BIODEGRADABLE COMPOSITION AND METHODS FOR MANUFACTURE

Field of Invention

The present invention relates to biodegradable compositions and methods of manufacture and uses thereof. The present invention also relates to additives for use in enhancing the biodegradation of compositions. The present invention also relates to methods for adjusting the biodegradability of a composition.

Background to the Invention

Plastic waste accumulation is a recognised problem that has yet to be addressed satisfactorily.

A significant amount of such waste is derived from petrochemicals. While a certain degree of product longevity is often desired, this may be for a single use for as little as a matter of minutes, whereas it has been estimated that commonly used polymers such as polyethylene. polyethylene terephthalate (PET), and polystyrene may last for as long as 500 to 5,000 years.

Biodegradable polymers have gained popularity since the 1980s and have been used to replace some non-biodegradable materials. Some of the challenges that has yet to be satisfactorily addressed with such biodegradable polymers are that:

• They often require industrial composting systems to "biodegrade", and such extreme conditions are not accessible to consumers in all locations. This means that biodegradable polymers consumed in those locations are often only marginally better than conventional plastics; and/or

• They often only partially break down into micro-plastics that are not themselves biodegradable.

For these reasons poly-lactic acid (PLA) is not recognised as being biodegradable under some certifying regimes (the American and European standards) since it does not biodegrade outside of artificial composting conditions. Some so-called "home compostable plastics" have been developed that meet standards developed by certain countries, but their application is limited and the standards are not universally accepted.

Some biodegradable polymers are also biobased polymers meaning that they are made fully, or partly, from biomass such as plants, algae, bacteria, or other micro-organisms. Such biomass is typically considered to be a renewable resource.

It is an object of the invention to provide a biodegradable composition that does not require industrial composting conditions. Ideally the biodegradable composition could be used to form a range of products designed to desired specifications.

Alternatively, or in addition, it may be an object of the invention to provide the public with a useful choice.

Summary of the Invention

In a first aspect the invention provides a biodegradable composition including a polymer and a filler, such that the composition has a C:N ratio of from 15 to 200, such as from 30 to 200.

Typically the composition will have a C:N ratio of from 15 to 200, such as from 30 to 200 prior to exposure to composting conditions.

It has now been realised that the rate of biodegradation of the compositions of the invention under non-industrial composting conditions can be materially increased by providing the composition with a filler material that can be used to modulate the overall carbon to nitrogen ratio (C:N ratio) of the composition. For instance, the filler may provide a source of nitrogen to the composition that may otherwise be substantially deficient in nitrogen. Without wishing to be bound by theory, it is believed that by using a filler to modulate the C:N ratio into a specific range, the filler acts to nucleate biodegradation by providing a site of biodegradation that is favoured by microorganisms. When using a filler, it has also been shown that the C:N ratio generally increases over time upon exposure to home compositing conditions. This suggests that microorganism growth is consuming nitrogen in situ over time.

In a second aspect the invention provides a biodegradable composition including a polymer and a filler, such that the composition has an extractable phosphorous concentration of at least 5 mg/kg. Typically the composition will have an extractable phosphorous concentration of at least 5 mg/kg prior to exposure to composting conditions.

It has now been realised that the rate of biodegradation of the compositions of the invention under non-industrial composting conditions can be materially increased by providing the composition with a filler material that can be used to modulate the extractable phosphorous concentration of the composition. For instance, the filler may provide a source of phosphorous to the composition that may otherwise be substantially deficient in phosphorous. Without wishing to be bound by theory, it is believed that by using a filler to increase the extractable phosphorous concentration of the composition, the filler acts to nucleate biodegradation by providing a site of biodegradation that is favoured by microorganisms. When using a filler, the extractable phosphorous concentration of the composition may increase over time upon exposure to home compositing conditions. This suggests that microorganism growth may facilitate the release of phosphorous in situ over time and/or that microorganism growth may facilitate breakdown of the composition within the soil environment.

In a third aspect the invention provides a biodegradable composition including a polymer and a filler, such that the composition has an extractable potassium concentration of at least 10 mg/kg.

It has now been realised that the rate of biodegradation of the compositions of the invention under non-industrial composting conditions can be materially increased by providing the composition with a filler material that can be used to modulate the extractable potassium concentration of the composition. For instance, the filler may provide a source of potassium to the composition that may otherwise be substantially deficient in potassium. Without wishing to be bound by theory, it is believed that by using a filler to increase the extractable potassium concentration of the composition, the filler acts to nucleate biodegradation by providing a site of biodegradation that is favoured by microorganisms. When using a filler, the extractable potassium concentration of the composition may increase over time upon exposure to home compositing conditions. This suggests that microorganism growth may facilitate the release of phosphorous in situ over time and/or that microorganism growth may facilitate breakdown of the composition within the soil environment.

In a fourth aspect the invention provides a biodegradable composition including a polymer and a filler, such that the composition has:

• a C:N ratio of from 15 to 200, such as from 30 to 200; and

• an extractable phosphorous concentration of at least 5 mg/kg; and/or

• an extractable potassium concentration of at least 10 mg/kg.

In a fifth aspect the invention provides a biodegradable composition including a polymer and a filler, such that the composition has:

• a C:N ratio of from 15 to 200, such as from 30 to 200; and

• an extractable phosphorous concentration of at least 5 mg/kg; and

• an extractable potassium concentration of at least 10 mg/kg.

In a sixth aspect the invention provides a biodegradable composition including a polymer and a filler, such that the composition has:

• an extractable calcium concentration of at least 15 mg/kg; and/or

• an extractable magnesium concentration of at least 1 mg/kg; and/or

• an extractable sodium concentration of at least 15 mg/kg; and/or

• an extractable manganese concentration of at least 0.05 mg/kg; and/or

• an extractable iron concentration of at least 0.05 mg/kg; and/or

• an extractable aluminium concentration of at least 0.05 mg/kg; and/or

• an extractable zinc concentration of at least 0.05 mg/kg; and/or

• an extractable copper concentration of at least 0.1 mg/kg; and/or

• an extractable boron concentration of at least 0.1 mg/kg. It has now been realised that the rate of biodegradation of the compositions of the invention under non-industrial composting conditions can be materially increased by providing the composition with a filler material that can be used to modulate the concentration(s) of extractable micronutrients of the composition. For instance, the filler may provide a source of the micronutrient(s) listed above to the composition that may otherwise be substantially deficient in the micronutrient(s). Without wishing to be bound by theory, it is believed that by using a filler to increase the extractable micronutrient(s) concentration of the composition, the filler acts to nucleate biodegradation by providing a site of biodegradation that is favoured by microorganisms. When using a filler, the extractable micronutrient(s) concentration of the composition may increase over time upon exposure to home compositing conditions. This suggests that microorganism growth may facilitate the release of micronutrient(s) in situ over time and/or that microorganism growth may facilitate breakdown of the composition within the soil environment.

In a seventh aspect the invention provides a biodegradable composition including a polymer and a filler, such that the composition has:

• a C:N ratio of from 15 to 200, such as from 30 to 200; and an extractable phosphorous concentration of at least 5 mg/kg; and/or an extractable potassium concentration of at least 10 mg/kg; and/or an extractable calcium concentration of at least 15 mg/kg; and/or an extractable magnesium concentration of at least 1 mg/kg; and/or an extractable sodium concentration of at least 15 mg/kg; and/or an extractable manganese concentration of at least 0.05 mg/kg; and/or an extractable iron concentration of at least 0.05 mg/kg; and/or an extractable aluminium concentration of at least 0.05 mg/kg; and/or an extractable zinc concentration of at least 0.05 mg/kg; and/or an extractable copper concentration of at least 0.1 mg/kg; and/or an extractable boron concentration of at least 0.1 mg/kg.

The present invention also provides a filler that may be used to modulate the properties of a polymer to enhance biodegradation. In an eighth aspect the invention provides a filler for incorporation in a biodegradable composition, the filler providing a source of at least one of: nitrogen; phosphorous; potassium; calcium; magnesium; sodium; manganese; iron; aluminium; zinc; copper; and boron, so that the biodegradable composition incorporating the filler has:

• a C:N ratio of from 15 to 200, such as from 30 to 200; and/or

• an extractable phosphorous concentration of at least 5 mg/kg; and/or

• an extractable potassium concentration of at least 10 mg/kg; and/or an extractable calcium concentration of at least 15 mg/kg; and/or

• an extractable magnesium concentration of at least 1 mg/kg; and/or

• an extractable sodium concentration of at least 15 mg/kg; and/or

• an extractable manganese concentration of at least 0.05 mg/kg; and/or an extractable iron concentration of at least 0.05 mg/kg; and/or

• an extractable aluminium concentration of at least 0.05 mg/kg; and/or

• an extractable zinc concentration of at least 0.05 mg/kg; and/or

• an extractable copper concentration of at least 0.1 mg/kg; and/or

• an extractable boron concentration of at least 0.1 mg/kg.

In a ninth aspect the invention provides a method of increasing the rate of biodegradation of a composition including mixing (such as blending) a filler and a polymer so that the composition has:

• a C:N ratio of from 15 to 200, such as from 30 to 200; and/or

• an extractable phosphorous concentration of at least 5 mg/kg; and/or

• an extractable potassium concentration of at least 10 mg/kg; and/or

• an extractable calcium concentration of at least 15 mg/kg; and/or

• an extractable magnesium concentration of at least 1 mg/kg; and/or

• an extractable sodium concentration of at least 15 mg/kg; and/or

• an extractable manganese concentration of at least 0.05 mg/kg; and/or

• an extractable iron concentration of at least 0.05 mg/kg; and/or

• an extractable aluminium concentration of at least 0.05 mg/kg; and/or

• an extractable zinc concentration of at least 0.05 mg/kg; and/or an extractable copper concentration of at least 0.1 mg/kg; and/or an extractable boron concentration of at least 0.1 mg/kg.

It will be understood that the C:N ratio of the polymer; and/or the concentration(s) in the polymer of the various elements outlined in the ninth aspect may be known before the filler is mixed (such as blended) into the composition. In such cases, the skilled person will be wellplaced to select a filler having the desired chemical composition to achieve the stated values.

Otherwise, where the C:N ratio of the polymer; and/or the concentration(s) in the polymer of the various elements outlined in the ninth aspect are not known before the filler is mixed (such as blended) into the composition, standard methodology (detailed further below) may be used to calculate those values. From that point, the skilled person will be well-placed to select a filler having the desired chemical composition to achieve the stated values.

In some embodiments the step of mixing (such as blending) the filler and the polymer will include the step of thermoforming or injection moulding.

Brief Description of the Drawings

One or more embodiments of the invention will be described below by way of example only, and without intending to be limiting, with reference to the following drawings, in which:

Figure 1 is a front view of a plant container in accordance with one embodiment of the present invention.

Figure 2 is a bottom view of a plant container in accordance with one embodiment of the present invention.

Figure 3 is a cross-sectional view of a plant container in accordance with one embodiment of the present invention.

Figure 4 is an exploded view of section "B" as shown in Figure 1. Figure 5 is a front view of one unit of a tray of individual plant containers in accordance with one embodiment of the present invention.

Figure 6 is an exploded view of section "B" as shown in Figure 5.

Figure 7 is a photograph of a plant container "A" used in the above ground degradation trial at day 60.

Figure 8 is a photograph of a plant container "A" used in the above ground degradation trial at day 60.

Figure 9 is a photograph of a plant container "B" used in the above ground degradation trial at day 60.

Figure 10 is a photograph of a plant container "A" used in the underground degradation trial after approximately 7 weeks.

Figure 11 is a photograph of a plant container "A" used in the underground degradation trial after approximately 7 weeks.

Figure 12 is a photograph of a plant container "B" used in the underground degradation trial after approximately 7 weeks.

Figure 13 is a photograph of a plant container "B" used in the underground degradation trial after approximately 7 weeks.

Figure 14 is a Scanning Electron Microscope (SEM) image of Sample ID#1, thermoforming

PBS/PLA composite with no filler, showing a smooth surface and uniform interior. Figure 15 is a Scanning Electron Microscope (SEM) image of Sample ID#2, thermoforming

Starch composite. Starch granules are readily visible on the surface and in the interior.

Figure 16 is a Scanning Electron Microscope (SEM) image of Sample ID#3, thermoforming

Blood & bone composite. Larger granules of varying size are seen within the voids inside the matrix.

Figure 17 is a Scanning Electron Microscope (SEM) image of Sample ID#7, thermoforming

Fish meal composite. Larger granules of varying size are seen within the voids inside the matrix.

Figure 18 is a Scanning Electron Microscope (SEM) image of Sample ID#12, thermoforming

Blood & bone composite showing cracking after 4 months of soil exposure.

Figure 19 is a Scanning Electron Microscope (SEM) image of Sample ID#13, thermoforming

Blood & bone composite, showing cracking after 6 months of soil exposure.

Figure 20 is a Scanning Electron Microscope (SEM) image of Sample ID#21, injection moulding Blood & bone composite, showing a uniform surface after 6 months of soil exposure.

Figure 21 is a Scanning Electron Microscope (SEM) image of Sample ID#22, injection moulding Starch composite showing pinholes after 6 months soil exposure.

Figure 22 is a Scanning Electron Microscope (SEM) image of Sample ID#23 injection moulded Fish meal composite, showing cracking after 6 months of soil exposure.

Figure 23-36 are photographs of samples of various compositions showing degrees of biodegradation under at home, soil conditions. Detailed Description of the Invention

As used herein the term "biodegradable composition" refers to a composition which is biodegradable under at least non-industrial composting conditions, but may additionally be biodegradable under industrial composting conditions.

As described herein, many so-called "biodegradable polymers" are only biodegradable under very specific conditions that are not ubiquitous. Many geographical centres do not have access to industrial composting conditions which means that such "biodegradable polymers" essentially never biodegrade within a reasonable time period, thus contributing to landfill waste. Even where the geographical centre does have such industrial composting facilities, consumer preference (often laziness) or lack of ubiquitous collection points means that such biodegradable polymers end up in the landfill, again never biodegrading within a reasonable time period. In some cases, industrial composting facilities may be prohibited from recycling bio-based polymers (such as PLA) due to restrictive local regulations/by-laws, which may (for example) stipulate that the facility can only accept green matter.

Hence there is a need to provide biodegradable compositions that are capable of biodegrading under non-industrial conditions such as home composting, in the soil or even as part of a landfill. This need is met, or at least met to some degree, such as a significant degree, by the biodegradable compositions of the present invention.

As used herein, the expression "industrial" in relation to composting conditions refers to those conditions that typically involve temperatures between 50 °C and 60 °C. Typically industrial composting conditions will be aerobic, rather than anaerobic. Typically industrial composting conditions involve two distinct phases: (i) active composting; followed by (ii) curing. The active composting phase may consist of a minimum period of 21 days where temperatures can reach

50°C to 60°C, whereas in the curing phase the rate of decomposition declines and the temperature decreases to < 40°C. Process parameters such as material structure (size of particles), mixing, relative humidity, temperature, pH, and the carbon/nitrogen ratio can be controlled during the phases. Such industrial composting conditions are detailed in Standards (incorporated herein by reference) as follows:

Europe - EN13432 - 'Requirements for packaging recoverable through composting and biodegradation'. The test requires the compostable plastics to disintegrate after 12 weeks ( at least 90% of the product should be able to pass through a 2 x 2 mm mesh and completely biodegrade after six months (at least 90% of the organic material is converted into CO ₂ ). The test is performed at 58 °C.

• USA - ASTM D6400 - 'Standard specification for labelling of plastics designed to be aerobically composted in municipal or industrial facilities.' The test covers plastics and products made from plastics that are designed to be composted in municipal and industrial aerobic facilities. The test is performed at 58°C.

• Australia - AS4736 - Biodegradable plastics suitable for composting and other microbial treatment.

As used herein, the expression "non-industrial" in relation to composting conditions refers to essentially all conditions that are not captured by industrial composting conditions as described herein. Typically such conditions would be considered "milder" and are characterised as operating at a substantially lower temperature than 50-60 °C. Typically such conditions will not include the conditions under which the biodegradable composition is kept for the duration of its functional life. For example, where the biodegradable composition is to be used to form a container, preferably the biodegradable composition will not substantially biodegrade while it is being used as a container. Generally the non-industrial composting conditions will refer to the conditions to which the biodegradable composition is exposed after the end of its functional life, typically through the conscious decision of the user to compost the product - namely the decision to place the biodegradable composition into a waste stream. Such a step will generally involve placing the biodegradable composition in contact with other waste products, although it is conceivable that the biodegradable composition is left alone. In one embodiment the non-industrial composting conditions may include being buried in the ground, although such conditions will preferably be aerobic. Specific examples of non-industrial composting conditions are those that relate to:

• "home composting conditions" - such conditions involve biodegradation at ambient temperature or slightly above ambient temperatures, and are generally under aerobic conditions. Such conditions are typically used for the treatment of organic waste, especially garden waste. Such biodegradation typically occurs under uncontrolled conditions unlike industrial composting. Standards have been developed to test biodegradation under home composting conditions and include (each of which is incorporated herein by reference): o International - ISO 14855-1 (2012) - the test is performed at 25 °C under aerobic conditions. This test methodology is used in the examples used to support the present invention; o Australia - AS5810- biodegradable plastics suitable for home compositing. The test is performed at 25 °C +/- 5 °C; o France - NF T 51800; o Austria - prEN 17427-TUV

• "soil biodegradability conditions" - a standard (which is incorporated herein by reference) has been developed to test biodegradation specifically in soil: o Europe — EN 17033 - Biodegradable mulch films for use in agriculture and horticulture; and

• "landfill" biodegradation conditions - a standard (which is incorporated herein by reference) has been developed to test biodegradation specifically in landfill: o ASTM D5526 - Standard Test Method for Determining Anaerobic Biodegradation of Plastic Materials Under Accelerated Landfill Conditions. The test is performed at about 35 °C.

The biodegradable compositions of the present invention are typically capable of biodegradation under at least one of the standards developed for non-industrial composting either listed here or elsewhere defined. Preferably the biodegradable compositions of the present invention are capable of biodegradation under at least ISO 14855-1 (2012). It will be appreciated that although poly(butylene succinate) (PBS) is biodegradable under non-industrial composting conditions, polylactic acid (PLA) is not and so neither is the combination of the two — namely compositions including PLA are not considered capable of meaningful biodegradation under at least one of the standards developed for non-industrial composting either listed here or elsewhere defined. In particular, it will be appreciated that PLA, of itself or in combination with PBS, is not considered capable of biodegradation under ISO 14855-1 (2012). It will be appreciated by the person skilled in the art that PLA degrades most efficiently at temperatures around 55 - 60°C.

Preferably the biodegradable composition of the invention is configured to undergo substantial biodegradation within 12 months of being exposed to non-industrial composting conditions.

Preferably, the biodegradable composition of the invention is configured to undergo substantial biodegradation within 6-12 months of being exposed to non-industrial composting conditions.

Preferably the biodegradable composition of the invention is configured to fully biodegrade within 24 months of being exposed to non-industrial composting conditions. More preferably, the biodegradable composition of the invention is configured to fully biodegrade within 18-24 months of being exposed to non-industrial composting conditions.

The biodegradable composition of the present invention has been shown, in preferred embodiments, to undergo at least 60% biodegradation within 60 days of being exposed to nonindustrial composting conditions. The biodegradable composition of the present invention has been shown, in preferred embodiments, to undergo about 80% biodegradation within 190 days of being exposed to non-industrial composting conditions. In those same studies, the positive control composition made of cellulose degraded about 82%, and so the preferred embodiments of the biodegradable composition of the invention were calculated to have a relative biodegradation of over 95%. In contrast, a combination of PBS and PLA without the filler has been shown to biodegrade only about 10% over a similar time frame.

Such rates of biodegradation make the biodegradable composition of the invention particularly well suited to those applications for which the functional life of the product is relatively short, such as take-away containers, food trays, beverage cups, etc. That said, without wishing to be bound by theory, it is believed that the rate of biodegradation may be modulated by increasing or decreasing the amount of filler and/or the chemical properties of the filler. Without wishing to be bound by theory, it is believed that the filler may act to nucleate biodegradation by providing a source of nutrition to the microorganisms that are responsible for the biodegradation. Scanning Electron Microscopy (SEM) indicates that for some fillers, there is a space/void between the filler and the polymer. That space/void may also act as a depot for microorganism growth and/or leaching of nutrients from the filler to the surrounding areas. As such, the more readily available the nutrition is (such as where it is provided in increased quantity, has a high surface area:volume ratio such as provided by small particulate size, located on an exterior surface, etc) then the rate of biodegradation is likely to be higher.

Conversely, where the nutrition is less readily available (such as where it is provided in decreased quantity, has a low surface area:volume ratio such as provided by large particulate size, located on the interior of the composition, etc) then the rate of biodegradation is likely to be lower. Advantageously, the filler of the present invention provides the user with the ability to configure the biodegradable composition to provide the desired rate of biodegradation.

In one application, the biodegradable composition of the invention is used to form a container suitable for growing a plant in. Typically, the growing phase of the plant above ground lasts up to approximately 12 months depending on the plant matter growing. In some forms, the biodegradable container formed from the biodegradable composition of the present invention may be configured to ensure that it does not degrade to a substantial degree before the container is likely to be ready to be planted. Such a container can be planted in situ at the site for which the plant is intended to continue to grow.

The filler included in the biodegradable composition of the invention may be used to impart mechanical stiffness to the biodegradable composition for a time and under certain conditions

(such as during the functional life of the biodegradable composition) whereby after it is exposed to the non-industrial composting conditions the mechanical stiffness is degraded, which may in turn promote accelerated biodegradation.

For example, a plant container made of the biodegradable composition of the present invention has been shown to maintain good mechanical stability and integrity during the growing phase of a plant in above ground degradation tests. It is believed that the use of the filler provides this advantage to the container. It is also envisaged that the use of a filler in the composition also provides nutrients to the soil upon degradation of the container in soil. It has also been surprisingly found that the filler greatly enhances the degradation of the composition.

As used herein the term "polymer", which forms part of the biodegradable composition, refers to any polymeric material that is capable of biodegradation under industrial or non-industrial composting conditions. Advantageously the incorporation of the filler of the invention into the biodegradable composition of the present invention increases the rate of biodegradation such that a polymer that may not, of itself, be considered to biodegrade satisfactorily under nonindustrial composting conditions is able to be formed into a biodegradable composition that is capable of biodegradation under non-industrial composting conditions. By way of non-limiting example, neat poly-lactic acid (PLA) may typically be considered to exhibit poor biodegradation under non-industrial composting conditions, however when combined with the filler of the invention the composition so formed exhibits a satisfactory rate of biodegradation under nonindustrial composting conditions.

Typical breakdown products of such polymers may include: naturally occurring gases (such as carbon dioxide and nitrogen); water; biomass (such as one or more components derived from a natural source that are used to form the polymer, such as polysaccharides); smaller subunits

(such as alcoholic acids) that are derived from microorganisms or made synthetically; and salts.

Generally such polymers will have a multitude of cleavable functional groups such as esters, amides, urethanes, and/or ethers. Such cleavable functional groups will typically be cleavable by hydrolysis and/or microbial action.

Examples of polymers that may be suitable for use in the present invention include agropolymers, and synthetic polymers. As used herein, "agro-polymers" refers to polymers that are either naturally occurring, or are derived from naturally occurring polymers. As used herein,

"synthetic polymers" may include polymers produced wholly synthetically, and may also include polymers produced at least in part by natural processes such as fermentation, such as microbial fermentation. For instance, poly-lactic acid (PLA) may be formed from the (synthetic) polymerisation of a monomer derived from fermentation of plant starch.

Examples of agro-polymers include: proteins (such as silk, wool, collagen); polysaccharides (such as starch, cellulose, chitin, chitosan, alginic acid, cellophane); polypeptides (such as gelatin, wheat gluten, casein, whey protein).

Examples of synthetic polymers include:

• Aliphatic polyesters such as: polyglycolide/ poly(glycolic acid) (PGA) polycaprolactone (PCL) polydioxanone (PDO) polylactic acid (PLA) (including poly(L-lactic acid), poly(D-lactic acid), and poly(DL-lactic acid)) poly(lactic-co-glycolic acid) (RIGA) poly(trimethylene carbonate) (PTMC) poly(aIkyl succinates), this family includes:

(i) poly(ethylene succinate) (RES)

(ii) poly(propylene succinate) (PPS)

(iii) poly(butylene succinate) (PBS)

(iv) poly(butylene succinate-co-butylene adipate) (PBSA) is a biodegradable, semi-crystalline polyester produced by co-condensation of succinic and adipate acid with 1-4-butanediol. polyhydroxyalkanoates (PHA), this family includes:

(i) polyhydroxybutyrate (PHB)

(ii) polyhydroxyvalerate (PHV)

(iii) polyhydroxyhexanoate (PHH)

(iv) polyhydroxyoctanoate (PHO)

(v) polyhydroxydecanoate (PHD)

(vi) polyhydroxy-5-phenylvalerate (PHPV)

(vii) poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) • Aromatic polyesters such as poly(butylene adipate-co-terephthalate) (PBAT);

• Polyamides such as BAK 1095 and BAK 2195 (based on caprolactam, butanediol, and adipic acid;

• Polyurethanes, that will typically include a biodegradable portion consisting of a polyester (such as PCI, PLA, and PGA), agro-polymer (such as chitin); and

• Vinyl alcohols such as polyvinylalcohol, and poly(vinyl acetate). Such polymers will typically be susceptible to oxidation and/or microbial degaradation.

In some embodiments where PHB is used, then a polymer selected from: PLA; PBAT; PHBV; PCL;

PBS, is also used. Typically where PHB is used it is used in a minor component to another polymer selected from; PLA; PBAT; PHBV; PCL; PBS. Preferably PHB is not used.

Preferably the polymer will be a synthetic polymer. Still more preferably the polymer will be a polyester. Preferably the polymer will be selected from polybutylene succinate (PBS), polylactic acid (PLA), a polyhydroxyalkanoates (PHA) (such as poly(3-hydroxybutyrate-co-3- hydroxyvalerate) (PHBV)), poly(butylene succinate-co-butylene adipate) (PBSA) and/or combinations thereof.

PBS is a thermoplastic polymer resin of the polyester family. PBS is a biodegradable aliphatic polyester with properties that are comparable to polypropylene. PBS is a relatively soft material and decomposes naturally into water and CO ₂ and is a suitable material for use in the biodegradable compositions of the present invention. However, the material is soft which may be problematic in the processing/handling and particularly during manufacturing when used alone.

PLA is a thermoplastic polyester and largely made from renewable resources. Contrary to other thermoplastics which are petroleum-based, some of the raw materials used for PLA's production include corn starch, tapioca roots, or sugarcane. PLA is bio-based and biodegradable but generally only under industrial composting conditions. Without industrial composting conditions it can take anywhere between 100 to 1000 years to decompose. As used herein, the "type" of polymer will refer to the chemical constitution of the polymer backbone - eg whether it is an agro-polymer, polyester, polyamide, etc.

That said, it will be understood that polymers may be characterised in a number of different ways, not just by the chemical constitution of the polymer backbone (such as whether it is a polyester or polyamide, for instance). For example, a polymeric material may be characterised by its degree of polydispersity (typically denoted as PD or PDI); its average molecular weight

(which may itself be provided as the number average molecular weight (M _n ); the weight average molecular weight (M _w ); the Z-average molecular weight (M _z )); degree of polymerisation (typically denoted as n); its degree of branching; its glass transition temperature

(Tg). At least some of these values may be obtained by using techniques such as gel permeation chromatography (GPC) and thermogravimetric analysis (TGA) and the use of such techniques will be within the skillset of the skilled person. Irrespective of the manner in which these values are obtained, the present invention contemplates polymers having all such values as being useful in the biodegradable compositions and methods of the present invention.

While the present invention contemplates the use of a single type of polymer in the biodegradable composition, preferably the biodegradable composition will include a plurality of types of polymers. For instance: the biodegradable composition may include two types of polymers; the biodegradable composition may include three types of polymers.

Advantageously a plurality of polymers may be included for a number of reasons, including to provide the biodegradable composition with desirable mechanical properties suitable for the intended use. The skilled person will appreciate that polymers individually have a wide range of mechanical properties, and that when combined such as in a composite material (such as a bilayer, or multilayer, or structural variants in which the plurality of polymers might be maintained separate locally), or in a mixture (such as a blend), that the mechanical properties of the combination may change, including that they may change dramatically. The present invention contemplates such combinations. Without wishing to be bound by theory, it is believed that the combination of a blend of polymers (such as PLA and PBS) with a filler provides the advantage of the composition having improved mechanical properties such as stiffness and strength. In general, it is believed that

PLA alone is a brittle substance. The inclusion of a filler such as the types described herein in a polymer blend of PLA and PBS has surprisingly produced a composition having improved mechanical strength and stiffness. Fillers of the types described herein may contribute stiffness to a product made from the biodegradable composition, but may slightly reduce strength (e.g. tensile strength, impact strength). The use of PBS is considered to add strength. In addition, combined with the improved biodegradation properties, it should be appreciated that the biodegradable composition of the present invention makes it well suited for a variety of different applications. The properties of the biodegradable composition may be modified as desired, by modifying the components, and the ratios of those components. For example, the amount of PLA in the composition can be increased as desired to produce more stiffness in the final composition. Increasing the stiffness of the composition would lead to a more rigid

(although possibly more brittle) product and lead to further control of the degradation time for the biodegradable composition. Additionally, the amount of filler may be varied to adjust the desired modulus of the biodegradable composition for processing. It may also be used to control the amount of nutrient(s) provided to the soil upon degradation of the biodegradable composition.

Where present, the plurality of polymers may be present in any ratio. Where two types of polymers are used, the polymers may be present at a ratio ranging from: 1:1000 to 1000:1; such as a ratio ranging from 1:100 to 100:1; such as a ratio ranging from 1:10 to 10:1; such as a ratio ranging from 1:5 to 5:1; such as a ratio ranging from 1:3 to 3:1; such as a ratio ranging from 1:2 to 2:1. Where two types of polymers are used, the polymers may be present at a ratio of about 2:1.

Preferably the biodegradable composition will include a plurality of types of polymers (such as two types of polymers) selected from: polybutylene succinate (PBS), polylactic acid (PLA), a polyhydroxyalkanoates (PHA) (such as polyhydroxyalkanoates (PHB), poly(3-hydroxybutyrate- co-3-hydroxyvalerate) (PHBV)) and/or combinations thereof. Most preferably the biodegradable composition will include polybutylene succinate (PBS) and polylactic acid (PLA).

When the biodegradable composition includes polybutylene succinate (PBS) and polylactic acid (PLA) the polymers may be present at a ratio (PBS:PLA) ranging from: 1:1000 to 1000:1; such as a ratio ranging from 1:100 to 100:1; such as a ratio ranging from 1:10 to 10:1; such as a ratio ranging from 1:5 to 5:1; such as a ratio ranging from 1:3 to 3:1; such as a ratio ranging from 1:2 to 3:1, such as a ratio ranging from 2.5:1 to 1.5:1, such as a ratio of about 2:1.

Examples of polymers that may be used in the biodegradable compositions of the present invention with a filler, such that the composition has a C:N ratio of from 30 to 200, include:

PLA;

• PBAT/PLA;

• PHBV/PLA

• PCL/PLA;

PBS/PLA.

For the or each type of polymer used in the biodegradable composition, a single grade of polymer may be used. As used herein, the term "grade" in relation to a polymer will typically refer to a polymer that is commercially available and sold as having a defined set of characteristics such as average molecular weight, polydispersity, etc. For example, PLA having an average molecular weight of 100 kDa may be used. However, that PLA grade may be blended with another PLA grade that might have a higher or lower average molecular weight, so that the polymer blend so formed may have characteristics different to either or both of the grades of PLA from which it is formed (such mixtures may have bi- or polymodal molecular weight distributions). All such combinations of grades and/or types are contemplated by the present invention.

The amount of polymer in the biodegradable composition of the present invention should not be seen as limiting. The concentration of polymer may be chosen so as to achieve the desired C:N ratio of the biodegradable composition; and/or the concentration(s) in the polymer of the various elements so desired and referred to herein. As such the concentration of the polymer should not be seen as limiting. It may be convenient to provide the concentration of the polymer as a weight for weight basis, as a percentage (% w/w) of the total of the biodegradable composition. In some embodiments the polymer (which includes a plurality of polymers) may be present at up to 99.99% w/w, such as up to 99% w/w, such as up to 98% w/w, such as up to 97% w/w, such as up to 96% w/w, such as up to 95% w/w, such as up to 94% w/w, such as up to 93% w/w, such as up to 92% w/w, such as up to 91% w/w, such as up to 90% w/w, such as up to 89% w/w, such as up to 88% w/w, such as up to 87% w/w, such as up to 86% w/w, such as up to 85% w/w, such as up to 80% w/w, such as up to 75% w/w, such as up to 70% w/w, such as up to 65% w/w, such as up to 60% w/w, such as up to 55% w/w, such as up to 50% w/w. In some embodiments the polymer is present at a concentration of at least 10% w/w, such as at least 15% w/w, such as at least 20% w/w, such as at least 25% w/w, such as at least 30% w/w, such as at least 35% w/w, such as at least 40% w/w, such as at least 45% w/w, such as at least 50% w/w, such as at least

55% w/w, such as at least 60% w/w, such as at least 65% w/w, such as at least 70% w/w, such as at least 75% w/w, such as at least 80% w/w, such as at least 85% w/w, such as at least 87% w/w, such as at least 89% w/w, such as at least 90% w/w. In some embodiments the polymer is present at a concentration of about 90% w/w, such as at a concentration of 90% w/w.

Preferably the biodegradable composition includes PBS. Where present, PBS may be included in an amount from 20 to 99.99% w/w of the composition, such as from 20 to 95% w/w, such as from 20 to 80% w/w, such as from 20 to 75% w/w of the composition, such as from 30 to 75% w/w, such as from 40 to 75% w/w, such as from 45 to 65% w/w of the composition, such as about 60 % w/w, such as 60% w/w.

Preferably the biodegradable composition includes PLA. Where present, PLA may be included in an amount from 10 to 99.99% w/w of the composition, such as from 10 to 95% w/w, such as from 10 to 80% w/w, such as from 15 to 60% w/w of the composition, such as from 15 to 50% w/w, such as from 25 to 45% w/w, such as about 30% w/w, such as 30% w/w. The biodegradable composition of the invention may be used in a variety of products. The biodegradable composition of the present invention may be used in the production of: pots

(including, plantable pots and transfer pots); saucers; troughs; packaging; weed barrier sheets; tubing; plates (including platters, round plates, square plates); dishes; cutlery (including, spoons, forks, knives, chopsticks); cups (including portion cups, cups configured for hot liquids, cold liquids); cup sleeves; cup lids; straws; bottles; bottle sleeves; bowls (including round bowls, square bowls, soup bowls); trays (including market trays, propagation trays, transfer trays, catering trays, takeout trays, lunch trays); containers (including clamshells, food boxes, to-go bowls, and containers configured for cold food, hot food and/or ice-cream); crates (for storage or transport, such as milk or egg crates); bags (including shopping bags, pet waste bags, produce bags, trash/rubbish bags, sandwich bags, bin liners); plant stakes; stands; branch tags; landscape twine/ties; cable ties; wraps (including sandwich wraps, lunch wraps, and pot wraps); baskets (including basket assemblies); greenhouse films; and personal items such as eyewear

(sunglasses), side bags, handbags, yoga mats, beach mats, towels, wallets, backpacks, phone cases, belts, umbrellas, tooth brushes, decking, jandals, footwear, shoe soles.

As used herein, the "filler" of the invention is a particulate material that is capable of incorporation into the biodegradable composition. Typically the filler is added to the polymer of the invention and mixed (such as blended) with the polymer. Typically the filler and the polymer are mixed prior to the polymer being formed into the desired article, however this should not be seen as limiting and the filler may be applied to the polymer (such as its surface) after it has been formed into the desired article.

In the context of the present invention, the filler will generally be chosen so as to achieve the desired C:N ratio of the biodegradable composition; and/or the concentration(s) in the biodegradable composition of the various elements so desired and referred to herein. With that desired function in mind, the present invention is not limited to the use of any particular type or amount of filler. While the present invention contemplates the use of a single filler, in some embodiments a plurality of fillers will be used. Said plurality of fillers may be pre-mixed prior to mixing with the polymer, or may be added separately. Typically, where a plurality of filler is used, the fillers will be pre-mixed prior to mixing with the polymer. Advantageously, the use of a plurality of fillers enables the user to achieve the desired C:N ratio of the biodegradable composition; and/or the concentration(s) in the biodegradable composition of the various elements so desired and referred to herein. Without wishing to be bound by theory the filler is adapted to enhance the non-industrial biodegradation of the biodegradable composition.

As used herein the "C:N ratio" refers to the ratio of carbon to nitrogen within the object being referred to, such as the biodegradable composition or the polymer or the filler. Typically it will refer to the carbon to nitrogen ratio of the biodegradable composition. There are a range of elemental analytical techniques available to the skilled person to determine carbon and nitrogen contents. Total nitrogen can be considered to consist of organic nitrogen, ammonium nitrogen, nitrate and nitrite. In known solid materials, it can be assumed in some cases that nitrate and nitrite nitrogen are negligible. Total Kjehldahl nitrogen (TKN) measures organic nitrogen, and ammonium nitrogen. The Dumas method (furnace) measures total nitrogen after converting organic nitrogen, ammonium nitrogen, nitrate and nitrite into gas. There are other ways to measure nitrogen, for example total nitrogen in water where total nitrogen that can be dissolved in water after digestion. One such technique is the persulfate oxidation technique for nitrogen in water which is performed under heated alkaline conditions, where all organic and inorganic forms of nitrogen are oxidized to nitrate. Extractable nitrogen may generally be measured as extractable ammonium.

Preferably the biodegradable composition of the invention will have a C:N ratio of from 15 to

200, such as from 30 to 200, such as from 15 to 150, such as from 30 to 150, such as from 15 to

100, such as from 30 to 100, such as from 50 to 100, such as from 60 to 85, such as from 75 to

85, such as about 79, such as 79. Typically the composition will have a C:N ratio of from 15 to

200, such as from 30 to 200 prior to exposure to composting conditions. In some cases, the C:N ratio of the material may increase after exposure to composting conditions.

In addition to the methods for determining total and extractable nitrogen, other extractable element values may be obtained using an extraction method such as Mehlich 3, which is well understood and is most commonly used to determine the availability of soil macronutrients (such as phosphorous, calcium, magnesium, and potassium) and soil micronutrients (such as copper, zinc, manganese, and iron).

As used herein "extractable phosphorous" refers to phosphorous determined using a method such as Mehlich 3. Preferably the biodegradable composition has an extractable phosphorous concentration of at least 5 mg/kg, such as at least 50 mg/kg, such as at least 75 mg/kg, such as at least 90 mg/kg. Typically the composition will have an extractable phosphorous concentration of at least 5 mg/kg prior to exposure to composting conditions. In some cases, the extractable phosphorous concentration of the material may increase after exposure to composting conditions.

As used herein "extractable potassium" refers to phosphorous determined using a method such as Mehlich 3. Preferably the biodegradable composition has an extractable phosphorous concentration of at least 10 mg/kg, such as at least 20 mg/kg, such as at least 25 mg/kg, such as at least 30 mg/kg, such as at least 40 mg/kg, such as at least 50 mg/kg. Typically the composition will have an extractable potassium concentration of at least 5 mg/kg prior to exposure to composting conditions. In some cases, the extractable potassium concentration of the material may increase after exposure to composting conditions.

Typically the or each filler used in the biodegradable composition of the invention will be substantially solid at room temperature, although in some embodiments the filler may include at least a part that is liquid at room temperature.

Generally the filler will itself be biodegradable. The filler may be derived from an animal (such as terrestrial, aerial, aquatic), fungi, plant (such as terrestrial, aquatic), or inorganic source, for example. Preferably the filler will be a processed material rather than a raw material.

Examples of fillers that may be used in the present invention include the following:

Animal derived - solid bone meal; blood meal; blood and bone; bee wax; insect meal; ground meal worms; fishmeal; crab meal; dried whey; earthworm casting; leather meal; animal waste (including human sewerage/night soil, animal manure (such as chicken manure, sheep manure/pellets)); gelatin; silkworm sand; collagen; horn meal; horn shavings; feather meal;

Animal derived - liquid fish oil;

Fungi derived mushroom powder; fungi powder;

Plant derived - solid cottonseed meal; ground seaweed; cork; seeds; peat; wood ash; wood flour; saw dust; wood fibers (eg from hardwood, softwood); fibers from grasses (including bamboo); flax; abaca; sisal; ramie; hemp; and bagasse; processed starch; cellulose; cellulose fibers; tea seed meal; cassava residue; distiller's grains; coffee grinds; rice hulls (rice husks); oat hulls; shells (including ground pecan shells, ground apricot seed, ground walnut shell, ground almond shell, coconut shell powder); maize meal; vinasse; sunflower seed husk; pea flour; soy protein; canola meal; soy bean meal; kiwifruit hair (which may be collected in the extractors/cyclones of kiwifruit packhouses); starch (although generally the use of starch will be less preferred);

Plant derived - liquid soybean oil; castor oil; vegetable oil; sunflower oil; coconut oil; avocado oil; olive oil;

Inorganic pond mud;

Inorganic - sodium rich sodium phosphate; sodium nitrate; sodium nitrite;

Inorganic - potassium rich potassium phosphate; potassium nitrate; potassium nitrite; potassium sulphate; potassium chloride; potassium magnesium sulfate;

Inorganic - calcium rich calcium phosphate, calcium nitrate, calcium nitrite, calcium ammonium nitrate;

Inorganic — ammonia/ammonium rich (nitrogen rich) and/or phosphorous/phosphate rich ammonium phosphate (diammonium phosphate, monoammonium phosphate); ammonium nitrate; ammonium chloride; ammonium sulphate; ammonium sulphate nitrate; ammonium thiosulfate; Inorganic - magnesium rich and/or ammonia/ammonium rich (nitrogen rich) and/or phosphorous/phosphate rich magnesium phosphate; magnesium nitrate; struvite (magnesium ammonium phosphate); wastewater mineral precipitates;

Organic - nitrogen rich and/or phosphorous/phosphate rich urea; urea-ammonium nitrate, uric acid.

Without limitation, the filler may, advantageously, provide a (secondary) function such as acting as a fertiliser, soil conditioner, soil enriching agent, weed suppressant, and/or a combination thereof.

Advantageously, the present invention allows the skilled person to select a filler, or combination of fillers, such as from the above list so as to achieve the desired C:N ratio of the biodegradable composition; and/or the concentration(s) in the biodegradable composition of the various elements so desired and referred to herein. In some cases the elemental composition of the polymer and/or the filler will be known from published information. In other cases, the elemental composition will not be known, but can be derived using standard techniques known in the art. For instance, total phosphorous and total potassium may each be measured by a digestion method that involves solubilising the whole sample before quantitative analyses of those elements. Total nitrogen can be determined using a furnace at extremely high temperatures, however a total Kjehldahl nitrogen (TKN) digest will generally provide more accurate results. Extractable nitrogen may generally be measured as extractable ammonium. Other extractable element values may be obtained using an extraction method such as Mehlich 3, which is well understood and is most commonly used to determine the availability of soil macronutrients (such as phosphorous, calcium, magnesium, and potassium) and soil micronutrients (such as copper, zinc, manganese, and iron).

In some embodiment, based on an awareness of the elemental composition of the polymer and filler, a mix ratio can be calculated so as to achieve the desired C:N ratio of the biodegradable composition; and/or the concentration(s) in the biodegradable composition of the various elements so desired and referred to herein. The filler will be typically be provided at a sufficient concentration so that the so as to achieve the desired C:N ratio of the biodegradable composition; and/or the concentration(s) in the polymer of the various elements so desired and referred to herein. As such the concentration of the filler should not be seen as limiting. It may be convenient to provide the concentration of the filler as a weight for weight basis, as a percentage (% w/w) of the total of the biodegradable composition. In some embodiments the filler may be present at up to 90% w/w, such as up to

80% w/w, such as up to 70% w/w, such as up to 60% w/w, such as up to 50% w/w, such as up to

40% w/w, such as up to 30% w/w, such as up to 25% w/w, such as up to 20% w/w, such as up to

15% w/w, such as up to 10% w/w, such as up to 5% w/w. In some embodiments the filler is present at a concentration of at least 0.01% w/w, such as at least 0.1% w/w, such as at least 1% w/w, such as at least 2% w/w, such as at least 3% w/w, such as at least 4% w/w, such as at least 5% w/w, such as at least 6% w/w, such as at least 7% w/w, such as at least 8% w/w, such as at least 9% w/w, such as at least 10% w/w. In some embodiments the filler is present at a concentration of about 10% w/w, such as at a concentration of 10% w/w.

The particle size of the filler should not be seen as limiting, although generally the filler will have an average particle size from 1 nm to 5 mm. In some embodiments the filler will have an average particle size from 100 nm to 1 mm. Generally the filler will have a largest particle size from 10 nm to 5 mm. In some embodiments the filler will have a largest particle size from 100 nm to 1 mm, such as from 1 μm to 500 μm. In some embodiments the largest particle size of the filler will be about 500 μm, such as 500 μm. In some cases the source of the filler will be of a desired particulate size, although in some cases post-processing will be required. Techniques for generating particulate matter of the desired particle size will be well understood to the skilled person, and include both particle size reducing techniques such as grinding/milling (and optionally sieving) and particle size increasing techniques such as wet and dry granulation (and optionally sieving).

In some embodiments the filler (such as blood and bone) can be graded by sieving through a sieve of the desired size, such as a sieve to select out those particles of greater than 1 mm, such as greater than 850 μm, such as an 850 μm sieve, so that the finer particles are utilised in the biodegradable compositions of the invention. In some embodiments the sieve may have even smaller apertures. It has been found that for some biodegradable compositions the finer particles of filler, such as from 1 μm to 500 μm, are better suited to forming techniques such as injection moulding.

The biodegradable composition of the invention may be formed using a wide range of techniques, including 3D printing. In such modes of forming, the biodegradable composition may be passed through a nozzle having, for example, an aperture of 0.75 mm or less. It will be appreciated that the filler particle size should typically be (substantially) less than the aperture dimension of the nozzle. For example, a filler size of about 250 microns may be used to reduce or remove the likelihood of filler particle(s) clogging the nozzle.

In some cases the source of the filler will undergo other post-processing steps such as being subject to: modulated temperature (such as being exposed to a temperature above ambient temperature for a period of time, such as to reduce moisture content); modulated pressure

(such as extrusion); and/or chemical modification (such as digestion, such as to facilitate more rapid breakdown).

In preferred embodiments, the biodegradable composition including a polymer and a filler comprises a mixture of PBS, PLA and a filler. In such embodiments, the components PBS, PLA, and the filler may be present in:

• the ratio of from about 40:50:10 to about 50:40:10, such as from 40:50:10 to 50:40:10, such as about 45:45:10, such as 45:45:10; or

• the ratio of from about 65:25:10 to 55:35:10, such as from 65:25:10 to 55:35:10, such as about 60:30:10, such as 60:30:10; or

• the ratio of from about 65:30:5 to about 60:35:5, such as from 65:30:5 to 60:35:5, such as about 62.5:32.5:5, such as 62.5:32.5:5; or

• the ratio of from about 60:25:15 to about 55:30:15, such as from 60:25:15 to 55:30:15, such as about 57.5:27.5:15, such as 57.5:27.5:15; or

• the ratio of from about 57.5:22.5:20 to about 52.5:27.5:20, such as from 57.5:22.5:20 to

52.5:27.5:20, such as about 55:25:20, such as 55:25:20. The ratio of PBS:PLA:filler of about 60:30:10 (such as 60:30:10) is especially preferred. That said, similar (or the same) ratios of the following polymer compositions are also preferred:

PBAT/PLA; PHBV/PLA; and PCL/PLA.

As used herein the term "about" in relation to a specific numerical value (or plurality of values) typically refers to a range of values such as plus or minus 15% of that specific numerical value (or each of the plurality of values), such as plus or minus 10% of that specific numerical value

(or each of the plurality of values), such as a range of plus or minus 5% of that specific numerical value (or each of the plurality of values), such as a range of plus or minus 3% of that specific numerical value (or each of the plurality of values), such as a range of plus or minus 2% of that specific numerical value (or each of the plurality of values), such as a range of plus or minus 1% of that specific numerical value (or each of the plurality of values). For example, the expression "about 60:30:10" may refer to a range of (54 to 66) : (27 to 33) : (9 to 11), where

"about" indicates a range of values such as plus or minus 10%.

In some embodiments the term "about" in relation to a specific numerical value (or plurality of values) refers to a range of values corresponding to those values rounded to the number of specified significant figures - for example, the expression "about 60:30:10" may refer to a range of (59.50 to 60.49) : (29.50 to 30.49) : (9.50 to 10.49).

As noted above, the biodegradable composition of the invention may be used in a variety of products. Techniques that may be used to blend the filler and the polymer and form it into the desired product include additive manufacture, extrusion, thermoforming, injection moulding, rotational moulding, injection blow moulding, vacuum casting, vacuum forming and/or compression moulding.

For instance, the biodegradable composition of the present invention may be extruded into a desired product such as a container defining a cavity. Alternatively, an additive layering manufacturing process could also be used to build the shape of a product, such as a container defining a cavity. It is also envisaged that a moulding process could be used such as a sacrificial moulding or injection moulding process or thermoforming.

In some embodiments, the biodegradable composition is processed through extrusion using a twin-screw extruder in order to reduce the production cost by process simplification, and to minimize the degradation of physical properties following the addition of the filler. The biodegradable compositions may be prepared using standard extrusion equiμment - Labtech

26mm scientific twin-screw, co-rotating extruder, LTE26-40.

A mixture of the polymer and filler may be extruded into sheets using co-rotating extruder

(LTE26-40, 40L/D ratio) set up with a slit die and a LabTech roller calendar. An exemplary die pressure is from 25 to 35 Bar. Sheets formed in such a manner may be collected as rolls from the extruder and then stored prior to thermoforming.

3D printed moulds of the desired product shape (such as plant trays) may be prepared for a thermoforming step. A sheet (such as an extruded sheet) may be thermoformed using standard vacuum former equiμment such as Steele FS44. In order to allow the vacuum to penetrate through the mould, a series of vent holes may be included (such as drilled) in the moulds. The sheets may first be heated until soft, and then placed over the moulds to form the products

(such as the plant trays).

The present invention also provides a method of selecting a filler to prepare a biodegradable composition including a polymer, the method including the steps of: i) selecting a polymer; ii) determining the C:N ratio of the polymer; iii) selecting a filler of known C:N ratio so that when combined with the polymer the

C:N ratio of the combined filler and polymer is from 30 to 200.

For instance, if the selected polymer contains carbon but zero nitrogen (100:0 C:N), and a filler is selected that contains 95:5 C:N, then mixing the two in equal quantities will create a mixture that has a C:N ratio of 195:5 which is equivalent to 39, which falls within the range 30 to 200. Using this method, bespoke fillers may be created, including through combination of two or more conventional fillers, such as those shown above.

It will be understood that a similar method may be used to select a filler to prepare a biodegradable composition having concentration(s) in the biodegradable composition of the various elements so desired and referred to herein (such as phosphorous, potassium, etc).

Additionally, it has been found by the inventors that the addition of a filler also provides improved manufacturability, namely during the extrusion/thermoforming process. It has been found the addition of a filler raises the Young's Modulus of the composition to a preferred level (about 1.298 GPa) to allow for improved processing. Initial testing suggested that a ratio of 60:30:10 (PBS :PLA:filler) provided a similar mechanical strength to HIPS (High Impact Polystyrene) and so could be used as a suitable biodegradable composition for replacing HIPS in products made of that polymer.

By way of non-limiting exemplification only, aspects of the invention will be described with reference to a plant container/tray being formed from the biodegradable composition

Container suitable for biodegradation when buried in soil under non-industrial composting conditions

The biodegradable composition may be formed into a plant container. It will be appreciated by the person skilled in the art that the shape and/or configuration of the plant container may be adapted to facilitate growth of the plant and/or enhance degradation of the container once planted in the soil. Figures 1-4 depict a plant container (100) that includes drain holes (20) on a base portion of the container to allow excess water to drain away. The drain holes are substantially circular in nature; however it will be appreciated that these holes should not be limited as such and any shaped holes can be used with the containers of the present invention. The container (100) may include a series of elongated slits (10) around the outer circumference of the container. The slits generally extend vertically from the base portion of the container and may vary in size in terms of length and width of the slits. The slits (10) are configured to enable the root system of the plant to penetrate through the walls of the container once the container is planted underground. Additionally, the slits provide segments in which to allow the container to break down once it has been planted to further speed up degradation.

It will be appreciated that the number, size and location of the slits may vary depending on the size of the container. However, it will be noted that the container will be configured to retain soil and the plant within the container.

An alternative plant container/tray is also shown in Figures 5-6. Aspects of the container are similar to those of the plant container described above, therefore like references refer to like components.

Examples

This present invention will now be described by reference to the following compositions prepared for use in a plant container. However, such examples should not be seen as limiting on the scope of the present invention.

BIODEGRADATION STUDY 1

Method of Manufacture

Thermoforming

Initial testing indicated that examples 1 and 2 had the necessary attributes so that they were able to be thermoformed, and became "pot A" and "pot B" referred under in-home degradation tests below.

Injection Moulding

Additional compositions with injection moulding grade material (examples 7B, 8B-8D and 9B described above) were also manufactured into individual pots by injection moulding. This was successful and two separate pots were produced and considered suitable for mass production.

The testing involved developing five injection moulding compositions (examples 7B, 8B-8D and

9B), having varying percentages of PBS and PLA using specific injection moulding grades and incorporated using two different fillers in the process, one with "fishmeal" and one with "blood and bone".

Of the five compositions prepared above, examples 7B and 8D were considered to be commercially viable of production by injection moulding. It should be appreciated by the person skilled in the art that different grades of starting materials may be used depending on the method of manufacture. For example, the grade of

PLA, PBS or filler may be altered according to the method of manufacture utilised.

Degradation trial

A plant container prepared in accordance with the present invention was produced and tested in this trial. A plant container was prepared using compositions disclosed in examples 1 and 2.

The purpose of the trial was to investigate the rate and type of breakdown of the plant container of the present invention under 'normal' in use conditions. Both above ground and below ground trials were conducted. The trials were conducted during New Zealand spring time conditions (from September to November).

It will be appreciated that commercial plant nurseries are generally very wet environments. It is believed that this additional moisture may have contributed to a faster degradation of the containers in this trial.

Trial 1 - commercial nursery

Two separate compositions were trialled in an above ground commercial nursery environment.

Figures 7-9 show degradation of the containers after approximately 60 days of use.

As can be seen in Figures 7-8, in the trials, containers prepared from composition Example 1 showed visual signs of degradation after 60 days. This suggests the composition may be useful for plants with shorter growth times above ground.

With reference to Figure 9, containers prepared from composition Example 2 showed minimal visual biodegradation after 60 days. This suggest that this composition may be suitable for plants having longer growth times above ground. An additional sample was sent to a testing facility around approximately the same time for further detailed testing of biodegradation. It was noted at the time that no signs of degradation were evident after 60 days, possibly because the conditions in the testing facility are more controlled than in a commercial nursery which may have a higher moisture level.

Trial 2 - in home/underground trial

An in-home, under ground trial was conducted. Tomato seedlings were planted in both containers prepared from composition Examples 1 and 2, and both containers were subsequently planted.

Figures 10-11 show the degradation of containers prepared from composition Example 1 after approximately 7 weeks underground.

Figures 12-13 show the degradation of containers prepared from composition Example 2 after approximately 7 weeks underground.

In the underground trials, upon visual inspection, both containers showed good degradation after just 42 days of planting underground.

From an initial observation of the plants, it was observed that plant growth was positive, and the plant matter appeared to be generally healthy. Growth characteristics of the plant planted underground with the container of the present invention was observed to be improved overall from that of previous plants.

Trial 3 — Biodegradation trial

As noted in trial 1, samples were sent to a laboratory testing facility (Scion, Titokorangi Drive,

Rotorua 3046, New Zealand) for detailed testing to determine biodegradation of the samples.

Three samples were tested in accordance with AS 5810 at 25 °C - a standard for testing at home composting conditions. The testing facility conducted aerobic biodegradation testing of sample materials in activated vermiculite under home composting conditions at 25 °C according to ISO standard 14855-1

(2012).

Two different compositions with different fillers were tested in combination with a control sample. The two compositions included a polymer blend of PBS and PLA with different fillers comprising starch (sample 1) and blood and bone (sample 2) respectively. The control sample consisted of a mixture of PBS and PLA. Testing of each sample was conducted in triplicate with averages calculated from each sample, the results are as shown in table A and B below.

The biodegradable composition of the invention (examples 2 and 4) passed the 10-day and 45- day validation requirement, as outlined in ISO 14855-1 (2012), indicating the microbial activity of the composting inoculum is satisfactory.

Table A. Interim biodegradation percentage after 58 days at 25 °C (average from three replicates).

Table B. Interim biodegradation percentage after 112 days at 25 °C (average from three replicates).

The tested materials can be considered biodegradable according to AS5810 (2010) when 90% has biodegraded within 365 days or when biodegradation has reached 90% of the maximum biodegradation for cellulose (positive control). The maximum percentage biodegradation of the positive control shall only be obtained after a plateau has been reached in the rate of biodegradation.

As shown in Table C, the PBS/PLA composite and PBS/PLA/Starch composite biodegraded very little during the 190-day test period. The PBS/PLA/Blood and Bone composite did biodegrade much more effectively than either the PBS/PLA or PBS/PLA/Starch composites. After 190 days, the test material has reached 97.5% of the biodegradability achieved by cellulose. Please note though that the positive control cellulose and the PBS/PLA/Blood and Bone composite have not yet reached a plateau value, so further degradation is expected to occur after 190 days.

Table C. Interim biodegradation percentage after 190 days at 25 °C (average from three replicates - treatments tested in triplicate but one replicate of the PBS/PLA composite broke at

Day 113).

As can be seen, the biodegradable compositions of the present invention (examples 2 and 4) showed vast improvement in biodegradation over that of the control, in particular the results demonstrate the level of biodegradation of the biodegradable compositions of the present invention (examples 2 and 4) was at least double the biodegradation of the control sample

(after 58 and 112 days), while the preferred biodegradable composition of the present invention that included blood and bone filler degraded 38 times faster than the control sample

(after 112 days) and significantly faster than the composition including starch. From the results shown after 112 days and 190 days, the level of biodegradation of the preferred biodegradable composition of the present invention that included blood and bone filler was substantially the same as the positive control (cellulose) which is remarkable given the inclusion of PLA which would not be expected to biodegrade substantially, even when co-formulated with PBS, as shown by the negative control.

BIODEGRADATION STUDY 2

A further series of 29 compositions were made and tested, some of which were exposed to soil for a period of 0, 2, 4, or 6 months to assess biodegradation under non-industrial composting conditions.

Broadly, the samples tested had the following variable parameters:

• Type of polymer grade: thermoforming (TF) or injection-moulding (IM)

PBS/ PLA/ filler ratios: 65:35:0 (no filler), 60:30:10, or 45:45:10

• Types of filler materials (all at 10% w/w): starch, blood & bone, fish meal, canola, soymeal, and feather meal

Buried in the soil for 0, 2, 4, or 6 months. For the different production processes, different grades of PBS and PLA were used. For the thermoforming application, the PBS grade was FD92, and the PLA grade was 2003D, while for injection moulding application, the PBS grade used was FZ71, and the PLA grade was 3052D.

Not every combination of the above treatments was investigated in this study. Due to the quantity of samples available for the soil treatment, some testing replicates were combined for tests requiring a lot of test sample. Table 1 shows the samples that were analysed and the specific analyses that were carried out. Where sample amounts allowed, tests were run in triplicate.

The samples were subjected to a selection of the following tests:

• Microscopy analyses,

• Fourier-transformed infrared spectral analyses (FTIR),

• Gel Permeation Chromatography (GPC),

Carbon (C), nitrogen (N) and C: N ratio.

• Total and extractable N, P and K, analysed by Total Kjehldahl Nitrogen (TKN), Total P,

Total K, 2 M KCI extractable NH ₄ , and Mehlich 3 (P, K, Ca, Mg, Na, Al, Fe, B, Cu, Mn, and Zn) analyses.

Table 1: Description of samples tested and the analyses performed on them. TF =

Thermoforming grade, IM - Injection moulding grade.

Microscopy

Microscopy (SEM) analyses were performed on a number of samples and the results are summarised in Table 2 and shown in Figures 14 to 22.

Table 2: Samples examined by SEM imaging

The composites containing starch grains, blood & bone and fish meal were distinctive from the unfilled composite materials. Starch granules could easily be seen both inside and on the composite pellet surface. Likewise, composite pellets containing blood & bone or fish meal contained larger particles of variable size compared to the uniform starch granules.

After 4 to 6 months of soil exposure, the samples showed evidence of degradation in the form of cracking or pin holing. The filler at the surface may be degrading or affecting the degradation of the polymer. Filler at the composite surface appeared to be covered with polymer so the amount of direct exposure to soil may have been minimal. All three of the fillers (blood & bone, fish meal and starch) showed poor contact with the polymer with a void space surrounding the fillers in the matrix.

Fourier-transform infrared spectroscopy (FTIR) Fourier transform infrared spectroscopy provides a signature of the key chemical components of the test compositions. This signature would therefore only change considerably when the molecular components change significantly.

Samples were analysed by Fourier transform infrared spectroscopy in attenuated total reflectance mode (FTIR-ATR) with 64 samples and background scans at 4 cm ^{- 1} resolution from 4000-400 cm ^{- 1} .

The majority of FTIR peaks were very similar between all spectra measured. This indicated that there were no major changes in the key chemical composition within the molecules of the test materials. Nevertheless, small differences were observed. Ester bonds are present in both PBS and PLA but they are located at different wavelengths. The 1755 cm ^{- 1} peak signified the carbonyl stretch of the PLA ester, while the 1711 cm ^{- 1} peak signified the carbonyl stretch of the

PBS ester.

Qualitative observation of these peak locations showed that in the thermoforming grade formulation 60:30 PBS/PLA with blood & bone filler, the 1755 cm ^{- 1} peak was lower after soil exposure (sample ID #11, #12, and #13) than before (sample ID#3) but also the 1711 cm ^{- 1} peak was lower after soil exposure than before. Therefore, ratios of 1755 cm ^{- 1} peak (PLA ester) and the 1711 cm ^{- 1} peak (PBS ester) were used for interpretation (Table 3).

The data in Table 3 has been derived from FTIR spectra obtained for the analysed samples.

For the thermoforming grade formulation 60:30 PBS/PLA with blood & bone filler, the PLA/PBS peak ratio increased over the first 4 months. A possible explanation for this is that the PBS degraded faster than PLA thus increasing the peak ratio. After 6 months the peak ratio decreased, potentially signalling that PLA started to degrade too.

For other composites, FTIR peak ratios were only measured at 0 and 6 months. The thermoforming 45:45 PBS/PLA with blood & bone filler (sample ID #20) did not increase the peak ratio compared to thermoforming composite with no filler and the composite with 60:30:10 PBS/PLA with blood & bone filler (sample ID #3). The injection-moulding formulations

45:45 PBS/PLA with blood & bone (sample ID #8, and #21), starch (sample ID #9, and #22), and fish meal (sample ID #10, and #23) as fillers, all increased their peak ratio over time thus potentially indicating degradation of the composites but there is not enough data to determine whether PBS or also PLA were degraded.

Quantitative analyses including peak picking of the 1711 cm ^{- 1} peak and 1755 cm ^{- 1} peak and additional FTIR analyses of the composites exposed for 2 and 4 month could give more detailed information about the degradability of those composites.

Gel Permeation Chromatography (GPC)

Gel Permeation Chromatography (GPC) is a type of size exclusion chromatography and provides molecular weight data of polymers by separating analytes according to size. All samples described in Table 1 were analysed for their respective molecular weight distribution after dissolving a known sample mass in chloroform. The fillers typically did not dissolve in chloroform as was evident from the precipitate that remained after the dissolving process.

The parameters measured with GPC analyses that are most informative for this study are the mass-weighted molecular weight (Mw) and the dispersity index. The Mw does not directly average the mass of individual polymers like the number-weighted molecular weight (Mn) does, but it takes account of the overall molecular weight of all the polymers in the sample. It is based on the fact that larger sized molecules contain more mass than smaller molecules and thus unduly contribute to the molecular weight average. Unlike the Mn average, the Mw average accounts for the molecular size of the polymers instead of just the number of polymers in the sample and thus gives a more informative representation of the sample's molecular weight.

The dispersity index is the ratio between Mw/Mn and for a totally uniform sample would have a value of 1. The largerthe dispersity index the greater the size range of the polymers in a sample.

The melt mass-flow rate (MFR) also known as melt index, describes the flow properties of plastics at a defined temperature. The Melt Flow Rate is a measure of the ease of flow of melted plastic. The MFR is related to a polymer's relative molecular weight. The theoretical MFR for the biopolymers used in this study are shown in Table 4. In theory, if the MFR is higher for a given polymer, the molecular weight (Mw) is lower and vice versa. Therefore, based on MFR index in Table 4, and the actual measurements, the thermoforming grade exhibits a higher

Mw than the injection moulding grade for the respective polymers.

Table 4: Theoretical melt flow index (MFR), mass-weighted molecular weight (Mw), and dispersity index for the raw polymers used in the composite materials in this study.

Effect of polymer grade on composite material molecular weights

To obtain an indication of the effect of polymer grade on molecular weight of the composite material, the blend ratios of the composite materials were used to calculate a theoretical Mw mass. These calculations were based on the assumption that no filler material would be dissolved in the chloroform. The Mw measured on the composites after processing but before soil incubation were averaged by polymer grade, to compare them with theoretical Mw before compounding (Table 4).

This showed that the compounding step did not impact the Mw of the injection moulding grade composite while the compounding process reduced the Mw of the composite materials by 27% to 37% for the thermoforming type materials (Table 5). However, since the Mw of thermoforming plastics before compounding were higher than for injection moulding plastics, after compounding the mean Mw for all fillers of each processing type were comparable (Table

5). Table 5: Theoretical mass-weighted molecular weight (Mw) and GPC measured Mw averaged for all fillers for the various process types and blend ratios in this study and the percentage reduction due to processing, NA = not measured.

Effect of filler type, blend ratio and soil incubation period

The Mw separated by process type grade, blend ratio and filler type showed that the before soil incubation composites with the various fillers all ranged between 101,115 g/mol for fish meal and 129,050 g/mol for blood & bone (Table 6). After 6 months of soil exposure, the Mw of the injection moulding type (45:45 blend ratio) starch composite decreased by 18%, the blood & bone composite by 21%, and the fish meal composite by 37%. In the same period of soil exposure, the Mw of the thermoforming type (60:30 blend ratio) blood & bone composite decreased by 55%.

The Mw did not decrease considerably with increased soil exposure time from 2 to 6 months for both injection moulding and thermoforming blood & bone composites while only small decreases were observed for the injection moulded fish meal and starch composites. This could indicate that the microbial activity and most of the degradation of the polymer chains is occurring within the first few months. After 6 months soil exposure, the thermoforming blood & bone type composite with a blend ratio of 60:30:10 showed Mw value of about half the Mw value of the similar composite with a blend ratio of 45:45:10. A possible explanation for the higher Mw for the 45:45:10 blend could be that the amount of PLA present in the composites was greater. A PLA polymer is known to biodegrade slower than PBS polymer. Therefore, a greater proportion of PLA in the composite is likely to slow down the biodegradation process.

Table 6: The mass-weighted molecular weight (Mw) and (standard deviation) of the different processing types, blend ratios, filler types and soil incubation period measured in this study, whereby "(-)" indicates "not measured". Sample size is 2 for all except for soil incubated thermoforming 60:30 Blood & bone composites. Their sample size is 6.

A lower dispersity index indicates a more uniform sample than when dispersity index values are higher. Before soil exposure, the dispersity index of the injection moulding type composites was higher than those composites designed for thermoforming applications. The thermoforming type starch composite, however, approached the dispersity values of the injection moulded suited composites. The thermoforming type composites with other fillers all showed lower dispersity indices ranging from 8.9 for blood & bone to 10.0 for fish meal (Table 7).

After 6 months of soil exposure, the lowest dispersity index was reached for the thermoforming blood & bone composite with a blend ratio of 60:30:10. All the 45:45:10 blend ratios showed greater dispersity indices ranging in order from low to high: injection moulding fish meal composite < injection moulding blood & bone composite < injection moulding starch < thermoforming blood and bone (Table 7). Table 7: The mean dispersity index and (standard deviation) of the different processing types, blend ratios, filler types and soil incubation period measured in this study, whereby "(-)" indicates "not measured". Sample size is 2 for all except for soil incubated thermoforming 60:30

Blood & bone composites. Their sample size is 6.

Carbon and nitrogen ratios The carbon content of the composites with the various filler types ranged from 52.3 to 57.6%

(Table 8) indicating that the filler type only had a small effect on the carbon content of the composites before soil incubation. The range in nitrogen contents varied more considerably than the carbon content. The N content ranged from almost none (0.05%) for the fillers known to not contain any nitrogen, to 1.53% N for feather meal (Table 9).

After soil exposure, both the carbon and nitrogen contents decreased. However, the carbon content was stable with increasing soil exposure time, while the nitrogen kept decreasing with soil exposure time for the injection moulding and thermoforming compositions including blood

& bone fillers. This was also reflected in the C to N ratio that kept increasing over time for both blood & bone composites. This is a promising result suggesting that the nitrogen provided (in this case by the blood and bone) was accessible to the microbial communities and has to some extent been metabolised by those microbial communities.

Table 8: The carbon content of the different processing types, blend ratios, filler types and soil incubation period measured in this study, whereby "(-)" indicates "not measured". Standard deviations are given for the soil incubated thermoforming 60:30 Blood & bone composites, which were analysed in triplicate.

Table 8: The carbon content of the different processing types, blend ratios, filler types and soil incubation period measured in this study, whereby "(-)" indicates "not measured". Standard deviations are given for the soil incubated thermoforming 60:30 Blood & bone composites, which were analysed in triplicate.

Table 10: The carbon to nitrogen ratio of the different processing types, blend ratios, filler types and soil incubation period measured in this study, whereby indicates "not measured".

Standard deviations are given for the soil incubated thermoforming 60:30 Blood & bone composites, which were analysed in triplicate.

Total and extractable nitrogen, phosphorus, and potassium concentrations Total P and K were analysed by a digestion method that is able to solubilise the whole sample before quantitative analyses of those nutrients (Table 11). Total N can be determined using a furnace at extremely high temperatures. These results were reported in the previous section

(Table 9) but it is more accurate to use total Kjehldahl nitrogen (TKN) digest for analyses.

Extractable nitrogen will be measured as extractable ammonium.

Additionally, extractable nutrients (Tables 12) were analysed because they show the availability of those nutrients once composites are exposed to the soil. As an extraction method Mehlich 3 was selected. This method uses the acids acetic acid and nitric acid. The Mehlich 3 extraction procedure is most commonly used to determine the availability of soil macronutrients

(phosphorous, calcium, magnesium and potassium) and soil micronutrients (copper, zinc, manganese and iron).

Before soil exposure, blood & bone and fish meal composites processed both by thermoforming and injection moulding end-application, contained considerably more phosphorus than the other fillers (Table 11), while thermoforming type feather meal contained the most nitrogen (Table 9). The most total and extractable K and B was found in soymeal, while blood & bone contained considerably more Ca and Fe than the composites with other fillers. The composite with canola contained the most extractable Mg, Mn, Zn and Cu.

For the composites with fish meal filler and blood & bone filler, after soil exposure the extractable P % and extractable K % increased, compared to the composites before soil exposure. The thermoforming grade blood & bone filler increased more in extractable P and K percentages than the injection moulding grade blood & bone filler. This showed that with increased soil exposure more P and K become available (Table 11). Additionally, all other extractable nutrients except extractable sodium for thermoforming blood & bone also increased after soil exposure (Table 12). This provides evidence of composite material breakdown within the soil environment.

Table 11: The total phosphorus (TP), extractable phosphorus (Extr. P), total potassium (TK), and extractable potassium (Extr. K) of the different processing types, blend ratios, filler types and soil incubation period measured in this study. Standard deviations are given for the soil incubated thermoforming grade 60:30 blood & bone composites, which were analysed in triplicate for TP and TK.

Table 12: The extractable calcium (Ca), magnesium (Mg), sodium (Na), manganese (Mn), iron

(Fe), aluminium (Al), zinc (Zn), copper (Cu) and boron (B) of the different processing types, blend ratios, filler types and soil incubation period measured in this study. Sample size for all samples was 1.

Summary

Chemical, spectral and image analyses were performed on 10 different polybutylene succinate (PBS)/ poly(lactic acid) (PLA) composites containing biomaterial fillers, manufactured with either thermoforming or injection-moulding grade polymers using the following PBS/PLA/filler ratios: 65:35:0 (no filler), 60:30:10, or 45:45:10. The filler materials were: starch, blood & bone, fish meal, canola, soymeal, and feather meal.

Small strips of selected treatments (starch, blood & bone and fish meal composites) were also buried in peaty soil for either 2, 4, or 6 months. After the soil exposure period, samples were removed from the soil and submitted to Scion for analyses. In total 29 PBS/PLA composites were analysed. All strips were produced through injection moulding, even with the thermoforming formulations. This was decided in order to obtain similar and homogenous samples to test.

Microscopy showed that the fillers (blood & bone, fish meal and starch) exhibited poor contact with the polymer with a void surrounding the fillers in the matrix. This could be assisting with the degradation process. After 4 - 6 months of soil exposure, the composites showed evidence of degradation in the form of cracking or pin holing.

Fourier transform infrared spectroscopy (FTIR), indicated that all composites had a similar chemical fingerprint as can be expected since they all largely consisted of PBS and PLA. Nevertheless, small differences were observed. The 1755 cm ^{- 1} peak signified the carbonyl stretch of the PLA ester, while the 1711 cm ^-1 peak signified the carbonyl stretch of the PBS ester.

Qualitative observation of these peak locations showed that in the thermoforming grade formulation 60:30 PBS/PLA with blood & bone filler, both the 1755 cm ^{- 1} peak and the 1711 cm" peak were lower after soil exposure than before. Analysing the ratios of 1755 cm ^{- 1} peak (PLA ester) and the 1711 cm ^{- 1} peak (PBS ester) indicated that the PLA/PBS peak ratio increased over the first 4 months followed by a decrease after 6 months. This potentially indicated that the

PBS degraded faster at the start but that PLA started to degrade in the last months. However, more timeseries measuring composites exposure in soil would need to be analysed before conclusions about PLA degradation can be determined with absolute certainty.

The gel permeation chromatography (GPC) analyses indicated that the polymer grade had an impact on the molecular weights. It showed that the compounding step did not impact the weighted molecular weight (Mw) of the injection moulding composite formulation while it reduced the Mw of the thermoforming composite materials by 27% to 37%. However, since the

Mw of thermoforming plastics before compounding were higher than for injection moulding plastics, after processing the mean Mw for all fillers of each processing type were comparable. After 6 months of soil exposure, the Mw of the injection moulding (45:45 blend ratio) starch composite decreased by 18%, the blood & bone composite by 21%, and the fish meal composite by 37%. In the same period of soil exposure, the Mw of the thermoforming (60:30 blend ratio) blood & bone composite decreased by 55%. The lower decrease in Mw for the

45:45:10 blends could be because the amount of PLA in the composites was greater, and not due to the preparation method. PLA is known to biodegrade slower at environmentally relevant conditions than PBS. Therefore, a greater proportion of PLA in the composite is likely to slow down the biodegradation process. Increasing soil exposure from 2 to 6 months did not show clear trends in molecular weight losses.

Filler types had a large impact on nitrogen concentrations but only a small effect on carbon concentrations of the composites. Feather meal composites contained the highest concentrations of nitrogen. Fish meal composites contained the second highest nitrogen concentration. The blood & bone and fish meal composites, produced both with thermoforming and injection moulding grade, contained considerably more phosphorus than the composites with other fillers.

After initial soil exposure, both the carbon and nitrogen contents of the composite material decreased. However, the carbon content was stable with increasing soil exposure time, while the nitrogen kept decreasing with soil exposure time for both the injection moulding and thermoforming blood & bone fillers. This was also reflected in the C to N ratio that kept increasing over time for both blood & bone composites. This is a promising result suggesting that the nitrogen provided by the blood and bone was accessible to the microbial communities and has to some extent been metabolised by those microbial communities.

Most extractable nutrients increased after soil exposure, indicating that more nutrients became available, signalling composite material breakdown within the soil environment. The composites with fish meal filler and blood & bone filler increased the percentage of extractable

P and extractable K while the starch composite did not.

The thermoforming composite (60:30 blend ratio) with blood & bone filler increased more in extractable P and K percentages than the injection moulding (45:45 blend ratio) blood & bone filler composite. This indicated the thermoforming (60:30 blend ratio) blood & bone filler composite was further degraded than the injection moulding (45:45 blend ratio) blood & bone filler composite.

Implications and conclusions

Overall, this study has shown degradation after soil exposure of the described composites, especially for the composites containing blood & bone and fish meal. Feather meal composites were not tested for soil exposure in this study but could have a good degradation potential because they contained the highest nitrogen content of all the filler types. Finally, the 60:30 blend ratio degraded further than the 45:45 blend ratio, likely due to the higher content of more readily degradable PBS than PLA. BIODEGRADATION STUDY 3

A series of compositions were made and tested, some of which were exposed to soil for a period of 0, 2, 4, or 6 months to assess biodegradation under non-industrial (home) composting conditions.

The samples shown in the Figures 23 to 36 are the samples that had been inserted into soil on the 25th of June 2021. The sequence of numbers on the samples reflect when the samples were recovered from the soil, the lowest numbers are at 2 months, the middle numbers at 4 months and the highest at 6 months, there being three samples each month.

Table D: Average weather conditions by month and cumulative are shown in the table below.

Biodegradable Composition A - Figure 23

Biodegradable Composition B - Figure 24

Biodegradable Composition C - Figure 25

Biodegradable Composition D - Figure 26 Biodegradable Composition E - Figure 27

Biodegradable Composition C - Figure 28

Biodegradable Composition D - Figure 29

Composition DI - Figure 30

Biodegradable Composition D2 - Figure 31

Biodegradable Composition E - Figure 32

PBS Only - Figure 33

PBS 60% PLA 40% - Figure 34

6 Month Samples of all Eight Formulations - Figure 35

6 Month Results of Miscellaneous Formulations - Figure 36

BIODEGRADATION STUDY 4

In the current study, we examined the following materials: • Composites made from PLA combined with different fillers (added at 10 wt.%). The fillers were Blood and Bone, Fish meal, Feather meal, Canola Meal. A control of 100%

PLA was also used (Milestone 2);

• A composite made from PBS/PLA/Blood and Bone (60/30/10 wt.%);

• Composites using other plastics including Polybutylene adipate terephthalate (PBAT),

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV) and Polycaprolactone (PCI):

PBAT/PLA/Blood and Bone, PHBV/PLA/Blood and Bone, PCL/PLA/Blood and Bone,

PBS/PLA/Feather meal (60/30/10 wt.%) (Milestone 3);

• Blend of PBS/PLA/Blood and Bone with different Blood and Bone ratios: (62.5/32.5/5 wt.%), (57.5/27.5/15 wt.%), (55/25/20 wt.%) (QT 10336).

The above formulations were extruded using injection moulding grade of PLA polymer Luminy

1130 and injection moulding grade of PBS polymer BioPBS FZ71.

Methods and experimental design

In total 13 different formulations were tested (as shown in the table immediately below). These formulations were then exposed to soil for either: 0, 3, 4, or 6 months; or 0, 3, and 6 months; or

0, 2, 4 and 6 months to determine whether some fillers or different composite type combinations are likely to encourage the degradation process under ambient environmental conditions.

The samples were subjected to a selection of the following tests:

• Visual and microscopy analyses,

Fourier-transformed infrared spectral analyses (FTIR) at Time 0 and 6 months,

• Gel Permeation Chromatography (GPC),

Mass, carbon (C), nitrogen (N) and C:N ratio,

• Total P, Total K, extractable NH4, (extraction with 2 M KCI) and extractable P, K, Ca, Mg,

Na, (Mehlich 3 extraction with acetic acid and nitric acid).

Description of samples tested, and their soil exposure periods.

Results

Macro visual appearance:

After 6 months of soil exposure, the PLA without filler looked the same as before soil exposure, indicating that soil exposure did not affect the test strips made from pure PLA. The PLA/Blood and Bone, PLA/Fish meal, PLA/Feather meal, and PLA/Canola meal composites appeared structurally sound but showed granular discolourations from 2 months of soil exposure onwards. This could indicate that the fillers near the surface were starting to degrade but that the PLA was more resilient. In addition, there were some large cracks visible in the PLA/Fish meal test strips. This would suggest that the composite material was becoming more brittle over time.

The test strips where PLA was mixed with PBAT, PCL or PBS (and fillers) looked more eroded after 6 months than those made from only PLA with fillers. From 2 months of exposure onwards, black and red areas are visible for the PBAT and PCL composites, and large lighter areas are visible for the PBS composites. The PHBV composites did not show such discolourations and looked fairly intact after 6 months of soil exposure.

Increasing the amount of Blood and Bone filler in the PBS/PLA test strips from 5% to 20% resulted in a more eroded appearance. Microscopy:

Samples were prepared for scanning electron microscopy (SEM) imaging and examined at low and moderate magnification to assess the general structure and to look for evidence of degradation in samples exposed to soil. The results are summarised in the table immediately below.

After 4 to 6 months of soil exposure, the samples showed evidence of deterioration in the form of cracking, cavities or pin holes. Overall, it was difficult to distinguish if it was just the filler at the surface that was degrading or also the polymer.

The surface of the PLA test strips without any filler was after 6 months of soil exposure, still as smooth as it had been before soil exposure. In contrast, the test strips with PLA and 10% Blood and Bone filler showed large surface cracks after 6 months of soil exposure. The PLA with

Canola meal filler showed large surface cracks and cavities indicating severe deterioration. The

PLA with Feather meal filler also showed cracks indicating some deterioration. The PLA with

Fish meal filler showed some cracks but less than the PLA with other fillers.

The PBAT/PLA with Blood and Bone filler composite showed microbes colonising the Blood and

Bone exposed at the surface after 3 months of soil exposure. Also after 6 months, there were distinct surface cracks and cavities but the overall surface was smooth with pinholes and cavities. The PHBV/PLA with Blood and Bone composite showed a rougher surface with cavities and cracks after 6 months of soil exposure. The PBS/PLA with Blood and Bone filler and the

PBS/PLA with Feathermeal composites showed weathered surfaces with cracks and cavities.

The most severely degraded surface was observed for the PCL/PLA with Blood and Bone filler.

Overall, the presence of fillers near the surface tended to accelerate pitting and cracking of the composite surface after soil exposure. In these cracks and holes microbes were visible.

Microbes might have also been present on the flat surfaces but have been washed/brushed off when samples were removed from the soil. The pure PLA with filler samples tended to show more straight-line cracks than the polymer/PLA composite samples, while the polymer/PLA composite samples showed more holes and rougher surfaces. The straight-line cracks in the pure PLA with filler samples are likely caused by mechanical force after the fillers near the surface had started to biodegrade.

Microbial biodegradation was unlikely to create straight-line cracks in the pure PLA with filler sample materials. The PHBV/PLA and PCL/PLA with Blood and Bone fillers were the most deteriorated composite samples.

After 6 months of soil exposure, a notable increase in surface deterioration was observed compared to the shorter exposure time.

Mass balance

The PLA with filler composite only showed minor variations in the mass of the test strips after soil exposure and in some cases increased in mass possibly due to a small amount of moisture being absorbed into the test strips during the soil exposure period. The PBS/PLA composite with 10% or more Blood and Bone filler and the PCL/PLA composite with Blood and Bone filler achieved more than 2% mass loss after either 4 or 6 months of soil exposure.

Total C, N, P, K and C:N ratio

Total nitrogen (N) was determined using a furnace at extremely high temperatures. Total phosphorus (P), and total potassium (K) were analysed by a digestion method that solubilises the whole sample before quantitative analyses of those nutrients - the results of which are presented in the table immediately below.

The carbon concentration of the various composites ranged from 48.2 to 55.9% and was somewhat influenced by the polymer type. The PCL/PLA composite contained the highest carbon concentration while the pure PLA polymer by itself showed the lowest carbon concentration. The highest nitrogen concentrations were found in the Feather meal and 20%

Blood and Bone fillers while the highest phosphorus concentrations were found in the Blood and Bone fillers and the highest potassium in the canola meal filler.

Before soil exposure, the N concentration ranged from almost none (500 pμm) for the pure PLA without filler, to 13,000 pμm N for the composite with PBS/PLA and 20% Blood and Bone depending on the particular composite manufactured.

After soil exposure, the PLA with various fillers decreased in nitrogen and potassium concentration over time. The polymer/PLA composites with fillers also decreased after 6 months of soil exposure.

Because, the C concentration was much more stable over time than the N concentrations, the C to N ratio increased over time for most samples. The increased C to N ratio indicated that the

Blood and Bone and other fillers were becoming a little more accessible to the microbial communities and that they had started to metabolise the fillers.

Overall, the carbon and phosphorus concentrations were not influenced by the soil exposure duration while the nitrogen and potassium concentrations decreased over time. This would suggest that the fillers did start to biodegrade a little after soil exposure. The change in carbon and phosphorus concentrations was likely too small to see any significant decrease. The concentrations of carbon are typically very large so only big changes are visible while microbes typically require a lot less phosphorus than nitrogen for normal growth.

Extractable nutrients

Extractable nutrients were analysed because any increase over time would show the availability of those nutrients once composites are exposed to the soil. Extractable nitrogen was measured as extractable ammonium nitrogen while extractable Phosphorus (P), Calcium (Ca), Magnesium

(Mg), Potassium (K) and Sodium (Na) were analysed using the Mehlich extraction. The Mehlich

3 extraction procedure is most commonly used to determine the availability of soil macronutrients (phosphorous, calcium, magnesium and potassium). This Mehlich extraction uses acetic acid and nitric acid for the extraction process.

The extractable ammonium, phosphorus, potassium, sodium, calcium and magnesium concentrations in the pure PLA samples were below the detection limit before soil exposure and after 6 months of soil exposure. This was expected since these pure PLA samples contained very low concentrations of total nitrogen, total phosphorus, and total potassium. Before soil exposure, the most extractable ammonium, phosphorus, potassium, sodium, calcium and magnesium was found in the PBS/PLA composite with 20% Blood and Bone filler, followed by the PBS/PLA composite with 15% Blood and Bone filler. The PBS/PLA composites with 5% and 10% Blood and Bone filler had much lower concentrations of extractable nutrients indicating that the extractable nutrient originated from fillers. For the 10% filler formulations, before soil exposure, the most extractable ammonium was found in the PCL/PLA/Blood and

Bone composite, while the most extractable phosphorus was found in the PLA/Blood and Bone composite, the most extractable sodium was found in the PLA/Fish meal composite, the most extractable potassium and magnesium were found in PLA/Canola meal composite, and the most extractable calcium was found in the PHBV/PLA/Blood and Bone composite.

For most composites, after 6 months of soil exposure, the extractable ammonium, phosphorus, calcium and magnesium had typically increased while the extractable sodium and potassium decreased overtime (Table 12). This indicated that with soil exposure more filler had become exposed through material breakdown and that the nutrients became accessible for extraction.

The fact that extractable nutrients after soil exposure were greater than before suggests that some materials had started to breakdown after soil exposure. There was not much difference between the 3 months and 6 months of exposure suggesting that extraction was limited to the exposed surface area.

Conclusions from Biodegradation Study 4

Overall, the PLA combined with PCL, PHBV or PBS polymer and 10% Blood and Bone filler or

10% Feather meal filler started to biodegrade during 6 months of soil exposure. The pure PLA/filler composites only showed physical deterioration in the form of cracking and possibly some degradation of the filler that was exposed on the surface. Increasing the Blood and Bone filler ratio in the PBS/PLA test strips from 5% to 20% did lead to more deterioration of the composite more during soil exposure.

Disclaimers

Purely for the sake of avoiding self-collision with any prior filed disclosure and/or claim made or foreshadowed, the applicant provides the following explicit disclaimers. Such disclaimers should not be taken as (mis)representing the generality of the invention described herein.

In some embodiments the present invention may not include:

• A composition including PBS:blood and bone, such as at a ratio of 90:10; and/or

• A composition including PBS:PLA:blood and bone, such as at a ratio of 60:30:10 and/or

75:15:10 and/or 45:45:10 and/or 30:60:10; and/or

• A composition including PBS:PLA:sheep pellets, such as at a ratio of 60:30:10; and/or

• A composition including PBS:PLA:starch, such as at a ratio of 60:30:10 and/or 45:45:10; and/or

• A composition including PBS:PLA:kiwifruit "hair", such as at a ratio of 60:30:10; and/or

• A composition including PBS:PLA:sanderdust, such as at a ratio of 60:30:10; and/or

• A composition including PBS:PLA:fishmeal, such as at a ratio of 45:45:10; and/or

• plant container and/or nursery pot and/or (plant) tray made from any of the compositions provided immediately above; and/or

• the use of a filler that is selected from: blood and bone; starch; sheep pellets; kiwifruit "hair"; sanderdust; fertiliser; fishmeal; soil conditioner; soil enriching agent; weed suppressant; processed organic matter; processed animal matter (such as sourced from land or marine species); and/or processed biological matter obtained from an animal (such as comprising animal carcass); and/or

• the use of a filler between 0.01-15% w/w of the composition, such as between 1-15%, such as between 5-15%, such as at least 10% w/w; and/or

• the use of a single filler in the composition; and/or

• the use of Polybutylene succinate (PBS), Polylactic acid (PLA), Polyhydroxyalkanoates (PHA), Polyhydroxyalkanoates (PHB), Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and/or combinations thereof; and/or

• the use of PBS in an amount between 50-95% w/w of the composition, such as PBS in an amount between 60-90% w/w, such as PBS in an amount between 80-90% w/w of the composition; and/or

• a blend of PBS and PLA, such as in a ratio of approximately 3:1 to 1:1, such as 2.5:1 to

1.5:1, such as 2:1.

Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising", and the like, are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense, that is to say, in the sense of "including, but not limited to". Conversely, the term "consists" or "consisting of" and the like are to be construed in an exclusive or exhaustive sense, that is to say , in the sense of "being limited to".

The entire disclosures of all applications, patents and publications cited above and below, if any, are herein incorporated by reference.

Reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that that prior art forms part of the common general knowledge in the field of endeavour in any country in the world.

The invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, in any or all combinations of two or more of said parts, elements or features. Where in the foregoing description reference has been made to integers or components having known equivalents thereof, those integers are herein incorporated as if individually set forth.

It should be noted that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of the invention and without diminishing its attendant advantages. It is therefore intended that such changes and modifications be included within the present invention.