FIELD OF INVENTION This invention relates to the field of a fertiliser. More particularly, the present invention relates to a method of producing a bio-fertiliser from organic waste which contains high amount of plant growth promoting bacteria (PGPB) and absorbable nutrients for a plant.

BACKGROUND OF INVENTION

Everyday a substantial amount of organic waste material is produced as a result of agricultural, industrial, and household activities. These activities can include, but are not limited to, crops harvesting, trees chopping, vegetable oil extraction, and cooking. Often organic waste refers to any biodegradable waste containing organic matter which can be broken down into carbon dioxide, water, methane, or simpler organic molecules by processes carried out by microorganisms. The organic waste can include, but is not limited to, residual food, tree trunks, rice husk, and empty fruit bunches.

Exponentially increasing amount of organic waste produced has becoming a major concern to the society because a safe and reliable method of disposing the waste is currently not available.

One of the most commonly adopted methods of handling the waste is by direct disposal in a landfill. However, it is known that landfill can cause numerous social and environmental impacts.

Harmful pollutants may leach out from the waste and contaminate the soil and water source.

Further, greenhouse gases are produced as a result of decaying waste in the landfill and can be flammable and potentially explosive.

More research effort has been done to finding alternative method of handling or disposing waste material, particularly the organic waste. One of which is to convert the waste into a fertiliser through degradation processes such as fermentation, composting, aerobic digestion, anaerobic digestion, or the like. Microorganisms, usually bacteria, are added to the waste to carry out the degradation processes when the waste is exposed to a favourable environment and subsequently converting the waste into an organic fertiliser, which contains organically derived primary nutrients, and sometimes, plant growth promoting bacteria (PGPB)that promote plant growth.

There are a few patented technologies over the prior art relating to methods of producing organic fertiliser. Chinese Patent No. 1103635 has disclosed a method of producing organic fertiliser from municipal waste. Collected waste is decomposed and turned into particles-like substance. The decomposed waste is then subjected to high temperature carbonisation. The pH of the carbonised waste is adjusted to a desired level and sieved to obtain organic fertiliser of a desired particle size, whereby the retentate is again subjected to decomposition and carbonisation. Minerals and trace elements are added to the waste as additional nutrients for plants.

Chinese Patent No. 102786362 has disclosed a method of producing an organic fertiliser which also a pesticide, and a composition thereof. Bamboo sawdust is carbonised at high temperature to obtain charcoal and bamboo vinegar. Moisture is added to rapeseed meal, dregs of traditional Chinese medicines, slow-release potassium chloride, Celastrus angulatus, and patrina. Paulownia sawdust, charcoal, bamboo vinegar, faeces, nitrogen-phosphorus-potassium compound fertilizer, and living bacteria are added for fermentation under high temperature environment. Thereafter, zinc sulfate, magnesium sulfate, sodium molybdate, and borax are added accordingly. One of the major drawbacks of the prior art is that the time needed for producing the organic fertiliser is incredibly long, thereby causing the cost of production exceptionally high. Further, the disclosed processes does not provide an effective way of minimising pollution from waste handling. The discharged effluent from the processes still contain a substantial amount of pollutant. The performance of the organic fertiliser is also not sustainable and satisfactory as frequent re-application of the fertiliser is needed due to fast depletion of the nutrients and organic matters, as well as fast decreasing of available living PGPB which are important to maintain a healthy soil condition.

To overcome the drawbacks of the prior art, there is a need for an improved method of producing organic fertiliser or bio-fertiliser having a low cost of production and a fast processing time which can provide a sustainable and satisfactory fertilising performance. SUMMARY OF INVENTION

One of the objects of the invention is to provide an improved method of producing a bio-fertiliser that is environmental friendly, fast, and cheap in cost of production.

Another object of the invention is to produce a bio-fertiliser which has an improved fertilising performance. Still another object of the invention is to produce a bio-fertiliser containing high amount of available organic and inorganic nutrients to a plant, as well as a sustainable amount of plant growth promoting bacteria (PGPB) that improve the absorption of nutrients by the plant.

Yet another object of the invention is to improve soil condition and provide a suitable environment for maintaining a sustainable amount of PGPB in soil.

At least one of the preceding aspects is met, in whole or in part, by the present invention, in which the embodiment of the present invention describes a method of producing bio-fertiliser from organic waste comprising the steps of (a) carbonising the waste in a carboniser at 250-750 °C for 5-13 hours; (b) gradually cooling the carbonised waste for 8-10 hours; (c) separating pyroligneous acid and wood tar from the gaseous products; (d) adding the pyroligneous acid, the wood tar, and plant-growth-promoting-bacterial (PGPB) growth factors to the carbonised waste; and (e) fermenting the mixture. In a preferred embodiment of the invention, the method further comprises a step of pulverising the carbonised waste prior to the step (d).

In another preferred embodiment of the invention, a portion of the gaseous products is recycled to the carboniser The recycled gaseous products are mixed with fresh air prior to carbonisation. The recycled gaseous products are residual gas from step (c). Still in another preferred embodiment of the invention, the pH of the mixture from step (d) is adjusted to 6-8 prior to fermentation.

A further embodiment of the invention is a system for separating pyroligneous acid and wood tar from gaseous products of carbonisation as claimed in any of the preceding claims comprising a condenser for allowing at least partial condensation of pyroligneous acid and wood tar; a water bath for dissolving pyroligneous acid and wood tar; an atomiser above the water bath for producing water mist to encapsulate a portion of the gas particles; and a gas purifying arrangement above the atomiser.

In another further embodiment of the invention, the system further comprises a gas pump for introducing the gas into the water, a bubbling means for inducing gas bubbles in the water, and a waterwheel within the water bath for encourage mixing of the gas and the water. The preferred embodiment of the invention consists of novel features and a combination of parts hereinafter fully described and illustrated in the accompanying drawings and particularly pointed out in the appended claims; it being understood that various changes in the details may be effected by those skilled in the arts but without departing from the scope of the invention or sacrificing any of the advantages of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For the purpose of facilitating an understanding of the invention, there is illustrated in the accompanying drawing the preferred embodiments from an inspection of which when considered in connection with the following description, the invention, its construction and operation and many of its advantages would be readily understood and appreciated.

FIGURE 1 shows two exemplary apparatus set-ups for the method as embodied by one of the preferred embodiments of the invention.

DETAILED DESCRD7TION OF THE INVENTION This invention relates to the field of a fertiliser. More particularly, the present invention relates to a method of producing a bio-fertiliser from organic waste which contains high amount of plant growth promoting bacteria (PGPB) and absorbable nutrients for a plant.

Hereinafter, the invention shall be described according to the preferred embodiments of the present invention and by referring to the accompanying description and drawings. However, it is to be understood that limiting the description to the preferred embodiments of the invention and to the drawings is merely to facilitate discussion of the present invention and it is envisioned that those skilled in the art may devise various modifications without departing from the scope of the appended claim.

The invention discloses a method of producing bio-fertiliser from organic waste comprising the steps of (a) carbonising the waste in a carboniser at 250-750 °C for 5-13 hours; (b) gradually cooling the carbonised waste for 8-10 hours; (c) separating pyroligneous acid and wood tar from the gaseous products; (d) adding the pyroligneous acid, the wood tar, and plant-growth- promoting-bacterial (PGPB) growth factors to the carbonised waste; and (e) fermenting the mixture. The term "organic waste" herein refers to any waste material containing biodegradable organic matter which can be broken down into carbon dioxide, water, methane, or simpler organic molecules by the action of microorganisms, particularly bacteria. The organic waste may include, but is not limited to, biogas residue, residual food, tree trunks, rice husk, and empty fruit bunches. Preferably, the organic waste used herein is derived from oil palm waste, such as palm kernel shells, empty fruit brunches, decanter cake of palm oil mill effluent, or palm fronds.

Although carbonisation generally refers to conversion of biodegradable organic matter into carbon or carbon-containing residue in an oxygen-depleted environment, the carbonisation process herein shall not be confused with the carbonisation process mentioned in any of the prior art. The conventional carbonisation of organic waste involves nearly complete conversion, usually above 90% conversion, of the organic matter into ash which is the simplest form of combustion or carbonisation product that mainly contains only carbon element or non-absorbable elements such as magnesium (Mg) or calcium (Ca), under high temperature. Most nutrients useful for plant growth, such as nitrogen (N), phosphorus (P), potassium (K), and some trace elements are degraded. However, the carbonisation herein aims to minimise ash formation and achieve higher amount of simpler carbon molecules that contain higher amount of absorbable nutrients for a plant.

According to the preferred embodiment of the invention, the waste is collected and carbonised in a carboniser (1) at 250-750 °C for 5-13 hours. Prior to carbonisation, it is preferable to comminute the waste into smaller particle size for the ease of handling. Basically, the comminute can be sorted into two sets, one with a particles size of 2.5 cm and below, the other with a particle size of above 2.5 cm. Preferably, the waste with a particles size of 2.5 cm and below is carbonised at 250-550 °C while the waste with a particles size of above 2.5 cm is carbonised at 250-750 °C. However, it is not necessary to pre-dry the waste though the waste commonly has a moisture content of 30% and below. Fire is ignited in the carboniser (1) for approximately 5-15 minutes at the presence of oxygen, preferably with a continuous supply of fresh air, to combust the waste. Thereafter, carbonisation is initiated by controlling the supply of air to stop the combustion but to continue heating the waste in an oxygen-limited environment. Preferably, the air supply during the carbonisation is oxygen-depleted or -limited air. Nevertheless, fresh air may be used as the air supply but a careful control on the incoming flow rate is needed to ensure the oxygen content in the carboniser (1) is controlled below a threshold to maintain the carbonisation instead of combustion.

Large carbon molecules in the waste is broken down into simpler carbon molecules but not completely turned into ash or carbon element. It shall be noted that the simpler carbon molecules shall contain a substantial amount of organic carbon and some absorbable nutrients which are necessary to be a precursor for producing the bio-fertiliser in later stage. As described by the preferred embodiment of the invention, the heating is terminated by stopping the air supply and the carbonised waste is allowed to gradually cool to room temperature for 8-10 hours. Despite heating is stopped after termination of the air supply, some carbon molecules may continue be broken down into simpler carbon molecules as long as the temperature of the carbonised waste is still at a favourable level.

While the carbonisation is taking place, pyroligneous acid and wood tar are separated from the gaseous products of the carbonisation, which also purifies the gas prior to discharge or further use. Hereinafter, the term "pyroligneous acid" can be used interchangeably with "wood vinegar" or "wood acid" and shall refer to a dark liquid produced through carbonisation, which occurs when ligneous material is heated in an oxygen-depleted environment. Likewise, "wood tar" is also a liquid obtained as one of the products of carbonisation of ligneous material. The pyroligneous acid and wood tar are separated by condensation and forced dissolution whereby an exemplary separation method is described in the following description.

The gaseous products are first passed through a condenser (2), preferably made from a hollow tube (2 A) configured in a serpentine fashion and jacketed by a coolant (2B), in which some pyroligneous acid and wood tar are condensed and collected at the bottom ends of the serpentine tube (2A). A discharge opening equipped with a control valve (2C) is located at the bottom end of the tube (2A). Thereafter, the remaining gaseous products are introduced to a closed water bath (3), forced to mix with the water by a pump (not shown), and converted into bubbles by a bubbling means (not shown). At the same time, a waterwheel (not shown) in the bath (3) further mixes the water and the gas. With such, a portion of the pyroligneous acid and wood tar as well as some other impurities are forced to dissolve in the water. A portion of the gas rising above the water bath (3) is brought into contact with mist produced by an atomiser (4) above the water bath (3) so as to force some of the pyroligneous acid, wood tar, and other impurities to fall back to the water bath (3). Preferably, a portion of the water in the bath (3) is atomised. The residual gas can be partially recycled or further treated with a gas purifying arrangement (5) before discharge. The pyroligneous acid and wood tar from the condenser (2) and the acid and wood tar-containing water from the water bath (3) are to be collected for further use.

In another preferred embodiment of the invention, the air supply is a mixture of fresh air and recycled gas. The recycled gas may be a portion of the gaseous products directly from the carboniser (1) or residual gas after separation of pyroligneous acid and wood tar. By mixing the fresh air with the recycled gas, the carboniser (1) can be operated at a higher temperature as the recycled gas is hot. However, the recycled gas directly from the carboniser (1) has a higher temperature than that of the residual gas after the separation process. The oxygen content of the air supply in the carboniser (1) can be controlled and reduced as the nature of the recycled gas is oxygen-depleted. In short, the oxygen content and temperature in the carboniser (1) can be controlled by controlling the flow rate of the air supply, amount of recycled gas in the air supply, and the type of the recycled gas, and the abovementioned parameters could be controlled by the use of control valves (6A) and blower fan (6B) at various position of the apparatus set-up, as illustrated in FIGURE 1.

In accordance with the preferred embodiment of the invention, pyroligneous acid, wood tar, and plant-growth-promoting-bacterial (PGPB) growth factors are added to the carbonised waste. Optionally, palm oil decanter cake, palm oil mill effluent (POME), and palm ash can be further added to the carbonised waste. Preferably, the carbonised waste is crushed into particle size of 1 - 200 mesh to increase the surface area of thereof for subsequent bio-reactions. However, sieving is not necessary. The pyroligneous acid and wood tar are preferably obtained from the abovementioned separation step. However, it shall not limit the use of wood vinegar or wood tar obtained from other sources. By adding the wood vinegar, the pH of the mixture is adjusted to 6- 8 which is favourable for cultivation of PGPB and fermentation of the mixture. The addition of wood vinegar and wood tar are particularly necessary as they contain various elements and compounds that are useful for plant growth and soil conditioning as well as promoting sustainable growth of PGPB. PGPB growth factors are a bacteria attracting agent which creates a favourable environment that attracts PGPB to grow. The bioactive comprises a mixture of nutrients, such as sugar and protein, enzymes, and citric acid which are required for cultivation of PGPB. It shall be noted that the PGPB are not added to the carbonised waste but they are attracted to continuously grow thereon by providing a suitable environment for them to live. Hence, the amount of the PGPB is always sustainable.

As depicted in the preferred embodiment of the invention, the mixture is subsequently exposed to an environment favourable for fermentation. Particularly, the mixture is allowed to ferment, by the action of the PGPB, at a 50-70 °C for 2 hours to 5 days. It is important to ensure that the environment has sufficient aeration for providing oxygen to the PGPB to carrying out aerobic processes. During fermentation, insoluble carbonaceous materials or any other non-readily absorbable plant nutrients are converted, by the action of the PGPB, to readily absorbable organic carbonaceous materials or nutrients. With such, the suitability of the environment for bacteria growth is also maintained simultaneously. Since a suitable environment is provided, the fermentation process continues even the mixture is removed from the fermentation environment.

The fermented waste or the bio-fertiliser shall contain at least 500,000 Bacillus spp. per gram of waste, total nitrogen, phosphorus, and potassium (NPK) content of 9-15wt%, and organic matter of at least 50wt%. Further NPK and other nutrients such as magnesium oxide (MgO), boron (B), and trace elements can be added to the bio-fertiliser according to the needs of various plants. When in use, the bacteria in the fertiliser continuously promote plant growth by preventing deleterious effects of phytopathogenic organisms and producing plant hormones. The bacteria also increases the absorbable nutrients in soil by solubilising the nutrients, enhancing resistance to stress, stabilising soil aggregates, and improving soil structure and organic matter content. The bacteria also retain more soil organic N, and other nutrients in the plant-soil system, thus reducing the need for inorganic fertiliser containing NPK and enhancing release of the nutrients.

A further embodiment of the invention is a system for separating pyroligneous acid and wood tar from gaseous products of carbonisation as described in any of the preceding description comprising a condenser (2) for allowing at least partial condensation of pyroligneous acid and wood tar; a water bath (3) for dissolving pyroligneous acid and wood tar; an atomiser (4) above the water bath for producing water mist to encapsulate a portion of the gas particles; and a gas purifying arrangement (5) above the atomiser (4).

As illustrated in FIGURE 1, it is preferable that the condenser comprises a hollow tube (2A) configured in a serpentine fashion where the gas is passed through. The tube (2A) is jacketed with a coolant (2B), preferably a water coolant, which causes condensation of wood vinegar and wood tar within the tube (2A). A water pump (not shown) may be provided for introducing a portion of the water from the water bath (3) to the atomiser (4). The gas purifying arrangement (5) further remove any impurities and pollutants from the gas prior to discharge. In another further embodiment of the invention, a gas pump (not shown) is provided for introducing the gas into the water. The gas pump can be of any type that capable of forcing the gas to diffuse within water and allow appropriate mixing between the gas and the water so that some of the pyroligneous acid, wood tar, and other impurities could be dissolved. Preferably, a bubbling means (not shown) is provided for inducing and converting the gas into bubbles in water, which further enhance dissolution of pyroligneous acid, wood tar, and other impurities in water. Still in another further embodiment of the invention, a waterwheel (not shown) is provided within the water bath (3) for encourage further mixing of the gas and the water. It is important to prolong the contact time between the water and the gas to allow higher amount of dissolvable material to dissolve in water, including the pyroligneous acid and wood tar. Also in another further embodiment of the invention, the gas purifying arrangement comprises two sections, in which a first section handles wet gas while a second section handles dry gas. Moisture gas is purified in the first section to form pyroligneous acid. Serpentine condenser tube is preferably first utilised to condense any moisture and acid. Immediately after the condenser tube is a two-stage filter, in which the first stage removes majority of moisture and large gas particles while the second stage is a filter membrane of 1-5 μηι pore size which removes smaller gas particles to achieve purification efficiency of 60-90%. Remaining dry gas from the first section is further treated in the second section. The second section may include a plurality of filters such as activated carbon, ionic filter, magnetic filter, and electrostatic filter. With such treatment, impurities in gas could be removed simultaneously and renders the discharge gas cleaner and less polluting.

Although the invention has been described and illustrated in detail, it is to be understood that the same is by the way of illustration and example, and is not to be taken by way of limitation. The spirit and scope of the present invention are to be limited only by the terms of the appended claims.