"A METHOD FOR ANAEROBIC PROCESS COUPLED SEPARATION AND REFINING OF PLANT MATERIALS"

Field of the invention

This invention relates to the process of extraction of plant materials bound in tissues by employing anaerobic sludge. More particularly, this invention enables the faster extraction of plant fibres such as banana fibre, pineapple leaf fibre, jute and allied fibres, sisal fibre and tender coconut husk fibre by a clean and non-polluting anaerobic process.

This invention also effects extraction of pepper kernels, the white pepper from processed, dried black and unprocessed, fresh pepper {Piper nigrum L.) berries undamaged. Still more particularly, this invention relates to a process of cleaning plant products in usable forms by effecting the rapid degradation of cementing materials and coatings and bioconversion of degraded plant compounds to methane, a gaseous valuable fuel.

Background to the invention

The plant fibres of flax, jute, rhea, hemp, ramie, coir, banana, pineapple, etc. are of extreme importance in many applications and their growing demand urges the need for developing better and cleaner extraction methods. The extraction and preparation of quality plant fibres has been a challenging problem, as many of the attempted and practicing methods have many limitations such as high cost of production, environmental pollution, inadequate quality for making valuable products, poor yield due to higher level of damages, etc.

The Banana fibre produced today is mostly used for ropes and cordage, ships cables etc. It is also used for making hoisting and power transmission ropes, wet drilling cables, fishing nets and liner, and other types of cordage where strength, durability and flexibility are essential. Also banana fibre is used in the manufacture of strong high grade paper, plywoods, card board, craft paper, packing cloth for agriculture produce, carpets, table mats, hand bags, fancy articles, cushioning material etc.

Initially the extraction of fibres has been carried out mainly through manual operations and it is being continued even now in some parts of the world for the extraction of certain fibres like pineapple leave fibres and banana stalk fibres. Mechanical separation of the fibres using specially designed apparatus is already known in the art, GB190813897 Drews, J. O. June 30,1908; GB153413, Drews, J. O., and Noorden, A. van. Aug. 30, 1919; GB735551, Obtaining fibres from plant parts. HEYER, G., VON. Sept 2, 1953; GB191013220, Stark, E. G. May 31, 1910.

Banana fibre is usually produced from waste pseudostem of banana plant. The outer sheaths of the stalk are tightly covered by layers of fibre, which contains fibre to the extent of approximately four per cent of its weight. The fibre is located primarily adjacent to the outer surface of the sheaths and can be peeled-off in ribbons of strips of 5 to 8 cm wide and 2 - 4 mm thick, in the entire length of sheath. This hand stripping process of separation of fibre from spongy tissues is widely followed in the countries like Philippines and India. Clean fibre is then air dried and made up into bundles for subsequent grading and bailing.

In addition to hand stripping, machines are used to cut banana trunks into sections of 120 to 180 cm in length. The sections of stalks are crushed between rolls and the pulpy tissues are scraped away from the fibres which is then oven dried, graded and baled. Details of this process is described in GB190813897, 13,897, Drews, J. O. June 30,1908; GB153413, 153,413, Drews, J. O., and Noorden, A. van. Aug.30,1919. Mechanical operations for the extraction of the banana fibre simplifies the fibre separation to a certain extent, but heavy damage of the fibres is obviously observed in mechanical separation along with higher level of material wastage and its disposal remains as a threat in the mind of people to adopt this method (National Research Centre for Banana at Tiruchi, Tamil Nadu, India).

The tender coconut husks are not utilized for the extraction of fibre so far since there is no suitable method of extraction available today. Traditionally retting is the method followed for the preparation of white coir fibre from matured coconut husks, as well for the preparation of plant fibres like jutes. The method of mechanical extraction of coir

fibre from coconut husk is also widely used, but this process particularly results inferior quality fibres, and in the case of tender coconut husks the fibre becomes unusable for applications because of the heavy coating of polyphenols over the fibre during the process.

Refining of plant materials such as natural fibres from leaves and stems, and extraction of white pepper from black and green pepper {Piper nigrum L.) are carried out by different methods which include retting. Retting of different plant materials for the preparation of smooth and quality plant fibres types has already been patented and are GB190200244, Steenkiste, A. van. Jan. 3., 1902; GB190806532, Rossi, G. March 24.; GB191121801, Schreckenbach, R. Nov. 29, 1910; GB191013220, Stark, E. G. May 31;. GB191110812, Silberrad, O. May 4; GB191417941, Meister, J. Sept. 27, 1913; GB 147080, Wolkinzon, A. April 17, 1919; GB 173598, Kawabe, T. Oct. 1, 1920; The patent US4891096 specifies direct use of enzymes for retting of phloem-fiber plants such as hemp, flax, ramie, jute, kenaf, etc. Augmentation of retting process by aerobic treatment of process liquor is developed in the patents, GB825704, CA2153177 that claims to use activated sludge process that eliminates inhibitory effects of volatile fatty acids such as acetic acids in retting; GB302300302, Waddell, M., and Watson, H. C. Sept. 14, 1927; The dew retting of flax given in RU2181797, 2002 by which excess water use is avoided; US 20030041965; GB191110812, Silberrad, O., in which the invention facilitates aerobic decomposition of organic components in two phases. Above methods provide incremental advantages over traditional method of retting, but do not confer solutions to process delay, product quality deterioration and environmental pollutions considerably.

The processing of smooth plant fibres such as flax, hemp, rhea, ramie, kenaf, jute etc. have been attempted through a combination of mechanical and chemical or chemical processing with and without heating, are given in the patents, GBl 89711804, Prinz, A. H. May 12,1897; GB190828163, Malcolmson, N., Dec. 24,1908; GB191027570, Del Prato, G., Del Prato, V., Del Prato, C, and Del Prato, M. Nov. 26; GB 173598, Kawabe, T. Oct. 1, 1920; GB353868, Retting flax &c. Rohm & Haas Co., 222, West Washington Square, Philadelphia, U.S.A, March 28, 1930.

It is also understood from the prior arts that various methods have been tried to produce white pepper from matured green or black pepper, but a suitable technology to produce good quality white pepper from pepper berries is still unavailable. Mechanical polishing is specified to produce white pepper from nuts of black pepper (JP 10276714, Satake Eng. Co. Ltd., 1998-10-20).

White pepper is traditionally prepared by retting method in which the matured green pepper berries are separated from spike after harvest. The separated berries are filled loosely in gunny bags or knitted nylon bag of 25-50kg capacity and are soaked in flowing water stream or rivers for 2-3 weeks (Natarajan, 1967, Some aspects of spices research. Ind. Food Packer, 21(3), 12-15; Lewis, Y.S., Neelakantan, S., Philip,T., Nambudiri, E.S. (1968) Production of white pepper in India. Spices Bull, 5(6), 6-8; Lewis, Y.S., Nambudiri, E.S., Krishnamurthy, N., Natarajan, CP. (1969a) White pepper. perfum. Essent. Oil Rec, 60, 53-56). The removal of pepper skin has also been done by soaking of pepper in concrete tanks for more than nine days (Sudharshan, M.R. 'White pepper' a simple value addition to pepper, Spice Ind.,13(6), 10-12, 2000). About 10-15 days of soaking in running water is practiced for the complete removal of skin from the berries. After retting the skin is mechanically or manually removed by trampling. After thorough washing the pepper is sun dried to the moisture level of 8-12 % (Madhusoodanan, K.J., Radhakrishnan, V., Priyadarshan, P.M., Kuruvilla, K.M., Naidu, R., A cost effective method for the production of white pepper. Ind. Spices, 3 (2), 5-7. 1990). Major disadvantages of the above methods are the long retting period of 10- 15 days, the development of a characteristic foul smell, fading of colour, loss of piperine and retention of microorganisms (Natarajan, C. P., Lewis,Y.S., Nambudiry, E.S., Krishnamurthy, M.N. Production of white pepper, pepper oil and oleoresin. Ind, Spices, 3, 38 - 41(1967); Lewis, Y.S., Important spices from south East Asia cultivation and technology. Im/. Food Pack., 36(1), 62-71,1982).

In view of the above drawbacks in the prior art, the present invention proposes to obviate problems of extraction of plant materials in the prior art and provides solution for the release of plant fibres from the amorphous matrix of pectin, hemicellulose, celluloses and phenolic esters in pseudo stems of banana, leaves of pineapple and sisal, coir fibres from mature and tender coconut husks.

Object of invention

It is therefore the primary object of the invention to enable clean extraction of plant materials.

It is another object of the invention to remove pollutants generated in the biological extraction of plant materials.

It is still another object of the invention to generate biogas as a fuel from the pollutants in the extraction water.

It is yet another object of the invention to shorten the time required for the extraction of plant materials.

It is still another object of the invention to reuse water for the extraction plant materials.

It is yet another object of the invention to provide fast removal of skins of dried black or fresh pepper berries for making white pepper while the pollutants are converted into gases and removed.

Summary of invention

Accordingly the invention provides a process for the extraction of a solid and fibrous product from embedding natural matrices of plant based raw materials comprising

- soft crushing of the said plant materials to result easy liquid passage for extraction of fibre,

contacting the said raw materials with an aqueous liquor and a biomass of anaerobic sludge capable of depolymerisation and solubilization of the said embedding matrices,

- removing the said aqueous liquor containing soluble extracts of the said embedding matrices,

- passing the said aqueous liquor through an anaerobic reactor wherein the soluble extracts are gasified and removed as a methane rich gas at biological conditions of 10 to 5O ⁰ C and pH between 4.0 to 8.0,

- returning the liquor for contacting with the said raw materials and repeating the process till the said product is sufficiently detached from the said embedding matrices.

According to the preferred embodiment of the invention, soft crushing of plant materials is performed to result easy liquid passage for extraction of fibre such as pineapple leaves, sisal leaves, banana stems and tender coconut husks of 5-9 months old, followed by soaking of the materials in a liquor containing biomass of anaerobic sludge with or without microbial seeding, which enables leaching out water soluble and cementing materials of the fibre in the matrices and circulation of the liquor containing dissolved materials into at least one anaerobic system operated at biological conditions of 10 to 5O ⁰ C and pH between 4.0 to 8.0 thereby degrading the dissolved materials and then converting it to volatile fatty acids. The resulting volatile fatty acids is further converted to biogas and removed from liquor as biogas by the process of methanogenesis, enabling the reuse of the liquor for continuous soaking of the plant materials to be processed viz, banana stems, pineapple leaves, sisal leaves, tender coconut husks and continue the process till plant fibres are sufficiently loosened from bonding so as to make the separation of the materials easy from the matrices. This is also applied in the extraction of pepper kernel, the white pepper from dried black or fresh pepper berries which do not require crushing in this process unlike in fibre extraction.

According to a feature of the present invention a clean process for the release of plant fibres embedded in natural amorphous matrix of pectin, hemicellulose, celluloses and phenolic esters in pseudo stems of banana, leaves of pineapple, leaves of sisal, stems of jute and tender coconut husks. This invention also facilitates fast removal of skins of dried black or fresh pepper.

In an embodiment of the present invention, the plant product is banana fibre or pineapple fibre or tender coconut fibre or jute and allied fibre.

In another embodiment of the present invention, the plant product is pepper kernel

embedded in fresh green pepper {Piper nigrum L.).

In yet another embodiment of the present invention, the plant product is pepper kernel embedded in dried black pepper {Piper nigrum L.).

In a further embodiment of the present invention, the plant fibres embedded in banana pseudo stem sheath are extracted by contacting with the said aqueous liquor for a period of at least 3 days.

In another embodiment of the present invention, the pineapple fibres embedded in pineapple leaves are extracted by contacting with the said aqueous liquor for a period at least 2 days.

In still another embodiment of the present invention, the plant fibres embedded in the stalk of jute or allied plants are extracted by contacting with the said aqueous liquor for a period of at least 3 days.

In yet another embodiment of the present invention, the plant fibres embedded in tender coconut husks are extracted by contacting with the said aqueous liquor for a period of at least 2 weeks.

In another embodiment of the present invention, the plant product embedded in fresh green pepper {Piper nigrum L.) berries is extracted by contacting in said aqueous liquor for a period of at least 2 days.

In still another embodiment of the present invention, the plant product embedded in fresh black pepper {Piper nigrum L.) berries is extracted by contacting in said aqueous liquor for a period of at least 2 days.

In yet another embodiment of the present invention, the contacting is carried out in one or more contacting vessels connected to enable circulation of said liquor pumped between said contacting vessels and said anaerobic system.

In a further embodiment of the present invention, the vessels have provisions to prevent

entry of air into said liquor.

In still further embodiment of the present invention, the vessels have provisions to prevent exchange of gases between atmosphere and anaerobic systems. In yet another embodiment of the present invention, the rate of circulation is such that pH of liquor in the contacting vessel is maintained between pH 3.0 and pH 8.0.

Detailed description of the invention The preferred embodiments of the invention are discussed in detail below. While specific steps, configurations and arrangements are discussed, it should be understood that this is done for illustrative purpose only. A person skilled in the art will recognize that other steps, configurations and arrangements can be used without departing from the spirit and scope of the present invention. While the foregoing description assumed a particular embodiment it will be appreciated that the present invention may be used in numerous other embodiments and other examples.

The present invention for quality plant fibre extraction and white pepper production is less time consuming, and pollution free. This method facilitates faster release of compounds fixing plant fibre in the matrices of banana sheath in the stalk of banana, in pineapple leaves, in sisal leaves, jute like plant and in tender coconut husks. This method also enables faster detachment and degradation of the skin of green or black pepper. The present invention provides improved performance because of the crushing the banana sheath of banana stalks, sisal leaves, pineapple leaves and tender coconut husks, rapid microbial growth and participation in bioconversions while soaking; conversion of released pollutants to methane gas by passing through reactions at least in a system maintained anaerobic and connected to soaking tanks where plant materials are placed. The microbial activity further enables to degrade binding carbonaceous matter in the matrices of fibres and pepper kernel to simpler molecules by enzymatic reactions. The plant fibres and pepper berries are freed and refined from binding matrices in this process by enzymatic actions of sludge microorganisms of in-situ and in the anaerobic system connected.

Microorganisms involved in anaerobic sludge digestion - various physiological groups of bacteria occur in anaerobic sludge digestion tank. Although fungi and protozoa have

been found, they occur in very low number. The digestion process itself is believed to be carried out significantly by bacteria.

There are three different groups of bacteria occurring in this process: hydrolytic, fermentative and methanogenic bacteria. However, there is some overlap between the members of the first two groups.

Among the non-methanogens involve Bacillus, Pseudomonas, Lactobacillus, Spirillum, Vibrio, Klebsiella, Alcaligens and Micrococcus are the facultative anaerobes and Clostridium and Bacteroides are the obligate anaerobes. Methanogens include Methanobacterium, Methanococcus, Methanosarcina, Methanospirillum and Methanomicrobium.

The entire process is preferably carried out in the biological conditions and free of oxygen. It has been observed by the inventors that oxygen contact in the process leads to the formation of compounds that are toxic to the microorganisms in the degradation and methanogenic reactions. The exposure of oxygen causes dark unattractive coloured coatings over the plant fibres, which deteriorates quality of plant products severely. The oxygen contact delays in decortication of pepper and sometimes supports fungal growth which is undesirable to skin removal process. More exposure to oxygen leads to the formation of dark coloured liquor and that dark colour compounds are highly toxic to microorganisms and resistant to anaerobic biodegradation, which ultimately halts the anaerobic processes. In fact, biological processes are not then suitable for the removal of these coloured materials which have the nature of polymeric phenols and tannins. These compounds are undesirable in the environment because of its long persistence, surface absorption properties and dark colour. It is a major component of the environmental nuisance from the current retting practices of fibre extraction process. In this invention, the pollution problem is avoided in the extraction of fibre and pepper berries by degrading and converting colouring compound precursors to methane. The generation of methane from solubilized and degraded binding materials makes this anaerobic extraction process a net energy producer as well as clean method. In the usual practices wastes are generated as solids, liquids or gases and cause heavy environmental pollution. In the case of gases which are emitted to the atmosphere and thus contributing to global greenhouse gas emissions.

The applicants have observed that, if the banana stalks, sisal leaves, pineapple leaves and tender coconut husks are crushed without damaging fibres, it enables faster separation of fibre. The crushing operation can be done before dipping in water or after in the absence or presence of oxygen. Elimination of colour formation in the medium is completely eliminated by avoiding oxygen contact. This is as a result of improved mass transfer, particularly in the solubilisation phase when bulk of the binding material is leached out by physico-chemical actions. After the easily soluble compounds are removed, the second phase of activity is as a result of microbial enzyme action from established growth of anaerobic sludge in the system, where insoluble binding compounds are solubilized and degraded. The sludge activity is retarded if the initially leached compounds accumulate in the retting liquor or change of water with dissolved oxygen. Severe drop in the liquor pH and build up of organic acids takes place if the easily soluble compounds are allowed to accumulate in an inappropriate condition.

White pepper preparation through retting in prior arts, the 'soak liquor' is removed in running water and causes severe pollution or heavy pollution in the ground water where the black or green pepper (Piper nigrum L.) is soaked for 10-15 days. Similarly the plant fibre extraction also causes water pollution with exchange of fresh water for removing the soak liquor. This has the disadvantage of needing discharge of high strength wastewater in addition to increased water consumption. The oxygen contact with soak liquor allows generation of tougher organic compounds from the precursors of leached molecules from plant materials. In this invention, the liquor is recirculated after removal of its organic fraction in the anaerobic reactor through degradation and biomethanation, thus avoiding pollution and permitting faster establishment of anaerobic biomass by recycling nutrients and maintaining anaerobiosis. The biodegradable wastes are converted to methane in this invention simultaneously, which can be collected for fuel source.

Flow chart for plant fibre extraction

On completion of processing fibre and white pepper the soak liquor will also be freed of organic contaminants from the anaerobic degradations and biomethanation reactions. After removing the products, the fibres or white pepper, the soak liquor can be reused for a new batch of materials.

This invention facilitates easy extraction of fibres from various plants as described previously and white pepper of superior quality in terms of brightness and smoothness, in shorter periods. The applicants have also observed that the coating of colouring compounds occurs in the prior arts are avoided in the new process and thus results in cleaner products.

Flow chart for white pepper preparation

This invention discloses a process having several advantages which include zero aquatic pollution achieves by recycling the used water after anaerobic treatment, prevention of air pollution, production of better quality plant materials. It also reduces processing time, controls damages in processing substantially, minimizes the wastages and solid waste disposal problem, reduces hard labor, eliminates occupational health hazard and enables direct collection and utilization of methane as a fuel.

EXAMPLES

The following examples are given by way of illustration and therefore should not be construed to limit the scope of the present invention.

Example 1 Six sheaths of banana pseudostem from exterior to interior, the raw material for the extraction of fibre of 361.8 gm was kept in a cylindrical glass vessel of 4 litre volume with 3.5 litre water freed of oxygen by stripping with nitrogen gas. Exchange of air and gases was prevented in the system by closing the glass vessel with a glass lid. The closed glass vessel was provided with a liquid inlet, a liquid outlet and a gas outlet connected to a meter on top. The liquor of the vessel was circulated using the connected rubber tubes of 7 mm internal diameter through a hybrid anaerobic glass reactor of 9.0 litre working volume, having anaerobic expanded sludge of 2 litres at the bottom, floating pall rings on top with retained biomass. The reactor liquor pH was in between 5.8 to 7.9 and mostly in the near neutral range of 6.2 to 7.6. Anaerobic sludge capable of degrading waste plant materials and converting to methane was developed by feeding soak liquor of banana stalk and seeding anaerobic sludge from a canteen waste treatment plant to the above stated hybrid reactor. The entire experimentation was conducted at the temperature between 18° and 35° Celsius. Biogas from the anaerobic reactor was metered in a gas flow metre connected to the reactor which was maintained between 18° and 35° Celsius. The circulation of liquor was continued till the gas production from the liquor reduced to negligibly low to measure. Total biogas produced over a period of 7 days was 70 litres/kg dry weight of sheath from glass vessel containing stalk and anaerobic reactor. The fibres of the banana stalk sheath were detached from bindings of surrounding pith tissues in a week and that resulted in the easy cleaning of fibres by simple agitation in

water. At the end of experimentation the fibres and other materials were estimated and the data is presented in Table 1.

The experiment was also done after crushing the banana stalk sheaths prior to placing in water as detailed in experiment 1 and the results are presented in Table 2.

Table 1. Material balance in fibre extraction experiment with banana stalk sheath

Table 2. Material balance in fibre extraction experiment with banana stalks pressed between two steel rollers.

Example 2

Four pineapple (Ananas comosus) leaves crushed and uncrushed, were kept in a cylindrical glass vessel of 4 litre volume with 3.0 litre water free of oxygen by stripping with nitrogen gas using distributor. Exchange of air and gases was prevented in the system by closing the glass vessel with a glass lid. The closed glass vessel was provided with a liquid inlet, a liquid outlet and a gas outlet connected to meter on top. Liquor of the vessel was circulated using the connected rubber tubes of 7 mm internal diameter through a hybrid anaerobic glass reactor of 9.0 litre working volume, having anaerobic

expanded sludge of 1.5 litres at the bottom, floating pall rings on top with retained microbial biomass for biomethanation. The reactor liquor pH was in between 6.0 to 7.8 and mostly in the near neutral rage of 6.5 to 7.5. Anaerobic sludge of microbial biomass capable of degrading waste polymeric plant materials and converting to methane was developed by feeding soak liquor of pineapple leaves and seeding of anaerobic reactor sludge from a canteen waste anaerobic treatment plant to the above hybrid reactor. The entire experimentation was conducted at the temperature between 20° and 35° Celsius. Biogas from the anaerobic reactor was metered in a gas flow metre connected to the reactor which was also maintained between 20° and 35° Celsius. The circulation of liquor was continued till the gas production from the liquor reduced to negligibly low to measure. Total biogas produced over a period of 7 days was 53 litres/kg dry weight of leaves from the glass vessel with plant leaves and anaerobic reactor. The fibres of the pineapple leaves were detached from bindings of surrounding pith tissues in a week and that resulted in the easy removal of fibres by simple agitation in water. At the end of experimentation the fibres and other materials were estimated and the data is presented in Table 3.

Table 3. Material balance in fibre extraction experiment with pineapple leaves: crushing was effected between two steel rollers.

Example 3

Tender coconut husks of 6 to 8 months old coconuts were obtained after removing the nuts, the raw material for extracting coir fibre was kept in a glass rectangular tank with 60 litre water freed of oxygen by stripping with nitrogen gas. The glass tank was covered with a lid to prevent exchange of gases. The closed tank was provided with a liquid inlet,

a liquid outlet and a gas outlet and a gas collector on top. Liquor of the tank was circulated through a hybrid anaerobic glass reactor of 9.0 litre working volume, having anaerobic sludge of 3 litres at the bottom, floating pall rings on top with attached biofilm by means of a poly vinyl chloride pipe line connection of V ₂ inch diameter. The reactor liquor pH was in between 6.0 to 7.9 and mostly in the near neutral rage of 6.6 to 7.5. Anaerobic sludge of microbial biomass capable of degrading plant wastes and converting to methane was developed initially by feeding soak liquor of coconut husk and seeding of anaerobic reactor sludge from canteen waste treatment plant to the above hybrid reactor. The entire experimentation was conducted at the temperature between 20° and 35° Celsius. Biogas from the anaerobic reactor was metered in a gas flow metre attached to the reactor which was also maintained between 20° and 35° Celsius. The circulation of liquor was continued till the gas production from the liquor reduced to negligibly low to measure. Towards the later half of the operation, gas production was also begun in the husk placed tank. Total biogas produced over a period of 40 days was 150 litres/kg dry tender coconut husks, from soaking tank and anaerobic reactor together. The surrounding matrices of fibres in the husk were degraded and that resulted in the easy removal of fibres by simple agitation in water or in mechanical defibre unit. The results of experimentation with 6-8 months old coconut husks are presented in tables 4, 5 and 6 respectively.

Table 4. Material balance in fibre extraction experiment with 6 months old tender coconut husks

Table 5. Material balance in fibre extraction experiment with 7 months old tender coconut husk

Table 6. Material balance in fibre extraction experiment with 8 months old tender coconut husk

Example 4

Black pepper (Pieper nigrum L) were procured and dried to moisture content 11%, washed in tap water and samples of 250 gm to 1000 gm were kept in a cylindrical glass vessel of 4 litre volume with 3.0 litre water free of oxygen by stripping with nitrogen gas. Exchange of air and gases was prevented in the system by closing the glass vessel with a glass Hd. The closed glass vessel was provided with a liquid inlet, a liquid outlet and a gas outlet connected to a meter on top. Liquor of the vessel was circulated using

the connected rubber tubes of 7 mm internal diameter through a hybrid anaerobic glass reactor of 9.0 litre working volume, having anaerobic expanded sludge of 1.3 litres at the bottom, floating pall rings on top with retained microbial biomass. The reactor liquor pH was in between 5.7 to 7.8 and mostly in the near neutral rage of 6.3 to 7.5. Anaerobic sludge capable of degrading skin of pepper berries and converting to methane was developed initially by feeding soak liquor of pepper and seeding of anaerobic reactor sludge from canteen waste treatment plant to the above hybrid reactor. The entire experimentation was conducted at the temperature between 18° and 35° Celsius. Biogas from the anaerobic reactor was metered in a gas flow metre connected to the reactor which was also maintained between 18° and 35° Celsius. The circulation of liquor was continued till the gas production from the liquor reduced to negligibly low to measure.

Total biogas produced over a period of 4 days was 15 litres/kg black pepper from the glass vessel with pepper and anaerobic reactor together. The skins of pepper berries and pectin bindings between mesocarp layer of skin and pepper kernel were degraded and easily detached from bindings to kernel in 4 days, and that resulted in the removal of skin by washing in water. At the end of experimentation the white pepper and other materials were estimated, and the data is presented in Table 7, 8 and 9.

Table 7. Material balance in bioextraction experiment with 250 gm pepper

Table 8. Material balance in bioextraction experiment with 1000 gm pepper

Table 9. Material balance in bioextraction experiment with 500 gm pepper

Although the invention has been described with reference to the specific embodiment, the description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternate embodiments of the invention will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore contemplated that such modifications can be made without departing from the spirit and scope of the present invention as defined in the appended claims.