Selective Filtratin Process For Biogas Production

FORM 2 THE PATENT ACT 1970 & The Patents Rules, 2003 PROVISIONAL/ SPECIFICATION (See section 10 and rule 13) 1. TITLE OF THE INVENTION 'Selective Filtration Process for Biogas Production/

2. APPLICANT (a) NAME (b) NATIONALITY (c) ADDRESS

1. Kirloskar Oil Engines Limited 2. Gangotree Eco Technologies Pvt. Ltd. Indian Companies registered under the provisions of the Companies Act/1956 1. Laxmanrao Kirloskar Path Khadki, Pune 411003, M.S. India. 2. Flat no.l Susheeldatta Aprs., Plot No.4, Padamarekha Society Karvenagar, Pune 411052, M.S., India. 3. PREAMBLE TO THE DESCRIPTION

PROVISIONAL The following specification describes the invention.

COMPLETE The following specificai particularly describesthe invention and the manner in which it is to be performed.

Technical field This is a method for biogas production. More particularly it relates to a method for segregating the two stages i.e. acidogenesis and methanogenesis in order to provide optimal conditions for the two sets of microbes and improving the efficiency of the plant for biogas generation. Prior art Generation of biogas from biomass is one of the several alternatives that are being attempted to get over the problems arising from shortage of fossil fuels. Conversion of biomass to biogas proceeds through a number of steps. Firstly, there is breaking down of the biomass into smaller units capable of penetrating the microbial cell wall. This is done through the mediation of exo-enzymes released by the microbial cell and results in hydrolysis or depolymerisation of complex biological matter. This is followed by acidogenesis that converts the smaller units into volatile fatty acids. These fatty acids in turn are converted into methane and carbon dioxide by a process called methanogenesis that is brought about by another set of microbes. The set of microbes that bring about acidogenesis are fast multipliers, can tolerate a downward shift of pH and an oxygenated environment. The set that brings about methanogenesis, however, are slow multipliers, perish at low pH values and need an anaerobic environment.

Cases of Prior Art and their Drawbacks: 1. United States Patent 4022665 An improved two phase anaerobic digestion process in which an initial phase continually receives an organic feed for short detention times of less than two days under conditions which efficiently liquefy and breakdown the feed to lower molecular weight acids and other intermediates for conversion to methane. A succeeding phase is operated to treat the lower molecular weight acids and intermediates for detention times of about two to about seven days under conditions which efficiently lead to production of methane. The feed is loaded in the first phase at rates from about 1 to about 10 pounds of total organics per cubic foot per day; and the products from the initial phase are loaded in the succeeding phase at rates of about 0.1 to about 0.5 pounds total organics per cubic foot per day. Drawbacks of Case One: As there is no separation of Micro organisms, every time they get drained out through the output slurry. This limits the speed of the process. 2.United States Patent 4696746 A two phase anaerobic digestion process for production of methane from organic carbonaceous material in which an active acid forming microbial population is maintained in a first acid forming digestion phase and an active methane forming microbial population is maintained in a second methane forming digestion phase, the liquid effluent from the acid forming digestion phase being passed to a first methane forming digester and gaseous product from the acid forming digestion phase being passed to a second separated methane forming digester for production of methane in the first and second

methane forming digesters of the methane forming digestion phase. The two separated methane digestion phases provide increased overall methane production. Drawbacks of Case Two: Micro organisms are not retained in their respective digesters. Every time they get drained out with the output slurry. limits the speed of the process. 3. Indian patent no. 210309 A three step biomethanation process, to convert starch or sugary agricultural feed stock into a methane rich gas mixture for facilitating generation of biogas to be used as kitchen fuels, electrical power or transportation from renewable biomass in a cost-effective manner. The process brings about conversion of starch-rich or sugar-rich biomass into methane through three stages, namely, hydrolysis, acidogenesis and methane formation. The present invention deploys enzymes/physical/microbial parameters to hasten the hydrolytic reaction in the first stage. It also deploys micronical consortia that have been enriched for a targeted feed in order to speed up the process of conversion. The formation of alcohol from starch is prevented as a result of the consortia deployed, the conversion efficiency is substantially improved and the retention time is also reduced to cut the capital cost of the plant. Drawbacks of Case Three: Though the process is divided into three stages, it is observed that no attempt has been made to retain the microbial consortia in the respective digesters. This limits the process speed, as every time the new bacteria needs to be generated.

4. U.S. Patent no. 5,529,692 A method for the biological processing of organic substances and more particularly for anaerobic biological hydrolysis for subsequent biomethanation, with pH value control, in the case of which the dissolved and/or un dissolved organic substances supplied to a first reactor are at least subjected to slight acidification in such reactor, the major part of the un dissolved, at least partly acidified organic substances taken from the first reactor are supplied to a second reactor for the performance of at least one solids hydrolysis step and the main part of the dissolved, at least partly acidified organic substances from the first reactor and from the second reactor are supplied to a third reactor for the performance of at least one methanation step. Drawbacks of Case Four: As there is no separation of Micro organisms for acid digester as well as for methane digester, the consortia get lost, every time they get drained out through the output slurry. This limits the work force for conversion of biomass into methane and thus limits the speed of the process. 5. U.S. Patent no. 4,781,836 An improved process for the biomethanation of an organic substrate includes treating the substrate in a first reactor to form organic acid anions, passing an aqueous preparation containing dissolved organic anions through an anion exchanger so that the organic acid anions are adsorbed and separated from the remainder of the aqueous preparation, desorbing the organic acid anions and passing the desorbed acids to a second reactor containing methanogenic bacteria which convert the acids to methane. In a preferred embodiment, a

bicarbonate solution is produced in the second reactor and it is used to desorb the organic acid anions and regenerate the anion exchanger into the bicarbonate form. Drawbacks of Case Five: In this isolated case where introduction of an ion exchange column overcomes such a loss of microbial population/ the feed streams have to be interrupted when the ion exchange resins get saturated with volatile fatty acids. Thus, after analyzing the limitations of these suggested Prior Art cases, the new inventive procedure was set up. Object of present invention Object of present invention is to provide method for segregating the two stages and improving the efficiency of biogas generation. Further more object of present invention is to provide a process to bring about a much faster conversion of feed into biogas without undue loss of the methanogens. Statement of present invention Present invention "Selective filtration process for biogas production" discloses a method for segregating the two stages and improving the efficiency of biogas generation. Segregation of two said stages is done with help of two separate digesters and balancing tank. The two streams are separated by the semi-permeable membrane e. g. the hollow fibre membrane unit that permits the migration and concentration equilibration of the low

molecule fatty acids and hydrogen ions but does not permit the migration of high molecular weight undigested/ semi-digested feed as also of microbial cells. The net effect of the two recirculations thus is to transport the volatile fatty acids to the methanogenic reactor and acidity neutralization, without exchanging the microbial populations. Description of present invention The foregoing objects of the invention are accomplished and the problems and shortcomings associated with prior art techniques and approaches are overcome by the present invention as described bellow in the preferred embodiment. Present invention "Selective filtration process for biogas production" comprises of following steps - The acidogenic and methanogenic stages of the overall process are carried out in two separate digesters. - An appropriate quantity of digested mass of the acidogenic digester is removed at regular intervals and remaining contents in the digester are mixed with slurry of the fresh feed, thereby adjusting the residence time and bringing about completion of the acidogenic phase. - The quantity of the acidogenic slurry so removed is stored in collection tank and further subjected to filtration and transferred to a storage tank.

A suitable semi permeable membrane device such as a dialyser or a hollow fibre ultra filtration unit is placed between the abovementioned storage tank and the methanogenic digester. - The contents of the storage tank (the VFA stream) are then circulated by means of a suitable pump through the hollow fibres of such ultra filtration unit and returned to the balancing tank. - The contents of the methanogenic reactor (the alkaline stream) are circulated by means of a suitable pump through that portion of the above filtration unit external to the fibres and returned back to the methanogenic tank. If necessary/ a filtration unit and a balancing tank are inserted in the line. - When in operation, the ultra filtration unit has two streams of fluids passing through it; the stream from the balancing tank (VFA stream), high in volatile fatty acid concentration and with a low pH passing through one (e.g. the inner channels of the hollow fibres) and the contents of the methanogenic digester (the alkaline stream) that is low in volatile fatty acids and with a high pH through the other (e.g. external to the hollow fibres in a hollow fibre unit) - The two streams are separated by the semi-permeable membrane (e.g. the hollow fibre membrane unit) that permits the migration and concentration equilibration of the low molecule fatty acids and hydrogen ions but does not permit the migration of high molecular weight undigested/semi-digested feed as also of microbial cells.

- The net effect of the two re circulations thus, is to transport the volatile fatty acids to the methanogenic reactor and acidity neutralization, without exchanging the microbial populations. The overall effect is to bring about a much faster conversion of feed into biogas without undue loss of the methanogens. The foregoing objects of the invention are accomplished and the problems and shortcomings associated with prior art techniques and approaches are overcome by the present invention described in the present embodiment. Detailed descriptions of the preferred embodiment are provided herein; however, it is to be understood that the present invention may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present invention in virtually any appropriately detailed system, structure or matter. The embodiments of the invention as described above and the methods disclosed herein will suggest further modification and alterations to those skilled in the art. Such further modifications and alterations may be made without departing from the spirit and scope of the invention; Advantages of present invention The method gets over the problems faced in the prior art of suboptimal conditions of a single digester and the risk of digester failure.

As the micro organisms are retained in their respective digesters, the process speed is improved. This results in reduction of capital cost, over the conventional digesters, for getting the same output. As the process oi biogas production is continuous i.e. without any break, we get the uniform and continuous source of energy. Date 4th October, 2008 M.D. Bhate Agent for applicant