FORM-2
THE PATENTS ACT. 1970
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION
"A SYSTEM FOR BIOGAS PRODUCTION BY DUAL PHASE ANAEROBIC PROCESS."
2. APPLICANT
a) NAME: Kirloskar Integrated Technologies Limited
b) NATIONALITY: An Indian Company registered under the provisions of the
Companies Act, 1956.
c) ADDRESS: 13/A, Karve Road, Kothrud, Ptme- 411038.M.S. India.
2.A. INVENTORS
a) NAME: GOYAL DEVENDRA JAYANT
b) NATIONALITY: An Indian national
c) ADDRESS: A7/17, Vishnu Vihar, Bibevevadi Kondhwa Road, Bibevevadi,Pune
411037, Maharashtra, India.
2.A) NAME: MATE NITANT VISHNU
b) NATIONALITY: An Indian national
c) ADDRESS: 9 ' Shriman', 793 Bhandarkar Road, Pune-411004, Maharashtra, India.

3.a) NAME: JOSHI ASHWIN SHARAD
b) NATIONALITY: An Indian national
c) ADDRESS: Plot No. 7, "Radharang", Sanjeevraje Nagar, Girvi Road,Phaltan.
Dist. Satara -415523, Maharashtra, India.
4.a) NAME: KHOT NIKHIL APPASAHEB
b) NATIONALITY: An Indian national
c) ADDRESS: Flat No. 306, Dhruva Residency, 250B/28, Nagala Park, Near
Rajhans Press, Kolhapur - 416003, Maharashtra, India.
5.a) NAME: GANU SHIRISH MADHAV
b) NATIONALITY: An Indian national
c) ADDRESS: Plot no 1, Manmohan Housing Society, Karvenagar, Pune, 411052,
Maharashtra, India.
3. PREAMBLE TO THE DESCRIPTION
COMPLETE
The following specification particularly describes the invention and the manner in which it is to be performed.

FIELD OF INVENTION:
The invention relates to a system for biogas production. More particularly it relates to equipment for dual phase anaerobic process of biogas production.
GLOSSARY:
Biomethanation:
Biomethanation is the formation of methane, a metabolic byproduct in anoxic conditions by microbes known as methanogens by anaerobic respiration.
Biomass:
Biomass is defined as the total amount of living material in a given habitat. Herein biomass is referred to as any carbonaceous organic substrate including, but not limited to, sewage sludge, forestry waste, food waste, agricultural waste, municipal waste, agricultural feeds, agricultural produce, forest produce, and the like.
Digested material:
Herein defined as the material, which is left after degradation of the available biomass by biomethanation process
Dual- phase process of biomethanation:
Herein defined as a biomethanation process in solid phase / state as a first step and biomethanation process in liquid phase / state as the second step
Feed:
Herein defined as the mix of biomass and seed inoculum of anaerobic microorganisms required to initiate the anaerobic digestion process

Methane digester:
Methane digester is an anaerobic (low or no oxygen) chamber, which facilitates the breakdown of biomass (substrate) by anaerobic bacteria with the release of methane and as a byproduct of their metabolism other gases, including ammonia, nitrogen, hydrogen sulfide, and carbon dioxide, water vapour, etc.
Liquid state/Wet methane digester:
Herein defined as a methane digester wherein the leachates from solid state methane digester, fresh culture and feed are in liquid state, i.e. in a flowable form.
Liquid state methane fermentation:
Herein defined as a methane digester wherein the contents of the digester are in a flowable form i.e. in liquid state.
Solid state anaerobic fermentation:
A process of anaerobic fermentation wherein the contents of the digester are in a non pump-able/ non flowable form i.e. dry form (partially unsaturated solid form) it may have considerably high percentage of liquid absorbed in the solid mass.
Solid state / dry methane digester:
Herein defined as a methane digester wherein culture, feed is in a moist but solid state i.e. the
contents of the digester are in a non pump-able or non flowable form.
BACKGROUND OF THE INVENTION:
Anaerobic digestion is the process in which the micro- organisms break down the organic materials in an enclosed vessel with lack of oxygen supply. This procedure helps in treating the waste and produce biogas. The container in which this process takes place is termed as anaerobic digester / anaerobic reactor. The digester decomposes (or "digests") the organic waste in an oxygen free environment wherein the microbes in the waste generate methane and carbon

dioxide along with other gases. This digester gas (which often comes contaminated with hydrogen sulfide) is then burnt as fuel to produce heat as also to make electricity. Digesters are commonly used for sewage sludge at sewage treatment plants and for animal waste (dung) on farms. Digested manure is applied as soil conditioner. Anaerobic digesters are of various types. The following is a partial list of different types of anaerobic digesters. These processes and systems harness anaerobic digestion for purposes such as waste disposal/ treatment and biogas generation.
Examples include:
• Anaerobic activated sludge process
• Anaerobic clarigester
• Anaerobic migrating blanket reactor
• Batch system anaerobic digester
• Continuous stirred-tank reactor (CSTR)
• Expanded granular sludge bed digestion (EGSB)
• Hybrid reactor
• Imhoff tank
• One-stage anaerobic digester
• Submerged media anaerobic reactor
• Sintex Digester
• Two-stage anaerobic digester
• Upflow anaerobic sludge blanket digestion (UASB)
• Upflow and down-flow anaerobic attached growth.
The above mentioned digesters vary in their designing and follow different route for production of biogas by degrading the feed / substrate which is particularly in liquid (flowable) state. Herein is an effort for conversion of biomass into biogas by introducing dry digester. Degradation of biomass takes place by following both solid and liquid stages and in two or more different digesters.

Some of the available technologies for utilizing digesters and producing biogas from them are cited as follows:
PRIOR ART:
• Patent Application (WO/2007/096392) discloses "BIOREACTOR FOR METHANIZATION OF BIOMASS HAVING A HIGH SOLIDS FRACTION."
Abstract: A bioreactor having improved gas yield is specified, in which the necessary residence time of the biomass in the rotting vessel is decreased. On fermentation of dry, that is to say non-pumpable, biomass, owing to the moisture present in the biomass, percolating juices, what is termed percolate, are formed and are taken off via a drainage system and, if appropriate, is recirculated from the top onto the biomass to be fermented. It has now turned out that the biogas yield is significantly increased, in the region between 10% and 40%, when the resultant percolate is not taken off immediately via the drainage system, but is backed up in the rotting vessel up to a certain level. This is achieved in terms of the device in such a manner that the rotting vessel is designed so as to be liquid-tight, that is to say even the flap for charging and unloading the rotting vessel has to be made in a liquid-tight manner, and also must be constructed in a correspondingly stable manner in order to withstand the resultant liquid pressure. By means of the combination of the existing percolate drainage system with a percolate control unit it is possible to set the liquid level of the percolate in the biomass to be fermented and to control it in such a manner that the biogas production rate or the biogas yields is maximal.
Limitation: The patent claims that the percolate from the first digester is stored in a rotting vessel which if desirable is recirculated from the top onto the biomass. No attempt has been made to convert the rotting vessel into another methane generating digester. The present invention introduces a solid state methane digester to generate biogas with minimum hydraulic retention time of 18- 20 days.
• United States Patent Application No 7,144,507 discloses "DRY CYCLE
ANAEROBIC DIGESTER".

Abstract: The present invention provides a digester for handling waste or contaminated materials. A process and an apparatus for processing are disclosed. A Dry Cycle Anaerobic Digester (DCAD) uses tanks to perform aerobic and anaerobic digestion to eliminate the waste, while producing little or no sludge.
Limitation: The invention claims handling waste in liquid form storing it for a defined period and thereby emptying the tanks and than drying the tank. This does not have any effect on digester size. As also the process is aerobic and anaerobic, whereas the present invention describes a dual- phase anaerobic process in solid state.
• Patent Application No WO/2007/075762 discloses "ANAEROBIC PHASED
SOLIDS DIGESTER FOR BIOGAS PRODUCTION FROM ORGANIC SOLID
WASTES."
Abstract: The present invention provides methods for the generation of methane by a two phase anaerobic phase system (APS) digestion of organic substrates. Also provided is a device for practicing the methods of the invention. The APS-digester system is a space-efficient, high-rate solids digestion system. The APS-digester system consists of one or more hydrolysis reactors, a buffer tank and one biogasification reactor.
Limitations: This invention describes biogas production in two stages: hydrolysis and methanization.In the first hydrolytic reactor, volatile fatty acids are produced, which are converted into biogas in the second biogasification reactor. The present invention defines biogas production in both the phases i.e. in solid state and liquid state and from both the methanogenic reactors.
• Patent application No: WO/2009/073902 discloses: "BIOMASS DIGESTER
SYSTEM & PROCESS."
Abstract: A biomass digester system for generating biogas includes a battery of flexible, elongate digesters at least one common biogas accumulator, connection means for connecting the digesters in gaseous communication with the accumulator and valve means fitted to the

connection means, for adjusting flow of the biogas through the connection means thereby to permit a digester to be disconnected from the accumulator and taken offline. Each digester may include a flexible bag adapted to withstand pressure of the order of two bars, an inlet for biomass and an outlet for biogas. Also provided is a process for producing biogas from biomass.
Limitations: The invention discloses a process of biogas production by utilizing biomass which is in slurry form or in liquid form, thereby limiting its scope of biogas production for solid substrates.
• Patent Application No: WO/2008/016999 discloses "FERMENTATION SYSTEM
HAVING STRAINER ASSEMBLY."
Abstract: A fermentation system for production of biogas from solid organic material, the system including at least one fermentation reactor. The fermentation reactor includes a vessel for housing a feed mixture having liquid and solid particles and an outlet port, a strainer assembly at the outlet port for filtering processed feed mixture from the vessel, and a biogasification reactor in fluid communication with another fermentation reactor, the other fermentation reactor configured to produce a biomethane. The strainer assembly further includes a mixture driving member positioned in the strainer body adjacent the drain opening , the mixture driving member having a driving surface configured to receive the liquid passing through the filter member. The driving surface engages the filter member such that solid particles are driven from a surface of the filter member when the driving member is activated. A method of continuously producing a biogas and servicing a strainer assembly for a hydrolysis reactor are disclosed.
Limitations: The process claimed herein is biogas production from solid organic material, in two steps of hydrolysis and methanogenesis and in two different digesters. Herein possibilities of digestate accumulation are high since the solid and liquid fractions are separated by means of filter, which in due course may get choked and thus interfering with the methanogenic stage.
• Patent Application no: WO/2002/100784 discloses an "ANAEROBIC DIGESTION
APPARATUS, METHODS FOR ANAEROBIC DIGESTION AND FOR MINIMIZING THE USE OF INHIBITORY POLYMERS IN DIGESTION."

Abstract: The invention includes an anaerobic solids digestion apparatus comprising a digester, at least one draft tube, at least one nozzle and a biogas source a method for digesting a waste stream in an anaerobic solids digestion apparatus comprises feeding a waste stream to a digester, reacting the anaerobically biodegradable material in the waste stream with anaerobic bacteria in the digester , introducing a mixed liquor into the digester and mixing the mixed liquor, and a method for minimizing the use of inhibitory polymers by concurrently digesting and concentrating the mixed liquor in the digester.
Limitations: The above inventions describe biomethanation process for biomass in liquid state and heterogeneous biomass solution with total suspended polids in the range of 0.5 to 12 percentage. However, the above invented system are not suitable for solid biomass; especially biomass like water hyacinth, paper waste, bagasse, biomass, and agro waste etc., which tend to float on the surface in the liquid solution state because of their low density in dry state or due to buoyancy attended by the adhering gas bubbles and subsequently become inaccessible to the microorganisms.
• Patent Application No: CN 101717793 titled "Technological method of parallel-connected sequencing batch dry type anaerobic digestion treatment of organic solid waste."
Abstract: The invention discloses a technological method of the parallel- connected sequencing batch dry type anaerobic digestion treatment of organic solid waste, belonging to the technical filed of environmental protection. Four sequencing batch type anaerobic digestion reaction pots are in parallel connected; each sequencing batch type anaerobic digestion reaction pots (A,B,C,D) respectively correspond to four biogas slurry collection pools (a,b,c,d); and each biogas slurry collection pool is connected with a submerged pump and a valve. Biogas slurry enters a main biogas slurry regurgitated pipe through the submerged pump, enters the corresponding main biogas slurry regurgitated pipe by opening the corresponding valve according to the digestion process of materials and is uniformly spread to the materials through a spraying device. The invention forms difference technological conditions to furthest activity of two anaerobic nitrifying bacteria to acceleration the degradation of the organic solid waste and

enhance the aerogenesis speed by utilizing the difference of optimal growing environments of acid producing bacteria and methanogens through the recharge of the biogas slurry.
Limitations: The slurry collection pools for the above invention are individually connected to the digester and are just utilized for collection of slurry and does not propose any other function
BRIEF DESCRIPTION OF DRAWINGS:
The present invention will be more fully understood and appreciated by reading the following detailed description in conjunction with the accompanying drawings, in which:
Figure 1 is the flow chart of the system of dual phase digestion process using the solid state digester according to an embodiment of the present invention;
Figure 2 illustrates front view of solid state methane digester used for biogas production system according to an embodiment;
Figure 3 illustrates top view of the solid state methane digester assembly;
Figure 4 illustrates schematic cross sectional view on both lines A-A of the solid state methane digester;
Figure 5 illustrates schematic front view of solid state methane digester;
Figure 6 illustrates sectional view of solid state methane digester with flexible gas holder according to an embodiment;
Figure 7 illustrates top view of solid state methane digester with flexible gas holder according to an embodiment; and
Figure 8 illustrates schematic sectional view of solid state methane digester with flexible gas holder according to an embodiment;

Part list:
1- Feed Storage Tank
2- Solid State Methane Digester
3- Reaction chamber of solid state methane digester
4- A vertical perforated container
5- Liquid State Methane Digester
6- Reaction chamber of liquid state methane digester
7- Biogas Storage Vessel
8- Inlet port for collecting percolate
9- Outlet port for recycling the percolate
10- Culture Preparation Tank 11-Filtration Unit

12- Manure Preparation Unit
13- Spray recirculation system
14- Solid handling pump
15- Control valves/ Regulators
16- Insulated Feed Inlet port
17- Leachate outlet port connected to the liquid digester
18- Digested material outlet port 19-Gas outlet port
20- Gas holder of solid state methane digester
DISCLOSURE OF THE INVENTION:
The present invention is directed towards a system of biogas production from solid biomass using combined dual phase anaerobic digestion process. It comprises plurality of solid state digesters and a liquid state digester. The number of solid digester varies depending upon the nature of biomass and time required for its complete digestion.
An object of the present invention is to provide effective biogas production system to generate biogas from solid biomass by using combined dual phase anaerobic digestion.

An object of the present invention is to utilize the percolate / leachates generated during the solid state digestion to produce biogas.
An object of the present invention is to achieve complete digestion of solid biomass by enabling anaerobic microorganism continuously accessible to the biomass.
A further object of the present invention is to reduce the size of digester as compared to the commercially available existing anaerobic digesters.
A further object of the present invention is to reduce the moving parts involved in the system for biogas production and lower the maintenance cost of the system.
A still further object of the present invention is to generate maximum energy by producing biogas through waste with minimum natural resources like water; electricity etc and can handle heterogeneous waste in the same digester scheme.
SUMMARY OF THE INVENTION:
The present invention encompasses a system for generation of biogas in a combined solid and liquid dual phase anaerobic process. The system comprises two or more methane digesters (2), (5), gas collecting unit (19), culture preparation tank (10), filtration unit (11) and manure preparation unit (12). The solid state methane digester (2), comprise a vertical perforated displaceable container (4) placed to fit proximally inside the solid state methane digester(2), a gas sealed feed inlet port (16), spray recirculation system (13), leachate outlet port (17) and digestate material outlet port (18). The flow of the leachates is controlled by control valves/ regulators (15) or any other appropriate flow control mechanism so as to maintain the liquid volume in the solid state methane digester(2) at a substantially constant volume. The solid state methane digester (2) has a conduit / outlet i.e. leachate outlet port (17) in fluid communication with the liquid state methane digester (5). The leachates produced in the solid state methane digester (2) are channeled into liquid state methane digester (5) for further extraction of biogas from leachates through leachate outlet port (17), The feed may preferably be introduced into the perforated container (4) proximally placed inside the solid state methane digester (2). Biomass

includes any carbonaceous organic substrate including, but not limited to, sewage sludge, forestry waste, food waste, agricultural waste, municipal waste, agricultural feeds, agricultural produce, forest produce, and the like.
The solid digestate collected from the digested material outlet port (18) of the solid state methane digester (2) is channeled into the culture preparation unit (10) which in turn is connected to the solid state methane digester (2) thereby treating the mixture as feed for further extraction of biogas. The undigested material from the culture preparation unit (10) is filtered through appropriate filtration process (11) and apparatus and further treated and utilized as manure (12).
The present invention envisages an overall reduction in the size of digesters and in the retention time biomethanation as compared to the conventional digesters like the Continuously Stirred Tank Reactor (CSTR). The system makes possible optimum biogas generation from fresh feed / biomass, undigested digestate and leachates produced during the biomethanation process, which otherwise is expelled out directly from the biomethanation process. The system simultaneously generates optimum biogas following two phases and in two different digesters and producing feed and manure. The desired temperature, in the methane digesters, preferably temperature of about 30 degree C to about 40 degree C are maintained by means of spray recirculation system and heat exchanger. The dimensions and material of construction for the methane digesters (2), (5) and perforating container (4) vary depending on the quantity and nature of the biomass used in the said biomethanation process. The methane rich gas generated is collected in a gas collecting assembly (19). The resultant produce i.e. methane and carbon dioxide (CO2) may be used for cooking purposes or generating electricity or as vehicle fuel, etc., either as it is or after cleaning and / or compressing to higher pressures. Due to the simple nature of the system and minimal moving parts, parasitic energy consumption is extremely low. This leaves a considerable amount of energy available for export to either commercial users or the grid. The process produced minimum or zero scum, thereby increasing efficiency of biogas generation.
Other features, advantages, and objects of the present invention will become more apparent and be more readily understood from the following detailed description, which should be read in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS:
The present invention is best understood by the description set forth herein. To achieve the foregoing objects and in accordance with the purpose of the invention, and to overcome the problems and shortcomings associated with prior art, a variety of embodiments are described. However, those skilled in the art will readily appreciate that the detailed description given herein is for explanatory purposes and may be embodied in various forms as the invention extends beyond these limited embodiments. 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.
Embodiments of the invention are discussed below with reference to Figure 1. In a preferred embodiment, the process of biomethanation comprises two or more methane digesters (2), (5), gas collecting unit (19), culture preparation tank (10), filtration unit (11) and manure preparation unit (12). The solid state methane digester (2) comprising a series of displaceable perforated structure (4), spray recirculation system (13), leachate outlet port (17) is in fluid communication with the liquid state methane digester (5), digested material outlet port (18) which is in communication with the culture preparation tank (10).
In the above said embodiment, the digester (2) is cylindrical mild steel container with a fixed mild steel gas holder (20) containing series of displaceable vertical perforated structure (4) of mild steel. The feed / biomass and substrate specific seed inoculum of anaerobic microorganisms is introduced into the solid state methane digesting tank (2) from the feed storage tank (1). The biomass is passed into the reaction chamber (3) for a stipulated period of time (About 18 to 20 days) required for anaerobic digestion of the feed. The period for degradation of biomass to produce biogas is variable, which depends on the retention time of the substrate used. Biomethanation reaction takes places inside the digester (2) producing biogas, leachates and solid digestate. Biogas generated after degradation of the feed is collected in fixed gas holder (20) surrounded by water jacket column (16). The biogas generated from the methane digesters

(2), (5) is further collected in a common gas collecting unit (19). The biomethanation process produces leachates and solid digestate simultaneously in the solid state methane digester (2).
The solid state methane digester (2) has a conduit /outlet arranged (18) at the extreme lower end of the digesting tank for discharging sludge/ solid digestate from the digesting tank, which is in communication with the culture preparation tank (10). The leachates produced are carried to the liquid state methane digester (5) through leachate outlet port (17). Both the outlets (17), (18) are placed at the extreme bottom end of the solid state methane digester (2). The leachates produced are again introduced into the solid state methane digester (2) by spray recirculation system (13) through liquid state methane digester (5). The spray recirculation system (13) is in fluid communication with a port situated at the extreme bottom region of liquid state methane digester (9) and suspended internally in the head space of solid state methane digester. The recirculation system (13) operates intermittently by spraying the leachates, preferably up to about 10 minutes per hour. This system (13) controls and enhances the overall degradation of solid biomass to generate biogas and produce leachates and solid digestate.
The liquid state methane digester (5) consists of a reaction chamber (6) and a flexible biogas collecting vessel preferably a dome shaped (7) for extraction of biogas generated from solid state methane digester (2) and liquid state methane digester (5). The biogas collecting vessel (7) is mounted in the head region of the liquid state methane digester (5), which is movable and displaces gas by vertically upward movement. The liquid state methane digester (5) has provisions for collecting the percolate at the lower region of the digester (8) and an outlet at another lower end (9) for recycling the percolate into the solid state methane digester (2) by means of spray pumps and dispensers. The sludge produced is further filtered through a filtration unit (11) which may be sand filter or any other appropriate filter unit. The filtered sludge is finally dispatched for manure preparation into the manure preparation unit (12) manually. The number of solid state methane digesters (2) varies with respect to biomass / substrate used for biogas generation. The lechates from the liquid state methane digester (5) and the sludge produced from the solid state methane digester (2) is directed towards culture preparation unit (10). The culture prepared from the culture preparation unit (10) with addition of fresh feed is

utilized further for biogas generation. The culture preparation unit (10) is connected in series with the filtration unit (11) and the feed storage tank (1). The spray recirculation system (13) maintains the desired temperature conditions preferably about 30-40 degree Celsius inside the solid state methane digester (2), which in turn is controlled by solid handling pump (14). The reactor size is optimized taking into consideration the microbial population and retention time required for digestion. Introduction of the liquid state methane digester optimizes biogas generation from the non digested slurry which otherwise is disposed off.
The said non digested material prepared in the said culture preparation unit (10) is introduced partly in the said solid state methane digester (2) and partly treated for manure preparation. The said non digested material is introduced onto filtration tank: (10) for draining excess water / liquid present in the solid digested material. The said non digested material further may be subjected for composting to manure (12) in order to achieve the desired quality of carbon to nitrogen ratio.
Valves and regulators (15) or any other appropriate flow control mechanism are introduced to control the flow of leachates/ slurry. The culture preparation tank (10) is than regularly fed with the substrate and portion of the solid digested material from the solid state methane digester (2). The gas generated from the digesters (2), (5) is collected in storage vessel (19). The mixture produced in the said culture preparation tank (10) is utilized as feed for further subsequent biogas generation.
Embodiments of the invention are discussed below with reference to Figure 5. In an exemplary embodiment a single perforated container (4) is sized to fit proximally inside the cuboid solid state methane digesting tank (2), with the sprinkler (13) placed in the head region of the solid state methane digester. The perforated container (4) is filled up with feed. The leachates produced through the perforated container (4) during biomethanation process are channeled into liquid state methane digester (5) through digested material outlet port (17) created at one extreme bottom end of the solid state methane digester (2). The liquid state methane digester (5) is in fluid communication with the solid state methane digester (2). The feed / biomass from the feed

storage tank (1) and substrate specific culture is introduced into the perforated container/unit (4) placed inside the solid state methane digesting tank (2).
The perforated unit structure/container (4) is a rectangular structure, with the sprinkling arrangement (13) suspended in the head region of the perforated rectangular structure unit (4). The gas holder (20) is placed enveloping the perforated rectangular structure unit (4) and sealing the holder by water jacket (16) thereby creating anaerobic conditions inside the solid sate methane digester (2) and the displaceable perforated structure unit (4). The gas is generated in the gas holder of solid state methane digester (20) and in the gas holder liquid state methane digester (7). The solid digestate is let out in culture preparation unit (10) through digestate material outlet port (18) situated at another extreme bottom end of the solid state methane digester (2). The solid digestate is mixed along with fresh feed to prepare feed for the biomethanation process. The prepared feed is introduced into solid state methane digester (2) for further degradation of the biomass to produce biogas. The culture unit (10) in turn is connected in series to the filtration unit (11) which is in communication with the manure preparation unit (12) to prepare and be used as manure. The gas generated from both the digesters (2), (5) is collected in a common gas collecting unit (19). The gas generated i.e. methane and carbon dioxide (CO2) may be used for cooking purposes or generating electricity or as vehicle fuel, etc., either as is or after cleaning and / or compressing to higher pressures. This mixture can also be converted to purified methane and compressed to replace CNG for various applications. The digester shape varies but not limited to square, rectangle, oval and/or of any geometric shapes.
Embodiments of the invention are discussed below with reference to Figure 8. In another preferred embodiment, the gas holder (20) is flexible in nature and placed enveloping the perforated container (4). The gas holder (20) is sealed with water jacket (16) covering the perforated container (4). The sprinkler (13) suspended in the head region of the perforated container (4) and the leachates produced through the container (4) are carried into the liquid state methane digester (5) through leachate outlet port (17). The net cumulative result is optimum biogas production from plurality of methane digesters in the gas collecting assembly (19).

The displaceable percolating container, methane digesters and gas holder vary with respect to its dimensions and material of construction subject to the biomass/ feed used for biomethanation process. The shape of the methane digesters used may be of any geometric shape as like but not limited to rectangle, square, cylindrical and/ or cuboid. The niaterial of construction of the solid state methane digester varies depending on the nature of biomass used for the biomethanation process. The material used for construction of the digester find other equipment in the above embodiments may be as like, but not limited to mild steel, poly vinyl chloride, poly propylene fiber reinforced plastic (poly FRP). The gas holder may be ()f fixed or flexible nature with its material of construction as like, but not limited to poly vinyl chloride coated with polymer and/or mild steel, and/ or galvanized iron sheet. The displaceable perforated container varies subject to the dimensions of solid state methane digester. The dimensions of perforated container are structured and designed depending on the flow rate of leachate recirculation. The material for the perforated container used may be as like filter cloth, mild steel mesh/ screen.
While considerable emphasis has been placed herein on the specific steps of the preferred process and components of the preferred embodiment, and many details have been set forth for purpose of illustration, it will be appreciated that many alterations can be made and that many modifications can be made in the preferred embodiment without departing from the principles of the invention. These and other changes in the preferred embodiment as well as other embodiments of the inventions will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.
ADVANTAGES OF THE PRESENT INVENTION:
The present invention reduces the size of digesters drastically which depends on the hydraulic retention time of biomethanation process.
The present invention makes possible maximum biogas extraction and minimum sludge production.

The present invention reduces the moving parts involved in the system for biogas production thereby lowers the maintenance cost of the system.
The present invention introduces a number of digesters for biogas production thereby minimizing the possibilities of failure of biogas plant and optimum biogas production.
The present invention also minimizes use of fresh water required to carry out the process of digestion.

CLAIMS
We claim;
1) A system following combined dual anaerobic process for biomethanation comprising;
plurality of different anaerobic digesters for biogas generation in dual phase using mixed and / or multiple solid feeds as substrates.
a culture preparation tank/ unit for preparing feed from non digested feed material for the said process
a filtration unit / percolation unit for draining excess liquid from the non digested feed material
a manure preparation unit for preparing manure from the non digested feed material.
2) A system as claimed in claim 1, wherein the first or solid state methane digester comprises;
a gas collecting fixed/flexible gas holder to collect biogas generated from the reaction mixture
a reaction chamber for biomethanation process
a vertical displaceable perforated structure (tube) placed to fit proximally inside the solid state methane digester
a spray / recirculation unit connected to the other or liquid state methane digester to facilitate percolation of leachates from the feed into the digester and maintaining the required temperature for the microbial activity for biogas generation.
Control valves for controlling flow of biogas from both the digesters into a common biogas collecting unit.
a sludge handling pump to control the flow of leachates from the liquid state methane digester to the solid state methane digester.

The number of said solid state methane digester varies depending on the retention time of the biomass used for biomethanation process.
3) A system a claimed in claim 1, wherein the leachates produced during biomethanation process from solid state methane digester are channeled again onto the reaction mixture by means of spray recirculation system which is in fMid communication with the liquid state methane digester to enhance microbial degradation of substrates and increase biogas production.
4) A system as claimed in claim 1, wherein the dimensions and material of construction of the methane digesters, perforating structure and biogas holder varies with regards to nature and quantity of biomass used for biomethanatior1 process.
5) A system as claimed in claim 4, wherein the material of construction of the methane digesters used include but not limited to mild steel, polyvinyl chloride, polypropylene fiber reinforced plastic, composites, the material of construction for the perforating structure include mild steel mesh and or sheet and material of construction for gas holder include cover of polyvinyl coated polymer, mild steel, galvanized sheet, composites.
6) A system as claimed in claim 1, wherein the solid non digested feed material is collected in culture preparation unit to produce culture for the biomethanation process.
7) A system as claimed in claim 1, wherein manure is produced in manure preparation unit through the step of filtration of non digested material until desired quality of carbon to nitrogen ratio is obtained as in required for manure.
8) A system as claimed in claim 1, wherein the biomethanation process reduces the overall hydraulic retention time, depending on substrate, to 5 to 20 days required for the biomethanation process, thereby reducing the size of the biogas digester by 50 percent or more of equivalent capacity with optimum biogas generation.

9) A system as claimed in claim 1, wherein the substrates used are agro residues, like paddy straw, wheat straw, maize, Napier grass, press mud, oilcakes of castor, sal and the like.
10) A system as claimed in claim 1, wherein the system achieves digestion of solid biomass by enabling anaerobic microorganism continuously accessible to the biomass, thereby continuously generating biogas, fuel and manure with minimum effluent slurry thereby solving the problem of waste disposal and optimum biogas production.