Title of Invention	A NOVEL HIGH RATE BIOGAS PROCESS FOR VARIABLE ORGANIC FEEDSTOCK
Abstract	The subject of this patent is a novel process for high rate production of biogas from variable organic feedstocks of natural origin. The process claimed has the following advantages over existing biogas production process: The process is faster than existing biogas production processes, for the same kind of feedstock. The process can rapidly adapt to changes in feedstock. For example, the feedstock can be switched from, say, molasses to coir pith and thereafter to, say, vegetable - waste and the process will rapidly adapt, without being upset. Hence, a single installation can handle variable organic feedstock without loss of biogas production. This is important for industrial applications.The process integrates physico-chemical feedstock conversion with subsequent anaerobic fermentation steps, to produce biogas.Feedstock conversion produces easily biodegradable 'Intermediate Broth' enabling high rate anaerobic fermentation regardless of variations in primary feedstock by utilizing a microbial culture pre-adapted to 'Intermediate Broth'.

Title of Invention

A NOVEL HIGH RATE BIOGAS PROCESS FOR VARIABLE ORGANIC FEEDSTOCK

Abstract

The subject of this patent is a novel process for high rate production of biogas from variable organic feedstocks of natural origin. The process claimed has the following advantages over existing biogas production process: The process is faster than existing biogas production processes, for the same kind of feedstock. The process can rapidly adapt to changes in feedstock. For example, the feedstock can be switched from, say, molasses to coir pith and thereafter to, say, vegetable - waste and the process will rapidly adapt, without being upset. Hence, a single installation can handle variable organic feedstock without loss of biogas production. This is important for industrial applications.The process integrates physico-chemical feedstock conversion with subsequent anaerobic fermentation steps, to produce biogas.Feedstock conversion produces easily biodegradable 'Intermediate Broth' enabling high rate anaerobic fermentation regardless of variations in primary feedstock by utilizing a microbial culture pre-adapted to 'Intermediate Broth'.

Full Text	INTRODUCTION The subject of this patent is a process for production of biogas from organic feedstocks of natural origin. The innovations in this process pertain to: i. Increase in the overall speed of conversion of feedstock to biogas: This improvement is achieved by utilizing a pre-adapted bacterial culture, thus avoiding the time delay for bacterial adaptation to feedstock and also by decomposing the feedstock to a predetermined extent such that degree of feedstock decomposition is matched with the metabolic requirements of the bacterial culture, thus avoiding the time delay for bacteria to hydrolyse the feedstock. ii. Ability to handle a variety of organic feedstocks of variable quality without resulting in process upsets: This improvement is achieved by ensuring a specific degree of feedstock decomposition such that regardless of the primary feedstock, the bacterial culture is exposed only to a decomposed feedstock to which it is pre-adapted. In contrast, conventional processes are designed to handle single feedstocks with consistent feed quality and are known to go out of control if the primary feedstock quality changes significantly. UTILITY This invention would be especially useful in the conversion of natural organic biomass or solid & liquid wastes or other natural organics from domestic and industrial sources, into a valuable fuel i.e., biogas. DESCRIPTION OF THE PROCESS Organic feedstock of natural origin is the primary feedstock for this process. The feedstock could be sourced from raw biomass or processed biomass. Some examples of raw biomass are plants, vegetables, fruits, trees, foliage, crops, crop residues, forest litter, grass cuttings, flowers, seeds. The biomass could be from industrial or domestic sources. Some examples of biomass from industrial sources are byproducts, intermediates or wastes from agro-processing industries such as vegetable processing, fruit processing food processing. Sugar manufacture, Ethanol manufacture, Vinegar manufacture. Wine manufacture. Starch manufacture, Herbal products manufacture. Tea processing. Coffee processing, Sugar Beet processing, Sweet Sorghum processing, Neem fruit processing. Groundnut processing, Com processing. Soya bean processing, Rice processing, Wheat processing. Coconut and Coir processing, edible and non-edible Oilseeds processing. Rye processing, Cattlefeed manufacture. Some examples of biomass from domestic and community sources are Kitchen wastes from households, hotels or vegetable market wastes or organic municipal wastes. It is known that organic materials of natural origin are mainly made up of Carbohydrates, Proteins and Fats, apart from various essential minerals, vitamins etc. Biomass can be of various types, i.e Cellulosic, Starchy, Proteinaceous, Fatty, or contain all these categories of molecules in varying proportions. This invention can handle all these types of biomass in any combination. This is because, regardless of the type of biomass, they can all be decomposed biologically into simpler Sugars, Fatty acids, Amino acids etc. along well-known metabolic pathways (e.g Enzymatic hydrolysis, Krebs cycle, Embden Meyerhoff pathway). In nature, bacteria have the ability to decompose all types of complex natural molecules into simpler molecules as part of their metabolic activity, using intra-cellular and exo-cellular enzymes. More importantly, from the viewpoint of industrial applications, it is known that bacteria can adapt themselves to utilize different types of organic molecules. During the process of adaptation, bacterial populations learn to produce 'new' enzymes, which can break down and metabolize unfamiliar organic molecules, i.e molecules which are not normally part of their 'diet'. This process takes time, but can be accomplished under controlled conditions using standard microbiological techniques. The principle underlying this invention is the fact that all types of biomass, during the process of biological decomposition, produce common intermediates and end products, depending on whether the decomposition is aerobic, anaerobic or facultative. Thus, if different types of feedstock are first treated physico-chemically, to yield a common set of intermediate molecules and if the target bacterial populations are pre-adapted to this common set of molecules, then it is possible to achieve a faster and stable biological degradation process. The process is faster because adaptation time and hydrolysis time are substantially reduced. The process is stable, since, regardless of variations in type of feedstock, the bacteria are exposed only to the intermediate molecules, to which they are already adapted. The steps of the process are: (a) Methanogenic culture on special growth medium: The first requirement of the process is to grow a pre-adapted microbial culture, capable of producing Methane from decomposed organic feedstock. The technique of growing Methanogenic cultures is well known in microbiology. In this invention, the Methanogenic microbial culture is grown on a special growth medium, which is composed of key molecules that are produced during decomposition of various common types of biomass. This ensures that during an early stage of their evolution, the bacteria develop the ability to survive and grow in the presence of these key molecules. In this invention, these key molecules comprise Xylose, Rhannose, Arabinose, Glucose, Mannose, Galactose, Sucrose, Amino acids. Cellulose, Starch, Acetic acid. Propionic acid. Butyric acid. Formic Acid, p-Hydroxy Cinnamyl Alcohol, Coniferyl alcohol, Sinapyl alcohol, p-Coumaryl alcohol, Furfural, Hydroxymethyl furfural, 4-0-methyl-glucuronic acid, Galacturonic acid. Soya bean meal and Groundnut meal are added as good natural sources of Amino-acids and Lipids. Nitrogen and Phosphorus are essential for any biological process and these are added in the form of Urea and Phosphoric acid. The composition of the growth medium is important to get an efficient culture and this invention utilizes the following proportions of its various constituents: Glucose, Xylose, Acetic acid, to be present at a concentration between about 5% by weight and about 25% by weight and each of the members of the group: Rhannose, Arabinose, Mannose, Galactose, Sucrose, Cellulose powder. Starch powder. Propionic acid. Butyric acid. Soya bean meal. Groundnut meal is present at a concentration between about 1% by weight and about 10% by weight in the microbial culture growth medium; each of the members of the group: Formic Acid, Phosphoric acid. Urea are present at a concentration between about 0.5% by weight and about 3 % by weight and each of the members of the group: p-Hydroxy Ciimamyl Alcohol, Coniferyl alcohol, Sinapyl alcohol, p-Coumaryl alcohol, Furfural, Hydroxymethyl furfural, 4-0-methyl-glucuronic acid, Galacturonic acid is present at a concentration between about 0.0001% by weight and about 0.3 % by weight of the microbial culture growth medium. Further, withdrawn fluid from main anaerobic digestion unit can also be added, the concentration being between about 5 % by weight to about 75% by weight of the microbial culture growth medium. This ensures that the species which evolve and grow in the medium would be representative of the populations which survive in the large scale digester. Fresh cow-dung can also be added, if anaerobic digester fluid is not available. (b) A Feedstock conversion step: This step uses known methods of applying heat and pressure and is designed to decompose the feedstock to a pre-determined extent. The intention of this step is to decompose the feedstock to an extent that produces smaller molecules, to which the bacteria are pre-adapted. In other words, this step makes sure that the processed feedstock and the bacterial culture are 'made for each other', and hence the main anaerobic digestion can start immediately without delay caused by bacterial adaptation. In this invention, the feedstock conversion step of the process shall be conducted by applying heat and pressure to the feedstock in the presence of Water at a Neutral pH. In the case of solid feedstock, the size of the solids is first reduced to less than 50 millimetres, before subjecting the feedstock to heat and pressure. Size reduction is required to enable efficient physico-chemical decomposition. In the case of fluid organic feedstock, the size reduction step is not necessary and the fluid feedstock shall be directly subjected to heat and pressure in the presence of Water, at neutral pH. In this invention, the temperature during heating can be maintained anywhere between about 40 Degrees Centigrade to about 250 Degrees Centigrade, depending on the nature of the feedstock. Similarly, the Pressure during heating can be maintained anywhere between about 1 KiloPascals (gauge) to about 25000 KiloPascals (gauge).Water and neutral pH are necessary in this process. An analogy with 'cooking vegetables in a pressure cooker' is appropriate at this point, to explain to the layman the purpose of this step; this is because a 'pressure cooker' utilizes heat and mild pressure, which along with Water (and steam), transform vegetables in the cooker into more easily digestible forms, for human consumption. In a similar way, the feedstock conversion step aims to utilize high pressure, temperature and Water to achieve the desired decomposition of biomass. Obviously, it is likely that at higher temperatures and corresponding pressures. Water would boil off and become steam or else it may even reach a temperature and pressure that is beyond the thermodynamic Critical point of Water, when it ceases to be either a liquid or a vapour. Thus in such cases, the organic feedstock would actually be subjected to heat and pressure by high pressure steam in direct contact with the organic feedstock, or by super-critical Water (i.e Water beyond its Critical point) in direct contact with the organic feedstock. The actual choice of process conditions for the feedstock conversion step depends on the type of feedstock. Biomass can be of various types, i.e Cellulosic, Starchy, Proteinaceous, Fatty, or contain all these categories of molecules in varying proportions. On this basis, the various types of feedstock can be divided into the following categories: • High Cellulose feedstock, wherein the composition of the organic feedstock is predominantly comprised of Cellulose compounds. • High Sugar feedstock, wherein the composition of the organic feedstock is predominantly comprised of Sugars. • High Starch feedstock, wherein the composition of the organic feedstock is predominantly comprised of Starch compounds. • High Protein feedstock, wherein the composition of the organic feedstock is predominantly comprised of Protein compounds. • High Fat feedstock, wherein the composition of the organic feedstock is predominantly comprised of Lipid compounds. • Furthermore, the organic feedstock can be a physical mixture, in any proportion by weight, of High Cellulose feedstock, High Sugar feedstock. High Starch feedstock. High Protein feedstock and High Fat feedstock. This invention specifies only the range of applicable process conditions and the specified process steps can be conducted in any machinery suitable for the purpose. Some examples of the type of equipment that can be used to subject the organic feedstock to heat by indirect heating are: heat exchangers, vessels, fired heaters, water-bath heater, electrical heater, solar heater. Similarly, pressurising equipment such as pumps or various types of presses can be used to directly pressurize the feedstock or, pressurized fluids can be used to create the necessary conditions of high pressure. The essence of this step is that the degree of feedstock decomposition must be controlled to ensure that key molecules, which the pre-adapted bacteria can readily consume, become available in sufficient quantity. This is ensured by checking the following points: • Monitoring BOD5 (5 day Biochemical Oxygen Demand) in the liquid phase. • Monitoring the presence of key molecules, which would indicate that decomposition is proceeding in the right direction, to the required extent. The decomposed feedstock, is then adjusted to neutral pH and blended thoroughly with recycle slurry from main anaerobic digester, so that the ensuing broth is in a similar state to material already successfully undergoing anaerobic digestion. The homogeneous suspension, which is ready to be fed to the bacteria, is termed 'Intermediate Broth'. (c ) An inoculum development step: The intent of this step is to multiply the bacterial culture till sufficient quantity of viable bacteria are available to seed the main digester. A small part of the 'Intermediate Broth' is used for the inoculum development while the balance goes to anaerobic digesters. A portion of the Intermediate Broth from step (b) is mixed under anaerobic conditions and controlled conditions of temperature, pressure and pH, with the pre-adapted anaerobic bacterial culture from step (a) and incubated under strict anaerobic conditions and controlled conditions of temperature, pressure and pH till the produced gas composition is consistently at least 55% by volume of Methane, after which this Methane producing Broth is considered to be sufficiently adapted and therefore hereinafter termed 'adapted inoculum' and shall be used as inoculum to start and sustain the main anaerobic digestion. The pH in the inoculum development digester is kept at about pH 7.0-8.0 and the temperature between about 30 degrees Centigrade to about 70 degrees centigrade; the pressure is maintained at between about 0.1 KiloPascals (gauge) to about 3500 KiloPascals (gauge). (d) The main anaerobic digestion step: The main anaerobic digesters are 'seeded' with adapted inoculum from the inoculum development section. This involves mixing the 'adapted inoculum' from step (c ) with the remaining portion of Intermediate Broth from step (b) under anaerobic conditions and transferring to the main digestion unit. The main anaerobic digestion unit comprises a single stage of anaerobic digestion, in which Acetogenic and Methanogenic reactions occur within the same anaerobic digestion stage, under controlled conditions of temperature, pressure, pH and sufficient mixing, with an average retention time of at least 6 hours for the digesting mass. The produced bio-gas has to be continuously withdrawn, to ensure that excessive partial-pressure of Hydrogen within the digesting mass does not inhibit the reaction. The pH in the main anaerobic digestion unit is kept at about pH 7.0-8.0, using a member of the group: Sodium Hydroxide, Calcium Hydroxide, Potassium hydroxide; Ammonia, Ammonium Hydroxide, Sodium Carbonate, Sodium Bi-Carbonate. The temperature within the main anaerobic digester unit is maintained at between about 30 degrees Centigrade to about 70 degrees centigrade and the pressure within the main anaerobic digester unit is maintained at between about 0.1 KiloPascals (gauge) to about 3500 KiloPascals (gauge). (e) Digested product withdrawal and fresh feed step: Controlled withdrawal of the liquid and solid contents from the said main anaerobic digestion unit can be done after at least 6 hours of retention time in the main anaerobic digestion unit and replacing the withdrawn volume with fresh slurry from step (d), ensuring that anaerobic conditions are maintained in the said digestion unit during slurry withdrawal and filling. A portion of the withdrawn fluid from the said digestion unit is recycled to form a constituent of the mixture described in step (b). The retention time of the digesting mass in the main single stage of anaerobic digestion is controlled at between about 6 hours and about 480 hours, depending on the feedstock and the desired product quality. WORKING PRINCIPLE This invention is a process that combines a physico-chemical feedstock conversion step with a microbial fermentation step to obtain a high rate, flexible process for converting organic feedstocks to biogas. The physico-chemical nature of the feedstock conversion step enables the processing of varying feedstocks to yield 'Intermediate Broth'. This step is based on the proven principle that all natural organic materials can be decomposed by physico-chemical means to smaller, biodegradable molecules. The resulting mixture of biodegradable compounds along with inerts, is termed 'Intermediate Broth'. The physico-chemical step imparts speed and flexibility to the overall process. The physico-chemical step is conducted by applying heat and pressure to the feedstock in the presence of Water at a Neutral pH, such that the feedstock decomposes to a pre-determined extent. In the case of solid feedstock the size of the solids are first reduced to less than 50 millimetres, before subjecting the feedstock to heat and pressure. The essence of this invention is that the degree of feedstock decomposition must be controlled to ensure that molecules which the pre-adapted bacteria can readily consume become available in sufficient quantity. This is ensured by checking the following points: • Monitoring BOD5 (5 day Biochemical Oxygen Demand) of the liquid during feedstock decomposition, to ensure that the concentration of organic molecules corresponds to a BOD5 value of at least 1000 milligrams per litre. The COD (Chemical Oxygen Demand) can be monitored instead of BOD5 provided a validated conversion formula is used to calculate the equivalent BOD5. • Analysing the liquid phase during feedstock decomposition to monitor concentration of some of the key molecules readily metabolizable by the pre-adapted bacteria, such as any of Glucose, Rhannose, Xylose, Arabinose, Galactose, Sucrose, Acetic acid. Propionic acid and Butyric acid. Once the above decomposition is completed satisfactorily, the resulting Broth is further pH adjusted (if necessary) and nutrients such as Urea and Phosphate added and the mixture is termed Intermediate Broth. Anaerobic fermentation of the 'Intermediate Broth' then produces biogas. This step utilizes a special microbial culture that can adapt itself quickly to changes in composition of the 'Intermediate Broth'. The feedstock conversion step is designed to ensure that the variations in 'Intermediate Broth' composition remain in a fairly narrow band, well within the adaptive capabilities of the microbial culture. Thus, the microbial culture is exposed only to permissible variations in the 'Intermediate Broth' and not to drastic variations that can occur in the primary feedstock. This ensures that the microbial metabolic processes are not upset and the biogas production proceeds smoothly. PRIOR ART The science of anaerobic fermentation has been well understood for more than a century. Similarly, physico-chemical transformation of natural organics into fermentable intermediates is also well known. However, combination of physico-chemical processes with a subsequent microbial fermentation step has been reported in detail only for Ethanol manufacture and some aerobic fermentation products from materials like wood, com cob, etc. In these processes, wood and other organic materials were converted to fermentable sugars and acids which were then converted to Ethanol by Yeast. This technology is reported to have been popular during the World War years, to produce fuel grade Ethanol. In U.S Pat. No. 6,059,972 to Mahrer, which claims an apparatus for anaerobic digestion of Kitchen Wastes, the process by which the disclosed apparatus works comprises mechanical grinding of Kitchen Waste before anaerobic digestion. The process disclosed does not include the decomposition of feedstock prior to anaerobic digestion by applying heat and pressure in the presence of Water at a Neutral pH or by any other physico-chemical means. The process disclosed does not include the use of pre-adapted bacteria, to handle feedstock quality variations and to speed up the digestion process. In fact, in the narrative description of the Patent, it is stated that 'Stability is indeed an essential condition for maintaining the biological process for transforming the materials'. This would indicate that the process is not designed to handle significant variations in feedstock quality. The process also does not disclose any capability to handle feedstock other than Kitchen Waste. For example it is not expected to handle a high Cellulosic feedstock such as Coir pith or Bagasse. Thus the invention by Mahrer is designed for a specific type of feedstock and cannot handle significant variations in feedstock quality and cannot handle a wide variety of organic feedstock. It is precisely these issues which are now claimed to be resolved in the process of this invention, in addition to increasing the overall speed of the conversion to biogas by using the innovation of physico-chemical feedstock conversion and pre-adaptation of bacteria. In U.S Pat. No. 4,750,454 to Santina and Chatterjee, which claims a Manure Digester and power generating system, the system is designed to work only with manure. Such systems are very well known, for example, the numerous Gobar Gas plants in India which handle Cow or Buffalo manure. The Manure digestion process is different from a process that directly handles biomass, since manure is formed from edible biomass that has already been well digested in the digestive system of animals. The manure digester cannot handle the kind of variable organic feedstock that is the subject of this invention. Thus, in the survey of prior art, there is no report of a similar process that utilizes heat and pressure in the presence of Water at Neutral pH to decompose the feedstock prior to digestion and which utilizes a pre-adapted bacterial culture that produces biogas in a single stage of anaerobic digestion. Biogas is approximately 60% Methane and 40% Carbondioxide by volume. Biogas fermentations are quite difficult when compared to Ethanol fermentation. The anaerobic bacteria which produce biogas are extremely slow- growing and sensitive creatures and are easily upset by changes in medium composition. This is why a Microbial culture that is adapted to one feedstock does not work satisfactorily with another. Therefore, this invention, which claims a High Rate Process that links a physico-chemical decomposition step to a succeeding anaerobic step to produce biogas and is capable of handling wide variations in feedstock quality with faster production of biogas, is an original invention. ADVANTAGES OF THE PROCESS OF THIS INVENTION The process of this invention has the following advantages over other known biogas production processes existing at this time: 1. Speed is an advantage of the process of this invention over conventional processes. The process of this invention does not rely upon microbes to hydrolyse complex organics into simpler intermediates and utilizes heat and pressure along with Neutral pH Water to achieve speedy decomposition of feedstock. In contrast, conventional processes rely upon microbes to accomplish the hydrolysis step. This reaction is quite slow, since microbes have to first produce enzymes which then slowly degrade the feedstock. Often the microbes are not adapted to the feedstock and cannot produce the required enzymes and the process comes to a standstill. The subsequent acidification & anaerobic reactions to produce biogas are also very slow. This is one of the reasons conventional anaerobic processes require residence times ranging from 30 to 90 days to accomplish complete conversion of typical organic feedstocks to biogas. On the other hand, the process of this invention will complete the digestion process of the same feedstock in shorter time. 2. Adaptability to different feedstocks is an advantage of the process of this invention over conventional processes. Again, this is because conventional processes rely on microbes to accomplish both the hydrolysis step as well as the biogas generation step. Thus, in case of a change in feedstock, the microbes may fail to adapt to the change and the process comes to a standstill. In the process of this invention, the biogas generating bacteria are fed an 'Intermediate Broth' of fairly consistent quality, regardless of primary feedstock, thus avoiding any upsets. WE CLAIM 1. A process for production of biogas containing Methane, utilizing solid organic feedstock of natural origin, comprising the following steps: (a) Preparation of a Methane producing anaerobic microbial culture utilising a growth medium containing at least each member of the following group : Xylose, Rhannose, Arabinose, Glucose, Mannose, Galactose, Sucrose, Soya bean meal. Groundnut meal, Urea, Phosphoric acid. Cellulose powder, Starch powder, Acetic acid, Propionic acid. Butyric acid. Formic Acid, p-Hydroxy Cinnamyl Alcohol, Coniferyl alcohol, Sinapyl alcohol, p-Coumaryl alcohol. Furfural, Hydroxymethyl furfural, 4-0-methyl-glucuronic acid, Galacturonic acid, and (b) Feedstock processing, comprising size reduction of the said solid organic feedstock to obtain sohd particles of not more than 50 millimetre size and then controlled heating of said particles under controlled pressure in the presence of Water at Neutral pH, till it results in the release from the solid feedstock of sufficient biodegradable organic molecules, the concentration of the said organic molecules being such that it would result in a Biochemical Oxygen Demand (BOD5) of the surrounding liquid of at least 1000 Milligrams/ litre and the said organic molecules comprising at least one member firom the group: Xylose, Rhannose, Arabinose, Glucose, Mannose, Galactose, Sucrose and additionally comprising at least one member from the group: Acetic acid. Propionic acid. Butyric acid and subsequently stopping the heating of the said particles and further adding Water, recycled digested slurry from the main anaerobic digestion unit and Urea, Phosphoric acid. Sodium hydroxide and adjusting the pH of the mixture to be about Neutral and blending the mixture thoroughly in order to produce a homogeneous suspension hereinafter termed 'Intermediate Broth', and (c) Mixing a portion of the said Litermediate Broth from step (b) under anaerobic conditions and controlled conditions of temperature, pressure and pH, with the said anaerobic bacterial culture from step (a) and incubating under strict anaerobic conditions and controlled conditions of temperature, pressure and pH till the produced gas composition is consistently at least 55% by volume of Methane, after which this Methane producing Broth is considered to be sufficiently adapted and therefore hereinafter termed 'adapted inoculum' and shall be used as inoculum to start and sustain the main anaerobic digestion, and (d) Mixing the said 'adapted inoculum' from step (c ) with the remaining portion of said Intermediate Broth from step (b) under anaerobic conditions and transferring to the main digestion unit, which comprises a single stage of anaerobic digestion , in which Acetogenic and Methanogenic reactions occur within the same anaerobic digestion stage, under controlled conditions of temperature, pressure, pH and sufficient mixing, with an average retention time of at least 6 hours for the digesting mass, continuously withdrawing the produced bio-gas, and (e) Controlled withdrawal of the liquid and solid contents from the said main anaerobic digestion unit, after at least 6 hours of retention time in the said main anaerobic digestion unit and replacing the withdrawn volume with fresh slurry from step (d), ensuring that anaerobic conditions are maintained in the said digestion unit during slurry withdrawal and filling and recycling a portion of the withdrawn fluid from the said digestion unit to form a constituent of the mixture described in step (b). 2. A process for production of biogas containing Methane, from fluid organic feedstock of natural origin, containing at least 1% by weight of dry organic feedstock of natural origin, comprising the following steps: (a) Preparation of a Methane producing anaerobic microbial culture utilising a growth medium containing at least each member of the following group : Xylose, Rharmose, Arabinose, Glucose, Mannose, Galactose, Sucrose, Soya bean meal, Groundnut meal. Urea, Phosphoric acid. Cellulose powder. Starch powder. Acetic acid. Propionic acid, Butyric acid. Formic Acid, p-Hydroxy Cinnamyl Alcohol, Coniferyl alcohol, Sinapyl alcohol, p-Coumaryl alcohol, Furfural, Hydroxymethyl furfural, 4-0-methyl-glucuronic acid, Galacturonic acid, and (b) Feedstock processing, comprising controlled heating of the said fluid feedstock under controlled pressure in the presence of Water at Neutral pH, till it results in the release from the said fluid organic feedstock of sufficient biodegradable organic molecules, the concentration of the said organic molecules being such that it would result in a Biochemical Oxygen Demand (BOD5) of the fluid of at least 1000 Milligrams/ litre and the said organic molecules comprising at least one member from the group: Xylose, Rhannose, Arabinose, Glucose, Mannose, Galactose, Sucrose and additionally comprising at least one member from the group: Acetic acid, Propionic acid. Butyric acid and subsequently stopping the heating of the fluid and further adding Water, recycled digested slurry from main anaerobic digestion unit, and Urea, Phosphoric acid. Sodium hydroxide and adjusting the pH of the mixture to be about Neutral and blending the mixture thoroughly in order to produce a homogeneous suspension hereinafter termed 'Intermediate Broth', and (c) Mixing a portion of the said Intermediate Broth from step (b) under anaerobic conditions and controlled conditions of temperature, pressure and pH, with the said anaerobic bacterial culture from step (a) and incubating under strict anaerobic conditions and controlled conditions of temperature, pressure and pH till the produced gas composition is consistently at least 55% by volume of Methane, after which this Methane producing Broth is considered to be sufficiently adapted and therefore hereinafter termed 'adapted inoculum' and shall be used as inoculum to start and sustain the main anaerobic digestion, and (d) Mixing the said 'adapted inoculum' from step (c) with the remaining portion of said Intermediate Broth from step (b) under anaerobic conditions and transferring to the main digestion unit, which comprises a single stage of anaerobic digestion, in which Acetogenic and Methanogenic reactions occur within the same anaerobic digestion stage, under controlled conditions of temperature, pressure, pH and sufficient mixing, with an average retention time of at least 6 hours for the digesting mass, continuously withdrawing the produced bio-gas, and (e) Controlled withdrawal of the liquid and solid contents from the said main anaerobic digestion unit, after at least 6 hours of retention time in the said main anaerobic digestion unit and replacing the withdrawn volume with fresh slurry from step (d), ensuring that anaerobic conditions are maintained in the said digestion unit during slurry withdrawal and filling and recycling a portion of the withdrawn fluid from the said digestion unit to form a constituent of the mixture described in step (b). 3. A process according to claims 1 or 2, wherein the said organic feedstock originates from natural biomass comprising any member of the group: plants, vegetables, fruits, trees, foliage, crops, crop residues, forest litter, grass cuttings, flowers, seeds or originates as a byproduct or intermediate or waste from the industrial process of agro-processing or originates as a byproduct or intermediate or waste from any activity from the following group of activities : vegetable processing, fruit processing, food processing, sugar manufacture, ethanol manufacture, vinegar manufacture, wine manufacture, Starch manufacture, herbal products manufacture, tea processing, coffee processing, oilseeds processing. Pulses processing. Tapioca Processing, Sugar Beet processing, Neem fruit processing, Groundnut processing. Com processing. Soya bean processing, Rice processing. Wheat processing. Coconut and Coir processing, edible and non-edible Oilseeds processing. Rye processing. Sweet Sorghum processing, Cattlefeed manufacture or originates from any member of the group: Kitchen wastes from households. Kitchen wastes from hotels. Kitchen wastes from residential establishments, or Kitchen wastes from communities or originates from vegetable market wastes or organic municipal wastes, and wherein the said organic feedstock can be a single type of said organic feedstock or a plurality of types of said organic feedstock. 4. A process according to claims 1 or 2, wherein the composition of the said organic feedstock or plurality of said organic feedstock is in accordance with claim 3 and is predominantly comprised of Cellulose compounds and hence hereinafter termed as High Cellulose feedstock. 5. A process according to claims 1 or 2, wherein the composition of the said organic feedstock or plurality of said organic feedstock is in accordance with claim 3 and is predominantly comprised of Sugars and hence hereinafter termed as High Sugar feedstock. 6. A process according to claims 1 or 2, wherein the composition of the said organic feedstock type or plurality of said organic feedstock is in accordance with claim 3 and is predominantly comprised of Starch compounds and hence hereinafter termed as high Starch feedstock. 7. A process according to claims 1 or 2, wherein the composition of the said organic feedstock or plurality of said organic feedstock is in accordance with claim 3 and is predominantly comprised of Protein compounds and hence hereinafter termed as High Protein feedstock. 8. A process according to claims 1 or 2, wherein the composition of the said organic feedstock or plurality of said organic feedstock is in accordance with claim 3 and is predominantly comprised of Lipid compounds and hence hereinafter termed as high Fat feedstock. 9. A process according to claims 1 or 2, and claims 3, 4, 5,6,7,8 wherein the said organic feedstock is a physical mixture, in any proportion by weight, of said High Cellulose feedstock, said High sugar feedstock, said High Starch feedstock, said High Protein feedstock and said High Fat feedstock. 10. A process according to claims 1 or 2 wherein each of the members of the group: Glucose, Xylose, Acetic acid, is present at a concentration between 5% by weight and 25% by weight in the said microbial culture growth medium and each of the members of the group: Rhannose, Arabinose, Mannose, Galactose, Sucrose, Cellulose powder. Starch powder. Propionic acid. Butyric acid, Soya bean meal, Groundnut meal is present at a concentration between 1 % by weight and 10% by weight in the said microbial culture growth medium and each of the members of the group: Formic Acid, Phosphoric acid, Urea are present at a concentration between 0.5% by weight and 3 % by weight of the said microbial culture growth medium and each of the members of the group: p-Hydroxy Cinnamyl Alcohol, Coniferyl alcohol, Sinapyl alcohol, p-Coumaryl alcohol, Furfural, Hydroxymethyl furfural, 4-0-methyl-glucuronic acid, Galacturonic acid is present at a concentration between 0.0001% by weight and 0.3 % by weight of the said microbial culture growth medium. 11. A process according to claims 1 or 2 and claim 10 wherein the said microbial culture growth medium additionally includes withdrawn fluid from main anaerobic digestion unit, the concentration of the said withdrawn fluid in the said microbial culture growth medium being between 5 % by weight to 75% by weight of said microbial culture growth medium. 12. A process according to claims 1 or 2 wherein the percentage of Methane in the said biogas from said main anaerobic digestion unit ranges from 25% by volume of said biogas to 85% by volume of said biogas. 13. A process according to claims 1 or 2 wherein the said Acetogenic reactions are due to the presence in the said anaerobic microbial culture of any member of the group known in microbiology as: Mesophilic Acetogenic bacteria , Thermophilic Acetogenic bacteria and wherein the said Methanogenic reactions are due to the presence in the said anaerobic microbial culture of any member of the group known in microbiology as: Mesophilic Methanogenic bacteria. Thermophilic Methanogenic bacteria . 14. A process according to claims 1 or 2 wherein the temperature during the said heating is maintained between 40 Degrees Centigrade to 75 Degrees Centigrade. 15. A process according to claims 1 or 2 wherein the temperature during the said heating is maintained between 75 Degrees Centigrade to 250 Degrees Centigrade 16. A process according to claims 1 or 2 wherein the Pressure during the said heating is maintained between 1 KiloPascals (gauge) and 1000 KiloPascals (gauge). 17. A process according to claims 1 or 2 wherein the Pressure during the said heating is maintained between 1000 KiloPascals (gauge) and 25000 KiloPascals (gauge). 18. A process according to claims 1 or 2, and claims 3,4,5,6,7,8,9 wherein the said organic feedstock is subjected to said heat and pressure by high pressure steam in direct contact with the said organic feedstock. 19. A process according to claims 1 or 2, and claims 3,4,5,6,7,8,9 wherein the said organic feedstock is subjected to said heat and pressure while in direct contact with Water that is in a thermodynamic state beyond its Critical point. 20. A process according to claims 1 or 2, and claims 3,4,5,6,7,8,9 wherein the said organic feedstock is subjected to said heat by indirect heating utilizing any one or more members of the group: heat exchanger, vessel, fired heater, water-bath heater, electrical heater, solar heater. 21. A process according to claims 1 or 2, and claims 3,4,5,6,7,8,9 wherein the said organic feedstock is subjected to said pressure by utilizing pressurised fluids. 22. A process according to claims 1 or 2 where the pH in the said main anaerobic digestion unit is kept above pH 7.0 using a member of the group: Sodium Hydroxide, Calcium Hydroxide, Potassium hydroxide; Ammonia, Ammonium Hydroxide, Sodium Carbonate, Sodium Bi-Carbonate. 23. A process according to claims 1 or 2 wherein the pH of the said Intermediate Broth is adjusted to between 7.0 and 8.0. 24. A process according to claims 1 or 2 wherein the temperature within the said main anaerobic digester unit is maintained at between 30 degrees Centigrade to 70 degrees centigrade. 25. A process according to claims 1 or 2 wherein the pressure within the said main anaerobic digester unit is maintained at between 0.1 KiloPascals (gauge) to 75 KiloPascals (gauge). 26. A process according to claims 1 or 2 wherein the pressure within the said main anaerobic digester unit is maintained at between 75 KiloPascals (gauge) to 3500 KiloPascals (gauge). 27. A process according to claims 1 or 2 wherein the pH of the said digesting mass within the said main anaerobic digester unit is maintained at between 7.0 and 8.0. 28. A process according to claims 1 or 2 wherein retention time of the said digesting mass in the said main single stage of anaerobic digestion is controlled at between 6 hours and 100 hours. 29. A process according to claims 1 or 2 wherein retention time of the said digesting mass in the said main single stage of anaerobic digestion is controlled at between 100 hours and 480 hours.

Full Text

INTRODUCTION
The subject of this patent is a process for production of biogas from organic feedstocks of natural origin.
The innovations in this process pertain to:
i. Increase in the overall speed of conversion of feedstock to biogas: This improvement is achieved by utilizing a pre-adapted bacterial culture, thus avoiding the time delay for bacterial adaptation to feedstock and also by decomposing the feedstock to a predetermined extent such that degree of feedstock decomposition is matched with the metabolic requirements of the bacterial culture, thus avoiding the time delay for bacteria to hydrolyse the feedstock.
ii. Ability to handle a variety of organic feedstocks of variable quality without resulting in process upsets: This improvement is achieved by ensuring a specific degree of feedstock decomposition such that regardless of the primary feedstock, the bacterial culture is exposed only to a decomposed feedstock to which it is pre-adapted. In contrast, conventional processes are designed to handle single feedstocks with consistent feed quality and are known to go out of control if the primary feedstock quality changes significantly.
UTILITY
This invention would be especially useful in the conversion of natural organic biomass or solid & liquid wastes or other natural organics from domestic and industrial sources, into a valuable fuel i.e., biogas.
DESCRIPTION OF THE PROCESS
Organic feedstock of natural origin is the primary feedstock for this process. The feedstock could be sourced from raw biomass or processed biomass. Some examples of raw biomass are plants, vegetables, fruits, trees, foliage, crops, crop residues, forest litter, grass cuttings, flowers, seeds. The biomass could be from industrial or domestic sources. Some examples of biomass from industrial sources are byproducts, intermediates or wastes from agro-processing industries such as vegetable processing, fruit processing food processing. Sugar manufacture, Ethanol manufacture, Vinegar manufacture. Wine manufacture. Starch manufacture, Herbal products manufacture. Tea processing. Coffee processing, Sugar Beet processing, Sweet Sorghum processing, Neem fruit processing. Groundnut processing, Com processing. Soya bean processing, Rice processing, Wheat processing. Coconut and Coir processing, edible and non-edible Oilseeds processing. Rye processing, Cattlefeed manufacture. Some examples of biomass from domestic and community sources are Kitchen wastes from households, hotels or vegetable market wastes or organic municipal wastes.

It is known that organic materials of natural origin are mainly made up of Carbohydrates, Proteins and Fats, apart from various essential minerals, vitamins etc. Biomass can be of various types, i.e Cellulosic, Starchy, Proteinaceous, Fatty, or contain all these categories of molecules in varying proportions. This invention can handle all these types of biomass in any combination. This is because, regardless of the type of biomass, they can all be decomposed biologically into simpler Sugars, Fatty acids, Amino acids etc. along well-known metabolic pathways (e.g Enzymatic hydrolysis, Krebs cycle, Embden Meyerhoff pathway). In nature, bacteria have the ability to decompose all types of complex natural molecules into simpler molecules as part of their metabolic activity, using intra-cellular and exo-cellular enzymes. More importantly, from the viewpoint of industrial applications, it is known that bacteria can adapt themselves to utilize different types of organic molecules. During the process of adaptation, bacterial populations learn to produce 'new' enzymes, which can break down and metabolize unfamiliar organic molecules, i.e molecules which are not normally part of their 'diet'. This process takes time, but can be accomplished under controlled conditions using standard microbiological techniques.
The principle underlying this invention is the fact that all types of biomass, during the process of biological decomposition, produce common intermediates and end products, depending on whether the decomposition is aerobic, anaerobic or facultative. Thus, if different types of feedstock are first treated physico-chemically, to yield a common set of intermediate molecules and if the target bacterial populations are pre-adapted to this common set of molecules, then it is possible to achieve a faster and stable biological degradation process. The process is faster because adaptation time and hydrolysis time are substantially reduced. The process is stable, since, regardless of variations in type of feedstock, the bacteria are exposed only to the intermediate molecules, to which they are already adapted.
The steps of the process are:
(a) Methanogenic culture on special growth medium: The first requirement of the process is to grow a pre-adapted microbial culture, capable of producing Methane from decomposed organic feedstock. The technique of growing Methanogenic cultures is well known in microbiology. In this invention, the Methanogenic microbial culture is grown on a special growth medium, which is composed of key molecules that are produced during decomposition of various common types of biomass. This ensures that during an early stage of their evolution, the bacteria develop the ability to survive and grow in the presence of these key molecules. In this invention, these key molecules comprise Xylose, Rhannose, Arabinose, Glucose, Mannose, Galactose, Sucrose, Amino acids. Cellulose, Starch, Acetic acid. Propionic acid. Butyric acid. Formic Acid, p-Hydroxy Cinnamyl Alcohol, Coniferyl alcohol, Sinapyl alcohol, p-Coumaryl alcohol, Furfural, Hydroxymethyl furfural, 4-0-methyl-glucuronic acid, Galacturonic acid. Soya bean meal and Groundnut meal are added as good natural sources of Amino-acids and Lipids. Nitrogen and Phosphorus are essential for any biological process and these are added in the form of Urea and Phosphoric acid. The composition of the growth medium is important to get an efficient culture and this invention utilizes the following proportions

of its various constituents: Glucose, Xylose, Acetic acid, to be present at a concentration between about 5% by weight and about 25% by weight and each of the members of the group: Rhannose, Arabinose, Mannose, Galactose, Sucrose, Cellulose powder. Starch powder. Propionic acid. Butyric acid. Soya bean meal. Groundnut meal is present at a concentration between about 1% by weight and about 10% by weight in the microbial culture growth medium; each of the members of the group: Formic Acid, Phosphoric acid. Urea are present at a concentration between about 0.5% by weight and about 3 % by weight and each of the members of the group: p-Hydroxy Ciimamyl Alcohol, Coniferyl alcohol, Sinapyl alcohol, p-Coumaryl alcohol, Furfural, Hydroxymethyl furfural, 4-0-methyl-glucuronic acid, Galacturonic acid is present at a concentration between about 0.0001% by weight and about 0.3 % by weight of the microbial culture growth medium. Further, withdrawn fluid from main anaerobic digestion unit can also be added, the concentration being between about 5 % by weight to about 75% by weight of the microbial culture growth medium. This ensures that the species which evolve and grow in the medium would be representative of the populations which survive in the large scale digester. Fresh cow-dung can also be added, if anaerobic digester fluid is not available.
(b) A Feedstock conversion step: This step uses known methods of applying heat and pressure and is designed to decompose the feedstock to a pre-determined extent. The intention of this step is to decompose the feedstock to an extent that produces smaller molecules, to which the bacteria are pre-adapted. In other words, this step makes sure that the processed feedstock and the bacterial culture are 'made for each other', and hence the main anaerobic digestion can start immediately without delay caused by bacterial adaptation. In this invention, the feedstock conversion step of the process shall be conducted by applying heat and pressure to the feedstock in the presence of Water at a Neutral pH. In the case of solid feedstock, the size of the solids is first reduced to less than 50 millimetres, before subjecting the feedstock to heat and pressure. Size reduction is required to enable efficient physico-chemical decomposition. In the case of fluid organic feedstock, the size reduction step is not necessary and the fluid feedstock shall be directly subjected to heat and pressure in the presence of Water, at neutral pH. In this invention, the temperature during heating can be maintained anywhere between about 40 Degrees Centigrade to about 250 Degrees Centigrade, depending on the nature of the feedstock. Similarly, the Pressure during heating can be maintained anywhere between about 1 KiloPascals (gauge) to about 25000 KiloPascals (gauge).Water and neutral pH are necessary in this process.
An analogy with 'cooking vegetables in a pressure cooker' is appropriate at this point, to explain to the layman the purpose of this step; this is because a 'pressure cooker' utilizes heat and mild pressure, which along with Water (and steam), transform vegetables in the cooker into more easily digestible forms, for human consumption. In a similar way, the feedstock conversion step aims to utilize high pressure, temperature and Water to achieve the desired decomposition of biomass. Obviously, it is likely that at higher temperatures and corresponding pressures. Water would boil off and become steam or else it may even reach a temperature and pressure that is beyond the thermodynamic Critical point of Water, when it ceases to be either a liquid or a vapour. Thus in such cases, the organic feedstock would actually be subjected to heat and pressure by high pressure steam in

direct contact with the organic feedstock, or by super-critical Water (i.e Water beyond its Critical point) in direct contact with the organic feedstock.
The actual choice of process conditions for the feedstock conversion step depends on the type of feedstock. Biomass can be of various types, i.e Cellulosic, Starchy, Proteinaceous, Fatty, or contain all these categories of molecules in varying proportions. On this basis, the various types of feedstock can be divided into the following categories:

•
High Cellulose feedstock, wherein the composition of the organic feedstock is predominantly comprised of Cellulose compounds.
• High Sugar feedstock, wherein the composition of the organic feedstock is predominantly comprised of Sugars.
• High Starch feedstock, wherein the composition of the organic feedstock is predominantly comprised of Starch compounds.
• High Protein feedstock, wherein the composition of the organic feedstock is predominantly comprised of Protein compounds.
• High Fat feedstock, wherein the composition of the organic feedstock is predominantly comprised of Lipid compounds.
• Furthermore, the organic feedstock can be a physical mixture, in any proportion by weight, of High Cellulose feedstock, High Sugar feedstock. High Starch feedstock. High Protein feedstock and High Fat feedstock.
This invention specifies only the range of applicable process conditions and the specified process steps can be conducted in any machinery suitable for the purpose. Some examples of the type of equipment that can be used to subject the organic feedstock to heat by indirect heating are: heat exchangers, vessels, fired heaters, water-bath heater, electrical heater, solar heater. Similarly, pressurising equipment such as pumps or various types of presses can be used to directly pressurize the feedstock or, pressurized fluids can be used to create the necessary conditions of high pressure.
The essence of this step is that the degree of feedstock decomposition must be controlled to ensure that key molecules, which the pre-adapted bacteria can readily consume, become available in sufficient quantity. This is ensured by checking the following points:
• Monitoring BOD5 (5 day Biochemical Oxygen Demand) in the liquid phase.
• Monitoring the presence of key molecules, which would indicate that decomposition is proceeding in the right direction, to the required extent.
The decomposed feedstock, is then adjusted to neutral pH and blended thoroughly with recycle slurry from main anaerobic digester, so that the ensuing broth is in a similar state

to material already successfully undergoing anaerobic digestion. The homogeneous suspension, which is ready to be fed to the bacteria, is termed 'Intermediate Broth'.
(c ) An inoculum development step: The intent of this step is to multiply the bacterial culture till sufficient quantity of viable bacteria are available to seed the main digester. A small part of the 'Intermediate Broth' is used for the inoculum development while the balance goes to anaerobic digesters. A portion of the Intermediate Broth from step (b) is mixed under anaerobic conditions and controlled conditions of temperature, pressure and pH, with the pre-adapted anaerobic bacterial culture from step (a) and incubated under strict anaerobic conditions and controlled conditions of temperature, pressure and pH till the produced gas composition is consistently at least 55% by volume of Methane, after which this Methane producing Broth is considered to be sufficiently adapted and therefore hereinafter termed 'adapted inoculum' and shall be used as inoculum to start and sustain the main anaerobic digestion. The pH in the inoculum development digester is kept at about pH 7.0-8.0 and the temperature between about 30 degrees Centigrade to about 70 degrees centigrade; the pressure is maintained at between about 0.1 KiloPascals (gauge) to about 3500 KiloPascals (gauge).
(d) The main anaerobic digestion step: The main anaerobic digesters are 'seeded' with adapted inoculum from the inoculum development section. This involves mixing the 'adapted inoculum' from step (c ) with the remaining portion of Intermediate Broth from step (b) under anaerobic conditions and transferring to the main digestion unit. The main anaerobic digestion unit comprises a single stage of anaerobic digestion, in which Acetogenic and Methanogenic reactions occur within the same anaerobic digestion stage, under controlled conditions of temperature, pressure, pH and sufficient mixing, with an average retention time of at least 6 hours for the digesting mass. The produced bio-gas has to be continuously withdrawn, to ensure that excessive partial-pressure of Hydrogen within the digesting mass does not inhibit the reaction. The pH in the main anaerobic digestion unit is kept at about pH 7.0-8.0, using a member of the group: Sodium Hydroxide, Calcium Hydroxide, Potassium hydroxide; Ammonia, Ammonium Hydroxide, Sodium Carbonate, Sodium Bi-Carbonate. The temperature within the main anaerobic digester unit is maintained at between about 30 degrees Centigrade to about 70 degrees centigrade and the pressure within the main anaerobic digester unit is maintained at between about 0.1 KiloPascals (gauge) to about 3500 KiloPascals (gauge).
(e) Digested product withdrawal and fresh feed step: Controlled withdrawal of the liquid and solid contents from the said main anaerobic digestion unit can be done after at least 6 hours of retention time in the main anaerobic digestion unit and replacing the withdrawn volume with fresh slurry from step (d), ensuring that anaerobic conditions are maintained in the said digestion unit during slurry withdrawal and filling. A portion of the withdrawn fluid from the said digestion unit is recycled to form a constituent of the mixture described in step (b). The retention time of the digesting mass in the main single stage of anaerobic digestion is controlled at between about 6 hours and about 480 hours, depending on the feedstock and the desired product quality.

WORKING PRINCIPLE
This invention is a process that combines a physico-chemical feedstock conversion step with a microbial fermentation step to obtain a high rate, flexible process for converting organic feedstocks to biogas.
The physico-chemical nature of the feedstock conversion step enables the processing of varying feedstocks to yield 'Intermediate Broth'. This step is based on the proven principle that all natural organic materials can be decomposed by physico-chemical means to smaller, biodegradable molecules. The resulting mixture of biodegradable compounds along with inerts, is termed 'Intermediate Broth'. The physico-chemical step imparts speed and flexibility to the overall process. The physico-chemical step is conducted by applying heat and pressure to the feedstock in the presence of Water at a Neutral pH, such that the feedstock decomposes to a pre-determined extent. In the case of solid feedstock the size of the solids are first reduced to less than 50 millimetres, before subjecting the feedstock to heat and pressure. The essence of this invention is that the degree of feedstock decomposition must be controlled to ensure that molecules which the pre-adapted bacteria can readily consume become available in sufficient quantity. This is ensured by checking the following points:
• Monitoring BOD5 (5 day Biochemical Oxygen Demand) of the liquid during feedstock decomposition, to ensure that the concentration of organic molecules corresponds to a BOD5 value of at least 1000 milligrams per litre. The COD (Chemical Oxygen Demand) can be monitored instead of BOD5 provided a validated conversion formula is used to calculate the equivalent BOD5.
• Analysing the liquid phase during feedstock decomposition to monitor concentration of some of the key molecules readily metabolizable by the pre-adapted bacteria, such as any of Glucose, Rhannose, Xylose, Arabinose, Galactose, Sucrose, Acetic acid. Propionic acid and Butyric acid.
Once the above decomposition is completed satisfactorily, the resulting Broth is further pH adjusted (if necessary) and nutrients such as Urea and Phosphate added and the mixture is termed Intermediate Broth.
Anaerobic fermentation of the 'Intermediate Broth' then produces biogas. This step utilizes a special microbial culture that can adapt itself quickly to changes in composition of the 'Intermediate Broth'. The feedstock conversion step is designed to ensure that the variations in 'Intermediate Broth' composition remain in a fairly narrow band, well within the adaptive capabilities of the microbial culture. Thus, the microbial culture is exposed only to permissible variations in the 'Intermediate Broth' and not to drastic variations that can occur in the primary feedstock. This ensures that the microbial metabolic processes are not upset and the biogas production proceeds smoothly.

PRIOR ART
The science of anaerobic fermentation has been well understood for more than a century. Similarly, physico-chemical transformation of natural organics into fermentable intermediates is also well known.
However, combination of physico-chemical processes with a subsequent microbial fermentation step has been reported in detail only for Ethanol manufacture and some aerobic fermentation products from materials like wood, com cob, etc. In these processes, wood and other organic materials were converted to fermentable sugars and acids which were then converted to Ethanol by Yeast. This technology is reported to have been popular during the World War years, to produce fuel grade Ethanol.
In U.S Pat. No. 6,059,972 to Mahrer, which claims an apparatus for anaerobic digestion of Kitchen Wastes, the process by which the disclosed apparatus works comprises mechanical grinding of Kitchen Waste before anaerobic digestion. The process disclosed does not include the decomposition of feedstock prior to anaerobic digestion by applying heat and pressure in the presence of Water at a Neutral pH or by any other physico-chemical means. The process disclosed does not include the use of pre-adapted bacteria, to handle feedstock quality variations and to speed up the digestion process. In fact, in the narrative description of the Patent, it is stated that 'Stability is indeed an essential condition for maintaining the biological process for transforming the materials'. This would indicate that the process is not designed to handle significant variations in feedstock quality. The process also does not disclose any capability to handle feedstock other than Kitchen Waste. For example it is not expected to handle a high Cellulosic feedstock such as Coir pith or Bagasse. Thus the invention by Mahrer is designed for a specific type of feedstock and cannot handle significant variations in feedstock quality and cannot handle a wide variety of organic feedstock. It is precisely these issues which are now claimed to be resolved in the process of this invention, in addition to increasing the overall speed of the conversion to biogas by using the innovation of physico-chemical feedstock conversion and pre-adaptation of bacteria.
In U.S Pat. No. 4,750,454 to Santina and Chatterjee, which claims a Manure Digester and power generating system, the system is designed to work only with manure. Such systems are very well known, for example, the numerous Gobar Gas plants in India which handle Cow or Buffalo manure. The Manure digestion process is different from a process that directly handles biomass, since manure is formed from edible biomass that has already been well digested in the digestive system of animals. The manure digester cannot handle the kind of variable organic feedstock that is the subject of this invention.
Thus, in the survey of prior art, there is no report of a similar process that utilizes heat and pressure in the presence of Water at Neutral pH to decompose the feedstock prior to digestion and which utilizes a pre-adapted bacterial culture that produces biogas in a single stage of anaerobic digestion. Biogas is approximately 60% Methane and 40% Carbondioxide by volume. Biogas fermentations are quite difficult when compared to Ethanol fermentation. The anaerobic bacteria which produce biogas are extremely slow-

growing and sensitive creatures and are easily upset by changes in medium composition. This is why a Microbial culture that is adapted to one feedstock does not work satisfactorily with another.
Therefore, this invention, which claims a High Rate Process that links a physico-chemical decomposition step to a succeeding anaerobic step to produce biogas and is capable of handling wide variations in feedstock quality with faster production of biogas, is an original invention.
ADVANTAGES OF THE PROCESS OF THIS INVENTION
The process of this invention has the following advantages over other known biogas production processes existing at this time:
1. Speed is an advantage of the process of this invention over conventional processes.
The process of this invention does not rely upon microbes to hydrolyse complex organics
into simpler intermediates and utilizes heat and pressure along with Neutral pH Water to
achieve speedy decomposition of feedstock. In contrast, conventional processes rely upon
microbes to accomplish the hydrolysis step. This reaction is quite slow, since microbes
have to first produce enzymes which then slowly degrade the feedstock. Often the
microbes are not adapted to the feedstock and cannot produce the required enzymes and
the process comes to a standstill. The subsequent acidification & anaerobic reactions to
produce biogas are also very slow. This is one of the reasons conventional anaerobic
processes require residence times ranging from 30 to 90 days to accomplish complete
conversion of typical organic feedstocks to biogas.
On the other hand, the process of this invention will complete the digestion process of the same feedstock in shorter time.
2. Adaptability to different feedstocks is an advantage of the process of this invention
over conventional processes. Again, this is because conventional processes rely on
microbes to accomplish both the hydrolysis step as well as the biogas generation step.
Thus, in case of a change in feedstock, the microbes may fail to adapt to the change and
the process comes to a standstill.
In the process of this invention, the biogas generating bacteria are fed an 'Intermediate Broth' of fairly consistent quality, regardless of primary feedstock, thus avoiding any upsets.

WE CLAIM
1. A process for production of biogas containing Methane, utilizing solid organic feedstock of natural origin, comprising the following steps:
(a) Preparation of a Methane producing anaerobic microbial culture utilising a growth medium containing at least each member of the following group : Xylose, Rhannose, Arabinose, Glucose, Mannose, Galactose, Sucrose, Soya bean meal. Groundnut meal, Urea, Phosphoric acid. Cellulose powder, Starch powder, Acetic acid, Propionic acid. Butyric acid. Formic Acid, p-Hydroxy Cinnamyl Alcohol, Coniferyl alcohol, Sinapyl alcohol, p-Coumaryl alcohol. Furfural, Hydroxymethyl furfural, 4-0-methyl-glucuronic acid, Galacturonic acid, and
(b) Feedstock processing, comprising size reduction of the said solid organic feedstock to obtain sohd particles of not more than 50 millimetre size and then controlled heating of said particles under controlled pressure in the presence of Water at Neutral pH, till it results in the release from the solid feedstock of sufficient biodegradable organic molecules, the concentration of the said organic molecules being such that it would result in a Biochemical Oxygen Demand (BOD5) of the surrounding liquid of at least 1000 Milligrams/ litre and the said organic molecules comprising at least one member firom the group: Xylose, Rhannose, Arabinose, Glucose, Mannose, Galactose, Sucrose and additionally comprising at least one member from the group: Acetic acid. Propionic acid. Butyric acid and subsequently stopping the heating of the said particles and further adding Water, recycled digested slurry from the main anaerobic digestion unit and Urea, Phosphoric acid. Sodium hydroxide and adjusting the pH of the mixture to be about Neutral and blending the mixture thoroughly in order to produce a homogeneous suspension hereinafter termed 'Intermediate Broth', and

(c) Mixing a portion of the said Litermediate Broth from step (b) under anaerobic conditions and controlled conditions of temperature, pressure and pH, with the said anaerobic bacterial culture from step (a) and incubating under strict anaerobic conditions and controlled conditions of temperature, pressure and pH till the produced gas composition is consistently at least 55% by volume of Methane, after which this Methane producing Broth is considered to be sufficiently adapted and therefore hereinafter termed 'adapted inoculum' and shall be used as inoculum to start and sustain the main anaerobic digestion, and
(d) Mixing the said 'adapted inoculum' from step (c ) with the remaining portion of said Intermediate Broth from step (b) under anaerobic conditions and transferring to the main digestion unit, which comprises a single stage of anaerobic digestion , in which Acetogenic and Methanogenic reactions occur within the same anaerobic digestion stage, under controlled conditions of temperature, pressure, pH and sufficient mixing, with an average retention time of at least 6 hours for the digesting mass, continuously withdrawing the produced bio-gas, and

(e) Controlled withdrawal of the liquid and solid contents from the said main anaerobic digestion unit, after at least 6 hours of retention time in the said main anaerobic digestion unit and replacing the withdrawn volume with fresh slurry from step (d), ensuring that anaerobic conditions are maintained in the said digestion unit during slurry withdrawal and filling and recycling a portion of the withdrawn fluid from the said digestion unit to form a constituent of the mixture described in step (b).
2. A process for production of biogas containing Methane, from fluid organic feedstock of natural origin, containing at least 1% by weight of dry organic feedstock of natural origin, comprising the following steps:
(a) Preparation of a Methane producing anaerobic microbial culture utilising a growth medium containing at least each member of the following group : Xylose, Rharmose, Arabinose, Glucose, Mannose, Galactose, Sucrose, Soya bean meal, Groundnut meal. Urea, Phosphoric acid. Cellulose powder. Starch powder. Acetic acid. Propionic acid, Butyric acid. Formic Acid, p-Hydroxy Cinnamyl Alcohol, Coniferyl alcohol, Sinapyl alcohol, p-Coumaryl alcohol, Furfural, Hydroxymethyl furfural, 4-0-methyl-glucuronic acid, Galacturonic acid, and
(b) Feedstock processing, comprising controlled heating of the said fluid feedstock under controlled pressure in the presence of Water at Neutral pH, till it results in the release from the said fluid organic feedstock of sufficient biodegradable organic molecules, the concentration of the said organic molecules being such that it would result in a Biochemical Oxygen Demand (BOD5) of the fluid of at least 1000 Milligrams/ litre and the said organic molecules comprising at least one member from the group: Xylose, Rhannose, Arabinose, Glucose, Mannose, Galactose, Sucrose and additionally comprising at least one member from the group: Acetic acid, Propionic acid. Butyric acid and subsequently stopping the heating of the fluid and further adding Water, recycled digested slurry from main anaerobic digestion unit, and Urea, Phosphoric acid. Sodium hydroxide and adjusting the pH of the mixture to be about Neutral and blending the mixture thoroughly in order to produce a homogeneous suspension hereinafter termed 'Intermediate Broth', and
(c) Mixing a portion of the said Intermediate Broth from step (b) under anaerobic conditions and controlled conditions of temperature, pressure and pH, with the said anaerobic bacterial culture from step (a) and incubating under strict anaerobic conditions and controlled conditions of temperature, pressure and pH till the produced gas composition is consistently at least 55% by volume of Methane, after which this Methane producing Broth is considered to be sufficiently adapted and therefore hereinafter termed 'adapted inoculum' and shall be used as inoculum to start and sustain the main anaerobic digestion, and
(d) Mixing the said 'adapted inoculum' from step (c) with the remaining portion of said Intermediate Broth from step (b) under anaerobic conditions and transferring to the main digestion unit, which comprises a single stage of anaerobic digestion, in which Acetogenic and Methanogenic reactions occur within the same anaerobic digestion stage,

under controlled conditions of temperature, pressure, pH and sufficient mixing, with an average retention time of at least 6 hours for the digesting mass, continuously withdrawing the produced bio-gas, and
(e) Controlled withdrawal of the liquid and solid contents from the said main anaerobic digestion unit, after at least 6 hours of retention time in the said main anaerobic digestion unit and replacing the withdrawn volume with fresh slurry from step (d), ensuring that anaerobic conditions are maintained in the said digestion unit during slurry withdrawal and filling and recycling a portion of the withdrawn fluid from the said digestion unit to form a constituent of the mixture described in step (b).
3. A process according to claims 1 or 2, wherein the said organic feedstock originates from natural biomass comprising any member of the group: plants, vegetables, fruits, trees, foliage, crops, crop residues, forest litter, grass cuttings, flowers, seeds or originates as a byproduct or intermediate or waste from the industrial process of agro-processing or originates as a byproduct or intermediate or waste from any activity from the following group of activities : vegetable processing, fruit processing, food processing, sugar manufacture, ethanol manufacture, vinegar manufacture, wine manufacture, Starch manufacture, herbal products manufacture, tea processing, coffee processing, oilseeds processing. Pulses processing. Tapioca Processing, Sugar Beet processing, Neem fruit processing, Groundnut processing. Com processing. Soya bean processing, Rice processing. Wheat processing. Coconut and Coir processing, edible and non-edible Oilseeds processing. Rye processing. Sweet Sorghum processing, Cattlefeed manufacture or originates from any member of the group: Kitchen wastes from households. Kitchen wastes from hotels. Kitchen wastes from residential establishments, or Kitchen wastes from communities or originates from vegetable market wastes or organic municipal wastes, and wherein the said organic feedstock can be a single type of said organic feedstock or a plurality of types of said organic feedstock.
4. A process according to claims 1 or 2, wherein the composition of the said organic feedstock or plurality of said organic feedstock is in accordance with claim 3 and is predominantly comprised of Cellulose compounds and hence hereinafter termed as High Cellulose feedstock.
5. A process according to claims 1 or 2, wherein the composition of the said organic feedstock or plurality of said organic feedstock is in accordance with claim 3 and is predominantly comprised of Sugars and hence hereinafter termed as High Sugar feedstock.
6. A process according to claims 1 or 2, wherein the composition of the said organic feedstock type or plurality of said organic feedstock is in accordance with claim 3 and is predominantly comprised of Starch compounds and hence hereinafter termed as high Starch feedstock.
7. A process according to claims 1 or 2, wherein the composition of the said organic feedstock or plurality of said organic feedstock is in accordance with claim 3 and is

predominantly comprised of Protein compounds and hence hereinafter termed as High Protein feedstock.
8. A process according to claims 1 or 2, wherein the composition of the said organic feedstock or plurality of said organic feedstock is in accordance with claim 3 and is predominantly comprised of Lipid compounds and hence hereinafter termed as high Fat feedstock.
9. A process according to claims 1 or 2, and claims 3, 4, 5,6,7,8 wherein the said organic feedstock is a physical mixture, in any proportion by weight, of said High Cellulose feedstock, said High sugar feedstock, said High Starch feedstock, said High Protein feedstock and said High Fat feedstock.

10. A process according to claims 1 or 2 wherein each of the members of the group: Glucose, Xylose, Acetic acid, is present at a concentration between 5% by weight and 25% by weight in the said microbial culture growth medium and each of the members of the group: Rhannose, Arabinose, Mannose, Galactose, Sucrose, Cellulose powder. Starch powder. Propionic acid. Butyric acid, Soya bean meal, Groundnut meal is present at a concentration between 1 % by weight and 10% by weight in the said microbial culture growth medium and each of the members of the group: Formic Acid, Phosphoric acid, Urea are present at a concentration between 0.5% by weight and 3 % by weight of the said microbial culture growth medium and each of the members of the group: p-Hydroxy Cinnamyl Alcohol, Coniferyl alcohol, Sinapyl alcohol, p-Coumaryl alcohol, Furfural, Hydroxymethyl furfural, 4-0-methyl-glucuronic acid, Galacturonic acid is present at a concentration between 0.0001% by weight and 0.3 % by weight of the said microbial culture growth medium.
11. A process according to claims 1 or 2 and claim 10 wherein the said microbial culture growth medium additionally includes withdrawn fluid from main anaerobic digestion unit, the concentration of the said withdrawn fluid in the said microbial culture growth medium being between 5 % by weight to 75% by weight of said microbial culture growth medium.
12. A process according to claims 1 or 2 wherein the percentage of Methane in the said biogas from said main anaerobic digestion unit ranges from 25% by volume of said biogas to 85% by volume of said biogas.
13. A process according to claims 1 or 2 wherein the said Acetogenic reactions are due to the presence in the said anaerobic microbial culture of any member of the group known in microbiology as: Mesophilic Acetogenic bacteria , Thermophilic Acetogenic bacteria and wherein the said Methanogenic reactions are due to the presence in the said anaerobic microbial culture of any member of the group known in microbiology as: Mesophilic Methanogenic bacteria. Thermophilic Methanogenic bacteria .
14. A process according to claims 1 or 2 wherein the temperature during the said heating is maintained between 40 Degrees Centigrade to 75 Degrees Centigrade.

15. A process according to claims 1 or 2 wherein the temperature during the said heating is maintained between 75 Degrees Centigrade to 250 Degrees Centigrade
16. A process according to claims 1 or 2 wherein the Pressure during the said heating is maintained between 1 KiloPascals (gauge) and 1000 KiloPascals (gauge).
17. A process according to claims 1 or 2 wherein the Pressure during the said heating is maintained between 1000 KiloPascals (gauge) and 25000 KiloPascals (gauge).
18. A process according to claims 1 or 2, and claims 3,4,5,6,7,8,9 wherein the said organic feedstock is subjected to said heat and pressure by high pressure steam in direct contact with the said organic feedstock.
19. A process according to claims 1 or 2, and claims 3,4,5,6,7,8,9 wherein the said organic feedstock is subjected to said heat and pressure while in direct contact with Water that is in a thermodynamic state beyond its Critical point.
20. A process according to claims 1 or 2, and claims 3,4,5,6,7,8,9 wherein the said
organic feedstock is subjected to said heat by indirect heating utilizing any one or more
members of the group: heat exchanger, vessel, fired heater, water-bath heater, electrical
heater, solar heater.
21. A process according to claims 1 or 2, and claims 3,4,5,6,7,8,9 wherein the said organic feedstock is subjected to said pressure by utilizing pressurised fluids.
22. A process according to claims 1 or 2 where the pH in the said main anaerobic digestion unit is kept above pH 7.0 using a member of the group: Sodium Hydroxide, Calcium Hydroxide, Potassium hydroxide; Ammonia, Ammonium Hydroxide, Sodium Carbonate, Sodium Bi-Carbonate.
23. A process according to claims 1 or 2 wherein the pH of the said Intermediate Broth is adjusted to between 7.0 and 8.0.
24. A process according to claims 1 or 2 wherein the temperature within the said main anaerobic digester unit is maintained at between 30 degrees Centigrade to 70 degrees centigrade.
25. A process according to claims 1 or 2 wherein the pressure within the said main anaerobic digester unit is maintained at between 0.1 KiloPascals (gauge) to 75 KiloPascals (gauge).
26. A process according to claims 1 or 2 wherein the pressure within the said main
anaerobic digester unit is maintained at between 75 KiloPascals (gauge) to 3500
KiloPascals (gauge).

27. A process according to claims 1 or 2 wherein the pH of the said digesting mass within
the said main anaerobic digester unit is maintained at between 7.0 and 8.0.
28. A process according to claims 1 or 2 wherein retention time of the said digesting
mass in the said main single stage of anaerobic digestion is controlled at between 6 hours
and 100 hours.
29. A process according to claims 1 or 2 wherein retention time of the said digesting
mass in the said main single stage of anaerobic digestion is controlled at between 100
hours and 480 hours.

Documents:

410-mas-2000-abstract.pdf

410-mas-2000-claims filed.pdf

410-mas-2000-claims granted.pdf

410-mas-2000-correspondnece-others.pdf

410-mas-2000-correspondnece-po.pdf

410-mas-2000-description(complete) filed.pdf

410-mas-2000-description(complete) granted.pdf

410-mas-2000-form 1.pdf

410-mas-2000-form 13.pdf

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Patent Number

198848

Indian Patent Application Number

410/MAS/2000

PG Journal Number

27/2006

Publication Date

07-Jul-2006

Grant Date

02-May-2006

Date of Filing

31-May-2000

Name of Patentee

SMT. VIDYA VASUDEVAN

Applicant Address

FLAT NO.302,"MADHU KIRAN"R.V. APTS.(NO.8),106,MARGOSA ROAD,MALLESWARAM,BANGALORE-560 003

Inventors:

#	Inventor's Name	Inventor's Address
1	VIDYA VASUDEVAN	FLAT NO.302,"MADHU KIRAN"R.V. APTS.(NO.8),106,MARGOSA ROAD,MALLESWARAM,BANGALORE-560 003
2	VENKATARAMANI VASUDEVAN	FLAT NO.302,"MADHU KIRAN"R.V. APTS.(NO.8),106,MARGOSA ROAD,MALLESWARAM,BANGALORE-560 003

PCT International Classification Number

C02F 3/28

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA