NOVELTY - An apparatus for continuous production of biogas from biomass comprises acidogenic reactor (1) for mixing pulverized feed with fresh water and acidogenic culture; methanogenic reactor (7) for converting volatile fatty acid to methane; filter unit (2) to separate acid solution from acidogenic reactor; acid filtrate tank (3) for storing acid solution; balancing tank (5) with two semi-permeable membrane tubes; first peristaltic pump (4) for pumping acid solution; and second peristaltic pump (6) for pumping methanogenic slurry through second membrane tube to methanogenic reactor.    USE - As apparatus for continuous production of biogas from various types of biomass (claimed); and for converting biomass into energy such as biodiesel, ethanol and biomass gasification.    ADVANTAGE - The apparatus and method improves biogas generation by segregation of two stages i.e. acidogenesis and methanogenesis by means of two separate reactors and semi-permeable membrane units. The semi-permeable membrane unit permits the migration and concentration equilibration of low molecular size fatty acids but does not permit the migration of high molecular weight undigested, semi-digested feed as also of microbial cells. The apparatus shows faster conversion of feed into biogas without undue loss of the methanogens or accumulation of unwanted metabolites. The apparatus allows continuous production of biogas while avoiding digester failure because of depletion of methanogenic microorganisms; and provides continuous, fast and efficient biomass conversion. The method gets over the problems faced in the prior art of suboptimal conditions of a single digester and the risk of digester failure. As the microorganisms are retained in their respective digesters, the process speed is improved. This results in reduction of capital cost over the conventional digesters, for getting the same output. Any unwanted metabolites formed in the methanogenic digester are removed by a reverse concentration gradient. The process of biogas production is continuous i.e. without any break.    DETAILED DESCRIPTION - An apparatus for continuous production of biogas from various types of biomass comprises an acidogenic reactor (1) for mixing pulverized feed with fresh water and acidogenic culture; a methanogenic reactor (7) for conversion of volatile fatty acids to methane; a filter unit (2) capable of separating acid solution from acidogenic reactor; an acid filtrate tank (3) capable of storing the acid solution received from the filter unit; a balancing tank (5) having first and second semi-permeable membrane tubes enclosed in it; a first peristaltic pump (4) for pumping the acid solution from the acid filtrate reactor through the first semi-permeable membrane tube of balancing tank and back to the acid filtrate reactor; and a second peristaltic pump (6) for pumping the methanogenic slurry from the methanogenic reactor through the second semi-permeable membrane tubes of balancing tank back to the methanogenic reactor, where water acting as a buffering unit is maintained around the first and second semi-permeable membrane tubes, thereby enabling passage of volatile fatty acids out of the membrane and permitting the migration of volatile fatty acids from the acidogenic slurry to the water in the balancing tank and then to methanogenic slurry without exchanging microbial populations using the principle of concentration equilibrium. The balancing tank comprises a chamber for enclosing; a first semi-permeable tube enclosed in the chamber, for passage of acid solution from it; a second semi-permeable tube enclosed in the chamber in juxtaposition with respect to first semi-permeable tube, for passage of methanogenic slurry from it; a first inlet and a first outlet openings for circulating the acid solution through the first semi-permeable openings; and a second inlet and a second outlet openings for circulating the methanogenic slurry through the second semi-permeable openings, where water is maintained in the balancing tank around the first semipermeable tube and second semi-permeable tube to enable concentration equilibrium of volatile fatty acids, pH metabolites etc.. The acidogenic reactor comprises a stirrer for stirring the contents; and a heater for heating the acidogenic reactor for maintaining the temperature of the acidogenic reactor to 30-45 degrees C. The organic matter used as feed is pre-treated using chemical, physical or enzymatic unit to convert it into small units to facilitate acidogenesis. An INDEPENDENT CLAIM is included for continuous production of biogas from various types of biomass involving: feeding an acidogenic reactor with a biomass, fresh water and acidogenic microorganisms; filtering the acidogenic slurry by filter unit for separating acid solution and slurry from it; collecting the acid solution in the acid filtrate tank for circulating from it; pumping the acid solution by first peristaltic pump from the acid filtrate tank through the balancing tank and collecting back the acid solution to the acid filtrate reactor; pumping the methanogenic slurry by second peristaltic pump from the methanogenic reactor for circulation; and permeating the acid solution through semi-permeable membrane tubes enclosed in a chamber, where the acid solution is allowed to pass through the first semi-permeable membrane tube and is collected back in the acid filtrate tank, the methanogenic slurry is allowed to pass through the second semi-permeable membrane tube and collected back in the methanogenic reactor, water acts as a unit to facilitate transport maintained around the first and second semi-permeable membrane tubes, thereby enabling passage of volatile fatty acids out of the membrane and permitting the migration of volatile fatty acids from the acid solution to the water for balancing and then to methanogenic slurry without exchanging microbial populations using the principle of concentration equilibrium.    DESCRIPTION OF DRAWING(S) - The figure shows schematic view of an apparatus for continuous production of biogas.    Acidogenic reactor (1)    Filtration Unit (2)    Acid filtrate tank (3)    Peristaltic pump for acid solution (4)    Balancing tank through which two semi-permeable membrane channels pass (5)    Peristaltic pump for methanogenic slurry (6)    Methanogenic reactor (7)