TECHNOLOGY FOCUS - BIOLOGY - Preferred Process: The bioprocess is carried out continuously. The biomass and/or the components of the media are retained in the bioreactor. The process is carried out at a dilution rate of 0.005-0.2 hour-1. The membrane module is provided outside or inside the bioreactor. The bioprocess is conducted under anaerobic conditions. In the process, additional water is formed during the bioprocess, the methanogenic archaea are cultured and methane is produced. Preferred Components: The methanogenic archaea are Methanobacteriales, Methanomicrobiales, Methanopyrales, Methanococcales, Methanosarcinales or Methanocellales. EXAMPLE - Methanothermobacter marburgenesis was cultured in a continuous bioprocess reactor, which was equipped with a bypass membrane module outside the reactor. The fermentation broth was pumped continuously through the bypass and then held the reactor volume by the continuous removal of water through the membrane module constant. During the bioprocess biomass concentration and the specific volumetric productivity and the quality of permeate were monitored. The fermentation medium comprised of 2.1g/l of ammonium chloride, 6.8 g/l of monopotassium phosphate, 3.6 g/l of sodium carbonate, 0.09 g of Titriplex I (RTM: Nitrilotriacetic acid), 0.04 g/l of magnesium chloride hexahydrate, 0.01g/l of iron(II) chloride tetrahydrate, 0.2 mg/l of cobalt chloride hexahydrate, 1.2 mg/l of nickel chloride hexahydrate and 0.2 mg/l of sodium molybdate dihydrate. The entire system was rinsed with hydrogen/carbon dioxide mixture for several minutes prior to inoculation to ensure anaerobic conditions in the vessel. For inoculation 50 ml/l of Methanothermobacter marburgenesis stock solution was transferred to medium anaerobically in the anaerobic reactor using gas tight syringe. The cultivation was carried out at 65 degrees C and stirred speed of 1500 rpm. The pH value was determined by a pH probe and measured by adding 1M diammonium carbonate solution at a value of 6.85 kept constant to compensate for the acidification of microbial growth. The culture suspension was removed from bioreactor. The separated suspension was transferred into harvesting bottle. Selective separation of water was achieved using pervaporation module. The evaporated waster was then condensed.