Biotechnological intensification of biogas production

Abstract

The importance of syntrophic relationships among microorganisms participating in biogas formation has been emphasized, and the regulatory role of in situ hydrogen production has been recognized. It was assumed that the availability of hydrogen may be a limiting factor for hydrogenotrophic methanogens. This hypothesis was tested under laboratory and field conditions by adding a mesophilic (Enterobacter cloacae) or thermophilic hydrogen-producing (Caldicellulosyruptor saccharolyticus) strain to natural biogas-producing consortia. The substrates were waste water sludge, dried plant biomass from Jerusalem artichoke, and pig manure. In all cases, a significant intensification of biogas production was observed. The composition of the generated biogas did not noticeably change. In addition to being a good hydrogen producer, C. saccharolyticus has cellulolytic activity; hence, it is particularly suitable when cellulose-containing biomass is fermented. The process was tested in a 5-m(3) thermophilic biogas digester using pig manure slurry as a substrate. Biogas formation increased at least 160-170% upon addition of the hydrogen-producing bacteria as compared to the biogas production of the spontaneously formed microbial consortium. Using the hydrogenase-minus control strain provided evidence that the observed enhancement was due to interspecies hydrogen transfer. The on-going presence of C. saccharolyticus was demonstrated after several months of semicontinuous operation.

Characterizing Bacterial Consortia from an Anaerobic Digester Treating Organic Waste for Biogas Production

“…The maximum level of biogas production in R4 was possibly due to acidogenis and methanogenisis, indicating a promising role of mixed bacterial cultures. It has been previously reported that the addition of active inoculum containing mixed bacterial cultures in the bioreactor proved to be more promising for biogas production at 35ºC and 55ºC [26].…”

Identification and Evaluation of Effective Bacterial Consortia for Efficient Biogas Production

“…The maintenance of an extremely low pressure of hydrogen is essential for the acetogenic and hydrogen producing bacteria. Although many microbial details of metabolic networks in a methanogenic consortium are not clear, present knowledge suggests that hydrogen may be a limiting substrate for methanogens [2]. This assumption is based on the fact that addition of hydrogen producing bacteria to the natural biogas-producing consortium increases the daily biogas production.…”

Bioenergy Research Needs for Heat, Electricity, and Liquid Fuels

“…In the long term, there is great interest in the engineering of microorganisms that can produce hydrogen directly from anaerobic digestion of biomass. 20,21 This effort is still early in the research phase, but it shows great promise as an inexpensive source of hydrogen if successful. Another novel concept is an integrated biofuel-feedlot facility where animal feed is a coproduct of biofuel production and AD is used to augment power generation.…”