Advanced anaerobic bioconversion of lignocellulosic waste for bioregenerative life support following thermal water treatment and biodegradation by Fibrobacter succinogenes.
The feasibility of nearly-complete conversion of lignocellulosic waste (70% food crops, 20% faecal matter and 10% green algae) into biogas was investigated in the context of a life support project. The treatment comprised a series of processes, i.e., a mesophilic laboratory scale CSTR (continuously stirred tank reactor), an upflow biofilm reactor, a fiber liquefaction reactor employing the rumen bacterium Fibrobacter succinogenes and a hydrothermolysis system in near-critical water. By the one-stage CSTR, a biogas yield of 75% with a specific biogas production of 0.37 l biogas g(-1) VSS (volatile suspended solids) added at a RT (hydraulic retention time) of 20-25 d was obtained. Biogas yields could not be increased considerably at higher RT, indicating the depletion of readily available substrate after 25 d. The solids present in the CSTR-effluent were subsequently treated in two ways. Hydrothermal treatment (T approximately 310-350 degrees C, p approximately 240 bar) resulted in effective carbon liquefaction (50-60% without and 83% with carbon dioxide saturation) and complete sanitation of the residue. Application of the cellulolytic Fibrobacter succinogenes converted remaining cellulose contained in the CSTR-effluent into acetate and propionate mainly. Subsequent anaerobic digestion of the hydrothermolysis and the Fibrobacter hydrolysates allowed conversion of 48-60% and 30%, respectively. Thus, the total process yielded biogas corresponding with conversions up to 90% of the original organic matter. It appears that particularly mesophilic digestion in conjunction with hydrothermolysis at near-critical conditions offers interesting features for (nearly) complete and hygienic carbon and energy recovery from human waste in a bioregenerative life support context.
Lissens
Geert
G
Laboratory of Microbial Ecology and Technology, Ghent University, Coupure L 653, B-9000 Ghent, Belgium. geert.lissens@ugent.be
Verstraete
Willy
W
Albrecht
Tobias
T
Brunner
Gerd
G
Creuly
Catherine
C
Seon
Jerome
J
Dussap
Gilles
G
Lasseur
Christophe
C
D000693:Anaerobiosis; D001673:Biodegradation, Environmental; D002482:Cellulose / Q000378:metabolism*; D005285:Fermentation; D045848:Fibrobacter / Q000378:metabolism*; D006358:Hot Temperature; D008031:Lignin / Q000378:metabolism*; D011312:Pressure; D014871:Water Microbiology
C036909:lignocellulose; D002482:Cellulose; D008031:Lignin