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Energy recovery from the effluent of plants anaerobically digesting urban solid waste

Technical Report ·
DOI:https://doi.org/10.2172/6339289· OSTI ID:6339289

The program objective was to study the parameters of concentration, time, temperature, and pH to find optimum conditions for enzymatically converting unreacted cellulose in the effluent of an anaerobic digester to glucose for ultimate conversion to methane, and then to project the economics to a 100-tons-per-day plant. The data presented illustrate the amount of cellulose hydrolysis (in percent solubilized mass) for enzyme concentrations from 5 to 1000 C/sub 1/U/gram of substrate using either filter paper or anaerobically digested municipal solid waste (MSW) reacted over periods of time of from 0 to 72 hours. With an active bacterial culture present, the optimum temperature for the hydrolysis reaction was found to be 40/sup 0/C. The feasibility of recycling enzymes by ultrafilter capture was studied and shows that the recovered enzyme is not denatured by any of several possible enzyme loss mechanisms - chemical, physical, or biological. Although rather stable enzyme-substrate complexes seem to be formed, various techniques permit a 55% enzyme recovery. Posttreatment of digested MSW by cellulase enzymes produces nearly a threefold increase in biomethanation. However, the value of the additional methane produced in the process as studied is not sufficient to support the cost of enzymes. The feasibility of enzymatic hydrolysis as a biomethanation process step requires further process optimization or an entirely different process concept.

Research Organization:
Systems Technology Corp., Xenia, OH (USA)
DOE Contract Number:
AC01-78CS20451
OSTI ID:
6339289
Report Number(s):
DOE/CS/20451-T1; ON: DE83009183
Country of Publication:
United States
Language:
English