10.2190/4HJV-0BNX-Y6RQ-LJ4R 4HJV0BNXY6RQLJ4R 1 Energy Balance for Anaerobic Digestion 183 198 20020509 20020509 20020509 20020509 4HJV0BNXY6RQLJ4R.pdf http://baywood.metapress.com/link.asp?target=contribution&id=4HJV0BNXY6RQLJ4R 3 Steven I. Ojalvo John D. Keenan Energy Center, University of Pennsylvania Department of Civil and Urban Engineering, University of Pennsylvania A model is developed which describes the energy balance of an anaerobic digestion system for energy recovery from organic wastes. The model is used to evaluate the energy efficiency of the process which consists of pre-treatment including primary shredding, magnetic separation, trommel screening, secondary shredding and air classification of the organic fraction; anaerobic digestion yielding methane fuel gas; gas scrubbing for removal of carbon dioxide and hydrogen sulfide; and dewatering of the waste solids. The results indicate that energy efficiencies for the entire process, excluding transportation of input and output materials, of 48 to 65 per cent are possible; and, 20 to 30 per cent are achievable with present technology. The system is relatively insensitive to front-end and back-end power requirements and to the energy needed for digester operation and maintenance. The most significant factor influencing energy conversion efficiency is the rate and degree of completion of the digestion process. L. L. Anderson, Energy Potential From Organic Wastes: A Review of Quantities and Sources, U. S. Bureau of Mines, Information Circular #8549, 1972. A. Poole, The Potential for Energy Recovery From Organic Wastes, Chapter 6, <i>The Energy Conservation Papers</i>, R. H. Williams, (ed.), Ballinger, Cambridge, Mass. (Ford Foundation Energy Policy Project Series), 1975. R. A. Lowe, <i>Energy Conservation Through Improved Solid Waste Management</i>, Office of Solid Waste Management Programs, U. S. EPA, Washington, D. C., 1974. E. K. Dille, Utilization of Municipal Refuse for Recovery of Energy and Other Resources, <i>Earth, Environment and Resources Conference 1974</i>, IEEE Digest of Papers, Lewis Winner, N. Y., 1974. Gilbert Associates, Inc., Refuse Fuel Energy Utilization Systems, <i>Earth Environment, and Resources Conference 1974</i>, IEEE Digest of Papers, Lewis Winner, N. Y., 1974. J. D. Keenan, Two-Stage Methane Production, ASME Preprint No. 74-WA/Ener-11, 1974. A. W. Lawrence and P. L. McCarty, Kinetics of Methane Fermentation in Anaerobic Waste Treatment, Technical Report 75, Dept. of Civil Engineering, Stanford University, 1967. R. G. Kispert and D. L. Wise, <i>Fuel Gas Production from Solid Waste</i>, Dynatech R/D Company, Cambridge, Mass., NSF/RANN 74-111 Final Report, Jan. 1975. Also MIT Reports on Research, 3:4, Dec. 1975, MIT News Office, Room 5-111, MIT, Cambridge, 02139. J. T. Pfeffer and A. Liebman, <i>Biological Conversion of Organic Refuse to Methane</i>, Illinois University at Urbana, Dept. of Civil Engineering, NSF/RANN 74-068, July 1974. R. Smith, <i>Electrical Power Consumption for Municipal Wastewater Treatment</i>, National Environmental Research Center, Office of Research and Monitoring, U. S. EPA, Program Element IB2043, EPA-R2-73-281, Cincinnati, Ohio, July, 1973. P. L. McCarty, Anaerobic Waste Treatment Fundamentals, <i>Public Works, 95</i>:9, 10, 11, 12, Sept.-Dec, 1964. W. W. Eckenfelder, Jr., <i>Biological Waste Treatment</i>, Pergamon Press, New York, Chapters 7 and 9, 1961. J. T. Pfeffer, Anaerobic Processing of Organic Refuse, Illinois University at Urbana, U. S. EPA Grant No. EPA-R-800776, Jan., 1973. J. Griffiths, <i>The Practice of Sludge Digestion-Waste Treatment</i>, Pergamon Press, New York, 1960. S. I. Ojalvo, <i>An Energy Balance for the Anaerobic Digestion of Garbage and Sewage</i>, M. S. Thesis, Energy Management and Policy, University of Pennsylvania, 121 pp., 1976. J. D. Keenan, Multiple Staged Methane Recovery from Solid Wastes, in preparation, 1976.