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Photo: quasar energy group

Photo: quasar energy group

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Anaerobic digestion is a process where bacteria break down organic matter, such as manure, in the absence of oxygen. The anaerobic digestion process generates biogas that is composed mostly of methane, which can be used as an energy source (e.g., heat or electricity generation). Codigestion refers to the simultaneous anaerobic digestion of multiple organic wastes in one digester. Codigestion is used to increase methane production from low-yielding or difficult to digest materials (i.e., feedstocks). For the codigestion process, care must be taken to select compatible feedstocks that enhance methane production (and to avoid materials that may inhibit methane generation). In addition, an existing anaerobic digester system must be able to handle the significant increase in methane output that is common with codigestion.

In agriculture, codigestion is often used to increase methane production from the anaerobic digestion of manure. There are multiple choices for codigestion feedstocks, including restaurant or cafeteria food wastes; food processing wastes or byproducts; fats, oil and grease (FOG) from restaurant grease traps; energy crops; crop residues; and others. Codigestion of various organic feedstocks may enhance the biogas and methane production from an anaerobic digester. The Codigestion Fact Sheet (PDF) (3 pp, 422K) discusses factors that should be considered when selecting a feedstock.

AgSTAR also has compiled resources for those interested in pursuing a codigestion anaerobic digestion system. Use the information below to determine the feasibility of a codigestion system for your facility. Additionally, AgSTAR has a discussion of permitting requirements on the Permitting Practices page.

Methods for Testing Potential Codigestion Feedstocks

Information on Carbon to Nitrogen (C:N) Ratios

Basics of Energy Production through Anaerobic Digestion of Livestock Manure (PDF) (6 pp, 926 KB), Exit EPA Disclaimer Department of Agricultural and Biological Engineering, Purdue University

Characteristics of raw materials for on-farm composting, Exit EPA Disclaimer Natural Resource, Agriculture, and Engineering Service, Cornell University

Materials and methods to ensure quality compost: carbon-nitrogen relationships, Exit EPA Disclaimer Washington State University

The Carbon/Nitrogen Ratio, Exit EPA Disclaimer The Humanure Handbook

A Balancing Act (Carbon-Nitrogen Ratios), Exit EPA Disclaimer Composting101.com

Laboratories that Conduct Testing of Anaerobic Digester Feedstocks

Organization Contact Phone
Cornell University Manure Management Program * Curt Gooch (cag26@cornell.edu) 607-255-2088
Iowa State University Agricultural Waste Management Laboratory Dan Andersen (dsa@iastate.edu) 515-294-4167
Marquette University Water Quality Center Dan Zitomer (Daniel.zitomer@mu.edu) 414-288-5733
Michigan State University Anaerobic Digestion Research and Education Center Dana Kirk (kirkdana@msu.edu) 517-432-6530
Ohio State University Bioproducts and Bioenergy Research Laboratory Yebo Li (li.851@osu.edu) 330-263-3855
University of California-Davis Bioenvironmental Engineering Research Laboratory Ruihong Zhang (rhzhang@ucdavis.edu) 530-754-9530
University of Wisconsin-Platteville Tim Zauche (zauchet@uwplatte.edu) 608-342-1678

*Research laboratory, testing for public on case-by-case basis

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