Anaerobic Digestion (Biogas)

Anaerobic digestion (AD) is a process in which organic matter from wet organic wastes (i.e. liquid manure, food processing wastes, etc.) is converted into methane by bacteria in the absence of oxygen. The methane is then collected and may be used to generate combined heat and power (CHP) or renewable methane fuel (RNG). In addition, the AD process creates potentially valuable by-products (i.e. fibrous solids/peat moss replacement and liquid wastewater rich in bio-available nutrients) while also alleviating key environmental concerns. These include reduction in odor, indicator pathogens, and greenhouse gas emissions as compared to non-AD baselines.

CSANR views AD as important technology for organic management but more importantly as a core unit operation in a grander vision of a bio-refinery. Within the bio-refinery approach multiple wastestreams are collected, separated and selectively treated for more efficient processing while also harnessing interconnected synergies and production of multiple co-products and revenue streams.  CSANR has supported extensive efforts in improving AD technology for:

  • multiple organic wastes,
  • co-digestion of manure with outside organics,
  • development and demonstration of novel nutrient recovery technologies for production of concentrated nutrient co-products,
  • development and demonstration of novel biogas purification systems,
  • integration of pyrolysis/chars within an AD platform,
  • reporting of reliable techno-economic and feasibility studies related to farm-based AD projects, and
  • technical/extension/outreach support for farmers, rural communities, project developers, and engaged agencies.

See also our Small-Scale Biogas page.

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Featured Publications

Increasing the Economic Value and Sustainability of Washington’s Agriculture Sector Through Industrial Symbiosis: A Report to the Washington Legislature (PDF)

Roth, R., M.P. Wolcott, G.G. Yorgey, J.L. Male, T. Sturdevant, D. Camenzind, F. Pierobon, J. Padowski, C.E. Kruger, A. Whittemore,

T. Carroll, K. Jensen, S. Moddemeyer, and A. Ybarra. 2023. Increasing the Economic Value and Sustainability of Washington’s Agricultural Sector through Industrial Symbiosis: A report to the Washington Legislature. WSU Center for Sustaining Agriculture and Natural Resources, WSU Institute for Northwest Energy Futures, Richland, WA.

Video: Recovering Nutrients from Manure – New Tools for Maintaining Air and Water Quality

Hall, S., and G.G. Yorgey. 2017.  Produced by CAHNRS Communications. Washington State University, Pullman, WA.  This video profiles two Washington State dairies – Edaleen Dairy and Royal Dairy – who have implemented new technologies that partition, and in some cases recover, some of the nitrogen and phosphorus in manure. The video discusses both the potential that […]

Soil Amendments (PDF)

Yorgey, G., W. Pan, R. Awale, S. Machado, A. Bary. 2017. Chapter 7 In Yorgey, G. and C. Kruger, eds. Advances in Dryland Production Systems in the Pacific Northwest. Washington State University Extension, Pullman, WA.

Digested Fiber Solids: Methods for Adding Value

Jim Jensen , Dr. Craig Frear , Dr. Jingwei Ma , Chad Kruger , Rita L. Hummel , Georgine Yorgey , WSU Fact Sheet FS235E. November 2016. This publication describes the composition and separation process for fibrous solids that result from the digestion of dairy manures. It also reviews both current and future potential uses of fiber. […]

Considerations for Incorporating Co-Digestion on Dairy Farms

Kennedy, N., G. Yorgey, C. Frear, and C.E. Kruger. July 2016. WSU Fact Sheet EM088E. This publication discusses the impacts of incorporating co-digestion at dairy-based anaerobic digesters. That is, mixing manure with non-manure waste in anaerobic digesters. This information is based on stakeholder perspectives and a literature review of infrastructure, operational upgrades, and related costs and revenues […]

Anaerobic Digestion Effluents and Processes: The Basics

S. M. Mitchell, N. Kennedy, J. Ma, G. Yorgey, C. Kruger,  J. L. Ullman, C. Frear.  Sept 2015. WSU Fact Sheet FS171E. This fact sheet reviews the basic elements of anaerobic digestion and the process used by digesters, including the types of digesters, biochemistry of influents and effluents, laboratory evaluations and optimizing anaerobic digesting through modeling. This fact […]

On-Farm Co-Digestion of Dairy Manure with High-Energy Organics

N. Kennedy, G. Yorgey, C. Frear, C. Kruger 2015. WSU Fact Sheet FS172E. This publication focuses on pre-consumer food wastes that can sustainably be used as substrates for co-digestion with dairy manure and increase the value of co-products. Topics covered include complementary and problematic substrates, the substrate procurement process, regulations, and solutions for co-digestion processing issues. This fact sheet […]

Biogas Upgrading on Dairy Digesters

N. Kennedy, G. Yorgey, C. Frear, D. Evans, J. Jensen, C. Kruger. 2015. WSU Fact Sheet FS180E.  This fact discusses the chemical composition of renewable natural gas, the most appropriate end-use options for dairy digesters, and some of the more common techniques used to clean biogas to RNG quality at dairy digesters. This fact sheet is part […]

Anaerobic Digester Project and System Modifications: An Economic Analysis

Galinato, S., C. Kruger, and C. Frear. 2015. WSU Extension Publication EM090E. This publication introduces readers to key concerns regarding the profitability of anaerobic digestion systems and examines the potential profitability of three alternative anaerobic digester systems: (a) combined heat and power, which is the baseline system; (b) boiler as a substitute for combined heat and power; […]

Anaerobic Digester System Enterprise Budget Calculator

Astill, G., R. Shumway, and C. Frear. 2016. This tool calculates the economic value of investment under a variety of technology and price scenarios for an AD system. The budget calculator includes options for anaerobic digestion, codigestion, compressed natural gas, combined heat and power, environmental credits, fiber solids separation, phosphorous solids separation, struvite precipitation, ammonium sulfate […]

The Dairy Manure Biorefinery

Graphic poster depicting the biorefinery concept. Developed by Nick Kennedy, Jingwei Ma, Craig Frear, Georgine Yorgey, Tara Zimmerman, Chad Kruger, and Jim Jensen.

Additional Publications

Economics of Dairy Digesters in Washington State

Kennedy, N. 2013.  BioCycle Magazine. Feasibility study supports a shift from the conventional CHP model to a renewable natural gas (RNG) model that takes advantage of the accelerating move to natural gas fuels in the transportation sector.

Browse all Anaerobic Digestion (Biogas) Publications

External Links

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