Technology Type - Anaerobic Digestion



Technology Strengths,Weaknesses and Critical Indicators

Anaerobic Digester technology:

  • Long usable life and can be run reliably
  • Creates energy and generates environmental credits
  • Requires proper preparation of the feedstock
  • Requires other technologies for energy utilization
  • Requires other technologies for digestate handling
  • Proper feeding & system monitoring is required to avoid system downtime
  • Proven technology for odor control, GHG reduction and pathogen reduction

image/svg+xml Nitrogen Recovery Phosphorus Recovery Storage Reduction GHG Reduction Odor Control Pathogen Reduction Negative Positive NEAT MATRIX - Peer Reviewed P - Documented D - Expert Opinion E P D E P D E

Overall Summary

Primary Application

  • Dairy farms with over 500 cows or farms with meaningful organics for co-digestion.
  • Vacuumed/scraped manure, manure slurries, bedded pack that is diluted with digester effluent.

 Economic/Return on Investment Considerations

  • Economics are almost always a challenge; on a value of renewable energy basis, AD is hard to justify, at present received prices for electricity and gas.
  • AD does provide several non-monetary benefits to a farm (see below).

 Industry Uptake

  • 200 dairy-based U.S. installations and thousands worldwide.

Technology Maturity

  • Refined, standard designs available from multiple technology providers.

Primary Benefits

  • Odor reduction – 70 to 95% reduction of indicator acids.
  • Manure organic matter reduction – 35%.
  • Renewable electrical energy production – 2,000 kWh/cow possible each year.
  • Pathogen reduction – 90%+ elimination of fecal coliform organisms as a typical indicator pathogen.
  • Greenhouse gas emission reduction – amount varies by location and farm-specific, but reductions can be large, on the order of 67%+.
  • Nutrient preservation/transformation – key crop nutrients in manure are not consumed by AD and the nutrient form is more plant available than when not digested.
  • Contributes to society’s goal for organic landfill diversion – co-digestion easily achieved enhancing above benefits.

Secondary Benefits

  • Pre-treatment for tertiary treatments like ammonia stripping.
  • Renewable thermal heat production – 13,500 Btu’s/cow or more possible each year.
  • Less impact on water quality.
  • Increased crop yields possible.

How it Works

  • Raw or pre-treated manure is conveyed into a gas tight vessel on a regular basis (daily or more often) that operates at a set temperature (38 ⁰C in most cases).
  • Naturally occurring microbes in manure break solids down into energy-rich biogas.
  • Biogas is used to fuel engine-generators to make electricity or is cleaned to make a natural gas replacement.
  • Some of the produced gas, or heat produced by an engine-generator set is used to heat the digester making it a net energy production system.

 Pre-treatment and/or Post-treatment Required

  • Pre-treatment not required when organic material is used to bed stalls and/or when manure is not substantially diluted. Pretreatment to remove bedding sand is required with sand-bedded stalls.
  • Pre-treatment may be used to remove excess moisture from influent from barns were hydraulic flushing is used.
  • Post-treatment not required but may be employed based on overall goals of the manure treatment system.

Limitations

  • Does not reduce volume.
  • Does not work well with raw manure containing bedding sand.
  • Does not work with highly diluted manure due to cost and heat demands for a large vessel.

Other Considerations

  • Currently, most systems are farmer managed, more consistent results may be achieved by dedicated operators.

References
Gooch, C., Pronto, J., & Labatut, R. (2011). Evaluation of Seven On-Farm Anaerobic Digestion Systems Based on the ASERTTI Monitoring Protocol: Consolidated Report and Findings Cornell University.

 

Holly, M. A., Larson, R. A., Powell, J. M., Ruark, M. D., & Aguirre-Villegas, H. (2017). Greenhouse gas and ammonia emissions from digested and separated dairy manure during storage and after land application. Agriculture, Ecosystems & Environment, 239, 410-419.

 

Massé, D. I., Talbot, G., & Gilbert, Y. (2011). On farm biogas production: A method to reduce GHG emissions and develop more sustainable livestock operations. Animal feed science and technology, 166, 436-445.

 

Möller, K., & Müller, T. (2012). Effects of anaerobic digestion on digestate nutrient availability and crop growth: a review. Engineering in Life Sciences, 12(3), 242-257.

 

Owen, J. J., & Silver, W. L. (2015). Greenhouse gas emissions from dairy manure management: a review of fieldbased studies. Global change biology, 21(2), 550-565.

 

Page, L. H., Ni, J. Q., Heber, A. J., Mosier, N. S., Liu, X., Joo, H. S., ... & Harrison, J. H. (2014). Characteristics of volatile fatty acids in stored dairy manure before and after anaerobic digestion. biosystems engineering, 118, 16-28.

 

Pain, B.F., Misselbrook, T.H., Clarkson, C.R. & Rees, Y.J. (1990). Odour and ammonia emissions following the spreading of anaerobically-digested pig slurry on grassland. Biol. Wastes 34:259-267.

 

Summers, M., Williams D. (2013). Energy and environmental performance of six dairy digester systems in California. A final report for the Energy, Economic, and Environmental Performance of Dairy Bio-power and Bio-methane Systems project (contract number PIR-08-041) conducted by Summers Consulting, LLC. CED-500-2014-001-VI, March 2013.

 

Topper, P. A., Graves, R. E., & Richard, T. (2006). The fate of nutrients and pathogens during anaerobic digestion of dairy manure. Lehman (PA): Penn State University. College of Agricultural Science, Cooperative Extension Bulletin G, 71.

 

Welsh, F.W., Schulte, D.D., Kroeker, E.J. & Lapp, H.M. (1977). The effect of anaerobic digestion upon swine manure odors. Can. Agric. Eng. 19:122-126. Wilkie, A. C. (2000). Anaerobic digestion: holistic bioprocessing of animal manures. Gainesville, FL, University of Florida

 

Wright, P. E., Inglis, S. F., Stehman, S. M., & Bonhotal, J. (2003). Reduction of selected pathogens in anaerobic digestion. In Animal, Agricultural and Food Processing Wastes-IX (p. 1). American Society of Agricultural and Biological Engineers.

Technology Providers in order of 9 - Point Scoring System