AD Support

Technology Strengths, Weaknesses and Critical Indicators

Anaerobic Digester Associated Technology:

NOTE: There are several technology types that are used as part of an integrated manure management system that includes an anaerobic digester and are not applicable to manure management in other cases. The impact of these technologies on the critical indicators are represented as those of an entire anaerobic digester system.


  • 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

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. Pre-treatment 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.


  • 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.

Technology Providers in order of 9-Point Scoring System

Warren’s epoxy coating system is a quick and effective rehabilitation method that adds valuable service life to anaerobic digester tanks with minimal impact on their operations.   Warren’s approved applicators use 301-14 epoxy to repair tank’s concrete surfaces. Before coating the walls, the team sandblasted and water blasted to remove…
W.W. Williams delivers with world-class emissions-certified products from MTU Onsite Energy for a wide variety of applications. Whether it’s continuous, standby, prime or combined heat and power you need – consider it done.  
The installation of emission control devices on biogas engines is becoming increasingly common. Just as an engine will suffer with increased biogas contaminants, so too will the emission control system. GraniteFuel provides high efficiency biogas conditioning systems to process raw gas to levels ideal for optimum engine and emissions system…
Compact in size, BayoTech systems tap into existing natural gas pipelines or co-located biogas resources. Systems produce 1,000 kilograms of hydrogen per day right at the point of use, eliminating the cost and emissions of liquification and transportation.   When paired with renewable natural gas (“RNG”) and/or carbon capture, BayoTech’s…
Agra Energy’s MICRO Gas-To-Liquid (GTL) UNIT is prefabricated and transportable. Installed at a farm location, this unit will process the “feedstock methane” from a herd of dairy cows. The effluent-waste is converted into about 25 barrels per day diesel, naphtha and jet fuel products. It is on the scale of…
BGX BiostreamTM: Introducing Xebec’s New Biogas Upgrading Solution Biogas projects have been taking off all over the world. Despite the growing number of projects, small-scale plants still have limited options. Most available systems are simply not viable for farms, small biogas plants that process agricultural and industrial organic wastes, wastewater…
The Vanguard Renewables solves organic waste disposal challenges and supports the American Farmer. Their scalable, closed-loop anaerobic digestion process converts the energy potential in farm and food waste into Renewable Electricity or Renewable Natural Gas. They strive to be the premier farm-based anaerobic digestion plant owner/operator in the United States…