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

PEI designs and manufactures Biogas Processing Systems (Compressor Skids, Blower Skids, Chiller Skids) to extract / receive waste gases from landfills, digesters, and other sources. Systems provide maintainable inlet and discharge pressures to satisfy process requirements as well as gas stream moisture removal and temperature conditioning. Systems range from basic…
Clarke Energy is an authorized distributor and service provider for Techno Project Industriale’s (TPI’s) biogas upgrading plants. These include both membrane and selective solvent-based washing systems. With Clarke Energy’s engineering, procurement, construction and aftersales support capabilities we are able to offer full biogas upgrading solutions to our customers along with…
Achieve environmental performance goals without sacrificing economic results The composition of biogas varies widely, but typically includes methane, carbon dioxide, hydrogen sulfide (H2S), water vapor, and oxygen. Hydrogen sulfide and oxygen create corrosion and safety hazards to infrastructure, including natural gas pipelines. To sell biogas as renewable natural gas (RNG),…
The “solid” and simple solution to sour gas treatment to protect equipment and pipe Sulfur Sentinel™ is an all-in-one solution for cost-effectively treating H2S at oil and gas well sites. It uses a simple but highly effective dry iron oxide scavenger to safely remove hydrogen sulfide from the gas stream.…
Connection to the natural gas grid is not always possible. Liquid renewable natural gas is the solution where there are logistical constraints. Liquefied RNG, in fact, is not only easily transportable to its point of use but, thanks to its density, three times higher than that of compressed natural gas,…
RNG (renewable natural gas) is obtained by putting raw biogas through a purification process called upgrading. Raw biogas can be obtained from anaerobic digestion of various raw materials including agricultural biomass (by-products, agricultural waste and animal waste). Once the biogas-to-RNG upgrading has been carried out, it must be refined, in…
Renewable electrical and thermal energy from organic residues. Biogas is a natural fuel that is obtained through anaerobic digestion, i.e. bacterial fermentation that takes place in the absence of oxygen of organic residues from plant or animal residues. About 50-70% of the biogas produced is made up of methane and…