Anaerobic Digestion in US – A Large Biogas Opportunity

Gradual development of Anaerobic Digestion in US states-wide is progressing. The nation is sitting on a very large Biogas Plant, and climate change emissions reduction opportunity! That much is undeniable. We set out to find out what the US government has published about the anaerobic digestion technologies.

Current Number of US Biogas Plants in Use

“The U.S. has over 2,200 sites producing biogas in all 50 states: 250 anaerobic digesters on farms, 1,269 water resource recovery facilities using an anaerobic digester (~860 currently use the biogas they produce), 66 stand-alone systems that digest food waste, and 652 landfill gas projects. For comparison, Europe has over 10,000 operating digesters and some communities are essentially fossil fuel free because of them.”  via The American Biogas Council (last updated by the ABC in April 2018)

Anaerobic Digestion US Potential for Growth

“Biogas Potential in the United States”

Biogas is the gaseous product of anaerobic digestion, a biological process in which microorganisms break down biodegradable material in the absence of oxygen.

Biogas is comprised primarily of methane (50%–70%) and carbon dioxide (30%–50%), with trace amounts of other particulates and contaminants.

It can be produced from various waste sources, including landfill material; animal manure; wastewater; and industrial, institutional, and commercial organic waste.
Biogas can also be produced from other lignocellulosic biomass (e.g., crop and forest residues, dedicated energy crops) through dry fermentation, co-digestion, or thermo-chemical conversions (e.g., gasification).

Biogas can be combusted to provide heat, electricity, or both.

In addition, it can be upgraded to pure methane, also called biomethane or renewable natural gas, by removing water, carbon dioxide, hydrogen sulphide, and other trace elements.

This upgraded biogas is comparable to conventional natural gas, and thus can be injected into the pipeline grid or used as a transportation fuel in a compressed or liquefied form.

Renewable natural gas, with respect to anaerobic digestion in US states, is considered a “drop-in” fuel for the natural gas vehicles currently on the road and can qualify as an advanced biofuel.

It can also be a source for renewable hydrogen, which can be used in stationary fuel cells and fuel cell electric vehicles.

The methane content of biogas is the usable portion of the gas and determines its calorific value.

The methane potential from landfill material, animal manure, wastewater, and industrial, institutional, and commercial organic waste in the United States is estimated at about 7.9 million tonnes per year, which is equal to about 420 billion cubic feet or 431 trillion British thermal units.

This amount estimated to be available for anaerobic digestion in US jurisdictions, could displace about 5% of current natural gas consumption in the electric power sector and 56% of natural gas consumption in the transportation sector (see EIA 2013).

While this resource potential appears small and easy to overlook given the abundance of relatively inexpensive natural gas, it presents an opportunity for greenhouse gas mitigation (methane is 21 times more potent than carbon dioxide) and production of renewable energy fuel.

These waste resources are under-utilised and considered “low-hanging fruit” in biogas generation if used for anaerobic digestion in US states, thus their use could stimulate further development of the industry in the United States.

This video, and the text above, are based upon the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy (NREL) pdf file, “Biogas Potential in the United States“.

The following is our round-up of information on anaerobic digestion in US states-wide including excerpts from articles about the science of AD, the environmental and economic benefits that can be realized through AD projects, and direct visitors to appropriate …

Permitting and Regulations for Anaerobic Digesters in US States

Anaerobic digesters must meet local, state and federal regulatory and permitting requirements for air, solid waste and water. It is important for all stakeholders working with digesters to be able to find information about permitting and regulations. EPA's AgSTAR program compiled a comprehensive set of requirements for livestock digesters. These requirements also apply to all other types of digesters. via Anaerobic Digestion (AD) | US EPA

Anaerobic Digestion in US – Farm-Based Anaerobic Digestion Practices in the United States

Although some effort has focused on the AD of caged layer poultry manures, the manures from dairy and swine operations tend to be more suitable for farm-based energy conversion.

During the energy crises of the mid- and late 1970s, the search for alternative energy resources Jed to investigation of small- and medium-scale anaerobic digesters developed in India and China to determine whether these technologies were directly transferable to farms in the United States. Unfortunately, although these technologies are useful in providing fuel for cooking and lighting in developing economies, most are much too small to be useful to most American farmers. For example, the typical small-scale digester daily produces about the same amount of energy as contained in 1 gal of propane.

The greater energy requirements of the larger American livestock operations Jed to the design and installation of several demonstration projects that transferred state-of-the-art sewage treatment plant technology to the farm.

Although these first-generation complete-mix digesters generally produced biogas at the target design rate, they suffered from high capital costs and significant O&M requirements. In practical application on the farm, solids settling, scum formation, and grit removal often presented major problems.

[Today, most problems have been solved, but plants must be operated in an expert manner, by trained plant operator's.]

Complete-mix digesters can handle manures with TS concentrations of 3%-10%, and generally can handle substantial manure volumes. The reactor is a large, vertical, poured concrete or steel circular container. The manure is collected in a mixing pit by either a gravity-flow or pump system. If needed, the TS concentration can be diluted, and the manure can be preheated before it is introduced to the digester reactor. The manure is deliberately mixed within the digester reactor. The mixing process creates a homogeneous substrate that prevents the formation of a surface crust and keeps solids in suspension. Mixing and heating improve digester efficiency. Complete-mix digesters operate at either the mesophilic or thermophilic temperatures range. with a HRT as brief as 10-20 days.

A fixed cover is placed over the complete-mix digester to maintain anaerobic conditions and to trap the methane-rich biogas that is produced. The methane is removed from the digester, processed, and transported to the site of end-use application. The most common application for methane produced by the digestion A modern dairy farm complete-mix digester that also recovers valuable fiber process is electricity generation using a modified internal combustion engine. Both the digester and the mixing pit are heated with waste heat from the engine cooling system. Complete-mix digester volumes range considerably from about 3,500-70,000 cubic feet (ft³) This represents daily capacities of about 25,000-500,000 gal of manure/digester. Larger volumes are usually handled by multiple digesters.

The basic plug-flow digester design is a long linear trough, often built below ground level, with an air-tight expandable cover. Manure is collected daily and added to one end of the trough. Each day a new “plug” of manure is added, slowly pushing the other manure down the trough. The size of the plug-flow system is determined by the size of the daily “plug.” As the manure progresses through the trough, it decomposes and produces methane that is trapped in the expandable cover.  … via Farm-Based Anaerobic Digestion Practices in the United States

Useful Links to Information About Anaerobic Digestion in US States

Anaerobic Digestion in the United States By: Curt A. Gooch, P.E. Dairy Housing and Waste Management Engineer Biological and Environmental Engineering Department via Anaerobic Digestion in the United States – Manure

American Biogas Council is the first anaerobic digestion industry association in the United States that represents a full range of anaerobic digestion technologies … via Anaerobic Digestion Companies and Suppliers …

Anaerobic manure digestion for animal agriculture has come into the main stream in recent years in the United States. Other countries in Asia and Europe have used … via Energy from Waste: Anaerobic Manure Digestion

SMALL-SCALE ANAEROBIC DIGESTION IN THE UNITED STATES: DESIGN OPTIONS AND FINANCIAL VIABILITY S. Lansing and K. Klavon Department of Environmental Science and Technology via SMALL-SCALE ANAEROBIC DIGESTION IN THE UNITED STATES …

… biosolids anaerobic digestion in the United States. … Treatment Plants with Anaerobic Digestion … Wastewater Treatment Plants with Anaerobic … via U.S. Wastewater Treatment Plants with Anaerobic Digestion

Anaerobic Digestion jobs in United States. 1 job to view and apply for now with Energy Jobline via Anaerobic Digestion jobs in United States – energyjobline.com

Methane Creation from Anaerobic Digestion . … Since a quarter of the Earth’s known coal resources are located in the United States, coal is the via Methane Creation from Anaerobic Digestion

The Benefits of Anaerobic Digestion of Food Waste . At Wastewater Treatment Facilities . Why Anaerobic Digestion? Anaerobic digestion occurs naturally, in the absence … via The Benefits of Anaerobic Digestion of Food Waste – US EPA