Top: Image courtesy U.S. EPA AgSTAR

The U.S. EPA’s AgSTAR program updates its online database of livestock anaerobic digestion (AD) facilities twice a year. Its latest update was in March 2021. In addition to details on AD facilities, AgSTAR also summarizes associated data and trends, including the latest status of existing or planned projects. Here are some highlights:

• 17 manure-based anaerobic digestion (AD) systems came online in 2020, bringing the total number of systems operating in the United States to 273.
• The majority of the 273 operational projects digest dairy manure (221). Hog manure accounts for 45 projects, followed by beef (9) and poultry (8). AgSTAR notes the total exceeds 273 because some systems accept manure from more than one animal type.
• Most of the digester designs in use fall into these 3 categories: Plug flow (36.6%); Complete mix (31.9%); and Covered lagoon (26.0%).
• Approximately 60 additional systems are currently under construction in the U.S., most of which will produce renewable natural gas (RNG). The number of combined heat and power (CHP) projects steadily increased each year from 2000 to 2015, and then began to slightly decline.
• Annual emission reductions resulting from manure-based AD systems have increased from 4.59 million metric tons of carbon dioxide equivalent (MMTCO₂e) in 2019 to 5.00 million MMTCO₂e in 2020.
• Annual energy production from manure-based AD systems has increased from 1.35 million megawatt hours (MWh) equivalent in 2019 to 1.46 million MWh equivalent in 2020.

Because the data are compiled from a variety of voluntary sources, AgSTAR acknowledges it cannot guarantee the accuracy of the information in its Anaerobic Digester Database: “While the Program strives to keep the information as updated and accurate as possible, the database is not exhaustive and may not include data for every AD system on livestock farms in the United States.”