The latest farm digester data (09/30/2021) from the U.S. EPA’s AgSTAR program finds that 44 anaerobic digestion (AD) systems on U.S. farms have come online this year, all producing renewable natural gas (RNG). Thirty-six of these systems are at dairy farms in California, three at swine farms in Missouri, and five at dairies in Idaho and Vermont. This brings the total number of U.S. manure-based AD systems operating to 317. Approximately 38 additional systems are currently under construction, most of which will produce RNG, either for pipeline injection or use as vehicle fuel. Seven existing power generation projects intending to switch to RNG production are now in the construction phase, and several more RNG project conversions are in the planning and development stages.
Different types of AD systems are utilized: covered lagoons lead with 112 installations (35.3% of the total), followed closely by plug flow designs (99 or 31.2%) and complete mix (91 or 28.7%). Although there has been a slight decline over the past 6 years, the most common end use of biogas from manure-based AD systems since 2000 is combined heat and power (CHP), followed by electricity. In 2021, manure-based AD systems are expected to generate the equivalent of approximately 1.73 million megawatt-hours (MWh) of electricity. More >>