Rapid Growth in Renewable Natural Gas, Which Could Significantly Cut Methane Emissions

­The sustainable energy NGO Energy Vision (EV) today released its annual assessment of the US renewable natural gas (RNG) industry, conducted in collaboration with the US Department of Energy’s Argonne National Laboratory.  It shows rapid growth in projects producing RNG last year, and a potential pathway to deep methane emissions cuts at a time when the latest Global Methane Budget shows emissions rising rapidly.

The new EV/ANL assessment tracks RNG production facilities where part or all of the output is used as transportation fuel.  RNG is the lowest-carbon transportation fuel available today. It cuts the greenhouse gas emissions from heavy duty trucks and buses to near zero by displacing carbon-intensive diesel fuel.

The latest assessment finds that by the end of 2023 (the most recent period for which survey data is available) there were 542 RNG production facilities, at least some of whose output is or will be used in transportation. These include 305 facilities in operation as well as 126 under construction, and 111 in various stages of planning. That’s an overall 33.8% increase over the last two years.

At the end of 2023, the 305 operational RNG facilities were able to produce enough fuel to displace nearly 843 million gallons of diesel fuel annually – enough to power 96,900 refuse trucks – more than half of all those on US roadways. That represents a 22% increase in RNG production capacity over the previous two years. With another 237 RNG projects in the pipeline, rapid capacity growth is likely to continue.

RNG growth can significantly cut methane emissions. As organic wastes decompose they emit methane biogases, but instead of allowing these to escape into the atmosphere, they can be captured in airless tanks called “anaerobic digesters” and refined into RNG fuel. According to Argonne National Laboratory’s GREET emissions modeling tool, RNG produced from food waste or farm manure is net carbon-negative over its lifecycle (production, transport and use), i.e., more greenhouse gases are captured (as methane) in producing the fuel than are emitted by vehicles burning it (as CO2). 

“Our data shows rapid growth in the production of renewable natural gas from the methane created by decomposing food and other organic wastes,” said Marianne Mintz, who manages the project for Argonne National Laboratory. “Capturing that methane, using it to displace fossil fuels, and burning it in vehicles significantly cuts greenhouse gas emissions.”

“While the expansion of RNG production in the US documented in this assessment is an important step forward, we need to see much more if we’re to have a real shot at achieving the Global Methane Pledge,” said Matt Tomich, president of Energy Vision. “The US’s domestic RNG production potential is 7 to 12 times greater than current production. Continued growth in the US RNG market could make this buildout possible.”

Cutting methane emissions is critical to limiting climate change. Methane is a potent greenhouse gas that the EPA calls a “climate super pollutant,” 87 times more potent than carbon dioxide over 20 years.  It has already caused about a third of modern warming.In 2021, the United Nation’s Intergovernmental Panel on Climate Change (IPCC) concluded that humans have already irreversibly transformed the Earth’s systems and the global average temperatures have risen by 1.1 degrees Celsius (2 degrees Fahrenheit) since the beginning of the industrial era. Most immediately, to avoid the catastrophic impacts of runaway climate change, global methane emissions had to be cut 30% by 2030. 155 countries including the US have since signed the Global Methane Pledge committing to meet that goal. 

2023’s record high global level of atmospheric methane correlates closely with 2023’s record high temperatures.  While the latest Global Methane Budget indicates methane emissions are rising rapidly and the Global Methane Pledge goal of reducing emissions 30% by 2030 is currently beyond reach, anaerobic digestion offers a new pathway to deep methane emissions cuts.

Another recent Energy Vision report, Meeting the Methane Challenge, found that the U.S. could cut its methane emissions 13.6% by building approximately 4,700 more anaerobic digesters to  process food waste and manure into renewable energy like RNG, plus high-quality soil amendments.  “This would get our country almost halfway to the Methane Pledge goal,” said Energy Vision Founder Joanna Underwood.

According to Energy Vision’s calculations, reaching full U.S. RNG production potential would generate enough fuel to displace over 25% of current U.S. on-road diesel demand (saving 10 billion gallons or more annually), and reduce overall GHG emissions by an estimated 120 million metric tons (CO2e annualized on a lifecycle basis).