A detailed roadmap for how to meet and exceed the US pledge to cut methane emissions has been published in a new paper in the peer-reviewed journal Biofuels, Bioproducts, and Biorefining (BioFPR). The paper by Michael Lerner, “How the USA can feasibly cut methane emissions 30% by 2030: anaerobic digestion of organic waste and various measures in oil and gas production,” is based on the NGO Energy Vision’s recent report “Meeting the Methane Challenge: How the U.S. Can Reach Its 2030 Goal,” which Lerner researched and wrote.
The Global Methane Pledge commits the U.S. and 157 other signatories to the goal of cutting methane emissions at least 30% by 2030 (or “30×30” for short) to keep global warming within 1.5 degrees Celsius and prevent the worst effects of “runaway” climate change. Methane is 87 times more potent as a greenhouse gas than carbon dioxide over 20 years, and it has already caused a third of modern global warming. This spring, EPA’s New Source Performance Standards (NSPS) for oil and gas production took effect, tightening methane regulations across millions of pieces of equipment.
The BioFPR paper assesses the NSPS and a range of other current and potential measures to cut methane emissions in the U.S. oil and gas sector, such as plugging abandoned oil and gas wells and “stripper wells.” Stopping methane leaks is crucial, and relatively inexpensive, but as Lerner points out the NSPS would get us little more than halfway to the 30×30 goal. The paper therefore lays out a complimentary, cost-effective strategy which could go the rest of the way to meeting and exceeding the 30×30 goal: anaerobic digestion (AD) of organic waste.
“New Source Performance Standards (NSPS) for oil and gas production by 2029 would cut 17.5% of total U.S. methane emissions annually, at a cumulative capex of $20.7 billion from 2024 to 2029,” Lerner writes. “Together, the 13.6% cut from food waste and manure ADs and the 17.5% cut from full NSPS compliance would amount to a 31.5% reduction, exceeding the 30 × 30 goal. Greater clarity from the federal government on funding eligibility and additional incentives would accelerate the buildout of ADs.”
Food waste and agricultural manure release methane biogases as they decompose, but instead of escaping into the atmosphere, these biogases can be captured in sealed tanks called anaerobic digesters (ADs) and converted to renewable energy.
Methane biogases captured in ADs can be used to generate local power and heat, for example to run dairy operations. Or they can be refined into renewable natural gas (RNG), the lowest-carbon fuel available today. RNG fueI is especially beneficial when used in applications which can’t readily be electrified: older homes and buildings, heavy industries, and heavy-duty trucks and buses. RNG is chemically similar to fossil natural gas and can be used in all the same ways. But unlike fossil gas, RNG made in ADs involves no fracking or other leaky extraction and has drastically lower carbon emissions. In fact, when made from food scraps or manure, it is “net carbon-negative” on a lifecycle basis. This means more greenhouse gas emissions are captured during fuel production than are emitted when the fuel is burned – a big net gain for the climate.
The paper finds that the most cost-effective option in organic waste methane abatement is keeping food waste out of landfills and processing it in ADs. Landfills are major methane emitters, and food waste accounts for most of those emissions. Half of all food currently discarded as waste is edible and should be redistributed. But the other, inedible half is an ideal feedstock for ADs. The second most cost-effective option is processing farm manure in ADs, which lowers agricultural methane emissions and provides another revenue source for farmers.
Building some 700 new ADs to process municipal and industrial food waste as well as about 4,000 new ADs to process dairy and swine manure would cut U.S. methane emissions 13.6%, Lerner finds. The total capital cost of all 4,700 digesters would be about $74 billion, some of which available in tax credits and other financing under the Inflation Reduction Act (IRA). New digesters take two to six years per project to build and could be operational by 2030.
“These numbers speak for themselves,” said Lerner. “ADs are low-hanging fruit that haven’t received the attention they deserve, and that needs to change. While stopping methane leaks from oil and gas operations – a major focus of government – is cheaper and could get us about halfway to the 30×30 goal, the resistance of oil and gas producers threatens to slow progress on that front. The oil and gas industry needs to support the essential transition to the sustainable future the planet needs. Meanwhile, ADs are the missing piece that can get us the rest of the way to 30×30. They are a fully commercial technology and they’re scaling fast, with nearly 100 operational food waste ADs and around 400 operational manure ADs, but we need to see many times those numbers deployed in the next few years. With the incentives provided in the IRA, their growth can be supercharged.”
