A Unit of Fuel Is Not a Methane Cut

In 2022, renewable natural gas that qualified for federal cellulosic fuel credits totaled 55 billion cubic feet. That was about 84 percent of all natural gas used as transportation fuel in the United States, but only about 0.2 percent of total U.S. natural gas consumption, according to the U.S. Energy Information Administration. Source: https://www.eia.gov/todayinenergy/detail.php?id=61045

That number captures the whole tension. RNG can dominate a narrow credit category while barely moving the national gas system. It can be important and limited at the same time. The mistake is treating a unit of fuel as if it were automatically the best unit of methane policy.

What the Fuel System Measures

The federal Renewable Fuel Standard was built around renewable fuel volume. EPA says the program requires a certain volume of renewable fuel to replace or reduce fossil fuel in transportation fuel, heating oil, or jet fuel. Compliance runs through Renewable Identification Numbers, or RINs, which are generally generated when renewable fuel is produced and used for transportation purposes. Source: https://www.epa.gov/renewable-fuel-standard/overview-renewable-fuel-standard-program

EPA's approved pathway table includes renewable compressed natural gas and renewable liquefied natural gas from biogas produced at landfills, wastewater treatment digesters, agricultural digesters, and separated municipal solid waste digesters. Those pathways can qualify for cellulosic biofuel treatment. Source: https://www.epa.gov/renewable-fuel-standard/approved-pathways-renewable-fuel

California's Low Carbon Fuel Standard works differently, but it still starts with fuel pathways. CARB says transportation fuels need a carbon intensity score to participate in pathway based crediting. Its guidance also includes reporting and recordkeeping for natural gas and book and claim accounting for biomethane. Sources: https://ww2.arb.ca.gov/our-work/programs/low-carbon-fuel-standard/lcfs-credit-generation-opportunities and https://ww2.arb.ca.gov/our-work/programs/low-carbon-fuel-standard/lcfs-guidance-documents-user-guides-and-faqs

What the Atmosphere Measures

The atmosphere does not track RINs, credit prices, or fuel pathway applications. It tracks molecules. A methane molecule either reaches the air or it does not. If it is destroyed, the near term warming damage is sharply reduced. If it escapes, the fact that a different molecule became fuel somewhere else does not undo the physical release.

That is why the policy unit matters. When incentives are tied to fuel output, the system naturally favors projects that can produce, condition, move, and document a saleable energy product. When incentives are tied to verified methane destruction, the system can reach sites where the climate problem is real but the fuel business is not.

This is not an argument against RNG. It is an argument against pretending RNG is the only legitimate outcome. Large landfills, wastewater plants, and big livestock operations may be good candidates for fuel projects. But a mid size dairy twelve miles from a pipeline is not failing the climate test by lacking interconnection. The policy test is failing the farm.

The Extra Steps Have a Cost

Turning biogas into pipeline quality RNG is a real industrial process. California's Public Utilities Commission defines biomethane, also called RNG, as biogas that is captured and then purified to a quality suitable for injection into an investor owned utility gas pipeline. Source: https://www.cpuc.ca.gov/industries-and-topics/natural-gas/renewable-gas

That purification and injection requirement is not a footnote. It means gas cleanup, compression, metering, interconnection, contract administration, and ongoing reporting. At the right scale, those steps can make sense. At the wrong scale, they turn a methane problem into a financing problem.

Cap and flare is simpler because it stops at the climate event. Capture the biogas, measure it, destroy the methane, and document the result. There is still equipment, maintenance, and verification. There is still a need for strong monitoring. But the project does not have to become a gas marketer before the atmosphere receives the benefit.

The Fair Comparison

A fair RNG comparison is not fuel versus nothing. It is fuel project versus direct destruction for the same site. How much methane will be destroyed? How soon? At what cost per ton? How much public or ratepayer money is needed? How much methane risk is added by processing and transport?

Those questions produce a more honest answer than a fuel volume target alone. For some sites, RNG will win. For many smaller sites, direct destruction will win. The point is not to crown one technology everywhere. The point is to let the measured climate outcome decide.

Policy should pay for the thing the public is actually buying: methane kept out of the air. Fuel production can be a bonus where it works. It should not be the gatekeeper that decides whether a farmer, landfill, or wastewater plant gets help reducing emissions. A unit of fuel is useful. A verified methane cut is the climate result. We should stop confusing the two.