California's dairy methane swap swaps short-term gain for centuries of warming

California’s Low Carbon Fuel Standard (LCFS) was designed to lower transportation emissions, but it has spawned a lucrative side industry: dairy methane capture. The state pays cattle farmers to install anaerobic digesters that trap methane from manure lagoons. That biogas is then converted to natural gas and sold as fuel for vehicles or power plants. Petroleum companies buy LCFS credits from these farmers instead of cleaning up their own fuels. According to UC Berkeley’s Aaron Smith, adding just one biogas-powered vehicle produces enough credits to offset the deficits of 26 gasoline cars. The program has become wildly popular because the subsidies are extremely profitable—California regulators extended it beyond 2050 in 2024 and are considering even more payments.

But researchers warn the carbon math doesn’t add up for the atmosphere. California assumes methane has 25 times the warming effect of CO₂ over 100 years (the 100-year GWP). In reality, methane is extremely potent but breaks down within a couple of decades, while CO₂ accumulates and warms the planet for millennia. By swapping captured methane (short-lived potent gas) for burned natural gas (CO₂, long-lived), the program reduces short-term warming at the cost of near-permanent CO₂ increases. This approach locks in long-term warming, as multiple studies have shown. The core problem: we need to slash both methane and CO₂, not trade one for the other.