LCFS dairy credits apply 25x methane GWP against 12-year atmospheric lifetime

The Low Carbon Fuel Standard requires transportation fuel producers to meet declining carbon intensity targets or purchase credits from dairy operators installing anaerobic digesters. Digesters capture methane from manure lagoons and convert it to pipeline gas. CARB extended credit eligibility past 2050 and proposed additional payments in 2024 while maintaining the original global warming potential factor.

Aaron Smith documented that the 25x multiplier allows one average biogas vehicle to generate credits covering 26 equivalent gasoline vehicles. Methane persists roughly 12 years before oxidizing to CO2. The 100-year GWP therefore overstates near-term benefit relative to the permanent CO2 released when the captured gas is later combusted. Primary data come from CARB LCFS regulation documents and Smith’s UC Berkeley analysis of credit volumes.

The accounting error connects to repeated failures across offset programs where short-lived pollutant reductions substitute for long-lived stock pollutants. Regulators accepted the 25x value despite IPCC updates showing methane’s adjusted 100-year GWP near 27-30 and its effective 20-year impact exceeding 80. Resulting credit prices continue to subsidize infrastructure that trades temporary methane avoidance for additional cumulative CO2.

CARB’s 2024 proposal would direct millions more to digester projects while easing compliance burdens on petroleum suppliers. No mechanism exists within current LCFS rules to reconcile the differing atmospheric lifetimes once credits are issued.