California's Carbon Manure Math Faces Scrutiny

California's climate policy, which incentivizes cattle farmers to convert methane from manure into natural gas, is facing significant criticism for its effectiveness in reducing atmospheric warming. This program, designed to encourage the dairy sector to produce a less potent greenhouse gas, has become highly popular due to lucrative subsidies. However, a growing body of research indicates that such carbon offsetting and trading schemes often overestimate the actual emissions reductions achieved.

The dairy program, in particular, is highlighted as an example of how these systems can obscure the impacts of different greenhouse gases, potentially leading to increased warming in the future. Despite these concerns, California regulators decided in 2024 to extend parts of the program beyond 2050. Furthermore, a recent proposal by the state's Air Resources Board could direct millions of additional dollars to dairy farmers by easing restrictions on major greenhouse gas producers.

The system operates by requiring the transportation fuels industry to reduce carbon dioxide levels in its products or purchase credits from entities that cut fuel emissions, including cattle farmers. Dairies typically store manure in open lagoons, where it produces methane. By installing anaerobic digesters, farmers can capture this biogas, which is then processed into natural gas. This process is intended to reduce the amount of methane released directly into the atmosphere, as methane is a significantly more potent greenhouse gas than carbon dioxide over a 20-year period.