Manure solids separator at Brindeiro & Danbom Dairy Farms in Turlock, CA. The separator, which was installed with support from the Alternative Manure Management Program (AMMP), helps reduce methane emissions, enhance efficiency, and allows the dairy to produce organic-certified compost. CalCAN’s new report identifies expanded adoption of practices like this as an underutilized pathway for meeting the state’s climate targets.
California has committed to reducing methane emissions from the dairy and livestock sector 40 percent below 2013 levels by 2030 under SB 1383 (Lara, 2016). An important strategy in meeting that target has been the Alternative Manure Management Program (AMMP), which invests in upgrades that move away from “wet” manure-handling and storage systems, where anaerobic decomposition of manure produces methane, to “dry” manure-handling and storage systems.
A new CalCAN report, titled Reassessing the Role of Alternative Manure Management in California’s Methane Reduction Strategy, revisits how these practices are represented in state modeling and explores their ongoing and potential contributions to the state’s methane reduction, water quality, and nature-based climate solutions goals.
AMMP’s methane reduction potential has been underestimated and is more cost-effective than recognized
In 2022, the California Air Resources Board (CARB) projected that alternative manure management practices would contribute a modest share of the additional methane reductions needed to meet the SB 1383 target. CARB’s projections were largely based on data available at the time from recent participation trends in AMMP.
The new CalCAN report models additional scenarios in which 50 to 75 percent of California’s lagoon-based dairy operations transition to alternative manure management practices. Under those scenarios, methane reductions could approach the additional 4.4 million metric tons of carbon dioxide equivalent (MMTCO2e) needed to close the projected gap under SB 1383. These scenarios illustrate what is possible with expanded funding and evolving policy and economic trends that are likely to increase demand beyond previously projected levels.
As part of annual reporting, CARB also evaluates and publishes the cost-effectiveness of California Climate Investments (CCI) programs, including AMMP. Current calculations assume a five-year project lifespan for AMMP-supported practices, while using a 10-year lifespan for the state’s other primary dairy and livestock methane program, the Dairy Digester Research and Development Program.
CalCAN’s report shows that recent evidence warrants revisiting AMMP’s projected lifespan assumptions. When adjusted to reflect longer project durations, AMMP ranks as the fourth most cost-effective CCI program out of 115 programs tracked by CARB.
Co-benefits of alternative manure management practices can play a vital role in meeting various state targets
By transitioning away from liquid manure storage systems, AMMP practices can reduce the volume of liquid effluent that must be stored and land-applied, which is especially relevant as the State Water Board considers new requirements for dairies on how they manage manure to prevent nitrogen from entering groundwater. Dry manure management and composting can shift nitrogen into more stable forms and reduce reliance on lagoon storage.
Composting also produces a stabilized product that is easier to transport. In regions with high livestock density, this can help move nitrogen from areas of surplus to areas of demand, such as nearby farms. California currently has an increasing demand for compost, in part driven by state investments in soil health incentives, suggesting potential alignment across state priorities.
The report recommends improved coordination between CARB, the California Department of Food and Agriculture (CDFA), and the State Water Board to better evaluate how methane mitigation strategies intersect with water quality and soil health goals.
Looking Ahead
California’s methane reduction goals remain ambitious. As CARB evaluates progress under SB 1383 and considers future pathways, updated analysis can help inform discussions about program design and funding allocation. CalCAN’s report provides additional context to support a more comprehensive evaluation of the contributions of alternative manure management practices. The report also offers policy recommendations for how state agencies can maximize AMMP’s benefits to meet climate and environmental goals.
