- Economic impact of methane emissions reductions varies by herd size and manure management practices employed.
- Methane emissions from California dairy manure management are declining with adoption of alternative manure management practices and installation of dairy digester projects with biogas capture and use.
- Continued funding of the Alternative Manure Management Program helps dairy producers regardless of herd size to participate in and contribute to manure methane emissions reductions.
To provide an economic evaluation of strategies for methane emission reduction effectiveness and appropriateness in small and large California dairies.
Background, Findings, and Outcomes:
California lawmakers have set a target for reduction of greenhouse gases. Senate Bill 1383 (SB 1383) specifically requires that by 2030 methane emissions from dairy and livestock manure must be 40% lower than 2013 levels. Understanding the environmental and economic impacts of implementing methane emission reduction strategies for farms of all sizes is necessary to support the wise investment of time, management, and capital resources, and is paramount to achieving the reduction goal.
Researchers from the University of California, Davis, evaluated the economic impact of two baseline manure collection practices—flush system and scrape system—against five alternative practices: compost bedded pack barn, solid separation (with both open solar drying and composting), scrape conversion, and lagoon digesters.
The analysis showed that the economic impact of methane emissions reductions varied by herd size and manure management practices employed. Adoption of any of the alternative practices could reduce manure methane emissions per cow but come at a higher cost to the farm compared with their baseline practice. At any given herd size, freestall dairies were assumed to collect 2.4 times more manure and have greater emissions when compared with non-freestall dairies. This means freestall dairies have a greater chance to reduce emissions. For example, adopting a digester reduced methane emissions by almost 83% on freestall dairies and by almost 58% for non-freestall dairies.
Using these same simulations, the researchers project that while the aggregate number of cows remains unchanged into the future, the number of cows in the smaller herd size categories will decline rapidly. This means fewer dairies in the smaller herd size categories and more cows per herd in larger herd size categories. In addition, with the adoption of digesters by a high share of dairies in the larger herd size categories, their methane emissions per cow decline and are well below those of the smaller herds.
Investment of public and private funds is necessary to reduce manure methane emissions. Continued funding of the Alternative Manure Management Program helps dairy producers regardless of herd size to participate in and contribute to manure methane emissions reductions. Without public funds, smaller dairies likely will be disproportionately impacted by higher fixed costs per cow associated with these reductions.