By Dr. Michael Payne, UC Davis, School of Vet. Medicine & Director | Originally Published in CDQAP’s Quality Assurance Update, October 2025
Before producers can begin composting carcasses, BMPs have to be developed & approved.
Although the practice is permitted in many other states, since 2003 California has remained unique in explicitly banning the composting of mammalian tissue. That changed on October 11, when Governor Newsom signed Assembly Bill 411 into law.
As might be expected, there has been a flood of inquiries from producers asking what this means for them. While the regulatory timeline to implementation is still fluid, a CDFA memo and industry presentations have provided some insight.
Under what situations will I be able to compost dairy carcasses? CDFA foresees three situations in which dairy producers might compost mortalities. 1) Federal disease response using USDA guidelines, such as those for Foot and Mouth Disease 2) State declared emergency such as rendering disruption 3) Routine mortality disposal under AB 411.
Can I start composting mortalities now under AB 411? No. The bill also requires that CDFA lead an interagency process to develop Best Management Practices (BMPs) for on-farm livestock composting. Composting of livestock carcasses is not permitted until BMPs are finalized and adopted by CDFA’s Secretary of Agriculture.
When will those AB 411 BMPs be developed? Once AB 411 takes effect on January 1, 2026, CDFA will begin working to develop the required BMPs. Ensuring that CDFA’s BMPs align with other agencies’ existing laws and regulations could require many months.
Who will be involved with the BMP development? Relevant “Sister Agencies” to CDFA include CalRecycle, the California Department of Public Health and various regional water boards and local enforcement agencies. The process will likely include guidance from composting researchers as well as input from industry.
What sort of things would those BMPs include? BMPs for carcass composting typically include: mitigating storm-water runoff into surface waters, minimizing leaching to groundwater, monitoring for flies, odors and wildlife scavengers and ensuring adequate time and temperature compost heating. Compliance with state and local regulations will also be required.
In addition, all compositing materials must come from the agricultural site composting and cured compost can only be applied to land owned or leased by the owner of the livestock carcasses.
What should I do while I’m waiting for the BMPs to be finalized? For now, nothing has changed with your mortality management. For instance, attempting to cancel a rendering contract is problematic because your water board will still be requiring documentation that carcass management is consistent with the current Dairy General Order.
Once the BMPs are developed, how will I learn to apply them? CDQAP and the California Dairy Research Foundation are working closely with all the dairy trade organizations. This collaboration will provide up-to-the-minute information on the implementation of AB 411. We will develop new resources for producers implementing carcass composting on their farm.
Is it possible to compost livestock carcasses sustainably? Yes. Research currently being conducted by CDQAP and the California Dairy Research Foundation indicate that:
- Properly constructed compost piles reach USDA time & temperature requirements for animal pathogens.
- Properly constructed compost piles have little or no impact on groundwater contamination risk.
- Heavy metal content of finished compost is far less then state and federal safe levels.
- Pathogen levels are far lower then than state limits for finished commercial compost.
- There is no difference in air emissions between carcass composting and manure composting.
If you have additional questions please contact Dr. Michael Payne at mpayne@ucdavis.edu.
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