When a large animal dies on your farm or ranch, what are your options for disposal? There are limited legal options in California, especially as rendering facilities have closed, regulatory burden has increased, and predators have grown in numbers. Livestock mortality composting could be a viable solution.
Composting of mammalian tissue is legal in most states and recommended for on-farm disposal of livestock mortalities. California has allowed composting to occur on farms only during emergencies such as high heat events, natural disasters, and disease outbreaks. This research aims to make composting a legal disposal option for livestock mortalities and to provide input to streamline the regulatory agency process.
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California has one of the strictest composting requirements in the country—requiring yard waste, food scraps, and more to be sent to composting facilities, so why are we so behind on livestock mortality composting? With livestock and dairy production contributing $11.7 billion in 2018 to the state economy, change is needed to support these industries. There are currently three rendering facilities statewide located in central California between Sacramento and Fresno. In many cases, these facilities are too far from livestock operations to take mortalities and the cost to transport and process carcasses is prohibitive to operations.
Rendering provides a beneficial use to the carcass like composting and unlike other disposal options. Landfills can get permitted to accept livestock mortalities, but there is no beneficial use to the carcass, and not many landfills are adequately suited.
Many livestock operations have a “bone pile” where they place livestock mortalities. This option can attract large predators such as wolves, mountain lions, bears, and others, making livestock operations a hazard with decreased predator control options. It also increases the time needed for the mortality to decompose with bones existing for years. Part of this study was to monitor predator and scavenger visits to current livestock mortality disposal sites in Modoc and Siskiyou counties. Trail cameras have been located on current disposal sites for a little over a year.
The pie chart shows the percentages for several different predator and scavenger species visits. The most common predators are bears, coyotes, and birds of prey, including golden eagles, bald eagles, hawks, turkey vultures and crows. Other species include skunk, bobcat, mountain lion, and raccoon. One surprising finding during this component of the study was the frequency of domestic dogs visiting the disposal sites. Some of the dogs at the sites included livestock guard dogs, while others seemed to be neighboring pets.
In 2019, a team of University of California Cooperative Extension (UCCE) and California State University (CSU) Chico researchers began a study looking at how livestock mortality composting would work in California. What are the current regulations preventing composting? Have studies taken place in the past? What would a composting site look like that follows current state regulations? Are all these regulations needed? These questions led to a composting site being established at the Intermountain Research and Extension Center in Tulelake, CA. Letters and permits were submitted to agency staff from the county environmental health department, CalRecycle, California Department of Food and Agriculture, California State Veterinarian, and the regional and state water board.
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An existing three-sided structure with cement at the base was retrofitted to accommodate the composting pile’s permitting regulations. A metal-roofed carport structure was installed within the structure as a roof, required by the regional water quality board. Base rock material was placed on the floor, and a pond liner was put on top of the rock to act as an impermeable layer. Then tube sand was used to secure the pond liner and created a basin to deter any runoff from the site.
Livestock mortalities that have died only of natural causes are allowed to be composted. On Aug. 10, UCCE received a call that a cow was available for the local producer project. It is required to have a certified dead animal hauler move the animal. Once at the composting site, a layered base of fine and coarse wood chips and straw was laid out as an absorbent layer on top of the base rock. Materials were byproducts from the Alturas Mill. The carcass was placed in the center of the structure and the carbon materials were layered on top. A sprinkler is available to add moisture as needed during the study.
Temperature readings are taken at 18- and 36-inch depth, and moisture and pH are also taken. A temperature of 131 F for 72 hours is required to kill potential pathogens in the compost pile. On Day 3, the pile achieved the target temperature and continued through Day 8. Water is applied as needed, and extra wood chips and straw are available as the pile shifts and needs additional material.
There is a good amount of research and educational material about livestock mortality composting from several university cooperative extension programs across the country. Navigating the regulatory process and coordinating with eight to 10 government agencies with competing regulations make this process currently unfeasible in California. By the end of this study, the objective will be to suggest best management practices from the research and other available science to create a streamlined approach to livestock mortality composting in California. — Laura K. Snell, UCCE livestock and natural resources advisor; and Nicole Stevens, lab assistant
