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Federal Highway Administration > Publications > Public Roads > Vol. 70 · No. 1 > Composting Roadkilled Deer

Jul/Aug 2006
Vol. 70 · No. 1

Publication Number: FHWA-HRT-2006-005

Composting Roadkilled Deer

by Elisabeth Kolb

Researchers in New York State are studying an alternative method for disposing of animals killed in roadway collisions.

This mule deer was struck by a motor vehicle while attempting to cross Yellow Head Highway 16 just west of Prince George, British Columbia, Canada. Determining what to do with roadkilled deer carcasses is the topic of ongoing research sponsored by NYSDOT.
This mule deer was struck by a motor vehicle while attempting to cross Yellow Head Highway 16 just west of Prince George, British Columbia, Canada. Determining what to do with roadkilled deer carcasses is the topic of ongoing research sponsored by NYSDOT. Photo: Roy V. Rea, University of Northern British Columbia.

As State departments of transportation (DOTs) work to improve traffic flow and mobility, the Nation's roadways are moving a growing volume of people and goods at greater speeds and at all hours of the day. One consequence of this seemingly endless flow of cars and trucks is that an estimated 1.5 million deer-vehicle crashes occur each year nationwide.

Indeed, collisions between deer and vehicles result in thousands of human injuries and millions of dollars in property damage, as well as countless animal deaths. Many factors contribute to the problem, including habitat fragmentation, increasing deer populations, the growing number of vehicle miles traveled, and increased vehicle speeds.

While researchers continue to study and implement solutions such as wildlife crossing structures to help minimize crashes, transportation and environmental experts at the New York State Department of Transportation (NYSDOT) are looking at an alternative method for disposing of the animals' carcasses. Traditional methods including "natural" disposal by offroad decomposition, pit burial, rendering into feed for domestic animals, and landfill disposal may be slowly being replaced by an environmentally and aesthetically preferable approach that entails composting the deer carcasses with wood chips.

NYSDOT researchers have found that deer composting provides a financial benefit and an opportunity to recycle materials such as asphalt millings, wood chips, and roadkill, which are readily available within the realm of highway work. "Deer composting can be conducted in a safe and worker-friendly environment," says Peter Teliska, regional transportation systems engineer with NYSDOT Region 8. "It also requires ingenuity and a willingness to try something new, traits that are easily found in transportation operations."

Traditional Disposal Methods

One traditional practice for disposing of roadkill entails simply dragging the carcasses off the road and into wooded areas to allow for natural decomposition. This practice, however, has a few downsides. For instance, it can attract scavenger animals such as coyotes and turkey vultures, which can become a nuisance in areas with a high concentration of deer-vehicle crashes.

Further, with the exponential growth of residential development along State highways, neighborhood residents are understandably opposed to depositing rotting deer carcasses in the nearby woods, citing odors, aesthetic and health concerns, and potential safety problems from the increasing presence of scavengers.

Other traditional disposal methods, such as hauling to transfer stations, pit burial in the highway right-of-way, or rendering by private contractors, have become impractical as well. Many solid waste disposal facilities do not want carcasses, and depending on the region, the tipping cost at transfer facilities can be as high as $15 per deer. Municipal solid waste incinerators are not designed to destroy large animal carcasses, which tend to come out charred but intact at the end of the process and still require disposal.

A worker is using an earth-moving tractor to prepare a compost bed. The first step is to apply a 0.6-meter (2-foot) layer of wood chips atop a ground layer of millings.
A worker is using an earth-moving tractor to prepare a compost bed. The first step is to apply a 0.6-meter (2-foot) layer of wood chips atop a ground layer of millings.

In some areas, the sheer volume of deer carcasses makes pit burial in the highway right-of-way prohibitive. A highway agency attempting to dispose of 1,000 deer carcasses by burial would have to dig 100 pits for the permitted 10-deer maximum per pit. This approach can pose a challenge considering right-of-way restraints, access issues, safety, time, and equipment. Logistics not withstanding, deer burial causes environmental concerns because of the potential addition of nitrates and pathogens to groundwater.

Finally, fees charged by private contractors have increased to as much as $80 per deer, attributed in part to increased tipping fees charged by landfills and restrictions placed on animal-derived protein products fed to livestock due to concerns about mad cow disease.

Deer pits like the one shown here are slowly becoming obsolete, reflecting concerns about odors, scavenging by other animals, and disease transmission. Deer were dumped in this pit for later burial beneath lime and dirt. Photo: Jim Benson, New York City Department of Environmental Protection.
Deer pits like the one shown here are slowly becoming obsolete, reflecting concerns about odors, scavenging by other animals, and disease transmission. Deer were dumped in this pit for later burial beneath lime and dirt. Photo: Jim Benson, New York City Department of Environmental Protection.

The Science of Composting

Some might ask: What makes composting a feasible alternative? What happens during the composting process? Composting is the controlled, aerobic, biological decomposition of organic matter into a stable product that can be used as a soil amendment. One advantage of composting is that it allows natural decomposition to occur at a faster rate.

Farmers have composted dead livestock with wood chips or sawdust since the 1980s. Hunting clubs and some public entities have composted dead game animals as well. One of the reasons composting is attractive is that no special certifications or permits are needed. NYSDOT workers, however, must follow the instructions laid out in the agency's (soon-to-be-published) guidance manual.

Shown here is a completed compost windrow containing roadkilled deer. Because wood chips allow air passage into the pile, turning over the material is not necessary during most of the composting  stages.
Shown here is a completed compost windrow containing roadkilled deer. Because wood chips allow air passage into the pile, turning over the material is not necessary during most of the composting stages.

Composting can begin in the cold of winter because natural processes release enough energy to heat the pile of organic matter and keep the biochemical reactions going. "With October through December being the peak months for deer-vehicle crashes, winter composting, therefore, represents a seasonably appropriate strategy for disposing of animal carcasses," says Kyle Williams, head of the operations section of the Environmental Analysis Bureau, NYSDOT. "It seems logical that NYSDOT would incorporate some composting practices into its activities to reduce disposal costs and handling of decomposing animals."

A compost pile should be sited on an impermeable surface, but a compacted layer of asphalt millings is acceptable. Composting can take place in windrows (rows of piled-up material) or bins. To start a pile, workers should place a 0.6-meter (2-foot)-high layer of wood chips. To this bedding layer, add alternate layers of wood chips and deer carcasses until the pile has reached a height of 1.5 meters (5 feet). Then the pile should be capped with 0.6 meter (2 feet) of wood chips to provide an insulating layer.

The workers need to monitor and record the temperature of the pile to ensure that it heats up, indicating that the compost process has activated. Temperatures above 71 degrees Celsius (160 degrees Fahrenheit) are common for a few days immediately following activation. The high compost temperatures kill many common pathogens such as salmonella and fecal coliform, including E coli.

NYSDOT Highway Maintenance Supervisor Mike Augustine and Assistant Resident Engineer Tom Story monitor the temperature of a compost pile in Highland, NY. The pile contains 700 deer  carcasses.
NYSDOT Highway Maintenance Supervisor Mike Augustine and Assistant Resident Engineer Tom Story monitor the temperature of a compost pile in Highland, NY. The pile contains 700 deer carcasses.

The final layer of wood chips keeps odors and scavengers at bay. In Highland, in Ulster County, NY, a pile with 700 carcasses is virtually odor free, according to local NYSDOT workers. Once the temperature of the compost drops below 38 degrees Celsius (100 degrees Fahrenheit), much of the composting process will have concluded. (Ongoing research will provide a more thorough understanding of completion indicators.)

A New Approach

In the summer of 2001, the Hudson Valley Regional Council's Solid Waste Committee acknowledged the growing disposal dilemma facing local and State transportation agencies and proposed a demonstration project for composting roadkilled deer in the lower Hudson Valley. Solid waste officials from the New York State Department of Environmental Conservation's (DEC) Region 3 took the lead in the project and selected an area north of New York City where dense commuter traffic and high deer populations result in deer-vehicle collisions more frequently than in other parts of the State. The pilot project took place at a facility operated by the New York State Department of Correctional Services.

DEC deemed the project successful based on observations of the reduced volume of the waste and elimination of many of the problems in handling carcasses. Also, early test results revealed a reduction in pathogens during composting; however, more research is necessary to substantiate those initial results. "The possibility that the compost end product could be reused in the composting process or other highway purposes looked promising," says Terry Laibach, solid waste environmental program specialist with DEC Region 3, "which absolutely puts this process in line with New York State's solid waste management hierarchy of 'Reduce, Reuse, Recycle.'"

The thermometer poking out from the compost pile reads about 74 degrees Celsius (165 degrees Fahrenheit). Photo credit: Elisabeth Kolb, NYSDOT
Proper composting requires sustained elevated temperatures. High temperatures help kill pathogens in the pile.

The success of the pilot project demonstrated that deer composting could be a viable option for regional environmental regulatory agencies. Other State agencies and academic institutions took notice, including NYSDOT, DEC's Division of Solid and Hazardous Materials and Wildlife Pathology Unit, the New York State Department of Health, and the Cornell Waste Management Institute (CWMI). An immediate concern was the potential environmental and health issues that could stem from composting.

Many of these issues are critical in animal disposal no matter which method is used. For example, workers may be exposed to an animal's body fluids during pickup, delivery, or dropoff. In fact, it is common practice to wear protective gloves, face masks, and protective eyeglasses. When composting deer at a facility, many, and in some cases hundreds, of carcasses are concentrated into one area, and a thorough analysis of the potential risk is necessary.

In 2002, Ward Stone, a wildlife pathologist with DEC's Wildlife Pathology Unit, started testing thousands of deer carcasses for the presence of chronic wasting disease (CWD), similar to mad cow disease but affecting deer and elk. By April 2005, Stone and his laboratory team had discovered isolated cases of CWD in upstate New York. These areas were quarantined, and composting was excluded there as a form of disposal.

Deer remains in a compost pile are reduced to a thin gray material after 4 months. A few bones are the only recognizable parts left of this deer.
Deer remains in a compost pile are reduced to a thin gray material after 4 months. A few bones are the only recognizable parts left of this deer.

"There are some indications that microbes active in the composting process may break down the prion [a protein particle believed to cause infectious diseases of the nervous system] structure, the protein attributed to CWD," according to Stone. He advocates research into CWD that is introduced into compost under controlled conditions. "One day, with properly sited and controlled composting, [deer composting] might become part of the process of inexpensively destroying prions and helping control CWD," he says. In the meantime, "as long as CWD occurs in just isolated areas, composting should be explored further for areas that do not have CWD."

Ongoing Research

By 2003, NYSDOT had established deer composting piles across the State. Although NYSDOT published a manual for facilities wishing to start their own composting piles, agency officials recognize the need to prove that the process is safe for workers and that the final compost product can be used in the highway environment. DEC Region 3 officials determined that deer composting could continue as long as workers follow the NYSDOT manual and no end products are used in the highway right-of-way until DEC grants approval.

In 2005, NYSDOT funded a research project to study the breakdown of pathogens in deer composting piles to ensure environmental and worker safety. CWMI is now conducting the research on behalf of NYSDOT. Scientists from various specialties identified the following indicator pathogens for study: salmonella, fecal coliform including E coli, fecal streptococci, enterococci, and mycobacterium avium paratuberculosis. These particular organisms were chosen by virtue of relative hardiness and whether they behave like other related pathogens that would be found in wild deer. Laboratory and sampling logistics also had to be taken into consideration. Due to the high cost involved in researching the breakdown of prions during composting, that study had to be excluded from the current research agenda. However, a literature search will be conducted on the prevalence of pathogens in New York State's wildlife population and conditions associated with their inactivation. An executive summary will be published.

The CWMI team set up research piles at the Ithaca campus of Cornell and at assorted NYSDOT facilities across the State. Team members Ellen Harrison, Jean Bonhotal, and Mary Schwarz bring years of experience from composting on farms. Their research will look at how pathogens break down and will identify indicators that the compost cycle is complete. At that point, NYSDOT may have more options for using the end product, such as to stabilize eroding roadsides or to amend poor-quality soils within the highway environment. For now, the material is used only for composting purposes, such as starting a new pile. The team's findings will be released in 2007, along with new guidance and training materials.

Harrison is confident about the future of composting. "There is a lot of roadkill that needs to be managed in an economical and environmentally sound way," she says. "Our research will help determine the role composting can play in meeting this challenge."


Elisabeth Kolb is an environmental coordinator for NYSDOT Region 8. Her work encompasses the wide range of environmental issues related to transportation facilities and maintenance. One of her responsibilities is serving as project manager for the research effort focusing on analyzing pathogens in roadkilled deer compost. She may be contacted at 845-575-6158 or ekolb@dot.state.ny.us.

For copies of NYSDOT's manual, Road-Kill Deer Carcass Composting: Operation and Maintenance Manual, please contact the author or visit https://www.nysdot.gov/portal/page/portal/divisions/engineering/environmental-analysis/repository/deer_c_manual.pdf. To learn more about a project sponsored by the Transportation Pooled Fund Program to develop a Deer-Vehicle Crash Information and Research Center, visit www.pooledfund.org/documents/solicitations/906.pdf.

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