May 27, 2009 | General

Composting Road-Killed Deer

BioCycle May 2009, Vol. 50, No. 5, p. 31
Ohio Department of Transportation standardizes mortality composting as part of operations, finding the process to be a quicker, more sanitary and less expensive method of disposal.
Angel Arroyo-Rodriguez

THE collection and disposal of road-killed animals presents a significant problem to state and county agencies and local governments in charge of maintaining roadways. In Ohio, road-killed deer are of high concern, as their size can make collection more strenuous and disposal more expensive. Just for the year 2007, the Ohio Department of Transportation (ODOT) reported handling 18,714 road-killed deer statewide. Increased concern with potential detection of chronic wasting disease reduced the willingness of the few remaining rendering plants to accept deer carcasses, leaving landfills as the only option for disposal.
Composting of livestock mortalities on farms has been a common practice in Ohio and throughout the world. In 2000, ODOT became interested in utilizing composting as a quicker, more sanitary and less expensive way to dispose of road-killed deer. The first facility was established in October 2000 in Wayne County; currently, there are facilities at Ashland, Clark, Medina and Richland county garages.
The success of these facilities is in large part due to adapting the composting process into the regular operations of the organization. ODOT county garages had available space, access to construction materials and bulking materials (e.g. wood chips). Composting operations are conducted in three-sided bins with no roof or covering. The bins were assembled from discarded highway concrete dividers placed on a compacted pad of recycled asphalt shavings. Each road crew brings collected carcasses to the facility throughout the day and places them in a designated receiving area or in front of the bin being currently filled. At the end of the day an employee loads carcasses into the bin. The pile assembly method and composting process were standardized in the following manner.

Each bin is loaded by placing carcasses starting in the back. They are stacked vertically until the maximum height is reached, and then the stack is continued forward until the front end of the bin is reached. A maximum of three layers of deer carcasses is placed in each bin. The first layer of carcasses is placed on top of a minimum of 12 inches of bulking material. A minimum of 12 inches of bulking material separates each layer of carcasses. The third and last layer is covered with a minimum of 24 inches of bulking material. No intentional cutting or slicing of the animals is required.
Composting consists of a two-stage static pile process, with turning between stages, followed by a curing period. Once a bin is full, it remains undisturbed for 90 days, after which the contents are turned, mixed and covered again with 24 inches of bulking material. The composting mixture then remains undisturbed for another 90 days. Afterwards, the compost can be further cured if needed, reused in the composting process or tested for distribution. Only cured compost that will be used outside the facility boundaries is required to be tested. Testing requirements include heavy metals, pathogens, foreign matter and parameters of agronomical interest. The time frame for each stage might be longer than necessary, but it makes it easier for employees to maintain a schedule and monitor the facility.
Throughout the years the standard process has been refined based on experience at the facilities. Initially, 100 percent sawdust was used as bulking material at the Wayne County facility. When wet, sawdust forms a crust-like layer on top of the pile, which would prevent excessive rainwater from entering the piles. At the time, this was considered important, as the piles were to be outdoors without a roof. However, the sawdust performed too well and the piles became overly dry, thus slowing down the composting process. Wood chips averaging two inches in size were mixed with the sawdust and moisture improved; however, after each 90-day stage, it was noticed that the process was not as complete as it should have been and temperatures were remaining below 120°F. Suspecting that a suboptimum carbon to nitrogen ratio was the cause, piles were broken apart and thoroughly mixed with fresh bulking materials (a mix of wood chips and green materials derived from shredded tree trimmings). In a couple of days, temperatures above 130°F were recorded and maintained for several weeks.
Similarly, the Ashland County facility experienced a slowdown in the process. Typically only the larger bones, such as jaw and skull, should be observed after the first stage and they should be brittle. However, after the completion of the first stage more bones remained and were still soft. Upon evaluation of its operational process, it was noted that composted material had been reused too many times, with piles basically assembled out of mature compost. Fresh wood chips were mixed into the piles at a minimum 1:1 ratio and the process improved.

The composting methodology was derived from the Ohio Livestock and Poultry Mortality Composting Manual, published by The Ohio State University (OSU) Extension (2000). This manual helps determine the bulking material volumes needed and the time frame of each composting stage based on formulas that factor the size and weight of the carcasses and the type of bulking material to be used (e.g. sawdust, wood chips). In addition, OSU Extension offers a trainer and an operator certification for on-farm composting of livestock and poultry. Certified trainers at Ohio Environmental Protection Agency (Ohio EPA) prepared a similar operator training for ODOT staff. The training introduces staff to the basic science of composting, preparing an optimum bulking material mix and the reasoning behind it, how to assemble and monitor the piles, troubleshooting and record keeping. When possible, the training includes a field demonstration.
ODOT composting facilities are regulated by the Ohio EPA and require a registration, operating license and financial assurance fund. There is no cost for the registration. The license requires an annual fee of $300. The financial assurance fund for these five facilities ranges from $2,000 to $6,000.
Table 1 provides cost data for the deer composting installation at ODOT’s Ashland garage, which has six composting bins. The cost/deer is estimated using a minimum of 250 deer for 2006 and 2007. The actual number composted was slightly higher. In addition, the cost of bulking agent was due to an initial Ohio EPA requirement to use sawdust, which had to be purchased. Sawdust is no longer required, and garages are using wood chips generated by road crews, which are available at no cost. Other costs not reflected in Table 1 are $300/year for the annual license, and the financial assurance fund contribution ($2,300 for the Ashland garage).
In addition to ODOT, the Montgomery County Engineer’s office and the City of Springfield established composting facilities modeled after the ODOT sites to compost deer and other road kill. Similarly, the Seneca County Dog Warden replaced its incinerator with a composting facility and accepts euthanized pets from veterinarians, as well as road kill.
Composting has been a viable solution for the disposal of deer carcasses and other road kill in Ohio. Standardization of the process has allowed several entities to incorporate this practice into regular operations, take advantage of available materials and reduce transportation and disposal costs.
Angel Arroyo-Rodriguez, AICP, RS, is an Environmental Specialist for Ohio EPA’s Composting & Infectious Waste Programs, Division of Solid & Infectious Waste Management.

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