By Ian SimpsonWINDSOR, Va. (Reuters) - For years, Jimmy White woke up worrying about road-kill.An official with the Virginia highway system, White's responsibilities included ensuring that thousands of deer and other animals hit by cars were collected, a process that cost the state some $4.1 million per year.But roadside burial is increasingly not an option because of underground cables, pipes and other infrastructure near highways, while landfills charge fees and a decline in the U.S. rendering industry has removed another disposal outlet. Dragging the carcasses into nearby bushes or dropping them into pits can pollute groundwater, said Jean Bonhotal, director of the Waste Management Institute at New York's Cornell University.Today, White rests easier thanks to a new facility in the southeastern Virginia town of Windsor that takes some of the 10,000 to 15,000 animals, mostly whitetail deer, killed by cars each year, piles them under sawdust and turns the remains into landscaping material for roadsides."We're on the leading edge for this kind of composting," White, project manager for the Virginia Department of Transportation, said in an interview at the state's newest mass composting site, 45 miles (72 km) west of the tourist town of Virginia Beach.Standing amid the four concrete bins and piles of sawdust at a highway yard that will be the last stop for thousands of Virginia deer, White described the composting process as "really clean and pretty much a natural thing to do."Virginia, the No. 5 U.S. state for deer-vehicle collisions, is among the few states where composting is a new tool for highway officials faced with cleaning up after deer-vehicle collisions while also reducing the load on landfills.Particularly in the eastern United States, highway officials have faced a growing problem in managing road-kill in recent decades. Populations of whitetail deer have rebounded from a low of a few hundred thousand little more than a century ago to about 15 million today, according to the National Wildlife Federation figures.State Farm, the biggest U.S. auto insurer, says there were 1.2 million deer-related crashes in the 12 months ending in mid-2013, with the average property damage $3,414.COSTLY CARCASSESVirginia had been spending some $4.1 million a year to dispose of road-kill carcasses, with much of the cost going for landfill fees, according to the state Transportation Department.Its new $140,000 system began operating at the highway yard in southeastern Virginia at the start of December. The program was developed by North Carolina's Advanced Composting Technologies for farm carcasses and tailored for Virginia.The system calls for laying carcasses on a bed of sawdust inside a bin. Workers cover the deer with another layer of sawdust, and they generate heat as microbes break them down, sped by a forced-air system.Microbe-rich liquid is drained off and funneled into a tank, to be sprayed onto the pile twice weekly. That helps raise its internal temperature to more than 150 degrees Fahrenheit (66 Celsius).Within two months, nothing remains of the deer but some bones scattered in a rich brown compost, White said.WHIFF OF AMMONIAThe weeks of heat kill almost all the pathogens, or disease-causing agents. Even with about 120 deer rapidly decaying at the site, there was no odor beyond that of humus and a whiff of ammonia."Environmentally, it's the best way to dispose of the animals," said Cornell's Bonhotal.She said only a few states were composting road-kill, including New Jersey and New York along its state-run Thruway. Western states have avoided composting out of fear of spreading chronic wasting disease, the deer equivalent of mad cow disease and most commonly found in western mountains, Bonhotal said.A survey of 23 states by the American Association of State Highway and Traffic Officials found that four compost road-kill, though mostly in scattered sites. Composting is also encouraged by the U.S. Environmental Protection Agency.With composting, "a 1,200-pound (540-kg) cow will disappear in three months, except for bones," Bonhotal said.(Reporting by Ian Simpson; Editing by Scott Malone and Dan Grebler)Join the conversation about this story Click here to read full news..