Wednesday, 11 May 2011

Roadkill compost

I found out today that the state of Virginia is considering getting rid of roadkill by composting it.  The state’s Department of Transportation is considering it as an alternative to sending carcases to landfill – 77% currently end up there and transporting them to such sites costs $4.4 million annually.

I didn’t stumble across this fact by chance.  I Googled ‘roadkill compost’ having heard several years ago about how roadkill was used to make compost in Australia, and wondered what the compost was like and what the opportunities would be for this kind of treatment of British roadkill.  With the increasing deer numbers we’ve seen in recent years and correspondingly higher numbers of dead deer on our roads, ought we to think about this?

According to the Cornell University Chronicle, using a simple composting technique, the Cornell Waste Management Institute (CWMI) discovered it takes about a year to turn deer carcasses into compost that can be used for landscaping purposes along the very roadsides that were the animals' death sites.  The cost of composting a deer is less than $25 a carcass.

As in the UK, deer/car collisions are an increasing problem, especially in rural areas.  Collection followed by landfill or cremation, or roadside burial apparently all have public or environmental health impacts.  But composting, in passively aerated woodchip windrows in which the carcases are buried side by side, is inexpensive, avoids human health problems and provides environmental benefits.

Microbial action in the pile causes it to heat to 110 degrees Fahrenheit (43oC) and decomposition takes around six months.  The high temperatures and microbial processes during composting greatly reduce or kill most pathogens, minimizing the chance of spreading disease and usable compost is available after one year.

Public Works magazine reports that motorists in Maryland kill around 1,500 a year and that the state is turning them into nutrient-rich soil conditioner that combats erosion and sucks up contaminants before they reach storm sewers.

The reports states that unlike vegetative matter, composting deer doesn't require windrow turning.  Because coarse wood chips are used in the process, air flows through the pile naturally. The pile quickly reaches temperatures necessary to break down muscle tissue and cartilage and kill faecal coliform bacteria and Salmonella but that skulls and other large bones, which don't completely decompose, are composted again or disposed of separately.

Unfortunately, I could find nothing about the composition or quality of the compost but Cornell has produced a useful factsheet available here.