13 November 2009

5 minute read

North America

"The FDA came out with a final rule that said rendering plants that accepted cattle over 30 months of age, which is any breeding animal, would have to have the sensitive tissue removed, which is basically the brain and the spinal cord," said Steve Higgins, researcher for the UK Department of Biosystems and Agricultural Engineering. "Basically it goes back to the issue of BSE (bovine spongiform encephalitis). They don't want to risk these constituents of BSE infecting the food stream." 

Mr Higgins emphasised that there currently are no cases of BSE in the United States and that the new rules will allow US beef to get back into markets that have been unavailable for some time.

The 30-month rule creates a lot of record keeping for rendering companies and many companies who were picking up carcases, no longer have a market for them, Mr Higgins said.

"So, rendering as a means of disposal, basically went out the window," he said. "Burial is an option, but it's very expensive. So we had to find an alternative and now we are demonstrating composting as a viable alternative. It's unbelievably cheap to do it."

Mr Higgins' method for composting dead farm animals safely breaks down the carcase while keeping pollutants out of the ground water. It's an odourless process that won't attract scavengers and also provides an end product that farmers could use as a soil amendment.

With approval of the Kentucky Office of the State Veterinarian, Mr Higgins set up a site at the Kentucky Agricultural Experiment Station in Woodford County to demonstrate two composting systems, bin and windrow.

"Windrow and bin composting are basically a ‘Composting for Dummies' technology," he said, drawing a parallel to the series of books with similar names. "It's hard to mess it up. Bin systems work really well for small animals such as hogs and chickens. When you get into large animals, more than 1,000 pounds, a windrow system works best because you've got more open area."

Presently, Kentucky requires an animal weighing more than 300 pounds be quartered before disposal. Mr Higgins says that can turn farmers away from practicing safe on-farm methods. For that reason, he demonstrates how to do whole carcases in an open-air facility that doesn't require a lot of capital to install.

The UK demonstration site uses a water quality best management practice of soil cement for its flooring. It's less expensive than concrete and just as impermeable.

Once the required impermeable flooring is installed, the rest of the process is easy and inexpensive, according to Mr Higgins. First he lays two feet of wood mulch or some type of carbon source on the base of the bin or windrow. Wood chips are readily available from storm-damaged trees on the property. He can also get them inexpensively or even free from county mulch programs or tree services. The entire carcase is rested on top of that mulch bed and covered with more wood mulch - at least 3 or 4 feet for a very large animal.

"That angle of repose will give you about two feet minimum on the sides covering up the carcase. Nothing is to be exposed.. Completely cover the animal," Mr Higgins said.

This method prevents odours from escaping the pile, so scavengers aren't attracted to the hidden remains.

The pile will quickly heat up to about 160 degrees Fahrenheit, and in five to six weeks, nothing but a few bones will remain.

"You're actually using beneficial bacteria that are ubiquitous," Mr Higgins explained. "They're everywhere. They're on the animal and in its gut. What you get is a sudden surge in the population of these microbes, and they basically feed off that carcase, breaking it down into its bare essentials."

The resulting compost can be spread on fields or used to compost future downed stock, which is the method Mr Higgins prefers. Each succeeding use of the material results in faster composting because the base is already inoculated with a healthy population of beneficial microbes.

Some farmers might have concerns that composting an animal that died of an illness will inoculate their farm with that disease. Mr Higgins said that won't happen.

"Any disease-causing pathogens are destroyed by beneficial bacteria and by the heat that's generated in the composting process," he said. "It's controlled, it's managed, and it takes care of a lot of nuisance and water quality concerns," Mr Higgins said.

UK is working with the Kentucky Division of Conservation and the Kentucky State Veterinarian's Office to develop standards for the composting method. Mr Higgins' method could lessen farmers' headaches when facing another task - creating their agricultural water quality plan.

"When farmers are developing their Ag. Water Quality Plans, one of the things that they have to deal with is dead animal disposal," said Amanda Gumbert, water quality liaison with the UK Cooperative Extension Service.

Ms Gumbert is working with Steve Higgins, Kentucky's Agriculture Water Quality Authority, and the Division of Conservation to help develop the language for a new practice standard, including clear information about composting as an option for disposing of carcasses.

"In the (current) state statute, composting is an option for disposal, but there have been permitting issues before," she said. "The language is somewhat confusing as to what is legal and what is not. What we're trying to do is get people away from throwing dead animals into sinkholes or dragging them out to the "back forty and leaving them where they could create other problems."

The state's practice standards are designed to prevent contamination of groundwater sources. Ms Gumbert explained that leachate from a carcase left in a sinkhole would go right into the groundwater, and then, potentially contaminate water that is pumped from wells, comes out of springs or gets into the public water supply.

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