But rendering plants have fallen on hard times of late. Mad cow disease, which was first identified in the U.K. in 1986, has led to costly regulations that rendering plants have passed on to their customers. In 1997, it became illegal in the United States to feed the remains of a dead ruminant to a live ruminant, thus eliminating one of the industry's largest markets: cattle feed. In 2009, the FDA made matters worse for renderers by requiring them to remove the brain and spinal cord from cows older than 30 months (thus making it especially expensive for dairies, whose cows live longer, to render deadstock). The intention behind this provision was certainly sensible—it keeps prions, the bits of the nervous system that contain mad cow disease, out of feed destined for non-ruminant animals—but its economic impact has been considerable. Costs have gone up as much as fivefold, and the industry has consolidated into fewer operations.
How this problem will be solved remains anyone's guess. Early responses, however, haven't been encouraging. On-site burial of animals has always been popular, but it's becoming increasingly commonplace with the decline of rendering plants. This legal option is certainly an improvement upon illegal off-site dumping (which anecdotal evidence also suggests is rising), but it's still a case of sweeping waste under the rug. Feedlots and ranchers basically dig their own bins and windrows and bulldoze waste into a mass grave. Burial pits are capable of holding tens of thousands of pounds of carcasses. Some states require permits to dig them, others don't. Negative impacts on water quality have been well documented both on site and downstream from burial grounds. Groundwater contamination is routine. The leaching of chloride, ammonium, nitrate, coliforms, and E. coli intensifies with rainfall and oozes for decades after burial (it can take 25 years for carcasses to decompose).
Outdoor incineration has also become more popular with the gradual decline of rendering. But incineration comes with its own rap sheet of environmental and health-related pitfalls. It reliably releases heavy metals into the atmosphere. Pyres emit pollutants including sulfur dioxide, carbon monoxide, and nitrogen oxides. Incineration is almost always used for culled animals—beasts that have been condemned to death after a disease outbreak (burying them works poorly because they can literally explode as a result of methane build up—a conditioned known as "cattle bloat"). When infected animals are burned, a host of new poisons go airborne. Without the most rigorous monitoring, these toxins easily reach the human food and water supply. All in all, incineration is a mess.
Another alternative to rendering animal carcasses is composting. This option is relatively new, with many states making it legal to compost dead farm animals in the past ten years. On paper the procedure has its merits. Animals are aerated in a giant compost bin, where they decompose to produce humus that is rich in nitrogen, potassium, and phosphorus—all of which potentially make it an excellent fertilizer. Many agriculture experts are optimistic about animal composting [pdf].
But (there's always a "but" when it comes to animal agriculture) there are problems—some minor, others quite serious. Minor ones include the fact that bones do not compost easily or quickly. More serious problems center on the fact that what's being composted is more than animal flesh and bones. The antibiotics, growth promoters, vaccines, and array of agricultural chemicals routinely used in animal agriculture are also composted. Composting, moreover, can also concentrate naturally occurring heavy metals. Currently, states that allow the use of composted animals limit its application to relatively innocuous tasks such as growing highway wildflowers.