Mortalities are a reality on any hog farm. There are many options for carcass disposal, but some raise environmental concerns.
Rendering is still the most common means of animal carcass disposal, says Bill Crawford, environmental manager for Preferred Capital Management of Fairmont, MN.
As the cost of rendering rises, producers look to other means of carcass disposal. Incineration is often still legal, but producers need to check with county regulators; cost can be an issue as well. Burial can be an option but also creates logistical problems as operations grow larger.
“Sow mortality is a big issue, and obviously the bigger units get, the more numbers (of deads) you are talking about,” says Crawford.
For Crawford, when feasible, the best method of carcass disposal is composting. “You take a problem and turn it into fertilizer,” he says.
If a composting facility is set up and operated correctly, it will function year 'round, even with moisture and temperature extremes.
“With a sow farm, you've always got preweaning mortalities and placental material, and that stuff can all be composted and gone in a week. Obviously for a mature sow, it is going to take longer with simply more tissue to be consumed in the process. But if you have composted them correctly, they are pretty well cooked in 90 days and even the bones bust up quite easily,” says Crawford.
Keys to Composting
First, locate the compost site near where the majority of the mortalities occur, and typically not in view of the general public, he says.
Load the compost pile correctly by layering the mortalities as a single layer, not simply as a pile of carcasses under a layer of carbon material. As more deads need to be added, simply continue to layer the pile, ensuring a minimum of 8-10 in. of carbon material covering the deads.
“Start with a layer of carbon material, maybe a foot deep, then place today's mortalities as the next layer, then cover them with 8-10 in. more of carbon,” suggests Crawford.
“There is not a lot of rocket science here,” he continues. “It's just the natural microbial breakdown of the carcass.” The University of Minnesota has found a 90-day system works quite well. When filling a compost bin, do a 30-day fill of carcasses, then start building a new pile. Build the second pile for 30 days while the first bin is cooking/decomposing for those 30 days.
On day 60, completely turn or re-mix the first pile using a skid steer loader or similar machine, pulling the compost out of that bin and moving it into a new bin so it becomes completely stirred. Let that first pile sit and cook for another 30 days, and when you've completed the 90-day composting period, going through two complete heat cycles, the process should be complete.
At that time, Crawford says, the compost material should be ready for land application, or it can be reused as a carbon source for the next mortalities.
Best carbon sources include straw, rice hulls, ground hay, turkey litter, yard waste, sawdust, peanut hulls, chopped silage and wood shavings/chips. Crawford rates wood chips, sawdust and turkey litter best because they are high carbon sources. Whatever you have available in sufficient quantity to do the job at the lowest cost is your best choice for carbon material.
“We want the compost to go through two complete heat cycles, up to 140 to 150° F,” he explains. To check, test with a 20- or 24-in. temperature probe, available through many supply houses.
With proper composting, all major bacteria and viruses will be completely destroyed.
If the sow farm is isolated from other pig sites, don't violate the biosecurity of the sow site by bringing dead pigs from off-site nurseries or finishers back to the sow farm for composting, he emphasizes.
In northern climates, carcasses can become frozen in winter. To compost, scatter out in the pile on a daily basis rather than concentrating them.
Building a Compost Site
Many producers can use old, open-front finishing units, cattle sheds or old, vacant sow gestation barns as a compost site. Using existing facilities can significantly reduce costs and allow for a learning period before deciding if a new composting facility is warranted
“We are going to build several compost sites for sow units that are going to have bins 12 ft. wide and deep,” explains Crawford. On average, six bins will be included, one just for storing the carbon material.
A typical compost site with a concrete pad out front, concrete sidewalls and a roof can cost around $15-20/sq. ft.
Most states have formulated rules on composting. The National Pork Board has detailed information posted on its Web site at www.porkboard.org under “composting.”