By Adam Hady, University of Wisconsin Extension Agriculture Agent, Richland County
Over the past few years there have been many changes to the rendering landscape. There are fewer rendering companies and greater regulation on the industry increasing costs for pick up on farm. As producers look to alternative options to the traditional rendering company, the question to on-farm disposal starts to arise. One option for producers to consider is on farm composting. Advantages to composting include increase in biosecurity from the standpoint of less traffic entering the farm and the potential for mortalities to be handled and properly disposed of in a timely manner. In addition to limiting traffic and quick disposal, proper composting can destroy most pathogens, weed seeds and insect eggs, while providing an environmentally sound and stable nutrient that can be utilized in a nutrient management program.
What is composting? Composting is an aerobic recycling process where microorganisms break down organic material in a controlled environment to produce a stable product called humus. There are many ways to compost livestock mortalities; however, there are a few basics that are universal to all systems. The key to proper composting is providing microorganisms the proper environment to grow and rapidly break down the mortality. There are five basic components that need to be considered for the optimum environment: moisture, oxygen, carbon to nitrogen ratio, heat, and pH. The primary nitrogen source is the mortality, and so the carbon ingredient must be added. The carbon source is usually from a source called co-compost or bulking material. Common co-composting materials are: sawdust, chopped cornstalks, corn silage, chopped straw, woodchips, bedded pack manure, separated manure solids, chopped hay, and compost.
To compost mortality, put down a layer of co-composed about 24 inches deep and in an area large enough so there is 24 inches of space between the mortality and the edge of the pile. Next is to lay the mortality on its side. The abdomen may be lanced to reduce bloating in the composting process. Then cover the mortality with another 24 inch layer of co-compost. The pile will then reach a temperature range of 110-150°F. This first heating cycle will decompose most of the soft tissue, within three to six months. When the pile temperatures drop below the range, it can be turned for a second heating. After the second heating, the mortality will be reduced to a few brittle large bones. At this point the compost can be utilized as a soil supplement.
For more information on composting mortalities, the complete fact sheet can be found here.