Purdue News
Purdue News
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August 1998
Composting livestock waste provides benefitsWEST LAFAYETTE, Ind. -- As livestock operations continue to grow in average size, one problem many of them share is what to do with all of the waste they generate.
Dairy farms scrape the stalls daily and spread the manure on farm fields, but hog farms, beef feedlots and poultry operations all have problems with what to do with all of the manure they produce. Purdue University researchers have found that composting waste from livestock operations can be an efficient way to manage the waste with less cost. Composting also virtually eliminates smells and runoff problems. Researchers Larry Wood and Mark Hamilton of the Department of Animals Sciences and Stephen Hawkins, assistant director of the Purdue Agricultural Centers, have been conducting a pilot project at the Purdue Animal Science Research Center, which has 400 head of livestock. They have found that composting offers many advantages to livestock producers. "Before this we had to do a daily scrape and haul," Hawkins says. "In all weather, 365 days of the year, we had to spread the manure on the fields. It was hard to find good people to do it, it was hard on the equipment, and the constant driving across the fields was causing soil compaction. "We've gone from spreading manure on a daily basis to spreading compost five or six days a year." Composting is also safer for the environment than stockpiling manure, according to Hawkins. "Stockpiled manure is not environmentally stable, which poses some safety concerns," he says. "There is the possibility of leachate moving off-site and into nearby streams. If the manure is spread on fields during the winter, it may not decompose, and then it can run off the fields into streams when it rains. Composting allows the manure to stay in a managed holding pattern until the time is right to apply it." Many livestock farms use lagoons to handle manure, but these have a strong odor and can become clogged with the manure solids. "It just turns to a big sludge pit," Hawkins says. Even if the lagoon doesn't become filled with solids, it still requires the producer to stir it and to periodically pump it out, he says. According to Hawkins, composting manure solids offers these advantages for the medium to large livestock producer:
On the Purdue research farm, the compost is applied to alfalfa fields after the first cutting. "We use a standard manure spreader to spread it on the fields, so we're not inventing anything new there," Hawkins says. He suggests that the finished compost also could be sold to landscaping contractors or given away to neighbors in a suburban setting to build good community relations. The Purdue composting facility, which was built with a grant from the Indiana Department of Environmental Management, uses a 1.3-acre site near the Purdue dairy barns. The Purdue dairy herd is made up of 400 animals that produce about nine tons of manure solids a day. When the composting site is at capacity, there is room for 13 rows of composting material. Each row is approximately five feet high, 10 feet wide and 250 feet long. The rows are turned using a specialized windrow turner. The site development costs for the composting project were approximately $4,600, which included bulldozing a slope, berm, and retention pond (to capture rainfall runoff); adding rip-rap, an overflow pipe, and perimeter fence; and labor. The major startup cost for the composting project was a pull-type windrow turner, which was purchased in 1996 for $19,400. The windrow turner allows faster turning of the compost and a better end product. "The turning can be done with common farm equipment, such as a front-loader tractor and a manure spreader, but that method is more time-consuming," Hawkins says. "We can turn the entire site in about two hours." In addition to the windrow turner, a carbon dioxide tester, thermometer and pH meter were purchased for $1,020. Since 1995, the operating costs have averaged approximately $4,500 per year, which includes labor, site maintenance (additional grading, mowing, etc.), and equipment depreciation. "We're not trying to make the best compost possible," Hawkins says. "That's not our objective. We're trying to reduce costs and reduce chances of pollution. You could make it look like the stuff in the store, but we just do it to solve a problem and eliminate the smell."
Source: Stephen Hawkins, (765) 494-8367; e-mail, seh@aes.purdue.edu Writer: Steve Tally, (765) 494-9809; e-mail, tally@ecn.purdue.edu; Web, www.agcom.purdue.edu/AgCom/homepages/tally/ Purdue News Service: (765) 494-2096; e-mail, purduenews@purdue.edu
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