Each year, tons of grass clippings, leaves and other yard refuse head for landfills. But at the Illinois State University Research Farm near Normal, Ill., hogs are helping convert campus and city yard waste to valuable compost.

In the process, two other benefits are being realized:

  • The farm is avoiding odor problems from conventional hog-manure spreading on its crop land, even with urban neighbors nearby.
  • It’s taking some of the load off of area landfills.

For three years, animal scientist Paul Walker and his associates at Illinois State have conducted farm-scale compost research with swine manure, grass clippings, leaves and wood chips. In addition, they have ongoing compost research studies with corn stalks.

Work at Illinois State has shown that standard farm equipment can be used to process compost:

  • A rear-delivery, apron-type manure spreader, with beaters removed, can form the compost rows. Also, the spreader can be used later to spread the cured compost onto crop land.
  • A honey wagon modified for side discharge (see accompanying photos) can be used to spray swine slurry on top of the vegetable-matter windrows.
  • A front-end loader works to turn the compost windrows and also breaks down stacks of chopped corn stalks.

Swine slurry should be mixed into the vegetable matter as soon as possible, Walker advises. “Aerobic action begins quickly and odor from the swine manure dissipates. Introducing air promotes aerobic action that reduces and eventually eliminates odor.”

The arrangement at Illinois State involves pumping swine manure from pits under the buildings of the farm’s 125-sow, farrow-to-finish operation. The 2.5- acre compost site has 12, 500-foot rows. Vegetable matter is deposited in windrows 5 feet wide by 5 feet high and liquid swine manure is sprayed onto those at the following rates: 350 pounds per cubic yard of green grass, 665 pounds per cubic yard of dry leaves, 1,500 pounds per cubic yard of wood chips.

With grass clippings, no additional manure is sprayed after the initial application and compost is ready to use in six to eight weeks. But with wood chips and dry leaves, spraying frequency depends on dryness, coarseness and humidity.

“During the first two weeks,” he says, “we spray manure on chips or leaves every other day and then as often as needed to keep the compost damp. We want to keep the carbon-to-nitrogen ratio at 25:1 or 30:1 for six weeks. Then we let the compost mature for two to four more weeks, so it is 8- to 10-weeks old when we spread it on crop land.”

To make fully-cured compost with liquid swine manure, Walker’s recommended schedule is:

  • First week, turn the compost daily.
  • Second through fourth week, turn twice a week.
  • Fifth and sixth weeks turn weekly with grass. When using chips or leaves, turn weekly from the fifth through the eighth week.

“In six weeks,” adds Walker, “the compost usually smells like soil but if made with chips or leaves, we give it a couple more weeks as a precaution.”

Compost is spread on crop fields using the same conventional, tractor-drawn spreader that the workers use to spread the vegetable matter into rows. “Because the cured compost is virtually odor-free,” says Walker, “we can spread it onto land at our convenience, unlike with straight swine manure, and not bother neighbors whose homes are right across the street.”

In corn tests, 60 tons of compost was equal to 100 pounds of nitrogen from a commercial fertilizer. The compost’s nitrogen content is quite uniform, says Walker, 1 percent to 1.5 percent.

Targeted production is 150 bushels of corn per acre. This year, corn receiving compost hit the mark. Commercial fertilizer produced 160 bushels.

“Other potential long-range benefits to crop land may also be significant,” adds Walker. “We are tracking effects on organic matter and soil tilth.”

At Illinois State, researchers also have studied corn stalks as the vegetative matter with liquid swine manure.

They are stepping up this research because of the availability of stalks at or near most Midwest hog operations.

“Another positive,” says Walker, “is a producer doesn’t need a permit to compost using a ‘homegrown carbon source’ such as stalks. But with yard and landscape waste, it varies by state.”

At Illinois State, they have experimented with corn stalks in large round bales and in different size stacks. “Big bales were difficult to roll out and were too labor-intensive. We prefer chopped stalks in five-ton stacks which are convenient to work with. Ten- or 20-ton stacks need to be broken up with an end loader and this is a lot more time consuming.”

Strictly from a fertilizer-value standpoint on crop yields, Walker concedes that you cannot justify the total cost of producing compost. “But it also contributes to soil condition. And, in a location like ours where odor control is important, composting can be a good investment.”

Walker believes the long-range profitability of large-scale compost production is in developing a Class A product that can be marketed as potting soil for nurseries and homeowners. Class B compost is for farm use. He explains, “Classification of compost as A or B is based on several factors, including particle size and degree of compost maturity.”

Because of composting’s various benefits, the Illinois State animal scientists are stepping up their research, especially with corn stalks. At the same time, they are determining the costs to produce Class A and Class B compost relative to the size of a swine operation.

For more information, you may contact: Paul Walker, Illinois State University, 149B Turner Hall, Campus Box 5020, Normal, IL 61790-5020, phone (309) 438-3881; e-mail pwalker@ilstu.edu

Facts Worth Noting

Paul Walker, animal scientist at Illinois State University, says the research shows:

  • The initial mixture required to make compost is 500 pounds of solid manure per cubic yard of landscape waste.
  • Roughly 2.2 tons of raw material ù landscape waste and solid swine manure ù decomposes to 1 ton of finished compost.