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Black Gold

By Staff | Apr 9, 2010

A drum-style turned is used twice a week to mix up the components of the compost windrows. This helps ensure that the microbes receive enough oxygen to break down the organic materials.

AMES – Though it comes from humble beginnings, dark, brown, crumbly compost is almost magical in its benefits, from its ability to improve soil quality to its embodiment of the “reduce, reuse, recycle” mantra.

Small mountains of this “black gold” are produced every year at Iowa State University’s composting facility south of Ames, which handles thousands of tons of solid organic materials annually that come from various campus sources.

“Our goal is to turn manure and livestock bedding, leaves, organic greenhouse waste, biomass research waste like corn cobs and switchgrass, and food scraps from campus dining facilities, into a useful product,” said Steve Jonas, who manages the compost facility. “We’re always looking for ways to make the process better.”

The compost facility, which was built in late 2008 and is located about a mile from the southwest edge of Ames, includes seven, 80-by-140-foot hoop barns to contain the compost. The concept for the facility was developed when ISU built its new dairy farm south of Ames a few years ago. In fact, the dairy farm, which includes 450 head of milking cows, supplies a significant portion of the inputs for the nearby compost facility.

After the liquid is separated from the dairy manure, the manure solids and sawdust bedding are mixed with carbon-rich campus waste such as leaves, cornstalks and livestock bedding to form windrows that will eventually produce compost.

“While the former dairy farm did some composting, the old site was smaller and it wasn’t covered,” said Jonas, who noted that the new facility is designed to handle 20,000 tons of waste per year. “Today, we handle about 10,000 tons of waste and produce 4,000 to 5,000 tons of compost each year.”

Going green

Composting is a natural process that relies on microorganisms to break down organic material. The transformation works the best when there is a 25-to-1 or 30-to-1 ratio of carbon to nitrogen sources in the organic waste, although the system is fairly forgiving, said Jonas, who said the range can include a 20-to-1 or 40-to-1 ratio.

When truckloads of organic waste from various campus sources are delivered to the ISU composting facility, Jonas moves the materials into the various hoop barns and makes windrows that are seven feet tall and 14 feet wide. About three windrows can be made inside one hoop barn.

The windrows must be turned about twice a week to ensure that the microbes receive enough oxygen to break down the organic matter. “You want 50 percent moisture and a pH of about 7 in a compost pile,” said Jonas, who notes that 10 percent oxygen in a compost pile is ideal for microbes. “If a compost pile doesn’t receive enough oxygen, the process will start to slow significantly.”

Four of ISU’s hoop barns include concrete floors, while three have asphalt floors, which make it easier to turn the compost piles regularly.

As the microbes break down the organic material, the temperature in the piles climbs to 140 to 160 degrees, which kills pathogens and inactivates weed seeds.

Food scraps and biodegradable dessert cups from ISU’s dining facilities are among the materials that break down the fastest in the compost windrows.

“This compost facility allows ISU Dining to be a part of an all-university project that brings waste full-circle,” said Nancy Levandowski, ISU dining director.

The composting process, which produces no odor when managed properly, can continue throughout much of the year, said Jonas, who added that the system starts to shut down when outside temperatures hit 10 degrees below zero.

Compost uses abound

After about 12 weeks, the composting process is complete. ISU then allows the compost to cure for another three to four weeks so the microbes become less active and the piles cool down. The result is an odorless compost that makes a high-quality soil amendment. The finished product is used in a mix with topsoil and sand to replenish areas around construction sites on campus. The compost is also used for landscaping around campus, and at ISU’s horticultural and agronomic research farms.

The compost facility also takes separator solids from the ISU dairy farm, composts them and sends them back to the dairy to be reused for dairy bedding.

The compost facility, which is not open to the public, is designed to be an entirely self-supporting service unit. It charges by the ton to bring material brought to the facility. All compost leaving the site is weighed and charged by the ton to the department using the material. ISU is also looking at wholesaling the finished compost to various operations outside of the university system.

“Iowa State wants to be a leader in sustainability, and this compost facility contributes to that goal,” said Mark Honeyman, professor of animal science and coordinator of ISU research farms.

“Composting is a great way to demonstrate an alternative use for manure and biomass with the end result as an organic, usable product on campus. It’s intuitively the right thing to do as it takes waste and turns it into something valuable.”

Contact Darcy Dougherty Maulsby by e-mail at yettergirl@yahoo.com.

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