Wisconsin Natural Resources magazine

Wisconsin Natural Resources magazine

UW-Oshkosh processing compostable materials in its anaerobic digester © Dana Kampa

UW-Oshkosh processes compostable materials in its anaerobic digester on a 28-day schedule, using some of the products to produce energy.
© Dana Kampa

August 2014

Fueling the food of the future

Scrap composting is catching on.

Story and photos by Dana Kampa

There is a growing trend in residential food composting in the United States, and now Wisconsin. Cities like Oshkosh and Madison are taking what experts call the "next logical step in organics recovery."

The University of Wisconsin–Oshkosh has started its own composting program, turning food scraps, yard materials and agricultural waste into renewable energy with its dry fermentation anaerobic biodigester of German design.

During a tour of the facility, UW–Oshkosh graduate student Brooke Koenig explained how the organic scraps are converted into gas and liquid materials. A dump truck mixes the scraps in the mixing bay to break them down, releasing methane gas. The facility receives materials weekly from local farms, restaurants and the campus.

"Weíre feeding the piles with healthy organisms and lots of nutrients," Koenig says. "I want people to understand that [residential food composting] is not a harmful process to the environment."

Koenig says the facility staff takes many measures to ensure environmental safety and encourages people to learn more about the composting process.

"This process is so powerful. It's really going to help this whole nation, "Koenig says.

More than 2.55 million households nationwide are served by curbside food scrap collection and 18 states have municipalities collecting residential food scraps, according to the Composting Council Research and Education Foundationís (CCREF) "Curb to Compost" website. A tool kit on the site (compostfoundation.org/curb-to-compost/) contains resources for getting started in food scrap collection. The kit also defines residential food scraps as household waste that used to be alive, such as produce, coffee grounds, food-soiled paper and plant trimmings.

CCREF Executive Director Lori Scozzafava suggests that diverting food scraps is the next logical step in organics recovery.

"Only 2.5 percent of food scraps are recovered in the United States, so there is incredible room for growth in this area," Scozzafava says. "This is an opportunity for community leaders to improve local environmental conditions and waste management practices, and save taxpayer dollars simply by collecting residential food waste."

Some cities give residents a small kitchen compost pail and a larger outside bin, which the residents fill over the course of one or two weeks. The city then collects the scraps along with trash and recyclable materials.

Although Wisconsin cities are beginning pilot compost programs, they are only able to serve a limited number of households, explains DNR Recycling and Solid Waste Section Chief Brad Wolbert. Programs have to implement reliable and efficient ways of eliminating odors and sorting out non-degradable materials such as plastic bags. The Department of Natural Resources revamped its composting facility regulations a couple of years ago to make it easier to start a commercial food composting operation.

The city of Madison launched an organics collection pilot program in 2011 and diverted over 300 tons of material from the landfill over two years. The program has collected from 550 households and about six businesses since June of 2011 and plans to expand, adding 1,600 households and 25 to 30 businesses.

"I think the goal needs to be to divert as much organic material and organic waste as possible from the landfill," says Madison Recycling Coordinator George Dreckmann.

Madison also plans to build an anaerobic digester. Anaerobic digestion is a series of biological processes in which microorganisms break down biodegradable material in the absence of oxygen. One of the end products, biogas, can be turned into electricity and heat, or renewable natural gas and transportation fuels.

Other advantages of the digester include odor containment at the composting site and the cityís ability to handle more and a broader spectrum of materials. Contaminated paper, such as greasy pizza boxes, canít be recycled, but could be composted in the new facility. The Department of Natural Resources and city of Madison have exchanged ideas while working on plans for the digester.

Dreckmann adds that he is intrigued by the prospect of agricultural digesters accepting food scraps as a feedstock to increase profitability for farmers and divert other materials.

"Food scrap composting makes a heck of a lot of sense and itís better than a landfill," Dreckmann says.

Dana Kampa is a communications specialist for the DNRís Office of Communications.