Southwest Environment

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Department of Soil, Water and Environmental Science
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UA ‘Composting Cats’ turn food leftovers into soil amendment

By Bradley Schmitz

alex Harris turns the compost pilePhoto by Brad Schmitz
Composting Cats Co-manager Alex Harris turns the compost pile on April 26 at the Campus Agricultural Center
Composters dump bins and thrust shovels into large piles of half-eaten food leftovers at the Campus Agricultural Center on Roger Road and Campbell Avenue. University of Arizona students are lifting trash bags and operating tractors to create a sustainable resource.

“Collecting and loading the food waste is a lot more fun than most people would think. It is exciting to see how much waste is being added to the piles for composting, instead of going to the landfill,” said Alex Harris, an undergraduate chemical engineering student and co-manager of the Composting Cats.

Composting Cats is a team in the Students for Sustainability Club that is collecting food waste and green waste around campus to transform it into fertilizer, or a product that can enrich and amend soil. According to the club’s website, this project made the UA the first student-organized and student-employed composting university in the nation when the first composting began on Jan. 31.

“The compost project is very ambitious. It’s large scale. We’re looking to produce large quantities of compost,” said Chet Phillips, graduate assistant for Sustainability for the Associated Students of the University of Arizona and head of the composting project.

Monday through Friday, five part-time paid undergraduate students collect compostable food waste twice a day from restaurants at the Student Union Memorial Center and transport it to the compost site. Even restaurant employees help by carrying bins of compostable waste to the loading dock at the basement of the Student Union for the transfer truck pick-up.

food waste decays to form compost

The restaurants currently donating food waste are Canyon Café, Three Cheeses and a Noodle, Starbucks, Chic-Fil-A, Café Sonora, IQ Fresh, and the union’s main kitchen, the Cactus Grill. The restaurants Burger King, Panda Express, and Papa John’s were not asked to participate because they are not owned by UA and do not have waste applicable for composting. Participating restaurants help prepare the food waste by removing all non-compostable foods, such as dairy or meat, and sort their produce into bins.

Photo by Brad Schmitz
Recently collected food waste from the Student Union is dumped into a pile to start the decay process that will transform leftovers into compost.

“We are asking for institutional change that they have not done before, and they have really been supportive and helpful,” said Phillips. “Anytime you ask a large institution like the Student Union to change its way of doing things, that can be slow and takes getting into the routine full time. But they have really been helpful.”

Student Union restaurants are not the only sources of compostable material. In April, the project expanded its sources to include the Highland Market at 6th Street and Highland, and Raging Sage on Campbell Avenue near Grant. Home Depot representatives said they might be interested in purchasing compost product from the project team in order to sell it on their stores’ shelves.

Creating an affiliation with retail stores will help the Composting Cats reach their goal of becoming a self-sustaining project, Harris said. Selling the compost could provide a source of income that pays for employees, equipment, gas, and marketing. In the meantime, the project receives its funds from student services fees, including a recent award of $37,000 from the Green Fund.

Cooperation with other organizations besides retail stores already has proven to be successful for the project. UA Facilities Management contributes clippings from cactus plants, shrubs, and trees. The clippings need to go through a chipper-shredder so the material is small enough to decompose in two to three months. The Campus Agricultural Center supplies manure from its horses for composting.

“What we are composting is not just the food waste, but also the green waste clippings that facilities management collects on campus and runs through a chipper shredder. We combine that with food waste and horse manure to make the compost,” said Phillips.

At the site, a turner that is pulled by a tractor mixes the pile containing food waste, clippings and manure to speed decomposition. Every day, students monitor the pile to ensure that the final product will have sufficient nutrients to improve soil.

The biggest challenge in producing compost is maintaining stable pH, temperature, and adequate moisture.

The pH is monitored because an overly basic or acidic composition can be detrimental to the growth of plants. The temperature of the pile is crucial because specific bacteria grow at different temperatures. The temperature must remain between 135 and 160 degrees Fahrenheit to prevent heat-loving bacteria from contaminating the pile. Moisture speeds decomposition and helps kill pathogens.

When the process is complete, the resulting compost can then be sold or donated for agriculture and gardening.

Alex Harris turns the compost pilePhoto by Brad Schmitz
Composting Cats Co-manager Alex Harris turns the compost pile on April 26 at the Campus Agricultural Center.

“We want to bag it and brand it – something like Wildcat Compost – so that in the end, once we are up and running well, it should be a self-sustaining project that may even make a modest profit through selling the compost,” said Harris.

While the Composting Cats hope that the project can turn into a successful business venture, their true goal is to influence environmental sustainability. These leaders are trying to prevent the 2,000 tons of waste that the UA generates each year from reaching landfills.

“One of the big moves that is going to increase our quantity of food waste will be happening next year – look for new bins in the food court,” Phillips said.

The team will be introducing bins that are specifically for compost, similar to recycling bins. Students will be asked to learn how to sort compostable material into designated bins.

The composting project is an initiative to make students and the community more aware of sustainable practices. The everyday choices that people make have environmental impacts. The Composting Cats are making a concerted effort to encourage society to make these choices consciously and green the UA campus.

“We have a responsibility as an institution to lead our community and our state to do as much as we can with our limited resources,” Phillips said. “I very much believe that the University of Arizona has a responsibility to be a learning laboratory for how to live sustainably in a desert environment.”


Bradley Schmitz is an environmental science student at the University of Arizona.  


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