As a senior environmental biology major, I have always been very interested in biology and natural processes. Since I began working as a student leader on the Zero Waste team at the Hanley Sustainability Institute during my freshman year, my interest has specifically focused on composting. With this experience, I have also worked at the EPA-regulated Class II composting facility at “Flyer Farm” located at Old River Park.
Throughout my years, I have dealt with a lot of compost on campus as we run the office and neighborhood composting programs. I have seen our composting program continue to grow in many ways. This year, Flyer Farm has begun to accept cooked meat and dairy products into its composting in-vessel. Previously, this was not permitted, and only fruits, vegetables and paper products could be composted on campus.
I wanted to learn more about this process, so I went to Flyer Farm to interview Patrick LaPerle, the Urban Agriculture and Compost Manager in the Office of Energy and Sustainability. In addition to answering my question about how they were able to accommodate this change, Patrick also gave me an in-depth lesson on the biology and science behind how composting works.
In a perfect world, meat and dairy should not be composted on a small scale. As the food breaks down, it emits a bad odor, attracts vermin and disrupts the entire chemistry of the compost. For Patrick, accepting meat and dairy is not an issue due to the sheer amount of compost collected. On average, one ton is composted daily at Flyer Farm, with only about 5-10% of that weight being meat and cheese. In these small quantities, meat does not have detrimental effects on the composting process.
Patrick has an agribusiness degree, and he uses this background to curate the perfect compost formula. There are three main categories of compost: green, brown and neutral. The green material typically consists of food scraps and plants, which add nitrogen to the compost, as well as moisture and proteins needed by the decomposers for fuel. The brown material includes dry leaves, wood chips, sticks, etc., and provides carbon and structure, helping aerate the compost so it doesn't become too moist and moldy. The neutral material does not add any significant carbon or nitrogen, but instead acts as a bulking agent. Most of Flyer Farms’ neutral material comes from the compostable containers provided in UD’s dining halls. At a minimum, the carbon-to-nitrogen ratio should be 1:1, and preferably 2:1, to generate heat and promote adequate decomposition of the materials.
This ratio of greens and browns creates the perfect environment for aerobic microorganisms to thrive. When the microorganisms eat the organic material, they break it down and release carbon dioxide, water and heat as byproducts. This heat allows the material to compost efficiently, as it must reach 135°F and remain in the composter for a minimum of 3 days to kill any harmful pathogens. Compost also requires good moisture levels of 40-60% and oxygen aeration levels of 10-20%, in addition to heat. The carbon-to-nitrogen ratio at Flyer Farm is closely monitored, resulting in high-quality compost verified by lab testing.
It has been so educational to learn about the biology and chemistry of composting, especially as a future environmental biologist. Having the opportunity to apply what I have learned in the classroom to my work on the Zero Waste team has been invaluable these past few years. As I get closer to graduation next semester, I am excited to apply this knowledge and continue pursuing my passions, combining biology with sustainability.