The dining hall proves to be the site of the first encounter many first-year students will have with the phrase “industrial composting system.” Three times a day, trays loaded with food scraps glide down the conveyor belt and vanish from sight, making it easy to imagine their contents being deposited into a giant commercial grade contraption in the back room of the dining hall. Even if this image is what the phrase industrial compost occasionally conjures, it is not an accurate representation of the process. Plenty of students are able to envision backyard composting, but the rules for those small-scale systems don’t apply to the operations on campus; meat, pizza boxes, and certain types of plant-based plastic are all allowed in an industrial compost bin.
When you throw something in the compost at Carleton, it fills a translucent green bag that will eventually be loaded onto a truck and driven 23 miles north of campus to a facility in Rosemount. Starting from the Facilities Building, the drive takes 30 minutes and leads to a dirt road and parking lot.
Upon our bumpy arrival onto the property, a man in a high-vis jacket and ball cap came smiling through the rain to greet us. His name was Jake, and I recognized his friendliness from his emails. He introduced himself as an employee of Environmental Technologies Inc. before handing out hard hats and high-vis vests and leading our group to the top of a grassy hill- the best vantage point for observing all the activity taking place around us. Seagulls were darting between long parallel piles called windrows that stretched across the property, and Caterpillar backhoes swiveled between piles, carrying dark clumps of compost. Wispy steam rose off the smaller heaps of compost in transit, and from the large stationary masses of the windrows. Heat is generated naturally as thermophilic bacteria break down organic matter. Due to this microbial activity, it can get up to 150 degrees Fahrenheit at the center of the windrow. On cold rainy days, the steam makes the high temperature apparent.
Jake walked us through the processes in our midst, putting them in chronological order. First, every load of compost brought to the facility is manually inspected for contamination by things like travel cup lids, plastic packaging, and wax-coated paper products. If the load is deemed too contaminated, it will be sent to the landfill, which is always a regrettable call to make. Not only is the extra step of transporting it from the source to the compost site to the landfill a waste of resources, but any good material mixed in with the non-compostable trash also goes to waste. If the load is contaminated but salvageable, then Jake or another employee sorts through it to remove any non-compostable items they are able to identify, until they have accumulated a usable quantity of organic material. The workable material then gets churned up in a mixer to even out the composition before it is contributed to a windrow and covered with yard waste. During the decomposition process, which lasts 9 months on average, the covering serves to insulate the windrow and manage odor. “Enough complaints about odor,” Jake points out, “can mean the end of a compost site.”
The mixer that churns up incoming loads
One operator was using a backhoe to move loads of compost onto an angled conveyor belt, which deposited it into a conical pile. Jake explained that the conveyor belt is part of a sifting process that filters out any objects larger than 2 inches, which failed to decompose during the 2-month “active phase” of composting. These items are often mixed in with new compost piles, as they can catalyze the decomposition process of the surrounding material. At the final stage, any objects ½ an inch or larger are filtered out, yielding a final product with the consistency of soil, which is then sold to a variety of customers including private community members and to the government for roadside restoration projects.
So what happens if plastic contaminates the compost?
It might be preferable to imagine that a massive windrow would not be affected by the occasional tiny piece of plastic. Unfortunately, any plastic waste that makes it into compost degrades the overall quality of the material around it. Scraps of plastic bags are especially damaging, as they collect moisture and block access to oxygen, which hinders the decomposition process.
“Composting is great, but at the end of the day it’s not a silver bullet.”
At the end of the tour, we asked Jake if he had a message that we could take back to campus and share with other students, and he wanted us to go back ready to challenge the assumption that composting was the solution to every problem involving waste. The impacts of generating gigantic quantities of waste are not negligible, even if most of the waste in question is compostable. Facilities like this one can process large volumes of waste, but it is currently running at capacity. Compost is the best possible outcome for unusable materials, but any kind of waste management is going to have an impact on the ecosystem. The ideal approach? Designing products and systems that limit wasteful behavior in the first place.
The “away” in throwing things away can be nebulous, somewhat abstract, and surrounded by misconceptions. By taking a short drive to meet the people who work at facilities like this one, it becomes tangible. By extension, the impact of the choices we make to reduce waste and contamination become tangible. It’s important to bring these things out of abstraction, and show that “away” is not distant- it’s local. The impact of every choice is absorbed by someone. Mindful material use can lessen burdens, and contamination has consequences.
Jake Duame
Written and photographed by Liesl Helminiak ’19
Waste STA