Compost Audit

Half-eaten pizza. Left-over rice. A brown napkin and potato peelings. Four Luther students are rifling through food waste from the cafeteria, not dumpster diving, but participating in Luther’s first-ever compost audit. A compost audit—similar to waste audits that have been conducted on campus in the past—is an examination of what sort of things are making their way into the compost stream at Luther. In one 24-hour period, Sustainability work study students collected compost bags from various Dining Services locations on campus—not only is there post-consumer composting offered by the tray returns in the cafeteria, but the cafeteria kitchen, Marty’s, and Oneota all practice pre-consumer (or kitchen scrap) composting. Student volunteers Mary Ferrian (’13), Chelsea Tegels (’13), and Maria Carr (’10), student worker Chris Rogers (’11), and Sustainability Coordinator Dan Bellrichard tore open these bags and sorted through their sloppy contents.

The event took place in front of the big, red barn by Baker on Tuesday, October 27th. The auditors sorted the contents into actual compostables, non-compostable food waste (including meat, dairy, and eggs), and trash. The weight of each of these three categories was compared to the total weight of compost from each location. The audit only measured each category by weight, which may underemphasize the amount of trash found, since trash is generally lightweight and food is generally very dense. Sustainability plans to measure both weight and volume in future compost audits. The results from these measurements can be found in the figures to the right and the table below.

Location Compost Non-compostable Food Waste Trash Total
Pre-consumer Caf 155 lbs. 11 lbs. 6 lbs. 172 lbs.
Post-consumer Caf 92 lbs. 10 lbs. 1 lbs. 103 lbs.
Oneota 8 lbs. .5 lbs. .5 lbs. 9 lbs.
Marty's 10 lbs. 0 lbs. .5 lbs. 11 lbs.

Trash included foil (from dish coverings), lots of wax paper, cardboard, paper desert plates, silverware, plastic cups, plastic gloves, among other things. Chicken made up a good deal of the non-compostable food waste along with meat and lots of cheesy pizza.

Sustainability is interested in the composition of compost in Luther because trash contaminating compost has been a problem at the compost pile. Trash, especially plastic products, in the decomposing pile has limited the usage of finished compost, the rich soil which your food scraps produce after about a year of decomposition. In an interview about the state of the compost pile, Grounds supervisor Paul Frana who oversees the compost pile, sifted the finished compost from last fall through his hands. Dark black soil was intermingled with plastic scraps which he explained prevented the soil from use in plantings on campus for aesthetic reasons. Sustainability hopes that information on the make-up of compost from various locations on campus will aid efforts to reduce trash entering the compost stream.

Perhaps more importantly, the findings of this compost audit and future audits like it will be used in conjunction with data from audits of waste from Dining Services locations to give information on how much of the food waste produced at each location is actually composted and how much is thrown away. Sustainability aims to use this information to identify problems with the existing compost system and make changes to reduce food waste and make the most of the soil produced by composting.