WashU’s Compost Efforts

Our campus produces a plethora of waste every single day, and the majority produced is “post-consumer”— the remains of lunchtime on the go or that stack of old notes you have finally cleaned out of your bag. While you can easily sort and dispose of everything in the many compost, recycle, or landfill bins across campus, the journey of that waste has only just begun.

Waste diversion on campus remains a top priority, with many campus partners invested in streamlining infrastructure to create the simplest system possible for consumers. Since 2012, the Office of Sustainability has been conducting waste audits to assess how far current consumer practices fall from ‘ideal’ waste sorting. Our goal is to divert as much waste from the landfill as possible. These audits provide valuable insight into evolving student behavior and the effectiveness of our education campaigns.

For the past several years, the Office’s Waste Reduction and Diversion team has been responsible for gathering waste audit data. In order to determine the amount of contamination in each waste stream, we initially weigh the contents of each bag as originally sorted by students, then we open the bags and re-sort every item into its correct category— compost, recycle, or landfill. While this may seem too close for comfort to some, we are able to determine contamination rates for each waste stream by re-weighing the bags. Specifically, for compost, our waste diversion target is 97% compost, i.e. less than 3% contamination by weight. We have made considerable progress since 2012, when statistics showed that our compost stream had a contamination rate of 8.5%; today, we are down to less than 5% contamination. While this decrease is significant, especially considering the nature of our large campus, it is imperative that we continue to reduce the amount of contamination in our compost to target levels.

Compost contamination is a tricky matter; in order to produce quality end-product, the initial source must be as contaminant-free as possible. Currently, St. Louis Composting Inc. takes compost from the Bear’s Den and charges a $6 fee for every compost bin with a contamination rate over 3%. The contaminated bin contents are then sent to the landfill.

In an effort to determine our current levels of contamination, the Office of Sustainability recently conducted a visual audit of the compost stream in Bear’s Den. In the photos below, Sustainability Manager Cassie Hage is looking for landfill or recycling items contaminating the compost. She is going through compost bags one by one and taking the landfill and recyclable items out. You can see paper cups and paper pizza boxes do not belong here, as well as soft plastic bags or Styrofoam.


Sorting Correctly: 

At WashU Dining Services locations, the most common compostable items include food waste, to-go boxes, and napkins.

It is important to remember that not all plastics are recyclable. Pay attention to the number at the bottom: #1-5 and 7 are recyclable. Other recyclable items include paper and glass.

Landfill items include plastic #6, wrappers, and Styrofoam. Please pay special attention to plastic utensils, which belong in landfill, as well.

Compost Explained:

A pile of decomposed compost can be transformed into an entirely new material. It contains a full spectrum of essential plant nutrients. Instead of being buried underground with other landfill items, it can be used in complement with fertilizers to enrich the soil.


In the photo above, Cassie is showing the items she picked out. They are mostly paper cups, paper pizza boxes, plastic utensils, and plastic wrappers.

Photo credit: Adeline Shen

This article was written by the Student Associates on our Waste Team. Read their bios.

150609_Auggie_Mense marissa-150x150 Adeline_Shen_Cropjpg