Why Contamination Ruins Compost: The Importance of a Clean Stream

Composting is an excellent way to reduce landfill waste and create a nutrient rich soil amendment. Imagine a thriving community garden, its soil enriched with compost made from yesterday’s food scraps. For compost to fulfill its potential and nourish the soil, it must remain free of contamination. Now, picture that same garden, the compost tainted with non-compostable materials like produce stickers, glass shards, and conventional plastic forks – this is the reality when contamination enters the compost stream.

Breaking Down Composting and Understanding the Basics

Composting is the natural process of recycling organic materials like yard trimmings, food scraps, and certified compostable packaging into decomposed organic matter that can be used as a valuable soil amendment. This process is a powerful method for reducing waste, cutting methane emissions from landfills, and improving soil health by boosting water retention and preventing erosion. However, compost can only effectively improve soil quality if the organic stream remains clean. When non-compostable materials, such as conventional plastics, glass, metals, and produce stickers end up in the compost mix, they can easily derail the entire process.

How Contamination Ruins Compost

At commercial composting facilities, incoming organic materials such as yard waste, food scraps, and certified compostable packaging arrive in a mixed blend. Unlike recycling facilities, which are designed for multi-material sorting, compost facilities typically aren’t equipped to separate different materials. This means that non-compostable contaminants mixed in with the organic waste must be manually removed.

Contamination occurs when materials that aren’t intended to break down at a compost facility, such as plastic products, glass, metal, or rubber, get mixed in with the organic waste. While seemingly harmless in small amounts, these contaminants can create big problems because they don’t decompose. And, because most compost facilities aren’t set up for advanced sorting systems, these non-compostable items create a rippling effect across the facility that disrupts the entire composting process, resulting in longer processing times, additional labor costs, and can even render the final compost product unusable. On top of longer operational times, if a compost load arrives that is heavily contaminated, the composter will typically send the load of non-compostables to landfill, resulting in additional costs.

As you can imagine, the cost of dealing with contamination is substantial. In a recent study conducted by Closed Loop Partner’s Composting Consortium, they reported that an average of 21% of composter operating costs is spent on contamination removal.

How You can Mitigate Contamination

The good news is that contamination is preventable, and the best way to stop contamination is at the source, by ensuring that only approved materials enter compost bins. You can do your part by familiarizing yourself with what materials are accepted at your local composting facility and being mindful of what you toss in the compost bin. When you approach a compost bin, take a moment to ensure that you remove produce stickers, plastic wrap, and any other non-compostable packaging elements before you dispose of food scraps and approved compostable materials into the bin. If you are not sure if something is compostable, it is best to follow the rule “When in doubt, throw it out” - meaning toss it into the landfill bin.

#KeepTheStreamClean

Bottom line: Contamination ruins compost. That’s why we created a program to remove it. Check out the CIRC page to learn more about how you can contribute to cleaner, more effective composting efforts!