Home » Food Scrap Collection Programs » Is contamination in compost a big deal?

A little contamination isn’t a big deal, right?

Let’s say new regulations are put in place in your area, and your apartment building decides to implement a system to separate food scraps from trash and recycling. One day, after eating a banana, you casually toss the peel into your food scraps bin and go on your merry way, content with the idea that you’re doing good for the planet. What you didn’t notice is that the banana peel had a non-compostable sticker on it. One little sticker on an otherwise compostable banana peel shouldn’t be that big of a deal, right? Let’s follow that sticker (and other contaminants) on their journey from your kitchen food scraps bin to the end result of your food scraps becoming compost to see what is being done to keep our compost clean.

Step 1: Emptying your food scraps bin

Once your kitchen bin is full, banana sticker included, you bring it downstairs to the central waste area. There, you toss it into the building’s communal organics collection container and head back up to your apartment. What you don’t know is that, if your building’s residents haven’t been given a convenient program to follow, or the proper education, your bin could potentially be filled with hundreds of pieces of contamination.

Step 2: The hauler collects the organic waste

On a set schedule, the hauler comes around to empty the central organics waste bin. The driver will take a cursory look inside the bin to make sure no obvious contamination can be seen. In cases where a lot of obvious contamination, like plastic bags, is visible, they may be forced to leave the bin uncollected and inform the building manager that the contamination needs to be removed. However, smaller contamination like your banana peel sticker likely won’t be seen, so they will empty the container into their truck, and head to the composting site.

Step 3: Giving the organic waste to the composter

At the composting site, the truck’s load will often be inspected by the composter before allowing the truck to add their load to the composting process. If an unacceptable amount of contamination is found, the truck will have two options. They can:

  1. Comb through the contents of their load and pull out contaminants by hand until the composter determines that the load is clean enough to accept.
  2. Take the entire load to the landfill

Unfortunately, in a world where time is very valuable, it is more likely that a contaminated load ends up in the landfill. When this becomes a consistent problem, additional fees may be charged back to the sites (like your apartment building) that are deemed to have contributed to the high level of contamination.

Step 4: The composter removes contamination

Assuming the load with your banana peel sticker was accepted by the composter, it will then be subjected to a screening process that is meant to remove things like metal, plastic, and glass. Of these, metal is easy to screen out with magnets, but glass and plastic can be very difficult because they can be difficult to see. When contamination is still visible, the load may be run through the screening machine again. Once screening is complete, all the contamination (called “overs”) that was removed will then need to be shipped off to the landfill. That cost, again, is forwarded on to the end consumer.

Step 5: The composter begins the composting process

There are several different methods that composters can use. All of the main methods have been proven to properly break down an EcoSafe® compostable bag and all the food waste inside, but none of them will break down a banana peel sticker. So, if your banana peel sticker manages to sneak through all the different screening methods, it will go through the entire composting cycle and remain as visible contamination even in the final product.

Step 6: The compost is sold and used

When the compost is complete it can be sold to retail and/or commercial customers as a way to enrich soil. If a banana peel sticker is found in the compost it can devalue the product in the same way that finding a hair in your soup devalues your meal. And, even though a banana peel sticker may not adversely affect the results of using the compost, there are some contaminants that can leak chemicals and other, more serious contaminants into the soil if they are not separated beforehand.

TLDR; When in doubt, throw it out!

Although contamination is not likely to ever be completely nullified in our organic waste stream, every person doing their part to reduce it means less time, effort, and money needed to create healthy compost. When it becomes easier to collect uncontaminated food scraps, it will be cheaper for individuals, more compost will be produced, and the impact on our world will be far greater. Take the time to remove stickers and look up whether a product is compostable before tossing it in your food scraps bin. Your actions will become part of the solution.

Implement a program in your apartment building, school or community that is designed specifically to reduce contamination through familiar processes and easy education. Read about the successes that many San Francisco high rises experienced using the EcoSafe MultiRes® program and contact us for more information.

Special thanks to McGill Compost for their insight into the difficulties in dealing with contamination from a composter’s perspective. If you’re interested in composting and the benefits and difficulties surrounding it, check out McGill’s Talking Compost blog. It has lots of useful and interesting information.

Food loss and waste occur at each stage of the supply chain. The biggest proportion (about 37%) happens in the home.

ReFED, 2021