Composting only works when the right materials go in and the wrong ones stay out. At Dakota Prairie Composting, our mission is to turn food scraps, yard waste, and wood waste into high‑quality compost that restores soil and protects the environment. Contamination is one of the biggest challenges composting facilities face, and even small additions at home or work can impact the finished product.
By properly sorting your compost, you help us create cleaner, healthier compost and keep organic material out of landfills. Below are the top 10 most common contaminants we find in compost loads, along with simple tips to avoid them.
1. PLASTIC BAGS AND PACKAGING
Why it’s a problem:
Conventional plastic does not break down during composting and must be removed by hand or equipment, adding time, cost, and contamination risk.
How to avoid it:
Only use BPI-certified compostable bags and products. If it doesn’t have the certification logo, it doesn’t belong in compost, even if it says “biodegradable.”
2. “BIODEGRADABLE” OR “ECO-FRIENDLY” PRODUCTS
Why it’s a problem:
Many products labeled “biodegradable” are designed for landfills, not compost facilities, and may never fully break down. Neither term is regulated by any governing body. They are often used just for marketing purposes. Neither term means compostable.
How to avoid it:
Stick to items that are clearly marked BPI-certified compostable. When in doubt, leave it out or check our acceptable items list before composting.
3. RECYCLABLE PAPER AND CARTONS
Why it’s a problem:
Items like milk cartons, juice boxes, frozen food boxes, and other coated paper products contain plastic liners that contaminate compost.
How to avoid it:
Recycle these items instead. Compost only food-soiled paper products, such as napkins, paper towels, unprinted cardboard, and pizza boxes (when accepted).
4. LARGE AMOUNTS OF GREASE AND OIL
Why it’s a problem:
Grease and oil can be hard to soak up and contained in large volumes and pose a risk of running into the stormwater. Dakota Prairie Composting does not accept loads with large quantities of grease or oil.
How to avoid it:
Scrape excess grease into the trash. Small food residues on compostable items are okay, but volumes of liquid grease or oil larger than two gallons should not be included.
5. ANIMAL WASTE AND LITTER
Why it’s a problem:
Pet waste can contain harmful pathogens and parasites that are unsafe for workers at the facility.
How to avoid it:
Never add cat or dog waste or litter to compost. These items must go in the trash.
6. GLASS AND METAL
Why it’s a problem:
Glass shards and metal pieces can damage equipment and pose safety risks to staff.
How to avoid it:
Rinse and recycle glass and metal separately. These materials never belong in compost.
7. DIAPERS AND SANITARY PRODUCTS
Why it’s a problem:
These items contain plastics, absorbent polymers, and human waste that contaminate compost and cannot be processed.
How to avoid it:
Dispose of diapers and sanitary products in the trash, never in compost containers.
8. CLEANING WIPES AND PAPER TOWELS WITH CHEMICALS
Why it’s a problem:
Most cleaning and baby wipes contain plastic fibers and chemical residues that persist in compost.
How to avoid it:
Only compost plain, food‑soiled napkins or paper towels. Wipes of any kind go in the trash.
9. CIGARETTES AND ASHES
Why it’s a problem:
Cigarette filters are plastic, and ashes or charcoal can alter compost chemistry and contaminate soil.
How to avoid it:
Dispose of cigarettes, ash, charcoal, and fireplace debris in the trash, not compost bins.
10. PAINTED, TREATED, OR GLUED WOOD
Why it’s a problem:
Treated wood products, like plywood, particle board, oriented strand board/engineered wood panels, and furniture, contain chemicals and glues that should never enter compost.
How to avoid it:
Only compost clean, natural wood waste. If it’s painted, stained, glued, or treated, it doesn’t belong in compost.
WHY PROPER SORTING MATTERS
Dakota Prairie Composting is a large-scale, source-separated organics facility, meaning we rely on customers to place only accepted materials in compost loads. Contamination slows processing, raises costs, and can affect compost quality. When everyone sorts correctly:
- More organic material is diverted from landfills
- Less time and money are spent removing contaminants
- Finished compost is cleaner, safer, and better for soil
- Minnesota moves closer to its waste‑reduction goals
WHEN IN DOUBT, CHECK FIRST
If you’re unsure whether something is compostable, the safest choice is to check our acceptable items list or give us a call at 952.233.9191 before dropping it off. A few seconds of sorting at home makes a big difference at the compost site.
Together, we can protect soil health, reduce waste, and turn today’s food scraps into tomorrow’s fertile soil.
Learn more about accepted materials and our programs.
