What not to put in garden compost comes down to a short compost no-go list. The bad list covers meat, dairy, oils, and pet feces. It also covers weed seeds, sick plants, sprayed grass, glossy paper, plastic, and black walnut leaves. Each one brings odor, pests, or harm to your crops.
I made the meat mistake just once. After a summer cookout I tossed leftover chicken bones into the back pile and went to bed. By the next week I had a regular rat trail to and from the bin. The visits lasted three full weeks before I dug the bones out and sealed the heap.
Months later I tried to sneak a small dish of bacon grease into the same bin. The pile turned slick and sour within days, and crows showed up to scratch through it. That was my last fat dump in a backyard heap.
The why behind each ban is clear. Meat, fish, dairy, and oily food rot in a smelly way that pulls in rats, raccoons, and flies. Pet feces from dogs and cats carry parasites and bacteria like E. coli that can survive low pile temps. Grass clippings from yards sprayed with weed killer hold those toxins for months and damage your tomatoes the next year.
Some pile contaminants hide in plain sight. Black walnut leaves and bark contain juglone, a plant toxin that kills tomatoes, peppers, and many other crops. Wisconsin Extension flags this as a top exclusion for home piles. Glossy magazines and color flyers have coatings that resist breakdown. They may leach metals into your finished mix.
Weed seeds and diseased plants compost poorly in cold or backyard piles. The edges of a heap rarely hit the 131°F (55°C) for 3 days needed to kill tomato blight, clubroot, or thistle seeds. Those bugs ride your spread compost right back into the bed next spring. Compost pests like squash vine borers can also survive a half-warm pile and hatch fresh in summer.
Skip dryer lint from synthetic clothing, charcoal ash from briquettes, and any treated wood scraps. Each adds chemicals you do not want in your salad. Coal ash is high in sulfur and heavy metals. Pressure-treated lumber sheds copper and chrome as it breaks down. Stick to plant matter and the four basic browns you know are safe.
Banned items still have a home. Send meat, dairy, and oily food to a bokashi fermenter, which pickles it in a sealed bucket for 2 weeks before burying. Drop pet waste compost at a curbside city program that runs hotter and longer than any backyard rig. Burn or trash diseased plant matter so no spores spread. Send glossy paper to your curbside recycling.
When in doubt, leave it out. Your pile and your plants will thank you next harvest.
Read the full article: Garden Compost: Complete Home Guide
