Which materials should never be added to compost?
Written by
Liu Xiaohui
Reviewed by
Prof. Martin Thorne, Ph.D.Some materials create real problems when added to compost piles. Meat and dairy products attract rats and flies. Diseased plants spread germs. Persistent weeds with mature seeds, when added to gardens, regrow. Pet wastes contain bacteria and germs (E. coli). All these materials must be excluded from the compost pile to produce healthy compost.
Animal Products
- Never add: Meat, bones, dairy, fish scraps
- Risks: Attract rodents; cause putrid odors
- Alternative: Bury deep in non-edible areas or use municipal collection
Diseased Plants
- Never add: Blight-infected tomatoes, mildewed squash
- Risks: Spread diseases to future plantings
- Alternative: Solarize in plastic bags before disposal
Toxic Materials
- Never add: Pressure-treated wood, glossy paper
- Risks: Leach arsenic and heavy metals
- Alternative: Use plain cardboard or natural wood chips
Animal products decay in a much different way than vegetable matter. They produce a condition of anaerobic decomposition, which fosters the growth of harmful microorganisms. The odor will draw pests from miles around. I have seen raccoons destroy a compost heap overnight for the sake of one chicken bone. One might thus profitably enough restrict oneself to vegetable scraps and yard waste.
Composting temperatures do not kill diseased plant material. Spores of fungal diseases, such as blight, are capable of resisting heat at 160°F. The viruses responsible for plant diseases will live through decomposition. These are disseminated through the application of diseased compost. Always remove all diseased plant material. Burn or enclose in plastic bags and dispose of them.
There are safe substitutes for harmful materials. For meat scraps, use city green waste programs. Boil weeds in hot water baths before use for treatment. Replace glossy paper with unbleached cardboard. These substitutes keep the quality of compost without hazards.
Control the sorting of compost inputs strongly. Keep separate containers for acceptable and unacceptable inputs. Educate household members on the importance of using clear labels. Place a list of references near the collection sites. Practices of exclusion consistently used will yield rich compost free of contaminants.
Read the full article: Choosing the Best Compost for Gardens
