Avoid these 8 in your compost

Black walnut tree leaves or twigs releases substances that might be harmful to plants
Coal or charcoal ash might contain substances harmful to plants
Dairy products (e.g., butter, egg yolks, milk, sour cream, yogurt) create odor problems and attract pests such as rodents and flies
Diseased or insect-ridden plants might survive and be transferred back to other plants
Fats, grease, lard, or oils create odor problems and attract pests such as rodents and flies
Meat or fish bones and scraps create odor problems and attract pests such as rodents and flies
Pet wastes (e.g., dog or cat feces, soiled cat litter) might contain parasites, bacteria, germs, pathogens, and viruses harmful to humans
Yard trimmings treated with chemical pesticides might kill beneficial composting organisms