If you are composting for a garden, avoid placing meat or dairy products in the compost. This will likely attract pests like rodents and flies, and it may also contribute to odor. The same is true for oils, fats, and lards. Some ash, like that from coal or charcoal, may contain harmful chemicals that can hurt plants. You’ll want to avoid composting pet waste as well, as it could contain harmful bacteria or germs.If you're composting for a city or town pickup or drop-off, find out what is and is not acceptable. Depending on the process and machines used, certain items that might not be intuitive can be included in the disposal. Each town, community, and city will have its own guidelines and rules.