MeatsAny type of meat should always be avoided in the compost pile. The rotting meat will stink to high heaven, and will almost certainly attract critters like rats and raccoons. It can also attract flies, maggots, and other annoying and disgusting insects. Dispose of meats in the city or local trash pickup. The same goes for animal bones.
Dairy ProductsDairy products such as milk, cheese, and butter should never be added to compost piles. The rotting milk will give off a stench as bad as the meat. Rotting milk can also attract roaches and other nasty varmints you really don't want in your yard, or around your home.
Carnivore ManuresWhile most manures from herbivores (plant-eating animals) are good for speeding up the decomposition process, manures from carnivores (meat-eating animals) should be strictly prohibited from composting. Manure from animals such as dogs, cats, and humans have the possibility of carrying harmful pathogens, bacteria, and even parasites. Although some recommend these can be used in lawns and ornamental gardens, I recommend staying completely away from these types of manures for composting no matter what the intended purposes for it. It's better to be safe than sorry, in my opinion.
Some localities sell a compost that is derived from the local sanitation and water treatment facilities. Different locations may have different names for the compost (in my local area it is called Nutri-Green®), but it is all pretty much the same thing - composted sludge that is left over after the sewage and water treatment process. I strongly recommend avoiding this stuff! There's no telling what is in it, and is not safe for edible gardening, in my opinion. Remember, this is the left over sludge from human waste and storm water treatment. Not something you really would want in your vegetable garden and lawn!
Cooking Oils and GreaseAnother material to avoid when composting is cooking oils and grease. These items do not break down that easily and can contain fat and other by-products that will also attract unwanted animals. Cooking oils, grease, and other liquids containing oils and fats should be disposed of properly according to local and state laws.
Plants Treated with Pesticides or HerbicidesNever put plants, grass clippings, or leaves in a compost pile that have been treated with pesticides, herbicides, insecticides, or other chemicals. These chemicals will not break down and will incorporate within the compost. Once you spread the contaminated compost into the vegetable garden the soil is then contaminated with those chemicals. The chemicals are also very dangerous to the beneficial microbes that are responsible for creating the compost. It's much better to bag up the chemically treated plant materials and dispose of them properly. If you question whether a certain material has been treated or not, err on the side of caution, and leave them out of your compost.
Non-Biodegradable MaterialsAny item such as plastic, rubber, polyester, and other synthetic materials should not go into the compost. These items will not break down and could leach unwanted chemicals into the compost. Also, leave baby diapers, cat litter, and charcoal ashes out of the mix. Check with your local sanitation department about their recycling program for plastics and other recyclable materials.
Plants With DiseasesDo not ever put diseased plants into your compost. An almost guaranteed way to spread the diseases throughout your lawn and vegetable garden is to place a diseased plant in the compost. The disease will just harbor in the compost, and then be quickly spread when you use the compost in the vegetable garden. Place diseased plants into a clear plastic bag and leave it out in the sun for a few days, which will help to kill the disease. Chunk the bag and all into the garbage. Even if you suspect a plant may have a disease, pull it up and dispose of it properly. Also, remember to throughly wash your hands after handling a diseased plant to decrease the risk of spreading it to other plants.
Keeping Your Compost Healthy and SafeIt is not difficult to keep your compost healthy and safe to use. By avoiding these items in your compost, you will have high quality compost that's perfect for your vegetable garden. The first step is adding materials that are useful, and avoiding the things you should never compost.
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