While your worms will eat a lot of different scraps, there are items you shouldn’t feed your worms. Some items won’t break down, some, the worms won’t like, and others that are flat out toxic to them.
The problem with attempting to compost meat is it will rot before the worms get to it, and it’ll attract plenty of unwanted pests, not to mention the smell is awful. Cooked meat is bad; raw meat is even worse.
Some experienced vermicomposters have successfully composted cooked meat scraps, but that is only under some very specific conditions. Decaying meat can also cause other problems with the ‘good’ items you’ve placed in your compost bin, like fruit or vegetable scraps.
Oily Foods, Dairy, or Bones
Similar to meat, trying to compost oily foods, dairy products, or bone scraps will only result in a putrid smell surrounding your compost bin. While your worms might eventually get rid of the scraps, the smell indoors will be too rotten to stand or will attract some unwanted critters outdoors.
Citrus Fruits – Lemons, Limes, and Oranges
The acidity of citrus fruits is the main issue. Combined with the oils contained in their rinds and you should be cautious if considering adding these to your bin. Fruit flies are very likely if you choose to place these in your bin. However, if you’re persistent in using these in your compost, it’s recommended to bokashi them first, then place them in your vermicompost bin.
Onions, Garlic, and Spicy Foods
You cry when cutting them, your worms cry when you add them to their home! But in all seriousness, the odor is the issue here. As you know, if you’ve ever cut onions, they’ll make you cry because of an enzyme that combines with the moisture in your eyes to create sulfuric acid. There’s likely a similar effect when the onion is combined with a moisture-rich worm bin.
Garlic also has a strong odor, and spicy foods have irritants the worms don’t like. Leave the spicy peppers, and any other hot items out!
With the possible exception of rabbit droppings, leave out the animal poop. That refers to all animals, cats, dogs, cows, horses, etc. Cat and Dog waste contain parasites and viruses that are harmful to your worms. Cow and horse waste may be used, but only after it has gone through some additional wait time before being added to the bin.
3P’s – Plastics, Pesticides, and Processed Foods
Plastics do not breakdown, nor will your worms eat them; maybe a different type of worm will, though. Any grass or other yard waste that has been treated with pesticides is a bad idea, and just as processed foods are bad for you, they are bad for your worms. In addition to plastic, keep out other man-made materials such as metal, glass, or processed wood or wood shavings.
Any paper products that have a shiny or glossy finish. Magazines, a lot of different ads, pamphlets, or handouts fall into this category. Copy paper or paper that has been printed on from your home printer is likely a bad idea too. The paper has likely been treated, and the ink is not safe for your worms. Most newspapers are okay since most are printed with soy-based ink.
You can put a lot of different lawn clippings and scraps into your bin, but generally speaking, keep out any plants you wouldn’t want to be touching. This includes poison ivy, poison oak, and poison sumac. Just like spicy foods, these plants are irritants and are only going to be problems for your worms.
Twigs are too big for your worms to do anything with. If you plan on composting twigs or branches, be sure to them through a chipper or shredder, so they’re in smaller, more digestible pieces for your worms. The size of shavings you see in small pet bedding is the ideal size you’ll want to reach before placing them in your bin.
Remember, your worms are delicate! While there are plenty of things they can eat, there are plenty more they can’t! If you’re unsure of an item, one way to test the waters is to remove about 20 worms and isolate them in a smaller container, like a 2-3 gallon bucket. Place some dirt, and a small amount of the questionable item in there and see how they do!