These are some basics when it comes to adding food scraps to a system. This is mainly for beginners but this will also have some info for ones that want to experiment a bit.
There are many ways a system can be fed but for most home/indoor systems left over food scraps will be the primary source. Some may have access to manure heaps, poultry feed, worm chow, and all sorts of other food sources but this discussion will be primarily about food scraps.
One of the first questions one may have is “how much can I add” to the system. As with all things vermicomposting it depends. The size of the system, the amount of worms, the proportion of bedding are just some factors that determine the “how much.” One thing that you may come across on various sites and videos is that worms can eat up to 1/2 of its body weight a day. This implies that if one has one pound of worms that they can throw in 1/2 pound of food scraps and it will be gone the next day…This is a fantastic way to kill your worms! Although worms are capable of these feats it happens when all the conditions are aligned. Before we dig in further, it is best to take a relaxed approach until you can see how much your worms can handle.
What type of scraps can be used?
Worms can handle a wide range of materials. One way to think about it is, if it decomposes the worms can eat it! Worms will chow down on just about anything. One important note, worms don’t actually eat the scraps…wait what?!? Worms eat on the decomposing portions of the food where the bacteria and fungi are. This is important to remember as some materials break down much slower than others and the worms won’t go after it until the decomposition starts.
For beginners it is best to stick with these types of food scraps:
- Fruit wastes – apple cores, strawberries, banana peels, and other non-citrus fruits
- Citrus fruits are generally not recommended as they can be acidic which can harm the worms. I personally use citrus as part of my feedings…what! Yes, citrus can be used but if you are new try to use it sparingly or test a small amount out…and yes I personally add pineapple to my systems
- Vegetable wastes – carrots, celery, squash, pumpkin, peppers, and other non-cruciferous (broccoli, kale, collards, etc) vegetables
- Cruciferous vegetables tend to have quite a pungent odor when breaking down and sometimes bedding cannot filter all the scent. The scent is quite horrible and if you keep a bin in a small apartment this won’t go over well. If you are new just try to limit how much you add
- Coffee grounds and tea bags
- Coffee grounds tend to break down fairly slow especially when it is clumped. The worms tend to process the grounds when they are spread out and mixed with other materials
- Bread, pasta, starches
- This material can be used but it shouldn’t be the primary food. These materials break down slower and can bring some anaerobic conditions to the system. I break this material into small pieces and haven’t had any issues using it.
Some other points about food scraps. I highly recommend that one does the following:
- Freezing the scraps
- Freezing will help with decomposition as the water in the scraps will expand causing the cell walls of the material to rupture. This will allow the worms to start processing the scraps more quickly. I put all my scraps in a bread bag and put it into the freezer when full.
- Cut up/mash the scraps
- I tend to do this after freezing and thawing the material. Breaking up the scraps into smaller and smaller pieces will allow decomposition to occur much faster. I don’t think it is necessary to use a blender since it tends to take a lot of time. However, it will break down very quickly. I do caution using blending as it can cause a system to heat up. Some heat is ok but if the worms cannot escape the very high temperatures they can die. I mash up the scraps using an ice scraper and a 5 gallon bucket.
Which foods be avoided?
In general meat and dairy should not be used. The main issue with these materials is that they take longer to break down and are not as water rich. So when it does break down it can stink quite bad. However, there are some worm composters that have had success with this material. Mark from Vernmenting has a video where he uses worms to break down roadkill. DO NOT try this as a beginner! In fact even if you’re pretty good at vermicomposting I would be very careful with this! Definitely wouldn’t want maggots in my systems!
I would also avoid using ones personal number two’s if you get my drift. This material is better suited for hot composting and should be left to sit for a long time. If one is interested in it “The Humanure Handbook” is the go to resource.
Other food sources
In addition to food scraps there are a few other materials that can be considered a food source for worms:
- Weeds and other green leafy material
- Some plants such as comfrey, dandelion, and other deep tap rooted plants can be a good food source. A bit of caution to avoid adding seeds as vermicompositing is a cold composting method and seeds will remain viable
- Worm chow, poultry feed, birdseed
- These are great sources of food that add some grit which is good for a worm’s digestion. However, this material should be used sparingly and not be the main food source
- Crushed eggshell, oyster shell flour, glacial rock dust
- This material helps keep pH levels in check and provides grit. A small sprinkling of this can be used with each feeding.
In general it is best to stick with plant based material as the food source for the worms. I also encourage beginners to be lighter on feeding until one gets a feel for it. There are sites and videos that show the awesome ability of the worms to process tons of waste, but these systems are mature and are loaded with beneficial microbes. Start slow and don’t push the system too much early on.