Worm compost cannot have cooked food

Worm compost cannot have cooked food

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I live in the Netherlands and it is getting fashionable to compost with worms. After investigating a few websites I noticed that most websites suggested that I cannot feed the worms leftovers from citrus fruits. This seems logical. I then started noticing that people advise against feeding the worms cooked food.

I'm no biologist but I cannot imagine a reason why cooked food is bad for the worms. Could anybody explain why this might be in layman's terms?

There are a few reasons for not feeding cooked foods to worms (Eisenia spp.) in a smaller household size worm farm. It's not because the food is cooked but what it often contains.

The earthworm used in vermiculture is usually Eisenia fetida (red wigglers) though other Eisenia species are sometimes used. All Eisenia are epigeic species meaning they live in the junction of decomposing organic matter (such as leaf litter, aging manure, rotted fallen trees) and their natural food is decaying plant matter and bacteria that are also digesting the organic matter. They don't make use of small dead animals (meat and fat).

In large scale commercial vermiculture operations, leftover and past-due-date foods from restaurants, institutions, nursing homes and schools are used along with plant matter and carboard and paper. I'm not sure how they balance cooked foods but possibly much less is used than plant matter.

The fact food is cooked isn't the problem but what's in it and/or what happens to it when added to the bin. If you have leftover vegetables and fruit that's been cooked with no added salt, it's perfectly acceptable. A certain amount of sweetened cooked fruit is also fine as the worms will eat that too. But ready-made foods usually have preservatives, salt, fats and spices added. Either worms won't eat it, leading to odour caused by mouldy rotten food, or it can make them unthrifty and even killing off your worms if it's fed them repeatedly.

Fats and meat along with cheeses and dairy products will also not be eaten so shouldn't be used. Sites about vermiculture say onions and garlic can 'burn' the worms skin which is the problem with citrus fruit. They can be used but in very small amounts and should be mixed well with their other food.

Vermicomposting for Business, Farms, Institutions & Municipalities

Wormy FACTS and Interesting Tidbits about Eisenia fedita

How to Correctly Feed Compost Worms: What, When, How and How Much

Worm composting, also called vermicomposting, is a great way to use kitchen scraps to create a nutrient-rich compost to feed your garden and keep it producing year-round. In a large container, simply shred some newspaper and leaves from your yard to create a nice loose base, then add in red wiggler worms, officially known as Eisenia fetida, and some moisture. Then you’ll be ready to start your very own vermicomposting headquarters that will create your own compost all year long. Once the worms’ environment has been created, it’s time to learn what to feed your worms, when to feed them, and how much food they will need to create the perfect nutrient-packed compost that will help you condition the soil of your garden year in and year out.

What Your Composting Worms Should Eat and Not Eat

Worms have voracious appetites, but they don’t actually eat the waste food that you put into the soil to feed them with as is. Instead, they wait for that waste food to become covered in microbial communities. In fact, your worms’ main source of nutrition comes from the microorganisms that grow in abundance on organic fruit and vegetable waste. That’s why instead of devouring the scraps that you throw in to the soil immediately, your worms will wait around until microbes begin to flourish on the surface of the food scraps. Once the microbial content of the food is high enough, dinner is served, and the food is ready for your compost buddies to eat their fill. A word of caution, however—don’t just throw any old kitchen scraps into the compost bin and hope for the best. Keep reading, and let’s dive into what you don’t want to feed them.

Do not feed your worms fatty or processed foods, such as meat or dairy products. These types of kitchen scraps will cause strong odors when they decompose that you won’t want stinking up your home. Fatty or processed food scraps will also disturb the delicate ecosystem that you’ve worked so hard to create in your composting bin, attracting fruit flies, house flies, and other pests as well as disrupting the moisture level you’ve worked to calibrate in your composting container.

Do feed your worms organic fruit and vegetable waste, including the rinds, cores, and peelings of your favorite fruits and vegetables. Feed them crushed eggshells, coffee grounds, and coffee filters (as long as the filters are unbleached), teabags, and aged manure from vegetable-eating animals, such as rabbits, horses, and cows. Be careful not to feed your worms any manure containing deworming medication (makes sense, right?) that could kill your worms.

Citrus fruit scraps are an acceptable addition to your bin in small amounts, but make sure not to overdo it. If you eat a lot of citrus fruits, you will want to limit the amount of scraps you add from oranges, limes, lemons, and grapefruits, as the peels contain a chemical that can harm red wiggler worms in large amounts. Avoid adding salt, or any salty foods, to the compost bin. Salt is really bad for worms and can kill them if it’s present in large amounts in the compost container.

Onions are another kitchen scrap that you may want to consider just throwing away instead of adding to the compost bin to be consumed. There are conflicting reports on the web, to be sure. Some composters use onions, and some do not. The reasoning behind some gardeners leaving onions out of the mix is pretty sound. As you know, onions can stink pretty badly, especially as they decompose. However, green onions in small amounts should pose no major problem.

Avoid adding oils, such as olive oil, sesame oil, or butter into your compost. Vegetable oil is okay in small amounts, but it’s best to just avoid adding oils altogether, as oils slow down or even stop the composting process completely.

When and How Often to Feed Your Worms

It is very important not to overfeed your worms when you are first starting your vermicomposting project. Your new nematode friends will have to wait patiently while the microbial organism population builds up before they dive into dinner. Be careful not to overload the compost bin during the first couple of weeks to give your worms time to settle in to their new environment a bit. Once the environment is set and you’ve added your worms, it’s important to never let them completely run out of food to eat. Remember, their food needs to grow plenty of microorganisms before they will eat it, so you will want to cycle in new food waste every two or three days.

Check the compost bin every other day. When provisions get low and the worms are wriggling around in the last bit of food waste that you gave them, it is time to add more. Don’t worry if the worms avoid the new food waste that you just added at first. They will get to it as soon as it has grown enough microorganisms to satisfy their cravings. The size of your compost bin will determine the amount of food waste you should use each time, but typically a cup of food waste every other day will be sufficient. If the worms are not eating their food to the point that it begins to build up, simply skip a feeding or two until they start to consume the end of the food waste you provided. Overfeeding the worms and not allowing them time to eat down their food supply before adding more will lead to a stinky compost bin.

When preparing the food waste that’s headed for your compost bin, chop fruit and vegetables into the smallest pieces possible so they will decompose at a faster rate, speeding along the process. Take note of how often you notice the worms consuming their food and how much food they consume each day. Once you get to know your worms’ appetite level, you can better predict how often to feed them and how much to feed them each time. There is no perfect amount or by-the-book method, so it’s up to you to adjust feeding times and amounts as is necessary. Make sure you rotate which area of the container you place the food waste into to ensure that every worm gets plenty to eat. Put the food waste three to four inches under the top of the soil to keep it from rotting out in the open and attracting flies and other pests.

Once you get the feeding schedule down to a science, the rest of the vermicomposting process is quite easy. Simply let the worms create compost, and when the time is right, mix that compost in with the soil in your garden to pack it with nutrient-rich, fertilizing goodness that your plants will thrive in season after season. Notice the impact that composting has on the amount of trash waste that you send off at the curb each week to fill up a landfill as well—not to mention how your vermicomposting hobby lessens the number of times that you need to take out the trash to begin with. Do not add water to the worm bin unless it is severely dry to the touch. In other words, don’t add water just to make more tea. Composting requires maintaining a delicate balance in the bin, and too much water will throw that balance off significantly.

Make sure to use a drip pan underneath the compost bin to collect the compost tea. Don’t let the moniker fool you—this is not a tea that you are going to want to drink. Compost tea is probably about the rankest liquid concoction anyone could possibly create, and it’s not at all meant for consumption. Compost tea is, however, a great liquid fertilizer, so collect it, then store it in a spray bottle so you can put this useful composting byproduct to use each gardening season.

How Many Worms You Need

You’ll want to start out with about 500 to 1,000 red wiggler worms, or one to two pounds of worms total. Your compost bin should be filled with a one-to-one ratio of worms to garbage. If you started out with a different balance, don’t stress out over it. Worms tend to multiply very quickly, so you will most likely have plenty of worms in due time, even if you started with too little. In fact, red worms are known to double their population size every 90 days. If you started with far too few, it’s okay to purchase more and add them to the mix. Just sprinkle the extra worms on the top of the bin. They will distribute themselves as they swim away from the surface layer to escape the heat of the sun or grow light.

Vermicomposting is an easy, affordable way to reap major rewards for your garden. The bounty of your vermicomposting bin doesn’t stop at compost and the compost tea. The waste the worms leave behind, which is called worm castings, are excellent to feed your potted plants. Used as a soil amendment, worm castings can bring soil that is lacking in nutrients back to life and get it prepped for a season of incredible growth. Worm castings are full of nitrogen, potassium, phosphorus, and humic acids that help improve soil structure.

After you gather your supplies: a bin, shredded newspaper or leaves, and red wiggler worms, all you need to do is start saving food scraps to feed them. Now that you have the facts you need to get started with vermicomposting and care for your worms, nothing should stand in your way. You can use the vermicomposting method to take advantage of small spaces, making it a great option for apartment composting. Get ready to see major results from the additional nutrition your compost bin will give your garden.

Worm compost cannot have cooked food - Biology

by Jen Fong and Paula Hewitt

    Do I need to add worms to my compost pile?

When most people think of "earthworms", they usually mean "nightcrawlers," which can be 8-10" long and 1/2" in diameter. These nightcrawlers are different from red wigglers, although both may be called "earthworms" since they both are found in the earth.

Almost everyone wants to know the answer to this question. Some species of worms can regenerate, or re-grow, a new tail, if their tail is cut off. However, a worm cut too closely to its' head will have difficulty growing a new tail. Most worms will not regenerate a head.

Generally, we tell students that if you cut a worm in half, you will most likely end up with two dead pieces of worms. However, if you are lucky, the piece with the head may grow a new tail, so you will have one alive worm and one piece of dead worm.

Worm compost makes nutrients available to plants. When compost is mixed with water, it has the ability to hold many positively-charged mineral ions (cations), or nutrients, which can then be taken up by plants. Also, as worms process (digest) the food scraps, the nutrients in the food are changed into forms which can then be used by plants.

How to Compost with Worms

All worms are not created equal. For vermicomposting, you need red wiggler or red earthworms (probably familiar to you if you fish). Your worms have one mission in life: to eat your food scraps and cast (i.e., poop) it into super rich soil. Not a bad life’s purpose. There are other organisms in there too that help break down your garbage. But the worms, and their health, are the number one priority. (See the links below for where to order worms.)

Vermicomposting Worm Bin Setup

Most DIY worm bins are made from large plastic storage bins with lids. (The size should equal about one cubic foot per person in the household.) Long and wide is better than a tall and narrow bin. Use a drill, or a hammer and nail to poke plenty of air holes in the lid top. Some organizations sell ready-made worm bins with large holes drilled in the sides and screens inserted for ample air circulation (but no worm escapees).

Add moistened, shredded paper (uncoated newspaper is ideal), chopped food scraps and worms (about a one pound of worms should be a good amount for most bins) to the bin, and cover it with the bin lid. About once a week, or every other week, move the material in the bin around to help with aeration. Always keep a layer of shredded paper or sawdust over the top of the pile to discourage smells and bugs. Once you stop adding new material the compost should be ready to harvest in one to two months (depending on how much is added in the last feeding).

Care and Feeding of Worms

Worms love to eat and spend most of their time doing so. Just like you and I, worms have culinary likes and dislikes. So what to feed worms and what should you avoid putting in the worm bin?

What to Feed Worms

Of the vermicomposting do’s and don’ts, veggies and fruits are a resounding “DO.” Worms will eat any of the following:

However, it is best to avoid putting citrus, onions, and garlic in the worm bin. Onions and garlic will eventually be broken down by worms, but the odor in the interim may be more than you can handle! Citrus pulp or any highly acidic fruit added to the worm bin in large quantities can kill off your worms, so be aware and only add small amounts or just add the citrus peels without the pulp.

When vermiculture feeding, basically go “green.” Worms will eat almost anything that you would put in a traditional compost bin such as coffee grounds, crushed eggshells, plant waste, and tea leaves. “Green” additions are nitrogen-based, but the worm bin also needs “browns” or carbon-based items such as shredded newspaper, copy paper, egg cartons, and cardboard.

Some “DON’TS” in the feeding of worms are:

  • Do not add salty or oily foods
  • Do not add tomatoes or potatoes
  • Do not add meat or dairy products

Worms will eat tomatoes but make sure to break down the seed or you will likely have some tomato sprouts in the bin. No big deal, however, as you can just pull them out. The same may occur with potatoes and their eyes spouting before the potato is consumed. Meat and dairy are “don’ts,” as they tend to smell quite rancid before they break down completely. Also, they attract pests such as fruit flies.

Don’t feed the worms pet waste or any “hot” manure. “Hot” manure is un-composted animal waste and its addition may result in heating the bin too much for the worms.

How to Feed Composting Worms

Be sure to chop larger pieces of fruit and vegetable into smaller pieces before vermiculture feeding. This aids in the decomposition process.

Depending on the size of your bin, feed the worms from once a week to every two days with about a cup (240 ml.) of food. You may want to keep a journal regarding how quickly your worms consume certain things so you can adjust timings, amounts, and varieties. A stinky worm bin may be an indicator of overfeeding. Rotate the areas of feeding in the bin to ensure all worms are getting fed and tuck the food 3 to 4 inches (8-10 cm.) under the bedding to thwart those pesky flies.

The best indicator of proper feeding is the condition of your worms and their increasing numbers. Proper care and feeding of the worms will reward you with rich soil for your garden, a smaller garbage can, and a hand in reducing the amount of waste in our landfills.

Things you can add to your vermicomposting bin that you might not necessarily think of.

  • Dryer lint – It is made up of mostly fibers from your clothes
  • Egg Shells – although they take a very long time to break down.
  • Paper Towels – as long as you have only used them to clean drink spills, etc. Do not put paper towels that have chemicals on them in your worm bin.
  • Pet Hair – you will want to be careful with this one. In small quantities I have found that it works well but in large quantities pet hair can easily clump together making it harder for the composting worms to break it down.
  • Tea bags and coffee filters – Go ahead and throw them in as well, they are just paper!

How Vermicomposting Works

Now comes the fun part of having a worm bin -- feeding the little guys. You can bury just about anything that originally came out of the ground in the bin. Coffee grounds and filters, tea leaves and bags, fruit and veggie peels and cores, paper, rice, grits, and natural fabrics are all things that can go in the bin. Eggshells that have been washed out and ground up are also an excellent source of calcium for the worms.

The following items make good worm food:

  • Leafy greens
  • Potatoes
  • Non-acidic fruits and vegetables (tomatoes, green peppers)
  • Low-acidity citrus
  • Coffee & tea grounds
  • Rice
  • Grits
  • Paper
  • Cotton
  • Eggshells

There are also several items that will harm the worms. For one, don't feed them anything fatty or oily. Worms can't digest meat proteins or lactose, so no dairy products either, like milk or cheese. While worms do like egg shells, the egg cannot go in the bin. Citrus and salt can actually harm the skin of the worms. We mentioned earlier that worms breathe through their skin, so just imagine if your lungs were on the outside of your body and someone decided to rub salt and lemon on them -- you probably wouldn't appreciate it either.

These items will harm your worms. Never give them:

  • Butter
  • Oil
  • Salad containing salad dressing
  • Eggs
  • Meat
  • Highly acidic fruits and vegetables (lemons, limes, oranges)
  • Hot peppers
  • Salt
  • Animal waste
  • Plastic
  • Synthetic materials
  • Insecticides

Once you've had your worms for a while, you'll get a feel for what they like to eat and what they don't. You'll also know how much to feed them and when. If your bin starts to smell bad, you're either feeding them so much that they can't keep up, or you're not burying the food well enough under the bedding.

Established bins that are healthy begin to reproduce worms and attract other decomposers. If you see other insects crawling around in there, don't be worried. It's OK unless there are a lot of flies hanging around. If you have a lid on your worm bin and bury your food well, you should not have to worry about flies or maggots. These other insects are helping the process, making sure that you can compost even more of your organic waste. After a while, you may also see tiny white sacks that may appear to be maggots. These are actually worm egg sacks -- or possibly even baby worms.

Your worm population should double in size every three months or so. When this happens, you can build new worm bins and transfer some worms over if they get to be too much for one area. If you feel that you can't keep up with the feeding schedule, you have a few different options. Teach your neighbors how to compost and donate some worms to them, set your worms free -- although this is a waste of really good worms -- or go fishing. They make great bait.

We've saved the best for last. Did you know that your worms can provide you with black gold? Read the next page to find out just how valuable it can be.

The Len Foote Hike Inn is a hotel in the North Georgia mountains that has an extensive vermicomposting system in the basement. With the help of the guests, they compost 1,500 pounds (680.4 kilograms) of food and office waste per year, and use the fertilizer in their organic gar­den. When the hotel staff gets bored, they find new (yet safe) things to shred and feed to the worms. One famous story tells of a pair of corduroy pants left by a guest that were never claimed. The staff shredded them up, buried them, and never saw them again. When sifting one day, an employee came across a button and a zipper … the rest had been eaten!

Best Foods to Feed Red Wiggler Composting Worms

It’s easy to make worms happy if you feed your red worms a variety of foods they love.

  • Vegetable scraps: apple cores, peels, carrot tops and wilted lettuce or trimmings. Any vegetable that’s not spicy or really gaseous will make them happy.
  • Non-citrus fruit work best, such as watermelon rind, strawberry tops, old blueberries, etc. Drastically limit citrus or eliminate all together to avoid fruit flies and to keep the bin clean smelling and easy to work with.
  • Used tea. We like to rip up the bags before dropping in but it’s not necessary to break them up.
  • Coffee grounds and filters. Don’t add too much coffee all at once. Mix with other foods. Test your worms’ preferences.
  • Dried leaves. If you want to add more bedding, leaves are awesome!
  • Used napkins and paper towels are ok as long as they are not greasy.
  • Shredded cardboard and paper bags are easy to find and recycle. Shred up the paper bags to make the bedding fluffy. I like to moisten the bedding before adding to the bin. I dip in a big bowl of water or spray.
  • CRUSHED egg shells. We’ve been reading that reproduction increases when worms live among egg shells! It helps add a little grit to the bin. Otherwise, use a small amount of garden dirt that has not been treated with chemicals. A small handful of eggshells or dirt is enough.
  • Citrus peels and fruit – to avoid fruit flies.
  • Starchy foods like pasta, bread and rice – too much for worms to handle with all that bedding already in there.It will take longer for the bin to compost.
  • Onions
  • Spicy peppers
  • Twigs
  • Meat
  • Daily
  • Oily foods
  • Plastic
  • Metal
  • Glass
  • Animal feces


  1. FINICKY EATERS: If after a week you notice a food hasn’t been touched, they may not be too fond of it. When testing a food, position it where you can easy find it later.
  2. EASY TO PLEASE: If they are happy with the food, temperature and moisture level, they will stay put in the bin even with the top off! The more circulation the better. But do not place the bin under a bright light.
  3. SPOIL ‘EM ROTTEN: If you really want to make brats out of your worms, chop up their food. This isn’t necessary but it speeds things up. Your bin may be completed in record time by making it easier for the worms to break down the scraps. We use a food processor, bring the bowl directly into the garage and scoop out the ground food with a rubber spatula. You can also store chopped up food in the frig until ready to feed if you end up with extra.
  4. PUT THAT FOOD TO BED: Because we keep our worms inside our garage, it’s important to us that the bin not call fruit flies, mice or get over-run with ants. Always cover the food with bedding. Folks that dump food on top increase the chance of fruit flies or yukky smells.The best method is to make layers of food and bedding with a big layer of bedding on top.

I made a video that shows you my favorite method for collecting worm compost:

Also take a look at our new guide, “How To Compost with Worms”. It’s in the eBookstore and there may be a coupon code available for a discount. Check it out if you’re interested in a “cheat sheet” that you can use forever to keep you on the right track.

Find out how to mix up homemade nutrients and soil amendments for specific vegetables and fruit! Learn more about manures, sewage sludge and other ingredients you want to stay away from. Don’t use the wrong fertilizer ever again.

We sell it on Amazon and also offer it as a convenient download in .PDF format from this website. Click on the image to learn more about the eBook or add the .PDF version to your shopping cart now. The transaction for the download is handled by PayPal and you’ll receive an email with the download link. EASY!

What types of food stuffs should not be put in the worm bin?

There is a lot of ‘gray area’ when it comes to what can and cannot be added to a vermicomposting system. Really, I would say it depends on your experience level and what exactly you are trying to accomplish. The size and location of your system are also very important considerations.

When just starting out, I highly recommend taking a fairly cautious approach – moderation is the key, and it is better to stick with those materials widely recommended for worm bins.

Fruit and vegetable scraps are always a safe bet – they are pretty well the best kitchen wastes for your bin.

It is ideal to cut them up and let them ‘age’ for a little while before adding them to the bin, but this is certainly not critical for success. Aging allows time for microbial colonization and the start of the decay process.

This can be done in the worm bin itself, but the worms generally won’t start feeding on the materials until they are starting to rot (since the microbial ‘soup’ is what provides much of their nutrition).

It’s also a good idea to mix a little bedding (shredded cardboard, peat moss etc) in the fruit/veg scraps when you add them since they are very water-rich, and the bedding will help soak up some of that excess moisture. Tea bags and coffee grounds are also great additions to your worm bin, but tend to be fairly acidic so you won’t want to go overboard with them.

Starchy materials such as rice, pasta, potatoes, bread etc can be somewhat troublesome for new vermicomposters because they can get moldy quite quickly and if decent amounts are added at once they can also go ‘anaerobic’ (no oxygen) and start fermenting. I can still vividly remember back to a time when I dumped a big clump of cooked rice in my worm bin (my first bin, I might add!).

Not only did it create a stinky mess, but it also resulted in a major population of white worms (which can spring up when conditions become sour in your bin). As part of a school worm composting project I tested rice and other starchy materials, such as donuts, in the bins and ended up killing quite a few worms and again creating a stinky mess yet again.

Don’t get me wrong, starchy materials are totally fine if you know what you are doing – especially if you have a nice big system and spread the materials out. I wouldn’t give a second thought to tossing rice or pasta in my big outdoor worm bin, that’s for sure.

Strongly acidic materials, such as citrus waste and pineapple should be used in moderation as well. Worms are very tolerant of low pH, but you don’t want to quickly throw off the balance of the ecosystem in the bin by adding too much acidic waste. Again, the size and type of system you are using can make a huge difference.

I’ve added a LOT of orange peels and rotten oranges at once to my outdoor bin without any trouble whatsoever. Would I do the same with one of my indoor plastic bins?

Not likely (but will still add moderate amounts of citrus waste).

Aside from the acidity of citrus fruit, the peels contain a potent oil than irritate the worms’ skin. Same is true of hot peppers and onions, so again use a little restraint with these as well.

Oils and oily foods generally should be avoided. They are slow to break down and the oils can coat the worms’ skin making respiration difficult (worms breath through their skin). A little leftover caesar salad or some fried green tomatoes etc won’t generally cause too many issues, but just be a little more cautious.

Meats and dairy shouldn’t be added to a worm bin – processed meats and cheese often contain lots of fat and salt, among other things that can potentially irritate your worms. They also tend to petrify fairly quickly, causing nasty odors and releasing potentially harmful gases. Outdoors in a larger system you could compost these, but they need to be buried well so as not to attract the attention of local scavengers.

Highly resistant or non-biodegradable materials shouldn’t be added to a worm bin because they won’t get processed. Corn cobs, fruit pits, and woody wastes can all be added (worms actually seem to like making a home out of corn cobs), but they will take a LONG time to fully break down.

Anyway, Mike – I think that pretty well covers the basics as far as kitchen wastes go.

Connecting to composting hubs

What if you have nowhere to put your bokashi or worm farm and your council doesn't offer a food scrap collection service?

Raylyn Gonsalvez lives in an inner-city house in Melbourne. Although she does have a tiny backyard it is not suitable for worm farming or composting.

She has looked at a number of ways of disposing her food waste such as signing up to a food waste app to people in the local area who can use the scraps in their compost, worm farm or chicken run taking her waste to put in the worm farm at work and taking it to a community garden compost bin within walking distance of where she lives.

Getty Images: David Freund

The community garden option turned out to be the easiest option for her.

"I found the garden by walking past it and noticed they had a compost bin out the front," Ms Gonsalvez said.

"I contacted them and signed up to the program. Now we collect our scraps in a plastic container and go drop it off whenever we need to."

Some councils run programs that provide residents with free caddies to take food scraps to their local community compost bins.

"People often don't think of going to their local council to ask what's around," Dr Christie said.

"They always know where all the local community gardens are, or where the kindergartens are that might want some compost."