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So why exactly do worms love coffee grounds so much?

August 20, 2008

Maybe they are addicted to caffeine?

Comments (26)

  • leearnold

    I think it has to do with several things. First is the caffeine. Secondly, coffee grounds have lots of surface area which allows bacteria to grow (and as you know, THAT is what they eat). Thirdly, I believe it adds to the gritty substance in their "guts" that they use to grind their food, since they have no teeth.

  • Jasdip

    I don't think mine are all that thrilled with it. I sprinkle it on top of the bedding, and they don't loll around in it. It mixes in with the vermicompost, so it's hard to tell whether they eat it or not. But it saves throwing it out.

  • stevesd

    Its a fairly good source of nitrogen,hence protein when mixed with more carbon sources such as your paper bedding, so if it is kept moist the microorganisms in the bedding will certainly thrive on it. I've mentioned before, I think, that my worms sometimes go for feeding after feeding with little else but coffee grounds and mine are thriving, reproducing, and catching fish too:) Steve

  • squeeze

    I don't think they like coffee much at all .... certainly not for the nitrogen, as there's actually very little available N in coffee ..... and the grounds don't hold water, so are actually quite slow to decompose on their own, they're more like humus ..... the only time I've found worms dealing with grounds is when I mixed them with carrot pulp from a juicing operation, a fine, water holding material higher in available N and sugers


    Here is a link that might be useful: about coffee grounds

  • vermiman

    My worms seem to love it when I add a coffee ground and tea bag mixture.

  • stevesd

    Hey Bill, I looked at that link and it seems that the total nitrogen in coffee grounds is as high or higher than most manure. The availability of it will be taken care of by the microbes in the bin. As you have said, compost happens. My worms thrive on coffee grounds. Your worms, well Bill, You feed them too good!:) they are spoiled. Happy worming. Steve

  • hydroponica

    I don't think there's very much caffeine in used grounds, but there's bound to be a little.

    I give my worms coffee grounds pretty regularly and they do love it.

  • amonkiki4_gmail_com

    soooooo do they like it or not!!!!

  • susanfromhawaii

    1. I doubt caffeine affects worms the way it affects mammals.
    2. Worms like any food. So yes, they like used coffee grounds.

    The thing to be careful of is that if you put in a lot at once, it will heat up, which can kill the worms. It's wise to either pre-compost it or make sure it's in a small part of the bin so the worms have somewhere to escape to if needed.

  • jolj

    I wish I knew for sure.
    I have about 20,000 lbs of coffee waste,give or take a 1,000lbs. & hope to put red worms in it when it warms up.
    So I would love to know for sure, now.
    Thing is, I can tell you by July or August for sure.
    Now if I can figure out a way to keep the Fire ants out of the red worms, I could have casting for my asparagus beds.
    I hope to put in 500 crowns this fall, but that is another thread.

  • GracieLives (WI 4a)

    Hey, Jolj, I'd like to know how your coffee grounds and worms are doing. Before I came across this Garden Web thread, I read a bit about a red worm composting site:

    They were using LOTS of coffee grounds, too. Maybe not as much as what you have but on a smaller scale w/same type of intent.

  • amcook

    Mine do like coffee grounds but with one caveat.. It has to be pre-rotted. A couple of years ago, I started making my own coffee at home instead of going to the local coffee shop. Well, I started putting the coffee grounds straight into the worm bin and they didn't seem to take to it. I realized that they tended to dry out before bacteria can form and start to break it down. Then I started to combine it with other "wet" foods and that helped but it took about a week before the worms would attack it.

    I recently started a new bin and decided to use a pre-rot container and not only do the worms attack the food almost immediately, I had almost zero worm escapes post introduction. I put pre-rotted food (about 70-80% coffee grounds) into the new bin and then transferred about two pounds of worms in. I was expecting the typical worm chase that night but to my surprise, I only found three worms at the bottom of the bin in the morning.. all of which were still alive and transferred easily back into the bin. I then looked at the area where the food was and it was filled with worms. I immediately put another scoop of pre-rotted grounds into another corner and within about 4 hours, that area was also filled with worms.

    My theory is that since bacteria feeds on sugar, just coffee by itself doesn't attract sufficient amount of bacteria and without bacteria, worms won't eat it. The pre-rot process helps introduces a large shot of bacteria into the grounds that helps to break it down and make it more attractive to the worms. Try combining coffee grounds with a little high sugar food like banana, strawberries, carrots, etc. and leaving it for a week or so before introducing it.

    Good luck.

  • Karchita

    Mine like it a lot. I don't know why. I only give them the wet grounds from the coffee I make at home with a drip brewer and I suppose it is a bit "pre-rotted" from sitting in the canister on my kitchen counter before it goes out to the bin. My worms get a steady diet of coffee grounds and banana peels all year round and then a variety of seasonal vegetable trimmings (lettuce, potato and carrot peels, melon rinds, etc.).

    I don't feed them the super dry grounds that I get from Starbucks. I tried it once long ago and they didn't seem to like it, probably because it is too dry.

  • Celbrise

    my worms seem to love it as long as it is wet. i often make coffee at home and right after i let it cool down and dump it in still moist. i don't put a lot of it in maybe a table spoon or 2 per day since i use kcups. the coffee itself will decompose on it's own. had it do this once when saving the grounds.

    idk why they love it i would assume it's like sand + some bacteria on it. other then that idk. i never had any problems with it though i use all different types of coffee and it's the same process

  • GreenIvy

    Mine don't seem to like it. I've only put it in one corner of the bin and that corner's pretty empty of worms.

    Maybe they don't like Starbucks? :)

  • hummersteve

    After this thread thought I would run a test. I took my coffee ground still in very wet paper filter and put it in one corner of my factory 360. I will see what happens in a couple of days. Most of the food that goes into my bin is fruit peeling , , bananas , potato, and run thru my juicer and saved till needed.

  • 11otis

    Mine don't care much for UCG and it caused increased mite population so I don't use it in the worm bins.

  • theparsley

    I don't think it's correct to say that worms "love" used coffee grounds, at least not in the way they react to melon rinds or corn meal, by visibly flocking to them while wiggling happily. I think coffee grounds just have a much longer lead time before they become worm-edible, possibly because it takes a fungal process to break down the cellulose component of the beans.

    I used to put my used coffee grounds in the bin still in their paper cone filter, but I found this creates a long-lasting clump of grounds that tends to dry out and become impervious to rewetting, and takes an extraordinarily long time to start breaking down on its own. The other drawback to solid masses of grounds is that they will heat up, which you can really notice if you dig around in the bin with your bare hands. Now I dump the grounds out of the filter and mix them together with the other food scraps.

  • 11otis

    Another reason UCG doesn't land in my worm bin, it has the colour of VC and very easy to confuse with finished VC. So for my own peace of mind of having a high % of castings, I leave it out. No idea how long it would take to break down anyway. For the same reason I do not use peat moss. I put some spagnum moss a few years ago and they are still there, very recognizable.

  • theparsley

    Oh, I'm sure the grounds do compost down with everything else in roughly the same time frame. Just the slightly longer time frame of tougher scraps versus the quick feeding frenzy of melon. I don't see unprocessed coffee grounds in my finished VC. Even if not every single granule of coffee ground actually passed through a worm, it's been in the system with all the other decomposer critters and micro-critters quite long enough to be composted.

    I produce a regular volume of coffee grounds in relation to my other scraps, since I consistently make the same amount of coffee every day regardless of whether or not I'm too sick that day to cook. I'd hate to put all that coffee in the landfill when I don't have to, especially when it offers so much compostable nutrition.

  • hummersteve

    I cant verify that worms particularly like coffee grounds as is, but I do add a few into the original bedding mix , no problem.

  • jolj

    First post was 2011, I am still fighting with the FIRE ants, but I know that after the heat is gone from the coffee waste that the red worms leave & the night crawlers move in.

    When you have pure ground coffee that has never had water poured on it, the worms seem to like it as well as the used grounds. The chaff seems to rot quicker then ground coffee or whole beans.

  • harry757

    Do the worms enjoy the coffee chaff? I know someone who has a coffee roasting company close by so chaff might be easy for me to get.

  • jolj

    I compost the chaff out side, the worms are wild & seem to do well in it.

  • harry757

    Am I correct in assuming the chaff in outside compost is a "brown"? Have you tried it in a hot pile?


  • gorbelly

    My worms don't like coffee grounds much. I mean, they'll eventually get around to them. But they definitely prioritize other foods I throw in the bin. I've found clumps of coffee grounds weeks later uneaten in the compost while harvesting (the grounds sink down into it as the worms work the stuff under the surface).

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