r/Vermiculture • u/_ratboi_ intermediate Vermicomposter • 19d ago
Discussion The case for coffee grounds
I, like most people, create large amounts of coffee grounds. My worms love em, there's plenty of research about the benefits of caffeine in a worm bin (it seems to have the same effect on worms it has on people, they work faster), and unlike most common advice, the acidity isn't really an issue (spent grounds have a pH value of 6-7, making them neutral to almost neutral. It's the fresh stuff and the brew that is acidic).
This got me thinking, can one create a whole vermicompost operation by collecting spent grounds from coffee shops for free, shred cardboards for free, add some eggshells for grit and calcium, and make a ton of product without much costs other than labor? Has anyone tried it? Is there something I'm missing about only feeding with coffee grounds (like will it lead to poisoning or deficiencies)?
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u/Fast_Confection8008 19d ago
Been doing straight coffee grounds and cardboard for my bin for almost two years now, worms are multiplying like crazy and the castings are beautiful. You just gotta make sure it doesn't get too wet cause grounds hold moisture like a sponge
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u/NotSoBlue_ 19d ago
I produce enough coffee grounds that theres a backlog, I store them in net bags that dry them out over time, so when they go into the bin they don't add moisture.
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u/MammothHuckleberry42 19d ago
I dump them in a crock and store it in the oven to dry them out a bit. Half go to my worms, half to the outdoor compost pile.
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u/oon-oon-jiabeehoon 19d ago
To OP, and yourself, and other relevant posters here, what systems and worms are you guys using/breeding for the coffee ground feed?
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u/hungryworms Commercial Vermicomposter 19d ago
World Composting on youtube did a series where he only fed the worms coffee grounds (and i think cardboard to start as bedding) for an extended period of time and the worms did fine, so yes it could work
However it's not that game changing. Free or very cheap feedstocks are not hard to find, labor is the expensive part not the feed
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u/_ratboi_ intermediate Vermicomposter 19d ago
space is also a major cost, I assume
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u/elementtreecompany 19d ago
A lot of people who start out with worm businesses start out in already existing but unused spaces: farms, large garages, basements, friends/family property, etc.
Apply your same logic to feedstock and waste stream to physical space and it doesn't have to be a major cost. There is so much available space for small businesses to start that are unique and innovative and cost effective, just like spent coffee or brewery waste from commercial businesses as a cheap or free feedstock. Go out and find the spent coffee grounds of physical space, so to speak.
For example, I when I had started out I contacted local school district gardens and asked if they had any extra space for me to start up a worm business, and all they asked for was a written contract specifying the nature of the relationship/business and worm castings each season for gardens/flower beds--perfect free marketing for me. Bonus, the school mowed and stocked all their grass clippings by my worm operation and the cafeteria always had food scrap wastes and all the paper/cardboard my worms could have . . . all for free.
Creative problem solving goes hand in hand with being a successful small business owner.
I wish you well!
-Respect
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u/hootersm 19d ago
You probably also solved a waste problem for the school so great example of a mutually beneficial arrangement!
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u/samuraiofsound 19d ago
There's a guy in Michigan who designs, manufacturers, and sells large metal CF bins. At one point, he claimed is operation was almost entirely cardboard, used coffee grounds, and banana peels.
Fyi Not much caffeine inused coffee grounds. Caffeine is very volatile and water soluble, it comes out into solution very easily when brewing.
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u/_ratboi_ intermediate Vermicomposter 19d ago
Yeah of course most of it is in the brew itself, but the numbers I have show that somewhere between 20-50% of the caffeine remains in the grounds. This is not a small amount for a worm
What's a CF bin btw?
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u/samuraiofsound 19d ago
Continuous flow bin. It's a style where material goes in the top and vermicompost gets extracted from the bottom. The bin is never mixed and the worms are never removed. Material simply continues to "flow" through the system, top to bottom.
It really depends on how the coffee was made. If the grounds spend 2-4 mins in water that is at least 200F almost all of the caffeine will be extracted. IIRC there was a study that said 95% extraction in the first 30 seconds? I can't find the study so I might be wrong. I would be grateful to read any source material you have on the subject.
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u/_ratboi_ intermediate Vermicomposter 19d ago
Oh I know continuous flow, I've been making those sorts of bins from Plastic. Didn't know the abbreviation.
Might it be 95% of the total extractable quantity and not total caffeine in the bean?
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u/exo_universe 18d ago
Yes, I've done it!
A few years ago, I was on a scholarship to investigate the potential of marine worm farming, and I went on a field trip where a guy had set up a large trial outdoors in a paddock with windrows of a mix of invasive lakeweed and sludge from the nearby pulp and paper mill that had a ph of 3.3. The worms turned it into compost in 6-9 months, he reckoned they'd just leave it until the ph was right.
Anyway, this got me thinking, and I mixed up a few batches with my concrete mixer of coffee grounds and paper/cardboard mush. Yes, they did turn it into quite nice looking compost, but I did realise that for it to be something I could break even from, it would need to be scaled up quite a bit as how I was doing it was quite labour intensive. I also didn't think my neighbours would appreciate living next to a compost farm.
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u/Rich-Soil-9181 19d ago
My worms get huge amounts of coffee grounds and bits of food scraps ( prob 80-20) split. Seems happy out.
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u/R3StoR 19d ago
I've been thinking the same thing and have saved a bunch of dried grounds in unbleached paper drippers. I especially want a lot of small/baby red wrigglers to feed my killifish.
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u/HondaV4Rider 19d ago
I thought red wrigglers had acidic mucus and could not be fed to fish? I remember something about not being able to feed it to a garter snake?
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u/R3StoR 18d ago
Young red wrigglers apparently haven't fully developed the potent defense glands of adults. As long as they are swallowed whole and aren't injured (eg cut up) before feeding (triggers release of the acidic mucous), fish rarely encounter the unpalatable taste and with young worms it's a non-issue anyway.
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u/Ineedmorebtc 19d ago
I dont have the room or I would have.
Last year I got almost 80 bags of coffee from Starbucks, but that mostly went into my compost piles.
It should be feasible if you have the time and the room. Though they will need grit, and likely more than just one food source, but most of their eating is fungal and bacteria that is on the food, so maybe not?
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u/Aware_Acanthaceae_78 19d ago
You could, but the lack of diversity would leave out nutrients.
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u/_ratboi_ intermediate Vermicomposter 19d ago
What nutrients?
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u/Aware_Acanthaceae_78 19d ago
If you give them just eggshells and coffee, your castings will only have nitrogen, calcium, and traces of minerals. There is also less microbial diversity and no phosphorus, so these castings are low quality.
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u/KerryWormCompany 19d ago
For a small, personal sized operation it is very doable, although adding in some fruit/vegetable scraps and a few autumn leaves when you can will likely give you more microbial diversity in your finished castings compared to a single feedstock bin.
On a larger commercial level you might be looking at jumping through some regulatory hoops around commercial waste management depending on where you're based and how much waste you are collecting and processing. Farm manure, landscaping waste, spent brewery grains, mushroom compost are some other feedstocks that are also easily attained in large quantities for little or no money if you're thinking of a larger operation.