Vermicomposting a Ton of Coffee Grounds?

Question from Andreas:

I live in an eco-village and we´ve been contacted by a large music festival who would like to give their coffee grounds to us. They say they will have somewhere around a ton. I´m kinda tempted to take it on, but I only have a few small systems – do you think there is any feasible way to handle the grounds with worms?

Hi Andreas,

This takes me back to the times I 1) decided to take all the compost-friendly food waste from a very popular local restaurant, and later, 2) started taking all the coffee grounds produced by a local coffee shop!

Good times…goooood times!!

Joking aside, these were both very valuable learning experiences, and – all in all – they resulted in a lot more “good” than “bad”! But as you might already have guessed, I will definitely recommend that you proceed with caution.

If I am understanding you correctly, this sounds like a single 1 ton quantity. Assuming you have the transportation worked out, this already has a lot of advantages over the regular, ongoing collections I was required to make with the above-mentioned arrangements. I have no doubt that I was collecting a lot more than a ton of waste from the restaurant EACH MONTH. Thankfully there wasn’t nearly as much from the coffee shop – and the grounds were a lot easier to deal with (another uhhh “perk” for you – lol), but it definitely DID add up over time.

My recommendation, assuming you have some outdoor space to work with at your eco-village, would be to start with some sort of hot composting phase. If you can get your hands on some really well-aged horse manure, I would mix that – plus a LOT of bedding (something like straw might be the most realistic option) – with the grounds, and create a windrow out of it. Cover it with more of the aged manure and a thick layer of straw, then let it cook for at least a couple of weeks.

Once temps drop down to a worm-friendly level (below 90 F), you can introduce some worms (ideally, along with safe habitat material from an existing vermicomposting system and/or some of that nice aged manure) on the edge of the windrow. Monitor their activity to see if they start to move into the windrow. Once they start spreading out in the bed, you are probably ok to add more of them (although I still recommend stocking them in the same manner as I just described).

If you DON’T have any options for working with this material in an outdoor location (or you don’t have access to any additional materials such as bedding or aged manure), you might be best to let the opportunity pass.

Just my 2 cents worth! Hope this helps.

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    • tom
    • April 10, 2015

    Last june I stated pick up about 35 lb. of coffee grounds a day. In november I started on a new pile in straw bales started the next one april fools day the november one was full. At 3 bales high 2 1/2 bales wide it is about 140 f.

    • chris
    • February 28, 2018

    140 f will kill any weed seeds in your compost. The caffeine will kill any slugs.
    You have the perfect compost??

    What is the question!

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