Best Ways to Use Coffee Grounds?

I recently picked up about 10 gallons of used coffee grounds on a trip into the nearest city (from 3 different Starbucks that I happened to be passing). I go into the city at least once a month, and could probably hit a few more Starbucks with some planning. I'm seeing a lot of conflicting info online, about how to use them and possibly drawbacks, however.

I know I have read on here that they are usually pH-neutral, since most of the acidity gets leached by the hot water into the actual coffee. I have also read that even if they are acidic, they become pH-neutral after composting.

I have also read on here that most, if not all, the potential pesticides would have been removed with the hull of the actual coffee bean, and little to none would be present in the actual coffee, much less the grounds. Sites online, however, do say that the coffee that you drink can contain pesticides. But I'm guessing even if so, then a lot less would be left behind in the grounds. And even less (if any) after composting.

I'm thinking I will use these mainly as a source of "greens" to compost with the autumn leaves I plan to start collecting any day now (here in Texas, the autumn leaf season is only just about to start, along with the yearly madness of raking them up into plastic trash bags for the garbage trucks to bring to the landfill).

I also lightly sprinkled some on top of my garden beds, where I recently planted small brassica seedlings (kale, broccoli, cabbage, etc) to grow through the winter. I didn't sprinkle them near the seedlings, more in-between them, for the roots to "grow into" as the plant grows. I only did a light sprinkling, because I've never used grounds before. Then I mulched over them with leaf mold from our bushy-foresty areas on our land.

I also plan use small amounts in my worm bins, along with other food, and balanced with plenty of carbon bedding materials.

I guess I'd really just like to learn more about how to, and how not to use these, since, for whatever reason, I've never collected them before.

So, of course, after posting this, this excellent thread appeared in the sidebar, answering many of my questions https://permies.com/t/45126/Coffee-Grounds. And this one https://permies.com/t/84305/composting/coffee-grounds

Hello, Lila.

I've heard from the Food Soil Web, that the best fertilizer you can possibly make is a living compost that matches the needs for your growies. If you grow herbs, you want a compost that is rich in bacteria, if you grow trees you want it rich in fungi.
By selecting the 'ingredients' in your compost, you encourage bacteria or fungi. They divide compost ingredients into three categories: black, green and brown. Black is manure, grains and fresh coffee beans. Green is anything that looks green and is fresh, plus coffee greens, kitchen scraps, ... Brown is paper, cardboard, dry leaves, wood, ...
So, consider coffee grounds as a 'green' composting ingredient.
If you apply coffee grounds directly, without composting, then it would create a compost that feeds your crops and promotes weeds. As with most fresh fertilizers that compost on site, if you apply too much of it, plants may suffer, so making a compost pile is a safer bet.

The only pesticide I've heard about that is persistent for several years is an herbicide that is employed in hay, and it involves also manure from animals that had been fed with such hay. Most other pesticides are gone by the time you are done with composting. It is unlikely that coffee grounds are contaminated.
If you are uncertain, you could make your compost pile, and then either apply it safely on trees, either try this compost on crops in a small scale to see whether it is contaminated. The herbicide would only affect your herb-alike crops (poaceas).

I've used fairly substantial amounts as top-dressing before with no issues. It's maybe very slightly acidic (soil around here is alkaline in the first place, so that's a plus for me), but unless you're growing in pure coffee grounds, I don't think it will be an issue. It can also be worked into soil in fairly large amounts and improves the tilth substantially.

It may be a "green" in that it's fairly high nitrogen (it is a seed after all), but any water soluble nitrogen is leeched out in brewing, and the remainder is tied up in the semi-charred, woody ground, and it takes longer to break down than you might imagine, I don't think you'd ever be at risk of burning plants from using coffee grounds directly.


All that said, mixed with sawdust and a bit of slaked lime (to raise the pH enough to prevent trich infection and add some calcium), it makes an excellent substrate for growing oyster mushrooms if that's something you think you might be interested in. Oysters have an excellent efficiency (i.e. for 50 lbs of dry sawdust and coffee grounds, you can easily get 50-75 lbs of fresh oyster mushrooms), and the spent substrate (which will be a block of mostly mushroom mycellium at the end) can be fed to worms, composted, or broken up and mixed with mulch to get some secondary fruiting in your garden.

I try to always mix coffee grounds into my compost.  I've never seen compost that has as many worms and little critters as compost that has a fair amount of coffee grounds. I find that my compost is pretty disappointing without them.

Here i use it on the ice on walking paths and outside stairs in winter, good enough alternative to sands.

As cover material for my composting toilet, I get sawdust, coffee grounds, and autumn leaves, in different amounts at different times of year. If I mix coffee grounds into sawdust and then pour some water in and mix it till all is damp, it heats up like crazy in 24 hours. Even more so if I add crumbled leaves into the mix. After a couple or few weeks it has cooled down and so far I don't notice it turning to compost, except that the sawdust is grey instead of fresh yellow. Seems like great stuff to use as cover material.

My composting toilet room is below freezing in winter, so I won't water the mix now, for fear it will freeze solid and be impossible to scoop out for the next 3 months. But I guess even a dry mix of sawdust and coffee grounds will make a good cover material, and in the spring down where I don't know what's going on, it'll improve the composting process. I only started bringing coffee grounds last summer so I don't have practical experience of its effects yet, because there are two composting chambers below and an alternating year system.