I used my already brewed espresso grinds to pH down. What would happen?

Hi there

We make minimum 2-4 espresso per day in our house between me and the wife. I heard coffee is acidic so just for fun I stuck my pH pen in a litre of water and added already brewed leftover grinds to bring the water from 8.1 to 6.5. It worked, quite well!

Then I ran the concoction through a chemex filter to remove all of the actual solids

And I am left with a brown transparent liquid with a pH of 6.5

What would happen if I dumped it on a plant in veg? Or used it as a starter liquid to a quick castings tea for example?

I’m assuming it has some nitrogen but doubt it would be enough to be instant toxic. Or would I be wrong?

I didn’t feed anything lol but I have too many plants in veg right now, maybe I should sacrifice one as a test dummy

And as a reminder, this is already brewed leftovers that would otherwise be thrown out so I am keen to know if there’s anything I can do with it (I don’t compost sadly, no room at the moment)


In the name of science do it!!!


That’s the kind of enthusiasm I’m looking for!! :sweat_smile:


Just be careful coffee grounds are loaded with nitrogen


You can actually get used coffee grounds from some Starbucks just for your garden!

1 Like

@frozen Very nice machine for espresso. It’s on my list. :drooling_face: Man, now I could go for some shots… :coffee:

Coffee should be composted first then added, but when using as a ph adjuster that works fine. Check your run off if you decide to use it, it may cause a rise in PH over time.


I have no way to compost it first sadly… I am thinking of researching how to do Bokashi since it’s something I can do in my limited space indoors… I wish I could make worm castings but we just don’t have a suitable space for it that won’t freeze come wintertime :frowning:

I appreciate the kind words though, and always love to meet another espresso fan !!! Thank you!

I’ll report back with any meaningful developments :smiley:


Believe it or not, all you need space wise is room for a 5 gallon bucket and stack them. You can do 250 red wigglers in a 5 gal just fine. Used coffee grinds is like crack to them. I give my guys some once a week or so… look on you tube for 5 gallon bucket worm farm setups. Its slow going at first and you wont get a return for at least 3 to 4 months but after you get established you can get enough a month to feed your girls every few weeks. They dont stink at all unless you overfeed or feed the wrong thing. Mine stay stoned all the time from them munching on defol. I even throw em some bud pieces when i harvest.

1 Like