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by Kit K Leung
on July 19, 2019 at 9:49 AM
Thanks for posting this. residual caffeine anything to be worried about? That is, does some caffeine remain in the used coffee grounds to be later leached into soils and taken up by plants and potentially the edible parts of the plant - leaves, roots, fruit? Or does the composting process also break down caffeine into less "active" components over time?
by Michele Martinez
on July 19, 2019 at 11:01 AM
Hi, Kit. that's a great question! Our author Pam Snethen used "Gardening Know How" as a reference. I looked there for info on caffeine. They say that if you're composting grounds, the caffeine dissipates, but if you're using grounds directly in the soil, the caffeine can affect things planted in that same soil. First, it can speed the growth, then it can retard plant growth (sounds like "coffee rush" in us!). Apparently the caffeine in coffee plants serves to deter the growth of other plants around the coffee bush by littering the ground with caffeine-rich leaves. Nature is amazing! Here's the reference:
by Diane Barrera
on May 13, 2021 at 8:43 PM
Do instant coffee grounds have the same benefits as regular coffee grounds?
Reply by Michele Martinez
on May 15, 2021 at 8:05 AM
Hi, Diane. I'm a fan of composting coffee grounds, but I've never tried instant coffee. My first guess is that since instant coffee is made from brewed/then dehydrated coffee, it would be much more acidic than the moderate levels in spent coffee grounds (6.5 to 6.8 pH). Also, the plant fiber's been removed (no ground beans), so you would't get the same mulchy "nitrogen boost" in the compost pile. It's a great question. I'll look into it more and let you know what I find.
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