Composting with Coffee Grounds

May 22, 2021

I would like to start collecting coffee grounds from coffee show such as Starbucks again now that covid is mostly behind us, but they are not offering them any longer. I looked online to see if I could find any information and I only found these disappointing compost miss information blogs.

Rural Sprout Blog

5 Reasons You Should NEVER Use Coffee Grounds In Your Garden

Tracey Besemer Published: Sep 16, 2019 by Tracey Besemer

This Machiavellian piece of writing takes half truths and twists them. Coffee grounds are not good to add to your garden. They need to be composted first. Earthworm deaths in coffee composting is also found on misguided Youtube Videos . The so called research had to do with red worms vs. earthworms. Redworms the live in unfinished compost. Earthworms live in the soil. They took earthworms and placed them in a bin with full of coffee grounds. Naturally, they died because that was the wrong environment for them. But even redworms can not live in straight coffee grounds. So no matter which worms the end result of the coffee experiment would be all the worms would die. If you want to compost large amounts of coffee you can do that in a compost bin has a bottom, but if you don’t add brown or carbon material in the ratio of 50 percent, you will only get a disgusting mess. If you are composting with a bottomless bin you can add coffee grounds, but no more than 50 percent of the contents should be coffee. The other 50 percent should be browns or carbon based materials like dried leaves, dried grass or ground up wood. There was no way for me to leave a comment on their pathetic blog of half truths. It’s very easy to take one point you want to make such as coffee grounds are bad and find evidence to support it.

Are coffee grounds full of acid or not?

These two blogs contradict each other.

Rural Sprout vs Discovery from Read the blogs on Archive Today in case they are deleted from their original source. May 22, 2021 finds the blogs up and online.

While the used grounds do have some acid left after water is poured through them, once they are composted they are fine. The Discovery Network claims large amounts of caffeine kill plants, but once the coffee grounds are composted they no longer have any caffeine. The book called “Caffeine: How Caffeine Created the Modern World” by Michael Pollan explains that caffeine is a natural substance that causes people and animals to crave it. The animals and people help the plants spread and reproduce by carrying the seeds and cultivating the plants. If you want to add leftover brewed coffee to your plants it is ok, but not on sensitive and tender seedlings. If you add a cup of brewed cool coffee to the roots of a blueberry bush it will be beneficial. Blueberries like acid soil. It’s true the acid does wash away over time, but if you soil is already full of health organic compost that will not matter. Please see this Wikipedia page on Coffee Grounds. I have not worked on the page, but I found it be all correct and in order.

Updated for National Composting Day May 29, 2021
I found a new article about Composting with Coffee. This article is better, but it still has some misinformation. Don’t use Coffee grounds as a mulch. I know people find mulch too expensive and they want free mulch to the point in which they go and raid parks for mulch. But free coffee grounds will not work as mulch. Anyone who ever tried this will know that coffee grounds attract files. As coffee grounds sit on the ground they also begin to grow mold which is white in color. After a while you will end up scooping up all your coffee ground mulch and removing it because it does not work as mulch. Use wood products or compost for mulch. Compost your coffee grounds along with browns. Remember coffee grounds are really “greens” that is they are nitrogen based and “browns” are carbon based such as wood or paper. Dry grass is a brown but green grass is a green. Things that are alive and green are “greens” such as old salad greens, but things that are dead and brown like ground up wood tend to be carbon.

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