yes, you can compost used coffee grounds. let them cool, mix them with other compost materials and keep them a small part of the pile. i would compost them before putting them around plants.
coffee grounds are useful after brewing, but a pile made mostly from coffee needs a different mix. the same goes for a flowerpot with fresh grounds dumped on top. start with the compost you already have and add the grounds as one ingredient.
are coffee grounds green or brown compost?
used coffee grounds count as a green compost material. that category refers to their nitrogen content, not their color.
dry leaves and suitable paper are brown materials. a home compost pile needs a mix. adding grounds to a pile full of kitchen scraps still adds another green material, even though everything looks brown in the bin.
washington state university extension recommends keeping coffee grounds to no more than 20 percent of the pile by volume. use that as an upper limit, not a target you need to reach. a little coffee alongside a range of other materials is enough.
how to add coffee grounds to compost
let the grounds cool after brewing. empty them into the pile and break up the compacted puck or clump. mix them through other materials instead of leaving a thick coffee layer on top.
add brown material as needed for your compost system. dry leaves are one option. follow the compost bin's instructions for moisture and turning. keep using a range of accepted ingredients rather than collecting more coffee than the pile can handle.
if you use a collection service instead of a home pile, check its accepted-materials list. follow that service's rules for filters and liners too. a bag used to carry the grounds needs its own check.
can you put coffee grounds directly on plants?
i would take the compost-first route. uncomposted grounds can suppress plant growth, and thick layers can compact enough to interfere with air and water movement in soil.
keep them out of seed-starting trays. washington state university's review reports reduced germination and growth in experiments using grounds. a seedling tray is a poor place to test a coffee disposal habit.
when compost is fully broken down, it should look soil-like and smell earthy. use the finished compost according to the needs of your garden. the plant and soil still decide what to add. a soil test can help with that decision.
do coffee grounds make soil acidic?
the acidity of decomposing coffee grounds varies. drinking an acidic-tasting coffee does not give you a reliable soil treatment.
if a plant needs a particular soil ph, test the soil and follow local gardening advice. adding yesterday's grounds is too rough a way to make that adjustment.
can coffee grounds go in a worm bin?
a worm bin needs separate guidance. washington state university advises avoiding coffee grounds in confined vermicomposting bins because they can harm the worms. i would leave the grounds out rather than transfer ordinary compost-pile advice to that setup.
for a regular home compost pile, keep the process simple: cool the grounds, spread them through a varied mix and let the compost finish before using it. the coffee has done its brewing job. now it can be a small part of the next one.
for your next brew, you can find coffee at couplet.