Google coffee grounds and you'll find hundreds of blogs and recipes for fabulous ways to reuse this most fabulous by-product of your morning caffeine fix. You'll also find plenty of sellers of coffee grounds, especially of body and cosmetic products - most of which you can make yourself after your morning coffee if you grind your own beans.
The virtues of coffee grounds are a pretty long list, but the high points of their nutrient make-up is that they contain approximately 2 percent nitrogen, 0.06 percent phosphorus, and 0.6 percent potassium by volume. They also contain many micronutrients including calcium, magnesium, boron, copper, iron, and zinc.
Coffee grounds are also slightly acidic - 5.5 to 6.8 pH - enough to be loved up with roses, fruit trees, tomatoes and blueberries, but make lavender, orchids & yucca very unhappy.
Of course coffee grounds are slightly abrasive so they make an excellent scrubbing tool for your body or your pots.
You really can use coffee grounds with wild abandon, and with very little downside. Healthline's 16 ways to use grounds is a pretty good round up of their many uses. The article also provides you the logic, diy tips and recipes. Here's their list:
Anything listed above! Whatever you do, don't toss your valuable grounds - or if you do, toss them onto your garden. If you compost, your pile or your worms will love you for the addition.
If you are a body scrubber, don't buy plastic packets of the very stuff you are already making. Look across at your coffee maker at the permanent access you have to a reliable, fresh cleanser. For the most benefit, it's best to undertake scrubbing activity with a greywater safe soap in your back garden so it doesn't clog your drains, but that's not always practical...
There is so much info online with coffee grinds, and much of the diy info follows the same pattern. This info by Lisa Ogden from UNYO is one of my favs for your garden if you would like another reference.