When I get grounds from Starbucks they include the filters - do I have to dispose of these or can they be mixed in? Thanks
Despite the wonders of coffee grounds touted on the internet, the scientific evidence is that coffee grounds (and filters) are fine for the compost pile. That's it. They do not stop slugs or acidify the soil. To begin with, the acid value of coffee BEANS varies quite a bit depending on where they are grown. More importantly, most of the acid leaches into the coffee liquid when beans are brewed. If you need to acidify your soil, seek a source such as sulphur that has a known amount of acidity so you can dose your soil correctly. Start with a pH test so you know how much to add. This article goes over some of your options.