Spent coffee grounds are a good fertilizer in gardens because of their high nitrogen content. Coffee grounds also contain potassium, phosphorus, and many other trace elements that aid plant development. Many gardeners report that roses love coffee grounds and when furnished with the same become big and colorful. When added to a compost pile, spent coffee grounds compost very rapidly.
Coffee grounds can be obtained inexpensively (usually free) from local coffee shops. Large coffee shop chains may have a policy of composting coffee grounds or giving them away to those who ask.