[header] How to store used coffee grounds [title] Put your grounds on a baking sheet lined with newspaper. [step] Keep the grounds no more than 2-3 inches (5.1-7.6 cm) thick. This will help you dry your grounds faster and will reduce the chance of them developing mold [title] Place the baking sheet outside in the sun. 
[step] Try to find a spot that receives sunlight for most of the day. Coffee grounds are often used as a deterrent for neighborhood pests, so you don't need to worry about critters getting into your grounds.