Coffee Knock box Stainless steel - Brewing EdgeDispose of your used coffee grounds quickly and easily within inches of your espresso maker. You can store old coffee grounds for gardening, old coffee grounds can be a rich fertilizer option for your garden beds. Black espresso knock box give you ample storage space for holding the residual coffee grounds so that you can later transfer them to a compost bin. PERFECT SIZE The coffee waste bin is perfect for storing underneath most espresso machines.