Kitchen Maestro Replacement Charcoal Filter Set for Compost Bin Filter keeps kitchen compost bins and pail odorless. Replacement compost filter refills for Kitchen Maestro Compost Bins Charcoal filters help absorb the unwanted odors that compost pails produce. Easy to replace, change every 6 months-depending on use. You can rinse your filters, but do not submerge in water.