From our friends at No Tox Life:

Our 100% biodegradable and compostable Eco-Sponge replaces soft plastic sponges at the sink for dish washing.

How to use for dish washing: Rub Eco-Sponge on your dish block® or pump liquid dish soap on the Eco-Sponge and lather up dishes as usual. It will create a nice bubbly foam just like an ordinary sponge, but without creating micro plastics that wash down the drain.

Longevity: For best longevity, rinse clean and squeeze dry after using, then place it in a dry spot where it can drain. If you leave it damp it will grow bacteria and mold, since it's made from natural plant fiber. We recommend replacing it every 3-4 weeks with a fresh one.

Notes: If you use a heavy amount of animal grease when cooking, you might replace more often, or wash it with soap several times to dislodge stuck grease. You can sanitize the sponge by microwaving the damp sponge for 20 seconds, or dipping in boiling water. 

End of life: Once you're ready to replace your sponge, compost the old one or bury it in the garden. It is completely biodegradable, made of natural plant fiber and doesn't contain any plastics or synthetics. 

Multipurpose: Take one of the sponges and use it exclusively for the body, it makes a great exfoliating body sponge.