Authority-questioning blog Truth is Treason notes that human beings have used wood ashes as a source of lye to make soap for centuries. Commercial lye is very caustic and, as any viewer of Fight Club will note, causes chemical burns. The small amount of lye you extract from a few cups of wood ashes will not harm you but it can leave your hands dry if you forget to wash them after the dishes are cleaned.
Pick your greasiest pot and add a few cups of wood ash to that pot. Add enough hot water to make a paste; the hot water will create potassium salts from the wood ash that will mix with the fats in the pot to make a rudimentary soap. When the paste is cool to the touch smear it over your dirty cookware and dishes and allow it to dry for several minutes. Finally scrub and rinse your dishes. Make sure you use purified water to clean the dishes; they'll be touching food again and you don't want any disease-causing organisms to come into contact.
While there are many types of biodegradable soaps that work well for camping such as Dr. Bronners and Campsuds, it's worth knowing how to make your own if you forget to pack soap or if you run out. Photo by Rick Bradley.
How to: Clean Your Cooking Gear and Make Soap from Wood Ash [Truth is Treason]