"Foam-Flush" toilets look and function much like conventional toilets. Using a mixture of biocompatible soap and water, the foam-flush toilet moves waste through a conventional 4" pipe to the composting tank below. The foam mixture cleans the toilet bowl with every flush but uses only about 3 oz. of water, making it fully compatible with the composting process. Since the foam flush is using water to carry the waste, it is possible to have it offset from the compost system at up to 45 degrees, making the design much like it would be for a conventional toilet system. Clivus Multrum makes foam-flush toilets.