The popularity of composting toilets is increasing because of the low water usage, simplicity of construction (sometimes with only three buckets and one lid) and useful byproducts. But their spread is limited to rural and suburban homes because of the need to lug the manure-filled buckets to a compost pile.
This system, using a mechanism partially based on a carousel spice rack, aims to reduce the amount of manual labour required to use composting toilets in a multi-story building. To power the mechanism with the minimum of electricity, it uses the fact that a manure-filled bucket is heavier than a sawdust-filled one. This is not as convenient as water closets but it is a step in the right direction.