The GCH4

LOCATION: New York City, USA

SUMMARY: The GCH4 is a toilet with a waterless, mechanical system for packaging and transport. It creates an urban infrastructure in which human waste becomes energy and fertilizer.

The toilet uses a biodegradable lining material to transfer and contain excrement inside an odorless, sealed cartridge, which the user periodically wheels to an outdoor biodigester in exchange for methane gas. An experiment in collaboration with chemical engineers at Imperial College London showed that the lining, which is made from carbon-rich organic material, doubles the methane output of human waste. The lining also serves the crucial purpose of freeing the user and the toilet from fecal contamination. The biodigester creates liquid fertilizer as a secondary byproduct to be emptied once a week.

Using low-tech means to turn human waste into high-value commodities, the GCH4 creates an economic cycle in which waste treatment pays for itself. Just as mobile phones have rendered landlines obsolete, this infrastructure could substitute plumbing.

PROBLEM SPACE: Problem: Most dry toilets today are built on the Eco-San model, which involves urine diversion and composting, and is not practical for dense urban environments.
Problem: The big challenge facing waterless systems is transport of fecal matter, because feces sticks to everything, even, as microbiologists have told me, nanosurfaces. Problem: Communities formerly deprived of toilets don’t properly maintain newly installed dry toilets. Problem: Biodigesters that harvest human waste generally don’t produce enough methane, because the Carbon to Nitrogen ratio of human waste is too low.

SOLUTION:
Solution: The GCH4 offers all the ease of a flush toilet, and requires no fixed installation. It can go anywhere.
Solution: The GCH4 creates a transport infrastructure based on motivation. People will carry the cartridge a short distance when the process is clean and the reward is high-valued fuel.
Solution: A user-friendly design provides cooking fuel, which is locally, immediately useful. This creates ample incentive for people to maintain their toilet systems.
Solution: The biodegradable lining, made from carbon rich materials, doubles methane production. A refillable commodity made from renewable resources, the lining helps to create a sustainable business model.

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