Biochar as a tool for Sanitation

The humble toilet. For the past 200 years, it has helped the Western world to safely collect and manage human waste. Unfortunately, because traditional sanitation systems are expensive to build and maintain, they are far less prevalent in the developing world. For over a billion people around the world, a clean toilet is a luxury they will never experience.

Far more prevalent is the pit latrine, pictured above. A pit latrine is, as its name implies, simply a hole in the ground. While pit latrines are relatively cheap to install and maintain, they can have very expensive consequences on human life. Pit toilets rapidly become infested with flies, produce pungent odors and have the potential to leak into water supplies spreading diarrhea and cholera.

Last year, the Bill and Melinda Gates Foundation announced a $42 Million initiative to ‘reinvent the toilet.’ The goal is to develop new technologies for sanitation in the developing world that cleanly convert waste into fertilizer and/or energy and cost <$.05/user/day. re:char was selected by the Gates Foundation as a grantee to investigate and develop a sanitation system based around biochar and pyrolysis.

We recognized that for any appropriate technology to be successful, it must meet the following criteria:

  • Locally prototyped, tested and produced
  • Ultra low-cost
  • Made with locally-available or recycled materials
  • Aspirational (ie sexy)
  • Fits within existing behavioral and cultural norms

We designed and deployed a prototype feces collection chamber that fits within existing pit latrines. This chamber can serve an entire family, while reducing odors and flies. The chamber cleanly captures the waste until it is ready for conversion to biochar.

Users then insert the collection chamber into the chimney of our Climate Kiln biochar system and produce a batch of biochar. The heat from the pyrolysis is transferred to the feces collection chamber, completely sanitizing and pyrolyzing the waste. The end product is inert, carbon-negative and ideal for use as an agricultural amendment. What’s more, the entire system (kiln & waste collection system) can be produced in our shop in a box for <$80.

Over the next few months, we’ll be working to refine the technology and field test it. In August, we will present our work to Bill Gates and other members of the foundation in Seattle at the ‘Reinvent the Toilet Fair.’ We will actually be bringing a shop in a box production facility to Seattle to demonstrate! We hope that biochar can become another tool in the sanitation arsenal.

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