Solar-powered waterless toilet to be unveiled in India

A revolutionary toilet that doesn’t require any water and is fuelled by the sun is set to be unveiled in India this month. Designed and built using a $777,000 (£467,299) […]

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By Priyanka Shrestha

A revolutionary toilet that doesn’t require any water and is fuelled by the sun is set to be unveiled in India this month.

Designed and built using a $777,000 (£467,299) grant from the Bill & Melinda Gates Foundation, the waterless toilet uses innovative technology that heats human waste to a high enough temperature to sterilise it and create biochar, a highly porous charcoal.

It is being developed by the University of Colorado Boulder to help some of the 2.5 billion people around the world lacking safe and sustainable sanitation.

Karl Linden, Professor of Environmental Engineering said the biochar “has a one-two punch in that it can be used to both increase crop yields and sequester carbon dioxide, a greenhouse gas”.

He added: “Biochar is a valuable material. It has good water holding capacity and it can be used in agricultural areas to hold in nutrients and bring more stability to the soils.

“A soil mixture containing 10% biochar can hold up to 50% more water and increase the availability of plant nutrients. Additionally, the biochar can be burned as charcoal and provides energy comparable to that of commercial charcoal.”

The invention consists of eight parabolic mirrors that focus sunlight to a spot no larger than a postage stamp on a glass rod connected to fibre-optic cables.

“Tests have shown that each of the eight fibre-optic cables can produce between 80 and 90 watts of energy, meaning the whole system can deliver up to 700 watts of energy into the reaction chamber”, Mr Linden said.

His team is one of 16 around the world funded by the Gates “Reinvent the Toilet Challenge” since 2011 – an effort to develop a next-generation toilet that can be used to disinfect liquid and solid waste while generating useful end products.

All have shipped their inventions to Delhi, where they will be on display on March 20-22 for scientists, engineers and dignitaries.