Waste’s the way to power the world, say young SA boffins


Waste’s the way to power the world, say young SA boffins

For example, in a rural school, manure can be used to charge battery backpacks for children to bring home

Senior science reporter

Imagine turning garbage or landfill gases into electricity so people don’t have to rely on Eskom. Or capturing the mining industry’s methane byproduct and turning it into energy. Or turning food waste into reusable water and fuel for transportation.
Most of us wouldn’t know where to start. For postgraduate students at SA universities, however, these are real projects, and they were on show at the recent Africa Utility Week in Cape Town.
Finalists from Wits University, the University of Cape Town, and Stellenbosch University put together proposals for the Initiate! Impact Challenge, which focuses on the energy sector. Team members included chemical engineers, environmental scientists and energy planners.
The UCT students unveiled their “energy box”, which turns organic waste into electricity.
“Across Southern Africa, there are over 700 waste digesters which turn organic waste … into a mixture of carbon dioxide and methane gas called biogas,” said team members Chelsea Tucker and Carol Ngwenya.
“Many of these digesters can be found in rural areas and off-grid communities But only 10% are being used to their full potential. The energy box can be retrofitted onto a waste digester to convert this biogas into electricity for the community.”
The device is up to 30% more efficient than conventional systems, and its developers say that in a metropolis like Johannesburg it could be attached to municipal waste digesters that process thousands of tons of organic household waste annually.
In rural areas, using existing digester infrastructure, the system could bring electricity to off-grid communities via battery banks.
“An example is in a rural school, where manure can be used to charge battery backpacks for children to bring home,” said Tucker and Ngwenya.
The Wits University team also focused on reducing the dependence on grid electricity by looking at ways of using methane from landfills and coal mines to generate electricity, heat or biogas.
“The type of technology we proposed is existing but under-exploited within the African context,” said team member Gamuchirai Mutezo.
In Mamelodi, for example, where there was limited access to electricity, a landfill produced copious amounts of methane.
“It can be captured and converted into electricity or scrubbed and used just as biogas for cooking. Instead of waiting for grid connectivity, landfill gas is then decentralised and made more accessible.”
Methane from coal mines in an area such as Witbank could be used in neighbouring households or even to operate the mines themselves.
Stellenbosch students worked on a waste-water refinery that uses bacteria to turn organic matter in waste from wineries and abattoirs into products such as biohydrogen for transportation fuel.
Team member Bovinille Anye Cho said the process required little energy because it relied on sunlight, atmospheric pressure and ambient temperature, yet its yield was far superior to other forms of fuel.
“Meanwhile, the reusable water contains nutritious elements for the soil, for example nitrogen and phosphorus,” he said.
All the students’ technology is in the development stage. As such, economic viability must be tested and public-private partnerships sought.

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