Reusing food waste is a gas

UCT research officer Rethabile Melamu shows off a new biogas digester used to produce methane gas which can be used for cooking.

UCT research officer Rethabile Melamu shows off a new biogas digester used to produce methane gas which can be used for cooking.

Published Jun 20, 2011

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MARY BETH BARKER

Staff Reporter

THERE’S nothing wasteful about the food waste on UCT’s campus, thanks to a chemical engineering department initiative which will see it used to produce methane gas, which can in turn be used for cooking.

The biogas digester, launched last week, is a container in which waste food rots, producing the gas. The system is used widely in rural areas, but UCT plans to show it works equally well in an urban environment.

The 2.2m by 2.5m pre-fabricated plastic digester is buried behind one of the university’s Tugwell Towers. Two round plastic covers which can be lifted in order to dump food, and to monitor the water level, are the only sign that it’s there.

Gas produced from the rotting food flows into a line, which leads into the kitchen of the Leo Marquard Hall residence, where it powers a medium-sized portable stove.

The digester is being “fed” half its 35kg potential weight, producing enough gas for about 30 minutes of cooking time. At full potential it will produce up to an hour of gas twice a day, helping to cook food for the 400 student residents.

Professor Francis Petersen, dean of UCT’s engineering and built environment department, said the project was linked to the university’s broader goal of reducing greenhouse gas emissions, and becoming a carbon- neutral campus.

The success of the digester proved “it is feasible to generate energy from separated waste in an urban environment”.

The project began in February last year when students and lecturers from the chemical engineering department teamed up with the staff at the Leo Marquard Hall residence. An initial research team studied the smell the digester could emit, ownership and upkeep.

The digestor was installed during the end-of-year holiday at a cost of about R30 000.

Most of the funding came from the vice-chancellor’s strategic fund. A rough study by the engineers predicts it will take about five years for the digester to pay for itself through energy savings.

The engineering team plans to expand its initiative, with the next installation to include the full integration of energy, solid waste and sanitation, incorporating the disposal of human waste.

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