SA Alternative Energy Association | 02 June 2013
With the number of people in Africa’s urban centres expected to grow rapidly in the next few decades, municipal waste and its disposal could pose a variety of logistical and public health challenges. Now, researchers at the University of Cape Town, in South Africa, are examining how to convert organic waste into biogas, which would alleviate disposal problems and help poor residents, particularly those in informal settlements, save on energy costs.
The number of people living of Cape Town is expected to grow almost 60 percent in the next three decades, according to a projection by the city. Meanwhile, energy prices, including the cost of electricity, have gone up at least 50 percent in the last four years.
University of Cape Town (UCT) researcher Rethabile Melamu told IRIN, “Up to 70 percent of organic municipal waste could be used to create biogas… We are going to set up a biogas project near an abattoir and use the leftover blood and animal waste to create fuel that can be used for cooking and heating water.”
The process of turning waste into gas involves the breakdown of organic waste in an oxygen-free environment called a biodigester – usually a large rubber bladder or a concrete structure, depending on the scale of the project – which operates like a human stomach.
This produces methane gas that can be siphoned off and used for cooking and to replace paraffin, an increasingly expensive fuel commonly used in informal settlements.
In June 2012, a grant of about US$305,000 was provided by the National Research Foundation to UCT for small biogas demonstration projects.
UCT partnered with the NGO Engineers Without Borders (EWB) and African Green Energy, a private company, to install a rubber-bladder biodigester at the Siyazama Community Garden in Khayelitsha, an informal settlement outside Cape Town, last year.
EWB volunteer Francois Petousis said it cost about $1,200 for the raw materials and labour to install the biodigester, which has a 10-year lifespan. The community gardeners grow vegetables and use the organic waste to fuel the system.
Cynthia Nkqayi, a group leader at the garden that supplies vegetables to Abalimi, an urban agriculture association, believes the biodigester is a great addition to their operation because they use gas for cooking every day. It has also saved them money. “We used to buy about R300 [$36] worth of gas every two months for cooking, so it is a big saving for us to have the biogas here, as it is free,” said Nkqayi.
There are similar pilot projects underway across the country.
Melamu, who has researched biogas since 2000, believes it is not a fuel that could replace traditional energy sources, but that it should be added to a mix of renewable energy sources like solar and wind power. “Biogas system installations have creased steadily since 2000, and now there are thousands of systems … around the country,” she said.