Organic waste could be viable energy source for South Africa

Nov 14, 2008 01:00 AM

by Brindaveni Naidoo

Organic waste generated in South Africa has the potential to generate an alternative energy source, through harvesting biogas from the fermentation of the organic fraction of municipal solid waste (OFMSW). This process could thus assist in providing heat and electricity.
"From organic waste to energy: a feasible option in South Africa?", a paper produced by the Council for Scientific and Industrial Research, says that, with the observation that State-owned utility Eskom was not able to supply the power needed by South Africa at the beginning of 2008, the mindset of waste companies and municipalities should change from "waste to landfill" to "waste to energy".

Currently, most waste generated in South Africa is disposed of in landfills but the scarcity of available land in close proximity to areas of waste generation has caused landfilling to become a less attractive option. Further, landfilling often causes unwanted gas and leachate production.
Through anaerobic digestion (AD), a biological treatment process applied to the OFMSW, which has become an established treatment process in Western Europe as well as in several Asian countries, products, such as biogas and a nutrient-rich sludge, are generated from this technology. The biogas produced is a potential energy source and the nutrient-rich sludge has beneficial value as a fertiliser.

However, the biological treatment of the OFMSW is marginally recognised in South Africa, the paper says, adding that this is a result of "relatively inexpensive landfill fees and a lack of an energy policy that recognises organic waste as an energy source rather than just a waste material".
Author of the paper Harma Greben says that the thinking around biological treatment in South Africa is starting to change. A study conducted for the Department of Science and Technology by a University of Cape Town team led by Professor Harro von Blottnitz, to evaluate the opportunities for energy from waste to influence policy in this regard, concluded that waste to energy has an "exciting future" in South Africa, but only when approached innovatively and responsibly.

The report further points out that, when using AD technology for energy production, one has to consider the environmental, social and economic aspects of the different locations in the country. For example, in poorer communities, especially in informal dwellings, gas, paraffin, wood and coal are often used for heating and cooking, which have the potential to be unhealthy, owing to inhalation of fumes associated with burning these fossil fuels.
However, the OFMSW can be separated at source and codigested with manure in an anaerobic digester, and the biogas produced can supply heat and light to the communities, which is a much safer and inexpensive option. An example of using biogas from waste can be seen in Gawula, in Mpumalanga province, where manure is being converted in a 4-cm digester, already producing 0,5 cm of gas, used for cooking.

Other developments in SouthAfrica include a biogas digester that converts human waste into energy, which is being tested at Ivory Park Urban Ecovillage, in Midrand, north of Johannesburg, and, further, the Agama team is involved in the building of anaerobic digesters treating organic waste to gain energy in several areas in the country.
In the city of Stockholm, in Sweden, the codigestion of sewage sludge with organic waste produces biomethane gas, which is used as fuel for about 5 % of the city's bus fleet. This is yet another attractive option for South Africa, given the high cost of fuel.

The study undertaken by the CSIR entailed investigating the biogas production when kitchen waste, combined with wet paper and later only dry paper waste, is digested in a laboratory-scale AD plant. The results indicated that AD for the OFMSW is feasible, and that the mindset of municipalities can be changed in terms of the treatment of organic waste.
According to the report, which will be discussed at the second CSIR biennial conference,to take place in Pretoria, from the November 17 to November 18, the biogas produced is an alternative source of energy, which is recognised in Europe and China. Taking organic waste out of landfills and into anaerobic dig- esters is an important consideration in light of South Africa's energy shortage, evidenced by load-shedding, earlier in 2008.

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