4 September 2008
Johannesburg is about to embark on its first landfill-gas-to-energy projects, which will be the first notable Clean Development Mechanism (CDM) project generating substantial carbon credits, which the metropolitan municipality can then use for trading.
The due diligences for the Linbro Park, Marie Louise, Robinson Deep, Goudkoppies and Ennerdale landfills were concluded in March this year, proving that all the sites have enough potential quantities of landfill gas to generate electricity.
Landfill-gas-to-energy CDM projects will be initiated at all five sites, and a consortium headed by ENER•G Systems Joburg has since been appointed by the municipality to take the process forward.
“The successful bidder, ENER•G Joburg, will incur all costs relating to the development of the projects right up to the trading of carbon credits and power that would have been generated by then,” said the municipality’s director for waste services, Palesa Mathibeli.
The municipality and ENER•G Joburg will share the profits resulting from the sale of carbon credits and electricity.
“The primary aim is to harvest methane gas from landfill sites for the purpose of generating power and to generate carbon credits for trading,” Mathibeli said.
The sites can produce as much as 20 to 25 megawatts of electricity for about 15 to 20 years, but the rate of gas production is dependent on a number of variables, including the age and composition of the waste, the temperature and moisture content of each site, and the design and operation of the site, among others.
Using the gas
Because it is now mandatory for cities to manage landfill gasses, flaring of methane gas will be undertaken irrespective of whether the site can generate electricity or not, Mathibeli said.
“The flaring of methane gas reduces the amount of greenhouse gases emitted to the atmosphere and improves air quality.”
Flaring produces carbon dioxide, which is a far less harmful greenhouse gas, while methane is considered to be up to 21 times more noxious than carbon dioxide. The gas may also be used for other purposes, such as heating.
Once the projects are under way, the air and water quality of the landfills will be closely monitored.
“Although it is acknowledged that all landfills do generate leachate and landfill gas, the scientific quantification thereof is not available at the moment,” Mathibeli said.
Leachate is a liquid that forms when water comes into contact with landfill waste and consists of various contaminants. It has a strong, offensive odour and is yellow-orange in colour.
Before the projects can begin, however, the municipality needs to complete environmental impact studies, which include public participation processes.
“This is not only a requirement from the national and provincial government, but also a requirement by the United Nations Framework Convention on Climate Change,” said Mathibeli.
Except for Linbro Park which was closed in 2006, the sites are still operational. Studies have proven that operating sites yield more landfill gas than closed ones.
The landfills in Kya Sands and Panorama have been closed for a long time and did not form part of the feasibility study as they were considered to be uneconomical.
Gas can be harvested while a landfill is still operational and for up to 50 years after closing the site. Once a landfill has been closed, it will be rehabilitated in line with the end-use closure permit. It could become anything from a new park to a cricket pitch or a golf course.
The landfills earmarked for the projects are at Houthammer Road, Devland; Marlboro Drive, Sandton; Dobsonville Road, Roodepoort; Turffontein Road, Turffontein; and Old Lawley Road, Lawley.
Source: City of Johannesburg