CER Bisasar Rd_January 2011_edit BWaste in landfills undergoes biological, chemical and physical transformation, giving rise to the formation of landfill gas. Landfill gas (LFG) can be extracted and safely utilised to generate power – aka “green energy”.
This project introduced a first-of-a-kind to South Africa and the African continent as a whole. It was one of the very first CDM’s worldwide when it was first introduced in 2002/3 and went on to become the first registered Kyoto Protocol’s Clean Development Mechanism (CDM) type project in Africa in 2006.
The project comprises two landfill sites namely Mariannhill and La Mercy that contain approximately 2.7 and 1.2 million m3 of disposed municipal solid waste respectively. Landfill gas is extracted through gas wells that are either vertically driven into the waste or inclined “gas riser” pipes located around the landfill perimeter laid on top of the slope lining system. Wells are typically not deeper than 25m in depth.
The landfill gas is sucked from the landfill at low pressure (15~50 millibars) and blown into a flare unit and reciprocating spark ignition engine through a roots blower system. Previously gas was flared at Mariannhill Landfill through 6 “baseline” gas wells.
This CDM project is termed “Component One” (Mariannhill and La Mercy Landfills) of the Durban Landfill Gas to Electricity CDM project. “Component Two” is the larger Bisasar Road Landfill CDM project. Waste is to be deposited at the Mariannhill landfill beyond 2024, and it is predicted that 1775Nm³/hr of landfill gas will be produced by 2024.
There are 6 “baseline wells” on the site currently producing some 65~100m³/hr and 7 new “project wells” have recently been installed. A further 20 gas wells are planned to still be installed into the site. Calculations show that gas utilisation equipment up to a capacity of 1.5MW will be required up to 2020. If a greater gas yield is sustained, then larger engines may be installed.
Fourteen (14) new gas “project wells” have been installed at the La Mercy landfill and there are no “baseline wells” since no gas extraction was carried out previously. Gas production at La Mercy is calculated to peak at 770m³/hr. However, extraction from the site is proving to be difficult owed to much leachate trapped within the disposed waste body. An additional 4 wells are to be constructed in 2007 to obtain a more optimum gas yield from La Mercy. A 500kW generation unit is installed at La Mercy and is expected to be operational through to 2013.