The City of Cape Town (CoCT) says it is moving closer to turning landfill waste into energy, with two projects that are designed to produce electricity from the combustion of landfill gas moving towards implementation.

Landfill gas, primarily made up of methane, is produced when organic matter, such as food scraps, breaks down at landfill sites.

To convert this gas into electricity, perforated pipes or ‘wells’ are dug into a landfill site to channel it as a fuel to produce electricity in specially designed engines.

CoCT Urban Waste Management MMC Grant Twigg tells Engineering News & Mining Weekly that the Coastal Park landfill site waste-to-energy project is awaiting the installation of a thermal mass-flow meter before the gas engines can be put into operation, while the process to permit the connection of the engines to the electricity grid is ongoing.

Should everything run according to plan, the estimated date for first electricity production is sometime during the second half of this year.

At the Vissershok landfill waste-to-energy project, Twigg says, there have been some delays with the appointment of a gas-flare operator owing “to complexities and complications in the procurement process”.

This has impacted the timeline for the development of the detailed designs for the waste-to-energy component, “pushing this out significantly.”

“The first 2 MW generation infrastructure at Vissershok is scheduled for implementation in 2026/27, increasing thereafter to between 7 MW and 9 MW of generation capacity by 2028/29, depending on gas yields.”

Just shy of R79-million has been budgeted for Phase 1 of the Vissershok project, which includes two generator sets, various filters and controls, as well as setup, installation and connections costs.

Further costs will be incurred for Phase 2, says Twigg, but it is too early at this point “to indicate these costs”.

He adds that the Vissershok landfill site is an Eskom-supplied site, with initial investigations showing that the local grid may be able to take up to 7 MW of electricity that could be fed into the grid.

This would, however, require confirmation during the design stages of the project.

The expected capital outlay for the Coastal Park energy project is R73.58-million.

Twigg says the electricity generation capacity of this project will be about 2 MW.

Some of this electricity will be used to power the new recycling facility that is under construction at this site.

While the process to put the gas engines into operation is under way at this site, CoCT is using a flaring system at the end point of the well system to destroy landfill gas before it can enter the atmosphere.

Landfull gas has a global- warming effect estimated to be 25 times higher than carbon dioxide.

The flaring and electricity generation system at Coastal Park has been designed in such a manner that it can earn the city carbon credits.

The proceeds from a planned auction of these carbon credits will be ringfenced to fund projects of the city’s Urban Waste Management Directorate aimed at reducing the impact of pollution.

Twigg says it is unlikely that the Coastal Park project will be expanded, given that the site is set to close down “in the next few years”.

However, the project will go ahead as landfill gas continues to be generated for 10 to 15 years after the closure of a landfill, albeit at a slightly decreasing yield year-on-year.

“This is evidenced by the fact that the Bellville South landfill, which closed in 2018, is still generating landfill gas eight years after the landfill was closed,” says Twigg.