Gases from Cape Town’s mountains of rotting garbage could one day help to keep the city’s lights on while being kind to the environment, thanks to a new plant at the Coastal Park landfill.
The City’s department of solid waste management launched the landfill-gas-flaring project at the dump earlier this month. It’s the first of its kind in Cape Town. Two more plants are planned for landfills in Bellville South and Vissershok.
The plant is a cluster of pipes and wells and its nerve centre is a shipping container that houses a computer system monitoring gas emissions.
The landfill produces 50% methane, 40% carbon dioxide and a 10% mix of other gases. The landfill gas is flared to stop the methane adding to other greenhouse gases in the atmosphere that cause global warming and climate change.
The plant only flares the gases now but they could, at a later stage, be converted into clean energy… electricity added to the national grid or enough fuel for 128 trucks a day. But it’s the electricity option the City is interested in.
During the Echo’s visit, Peter Novella, a solid waste department manager, said the plant could produce about 1.5 to 2 megawatts a day for the next 20 years, based on estimates of available gas.
While he conceded that that was not a lot of electricity it was significant because it was green energy.
Generators will be installed in phase 2 of the project to feed electricity into the grid.
The first phase, Mr Novella said, was about managing the gases produced by rotting organic matter in the landfill and keeping them out of the atmosphere as per the Kyoto Protocol, an international treaty which extends the 1992 UN Framework Convention on Climate Change (UNFCCC), that commits countries to reducing their greenhouse gas emissions.
“Methane is 25 times more dangerous to the atmosphere than carbon dioxide and emissions are improved when methane gas is destroyed,” he said.
The plant, he said, was a milestone for a project that had taken years and a lot of work by officials to develop a UN-approved clean development mechanism (CDM), which allows developing countries to set up carbon-offsetting projects that developed countries could invest in by buying carbon credits.
According to Fountain Green Energy (FGE) site agent Mark Zunckel the plant has vertical and horizontal wells, well heads, condensate traps, pipelines, gas blowers, measuring instrumentation and a gas flare.
The vertical wells are between 18 to 30m deep and the horizontal wells are shallower and waste is still added to it.
The organic matter in the landfill decomposes anaerobically (in the absence of oxygen at about 50 to
60°C ) and forms a landfill biogas rich in methane, which is highly combustible and can be used as a fuel or to generate electricity.
Suction is applied through the vertical well and when the gas reaches the surface of the well at an ambient temperature of 20 to 25°C, condensation takes place.
The toxic condensate is pumped out to a dam and then to treatment works as it cannot go back into the environment.
From there the gas will get extracted with slight suction to the suction station and gets pressured into a positive pressure, goes through the burners and gets destroyed. The gas burns inside the burner at about 1000°C. The flame is not visible from the outside.
Mr Zunckel said there were safety protocols for a plant shut-down should the methane reach dangerous levels.
Xanthea Limberg, Mayco member for informal settlements, water, waste services and energy, said the project would help Cape Town reduce its carbon footprint.
Professor Harald Winkler, from UCT’s Energy Research Centre, says the main advantage of a landfill-gas project is it captures methane.
“One ton of methane has about the same effect on global warming as 28 tons of carbon dioxide, over a hundred years. However, methane is a much shorter-lived gas, and its effect over 20 years is 84 times as strong as that of carbon dioxide, the main greenhouse gas.”
He said methane was not harmful to humans in low concentrations but should they be exposed to high concentrations of methane, they might experience a shortage of oxygen. But that would require enclosed spaces and landfill sites were generally open. “Landfill sites may contain toxic substances, other than methane. However, the methane is generated by the organic fraction of municipal solid waste which is not toxic,” he said.
