South Africa’s metros are racing to plug electricity gaps and meet the Waste Act’s diversion targets before 2030. Yet on the fringes of almost every city lie dozens of long-forgotten legacy dump sites — un-engineered mounds that still belch climate-heating gas and contaminate nearby streams.
Rose Morrison, environmental engineering and infrastructure writer.
From dormant dumps to living assets
South Africa has more than 1,000 legacy dumps, many located near dense settlements. A report by Project Drawdown shows that converting such sites to actively managed bioreactors can cut methane emissions by as much as 85%. A landfill bioreactor is a type of landfill that’s actively managed instead of sealed and left alone. Workers add air or moisture, recirculate the liquid that drains through the waste and control temperature so microbes break down organic materials faster. This accelerated decay creates a steady stream of landfill gas — primarily methane — for capture and use in power generation or upgraded into biomethane for fuel. Because the waste stabilises quickly, leachate is easier to treat and the environmental impact is lower than in a conventional landfill. If you need a mental image, picture stacking 10 floors of rubbish across 10 soccer pitches. That much mass is enough to keep the gas flowing long enough to pay for the pumps and engines. Anything smaller rarely justifies a full power plant, but it’s still possible to cap and flare it for safety.Why the construction sector should care
Construction is resource-hungry, and the sector often takes the blame for half of climate-changing outcomes, half of all waste sent to landfills, 40% of water pollution and 40% of global energy consumption. In South Africa, load-shedding and rising landfill fees magnify those numbers. Converting close dumps into energy-making bioreactors trims that footprint on three fronts.
- Power: On-site engines keep concrete batch plants humming during blackouts.
- Emissions: It’s possible to capture and burn methane instead of allowing it to escape.
- Materials: The pile compacts as the waste breaks down, leaving mostly inert soil-like rubble behind. Engineers can excavate this material and use it as the gravel sub-base beneath new roads, so there’s no need to quarry fresh stone.
How the gas under the ground earns its keep
Buried organics start giving off LFG within one to three years — the flow peaks around the fifth year and can keep going for 20 more. A steady 1,000 m3 of gas per hour — about the size of an Olympic pool every two years — spins a one-megawatt generator. Capturing that gas turns a silent, invisible problem into power for cities. That’s why eThekwini revived the stalled Marianhill project in 2025 and why Cape Town rushed to switch on two more LFG-to-power schemes at Bellville South and Coastal Park at the end of 2024. A carbon-credit auction in 2024 pulled in R36 million for engine procurement — proving that investors will back landfill gas projects when the numbers stack up.Why other sectors are jumping in
Once the engines start humming, a bioreactor landfill becomes a miniature utility hub. Wastewater plants pipe the warm water cooling the gas engines into sludge digesters, shaving thousands of rand off treatment-plant electricity costs per month. Road engineers like the project because they can use compacted, bio-stabilised rubble dug from old cells to lay new sub-bases. Energy planners welcome the extra megawatts since landfill gas is fully dispatchable — plugging the evening gap when rooftop solar fades and diesel prices rise. Even telecom companies are joining — low-cost LoRaWan sensors screwed onto each gas well feed live methane readings to a dashboard, and a Durban pilot who sees those smart nodes can reduce routine site visits significantly. Financiers have caught on just as quickly. South Africa’s National Waste Management Strategy insists on diverting 30% of waste from landfills by 2035, so banks now label bioreactor projects “green-loan eligible.” Once the gas begins flowing, the financial aspect can be as compelling as the environmental one.Converting yesterday’s dumps into tomorrow’s power hubs
Landfill bioreactors prove that Africa’s closed dumps are anything but dead ground. Municipalities can transform methane leaks into megawatts that steady grids by recirculating leachate, re-wetting the waste and drawing off the gas. The same retrofit shortens settlement time, slashes fire risks and odour and frees reusable aggregates to deliver climate, health and economic dividends in a single build. Converting legacy dump sites into energy production centres is a practical and bankable way for South Africa and its neighbours to add clean power, reclaim land and meet diversion targets.
Landfills have the potential for energy conversion
