The power of waste

At its facility in Germiston, Interwaste specialises in producing refuse-derived fuel materials. The final processed material is close to A-grade coal quality in terms of its calorific value

As populations increase, so too do waste streams, placing increasing pressure on their safe disposal. For waste that cannot be recycled, there are other alternatives, like energy generation, says Kate Stubbs, group marketing director at Interwaste. By Alastair Currie

Kate Stubbs, group marketing director at Interwaste A South African company with a 33-year track record for innovation, Interwaste forms part of French multinational waste management specialist Séché Environnement, which operates in 15 countries across Europe, South America and Africa.

Locally, Interwaste’s integrated solutions cover the full spectrum of general and hazardous waste, with the company operating its own licensed Class B waste landfill in Delmas, Mpumalanga. Allied operational focuses encompass waste-to-energy, waste recovery and complex hazardous waste treatment solutions.

“The strategic advantage of being part of the Séché Environnement group is that Interwaste can draw on best-in-class technological solutions that support our offering within the Southern African region,” says Stubbs.

A prime example is the development of a new leachate and industrial effluent treatment plant at its Delmas site. The first of its kind in South Africa, the plant is currently under construction and scheduled for commercial operation by the end of the first quarter of 2023.

“In line with current and future legislation, Interwaste’s strategy is to provide clients with expert advice on how best to manage and implement processes that optimise their waste streams, both from a sustainability and operating cost perspective,” Stubbs explains.

Waste as a resource

Handled correctly, waste can be a valuable resource that promotes reuse, growth in the circular economy, and a zero waste-to-landfill methodology. “The reality is that South Africa is fast running out of landfill airspace, and constructing new facilities is not the only answer from an environmental standpoint. Therefore, we need to find solutions urgently, drawing from international best practice,” she continues.

For waste that cannot be recycled, one highly viable option is to reprocess this as an alternative fuel source. In parallel are renewable waste-to-energy opportunities derived from landfill gas, organics, as well as wastewater treatment plants.

In developed countries, waste-to-energy is a common practice and receiving increasing focus. Within France, for example, Séché

Environnement operates various large-scale plants. These include its project in Laval, France, where landfill gas is converted into energy, alongside the production of a refusederived fuel (RDF), both of which provide the town with its power requirements.

Another example is Séché Environnement’s operation in Lyon, France, where hazardous waste from a local chemical plant is processed and converted into energy using thermal destruction technology. In terms of its agreement with the client, the electricity generated is wheeled back to power the plant.

South African opportunities

“There are major opportunities for South Africa to harness the value of waste-to-energy as we transition away from fossil fuels. Plus, it’s very evident that – on top of our growing waste crisis – South Africa has a power crisis that needs urgent interventions,” says Stubbs.

Within the renewable energy space, solar and wind are the most logical options for clean, net-zero power. However, Stubbs points out that waste-to-energy plants serve the added benefit that they can also safely dispose of toxic and hazardous materials that cannot be reused, alongside more renewable biogas options.

Based on studies, wind and solar typically cost less than R1/kWh to produce, and waste-to-energy around R1.50/kWh. However, the added cost is outweighed by the environmental gains.

“There is a general perception that waste-to-energy pollutes. In fact, thanks to technological advances, the emissions from these processes are often cleaner than the air around us,” says Stubbs.

Assessing commercial viability

As for any recycling initiative, the crucial starting point for a waste-to-energy project is commercial viability. “Of foremost importance is understanding your feedstock – what type of waste you have, its quality, quantity and consistency. This will determine the technology to employ, which must be appropriate for the South African market. Equally important is a guarantee of constant, 24/7 waste streams to feed the plant to ensure a sustained energy baseload, plus a secure independent power producer agreement so that the commercial model works in practice,” Stubbs explains.

A working example is Bio2Watt, based in Bronkhorstspruit, which operates a 4 MW anaerobic digestion plant that supplies electricity to an automotive manufacturer in Rosslyn in terms of an offtake agreement. Interwaste supplies Bio2Watt with some of its feedstock requirements.

Essentially, anaerobic digestion produces natural, methane-rich gas during the decomposition process, which is then converted into electricity.

Organics ban

In terms of South African legislation, a national ban will be imposed on the disposal of organic waste to landfill by 23 August 2027. As a proactive measure, the Western Cape Provincial Government took the decision to start the process early and, in 2022, has set a 50% landfill reduction target for organics.

Organics in landfills create methane gas, which is far more toxic than carbon dioxide. Additionally, methane creates leachate, which poses a risk in terms of groundwater contamination. For existing sites, part of the environmental solution is to install biogas plants that can convert this methane to usable energy.

“There’s no doubt that the opportunities for anaerobic digestion and biogas plant operators are favourable going forward,” says Stubbs.

RDF

Within the mix, RDF is another waste-toenergy platform gaining traction. The latter is created from solid, dry, non-recyclable waste typically found in industrial and municipal waste streams. A prime candidate is the multilayered material used in the FMCG sector, such as foil plastic packaging, which can be especially challenging to recycle.

At its facility in Germiston, Interwaste specialises in producing RDF materials. The final processed material is close to A-grade coal quality in terms of its calorific value. It can be used as a fuel source for firing cement kilns as a supplement or alternative to coal.

Hazardous liquid wastes (such as hydrocarbon sludges), oils and greases with a calorific value – but not pure enough to be converted into more direct fuels – can also be processed for thermal energy. For this purpose, Interwaste uses a blending platform at its Germiston operation that employs a special formula to create an alternative liquid fuel suitable for co-combustion with traditional fuels.

Interwaste’s research and development teams continue to explore solutions suited to the South African market that can process waste of any complexity.

“There has to be a shift in our thinking towards waste. It’s happening, but there needs to be far more public and private sector collaboration, and funding support for waste infrastructure. Within this context, wasteto-energy projects make environmental and commercial sense, and need to become a permanent feature of South Africa’s power mix,” Stubbs concludes.

There are major opportunities for South Africa to harness the value of waste-toenergy as we transition away from fossil fuels.”