Waste collection and transport are the public face of waste management. Landfills are the backend that keeps the sector going. As South Africa adopts circular economic practices, landfills still hold a key position in the waste sector, and act as the foundation for a circular economy.

Brendon Jewaskiewitz, managing director of Envitech, says, “In the South African context, landfills are crucial. Even if you look towards developed countries that have low waste to landfill, there are still landfills. They are an essential component of any waste management system and serve as a ‘final sink’ for materials that cannot otherwise be utilised for another purpose. They can also form part of an overall waste management facility which could include materials recovery and recycling, landfill gas extraction and utilisation, and possibly energy from waste.”

Unfortunately, about 80% of South Africa’s waste ends up in landfills or uncontrolled dumps. There are very few effective separations at source initiatives, and while recycling and other waste diversion initiatives are growing, landfills form a critical basic building block of the waste sector.

Far from a space to simply dump waste, landfills are highly organised and engineered spaces. Jewaskiewitz explains, “Landfills are not open pits – they are designed and managed spaces, subject to regulation. Engineered landfills are located in carefully selected areas. A rigorous site selection process is carried out to minimise the risk of ground water contamination, noise, dust, and sound pollution, with due consideration of the communities and surrounding environment. These sites are subject to stringent environmental protection measures that must be followed. The antithesis to this is an illegal dumping site where waste is improperly managed, often causing environmental and social harm. Properly designed, constructed, and managed landfills are integral to the health and safety of the people of South Africa.”

As environmental knowledge expands, and modern technologies emerge and improve, landfills themselves become ‘greener’ than previous iterations.

“The technologies we have available, especially in terms of construction materials, geosynthetics, and quality assurance measures, result in landfill sites being developed to protect the environment for well over 100 years, longer than the expected lifespan of a site. These sites are designed to prevent leachate and gas emissions and minimise environmental harm. And once the landfills have been capped, the surfaces can be used as recreational parks, solar farms or the like when space is limited.”

Landfills, the centre of new sustainability

South Africa has very low levels of separation at source, making landfills a necessity. This also means that landfills often act as a centre where waste pickers reclaim valuable materials, and where recyclables can be recovered. The secondary use of a landfill is really to maximise the sustainable potential of the site. Leachate, a genuine environmental concern, can be captured and treated to an environmentally acceptable level for discharge, and landfill gas can be extracted and utilized effectively.

The current state of the South African waste sector is such that while modern technologies, recycling, and repurposing waste are expanding, landfills remain necessary. “What we have in South Africa is an opportunity for landfills to become a centre point for other circular activities. Waste pickers use landfills as a resource, reclaiming can be done on site, and they can become a contact point for industrial symbioses. Landfills can become hubs for circular practices,” explains Jewaskiewitz.

Landfills that accept organic waste can become a viable source of gas. “Organic waste in a landfill undergoes anaerobic decomposition in the absence of oxygen. This results in the generation of landfill gas, comprising methane, carbon dioxide, and small quantities of trace gases such as hydrogen sulphide, for example. These gases have the potential to cause environmental harm, if left unmanaged, but can also be captured and utilized sustainably,” says Greg Fridberg, director at Envitech.

Landfill gas

Unless it is captured and destroyed, the carbon rich gas arising from the landfilling of organic waste is emitted directly to the atmosphere, exacerbating climate change. For this reason, organic waste is often diverted from landfill, but in South Africa, the separation of waste streams is not anywhere near effective enough for this to have a tangible impact. Whilst various industries and large organic waste producers have the option to divert, household organic waste typically ends up on landfill sites.

“The methane rich gas produced on these landfills could potentially be harvested for fuel, or even just flared off,” says Fridberg, “Landfill gas has the potential to aid in circularity if correctly managed. Simply destroying the gas through flaring is already far more environmentally friendly than letting it emit freely from the site, but some landfills have the added potential of utilising the gas as a source of energy, and additional revenue can also be generated though the sale of carbon emission reductions.”

The first step is assessing if the landfill can viably produce useful volumes of gas. A gas yield modelling study is part of an in-depth feasibility study undertaken before any investment takes place.

“The study would consider the quantities and classification of the waste in the site, the waste coming in, and the physical and climatic conditions on the site. Most of these models are developed using proprietary software. Once the various data is compiled and run through the software, the modeled results will provide an indication of whether the site could be a viable candidate for gas harvesting,” says Fridberg.

Once the modeling is done, a pumping trial is usually recommended to verify actual gas recovery conditions, and to calibrate the theoretical model. A few vertical gas recovery wells are constructed and connected to a small flaring station, with the gas being pumped and flared for about six months to verify sustainable gas recovery rates. If this trial succeeds in confirming the viability of a landfill gas recovery project, several vertical and horizontal gas recovery wells are then constructed in the landfill. These are connected via gas collection pipework to a full-scale blower and enclosed flaring unit, often located within a secure compound together with all relevant electrical infrastructure and control instrumentation.

Fridberg explains, “In many developed countries gas is used for both heat and electricity generation. The gas can also be pumped to factories that use it for kilns and boilers. In the South African experience, landfill gas has been used primarily for clean electricity generation. The gas is used to power reciprocating gas engine generator units, and the generated power is fed into the local municipal grid. There are also opportunities available for the sale of carbon emission reductions arising from these projects.”

Struggles and growth

The main obstacles to using landfills as a hub for other sustainable activities are typically the same obstacles that prevent landfills from being developed and operated effectively. The low separation at source rates, deficiencies in the effective collection and transportation of waste, illegal dumping, and poor landfill management – both due to a lack of law enforcement – are all contributing factors. Jewaskiewitz also notes, “the ongoing lack of funding for municipal landfills and non-compliance with regulations remain among the highest barriers to change. Along with having to import technology, the capital investment required, and maintenance costs are also often a significant barrier.”

These sites have the potential to be a base for the circular economy, and Fridberg adds that the “increasing clean energy demand, along with diversifying the energy mix, will be driving factors in developing landfill gas to energy on landfill sites.”

Jewaskiewitz concludes, “It is important to remember that landfills are essential facilities, and that these activities remain secondary to the primary function of the landfill. These sites should be properly designed, constructed, managed, and operated, thereby enabling other activities such as materials recovery or gas extraction as an additional benefit.”