Volume 7, Number 2 - March/April
25 Degrees in Africa - Water
A closer look at waste-to-energy projects
Waste-to-energy projects in South Africa will increase as the national government urges municipalities to get involved with the programme. 25º in Africa gives and overview on the feasibility of such projects and the prospects of implementing it successfully in the country.
Written by Nichelle Lemmer
Most people don’t see the value of waste. People throw their garbage in a bin and don’t think twice about what happens to it after this. The reality is that waste can add value to society if it is recycled and used to generate energy. By changing people’s perspective on waste, they have the power to create a more sustainable future.
While the rest of the world rapidly deploys waste-to-energy (WTE) plants, the emphases on this method of disposing waste is only gaining momentum in South Africa in the last year.
Leon Bredenhann from Golder Associates says the new national waste management strategy that was recently released specifically stipulates that municipalities should invest and look out for opportunities to launch WTE projects.
According to the website www.earthlife.org.za, a growing number of projects are being proposed for South Africa under the label of waste-to-energy where waste such as anatomical hospital wastes, bio-hazardous wastes, electronic scrap, municipal domestic and industrial waste, worn-out tyres, solvents, plastics and sludge are burned instead of coal.
A burning issue
According to a research paper called Waste to Energy done by Ronald Harley, chief technology officer of Xicon Infrastructure, waste-to-energy refers to the process of turning municipal solid waste (MSW) into a source of heat and then into electricity. The paper illustrates several methods used to convert MSW into energy. It can be done using thermal processing like combustion, pyrolysis, gasification, plasma arc or refuse-derived fuel. Chemical conversions like composting, biomethanation and landfill gas can also be applied.
The research paper fully illustrates the different types of methods. Pyrolysis is the degrading of MSW under pressure without the presence of oxygen, allowing for the formation of char, pyrolysis oil and syngas. It is accomplished with temperatures between 500 and 1 000 degrees Celsius.
Gasification involves higher temperatures than pyrolysis and includes a small amount of oxygen to form syngas. Plasma arc is useful for the treatment of biomedical waste due to the high temperature at which the process occurs, and involves the decomposition of MSW into its basic elements with an electrical arc between two electrodes, resulting in a hydrogen-rich plasma-converted gas (PCG).
Refuse-derived fuel (RDF) is the process of converting sorted MSW into dense pellets that burn more efficiently than untreated, unsorted MSW. RDF can be used as a fuel in a combustion process, which is the mass burning of MSW either by mechanical grate or by a circulating fluidized bed (CFB). For the combustion process, temperatures vary from 800 to 1 000 degrees Celsius, and combustion is most efficient if the MSW has less than 50% moisture.
The website www.earthlife.org.za states that it is important to note that the outcomes of burning WTE depend on the type of waste that is being burned. Certain wastes, like biomass such as agricultural waste, can be safely burned for energy, although bio-digestion to produce gas as a fuel and compost is generally preferable. “When waste has chlorine or metal in it, as in plastics, tyres and solvents, burning it doesn’t destroy the toxins. Instead it displaces some to landfills in the sky and concentrates the rest to create toxic ash,” it cites.
According to the Xicon Infrastructure research report, landfilling and wastewater are the two greatest producers of greenhouse gas (GHG) emissions, with landfills producing pollution for decades. “Not only do WTE facilities reduce these GHGs, but it also helps to substitute the need for burning fossil fuels by providing both electricity and heat.” The research report shows that GHG emissions from WTE, particularly carbon dioxide, are significantly lower than from burning coal, oil or natural gas.
Bredenhann also believes that WTE contributes towards mitigating global warming and reduces the country’s dependence on fossil fuels.
He is of the opinion that the WTE projects will also grow the green economy and is in line with South Africa’s goal to create more jobs. “A huge variety of jobs will be created when these projects are running.” According to him, municipalities could also reap financial benefits if WTE projects enable them to sell a supplementary supply of electricity generated by these projects to the national grid.
There are several factors that determine whether or not a WTE plant is suitable for a certain location. According to the Xicon Infrastructure research report, factors like a region’s economic strength, the national policies and laws regarding the handling of MSW and the infrastructure required to build, supply and maintain a WTE facility play a key role in the success of such a project.
The report further states the public’s perception of waste-to-energy technology in general. “Municipal jurisdiction usually controls the handling of MSW in a specific region, however some states have national policies that influence these regions,” it is cited in the report.
Another challenge that a country like South Africa faces is that statistics are not on our side. According to the research report, the potential for energy recovery is lower for developing countries than industrialised ones. “Globally, in 2003/4 there were 600 WTE facilities around the world, processing 130-million tons of MSW annually.” The report cites that many of these projects are located in countries that are severely limited in space, with dense populations producing anywhere from about 1kg to 2kg of MSW per person per day. “In places like Europe, landfilling of sorted combustible MSW is illegal and landfilling is taxed.”
Bredenhann says it is important to use scientific methods to collect, interpret and forecast waste composition and waste data before attempting to launch and operate a successful WTE project.
He says an important factor in ensuring that a WTE initiative is economically feasible is to be sensitive and flexible to the changes in the energy market. “It would be more profitable when for instance one could combine a WTE project with recycling projects that will also generate income.”
He says a range of technologies is available on the market and it is of essence to choose an integrated solution-driven mix of technologies to suit the needs of a specific town or metro.
Separating the good from the bad
According to Bredenhann, 90% of South Africa’s waste gets dumped into landfills. “With the limited space for development in cities like Johannesburg and Pretoria, this story could have a bad ending,” he says. He says a feasible solution to the problem would be to sort all the material into recyclable and non-recyclable waste before it gets dumped into a landfill. “This way one can minimise the amount of waste that is dumped into a landfill.”
He says that ideally only 5% of waste should end up in a landfill. “The remaining amount of waste could then be used for WTE projects and/or recycling projects.”
The research report stated that wet MSW, usually from recyclable material, negatively impacts the burning efficiency during the combustion process in a WTE project, which lowers the heating value of the MSW overall. “The moisture content of MSW is directly related to the level of wealth in a given region, with the more affluent households creating drier MSW than the less affluent, who mostly produce organic waste.”
According to the report, there is a difference in moisture content, density and lower heating value between a typical low-income country and a high-income country. “This shows that the heating value for high-income countries could be as much as twice as that of low-income countries.”
The report further states that MSW produced in developing countries is less suitable for WTE processing. “Developing countries also have lower MSW generation rates due to a general lower income per capita than these of the larger, industrialised countries like the United States.”
“Only about a third of the methane from the decomposing biomass material in municipal landfills is captured,” cites www.eartlife.org.za. “If all the bio-digestible waste was separated when it is received, all the resulting gas could be used, with compost as a by-product.”
A local perspective
According to www.earthlife.org.za, one form of waste-to-energy projects currently being considered by many municipalities in the country is to capture the gas released by rotting organic matter in landfills and use it to generate electricity.
The website states that the Department of Minerals and Energy recently released a draft document on the potential of landfill gas for power generation. In the document it is said that of the 453 landfill sites in South Africa, 53 could potentially be used to generate power.
Last year the member of the mayoral committee responsible for infrastructure services and environment, Councillor Roslynn Greeff, launched the City of Johannesburg’s first landfill gas-to-energy clean development mechanism project at the Robinson Deep Landfill Site.
According to www.joburg.org.za, the City of Johannesburg initiated the landfill gas-to-energy clean development mechanism (CDM) project in 2007. The main aim of the project is to mitigate the harmful greenhouse gases emitted from landfills.
The extraction and destruction of these gases has provided the city with an opportunity to receive revenue from the generation of emission reductions certificates through the CDM process and from the generation of electricity. It is anticipated that the renewable energy generated will be fed into the municipal grid, thus off-setting largely coal-derived electricity.
The website states that this project is being implemented in five of the city’s landfill sites, making it the largest landfill CDM project in South Africa so far. Approximately 19MW will be generated from the project. “Construction of the Robinson Deep Landfill Site started on 21 February 2011 and was completed on 25 July 2011. The site was handed over by the contractor, Fountain Civil Engineering (Pty) Ltd (FCE) to EnerG Systems, to the city on 26 July 2011,” it cites.
According the City of Johannesburg, the daily pumping of landfill gas at Robinson Deep happens at 1 400 cubic metres per hour and this will be increased over time. “The plant can reach an optimum pumping rate of 2 000 cubic metres per hour when it operates at full capacity,” it was stated in a press release.
In the press release it is said that to date the Robinson Deep LFG project has produced 10,322 verified emission reductions (VERs) during the months of June and July last year. “There are also plans to increase the flare output. The VERs will be converted into carbon emission reductions (CERs) in order to earn carbon credits.”
Waste-to-energy projects have been implemented with high success rates all over the world and could definitely be used to improve energy security in South Africa. It is almost inconceivable to think that the utilisation of waste could add to the quality of life and can even be a feasible solution to providing a reliable energy source for millions. It is time to change people’s perceptions to cultivate a greener future.
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