Eskom, South Africa’s state energy company, has been called the world’s most polluting energy company and the province of Mpumalanga, where most of the Eskom stations are located, the world’s largest air pollution hotspot. But are Eskom’s emissions really that high, and if so, why? Should South Africans be concerned about these emissions?
Eskom is by far the largest emitter of greenhouse gas pollutants sulfur dioxide and nitrogen oxides and carbon dioxide in South Africa due to its dependence on coal. Emissions of these gases from Eskom’s coal-fired power plants have been reduced slightly in the the last decade. South Africa, like other countries, has not significantly reduced emissions of air pollutants from the electricity sector despite the fact that the technologies exist to do so.
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Emissions from Eskom are detected in most of the northeastern region of South Africa via satellites. The large access point seen is due in part to the proximity of most of the country’s power plants in Mpumalanga. However, Eskom’s emissions are not the only source of pollution in this region. Ultimately, if South Africa wants to improve air quality and meet climate change goals, it must move away from coal.
What is thrown
Air pollution from coal-fired power plants is a by-product of burning coal. They are known as by-products of combustion.
The main component of the exhaust gases (called combustion gases) emitted by coal-fired power plants is nitrogen (N₂, 73% -76%), an inert gas that naturally constitutes 78% of the atmosphere. Other important components are oxygen (O₂, 6%) and water vapor (H₂O, 5% -8%). All three are normal components of the Earth’s atmosphere and are not toxic.
Carbon dioxide (CO₂) constitutes about 13% of combustion gases. Carbon dioxide is a greenhouse gas and is changing the weather.
Air pollutants make up a small percentage of total combustion gases: sulfur dioxide, 0.1%; nitrogen oxides, 0.05%; mercury and fly ash in trace amounts.
Eskom publicly reports its emissions. According to the most recent report from Eskom figures, around 1.6 million tons of sulfur dioxide, 804,000 tons of nitrogen oxides, 71 tons of particulates (ash) and 206.8 million tons of carbon dioxide are released annually in total from all its power plants .
Eskom’s sulfur dioxide emissions are now higher than those of the electricity sector in the us, porcelain and the European Union, but around 60% lower than the Indian power sector. China, in particular, has achieved dramatic reductions in sulfur dioxide emissions over the past two decades.
Emissions are not the same as what we breathe
Greenhouse gases remain in the atmosphere for a long time, so the amount that is emitted is closely related to concentrations in the atmosphere. However, when discussing the impact of any source on air pollution, it is important to distinguish between emissions and concentrations of environmental (outdoor) pollution.
Emissions are the release of pollutants from a source. Some, like those from power plants, are released higher into the atmosphere and are diluted before reaching the ground. Others, like vehicle emissions and veld fires, are emitted where we breathe.
The negative health impacts of air pollution are related to the amount we breathe – the environmental concentrations of pollution. In many areas, this is dominated by local sources that emit closer to the ground, while those that emit higher into the atmosphere contribute less pollution to a larger area.
The impact of what is thrown
By-products of combustion from Eskom power plants are emitted from tall, thin piles. Typically there are two, and it should not be confused with the steam emitted from shorter, occupying cooling towers. These piles are tall (ranging from 152 meters to 300 meters) so the feathers are diluted before reaching the ground, where pollutants can be inhaled and affect ecosystems.
But that only limits part of the damage. As carbon dioxide remains in the atmosphere for 300 to 1000 years, the impact on climate change is not affected by the height of the stacks. Carbon dioxide from South Africa’s coal-fired power plants accounts for around 43% of greenhouse gas emissions in and around South Africa 25% of greenhouse gas emissions from sub-Saharan Africa.
Sulfur dioxide and nitrogen oxides emitted can undergo chemical reactions in the atmosphere to form particles and ozone. These pollutants can remain in the atmosphere for days or weeks and therefore can travel long before rain removes them from the air or is deposited on surfaces (such as buildings, the ground, trees).
Exposure to air pollutants increases the incidence of diabetes, lung cancer, respiratory, cardiovascular and cardiopulmonary diseases and contributes to premature deaths. To protect health, environmental concentrations of sulfur dioxide, nitrogen dioxide, particulate matter and ozone are regulated in South Africa through the National ambient air quality standards. However, these levels are exceeded in many areas of South Africa, which means that people’s health is at risk. Eskom’s emissions contribute to these high concentrations, but they are not the only source of pollution.
Technology can play a role
Mature technologies can remove most of the pollution from the flue gas stream before it is released to the atmosphere. These are widely used worldwide.
Historically, Eskom’s focus has been on reducing particulate (ash) emissions. More than 99% of all ash is remote in all its power plants and is disposed of in large incineration facilities. These must be managed with care, generally by planting vegetation, to avoid the generation of windblown dust.
But Eskom has a long way to go to reduce the other pollutants. Few of its power plants have the technology to reduce emissions of sulfur dioxide and nitrogen oxides. The technology that extracts carbon dioxide from flue gas and stores it underground is not yet commercially available.
Minimum emission standards They were introduced in South Africa in 2010. These gave power plants 10 years to meet strict limits for sulfur dioxide, nitrogen oxides and particulate matter.
But this required the installation of new technology and by 2020 only one coal-fired power plant was fully compliant.
Lack of funds is the main reason Eskom has given for not modernizing power plants as needed. Long planning and installation times, long unit downtime, and additional water requirements are secondary considerations.
Large capital outlays for emissions reduction improvements were needed at the same time that Eskom was borrowing large sums of money to finance construction from the Medupi, Kusile and Ingula plants. And the national demand for electricity stagnant, limiting Eskom’s revenue growth.
The way to follow
Better air quality in South Africa can be achieved by reducing emissions in all sectors and decarbonizing the energy system. While Eskom power plants have the highest total emissions, there are many sources of air pollution in South Africa, most of which comes from the burning of fossil fuels.
Diversifying the energy mix towards cleaner fuels will have positive effects on air quality and will help South Africa meet the climate targets currently under discussion. at COP26.
Rebecca garland, Principal Investigator of the Climate and Air Quality Modeling Research Group, Council for Scientific and Industrial Research and Kristy langerman, Associate Professor, University of Johannesburg