Eskom pours mercury into air
TWO of South Africa’s power stations – Lethabo and Matimba – were the highest mercury-emitting coal power stations in 2015.
“When comparing the amount of average mercury emitted per GWh of energy sent out, Matimba and Lethabo are the top two ‘mercury per GWh’ emitting stations, then followed by Kendal, Matla and Tutuka.”
This is according to a new study, Mercury Emissions from South Africa’s Coal-Fired Power Stations, written by two Eskom employees, which was published in the Clean Air journal in November last year.
The authors, Belinda Garnham and Kristy Langerman, calculated the amount of mercury emitted from each of Eskom’s coal fired power stations based on the amount of coal burnt and the mercury content in the coal.
They revealed that between 16.8 and 22.6 tons of mercury was emitted from Eskom’s coal-fired power stations in 2015.
Coal-fired electricity generation plants are the highest contributors to mercury emissions in South Africa.
In their paper, the authors described how mercury was a persistent and toxic substance that could be bio-accumulated in the food chain. “Even though mercury is present in trace amounts, exposure increases as it accumulates.”
Trace amounts of mercury can be found in coal, mostly combined with sulphur, and can be released into the atmosphere upon combustion.
The authors wrote how a major factor affecting the amount of mercury emitted into the atmosphere, was the type and efficiency of emission abatement equipment at a power station.
“Eskom employs particulate emission control technology at all its coal-fired power stations, and new power stations will also have sulphur dioxide abatement technology. A co-beneficial reduction of mercury emissions exists as a result of emission control technology.”
They also reported a slight decrease in mercury emissions from 2011 to 2015, a direct link to the quality of coal burnt since 2011, which has declined from an average of 17.9 tons in 2011 to an average of 16.8 tons in 2015.
“Total mercury emissions are expected to be reduced by between 6% and 13% over the next 10 years from the implementation of Eskom emission/retrofit plan.”
The authors noted how there was limited information on the status of mercury emissions in African countries “although mercury emissions in Africa are increasing due to the rapid economic development in these countries”.
South Africa signed the Minamata Convention on Mercury on October 2013; “however, there is no legislation regarding mercury at present”.
“South Africa, being the most industrialised country on the continent, also has limited information on levels of mercury in resources, mercury in products and mercury in emissions.
“It’s previously been estimated that emissions of mercury as a result of power generation account for 77% of the total mercury emitted in SA. This figure, unless mitigated, is unlikely to decrease significantly as coal is the main source of energy and the demand for base energy will increase with the increase in population.”