Impacts and control of coal-fired power station emissions in South Africa

PhD (Geography and Environmental Management), North-West University, Potchefstroom Campus, 2016

South Africa is a major role player in coal generated energy both regionally and globally. It is the main electrical power generator in Africa, and falls under the top ten coal producers and consumers in the world. The South African energy sector of which 85% to 94% is constituted by coal-fired power plants is one of the major emitters of criteria pollutants (Particulate Matter (PM), Nitrogen Oxides (NOx) and Sulphur Dioxide (SO2)) as well as Carbon Dioxide (CO2) emissions in the country. The South African electricity industry and air quality regulation thereof has undergone many changes over the past decade. The most prominent of these changes is the promulgation of the Listed Activities and Associated Minimum Emission Standards (MES) identified in terms of section 21 of the National Environmental Management Air Quality Act (NEM:AQA) that came into effect in 2010. The South African energy crisis, on the other hand, is placing enormous amounts of strain on the South African energy generating system and economy since the middle 2000’s. The MES stipulates that emissions are to be measured by means of Continuous Emissions Monitoring Systems (CEMS) instead of being calculated by means of a mass balance methodology as has been done traditionally. The paper “A critical comparison of gaseous coal-fired large boiler emission estimation in South Africa” (Chapter3) compares the emissions estimation techniques in terms of cost, ease of operation/calculation, data quality and practicality in the South African context. It was found that calculation techniques are by far cheaper and simpler to implement than CEMS, which need expertly trained operators and are replaced every 10-15 years. The data quality of both methods is currently similar in South Africa. If operated properly, and if proper quality assurance/quality control measures are in place, CEMS can obtain emissions measurements with lower uncertainties than that of calculation methods. However, there is still a knowledge-gap in operating these systems in our country and the data availability requirements of the legislation cannot currently be achieved. Calculations are simple and cost effective techniques that can be used as a backup to CEMS measurements and it is believed that this technique should be used in conjunction with CEMS until such time as the quality of South African CEMS measurements is proven. The paper entitled “The impact of the South African energy crisis on emissions” (Chapter 4) investigates the effect the South African energy crisis had (and still has) on emissions from various sources, including power stations. Since 2007, the start of the South African energy crisis, the existing coal-fired power station fleet has been under enormous strain. During this period, maintenance was brought to a halt and this caused the deterioration of the overall condition of the fleet. Emissions abatement technology used at existing power stations also suffered from lowered maintenance and as a result the removal efficiencies of these systems decreased. This led to an overall increase in coal-fired power station emissions from the majority of criteria emissions (especially emissions of pollutants that are abated) and emissions of CO2. This means that, if the energy crisis persists, emissions from power stations may be much higher than expected and this should be taken in account in future planning. The paper “A perspective of South African coal-fired power station emissions” (Chapter 5) predicts future coal-fired power station emissions for a range of different scenarios based on pressures facing the energy generating industry at present, and possibly in the future. The scenarios differ in terms of different retrofit rates of power stations with emissions abatement technologies and different energy demand outlooks. The worst case scenario assumes a relatively high energy demand outlook and further assumes that the energy crisis persists over the next 15 years whereas the best case scenario assumes lower energy demand and abatement retrofits at some stations. Worst case emissions are roughly double that of best case emissions during 2030 for PM, SO2 and NOx. Another important finding is that it is unlikely that the South African climate commitment target of 280 Mt CO2 in 2030 will be made, unless energy demand dramatically decreases in the future. The listed activities and associated MES identified in terms of section 21 of the NEM:AQA set blanket Minimum Emission Standards for all large boilers (>100 MW) including coal-fired power stations. Tension sometimes arise between the ambient air quality standards and MES, as power stations are expected to comply with MES irrespective of whether ambient air quality standards in their vicinity are met and their potential impact on human health. This may lead to the unnecessary instalment of costly abatement technology, the funding which may have been applied with greater effect to health exposure reduction elsewhere. The paper “Emissions management and health exposure: Should all power stations be treated equal?” compares the potential health exposure to 15 power stations within the Highveld of South Africa in order to propose an emissions management strategy that is optimized for reduced health exposure and cost. It was found that the health exposure to power station emissions varies greatly from station to station and from pollutant to pollutant Potential human health exposure in the form of intake fractions estimated in this investigation differed up to two orders of magnitude for SO2, NOx and primary PM10. Secondary PM emissions differed less, due to the fact that these pollutants form away from the source and are therefore able to disperse more evenly in the atmosphere. Based on the findings of this study the author believe that a more logical solution to the effective management of power station emissions, with optimal human health and reduced cost as end goal, may be to address power station emissions on an individual power station basis.

Doctoral