Editorial - VGB PowerTech Journal 10/2016

The VGB „Hg^cap(ture)“ initiative
Further reduction in mercury emissions from coal-fired power plants

The use of fossil fuels in electricity and heat generation, and especially hard coal and lignite, will continue to make an important contribution to a safe and competitive energy supply system and to industry in Europe. Also with a view to the technical challenges of the energy transition, conventional power plants continue to be indispensable as a partner of the renewables.

The power plant operators are conscious of their responsibility to use the best available techniques (BAT) to reduce emissions at their plants. This also applies to the capture of mercury which is released from the coal during combustion.

Mercury gets into the environment as a result of human activity and in natural processes. It is estimated (UNEP, 2013) that in 2010 around 1,960 metric tons of mercury from anthropogenic sources was released into the atmosphere, and 380 metric tons into bodies of water. This corresponds to around 30 % of the total mercury emissions. The remaining 70 % comes from natural processes. Among the anthropogenic sources, gold mining is the largest source of emissions worldwide, with a share of approx. 42 %. The second largest source of emissions is coal-fired power plants, at around 24 %, although mercury only appears in trace form in hard coal and lignite. The quantity is attributable to the large amount of coal used worldwide for power generation.

The largest sources of mercury emissions are East and South-east Asia, followed by Africa and South America. With a share of approx. 4.5 % Europe (EU-28) is in the lower range of global emitters. A further emission reduction in Germany with a national total emission of approx. 0.54 % of global emissions has no significant effect on the global emissions.

The levels of mercury in the air in Germany are 1 to 2 nanogrammes per cubic metre, which is 2 to 4 % of the WHO air quality standard of 50 nanogrammes per cubic metre and also significantly lower than the national German guide value. Mercury levels in drinking water and foodstuffs are also below the limits. There is therefore no acute hazard to health resulting from the current mercury emissions in Germany.

Nevertheless, at present, mercury emissions from coal-fired power generation are increasingly becoming the subject of debate by politicians and experts in the field, especially in Germany. The discussions are also being fuelled by several studies and questions in Parliament.

In the political debate, the opinion has repeatedly been expressed that there is already an “advanced state of the art” which would allow the limits for emissions of mercury through the air to be reduced to levels below 1 microgramme per standard cubic metre flue gas, and those for emissions through water to levels below 1 microgramme per litre. These levels correspond to the lowest edge of emission bandwidths identified in the course of revising the European BREF-LCP (BAT reference documents – Large combustion plants, Final Draft, June 2016). Whether and to what extent these levels can be achieved with specific mercury reduction technologies is highly controversial. There are considerable doubts¹⁾ in professional circles, especially as to the representativeness of the reference plants used in the derivation of these figures. In the view of the industry, the emission levels which can be achieved with the best available techniques are significantly higher.

Notwithstanding this, VGB PowerTech and its member companies have already been conducting research into the physical and chemical behaviour of mercury in the individual stages of the power plant process for several years in a large number of projects, and searching for opportunities and new technical methods for improved mercury separation. Since the issues involved with mercury are complex, the research projects and development work are time-consuming, and, especially with regard to their design for specific plant, not yet complete. Suitable technologies, with trials and validation, design and approval planning and implementation on an industrial scale will not be available in the near future. Furthermore, continuous emission measurement systems are of decisive importance in the context of future limits. No suitable emission measurement technology for emissions in a very low concentration is currently available. The measuring uncertainties are in the same order of magnitude as the future limits. There is a need for development in this respect.

With the aim of putting the discussion on a sound scientific footing and creating a valid set of data, the VGB PowerTech and companies involved launched the “Hg^cap(ture)” initiative to ensure an exchange of knowledge and experience among the participants themselves and with scientists and politicians. At the same time, the provision of information on this work to the public is being intensified.

VGB PowerTech and the companies concerned are also working towards an objectification of the public debate on mercury emissions from industry. With regard to the further development of the legal conditions, the companies and VGB PowerTech demand an appropriate stipulation of limits on the basis of the European requirements, and a reasonable period for the establishment of suitable and efficient processes.

As a dialogue initiative, “Hg^cap(ture)” provides all stakeholders and interested parties with a suitable and up-to-date platform for profes-sional discussions and the planning of productive work.

The Position Paper “Hg^cap(ture)” and the related Working Paper are available for download.

¹⁾Refer.: Prof. Dr. Alfons Kather, “Expert opinion on BAT-associated emission levels (BAT-AELs) for mercury emissions to air from existing lignite-fired power plants with pulverised combustion (PC) boilers in the LCP BREF review process”, Hamburg 2016.