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The risks associated with the release of mercury and its compounds on people’s health and the environment is of great concern to stakeholders, in particular local communities and regulatory authorities. National or regional legislation (US, EU) are already in place, and work has started under the umbrella of the United National Environment Program (UNEP) to develop a global legally binding instrument to manage mercury emissions from different sectors.

The process to develop a global framework is organized under the Intergovernmental Negotiating Committee (INC). The goal is to complete the negotiations with a diplomatic conference at the end of 2013.

To support the negotiations track, the Global Mercury Partnership has been formed, which will deal mainly with dialogue and experience sharing in various industry sectors on the management of mercury and its compounds from different activities. This partnership process will feed information and data into the decision making process of the INC track.

The CSI supports the work carried out by UNEP and is co-chairing the cement partnership on mercury as agreed by the Partnership Advisory Group (PAG) of UNEP in November 2011. This overall mercury management process develops and shares knowledge on mercury baseline data, emissions factors, monitoring and control technologies and development of guidance material on best environmental practices.

For further information, please see the relevant UNEP webpage.

The CSI and CEMBUREAU, the European Cement Association, commissioned the University of Liège (ULg) in Belgium to provide an overall inventory of mercury emissions in the cement industry worldwide and, when appropriate, identify the best practices available to reduce such emissions.

CSI Recycling Concrete Full Report

Mercury in the Cement Industry




The full report is based on technical and scientific literature, on an exhaustive worldwide inventory of mercury emissions in the cement industry and on the analysis of case studies provided by cement companies which are members of the CSI.

Worldwide cement kiln mercury emissions data were collected through CEMBUREAU and the CSI member companies. The enquiry was launched in spring 2008 and data collection took place from summer 2008 until mid 2009. The enquiry was very general as the main objective was to collect as much data as possible. The questionnaire covered 2005, 2006 and 2007. 1681 emission values were obtained from 62 different countries from all continents, with 62 companies taking part. The main findings are:

Mercury enters in the cement manufacturing process as a trace element with the raw materials and the fuels. The mercury content of natural raw materials varies between individual raw material deposits and even within the same deposit. In fuels, the amount of mercury can vary in a similar way, depending on the fuel type and the fuel source. Depending on their origin, alternative raw materials and fuels may have a higher or a lower mercury content than the ordinary materials they replace.

Mass balance tests were conducted on several cement kilns and described in the literature. Moreover, CEMBUREAU and CSI members collected and provided several unpublished case studies. The information and data presented in this report and other studies demonstrate that mercury does not simply volatilize from the fuel and raw materials and directly leave the system through the stack. Rather, cement kiln systems have a significant inherent ability to control mercury stack emissions. The report and case studies largely confirm the experience and the key control factors for mercury abatement in cement kiln systems, as referenced in the available literature.

The key control factors and best environmental practices can be summarized as follow:

  • In most cases, the major contributors to total mercury input into the kiln system are the natural raw materials, and not the fuels.

  • Mercury input control is the most important measure for the responsible operation of a kiln. Best environmental practice is to conduct a careful selection and control of all substances entering the kiln in order to avoid too high a mercury input. A dedicated quality assurance system is recommended.

  • Selective mining may be an option in order to control and avoid mercury input peaks into the kiln system.

  • Mercury emissions are typically higher in kiln operations with the raw mill-off (“direct” operation) due to the missing adsorption capacity of the freshly ground particles in the raw mill.

  • Periodic purging (bleeding) of cement kiln dust from the system is an efficient way to control and reduce mercury emissions. Adsorption of mercury is favored due to the very high dust loadings present in the raw gas streams from preheater-precalciner kilns. This purging process is more efficient in the mill-off mode than in the mill-on mode due to the higher mercury concentrations in the dust. The efficiency of this measure depends, in part, on the quantity of dust removed from the system, and on the temperature prevailing in the air pollution control device.

  • Other techniques to reduce mercury air emissions are available in other industries such as waste incinerators and coal-fired power stations. Some, such as carbon adsorption, are well proven, whilst others are at laboratory or pilot stage. However, most of the test programs completed in those industries cannot be extrapolated to the cement industry. Therefore, those techniques cannot be considered as best environmental practice in the cement industry.

In 2016 the CSI released the Guidance for reducing and controlling emissions of mercury compounds in the cement industry. Member companies combined their experience and knowledge to develop this shared resource on this topic of utmost importance to the sector. The Guidance is an invaluable reference for engineers and technicians seeking information on mercury, its impacts and relevance to the cement sector and in particular the technologies and methodologies available for minimizing emissions during cement production.
mercury guidance cover
Guidance for reducing and controlling emissions of mercury compounds in the cement industry








 

The Stockholm Convention requires Parties to take measures to reduce or eliminate releases of persistent organic pollutants (POPs) from intentional production and use, from unintentional production and from stockpiles and wastes. The chemicals intentionally produced and currently assigned for elimination under the Stockholm Convention are the pesticides aldrin, chlordane, dieldrin, endrin, heptachlor, hexachlorobenzene (HCB), mirex and toxaphene, as well as the industrial chemical Polychlorinated Biphenyls (PCBs). 

Souselas Portugal

The Convention also seeks the continuing minimisation and, where feasible, elimination of the releases of unintentionally produced POPs such as the by-products from wet chemical and thermal processes, polychlorinated dibenzo-p-dioxins/-furans (PCDD/Fs) as well as HCB and PCBs. Concepts of Best Available Techniques and Best Environmental Practices to achieve such minimisation and reduction from all potential source categories will be further developed by the Conference of the Parties. Cement kilns co-processing hazardous waste are explicitly mentioned in the Stockholm Convention as an industrial source having the potential for comparatively high formation and release of these chemicals to the environment.

The cement industry takes any potential emission of POPs seriously, both because perceptions about these emissions have an impact on the industry's reputation, and because even small quantities of dioxin-like compounds can accumulate in the biosphere, with potentially long-term consequences. 

The objective of this study was to compile data on the status of POPs emissions from the cement industry, to share state of the art knowledge about PCDD/F formation mechanisms in cement production processes and to show how it's possible to control and minimise PCDD/F emissions from cement kilns utilising integrated process optimisation, so called primary measures.

In 2005, the CSI released the final version of this report on POPs emissions in the cement industry. The report was based on in depth scientific studies conducted with help from The Foundation for Scientific and Industrial Research (SINTEF) of Norway, a response to concerns from stakeholders regarding hazardous emissions from co-processing of waste materials in cement kilns. These studies concluded that emissions of organic compounds like dioxins and furans from well-operated dry cement kilns were of less than one part per billion in the air, and also ascertained that co-processing of waste in cement kilns did not lead to increased emissions of hazardous organic compounds. These findings have been backed up by similar studies done by the United States Environmental Protection Agency (EPA), and the United Kingdom's Environmental Agency. 

The CSI has comprehensively reviewed POPs emissions from cement plants, and worked closely with the Stockholm Convention (on POPs) Secretariat to help formulate reliable control measures as required under the convention.


Formation and Release of POPs in the Cement Industry
Formation and Release of POPs in the Cement Industry
Furans in Brazil: The Formation and Emission in Cement Kilns within the Framework of the Stockholm Convention