|Friday, 23 September 2011 15:28|
Due to the weathering of volcanic rocks and the accumulation of mercury in ancient sediments, mined coal subsequently contains mercury.
Although small quantities of mercury may be emitted while coal is stored and handled, most mercury is released from the combustion stack after it is burned. The boilers operate at temperatures of 1100 ̊C and the mercury in the coal is vaporized and released as a gas. Some of the released mercury may cool down and condense as it passes through the boiler and the air pollution control devices. The amount of mercury in coal that is not emitted into the atmosphere during combustion is trapped in wastes such as bottom ash and recoverable fly ash.
Mercury emissions from Fossil fuel combustion for power and heating, amount to 45.6% of the Global Mercury Emissions and are the largest anthropogenic source of emissions globally.
Up to 95% of mercury releases from power plants can be reduced. This can be achieved by taking direct measures to reduce mercury emissions, by optimizing control systems for other pollutants, improving coal treatment and improving plant performance.
Relevant legislation and NGO policy work
In the EU
The EU adopted the Large Combustion Plants Directive (LCP) , which entered into force in 2001. The overall aim of the LCP Directive is to reduce emissions of acidifying pollutants, particles, and ozone precursors. Control of emissions from large combustion plants - those whose rated thermal input is equal to or greater than 50 MW - plays an important role in the Union's efforts to combat acidification, eutrophication and ground-level ozone as part of the overall strategy to reduce air pollution. The directive mainly addresses and sets emission limit values for NOx, SO2, and particulate matter. Through these measures, mercury releases are also expected to be reduced.
Furthermore, the Integrated Pollution Prevention and Control (IPPC) Directive (96/61/EC), has been in place since 1996 and also refers to the Cement production sector. The Commission has undertaken a 2 year review to examine how the legislation on industrial emissions could be improved. As a result, the Commission adopted on 21 December 2007 a Proposal for a Directive on industrial emissions recasting seven existing Directives (the IPPC Directive and six sectoral Directives) into a single legislative instrument. One of these six sectoral directives is the LCP directive. Following the co-decision process on this Proposal, the Directive on industrial emissions 2010/75/EU (IED) has been adopted on 24 November 2010 and published in the Official Journal on 17 December 2010. It has entered into force on 6 January 2011 and has to be transposed into national legislation by Member States by 7 January 2013. IPPC and now IED sets out the main principles for the permitting and control of installations based on an integrated approach and the application of best available techniques (BAT) which are the most effective techniques to achieve a high level of environmental protection, taking into account the costs and benefits. For more information on the directive please visit the EC website. The benchmarks or criteria on which BAT relies are described in the BAT Reference Documents (BREFs). The first Large Combustion Plant BREF was published in 2006. Its revision is expected to start in 2011.
Through the implementation of the IED, the role of the BREFs will be strengthened. After a BREF is completed, it should be subject to BAT conclusions that are adopted through a comitology decision (implementing act). The right of initiative however rests with the Commission. BAT conclusions contain parts of the BREF, their description, information on applicability, including BAT Associated Emission Levels (BATAELs) for different pollutants (meaning emission levels that can be achieved for a pollutant if the industry is implementing BAT) as well as associated consumption levels and monitoring. It may also include site remediation measures “where appropriate”. Within 4 years after publication of the comitology decision on the relevant BAT conclusions, local authorities should review and update all the permits to the respective industries in order to make sure the industrial activity operates according to the requirements set out in the BAT conclusions. The provision in the IED requires that Emission Limit Values (ELVs) for pollutants set out in the permit should not exceed the relevant BATAEL. However the permit writer may derogate in specific cases and set higher ELVs under certain conditions. An assessment needs to demonstrate that the application of the BATAEL would lead to disproportionate higher costs compared to the benefits due to the local conditions (technical characteristics of the plants, or geographical location or local environmental conditions). In any case no significant pollution may be caused and a high level of protection of the environment as a whole is achieved. Environmental Quality Standards also need to be respected. These derogations are subject to public participation and scrutiny by the public concerned, which includes NGOs.
At UNEP level , under the request of the Governing Council Decision in February 2009 (GC 25/5) Para29, a study was carried out , "The paragraph 29 study." A study on various mercury-emitting sources . The focused sectors in the study were coal combustion, cement manufacturing, non-ferrous metal production and waste incineration. The study summarizes and evaluates efficiencies and costs of potential measures to reduce mercury emissions to air from the mentioned sectors. It also presents a global atmospheric mercury emissions inventory and update and evaluation of trends in global mercury atmospheric emissions (1990-2005). (see also http://www.unep.org/hazardoussubstances/Mercury/MercuryPublications/ReportsPublications/tabid/3593/Default.aspx)
Under the ZMWG work similar projects have been funded to look at emissions from the above mentioned areas in the countries of focus- India, Russia, and China. The projects were carried out by the respective NGO representatives of these countries - Toxics Link (India), EcoAccord (Russia) and with the input from GVB (China).
Important work is also being carried out under the UNEP Global Mercury Partnership on Mercury Control from Coal combustion. Further relevant documents have been developed under these initiatives.
Several measures are also being taken in other parts of the world.
US federal regulation of coal fired power plants can be found here: http://www.epa.gov/hg/control_emissions/index.htm
A summary of state initiatives to control mercury from coal-fired power plants is also provided at: http://www.4cleanair.org/ click on “State Utility Mercury/Toxics Programs” . See also http://www.epa.gov/hg/regs.htm#regs
The ZMWG has been following this issue closely and has been giving respective feedback at the global mercury negotiations. See also the ZMWG fact sheet on Mercury Air Emissions and Continuous Emissions monitoring Systems (CEMS) (Jan 2011)