Tag Archives: control technology

Co-Benefits of Mercury Emissions Reduction

Finding the silver lining in reducing quicksilver

By: Rebecca Saari

As a PhD Candidate researching air pollution, I have enjoyed following the treaty discussions, particularly those focusing on emissions and releases. At MIT, I study the many social and environmental gains from reducing air pollution. Often, targeting reductions of a single pollutant – like mercury – can simultaneously serve to reduce other pollutants as a side-benefit. Finding and quantifying such “co-benefits” is my passion. (My other passions include skiing and chocolate, so it does not hurt that the negotiations are in Switzerland.)

Reducing mercury emissions

Nanticoke, coal-fired thermal generating station in Ontario, Canada, with a total capacity of 3,920 MW, was once the largest coal plant in North America. It will no longer burn coal, by the end of 2013 (Photo by Ontario Power Generation).

If the treaty creates new action to reduce mercury emissions, it can realize gains that go far beyond the direct impacts of mercury alone. Controlling mercury from coal-fired combustion, the second-largest air emissions source, can be achieved with measures that also control other pollutants. In particular, reducing mercury emissions to air can also reduce emissions of particulate matter, sulfur dioxide and nitrogen oxides.

All of these pollutants have significant human health impacts. Estimates of global worldwide deaths due to fine particulate matter exceed 1 million per year. Beijing is currently experiencing extreme levels of fine particulate matter. Countries can use the opportunity presented by this treaty to make progress towards multiple goals in protecting human health and the environment.

Reducing mercury emissions from coal would go a long way towards diminishing the global transport of mercury pollution. Nearly one quarter of all mercury emissions to air arise from the combustion of coal in utility, industrial, and residential boilers.

Many ways to reduce mercury and other pollutants

There are numerous ways to address mercury emissions, which have varying co-benefits.
There are numerous ways to address mercury emissions, which have various co-benefits.

There are many ways to reduce mercury emissions from coal across the entire combustion process, from start to finish, including pre-treating coal, improving process efficiency, and using post-combustion technologies.

Before coal is burned, several actions can reduce mercury, sulfur compounds, and particulate emissions. There are several different types of coal, and they vary in the amount of pollutants they contain. Coal switching and coal blending can allow mercury emissions to be captured more easily. This is a low-tech, potentially low-cost form of mercury reduction. Coal can also be pre-treated through a variety of processes, including washing, beneficiation, and the application of additives. Depending on the type of cleaning and variety of coal, washing alone can remove about 10-80% of the mercury content in coal before combustion takes place.

We can also improve the efficiency of coal plants through operations and maintenance (O&M) measures that lower the emissions intensity of coal-related pollutants including mercury and greenhouse gases, and potentially lead to more sustainable and cost-effective use of fossil fuels. Various O&M measures are effective options. Typically, these approaches target improved combustion efficiency, improved flue-gas ventilation, and reduced leakage and fouling.

Once coal combustion is complete, mercury can be captured using conventional methods designed for other pollutants. Specifically, wet sulfur scrubbers (a.k.a. wet flue gas desulfurization), particulate capture (including fabric filters, electrostatic precipitators), and NOx controls (i.e. selective catalytic reduction) can aid in mercury removal. Depending on the type of coal and configuration of equipment, more than 90% reduction of mercury can be achieved. For additional mercury removal, mercury-specific sorbent injection can be added to the process.

Looking to the future, multi-pollutant control technologies, which aim to reduce key pollutants simultaneously, may gain in popularity. Several systems already exist, at various stages of development, demonstration and commercialization. The mercury treaty has the potential to sow the seeds for broad protection of human health and the environment, beyond the gains due to mercury alone.

Interested in learning more? Three great resources are the UNEP’s “Process Optimization Guidance”, the International Energy Agency Clean Coal Centre and Pacyna et al. There is also an interactive companion to UNEP POG called iPOG, a tool you can use to learn about  options, and estimate your facility’s mercury reduction potential.

Existing Domestic Mercury Regulations


by Leah Stokes and Amanda Giang

Many countries have existing regulations on mercury, whether on emissions from coal plants or on the use of mercury in products and processes. Here is a short summary of key mercury regulations in some of the world’s largest emitters: the US, the European Union (EU), China, India, and Canada.

United States (US)

Emissions and Releases: In the US, mercury is considered a Hazardous Air Pollutant under the Clean Air Act. During the 1990s, the Act was used to motivate limits on mercury emissions from medical and waste incinerators, leading to a 90% reduction in emissions from these sources.

In addition, the 1990 Clean Air Act Amendments aimed to include mercury emissions from coal plants, but these regulations took two decades to finalize. In December of 2011, the EPA began to regulate coal plants, the largest source of US air emissions, through intensity standards. Under this regulation, mercury emissions were limited for each unit of energy generated. This rule, the Mercury and Air Toxics Standards (MATS), is projected to reduce coal plant emissions by 90% by 2016.

In the US, direct and indirect releases of mercury into surface water are estimated to be 1.56 tonnes per year.

Products and Processes: In the past, the US used mercury in products and processes primarily for batteries, chlor-alkali production, and paint. According to the EPA, mercury use has been eliminated in most batteries and paint, but it is still used in electrical and measuring devices (e.g., thermometers). The US has also reduced its reliance on mercury in chlor-alkali production, but there are still some plants that use mercury in this process.

Most action on products and processes in the US has occurred at the state and local level. Many states have passed laws that restrict or ban mercury and require labeling of mercury-containing products. Ensuring that mercury containing products are recycled and do not end up in the waste-stream remains a key challenge.

Trade: The US banned mercury exports as of January 1, 2013.

Europe Union (EU)

Emissions and Releases: In the EU, the Integrated Pollution Prevention and Control Directive (2008/1/EC) regulates emissions from the metals, cement, and chemical industries and coal plants larger than 50MW. This regulation requires the use of best available techniques, but does not set specific emissions limits for mercury. Specific target values for ambient mercury concentrations may be established under Directive 2004/107/EC, which addresses other heavy metals as well.

In the EU, mercury releases from a single source of more than 1 kg per year to water and/or land must be reported.

Products and Processes: The EU prohibits or strictly controls mercury in the following products: batteries; electrical and electronic equipment; pesticides and biocides; cosmetics; wood preservatives; textile treatment agents; anti-fouling agents for boat hulls; and switches in vehicles. Mercury is being phased out of the chlor-alkali production process as well. For more information, see the EU’s Mercury Strategy FAQs.


Emissions and Releases: In 2011, China put out a national emission standard for mercury from coal plants and lead, zinc, and other metal production. The standard, which came into force in 2012, with full implementation to be achieved by 2015, limits mercury concentrations from coal plants to 0.03 mg/m3. The standard for the lead and zinc industries is 0.03 mg/L, and the standard for the copper, nickel, and cobalt industries is 0.05 mg/L.

China is also moving on mercury releases to water. Mercury discharge limits for urban sewage treatment plants are 0.001 mg/L.

Artisanal and Small-Scale Gold Mining (ASGM:) China has banned the use of mercury in ASGM [doc]. However, given that ASGM in China occurs in the informal sector, as is the case globally, this ban may be difficult to enforce.


Products and processes: India has used a voluntary public-private partnership to successfully reduce mercury use in chlor-alkali production. Between 2001 and 2009, mercury used in chlor-alkali production declined by two-thirds with emissions to the environment reduced by 95%.


Emissions and Releases: Canada has a comprehensive risk management strategy for mercury. Canada sets provincial caps on mercury emissions from electrical power generation, metal smelters, cement producers, and waste incinerators. Canada also has a comprehensive inventory of emissions and releases, which indicates that in 2010 total releases to water and land were 259 kg and 99 kg respectively; these releases were much lower than emissions to air, which were 5,222 kg or 5.2 tonnes.

Products and processes: In 2011, Canada began to regulate the domestic manufacture, import, and sale of mercury-containing products including toys, food and health products, pesticides, lamps, and dental amalgam. This regulation is estimated to reduce the amount of mercury in products by 4.5 tonnes each year.

Other countries have emissions regulations as well. For example, Chile has introduced mercury-specific emissions limits of 0.1 mg/m3. In addition, given the stringent regulations for particulate matter (30 mg/m3), further mercury co-benefits are expected.

If you know of another country with emission regulations for mercury, please add a comment to the page or let us know by emailing us at INC5@mit.edu.

Issue Overview: Mercury Emissions and Releases

by Leah Stokes and Rebecca Saari

Each year, humans mobilize around 2000 tonnes of mercury, with about 90% emitted to the air and 10% released to land and water. Since releasing mercury leads to environmental and human health impacts, addressing emissions and releases needs to be a central part of the global mercury treaty.

The draft text of the treaty, developed during the INC4 in Uruguay, distinguishes between emissions to the atmosphere and releases to land and water. However, the extent of controls on anthropogenic emissions remains to be seen, and it is possible that releases will be excluded altogether.


UNEP’s 2013 estimation of  2010 emissions from each global region. These estimations significantly changed since the 2008 reports, where East and Southeast Asia was estimated to contribute two-thirds of global emissions. These changes likely reflect a reduction in the estimation of mercury from coal power plants in Asia and an increase in the estimation of mercury from ASGM in Sub-Saharan Africa and South America.

Currently, almost 40% of mercury emissions come from East and Southeast Asia. Many developed countries have significant regulations on emissions, and the treaty is in part an effort to have all countries adopt standards. Yet most historic emissions came from the developed world. As is the case with climate change negotiations, this dynamic raises equity issues – mainly, who should pay: past emitters or current emitters?

Unlike carbon dioxide, however, mercury is toxic with acute health and environmental impacts, and its release is not tightly coupled with countries’ GDP. For this reason, all countries should be interested in reducing their mercury emissions and releases.

UNEP's 2013 report, "Time to Act" recently updated the proportion of emissions from each source. ASGM is now the largest estimated source of emissions, with coal plants in second place.

UNEP’s 2013 report, “Time to Act” recently updated the proportion of emissions from each source in 2010. ASGM is now the largest estimated source of emissions, with coal plants in second place.

About one-quarter of all global mercury emissions to air come from coal-fired combustion, including power plants and industrial boilers. This suggests an important aim for the treaty is reducing mercury emissions from coal-fired power and heating. There are many ways to achieve this, including pre-treatment of coal and various post-combustion technologies. These options also reduce co-emissions of other harmful air pollutants, and conventional post-combustion treatment can be enhanced to remove 80-90% of mercury emissions. Mercury-specific post-combustion control, which can achieve 90% mercury removal, is also available.

With a variety of emissions control options available, and significant variation in the mercury content of coal, the Chair and delegates are challenged to set appropriate goals and measures. When asked, most countries that currently regulate mercury responded that they employ emissions limits, or limits to the amount of mercury exiting a stack (flue gas concentrations).

Thus far, proposed flue gas limits range from 0.01 to 0.2 mg/m3. For reference, 0.05 mg/mg3 is one of the highest values measured at a series of US plants with limited pollution control through a fabric filter and a low-NOx boiler. In other words, a standard set as high as 0.2 mg/m3 could imply almost no control technology at all (See document: UNEP(DTIE)/Hg/INC.5/4 for more details). Ultimately, the level of control technology required will dramatically affect the treaty’s effectiveness.

While coal-related emissions present a clear priority, other mercury emissions are challenging to address, since they comes from a wide variety of sources, including: gold, cement and metal production, the chlor-alkali industry, waste incineration and dental amalgams. The Chair’s most recent updates also highlighted mining tailings, and sewage and wastewater treatment plants as potential sources. Over one-third of all emissions are from artisanal and small-scale gold mining (ASGM), which is addressed in a separate part of the treaty. Decisions on ASGM will dramatically affect global emissions, given that the UNEP 2013 report recently named it the largest source of emissions.

This week, countries have many decisions to make on mercury emissions and releases. Which sources should be controlled—existing or new plants, and from which industries? For examples, it is currently unclear whether the oil and gas sector will be included as a source.

Should small sources be exempted from requirements to inventory and reduce their emissions, and if so, what would the threshold be for a “small” source? Potential thresholds for required controls are listed in the Chair’s documents. For example, coal-fired power plants smaller than 50 MW could be exempted from mercury control technology. For context, 20% of all US coal units are 50 MW or smaller, meaning that this threshold could exempt a significant proportion of plants.

What should the goal be – should the treaty set reduction goals, emission limits, or require best available techniques? As the discussion about flue gas concentrations implies, these standards will have significant consequences. And finally, how flexible should the requirements be—should countries have to commit to specific standards, or can they develop flexible national plans and report at a later date?

The draft text reflects many of these debates. Article 10, which addresses atmospheric emissions, has two options: one, which would require goals, best available techniques or emissions limits; the other, which would require national plans. These issues and many more will need to be decided in the coming week. Decisions on atmospheric emissions and releases to land and water are essential to shaping the treaty’s ultimate environmental and health impacts.