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The Minamata Convention on Mercury (2013, hereinafter called “The Convention”) entered into force on August 16, 2017. As of February 1, 2018, 88 countries and regions, including Japan, ratified the Convention, which aims to protect human health and the environment from anthropogenic emissions and releases of elemental mercury and mercury compounds (hereinafter called “mercury”). The entry into force of the Convention, therefore, is a historic step for the international community in tackling mercury pollution in a concerted manner. As the country that experienced Minamata disease, Japan is committed to fulfilling its responsibility under the Convention.

To achieve its objective, the Convention stipulates a number of measures to reduce anthropogenic emissions and releases of mercury. Among the provisions, Article 8 of the Convention requires Parties to control and, where feasible, reduce total mercury emissions to the atmosphere by, for example, setting emission limit values (ELVs). In response to this requirement, Japan amended the Air Pollution Control Law (1967, hereinafter called “APCL”), which is the fundamental basis for protecting the atmosphere in Japan. Then, based on the amended APCL, Japan established ELVs for mercury from the point sources listed in the Convention. A series of considerations on setting ELVs was given by the Central Environment Council (2016), which is the advisory body to the Ministry of the Environment, Government of Japan (MOEJ).

This feature article describes Japan’s ELVs on mercury in detail, focusing on the approach and rationale. The article consists of six chapters. Following the introduction section, the second chapter gives a summary of the APCL and its amendment to involve regulation of mercury emissions. The third chapter throws light on the concentration of total mercury in fuels and materials as well as that in flue gas. These data formed the basis for setting ELVs. The fourth chapter illustrates the ELVs for mercury from the targeted sources, giving an explanation on the approach and rationale. The fifth chapter provides future perspectives, followed by the last chapter, conclusions.

In Japan, the APCL is the central pillar for protecting human health and the ecosystem from air pollution. The APCL was established in 1967 to tackle serious air pollution during a period of high economic growth in Japan and has been amended several times. It controls emissions of air pollutants, such as sulfur oxides and nitrogen oxides, by using regulatory measures, including setting ELVs on stationary and mobile sources and developing total emission control programs for specific areas. The APCL has contributed significantly to improving air quality in Japan.

In regard to ratifying an international treaty in Japan, domestic laws and regulations must be prepared to comply with the requirements of the treaty. Accordingly, amendment of the APCL was discussed to fulfill the stipulations under the Convention. Article 8 of the Convention requires Parties to use the best available techniques (BATs) and best environmental practices (BEPs) in order to control and, where feasible, reduce emissions for new sources by, for example, setting ELVs that are consistent with the application of BATs. For existing sources, the Article stipulates that Parties shall implement one or more of the following measures: a quantified goal, ELVs, use of BATs and BEPs, a multi-pollutant strategy and alternative measures. The argument in the discussion was how to reflect the requirements of the Convention in the amendments to the APCL.

In this regard, the mercury concentrations in the atmosphere were checked. The MOEJ monitors hazardous substances, including mercury, in the atmosphere on an annual basis at over 200 nationwide sites and releases the results. Fig. 1 shows the trend of the mercury concentrations in the atmosphere based on the latest MOEJ release (2017).

Fig. 1. 
Trend of total mercury concentrations in the atmosphere.

In Japan, the guiding criterion of atmospheric mercury concentrations is set at 40 ng/m³ (yearly average) from the viewpoint of minimizing environmental risks to human health. While mercury had not been regulated under the APCL and other laws, the concentrations of mercury in the atmosphere have been below this criterion since it was established in Fiscal Year (FY) 2003 (from April 1, 2003 to March 31, 2004). In FY 2015, the average and maximum concentrations of atmospheric mercury monitored at 262 sites were 1.9 and 3.7 ng/m³.

Hence, the amendment was drafted to regulate mercury emissions from flue gas with the aim of reducing global mercury emissions rather than avoiding direct risks to human health by inhalation. In line with this policy approach, clauses for the regulation of mercury in the APCL were drafted separately from others prescribing control of traditional air pollutants. As a countermeasure to reduce mercury emissions, establishment of ELVs for both new and existing sources were proposed.

The next question was which sources should be regulated under the amended APCL. The Convention lists the following point sources that are targeted: coal-fired power plants, coal-fired industrial boilers, smelting and roasting processes used in the production of nonferrous metals (copper, zinc, lead, industrial gold), waste incineration facilities, and cement clinker production facilities. Fig. 2 illustrates mercury emissions by source category in Japan in FY2014. The total emissions are 17 tons per year. The largest source category is that of the cement clinker production facilities (5.5 tons/year), followed by waste incineration facilities (5.4 tons/year). Artisanal and small-scale gold mining and processing, the largest emission source at the global level, does not exist in Japan. The sum of the emissions from the source categories listed in the Convention accounts for 81% of the total annual emissions. Accordingly, these categories were proposed to be targeted.

Fig. 2. 
Mercury emissions by source category in Japan (FY2014).

As shown in Fig. 2, iron and steel production facilities are the third-largest source category in Japan, while they are not listed in the Convention. Therefore, the proposed amendment of the APCL designated these facilities as “facilities subject to mercury emission control.” This designation urges operators of these facilities to control their emissions by, for example, setting voluntary ELVs.

After a series of discussions on the above points, the amendment of the APCL was finally approved by the National Diet in June 2015. By this amendment, a legal framework to control mercury emissions was created.

Following the amendment of the APCL, the MOEJ started work on setting ELVs for mercury emissions from the targeted sources. To set the ELVs, extensive data were collected and analyzed, including the mercury content in fuels and materials as well as that in the flue gas emitted from the targeted sources. This chapter throws light on the data, which are compiled in the report of the Central Environmental Council (2016).

This chapter illustrates the ELVs for mercury emissions from the targeted source categories. It has been assumed that the regulation aims at controlling mercury emissions under normal operating conditions, while the emissions vary owing to the mercury content in fuels and materials. Based on this assumption, the ELVs have been established, taking into consideration the following three points. The first point is the present state of mercury emissions from the source categories as well as the mercury content in the fuels and materials, which are described in the previous chapter. The second point is the use of the best available techniques (BATs) and best environmental practices (BEPs) to control and reduce mercury emissions, in accordance with paragraph 4 of Article 8 in the Convention. For this purpose, the draft guidance on BATs/BEPs (UNEP, 2015) has been used as a reference. The third point is consideration of the ELVs or equivalent standards used to control mercury emissions in other countries. For instance, the United States of America and the European Union have established or proposed their ELVs (for example USA Federal Register (2015) and European Commission (2013)). The present state of mercury emissions in Japan was compared to those values. It should be noted that the values of standards differ owing to several factors including the targeted duration (e.g., daily average or yearly average) and the monitoring method.

ELVs have been established separately for new and existing sources, in line with the Convention. New sources can install the latest BATs economically, leading to stricter ELVs than existing sources. However, existing sources are regarded as new ones when the sources are modified by more than 50% of their scale. Facilities for multiple purposes (e.g., coal-fired boilers to incinerate waste as a secondary fuel) are classified according to their main purpose.

Table 3 shows the ELVs for the targeted source categories in connection with the targeted scale and assumed BATs. Operators of the facilities are obliged to control mercury emissions below the ELVs applied. The regulation is to be put in place on April 1, 2018.

Paragraph 2(b) of Article 8 in the Convention allows Parties to establish criteria to identify the sources covered within a source category so long as those criteria for any category include at least 75% of the emissions from the category. In Japan, the sources under the mercury control regulation are already covered by the APCL or other legislation. To identify the targeted capacity of sources for mercury regulation, the same criteria as those for controlling traditional air pollutants are applied. It is estimated that those criteria for each category include more than 98% of the emissions from the category. Using the same criteria will reduce administrative costs and ease the burden on operators.

The unit for an ELV is expressed as micrograms of mercury per cubic meters under standard condition (273 K, 1 atm) or μg/Nm³. As in the MOEJ method described in the previous chapter, oxygen corrections are applied to measured values of mercury emissions from coal-fired boilers, waste incineration facilities and cement clinker production facilities.

Coal-fired power plants and coal-fired industrial boilers are classified into one category of “coal-fired boilers.” The ELVs of these facilities are lower than those of others because they are equipped with air pollution control systems that remove not only traditional air pollutants but also mercury from the flue gas. Higher ELVs have been established for small-scale coal-fired boilers with secondary fuels, for which the hourly heat input is below 100,000 L_foe, owing to variable mercury content in the fuels. While integrated coal-gasification combined cycle (IGCC) plants are included in coalfired power plants, there is only one such plant in operation in Japan, providing few data on its mercury emissions. Accordingly, ELVs for IGCC plants have been regarded as one of the issues to be considered in the future.

In the category of smelting and roasting processes used in the production of non-ferrous metals, separate ELVs have been established for primary and secondary smelting. The ELVs for the former have been established lower than those for the latter because of the low mercury content in materials fed into the process. In primary smelting, ELVs for the production of copper and industrial gold have been established lower than those of lead and zinc, reflecting the difference in mercury emissions from the flue gas. In secondary smelting, ELVs for the production of copper, lead and zinc have been established higher than those for industrial gold. The best available techniques for primary and secondary smelting have been assumed corresponding to the level of mercury impurities in the input materials.

Among waste incineration facilities, there is no considerable difference in mercury emissions from industrial waste, municipal waste and sewage sludge incinerators. Hence, the same ELVs have been established for those incinerators. However, different ELVs have been established for waste incinerators that burn industrial waste (or recyclable resources) with high mercury impurities, for example mercury recovery facilities, because of the peculiarity of the sources.

With regard to cement clinker production facilities, the BATs for new facilities have assumed multiple techniques in the draft guidance on BATs/BEPs. Those techniques include careful selection and control of raw materials and fuels, dust shuttling and collecting the dust instead of returning it to the raw feed, and installation of air pollution control devices such as wet scrubbers. The BATs for existing facilities are the selection of materials and fuels with low mercury content. Still, there are cases where facilities have no option but to use local limestone deposits with high mercury content. In those cases, 140 μg/Nm³ is used as the ELV for existing facilities instead of 80 μg/Nm³.

Operators of the targeted sources are required to periodically monitor gaseous and particle-bound mercury emissions in the flue gas based on the MOEJ method. A sample of the flue gas is collected manually. The required frequency of monitoring for a facility operating throughout the year is three times per year when the flue gas volume is equal to or greater than 40,000 Nm³/hr and twice per year when it is below 40,000 Nm³/hr. The procedure to verify compliance with the ELVs is unique. If the monitored value is over the ELV applied, operators are forced to additionally monitor mercury emissions three times or more within 30 days. Out of the four or more monitored values in total, the maximum and minimum values are removed, and the average of the remainder is calculated. Then, compliance is verified if this average is below the applied ELV. If the average is over the ELV applied, local authorities can urge the operators to improve their operation.

With the aim of implementing the Convention, Japan has introduced a regulation to reduce mercury emissions. This is a history-making step in the history of the APCL. As the regulation is brand-new, it is important to review progress of the implementation and improve the regulation if necessary. From such future perspectives, the following four points are essential.

First, it should be recognized that the aim of the Convention is to reduce the total amount of mercury emitted and released to the environment. Therefore, it is less meaningful that mercury removed from the flue gas merely shifts to other environmental media such as water and soil. Hence, it is necessary to keep an eye on the material flow of mercury in Japan and check the amount of mercury moving to the environment. If mercury reduction is not achieved, additional measures should be considered.

Second, it is essential to follow the state of compliance with this new regulation. If compliance is not ensured as a whole, it is critical to analyze the cause and consider improvements. In particular, Japan is advancing to a circular economy by recycling and reusing waste. Specifically, secondary smelting and cement clinker production facilities use considerable amounts of recyclable resources with mercury impurities. Accordingly, achievement of both a reduction in mercury emissions and promotion of a circular economy should be pursued.

Third, it is indispensable to review the ELVs themselves. The ELVs have been established based on assumed BATs, which will continuously evolve. Reflection of the evolution into ELVs will be desirable. Furthermore, addition of the IGCC to the targeted sources will be considered if sufficient data on its mercury emissions are obtained.

Lastly, the measurement and monitoring method should be reviewed as well, taking into consideration the progress of the monitoring methodologies and the burden on the operators.

To implement the stipulations of the Convention, Japan amended the APCL and has introduced a new regulation to reduce mercury emissions from the targeted sources. This regulation requires operators to comply with the ELVs for mercury emissions. The ELVs have been established based on the assumed BATs, taking into consideration the mercury content in fuels and materials and current mercury emissions from the sources.

Mercury content in recyclable resources and waste vary widely because they include mercury as impurities. This variation affects the mercury emissions from the sources that use those resources, including secondary smelting processes, waste incinerators and cement clinker production facilities. On the other hand, air pollution control systems to reduce traditional air pollutants contribute to the reduction of mercury emissions as well. These facts have been reflected in the ELVs for mercury emissions.

In response to the entry into force of the Convention, the international community is taking a significant step to control and, where feasible, reduce mercury emissions. As a Party to the Convention, Japan is committed to reducing mercury emissions from the targeted sources. The establishment of the ELVs is the centerpiece to fulfill this commitment.