| Minamata Convention | WNP Processing Plant Air Discharge Assessment | 4397169-66885702-113 | 16/06/2022 | 12 Sensitivity: General 4 Minamata Convention 4.1 Proposed Changes to NESAQ New Zealand is a signatory to the Minamata Convention on Mercury in 2013 but has not yet ratified it. To address the obligations under Articles 5(6) and 8 of the Convention, two amendments to the NESAQ were proposed in 2020 (in addition to other changes to the NESAQ)18. These changes are shown below. 1. prohibit the use of mercury in certain, listed processes known as Annex B processes. These have not been carried out in New Zealand, and they are not likely to be as technology has improved, removing the need for mercury 2. require applications for specified, new activities involving emissions of mercury to air, known as Annex D sources, to consider international best practice guidance (a combination of best available techniques and best environmental practice). Point 2 is the most relevant change to the proposed emissions from the Processing Plant. Under the Minamata Convention, smelting and roasting processes used in the production of non-ferrous metals are an Annex D source. However, the proposed changes to NESAQ would only apply to new emissions, or sources which have undergone substantial modifications. OGNZL does not propose to make any changes to the electrowinning or smelting process used in the Gold Room but will install additional mercury control equipment, in the form of the retort oven. Therefore, the proposed changes to the NESAQ would not be applicable to the proposal. The NESAQ Consultation Document notes that, “in New Zealand, current best practice is unlikely to result in significantly stricter controls than the RMA and resource consents require”. For completeness, the requirements of the guidelines are discussed in this report. 4.2 Minimata Best Practice Guidelines The Minimata Best Practice Guidelines19. (Minimata BPG) provide an overview of the co-benefits of mercury removal from discharges with a range of metal smelting processes and rates their effectiveness. Many of the emission control techniques discussed are not relevant to the OGNZL process due to differences in the type of ore and the upstream ore process. The Minimata BPG does not prescribe minimum standards of mercury removal and does not recommend the type of equipment that should be used. Rather, it provides general information on the costs and performance of various different technologies. 18 Ministry for the Environment, 2020. Proposed amendments to the National Environmental Standards for Air Quality, Particulate Matter and Mercury Emissions. 19 United Nations Environmental Programme/Secretariat of the Minamata Convention on Mercury. 2019 Guidance on the Best Available Techniques and Best Environmental Practices.
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