Nitrogen Oxides in Underground Mining: A Review of Emission Sources, Mitigation Strategies, and Sustainable Solutions

Exposure to nitrogen oxide (NOx) in underground mining workings poses a significant threat to the health and safety of workers, while NOx emissions also represent an important environmental challenge associated with the operation of diesel-powered mining equipment. This article provides an overview of primary and secondary methods for limiting emissions and reducing exposure to NOx under underground mining conditions. The primary methods include intensified ventilation, extended ventilation time after blasting, the use of low-emission fuels, and modifications to combustion engines, including exhaust gas recirculation (EGR). The secondary methods include the use of exhaust gas purification technologies such as photocatalysis, oxidation catalysts (DOCs), selective catalytic reduction (SCR), and nitrogen oxide traps (LNTs). The presented solutions were compared in terms of NOx reduction efficiency, implementation costs, technical requirements, and practical applicability in underground workings. The most effective strategies in the short and long term were identified, taking into account the growing role of machine park electrification as a potentially sustainable solution to reducing emissions at their sources. Additionally, an SWOT analysis of NOx emission reduction methods designed for deep underground ore mines was conducted, enabling assessment of their strengths and weaknesses as well as opportunities and threats related to their implementation. The results can support the selection of NOx emission reduction methods that take into account environmental protection, worker safety, technical possibilities, and implementation costs and thus contribute to more sustainable underground mining.