Synergies and tradeoffs between climate action and mercury reductions: a matrix approach to analyzing human-technical-environmental systems

Abstract:

Some efforts to address air pollution and climate change together (such as eliminating fossil fuel burning) can be synergistic, but others may introduce tradeoffs. End-of-pipe pollution controls can mitigate some air pollutants including mercury (Hg), but do not reduce CO₂ emissions. Identifying synergies and tradeoffs is critical for understanding and intervening to promote sustainability. To assess their dynamics, we introduce a new systems-oriented analytical framework – the human-technical-environmental (HTE) framework (Selin and Selin, 2020).The framework uses a matrix-based approach to examine material interactions among human, technical, and environmental components in the context of non-material institutional and knowledge components, and to assess system-wide implications of interventions. We apply the framework to examine past, present, and future trajectories of Hg and CO₂ emissions from coal-fired power plants in the United States and China. We assess the implications of interventions to enhance pollutant reductions by simulating the imposition of technology-based controls as well as fossil fuel reductions. We calculate local and global-scale present and future Hg deposition resulting from controls and climate policies. We estimate how the lifetimes of power plants affect near-term and long-term adverse impacts of CO₂ and Hg emissions. Synergies and tradeoffs depend on interactions of technology, knowledge, and institutions. In the US, where average coal-fired power plant age is high, shortened lifetimes of fossil energy sources due to Hg emission standards have a moderate synergistic effect on Hg and CO₂ emissions. In China, there is greater potential for tradeoffs where lengthening the lifetime of newer coal-fired power plants could lead to longer-term climate impacts. The degree of synergy, however, is constrained by institutional factors: the 2013 Minamata Convention on Hg would likely not be in force today if it had focused on controlling coal burning. The costs and benefits of different interventions are also unevenly distributed. While short-term pollutant reductions benefit nearby populations, long-term benefits are distributed globally. We suggest ways in which further interventions can encourage synergies among sustainability-related goals in practice.