The NOx Wedge: Large Scale, Non-Linear Emission Effects from Methane to Hydrogen Fuel Switching in Industrial Steam and District Heating Applications

Nitrous oxide (N2O) and carbon dioxide (CO2) are both long-lived greenhouse gases (GHG) that accumulate in the atmosphere. The growth in N2O emissions has exceeded some of the highest projected scenarios1, highlighting the urgent need to lower N2O emissions in addition to CO2. The adverse effects of N2O are making headlines because it is 300 times more potent as a climate change agent2 on a molecule basis than CO2. However, an important and frequently overlooked issue is that the fuel-blending of methane and hydrogen in industry and the building sector, as we transition from methane to hydrogen to lower CO2 emissions, can accelerate the build-up of nitrogen oxides (NOx), another adverse atmospheric agent. We present data3 that demonstrates the potential large-scale effects of fuel-switching strategies in thermal applications with respect to the rise of NOx emissions. We argue that it is crucial to consider the possible public health impact of increasing NOx emissions resulting from energy transition strategies implemented by the G20 nations and globally. New industrial hydrogen boiler technologies offer a potential solution to the hard-to-abate GHG problem for thermal applications in industry and the built environment at scale. We explore economically competitive pathways4 that can also address the potential negative public health effects of fuel-switching with respect to mitigating NOx emissions.