(729c) Life Cycle Analysis of NOx Emissions from Combustion of Hydrogen Blends in Natural Gas

Hydrogen (H₂) has no tailpipe emissions (end-use emissions) and is considered a clean energy carrier when produced with renewable or low-carbon energy sources. It also has the potential to reduce carbon emissions by replacing fossil fuels in various end-use applications. For example, H₂ can be combusted to energize commercial, industrial, and utility applications (with appropriate equipment modification) where natural gas (NG) dominates today. Due to the absence of widespread H₂ infrastructure, enabling clean H₂ production at scale requires a corresponding market demand. Blending clean H₂ with NG in existing NG pipelines can provide a market liftoff for clean H₂ production while decarbonizing NG supply to various end-use applications. However, this approach comes with challenges, one of which is the potential increase in nitrogen oxides (NO_x) generated from the combustion of H₂ in the blend with NG. Therefore, careful evaluation of NO_x emissions from the combustion of H₂-NG gas blends in various end-use applications is needed before practical implementation.

This study focuses on analyzing NO_x emissions using available data sources and covering all stages of the gas life cycle, from fuel feedstock recovery to end-use combustion. Our life cycle analysis includes different technologies for clean H₂ productions (e.g., SMR-CCS, solar/wind power, etc.), two blended gas delivery scenarios (constant volumetric flow rate and constant energy throughput), and various end-use applications (e.g., boiler, engine, etc.). For the considered cases, the life cycle NO_x emissions at different blending ratios of H₂ with NG are reported and discussed with respect to the feasibility of using gas blends in various end-use applications. Results show that NO_x emissions vary at different H₂ blending ratios, and they may not be significantly increased by the H₂ addition in most cases. In addition, emissions control technologies may be employed to mitigate any increase in NO_x emissions.