Air Quality Implications of Using Ammonia as a Renewable Fuel: How Low Can NOx Emissions Go?

In addition to their lifecycle carbon emissions, another important issue with decarbonized energy pathways is their air quality, water, or land use implications. This paper considers the air quality issue for ammonia combustion. When directly combusting ammonia, reactions of its N atom with atmospheric oxygen lead to NOx emissions that are O(103) ppm, 2 orders of magnitude higher than EPA limits or the amount emitted by current natural-gas-fired technologies. In order to provide guidance to policymakers and technologists on what is fundamentally possible, this Perspective analyzes the fundamental minimum NO x emissions that can be produced from ammonia combustion. The analysis shows that it is possible to achieve quite low NO x emission levels of O(10) ppm, but these designs differ markedly from those used in today's lean, premixed combustion systems.

Automated summary

In addition to carbon emissions, decarbonized energy pathways also face challenges regarding air quality, water resources, and land use. This paper focuses on the air quality issue of ammonia combustion and analyzes the minimum NOx emissions achievable. The analysis reveals the possibility of achieving significantly lower NOx emissions, but it requires different design approaches compared to current combustion systems.