As a carbon-free alternative fuel for internal combustion engines (ICEs), ammonia (NH 3 ) is gaining popularity in global decarbonization and sustainable transportation initiatives. Ammonia reduces CO 2 emissions due to its hydrogen-rich composition and minimal carbon content. Its use in combustion engines presents unique and complex emission challenges that differ from those of hydrocarbon fuels. Unburned ammonia (NH 3 slip), nitrogen oxides (NO x ), and nitrous oxide (N 2 O) pose significant environmental, health, and regulatory risks. This comprehensive evaluation examines emissions from ammonia-fueled engines. It reviews recent literature on combustion behavior, pollutant formation processes, and advanced aftertreatment technologies. Dual-fuel strategies, such as ammonia-hydrogen and ammonia-diesel, and their impacts on flame propagation, emissions control, and fuel reactivity are discussed. The paper also considers the performance and selectivity of SCR systems, AMOX catalysts, and AI-driven adaptive control frameworks. Tables, statistics, and performance graphs illustrate emission trends, thermal management requirements, and trade-offs across different operating conditions. The durability, regeneration, and poisoning resistance of catalytic materials in real-world applications are thoroughly examined. Researchers, engineers, and policymakers can utilize this mini-review to identify potential obstacles in developing clean, efficient, and scalable ammonia-powered vehicle systems.
Chen et al. (Sat,) studied this question.