The concept of hydrogen-powered internal combustion engines presents a promising solution for reducing emissions in the transportation sector while maintaining familiarity with existing technology. While the electrification of vehicles is currently leading the decarbonization efforts, challenges such as slow adoption rates persist, with only 11% of car sales in 2023 being fully electric according to IDTechEx. Mika Takahashi, a technology analyst at IDTechEx, explores the potential of hydrogen internal combustion engines in the report 'Hydrogen Internal Combustion Engines 2025-2045.' Hydrogen combustion in internal combustion engines eliminates carbon emissions, offering a cleaner alternative. However, challenges arise from nitrous oxide emissions and the environmental impact of hydrogen production. The report emphasizes the need to reduce NOx emissions from hydrogen combustion to achieve credible emissions reductions, considering factors like air-fuel ratios, engine speed, and exhaust gas treatments. The origin of hydrogen plays a vital role in its environmental impact, with green hydrogen produced using renewable energy standing out as a truly carbon-free option. Different types of hydrogen production methods, such as grey hydrogen from fossil fuels and blue hydrogen with carbon capture, have varying emissions levels. The report highlights the energetic inefficiencies in hydrogen production and transportation, impacting its overall environmental footprint. IDTechEx's analysis evaluates the lifecycle emissions of hydrogen internal combustion engines compared to fuel cell electric vehicles and traditional engines, providing insights into the efficiency and environmental impact of different energy sources. While hydrogen engines offer a pathway to reducing CO2 emissions, addressing challenges related to NOx emissions and sustainable hydrogen production methods is crucial for maximizing their environmental benefits.