Hydrogen fuel cells are more than twice as efficient as traditional internal combustion engines. As the only emission from the vehicle’s exhaust is water, if the hydrogen is produced using renewable energy (i.e biomass, wind and solar) fuel cell vehicles can reduce carbon dioxide emissions by 90%.
(https://bit.ly/3eeoQs3, https://bit.ly/3x5MeRg, https://bit.ly/2OYNjsM)