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Does the combustion of ammonia release a large amount of nitrogen oxide into the atmosphere?

A.　 No, that is not the case. Actually, it is possible to reduce emissions of nitrogen oxides　like NO, NO2, and N2O, (collectively “NOx”) to below current emission levels of power plants using conventional fossil fuels. This can be achieved by using technology developed in Japan to be able to keep proper condition during the combustion process.
  • Research has shown that fuel ammonia is less flammable than conventional fossil fuels. If ammonia is not burned properly, then ammonia has the potential to emit NOx and unburned ammonia which are a high risk for contributing to global warming and air pollution.
  • Even if the use of fuel ammonia can reduce GHG (greenhouse gas) emissions, it is not acceptable to add new environmental burdens to the earth. R&D and social implementation must be promoted so that emissions of harmful components other than GHG are also below the current level.
  • Industry, government, and academia have cooperated in research and development to establish a combustion method that can simultaneously reduce emissions of GHG including CO2, nitrogen oxides, and unburned ammonia 1-6). For example, a project is underway to reduce CO2 emissions by 20% while keeping nitrogen oxide emissions at the same level as before by co-firing 20% ammonia at a coal-fired power plant2). In addition, studies have shown that when ammonia is used as fuel for burners in industrial furnaces, NOx emissions in the exhaust gas can be kept below the Japanese environmental standards by optimizing a method for blowing in the oxidizer 3, 4). Other studies have shown that even in the case of pure ammonia firing, gas turbines can generate 2,000 kW of electricity without emitting unburned ammonia and N2O, and GHG emissions can be reduced by more than 99%5).
  • In international shipping as well as domestic shipping in Japan, the conversion of fuel from conventional heavy oil, natural gas, etc. to ammonia is being considered as a promising alternative of decarbonizing ship propulsion fuels. The reduction of unburned ammonia and NOx emissions in exhaust gases is one of the key development issues, and both improvements to optimize ammonia combustion and NOx emission reduction in engines, and the removal of residual ammonia, NOx andN2O in exhaust gases using catalytic decomposition equipment. are being developed domestically and internationally6).
  • Thus, by using the correct ammonia combustion and exhaust gas purification methods, it is possible to reduce GHG emissions while keeping nitrogen oxide and ammonia emissions to the atmosphere below current levels. Furthermore, activities are now underway for international standardization so that the ammonia utilization technology that Japan has worked together to develop will be adopted not only in Japan but also in other countries.
  1. H. KOBAYASHI and A. HAYAKAWA (2016), Carbon-free Ammonia Combustion, Journal of Combustion Society of Japan, Vol.58 No.183 pp41-48 (In Japanese)
  2. JERA (2022), JERA and IHI Move Up the Start of Large-Volume Co-firing of Fuel Ammonia in the Demonstration Project at Hekinan Thermal Power Station【Link】
  3. Murai et.al., Review of Fundamental Study on Ammonia Direct Combustion in Industrial Furnaces, Journal of the Combustion Society of Japan, Vol. 61, No. 198 (2019), pp.320 -325 (In Japanese)
  4. IHI (2022), CO₂-free power generation achieved with the world’s first gas turbine using 100% liquid ammonia –Reduction of over 99% greenhouse gases during combustion–【Link】
  5. Shipping Zero Emission Project, MLIT (2022), Toward Achieving Net Zero GHG Emissions from International Shipping【Link】

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