Ammonia and conventional engine fuels: comparative environmental impact assessment

Abstract

Ammonia has recently attracted great attention as a fuel for internal combustion engines. The aim of this study was to compare the environmental impact caused by the production processes of ammonia and conventional engine fuels – gasoline and diesel oil. Present fuel technology, commonly used in Europe, was investigated. Haber-Bosch process for ammonia synthesis was considered, coupled with steam methane reforming (SMR) and partial oxidation of heavy oils (POX) as sources of hydrogen. Fuel technology was evaluated with the use of Life Cycle Assessment (LCA), based on a total emission of selected pollutants, including greenhouse gases, total consumption of water and primary energy, as well as Eco-indicator 99 score. LCA results indicated that current industrial methods for ammonia production have unambiguously more negative impact on the environment, compared to fossil fuel technologies, when energy content of the fuel is taken into account. The environmental load of ammonia production process depends strictly on the method of hydrogen obtaining. SMR has lower negative impact on the environment than POX. In order for ammonia to be considered as a potential transportation fuel, the use of hydrogen generation pathways that are less burdensome to the environment should be promoted.