Life cycle assessment of ammonia as transportation fuel

• Main Author: Are, Kristian Ray Angelo G.
• Format: text
• Language: English
• Published: Animo Repository 2015
• Online Access: https://animorepository.dlsu.edu.ph/etd_masteral/4950
• Institution: De La Salle University

Ammonia (NH3) is a non-hydrocarbon transportation fuel with some fuel properties that are better compared to other alternative fuels. However, it has a low flame speed so it would need to be mixed with a more combustible secondary fuel to form a dual fuel system. Current methods of NH3 production are also major consumers of fossil fuels and emit large amounts of greenhouse gas. This study assessed the life-cycle global warming potential (GWP) and non-renewable energy consumption (NREC) of using different NH3-fuel mixtures in combustion engines. Four fuel mixtures that have previously been tested by other researchers were considered, wherein NH3 is mixed with gasoline, diesel, hydrogen or dimethyl ether (DME). Four processes of NH3 production were considered: steam reforming (SR), partial oxidation (PO), and two biomass-based processes using cereal straw (Salix) and cyanobacteria (Anabaena ATCC 33047) as feedstocks. Contribution, sensitivity, and uncertainty analyses (Monte Carlo simulation) were conducted for life-cycle interpretation. The study concludes that the environmental impacts of NH3 fuel depend on factors such as (i) method of NH3 production and (ii) type of NH3 fuel mixture. Using NH3 to substitute diesel is more environmentally beneficial than using it as a gasoline substitute, i.e. NH3-diesel fuel mixtures have lower GWP and NREC compared to pure diesel, while NH3-gasoline fuel mixture have higher GWP and NREC compared to pure gasoline. NH3-H2 mixtures have the lowest GWP and NREC among the four fuel mixtures but this will require new engines. Over-all it is shown that fuel systems involving biomass-based NH3 have lower environmental impacts as compared to their conventionally-produced NH3 counterparts.