Abstract
In recent years, several researchers have studied the potential use of ammonia (NH3) as an energy vector, focused on the techno-economic advantages and challenges for full global deployment. The use of ammonia as fuel is seen as a strategy to support decarbonization; however, to confirm the sustainability of the shift to ammonia as fuel in thermal engines, a study of the environmental profile is needed. This paper aims to assess the environmental life cycle impacts of ammonia-based electricity generated in a combined heat and power cycle for different ammonia production pathways. A cradle-to-gate assessment was developed for both ammonia production and ammonia-based electricity generation. The results show that electrolysis-based ammonia from renewable and nuclear energy have a better profile in terms of global warming potential (0.09–0.70 t CO2-eq/t NH3), fossil depletion potential (3.62–213.56 kg oil-eq/t NH3), and ozone depletion potential (0.001–0.082 g CFC-11-eq/t NH3). In addition, surplus heat for district or industrial applications offsets some of the environmental burden, such as a more than 29% reduction in carbon footprint. In general, ammonia-based combined heat and power production presents a favorable environmental profile, for example, the carbon footprint ranges from −0.480 to 0.003 kg CO2-eq/kWh.
Highlights
Ammonia (NH3 ) is currently gaining considerable interest as a zero-carbon energy vector from academic institutions, governmental bodies, and industrial companies
The results show that using ammonia with hydrogen/steam blends potentially can reduce NOX in an order of magnitude, while combustion efficiencies remain high with the implementation of two-stage combustion systems
This agrees with the literature, as the effect of ammonia production depends mainly on the methods used to produce hydrogen [51]; hydrogen synthesis accounts for around 90% of the carbon emissions for ammonia synthesis [35]
Summary
Ammonia (NH3 ) is currently gaining considerable interest as a zero-carbon energy vector from academic institutions, governmental bodies, and industrial companies. Ammonia as fuel still requires further research, especially when demonstrating an integrated approach that considers all the impacts in the production and utilization chain of ammonia produced with different methods and in various regions. The challenges of implementing large-scale green ammonia production and its novel uses must be identified and overcome if its development and deployment are to be accelerated and fully capitalized on [5]. Overall, some of these challenges include upfront investment costs
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