Environmental impact assessment of green ammoniacoupled with urea and ammonium nitrate production

Abstract

This study aims to explore more sustainable ammonia production routes for urea and ammonium nitrate fertilizers to support the rising global food demand and help achieve the Net Zero Emissions scenario by 2050. The research uses process modelling tools and Life Cycle Assessment methodology to evaluate the technical and environmental performance of green ammonia production compared to blue ammonia production, both pathways coupled with urea and ammonium nitrate production processes. The blue ammonia scenario uses steam methane reforming for H₂ production, while the sustainable approach scenarios consider water electrolysis with renewable resources (i.e., wind, hydro and photovoltaics) and nuclear power as a carbon-free source for H₂ generation. The study assumes an annual productivity of 450,000 tons for both urea and ammonium nitrate. The environmental assessment uses mass and energy balance data derived from process modelling and simulation. A cradle-to-gate environmental evaluation is conducted using GaBi software and the Recipe 2016 impact assessment method. Results show that green ammonia production requires less raw materials but has higher energy consumption due to electrolytic H₂ production (i.e., >90% of total energy requirements). The use of nuclear power achieves the highest reduction in global warming potential (i.e., 5.5 times for urea and 2.5 times for ammonium nitrate production processes), while hydro power coupled with electrolytic H₂ production shows lower environmental impacts in most categories (i.e., six out of ten impact categories). Overall, the sustainable scenarios prove to be suitable alternatives for fertilizer production towards achieving a more sustainable future.

Keywords: Ammonium nitrate production; Green ammonia production; Life cycle assessment; Renewable energy; Urea production.