Urea production: An absolute environmental sustainability assessment

The demand for urea, as the most popular global nitrogen fertilizer, is on the rise and as such, its performance in an environmentally sustainable perspective relative to planetary boundaries is high on the agenda. The increasing interest in nitrogen fertilizers is to improve agricultural methods for a better production rate, but can it become environmentally sustainable? Which is due to the significant contribution of fertilizers in the anthropogenic impacts of industrial activities on nature, should be considered. Here, a system analysis based on real data using life cycle assessment linked to the planetary boundaries framework (PB-LCIA) was conducted to study the performance of total urea consumption in Iran, 1.8E+6 metric tons per year. In LCA, midpoint and endpoint methods (ReCiPe 2016) and for AESA, a PB-LCIA methodology was utilized. Results showed that global warming potential, freshwater eutrophication, and marine eutrophication contribute 1.37E+09 kg CO₂ eq, 1.63E+04 kg P eq, and 1.28E+04 kg N eq, respectively, while the GHG emissions of combustion, electricity, and natural gas sweetening have the most contribution to global warming by 35, 24 & 15 %, respectively. Regarding absolute sustainability, global warming, ocean acidification, and biochemical N exceed this activity's assigned share of safe operating space (SoSOS). However, choosing different sharing principles can influence to what extent this activity exceeds or stays within the assigned SoSOS; accordingly, the Nitrogen Biogeochemical flows depend on the sharing principle. Ultimately, the total Iranian urea consumption as fertilizer is not absolutely sustainable. The promising point is that producing sustainable electricity and feedstocks could lead to more sustainable urea fertilizers.