Green urea production for sustainable agriculture

In a global mission to reduce atmospheric concentrations of anthropogenic carbon dioxide, the energy- and carbon-emission-intensive, century-old urea industry has re-captured attention. Today, global urea manufacture from the reaction of ammonia and carbon dioxide, enabled by the Bosch-Meiser process, yields 910 kg of CO₂ for every ton of urea generated. This amount of CO₂ is close to the quantity of CO₂ fixed during its production. Positively, urea utilization as a nitrogen fertilizer facilitates photosynthesis, earth's largest carbon capture carbon cycle. Negatively, the environmental impact of urea production presents a prime example of one of many global industries that need to be decarbonized to ameliorate climate change in the quest for sustainability. In this perspective, we explore the technical feasibility of green urea production, using system-wide energy efficiency as a key metric, via thermochemistry, electrochemistry, and photochemistry pathways. Baseline parameters for potential green urea industries are benchmarked by comparison with current Bosch-Meiser operations. Quantitative studies of this kind will help define a roadmap for green urea refineries that is consistent with the United Nations Sustainable Development Goals.