Green pathways for urea synthesis: A review from Australia's perspective

Abstract

• Historical trend of the unsustainable fertilizer manufacturing should pursue greener pathways. • Green ammonia feedstock is critical but should be complemented with non-fossil CO 2 sources. • Three potential non-fossil-fuel CO 2 resources are discussed and evaluated in Australia. • Carbon-neutral CO 2 from biomass, renewable methane, or direct air capture may fit the criteria. • Proper energy management systems are essential for process synchronization and optimization. This paper discusses the status of the global fertilizer industry with a primary focus on Australian market. The conventional energy- and carbon-intensive ammonia production industry is taking serious steps in transforming to more environmentally benign pathways via utilising ‘green’ hydrogen (hydrogen production via water electrolysis powered by renewable energy) feedstock into their production process and utilizing more of the CO 2 by-product into downstream processes such as urea production. However, it is very challenging for ammonia and other fertilizer production routes to use ‘green’ pathway to completely decarbonize agriculture and food industry. Here, we argue that urea synthesis can only be considered as a ‘green’ technology if ammonia feedstock is produced via ‘green’ pathway and the CO 2 feedstock comes from non-fossil-fuel and carbon-neutral sources. Three possible resources for carbon-neutral CO 2 are identified and discussed within Australia's context: from biomass, renewable methane, and from direct air carbon capture (DAC). Each of these carbon-neutral CO 2 routes has many opportunities and challenges that may affect the cost of production, but the trajectory urea prices and growing market demand if supported by an adequate government regulatory framework would be able to make the ‘green’ urea production cost affordable. Achieving this goal however would require proper energy management systems to synchronize and optimize such a multi-player orientation for a common objective of maximizing the penetration of renewable sources at competitive costs. In this review, it is emphasized that this challenge could be addressed more effectively via a rigours intelligent energy network (IEN) by managing the dynamics of the supply and demand, integrating reliable storage systems, reclaiming the waste heat, and improving process efficiencies. Local ‘green’ urea production at competitive costs would help Australia realizing ambitions to become a leading green fertilizer and renewable energy exporter in the region.