Abstract
Synthetic nitrogen fertilizers such as urea are a necessity for food production, making them invaluable toward achieving global food security. Conventional manufacture of urea is conducted in centralized production plants at an enormous scale, with the subsequent prilled urea product distributed to the point-of-use. Despite consuming carbon dioxide in the synthesis, the overall process is carbon positive due to the use of fossil feedstocks, resulting in significant net emissions. Blue Urea could be produced using attenuated reaction conditions and hydrogen derived from renewable-powered electrolysis to produce a reduced-carbon alternative. This paper demonstrates the intensified production of urea and ammonium nitrate fertilizers from sustainable feedstocks, namely water, nitrogen, and carbon dioxide. Critically, the process can be scaled-down such that equipment can be housed in a standardized ISO container deployed at the point-of-use, delocalizing production and eliminating costs, and emissions associated with transportation. The urea and ammonium nitrate were synthesized in a semi-continuous process under considerably milder conditions to produce aqueous fertilizers suitable for direct soil application, eliminating the financial and energetic costs associated with drying and prilling. The composition of the fertilizers from this process were found to be free from contaminants, making them ideal for application. In growth studies, the synthesized urea and ammonium nitrate were applied under controlled conditions and found to perform comparably to a commercial fertilizer (Nitram). Crucially, both the synthesized fertilizers enhanced biomass growth, nitrogen uptake and leaf chlorophylls (even in depleted soils), strongly suggesting they would be effective toward improving crop yields and agricultural output. The Blue Urea concept is proposed for installation in ISO containers and deployment on farms, offering a turnkey solution for point-of-need production of nitrogen fertilizers.
Highlights
Nitrogen Fertilizers and Food SecuritySynthetic fertilizers are a vital component of intensive agriculture and a necessity for global food production
Experiments were conducted to characterize the performance of the aforementioned single-tube reactor design, such that “scaleout” to a multi-tube system could be rigorously validated
The steady-state values for each parameter have been indicated on the figure, excluding those for scrubber temperatures which show the values upon first neutralization
Summary
Synthetic fertilizers are a vital component of intensive agriculture and a necessity for global food production. Removal of nutrients by crops during growth necessitates the use of fertilizers to accelerate soil replenishment and so maintain the productivity of intensive agriculture. Nitrogen fertilizers are especially important since available nitrogen is typically the limiting nutrient that inhibits soils from sustaining intensive crop growth (Yara, 2017). The economic growth of less developed countries is resulting in more varied and calorie dense diets, demanding higher productivity (Stewart and Roberts, 2012). Because of these challenges, the continued use of synthetic fertilizers within agriculture is expected for the foreseeable future
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