Cost-competitive design of sustainable urea production: Synergizing solid oxide electrolysis and oxy-fuel combustion-based carbon capture

Abstract

Urea is a vital nitrogen fertilizer for global food security; however, its production remains carbon-intensive owing to heavy reliance on fossil fuel–based H 2 . To reduce the carbon emissions of the urea production process, capturing CO 2 from the flue gas has emerged as a promising strategy. However, this strategy faces several critical limitations. First, the captured CO 2 from flue gas undergoes incomplete conversion into urea, causing inherent carbon losses. Second, conventional air combustion requires substantial fuel consumption, leading to thermodynamic inefficiencies. Finally, absorption-based capture approach causes high thermal energy penalties. To address these issues, this study proposes hybrid urea production processes that introduce solid oxide electrolysis and utilize oxy-fuel combustion within the natural gas-based process. CO 2 F, fully utilizing internally captured CO 2 , and CO 2 E, supplementing external CO 2 , were compared with the base case employing amine-based absorption with partial utilization of the captured CO 2 . The proposed processes maximized the carbon valorization efficiency, reduced fuel consumption, eliminated high thermal energy consumption for solvent regeneration, and achieved high CO 2 capture rates. CO 2 F and CO 2 E achieved a levelized cost of urea as 409.7 $/t Urea and 440.3 $/t Urea , lower than 468.4 $/t Urea for the base case. CO 2 E demonstrated superior environmental performance, achieving a global warming potential of 348.8–462.8 g CO2-eq. /kg Urea , including process direct, indirect and upstream emissions. Notably, under the broader greenhouse gas emission boundary, CO 2 E achieved a higher probability of being economically feasible under variable carbon taxes, credits, and electricity prices.