Economic evaluation of solar-driven thermochemical conversion of empty cotton boll biomass to syngas and potassic fertilizer

•Economic viability of biomass to liquid fuel via solar gasification was evaluated.•Economic feasibility of PF synthesis from residual ash was assessed.•LCOFTD ranged from 1.12 $/L for 5 MWsyn to 0.90 $/L for 20 MWsyn plant.•Mitigation of the CO2 emissions was 86% compared to conventional.•PF recovered from the residual ash was 31% of the annual PF requirement in field. The economic evaluation of concentrated solar-steam gasification of empty cotton boll biomass along with co-production of potassic fertilizer from residual ash was carried out. The study considered four different plant capacities: 5 MWSyn, 10 MWSyn, 15 MWSyn and 20 MWSyn in terms of syngas power and two different methods for synthesis of potassic fertilizer: (1) fractional crystallization, and (2) selective precipitation. The key process parameters like energy efficiencies and mass flow rates, based on experimental results were studied in-depth with a sensitivity analysis. It was found that the heliostat field was the most expensive component of the plant, while the synthesis of potassic fertilizer was economically feasible for all the tested plant capacities. The selective precipitation was found to be gainful than the fractional crystallization. The levelized cost for the liquid fuel via Fischer Tropsch synthesis was estimated at 0.90 USD L−1 for the 20 MWSyn plant. The trends indicate that levelized cost for liquid fuel could further be reduced by increasing the plant capacity. The solar steam-gasification of empty cotton boll biomass has the potential to mitigate the CO2 emissions by 86% compared to conventional fossil fuel. The potassic fertilizer recovered from the residual ash can cover 31% of the annual potassic fertilizer requirement of the cotton fields that originally supplied the feedstock.