Technoeconomic assessment comparison of batch and continuous hydrothermal carbonization of waste corn stover into advanced biorefinery feedstock

Abstract

The objective of this study was to investigate the economic feasibility of the hydrothermal carbonization (HTC) of waste corn stover. Two different cases of HTC of waste corn stover were considered for a 544 320 kg day−1 as-received corn stover plant. Case I assumed a batch HTC process, and case II assumed a continuous HTC process. The results show that both cases were economically feasible; however, case I reached the break-even point at 3 years whereas case II reached the break-even point at 4 years. Case I also showed greater return on investment (5.02) than case II (3.98) at the end of the 20 year project life, including 26.6% lower total capital investment. About 73% of fixed capital cost came from investment in the reactor alone for case I, whereas 63% came from the reactor for case II. The break-even selling price of the product was found to be $86.1/kg. A sensitivity analysis showed that the break-even selling price of the product was the most sensitive to the variation of the cost of corn stover and the least sensitive to variation in the tipping income.