Net carbon reduction from the pyrolysis of corn stover.

Abstract

Cellulosic biomass, such as corn stover, serves as a promising source to produce biofuels, particularly bioethanol through fermentation. Despite the well-establishment of fermentation, it poses limitations in fully utilising cellulosic constituents due to generation of metabolic byproducts, such as carbon dioxide (CO₂). In a pursuit of efficient carbon utilization, this study proposes pyrolytic valorization of corn stover due to its technical benefit in carbon reallocation into three distinct pyrolytic products. Nevertheless, given the energy-intensive nature of pyrolysis, the process-related CO₂ emissions remain inevitable carbon loss. To impart sustainability, CO₂ was introduced as a reactive medium to the pyrolysis system. Understanding the mechanistic roles of CO₂ is a primary aim of this study. CO₂ showed a reactivity of interacting with the volatiles derived from corn stover, leading to their conversion into syngas enriched with carbon monoxide (CO). However, the CO production driven by CO₂ was notable only above 490 °C. To accelerate the CO₂ reactivity, catalytic pyrolysis over a nickel catalyst was performed under controllable variables: catalyst bed temperatures and CO₂ composition. The systematic investigation enabled optimization of CO-rich syngas production, showing a 10.6-times increase compared to referenced pyrolysis. To evaluate the environmental benefits, a carbon footprint of the CO-cofed catalytic pyrolysis was calculated theoretically. The proposed pyrolysis platform offers potentials of suppressing 1107.11 g CO₂ per kilogram of corn stover consumed. Therefore, these findings highlight the potential of using CO₂ in the pyrolytic valorization of corn stover for achieving net carbon reduction.