Carbon-negative energy production from CO2-cofed pyrolysis of invasive biomass (water hyacinth)

Abstract

Invasive biomass can be supplied for a promising lignocellulosic feedstock to achieve sustainable biofuel production due to its rapid proliferation and the ecological rationale for its utilization. Furthermore, establishing a reliable supply chain is crucial to circumvent ethical and environmental constraints for biofuel production. In this study, the pyrolytic valorization of water hyacinth (WH), a widespread invasive species, was investigated for syngas production. To mitigate energy-related carbon dioxide (CO₂) emissions during pyrolysis, external CO₂ was introduced, particularly exploiting its partial oxidative function. Pyrolysis of WH generated a wide spectrum of volatile compounds, with CO₂ exhibiting favorable reactivity toward oxygenated volatiles, thereby enhancing their transformation into CO. This CO formation induced by CO₂ potentially contributes to a carbon-negativity to the pyrolysis platform. To expedite the kinetics of CO₂-mediated homogeneous reactions, the pyrolysis configuration was altered with an auxiliary heating element operated isothermally at 500, 600, or 700 ˚C, with and without a Ni-based catalyst. Catalytic pyrolysis at a catalyst-bed temperature of 700 ˚C in a CO₂ atmosphere maximized the yield of carbon-negative syngas. These findings highlight a strategic pathway for producing carbon-negative syngas as a clean energy carrier from fast growing invasive biomass while reducing CO₂ emissions from pyrolysis systems.