(86b) Unique Synergies between Carbon Mineralization and Biomass Conversion: Alkaline Thermal Treatment for Combined Carbon Capture and Hydrogen Production

Alkaline thermal treatment (ATT) is a promising and robust BECCS method which can run at mild temperatures and pressures (<500^oC, 1 bar) and produces carbon-free high-purity H₂ (>90% v/v) in a single reactor. Hydroxide salts are utilized during the ATT reaction (e.g., NaOH, KOH, LiOH, etc.), facilitating the degradation and conversion of organic matter. Tandemly, carbon from the biomass is captured in the form of stable carbonate salts (e.g., Na₂CO₃). The type of hydroxide utilized will greatly alter the reactivity of the system, with Group I hydroxides operating differently than Group II hydroxides due to differences in melting point and basicity. Herein, we explore the conversion of different types of biomass wastes using ATT to make high purity hydrogen and sequester carbon in the process. Discussion about the ATT reactive mechanism is also provided in the context of conventional steam gasification processes. Unique synergies are also explored between alkaline thermal treatment and carbon mineralization processes to maximize both carbon conversion from biomass and also carbon storage; ideally, as the most stable carbonates of Mg or Ca.