Hydrogen Production from Biomass Gasification Using Dolomite and Mechanical Mixtures of CaO-MgO-K₂CO₃

Biomass gasification has the potential to be a reliable technology for renewable hydrogen production once its technoeconomic efficiency is increased. Dolomite is a material commonly used to improve gasification performance after calcination (CaMgO₂), which depends on its composition (primarily calcium and magnesium) and the interactions among its components. However, its effectiveness is highly variable due to compositional differences based on the extraction site. Therefore, the composition and properties of dolomite can vary significantly between samples, complicating our understanding of their effect on biomass gasification. This research aims to elucidate the impact of the proportions of calcium and magnesium oxide (CaO and MgO) in dolomite and mechanical mixtures, along with the addition of potassium carbonate (K₂CO₃), on hydrogen production through biomass steam gasification in a fluidized bed reactor. Remarkably, the mechanical mixtures showed a similar performance to dolomite. Even the highest H₂ yield (441 mL/g-of-biomass-feed) was achieved with a mechanical mixture of CaO, MgO, and K₂CO₃, which was 11% higher than the yield from the dolomite-K₂CO₃ mixture and a 4-fold increase compared to no additives. These findings suggested a synergistic interaction between calcium and magnesium in mechanical mixtures that was previously attributed solely to dolomite. Additionally, CaO could be related to the decreased concentration of acidic tar, while K₂CO₃ diminished basic tar compounds. This kind of study is crucial for the development of cost-effective catalysts using these abundant and inexpensive materials, advancing biomass gasification as a truly viable and sustainable method for large-scale H₂ production.