Alkaline thermal treatment of seaweed for high-purity hydrogen production with carbon capture and storage potential

Current thermochemical methods to generate H-2 include gasification and steam reforming of coal and natural gas, in which anthropogenic CO2 emission is inevitable. If biomass is used as a source of H-2, the process can be considered carbon-neutral. Seaweeds are among the less studied types of biomass with great potential because they do not require freshwater. Unfortunately, reaction pathways to thermochemically convert salty and wet biomass into H-2 are limited. In this study, a catalytic alkaline thermal treatment of brown seaweed is investigated to produce high purity H-2 with substantially suppressed CO2 formation making the overall biomass conversion not only carbon-neutral but also potentially carbon-negative. High-purity 69.69 mmol-H-2/(dry-ash-free)g-brown seaweed is produced with a conversion as high as 71%. The hydroxide is involved in both H-2 production and in situ CO2 capture, while the Ni/ZrO2 catalyst enhanced the secondary H-2 formation via steam methane reforming and water-gas shift reactions.