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

Current thermochemical methods to generate H include gasification and steam reforming of coal and natural gas, in which anthropogenic CO emission is inevitable. If biomass is used as a source of H, 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 are limited. In this study, a catalytic alkaline thermal treatment of brown seaweed is investigated to produce high purity H with substantially suppressed CO formation making the overall biomass conversion not only carbon-neutral but also potentially carbon-negative. High-purity 69.69 mmol-H/(dry-ash-free)g-brown seaweed is produced with a conversion as high as 71%. The hydroxide is involved in both H production and in situ CO capture, while the Ni/ZrO catalyst enhanced the secondary H formation via steam methane reforming and water-gas shift reactions.