Abstract
Current thermochemical methods to generate H2 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 H2, 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 H2 are limited. In this study, a catalytic alkaline thermal treatment of brown seaweed is investigated to produce high purity H2 with substantially suppressed CO2 formation making the overall biomass conversion not only carbon-neutral but also potentially carbon-negative. High-purity 69.69 mmol-H2/(dry-ash-free)g-brown seaweed is produced with a conversion as high as 71%. The hydroxide is involved in both H2 production and in situ CO2 capture, while the Ni/ZrO2 catalyst enhanced the secondary H2 formation via steam methane reforming and water-gas shift reactions.
Highlights
Current thermochemical methods to generate H2 include gasification and steam reforming of coal and natural gas, in which anthropogenic CO2 emission is inevitable
Brown seaweed procured for this study contains a high ash content of 28.3 wt.% in total solid with a low moisture content of 7.8 wt.%
supercritical water (SCW) has been suggested as an effective means for producing H2 due to the ability of dissociated water to behave as an organic solvent[31]
Summary
Current thermochemical methods to generate H2 include gasification and steam reforming of coal and natural gas, in which anthropogenic CO2 emission is inevitable. A catalytic alkaline thermal treatment of brown seaweed is investigated to produce high purity H2 with substantially suppressed CO2 formation making the overall biomass conversion carbon-neutral and potentially carbon-negative. Their limited availability compared to fossil resources, the associated land use change, and the need for freshwater for cultivation and growth are often used to argue against the large-scale long-term impact of bioenergy[9,10]. Compared to terrestrial biomass, seaweed has a high average CO2 sequestration rate (36.7 ton hectare−1 year−1, seven times greater than that of conventional lignocellulosic biomass), rapid growth rate (harvested up to six times per year even without fertilizer), and does not compete with land-based food crops if grown in the sea[15,16]
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