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

Abstract

Current thermochemical methods to generate H 2 include gasification and steam reforming of coal and natural gas, in which anthropogenic CO 2 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 CO 2 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 CO 2 capture, while the Ni/ZrO 2 catalyst enhanced the secondary H 2 formation via steam methane reforming and water-gas shift reactions.

Obtaining High Yield Hydrogen from Sewage Sludge by Two-Stage Gasification: Alkaline Pyrolysis Coupled with Catalytic Reforming

“…However, this did not affect the performance of NaOH in the alkaline pyrolysis process, and the formation rule of CH 4 and the carbon capture effect were not affected. 24 These results show that it is feasible to recycle NaOH from Na 2 CO 3 to reduce the cost of alkaline pyrolysis. The CaCO 3 produced by the causticizing reaction is calcined to generate CaO and CO 2 , where CaO reacts with H 2 O to generate Ca(OH) 2 .…”

New Insight on Carbon Dioxide‐Mediated Hydrogen Production**

“…According to the International Energy Agency, the energy demand is estimated to increase by 30 % by 2040. [ 1 , 2 ] Simultaneously, the scenario proposes reducing CO 2 emissions by more than 40 % in 2015–2040. Currently, the EU Commission reports that global fossil CO 2 emissions still increased by 0.9 % in 2019 to a total of 38 Gt CO 2 .…”

Exploring the Thermodynamic Limits of Enhanced H2 Recovery With Inherent Carbon Removal From Low Value Aqueous Biomass Oxygenate Precursors

“…Technologies to harness H 2 from gaseous and solid biomass-based feedstocks include steam reforming (SR) in which light hydrocarbons are reacted with steam to produce H 2 and CO 2 , usually in the presence of a catalyst (Ross, 1984;Ming et al, 2002), partial oxidation in which biomass is partial combusted with limited amount of O 2 to produce synthetic gas (a mixture of CO and H 2 ) (Dissanayake et al, 1991;Hohn and Schmidt, 2001), and autothermal reforming (ATR) in which biomass is mixed with steam, and a limited amount of O 2 to produce synthetic gas and CO 2 (Dissanayake et al, 1991;Joensen and Rostrup-Nielsen, 2002;Deluga et al, 2004). Alkaline hydrothermal treatment (ATT) of wet biomass has been extensively reported to enhance H 2 generation from wet biomass with inherent CO 2 capture to produce inorganic carbonates (Stonor et al, 2017a;Zhang et al, 2020). However, few approaches have addressed strategies to harness H 2 from aqueous biomass oxygenate streams.…”