Carbon-negative hydrogen production technologies: new perspectives for

Hydrogen, seen as the “ultimate energy” for the 21st century, offers benefits such as being clean and renewable, as well as being storable and versatile. The International Energy Agency estimates that 115 million tons of hydrogen will be needed by 2030 to bring global net carbon dioxide emissions to zero by 2050. This makes green hydrogen a promising pathway to a carbon-free society.

By utilizing biomass for hydrogen production, we can reduce the carbon emissions produced by fossil fuels, thereby helping to overcome the worsening energy crisis. The new alkaline thermal treatment (ATT) technology for hydrogen production involves pyrolysis at atmospheric pressure and low temperature. From a complete biomass life cycle perspective, ATT has significant potential for “negative carbon emissions” and can replace some fossil fuels.

In a review published in the journal KeAi Carbon Resources Conversion, the research team comprehensively examined the latest advances in ATT biomass for hydrogen production. “There are many factors that influence the efficiency of hydrogen production from biomass ATT,” explained the study’s first author, Guojie Liu, a PhD student in the School of Chemical Engineering, Sichuan University. “They include alkalis, raw materials, catalysts, process parameters, and reactors, among others.”

“However, we must first clarify the fundamental role and synergy of alkalis and catalysts in the ATT reaction and biomass conversion mechanism, and then use that knowledge to guide the development of more effective upgrading strategies and even breakthroughs in large-scale applications, Liu added.

To overcome this, the team believes that in order to maximize the efficiency of hydrogen production from the ATT reaction, the alkali used should promote the conversion of biomass into small intermediates that can be gasified and stored in-situ carbon.

“In addition, by overcoming the kinetic limitations of the reforming reaction under low pressure and temperature in the ATT process, the efficiency of hydrogen production can be improved, and the synergy between the alkali and metal catalysts can be fully demonstrated,” explained Houfang Lu, professor in the same school.

After the review, four main conclusions were drawn. In order to better understand the transformation of model substances through different alkalis and identify more suitable biomasses, further studies are needed. In order to construct a suitable catalyst system based on the ATT reaction intermediate product, an analysis should be carried out on the catalyst deactivation mechanism, the interaction between the active site and the carrier, and the structure-catalytic activity relationship. In addition, when weighing the advantages and disadvantages of in-situ and ex-situ reactions, designing reasonable reactors and developing efficient inlet/outlet methods is key to addressing problems such as coke, limited mass transfer, and catalyst regeneration caused by solid-solid reaction. Finally, an economic assessment and an analysis of energy consumption should be carried out.

“We hope these points will guide the upcoming experiment of hydrogen production through the biomass ATT process to realize the industrialization of this technology,” said Lu.

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Contact the author: Houfang Lu, (email protected), (email protected)

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