Advantages of Biomass Gasification Hydrogen Production

Against the backdrop of the global energy supply crisis, the use of hydrogen not only contributes to enhancing energy security but also reduces the reliance on fossil fuels in end-use applications. This broadens the demand for renewable energy in hydrogen production, aiming to achieve the decarbonization of the entire societal energy system.

As the global economy rebounds, the total global demand for hydrogen reached 94 million tons in 2021, marking a 5% year-on-year increase. Hydrogen accounts for 2.5% of the global end-use energy, surpassing the 2019 level of 91 million tons. According to the hydrogen development policies established by various countries, it is anticipated that by 2030, the global demand for hydrogen will continue to rise rapidly, reaching 115 million tons. In a scenario where governments worldwide successfully achieve their climate targets, the global hydrogen demand by 2030 is expected to surpass 130 million tons.

The International Energy Agency (IEA), in its 2019 report released during the G20 Summit in Tokyo, highlighted the rapid advancements in hydrogen-related technologies, which continue to drive the expansion of low-carbon hydrogen production capacity. Electrolysis of water to produce hydrogen, as a currently more mature green hydrogen production technology, is expected to gradually achieve scalability in the industry. According to IEA predictions, by 2030, hydrogen produced through renewable energy-powered electrolysis is expected to meet at least 25% of the global hydrogen demand.

green hydrogen energy

In addition to the electrolysis of water, which is an upstream method for green hydrogen production in the hydrogen energy industry, there is another unique method for green hydrogen preparation. This involves utilizing agricultural and forestry crops as raw materials, subjecting them to gasification under high-temperature and oxygen-deficient conditions, and transforming them into small-molecule syngas (mainly carbon monoxide and hydrogen). Subsequently, impure hydrogen is produced through steam reforming reactions, commonly referred to as biomass gasification for hydrogen production.

Advantages of Biomass Hydrogen Production

Biomass generally refers to agricultural and forestry waste crops, such as fast-growing wood, and herbaceous straw. The combustion of biomass itself can achieve small-scale carbon cycling, representing a zero-carbon utilization method. Therefore, biomass-based hydrogen production is a unique method of obtaining hydrogen that depends on specific application scenarios. It has three main advantages:

Relatively Mature Technical Pathway

The composition of biomass raw materials is analogous to that of traditional fossil fuel coal, and both biomass and coal are solids at room temperature. Therefore, the technology for biomass-based hydrogen production bears similarity to coal-based hydrogen production in coal chemical processes. The technical pathway involves subjecting biomass to thermochemical conversion under high temperatures (typically between 800-1300℃, sometimes with added pressure or adjusted to negative pressure) and oxygen-deficient conditions. This process results in the transformation of biomass into syngas, primarily composed of carbon monoxide and hydrogen. Given that biomass contains a significant amount of carbon elements, the syngas produced have a higher content of carbon monoxide (CO). In the second step, steam is introduced into the system, typically at temperatures ranging between 300-400℃. This facilitates a chemical reaction, commonly known as steam reforming or the water-gas shift reaction in industrial terms, significantly increasing the proportion of hydrogen and thus producing hydrogen gas.

Produce Hydrogen Adaptively

In regions abundant in agricultural resources, during the harvest season, farmers need to manage a large amount of crop residues, and burning them could lead to regional air pollution. Similarly, in areas rich in forestry resources, fast-growing forests, once furniture and wood materials have been removed, still have many discarded branches that need to be processed. Therefore, utilizing agricultural and forestry waste for hydrogen production allows for the adaptive transformation of waste into a valuable resource, converting discarded materials into high-quality energy for practical use.

Relatively Low Production Costs

The production costs of electrolysis for hydrogen production are constrained by the price of green electricity and the efficiency of electrolysis. In contrast, the technical pathway for biomass hydrogen production is relatively mature, closely analogous to coal hydrogen production. Additionally, coal hydrogen production is currently the most mature technology in China, boasting the lowest production costs and the broadest application on a large scale. Therefore, biomass hydrogen production, sharing similarities with coal hydrogen production, is considered a relatively low-cost method for the preparation of “green hydrogen” at the current stage.

Challenges of Biomass Hydrogen Production

While biomass hydrogen production presents numerous advantages, it also faces certain limitations at the current stage.

green hydrogen

Firstly, the material balance of biomass hydrogen production requires consideration of carbon dioxide capture. In the process of converting biomass into hydrogen, during the second step involving the steam reforming reaction (where carbon monoxide reacts with water to produce hydrogen and carbon dioxide), carbon dioxide (CO2) is generated. As a result, the produced hydrogen contains impurities, and there is a need to manage the generated carbon dioxide. This can have some impact on the subsequent “zero-carbon” accounting of the technology. However, when considering the entire biomass utilization cycle, this technology still falls under the category of “zero-carbon” techniques.

Secondly, the energy balance of biomass hydrogen production needs to consider the impact of endothermic reactions. In the first step of the biomass gasification reaction, the primary chemical reactions are endothermic, requiring external heat input. Whether the external energy supplied falls under the category of green energy in a carbon-neutral context may also need subsequent verification.

Lastly, the application scenarios for biomass hydrogen production are currently quite limited. The energy density of biomass feedstock is relatively low, and transportation costs can be high. Optimal utilization tailored to specific locations is the most cost-effective approach, but such location-specific utilization can hinder the subsequent large-scale production of this technology. Therefore, the scalability of its application is subject to certain limitations.

Conclusion

In summary, biomass hydrogen production, at the current stage, represents a relatively mature technical pathway, yet it remains a “small but beautiful” technology that is challenging to scale up. This technology uniquely offers a new approach to the preparation of green hydrogen by employing traditional engineering methods to address new challenges. If it can be effectively applied in a location-specific manner, biomass hydrogen production has the potential to showcase high-quality energy cascading utilization in the ongoing development of hydrogen energy.

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