Biomass Hydrogen Production: Analysis Of Technology Costs And Application Scenarios

Biomass hydrogen production mainly refers to the use of gasification or microbial catalytic deoxygenation to produce hydrogen-containing synthesis gas after biomass undergoes different pretreatments. China's annual available biomass resources are about 3.5 billion tons, the main sources of which are energy crops, agricultural waste residues, forestry waste residues and industrial and urban solid waste. The use of biomass raw materials to produce hydrogen is a method that adapts to China's national conditions and has good Hydrogen production technology route with promising development prospects. Since the raw material in some scenarios is carbon-containing biomass, this path is also regarded as a "carbon-negative" hydrogen production path, and the hydrogen produced by this path is also called "emerald hydrogen" or "super green hydrogen."

Biomass hydrogen production technology can be mainly divided into two major paths: thermochemical hydrogen production and biological hydrogen production. Thermochemical hydrogen production can be divided into three subdivided technical paths: steam vaporization, supercritical water vaporization, and biomass thermal cracking and reforming; biological hydrogen production is also called microbial degradation method and biomass fermentation hydrogen production, including direct photolysis/indirect There are various subdivided paths such as photolysis, light fermentation, dark fermentation, light-dark coupled fermentation, cell-free enzyme biotransformation, etc.

Refers to the method of converting biomass into hydrogen-rich combustible gas through thermochemical treatment and then obtaining pure hydrogen through separation. This method can produce hydrogen directly from biomass raw materials, or from intermediate products of biomass depolymerization (such as methanol, ethanol). According to different specific processes, it can be further divided into steam gasification technology, supercritical water gasification technology and biomass pyrolysis reforming technology:

Steam gasification technology: Steam gasification hydrogen production technology selects steam as the gasification agent. The purpose of gasification treatment of biomass raw materials is to remove non-flammable components such as nitrogen and water to increase the calorific value of the fuel. At the same time, removing sulfur and nitrogen can prevent their products from entering the atmosphere and reduce the mass ratio of hydrocarbon elements; this method can generally obtain the volume The disadvantage of using 40% to 60% hydrogen and high calorific value synthesis gas is that tar is produced as a by-product. Therefore, exploring cost-effective catalysts to increase hydrogen production, reduce gasification temperature, promote tar cracking and develop green tar treatment technology, reforming tar into valuable synthesis gas and hydrogen separation systems are currently the further application of this technology. 

Thermal cracking reforming technology: The principle of this technology is to indirectly heat biomass at 350 to 600°C and isolate air and oxygen (or limited oxygen), so that it can be pyrolyzed and converted into biotar, coke and gas. The hydrocarbons are further catalytically cracked to obtain hydrogen-rich gas and the gas is separated to obtain hydrogen. Under the premise of using a catalyst, the volume fraction of hydrogen in the pyrolysis gas can reach 30% to 50%. However, the tar produced during the pyrolysis process will corrode equipment and pipelines, causing a decrease in hydrogen production efficiency. The next key steps at present are the development of new economical catalysts, research and development of low-cost tar removal processes, hydrogen separation processes, etc.

Supercritical water vaporization: refers to the decomposition of biomass in supercritical water to produce H2, CO, CO2, CH4 and other gases through pyrolysis, hydrolysis, condensation and dehydrogenation. Biomass supercritical water vaporization hydrogen production technology has relatively high energy consumption. Large, the production of tar by-products and other problems. Although the raw material price of this technology is low, the operating cost and initial investment of the supercritical water system are high, and there are no large-scale demonstration projects, so it cannot be promoted for commercial use in the short term.

Biological methods can be subdivided into direct photolysis, indirect photolysis, light fermentation, dark fermentation, light-dark coupled fermentation, cell-free enzyme conversion and other subdivided paths; different technical paths have their own advantages and disadvantages, among which light and dark Coupled fermentation can not only reduce the demand for light energy to a certain extent, but also significantly increase the production of hydrogen. It is the main development direction of biological hydrogen production at present.

Foreign Representative - United Kingdom:

At the beginning of 2023, the British Department of Business, Energy and Industrial Strategy (BEIS) announced that it would invest 30 million pounds to support innovation in biomass hydrogen production technology. Specific funding directions:

Raw material pretreatment: develop low-cost, energy-saving and efficient raw material pretreatment technology to optimize biomass and waste raw materials. Including granulation technology, mechanical sorting technology, heat treatment and calcination technology, etc.;

Research and development of advanced gasification technology and its components: focus on improving the quality of syngas and improving hydrogen production efficiency. Including real-time monitoring technology, physical removal technology, chemical removal technology, catalytic and thermal tar removal technology, synthesis gas pressure swing adsorption technology, gasifier integration technology, etc.;

New biomass hydrogen production technology: Focus on developing new biomass hydrogen production technology that can be combined with carbon capture. Including anaerobic fermentation hydrogen production technology, photofermentation hydrogen production technology, wastewater treatment technology, methane reforming hydrogen production technology, pyrolysis technology, etc.;

China:

Biological hydrogen production - it has been in the laboratory stage before; in early 2023, the country's first integrated biological hydrogen production and power generation project was launched in Harbin (using biomass-waste fermentation hydrogen production technology, using agricultural waste straw, landscaping waste, Food waste, highly concentrated organic wastewater, etc. are used as fermentation substrates, and efficient anaerobic hydrogen-producing strains are used as hydrogen producers to process waste while recovering a large amount of clean energy hydrogen. The technology comes from the team of Academician Ren Nanqi of Harbin Institute of Technology) .

Thermochemical hydrogen production - mainly used for biomass or waste with low water content, such as municipal waste and industrial solid waste containing more cardboard, plastic and other substances. Domestic enterprises such as Dongfang Boiler, Datang Group and other traditional energy enterprises are deploying pyrolysis gasification to produce hydrogen. However, due to the complexity of the gas treatment process, there is currently no mature commercial operation project in China under this route. Jiman Technology, which was born out of the Chinese Academy of Sciences, is currently promoting the construction of small-scale and pilot-scale demonstration projects.

Biomass hydrogen production can effectively utilize industrial, agricultural and urban waste, but the construction location is limited by the raw material supply area and is a distributed hydrogen production path; its direct product is hydrogen-containing synthesis gas, which will contain impurities such as CO, H2S and tar. The gas needs to be further separated to obtain hydrogen before it can be used, which is more suitable as fuel or industrial raw material.

Thermochemical method: The conversion rate is fast, but it requires high equipment, catalysts, etc., and gas separation is difficult; we can focus on key breakthrough directions such as new catalysts, tar reforming and utilization, and gas separation processes and equipment.

Biological method: high yield, low cost, but many impurities; among them, light-dark coupled fermentation hydrogen production has the fastest hydrogen production efficiency and the highest substrate utilization rate, and is expected to become the mainstream application technology of biological hydrogen production in the future.

In summary, biomass hydrogen production is generally still in its early stages, and some commercial demonstrations are still concentrated in the small-scale and pilot stages. Its application scenarios are mainly as industrial fuel raw materials. This field can focus on: biological fermentation hydrogen production. Key links include the cultivation, transformation and preparation of high-performance hydrogen-producing bacteria, the light-dark coupled fermentation hydrogen production method, the pretreatment of biological hydrogen production raw materials, and hydrogen separation process equipment.

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