ABSTRACT
Hydrogen is expected to play a significant role in the future energy market. Hydrogen production from renewable sources, such as biomass, is currently attracting significant research efforts. Biomass-based hydrogen production technologies can be divided into two main groups: (1) thermochemical technologies, including conventional gasification, hydrothermal gasification, biomass pyrolysis followed by steam reforming of pyrolytic oils and (2) biologic technologies, including fermentation, photosynthesis, and biological water gas shift process. The hydrogen yield from conventional biomass gasification is generally affected by a variety of parameters, such as biomass type and structure, gasifying agent, temperature, pressure, steam to biomass ratio, and addition of catalysts or absorbents. Similarly, the hydrogen production performance through hydrothermal gasification is strongly influenced by the biomass properties, water temperature and pressure, and added catalysts. Biomass pyrolysis followed by steam reforming of pyrolytic oils depends on more factors as the entire process is composed of two stages. Biomass pyrolysis generally generates the maximum bio-oil yields at around 400–550°C, and heating rate, atmosphere type, and other factors also exert the influence. Compared to thermochemical technologies, biological technologies are generally of much lower energy efficiencies and hydrogen production rates, higher hydrogen production costs but excellent environmental performance. There are still challenges for each biomass-based technology to be solved to achieve large-scale hydrogen production and acceptance in the market.
