Hydrogen production from the thermochemical conversion of biomass: issues and challenges
Hydrogen production from thermochemical conversion has been considered the most promising technology for the use of biomass, and some novel methods are also being developed for low cost and high efficiency. This review presents the recent progress in the studies on hydrogen production from different kinds of biomass by pyrolysis, gasification and steam reforming without and/or with chemical-looping technologies. Considering potential applications, the Ni-based catalysts made of cheap and earth-abundant elements are especially important for the economically viable hydrogen production from biomass by thermochemical conversion, and can also effectively be compensated for and modified, to some extent, by using extremely low noble metal loading for retaining high catalytic activity, high coke resistance and long-term stability. The catalyst modification strategies of adding other metals, minimizing Ni particle sizes and improving the supports are highlighted. The sorption-enhanced steam reforming (SESR) and chemical looping steam reforming (SE-CLSR) processes with in situ CO2 removal using different reactors have been considered to change the normal equilibrium limits of the water–gas shift (WGS) reaction, and thus increase feedstock conversion and process performances. The auto-thermal operating conditions and CO2 capture during hydrogen production can be achieved by chemical looping processes with cyclic oxidation–reduction of oxygen carriers (OCs). This paper discusses the related issues, challenges and prospects, along with the possible solutions in order to help in the development of efficient hydrogen production from the thermochemical conversion of biomass.