Hydrogen from biomass: state of the art and research challenges (2002)

The report was prepared for the International Energy Agency (IEA) Agreement on the Production and Utilization of Hydrogen, Task 16, Hydrogen from Carbon-Containing Materials. Hydrogen's share in the energy market is increasing with the implementation of fuel cell systems and the growing demand for zero-emission fuels. Hydrogen production will need to keep pace with this growing market. In the near term, increased production will likely be met by conventional technologies, such as natural gas reforming. In these processes, the carbon is converted to CO2 and released to the atmosphere. However, with the growing concern about global climate change, alternatives to the atmospheric release of CO2 are being investigated. Sequestration of the CO2 is an option that could provide a viable near-term solution. Reducing the demand on fossil resources remains a significant concern for many nations. Renewable-based processes like solar- or wind-driven electrolysis and photobiological water splitting hold great promise for clean hydrogen production; however, advances must still be made before these technologies can be economically competitive. For the near-and mid-term, generating hydrogen from biomass may be the more practical and viable, renewable and potentially carbon-neutral (or even carbon-negative in conjunction with sequestration) option. Recently, the IEA Hydrogen Agreement launched a new task to bring together international experts to investigate some of these near- and mid-term options for producing hydrogen with reduced environmental impacts. This review of the state of the art of hydrogen production from biomass was prepared to facilitate in the planning of work that should be done to achieve the goal of near-term hydrogen energy systems. The relevant technologies that convert biomass to hydrogen, with emphasis on thermochemical routes are described. In evaluating the viability of the conversion routes, each must be put in the context of the availability of appropriate feedstocks and deployment scenarios that match hydrogen to the local markets. Co-production opportunities are of particular interest for near-term deployment since multiple products improve the economics; however, co-product development is not covered in this report. Biomass has the potential to accelerate the realization of hydrogen as a major fuel of the future. Since biomass is renewable and consumes atmospheric CO2 during growth, it can have a small net CO2 impact compared to fossil fuels. However, hydrogen from biomass has major challenges. There are no completed technology demonstrations. The yield of hydrogen is low from biomass since the hydrogen content in biomass is low to being with (approximately 6% versus 25% for methane) and the energy content is low due to the 40% oxygen content of biomass. Since over half of the hydrogen from biomass comes from splitting water in the steam reforming reaction, the energy content of the feedstock is an inherent limitation of the process . The low yield of hydrogen on a weight basis is misleading since the energy conversion efficiency is high. However, the cost for growing, harvesting, and transporting biomass is high. Thus even with reasonable energy efficiencies, it is not presently economically competitive with natural gas steam reforming for stand-alone hydrogen without the advantage of high-value co-products. Additionally, as with all sources of hydrogen, production from biomass will require appropriate hydrogen storage and utilization systems to be developed and deployed. The report also looked at promising areas for further research and development. The major areas for R,D and D are: feedstock preparation and feeding; gasification gas conditioning; system integration; modular systems development; valuable co-product integration; and larger-scale demonstrations. These are in addition to the challenges for any hydrogen process in storage and utilization technologies.