Biomass, hydrogen from

Combustion is the direct burning of biomass in air to convert the biomass chemical energy into heat, mechanical power or electricity using equipment such as stoves, 

Thermo-chemical gasification is the conversion by partial oxidation at elevated temperatures of a carbonaceous feedstock into a low or medium energy content gas (Saxena et al., 2007). Gasification of coal is now well established, and biomass gasification has benefited from the activity in this sector and is developing rapidly. However, the two technologies are not directly comparable due to differences between the feedstocks (e.g. char reactivity, proximate composition, ash composition, moisture content, density). 

Pyrolysis is the thermal decomposition occurring in the absence of oxygen. It is always the first step in combustion and gasification processes where it is followed by total or partial oxidation of primary products. Lower process temperature and longer vapour residence times favour the production of charcoal. High temperature and longer residence time increase the biomass conversion to gas, and moderate temperature and short vapour residence time are optimum for producing liquids. 

In general, the main gaseous products from the pyrolysis of biomass are H2, C02, CO and hydrocarbon gases, whereas the main gaseous products from the gasification of biomass are H2, C02, CO and N2. It is well established that the use 

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Hydrogen from Biomass-Derived Other Intermediates.213... 

Spath, P. L. Lane, J. M. Mann, M. K. Amos, W. A., Update of Hydrogen from Biomass— Determination of the Delivered Cost of Hydrogen. NREL, Milestone Report for the U.S. Department of Energy s Hydrogen Program Process Task, Milestone Type C (Control), Golden, CO, 2001. 

Hamelinck, C. Faaij, A. P. C., Future prospects for production of methanol and hydrogen from biomass. Journal of Power Sources 2002,111(1), 1-22. 

Larson, E. D. Katofsky, R. E., Production of Methanol and Hydrogen from Biomass. Center for Energy and Environmental Studies, School of Engineering and Applied Science, Princeton University, Princeton, NJ, 1992. 

Biollaz, S. Sturzenegger, M. Stucki, S., Redox Process for the production of clean hydrogen from biomass. In Progress in Thermochemical Biomass Conversion, Seefeld, Tirol, 2000. 

A third area of hydrogen from biomass is metabolic processing to split water via photosynthesis or to perform the shift reaction by photo biological organisms. This is an area of long-term research. 

Cox, J. L. Tonkovich, A. Y. Elliott, D. C. Baker, E. G., and Hoffman, E. J. (1995). Hydrogen from Biomass A Fresh Approach. Proceedings of the Second Biomass Conference of the Americas, (NREL/CP-200-8098 CONF-9508104) August, Portland, Oregompp. 657-675. 

Figure 3.2 Summary of hydrogen production routes from biomass. (Source Milne, T.A. et al. Hydrogen from Biomass State of the Art and Research Challenges, NREL, IEA/H2/TR-02/001).

Abedi, J., Yeboah, Y.D., Howard, J., and Bota, KB. (2001) Development of a catalytic fluid bed steam reformer for production of hydrogen from biomass, 5th Biomass Conference of the Americas, Orlando, FL (Cancelled). Abstracts to be published on CD/ROM. 

For natural-gas-fuelled CHP plants, the same line of argumentation holds as for the stationary use of hydrogen from biomass. It is more reasonable to use natural gas directly than to convert it to hydrogen first and then to heat and electricity. High electrical efficiencies can be reached in the stationary sector by feeding natural gas to molten-carbonate fuel cells (MCFC) and solid-oxide fuel cells (SOFC). Molten-carbonate fuel cells have the added advantage of using C02 for the electrolyte (see also Chapter 13). 

To conclude, the generation of pure hydrogen from solid biomass is only reasonable if transportation fuel should be produced. But it is not reasonable to produce pure hydrogen from biomass for stationary heat and electricity generation. 

Hydrogen from Biomass Gasification hy Steam Reforming... 

Comparison of pyrolysis and air-steam gasification shows that the yield of hydrogen from biomass is generally higher by air-steam gasification than that by pyrolysis, because with interaction of water and char from decomposition of biomass intermediate products are formed, which leads to more hydrogen-rich gas yield by the steam reforming. 

Hydrogen from Biomass by Supercritical Water Gasification... 

Cox, J.L., Tonkovich, A.Y., Elliott, D.C., Baker, E.G., Hoffman, E.J. 1995. Hydrogen from biomass a fresh approach. Proceedings of the 2nd Biomass Conference of the Americas (NREL/ CP-200-8098 CONE-9508104) August 1995, Portland, Oregon. 

Czemik, S., Erench, R., Eeik, C., Chomet, E. 2001. Production of hydrogen from biomass derived liquids. Proceedings of the 2001 USA. DOE Hydrogen Program Review (NREL/CP 570-30535). 

Demirbas, A., Arin, G. 2004. Hydrogen from biomass via pyrolysis relationships between yield of hydrogen and temperature. Energy Sources 26 1061-1069. 

Milne, T.A., Elam, C.C., Evans, R.J. 2002. Hydrogen from biomass state of the art and research challenges 1-82. National Renewable Energy Laboratory, Golden, CO. 

Wang, D., Czernik, S., Chornet, E. 1998. Production of hydrogen from biomass by catalytic steam reforming of fast pyrolysis oils. Energy Fuels 12 19-24. 

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