The thermo-chemical processes for biomass treatment include combustion, gasification and pyrolysis. Pyrolysis converts biomass to mainly liquid fuels e.g. bio-oil. The yields of products depend on biomass composition, heating rate, pyrolysis temperature and residence time in the pyrolysis reactor.

Hydrogen is considered to be an ideal energy carrier for the future, which contributes to reduction of energy-linked environmental impacts, including global warming due to anthropogenic carbon emissions, mobile source emissions e.g. CO, NO, SO2 and NMHC (non-methane hydrocarbons) and particulates. H2 can be produced as a storable clean fuel from primary energy sources e.g. solar, wind, hydro, geothermal, nuclear, and from biomass as well. H2 has the unique feature of upgrading biomass and waste effluents to common liquid and gaseous hydrocarbons, thus providing flexible, sustainable energy source. Both photo-fermentation and dark fermentation processes can yield H2, and the most important advantage of such processes is the use of renewable energy sources as substrates.