Hydrogen from pyrolysis
Although most pyrolysis processes are designed for bio-oil production, hydrogen can be produced through fast pyrolysis at high temperature and long gas residence time. In order to evaluate hydrogen production from biomass pyrolysis, extensive experimental investigations have been conducted. Agricultural residues, organic wastes, mixed biomass and synthetic polymers have been widely used for hydrogen production [34]. Fast pyrolysis processes produce 60–75 wt.% of bio-oil, 15–25 wt.% of solid char and 10–20% of gases, depending on the feedstock used [53]. With the aid of catalysts incorporated in the pyrolysis process, the quantity and quality of the gas product can be improved. Different types of catalysts were used to accelerate process reaction rate such as inorganic salts (chlorides and carbonates) [34] and [54], metal oxides [55] and [56] and nickel-based catalyst [55]. Catalyst can be placed inside the pyrolysis reactor in the layer of glass wool or it can be dry mixed with feedstock biomass.