Hydrogen Production Technologies With Specific Reference to Biomass

Abstract

One of the environmental threats our planets is facing today is the long term changes in the earth’s temperature and climatic pattern known as Global Climate Change. The emissions of the six green house gases i.e. Carbon dioxide, Methane, Nitrous Oxide, Hydrofluoro carbons (HCFs), Perflouro carbons (PFCs), Sulfur Hexaflouride (SF₆) from human activities have influenced the global climate. In the transportation sector light vehicles are responsible for  the release of significant amount of carbon dioxide, volatile organic compound (VOC), carbon monoxide and nitrogen oxide (NOx) emissionsn . Thus efforts are made to diversify our energy supply particularly for the transportation sector and to find cleaner fuels. Hydrogen can be considered  as a clean  fuel  but as of today  it is not a primary energy source  but is considered an energy carrier. Hence it must be manufactured before it is used as a fuel. Recently there has been international attention on the development of new hydrogen technologies as a potential solution to the current fears of global warming. Fuel processing technologies convert a hydrogen containing material such as gasoline, ammonia, or methanol into a hydrogen rich stream . There are many processes for hydrogen production. Hydrogen  can be produced from carbonaceous materials mainly hydrocarbons and/or water by application of either chemical, electrical or thermal energy. It can also be produced by the partial oxidation of hydrocarbons, steam-iron process, water-gas and producer-gas processes. Biomass can also become an important source of hydrogen. Biomass as a product of photosynthesis is a renewable resource that can be used for sustainable production of hydrogen. Except for very low cost feedstocks and plants like switchgrass direct production of hydrogen from biomass by gasification/water-gas shift technology is economically unfavorable .Alternatively it can be produced by a two-stage process: fast pyrolysis of biomass to generate bio-oil; and subsequently catalytic steam reforming of the oil or its fractions to produce hydrogen. Also in the production of biodiesel from biomass by the transesterification process , glycerol is the main biomass-derived product . Now a days the worldwide trend of increasing production of bio-fuels results in an overproduction of glycerol. The hydrogen production from glycerol by the aqueous-phase reforming process at low temperatures and high pressures has been tried on various supported catalysts including Pt/Al₂O₃, Pd/ Al₂O₃. Hydrogen can also be produced by the Aqueous Phase Reforming (APR) process which generates  hydrogen-rich gas streams from biomass-derived compounds such as glycerol, sugars, and sugar alcohols.  The reaction of these oxygenated compounds takes place in a single step reactor process compared to the three or more reaction steps required for hydrogen generation conventionally carried out by non-renewable fossil fuels. The reforming of these reactions takes place in the liquid phase. Hence attempts are made to produce hydrogen through various techniques all across the globe to achieve economically viable process .  This paper reviews the technologies related to hydrogen production from  renewable biomass resources including reforming (steam, partial oxidation, autothermal,plasma, and aqueous phase) and pyrolysis.