ABSTRACT
Biomass is one of the renewable and potentially sustainable energy sources and has many possible applications varying from heat generation to the production of advanced secondary energy carriers. It has almost zero or very low net CO2 emission since carbon and energy are fixed during the biomass growth [1]. There are different types of technologies for con verting biomass to electricity or to a secondary fuel such as thermal conversion, chemical conversion and bio-chemical conversion [2]. However, 54thermo-chemical methods such as gasification have a great potential in producing a syngas mainly composed of H2 and CO with traces of different gases such as CH4 in different proportions [3]. The produced fuel gas can be flexibly utilized in boilers, engines, gas turbines or fuel cells [4]. Smaller scale gasification systems with internal combustion engines can now be used for thousands of hours to give reasonably high electrical efficiencies and limited emissions [5]. However, fuel cells have the potential to operate at higher electrical efficiency and with lower emissions compared with traditional power generation techniques. Fuel cells are emerging as a leading alternative technology to the more polluting internal combustion engines in vehicle and stationary distributed energy applications. In addition, the future demand for portable electric power supplies is likely to exceed the capability of current battery technology. Hydrogen-powered fuel cells emit only water and have virtually no pollutant emissions, even nitrogen oxides, because they operate at temperatures that are much lower than internal combustion engines [6]. However, even fuel cells fuelled by hydro- carbon fuels have the potential to provide efficient, clean and quiet energy conversion, which can contribute to a significant reduction in greenhouse gases and local pollution. When heat generated in fuel cells is also utilized in combined heat and power (CHP) systems, an overall efficiency of 85% in excess can be achieved [7]. Different types of fuel cells suitable for several energy applications at varying scales have been developed, but all share the basic design of two electrodes (anode and cathode) separated by a solid or liquid electrolyte or a membrane. Hydrogen (or a hydrogen-containing fuel) and air are fed into the anode and cathode of the fuel cell, and the electrochemical reactions assisted by catalysts take place at the electrodes [8]. The electrolyte enables transport of ions between the electrodes while the excess electrons flow through an external circuit to provide electrical power. Fuel cells are classified according to the nature of their electrolyte, which also determines their operating temperature, the type of fuel and a range of applications [9]. The electrolyte can be acid, base, salt or a solid ceramic or polymeric membrane that conducts ions.
