**Highly Efficient Biomass Utilization with Solid Oxide Fuel Cell Technology**

Yusuke Shiratori1,2, Tran Tuyen Quang1, Yutaro Takahashi1,

Shunsuke Taniguchi1,3 and Kazunari Sasaki1,2,3

*1Department of Mechanical Engineering, Faculty of Engineering, Kyushu University 2International Institute for Carbon-Neutral Energy Research (WPI), Kyushu University 3International Research Center for Hydrogen Energy, Kyushu University Japan* 

#### **1. Introduction**

164 Renewable Energy – Trends and Applications

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Mankind has been consuming plants, i.e. biomass, as an energy source for living and developing on earth from the paleolithic period to early the modern period. Consumption of bio-energy does not change the atmospheric environment because carbon dioxide emitted by the use of bio-energies will be used by plants through the photosynthesis (Züttel, 2008). Since 1769 James Watt significantly improved the steam engine, invented by Thomas Savery in 1698. The steam engine was widely introduced for producing mechanical work from chemical energy of fuels, i.e. mineral coal and wood. More practical heat engines, external and internal combustion engines, have served for developing of human society for almost two and a half centuries. Since the Otto-Langen engine was first introduced in 1867, human society has developed using the internal combustion engines (IC engines), which nowadays are used worldwide for transportation, manufacture, power generation, construction and farming. However, large consumption of fossil fuels may bring about environmental pollution and climate change.

Fuel cells are electrochemical devices that convert chemical energy of fuels directly into electrical energy without the Carnot limitation that limit IC engines. Even in the smallest power range of less than 10 kW, fuel cells exhibit electrical efficiencies of 35-50 %LHV (lower heating value), while being silent, whereas engines and microturbines show low electrical efficiency of 25-30%LHV and high levels of noise. Therefore, the fuel cell which can be operated with very low environmental emission levels, is regarded as a promising candidate for a distributed power source in the next generation. Although most fuel cells operate with hydrogen as a fuel, solid oxide fuel cells (SOFCs) operated in a high temperature range between 600 and 900 oC accept the direct use of hydrocarbon fuels. Hydrocarbon fuels directly supplied to SOFCs are reformed in the porous anode materials producing H2-rich syngas, which is subsequently used to generate electricity and heat through electrochemical oxidation (Steele & Heinzel, 2001; Sasaki & Teraoka, 2003). This type of SOFC, so called internal reforming SOFC (IRSOFC), enables us to simplify the SOFC system. Electrochemical performances of IRSOFC have been reported for gaseous and liquid fossil fuels such as methane (Park et al., 1999), propane (Iida et al., 2007), n-dodecane (Kishimoto et al., 2007), synthetic diesel (Kim et al., 2001), crude oil and jet fuel (Zhou et al., 2004). Highly efficient fuel cells operated by fossil fuels can certainly contribute to the suppression of environmentally harmful emissions, but in view of exhaustion of fossil resources, the utilization of renewable bio-energies should be more promoted. Direct feeding of biofuels to SOFC gives an environmental-friendly, compact and cost-effective energy conversion system. Biogas derived primarily from garbage is one of the most attractive bio-energies for SOFC (Van herle et al., 2004a; Shiratori et al., 2008, 2010a, 2010b). Recently, Shiratori et al. (2010) has demonstrated the stable operation of an IRSOFC operating on non-synthetic biogas over one month using an anode-supported button cell. On the other hand, the use of liquid biofuels is also attractive due to their easy storage and transportation with high energy density. Tran et al. (2011) has demonstrated the stable operation of an IRSOFC operating on practical palm-biodiesel over 800 h, also using an anode-supported button cell.

In this chapter, performances of IRSOFCs operating on biofuels are summarized and roadblocks to overcome for the realization of this type of highly-efficient carbon-neutral fuel cell are mentioned.
