Steam Gasification of Coffee Husk in Bubbling Fluidized Bed Gasifier Sileshi Kore, Abebayehu Assefa Mechanical Engineering Department Addis Ababa University Addis Ababa, Ethiopia e-mail: {sileshikore, abebayehuassefa}@yahoo.com Mayerhofer Matthias, Hartmut Spliethoff Institute of Energy System Technical University of Munich Munich, Germany e-mail: {m.mayerhofer, splithoff}@tum.de Abstract- Currently, the worldwide demand for fossil fuel is increasing rapidly and, at the same time, known resources are diminishing. In particular, energy resources, such as oil and natural gas, are almost depleted in some parts of the world. In addition, the fact that the climate changes are more severe than before has increased the demand for renewable energy resources. Thus, energy from biomass is one of the potential renewable energy options. The availability of biomass, combined with the recent development of technologies to use it efficiently, with low level of emission, promise to make biomass an increasingly attractive fuel option. Coffee husk is an agricultural waste in coffee processing industries in different parts of Ethiopia that has the potential of exploiting energy via thermo-chemical conversion such as gasification. However, the characteristic properties of this material with regard to thermo-chemical conversion technologies are missing in literature. This study focuses on the experimental investigating of coffee husk in bubbling fluidized bed gasifier. The performance parameters that were investigated during the experiment were tar content and gas composition. The study findings show that the tar content of coffee husk gasification is not disturbing the smooth operation of the gasifier and the gas composition observed was good as compared to wood pellet. Therefore, coffee husk will be promising feedstock in fluidized bed gasification. Keywords-coffee husk; tar-content; gas composition; fluidized bed; gasification. I. INTRODUCTION As an agricultural country, Ethiopia produces considerable amount of biomass each year. Most of biomass has been utilized for domestic energy purpose, mainly by direct combustion (which converts solid biomass into heat). On the contrary, coffee husk from coffee processing industries is not used as a fuel in most cases due to the poor handling of coffee husk to be used as domestic fuel. However, gasification, which converts solid biomass into fuel gas containing CO and H 2 or so-called synthesis gas, has to be considered as a promising alternative owing to a number of advantages. In the southern part of Ethiopia almost 171,000 tons of processed coffee is supplied to the international market per year. During the process, more than 20,000 tons of residue coffee husk is disposed of. This represents a very good potential for biomass energy. Apart from gasification for heat production, biomass gasification for electricity or combined heat and electricity production especially at small scales has drawn great attention as a more efficient and economical option compared to conventional combustion steam cycle in Thailand [1]. Unlike air gasification, steam gasification requires an external heat source if steam is used as a sole gasifying agent. Even though using a mixture of steam and air as a gasifying agent is common technology, in this experimental work, the air is used to facilitate the flow of coffee husk. In addition, it is assisted by gravity, since the feed is at the top of the gasifier. Also, the oxygen in the air will help to provide some amount of energy due to the exothermic nature of burning biomass. The elevated temperature will help in the de-volatilization process of biomass to produce various gases. Steam will react with carbon monoxide to produce hydrogen and carbon dioxide. The coffee husk is processed in an atmospheric bubbling fluidized bed reactor. Because fluidized beds can handle a large variety of feedstocks, they are well suited for this application [2]. The motivation of this study is to investigate the extent to which the gas quality (tar and gas) can influence the operation of the gasifier using coffee husk as a feedstock as compared to that of wood pellet from published data at the same operating conditions. The present work is organized as follows. The introduction part includes some overview of the availability of raw materials and available technologies to use coffee husk as renewable energy option. The methodology part describes experimental facilities and works that have been conducted at the Institute of Energy System, Technical University of Munich (IES TUM). In the result and discussion part, we present the findings of our experiments. Finally, conclusions are drawn. Figure 1. Wood pellets 17 Copyright (c) IARIA, 2013. ISBN: 978-1-61208-261-5 BIONATURE 2013 : The Fourth International Conference on Bioenvironment, Biodiversity and Renewable Energies