**Air Gasification of Malaysia Agricultural Waste in a Fluidized Bed Gasifier: Hydrogen Production Performance**

Wan Azlina Wan Ab Karim Ghani1,2, Reza A. Moghadam1 and Mohamad Amran Mohd Salleh1,2

*1Department of Chemical and Environmental Engineering, The Universiti Putra Malaysia, Serdang, Selangor, 2Green Engineering and Sustainable Technology Lab, Institute of Advanced Technology(ITMA), Universiti Putra Malaysia, Serdang, Selangor, Malaysia* 

### **1. Introduction**

226 Sustainable Growth and Applications in Renewable Energy Sources

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Recently, biomass gasification technology to produce hydrogen-rich fuel gas is highly interesting possibilities for biomass utilization as sustainable energy (McKendry, 2002). Hydrogen production from biomass gasification has many advantages as secondary renewable energy source as it is the universe's most abundant element, clean fuel has the potential to serve as renewable gaseous and liquid fuel for transportation vehicles. As a fuel, hydrogen is considered to be very clean as it releases no carbon or sulfur emissions upon combustion. The energy contained in hydrogen on a mass basis (120 MJ/kg) is much higher than coal (35 MJ/kg), gasoline (47 MJ/kg) and natural gas (49.9 MJ/kg). Additionally, the most important advantage for all the living beings is that when it is burned, hydrogen produces non toxic exhaust emissions. Clearly, the emissions from hydrogen combustion contain no carbon monoxide (CO), carbon dioxide (CO2) and unburned hydrocarbons (Veziroglu et al., 2005). Using biomass as an energy source can reduce the greenhouse gas emission that causes global warming which is a negative effect of using fossil fuels as an energy source.

In Malaysia, more than 2 million tonnes of agricultural wastes are produced annually and potentially an attractive feedstock for producing energy as the usage contributes little or no net carbon dioxide to the atmosphere. Major agricultural products are oil palms, sawlogs, paddy and tropical fruits. The palm oil sector is the biggest producer and hence the major contributor to the agricutural residues generation in Malaysia. The oil-palm solid wastes (including shell, fibre and Empty Fruit Bunch (EFB)) are abandoned materials produced during palm oil milling process. For every ton of oil-palm fruit bunch being fed to the palmoil refining process, about 0.07 tons of palm shell, 0.146 tons of palm fiber and 0.2 tons of EFB are produced as the solid wastes. Bagasse which is the matted cellulose fibre residue from sugar cane that has been processed in a sugar mill were produced about 3×105T per year in 1999. Despite the decreasing acreage, coconut still plays an important role in the

Air Gasification of Malaysia Agricultural Waste in a

**1.1 Hydrogen fuel** 

delivery is developed.

reactions:

**1.2 Biomass gasification** 

Fluidized Bed Gasifier: Hydrogen Production Performance 229

Technology development for conversion of waste feedstock to hydrogen has an economical potential. Depletion of fossil fuel source such as oil, gas and coal is going to become the biggest problem in the near future. Therefore, hydrogen fuel from the biomass waste is the best supersede for fossil fuels. Hydrogen is not widely used today but it has a great potential as an energy carrier such as fuel cell that can be applied to power cars and factories and also for home usages in the future. In comparison with fossil fuels, 9.5 kg of hydrogen

Hydrogen has the highest energy content of any common fuel by weight (about three times more than gasoline). Hydrogen is an odorless, tasteless, colorless and non-poisonous gas. It is a renewable resource found in all growing things. Hydrogen is an important raw material for chemical, petroleum and agro-based industries. The demand for hydrogen in the hydrotreating and hydrocracking of crude petroleum is steadily increasing (Min et al., 2005). Hydrogen is catalytically combined with various intermediate processing streams and is used in conjunction with catalytic cracking operations to convert heavy and unsaturated compounds to lighter and more stable compounds. Large quantities of hydrogen were used to purify gases such as argon that contain trace amounts of oxygen. Furthermore, in the food and beverages industry, hydrogen was used for hydrogenation of unsaturated fatty acids in animal and vegetable oils, to produce solid fat and other food products. While in manufacturing of semi conducting layers in integrated circuits, hydrogen were used as a carrier gas. The pharmaceutical industries use hydrogen to make vitamins and other pharmaceutical products. Hydrogen is mixed with inert gases to obtain a reducing atmosphere that is required for many applications in the metallurgical industry such as heat

In 2005, the overall U.S. hydrogen market is estimated at \$798.1 million and it is expected to rise to \$1,605.3 million for U.S. and \$740 million for European in 2010 (Keizai, 2005). However, hydrogen production is not enough to uphold this value. The hydrogen technology had been intensively studied to find a variety of hydrogen source with different treatment processes because hydrogen has great potential as an environmentally clean energy fuel and as a way to reduce reliance on imported energy sources. In Asian region, the biomass from agriculture sector is the largest source of hydrogen production. Many experts predict that hydrogen will eventually power tomorrow's industries and thereby may replace coal, oil and natural gas. However, it will not happen until a strong framework of hydrogen production, storage, transport and

According to Xiao et al. (2007), it is generally reported by different authors that the process of biomass gasification occurs through main three steps. At the first step in the initial heating and pyrolysis, biomass is converted to gas, char and tar. Homogeneous gas-phase reaction resulted in higher production of gaseous. High bed temperature during this phase allowed further cracking of tar and char to gases. Second step is tar-cracking step that favours high temperature reactions and more light hydrocarbons gases such as Hydrogen (H2), carbon monoxide (CO), carbon dioxide (CO2) and methane (CH4). Third step is char

The gasification mechanism of biomass particles might be described by the following

produce energy equivalent to that produced by 25 kg of gasoline (Mirza et al., 2009).

treating steel and welding (Delgado et al., 1997 and Dupont et al., 2008).

gasification step that is enhanced by the boudouard reaction.

socio-economic position of the Malaysian rural population that involves 80,000 households. About 63% of coconut production, coconut fronds and shells represent the largest amount as residues (about 8%) (Ninth Malaysia Plan 2006-2010). Table 1 summarize the estimations of the current and potential selected agicultural wastes (biomass) utilizations in annual energy productivity in Malaysia.

Thermo-chemical conversion processes, including gasification, pyrolysis and combustion have been proven the best available technology to convert these renewable materials into valuables fuel (hydrogen) and fine chemical feedstock. However gasification process offers technologically more attractive and useful options for medium and large scale applications due to presence of non–oxidation conditions and lower green house gases emission. Fluidized bed gasifier is proven to be a versatile technology capable of burning practically any wastes combination with low emissions. The significant advantages of fluidized bed gasifier over conventional gasifiers include their compact furnaces, simple designs, effective gasification of wide variety of fuels, relatively uniform temperatures and ability to reduce emissions of carbon dioxide, nitrogen oxides and sulfur dioxides.


Table 1. Estimates of the energy productivity and biomass production and utilization (Ninth Malaysia Plan 2006-2010)
