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Journal of Engineering Science and Technology Special Issue on SOMCHE 2014 & RSCE 2014 Conference, January (2015) 1 - 8 © School of Engineering, Taylor’s University

1

BIO-SYNGAS DERIVED FROM INDONESIAN OIL PALM EMPTY FRUIT BUNCH (EFB) USING MIDDLE-SCALE GASIFICATION

YANO S. PRADANA1, ARIEF BUDIMAN

1,2*

1Chemical Engineering Department, Faculty of Engineering, Gadjah Mada University,

Jalan Grafika No. 2, Kampus UGM, 55281, Yogyakarta, Indonesia 2 Center for Energy Studies, Gadjah Mada University,

Sekip K1-A Yogyakarta, 55281, Indonesia

*Corresponding Author: [email protected]

Abstract Indonesia now is the largest producer of palm oil in the world. Over seven

million hectares in the cultivation and more than 400 palm oil mills in

operation. The major biomass by product from the palm oil industry is empty fruit bunches (EFB) that have a great potency as basic feedstock used for

alternative energy. We proposed new technology that combined pyrolysis-

catalytic cracking-gasification processes in a whole system, namely as

integrated autothermal technology. By using this technology, energy supplied

to the system can be reduced significantly. In this study, Indonesian oil palm

empty fruit bunches (EFB) was converted to alternative energy using a middle-

scale gasification. The products werebio-syngas, bio-oil, water-phase and char.

The effects of various gasification temperatures and air volumetric flow rateson

the yields of the products were investigated. The temperature of gasification

and air volumetric flow rate were varied in the range of 500-700 °C and 29-55

ml/second, respectively. Product yields were found to be significantly influenced by the gasification conditions. Under the experimental conditions,

the maximum bio-syngas yield was 45.50 %wt obtained at 700 °C, with air

volumetric flow rate of 41 ml/second.

Keywords: Empty fruit bunch, Oil palm, Integrated-auto thermal technology,

Middle-scale gasification, Bio-syngas.

1. Introduction

Ever since the lack of petroleum resources began with the global energy crisis and

the increasing concerns of rising greenhouse gas emissions, considerable attention

has been focused on the development of alternative fuels. Alternative fuels should

2 Y. S. Pradana and A. Budiman

Journal of Engineering Science and Technology Special Issue 8 1/2015

be technically feasible, competitive in price, environmental friendly, abundantly

available and having sustainability character [1]. Among the available alternative

energy sources, biomass has drawn significant attention since it holds various

advantages compared with fossil fuel in terms of renewability, non-toxicity and

environmental friendly [1]. From these advantages, biomass is a potential energy

resource and there are several pathways, such as physical, thermal, chemical and

biological, to generate energy. Unlike fossil fuel, biomass as renewable fuel has

advantage in maintaining a closed carbon cycle with no net increase in

atmospheric CO2 levels [2]. Biomass takes carbon out of the atmosphere while it

is growing and returns it as it is burned. The increase of CO2emission from fossil

fuels has a dominant influence on the atmospheric CO2 concentration that

eventually results in rising global temperature and sea level [3]. Moreover, its

negligible sulphur and nitrogen are the main advantages of using biomass for

preventing the acid rain [4].

Indonesia is currently the largest producer and exporter of palm oil

worldwide. According to data from the Indonesian Ministry of Agriculture [5],

the total area of oil palm plantations in 2012 is around nine million hectares, a

number which is twice as much as in the year 2000 when around four million

hectares of Indonesian soil was used for palm oil plantations. This number is

expected to increase to 13 million hectare by 2020.Based on data of Badan Pusat

Statistik (Statistic Indonesia) in 2013 [6], Indonesia produced 27 million tons of

oil palm to produce crude palm oil. This process generates 30-40% of biomass

waste such as oil palm empty fruit bunch (EFB), palm kernel shell and mesocarp

fiber at palm oil mills.

The oil palm EFB is one of the high carbon content biomass, which is

currently used as a combustion boiler fuel with very low efficiency. It contains

cellulose, hemicellulose and lignin which have high carbon and hydrogen

contents, comparable with hard wood [1]. One of the promising technologies

utilizing the biomass is biomass gasification [7]. By combining pyrolysis-

catalytic cracking-gasification processeses in a whole system, the new

technology have been introduced for utilizing biomass waste for producing

alternative energy (bio-gasoline, bio-kerosie and bio-solar), namely as

integrated autothermal technology [8]. By using this technology, energy

supplied to the system can be reduced significantly.

Gasification is a thermo-chemical partial oxidation process in which

carbonaceous substances (biomass, coal and plastics) are converted into gas in the

presence of a gasifying agent (air, steam, oxygen, CO2 or a mixture of these) [9].

The gasification of biomass allows the production of a bio synthesis gas or ‘bio-

syngas”, consisting primarily of H2, CO, CH4, CO2 and N2 [10]. It also produces

solids (such as char, ash) and condensable products like tars and oils [3]. Basu

[11] illustrates the sequence of gasification steps as in Fig. 1.

Gasification occurs in a set of four steps: drying, pyrolysis, oxidation and

reduction [12]. Drying process removes water in the biomass and converts it into

steam. The steam produced by drying process can lead the thermal decomposition

of biomass into bio-syngas. Pyrolysis is the chemical decomposition through the

application of heat in the absence of oxygen [13]. Basu [11] explains that during

the pyrolysis process, biomass converted to liquid product (also known as bio-oil

or tar), a solid residue (also known as char) and several light gaseous compounds

Bio-syngas Derived from Indonesian Oil Palm Empty Fruit Bunch (EFB) . . . . 3


(e.g. carbon dioxide, carbon monoxide, hydrogen and light hydrocarbon).

Oxidation process takes place between oxygen in the air and biomass, producing

carbon dioxide and water. Reduction process is a high temperature chemical

reaction, occurring in the absence of oxygen. The main reactions in the reduction

process are boudouard reaction, steam reaction, water-shift reaction and

methanation. These reactions are endothermic reaction which needs the energy to

be occurred, except methanation.

Fig. 1. Schematic steps of biomass gasification.

Gasification of biomass needs gasifying medium. Gasifying medium reacts

with solid carbon and heavier hydrocarbons to convert them into low-molecular-

weight gases like CO and H2, as primary product of bio-syngas. The main

gasifying medium used for gasification are oxygen, steam and air [11]. Air has

been widely used as the oxygen source for gasification because steam requires

additional energy cost for increasing temperature [14] and oxygen requires

oxygen production equipments which increases the cost of gasification process

[7]. Couto et al. [12] studied on gasification process, the use of steam or oxygen

as gasifying agent increases remarkably the production of hydrogen and carbon

monoxide reflecting a significant increase of the syn-gas heating value.

There are several process parameters which may affect the gasification

process. In this study, Indonesian oil palm EFB was gasified in a midle-scale

of gasification to produce bio-syngas. The effects of various gasification

temperatures and air volumetric flow rateson the yields of the products

were investigated.

2. Experimental

2.1. Feedstock properties

The oil palm EFB was collected from palm oil mill in Riau, Indonesia. Samples

collected were relatively dry and having 13.3%wt moisture. After collecting, it

was sun-dried for two days in order to remove unbound moisture. Key properties

of EFB, both measured for this research and from the literature, are given in Table 1.



Table 1. Properties of EFB (%wt).

Component/properties Literature value [15] Measured

Moisture 7.95 13.30

Elemental analysis

Carbon 49.07 55.53

Hydrogen 6.48 5.54

Nitrogen 0.70 2.55

Sulphur <0.1 0.06

Oxygen 38.29 35.28

Potassium 2.00 0.33

2.2. Gasification experiment

Gasification of the oil palm EFB was carried out using batch reactor. The

following equipment after gasifier was condenser. It was for condensing gas from

reactor to be liquid product. The reactor was heated by LPG burner. The

temperature of the reactor was determined by inserting a thermocouple in the

middle of the reactor. The experimental rig consisting of the bio-oil condensation

system is illustrated in Fig. 2.

The oil palm EFB feedstock was weighted and introduced into the reactor. The

burning of the reactor and the condensation system of bio-oil were then started.

The whole experiment must be held for either minimum of 1 hour or until no

further significant release of gas was observed.During gasification, gas produced

from the reactor was streamed into cyclone, as the first condensation system. The

liquid product collected in the cyclone was transferred into flask. The cyclone-

uncondensed gas was streamed into two pipe-condensers, as the second

condensation system. The liquid product from second condensation system was

taken in the end of second pipe-condenser and transferred into flask. The bio-oil

was then physically separated from liquid product by separation funnel. The

upper liquid was bio-oil phase and the bottom liquid was water phase.

Meanwhile, the uncondensed-gas was then burned in burner. It is used for

substituting LPG as fuel in gasification process. The amount of the uncondensed-

gas was calculated from the material balance.

2.3. Parameter definition and method of data processing

The parameters determined in this study are bio-syngas, bio-oil and char yield.

The definitions of the parameters are as follows:

• Bio-syngas yield

�� =��

�� 100% (1)

• Bio-oil yield

�� =��

�� 100% (2)



• Char yield

�� =��

�� 100% (3)

Fig. 2. Schematic diagram of the gasification system.

2.4. Effect of Temperature

The first series of experiments was performed to determine the effect of the

temperature on gasification yields. The average heating rate was at 12 oC.min

-1 to

final temperature of 500, 550, 600, 650 and 700 oC with 1000 g of oil palm EFB

feedstock and 41 ml per second of air volumetric flow rate.

2.5. Effect of Volumetric Flowrate

The second series of experiments was performed to determine the effect of the air

volumetric flow rate on gasification yields. The air volumetric flow rate of 29, 41

and 55 ml per second were studied. The final gasification temperature was

maintained at 650 oC and feedstock was 1000 g.

3. Results and Discussion

The effects of temperature and air volumetric flow rate on the product yields were

analysed in this paper.



3.1. Effect of temperature

Gasification temperature is one of the most important operating parameters which

affect both bio-syngas composition and carbon conversion throughout the

gasification reactions. The effect of final gasification temperature on product

yields is shown in Fig. 3. Started at the lowest gasification temperature of 500 oC,

decomposition of oil palm EFB was significant as gas was the major product. At

this condition, the gas yield was 40.80 %wt of feedstock. It tended to increase by

increasing final gasification temperature. Thus, the maximum gas yield was

obtained at 700 oC in the value of 45.50 %wt of feedstock. Products of water, bio-

oil and char also presented in Fig. 3.

Fig. 3. Gasification product yields at different temperature.

The char yield was obtained at the range 23-25 %wt of feedstock over the

temperature range of 500 to 700 oC. The bio-oil yields reached a maximum value

of 10.94 %wt of feedstock at the lowest gasification temperature of 500 oC. It

tended to decrease by increasing final gasification temperature. Alaudin et al. [7]

studied on gasification of lignocellulosic biomass using fluidized bed reactor and

Mondal et al. [16] studied on carbonaceous materials respectively, indicated the

similar trend of gas and bio-oil yields. High temperature improves carbon

conversion and reforming of tars which result in high gas yields [7]. The higher

temperature gives the more energy into gasifier. This additional energy improves

product formation in endothermic reactions whereas they favor reactants in

exothermic reactions. Besides, high temperature will crack bio-oil into lighter

hydrocarbon in liquid phase and gas phase. As the result, the yield of bio-oil

tended to decrease by increasing final gasification temperature.

3.2. Effect of air volumetric flow rate

The effect of air volumetric flow rate on product yields is shown in Fig. 4. The

gas yields reached a maximum value of 45.07 %wt of feedstock obtained at the

air volumetric flow rate of 41 ml/second. Then, the gas yields decreased to 44.42

%wt of feedstock obtained at the air volumetric flow rate of 55 ml/second. The

higher air volumetric flow rate will decrease retention or contact time between



oxygen and biomass in the reactor. Thus, they are not reacting enough to produce

bio-syngas. Besides, air volumetric flow rate into the reactor should be limited.

The excess amount of oxygen will moves the process from gasification to

combustion and the major product is flue gas instead of fuel gas [11]. Then, the

flue gas or the combustion product contains no residual heating value. Chang et

al. [14] studied on gasification of α-cellulose using fluidized bed reactor over the

temperature of 700 oC and equivalent ratio of the air fed to the gasifier of 0.2. The

gas yield was 20.4 %wt of feedstock at this condition.

The char yield was obtained at the range 24-26 %wt of feedstock over the air

volumetric flow rate variation. The maximum bio-oil yield was 9.76%wt of

feedstock obtained at the air volumetric flow rate of 29 ml/second.

Fig. 4. Gasification product yields at different air volumetric flow rate.

4. Conclusions

Gasification is thermal decomposition process producing bio-syngas, as the main

product. Bio-syngas produced from this process can be used as alternative energy

either directly or in the form of bio-methane by catalytic methanation.

Gasification temperature and air volumetric flow rate are the important operating

parameters which affect gasification process. In this paper, gasification of

Indonesian oil palm empty fruit bunches (EFB) was performed in a batch reactor.

The maximum bio-syngas yield was 45.50 %wt obtained at 700 °C, with air

volumetric flow rate of 41 ml/second. The maximum char yield was 25.30%,

obtained at 650oC, with air volumetric flow rate of 29 ml/second. Meanwhile, the

maximum bio-oil yield was 10.94%wt, which could be achieved at 500°C, with

air volumetric flow rate of 41ml/second.

Acknowledgement

The authors would thank for the financial support for this study from the Ministry

of Education and Culture, Indonesia by MP3EI (Master Plan for Acceleration and

Expansion on Indonesia’s Economic Development) Program.



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