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Utilization of oil palm empty fruit bunches under bio-refinery concept for

ethanol hydrogen and fuel pellet production

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Rattana Jariyaboon , Sompong O-Thong , Sureewan Sittijunda , Prawit Kongjan 1,*

1 Department of Science, Faculty of Science and Technology, Prince of Songkla University, Pattani, 94000, Thailand
2 International College, Thaksin University, Songkhla, 90000, Thailand
3 Faculty of Environment and Resource Studies, Mahidol University, Salaya, Nakhon Pathom, 73170, Thailand
*Corresponding author: kprawit.kongjan@gmail.com
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Abstract
Oil palm empty palm bunches (OPEFB) was feasibly investigated to utilize under bio-

refinery concept by using products generated from hydrothermal pretreatment of OPEFB to
producing ethanol fuel pellet and hydrogen. Under optimum conditions of solid-liquid ratio

1:11.40 (w/v), temperature 195 °C and time 19 min, hydrothermal pilot scale with semi-
continuous feed could provide removal efficiencies of 79%, 53%, and 86 wt% for

hemicellulose, lignin, and potassium, respectively. Pretreated OPEFB was subsequently used

for ethanol production carried out in the CSTR reactor with semi-simultaneous saccharification
and fermentation (SSSF) for 72-hr at initial solid loading of 10 w/v% with Cellic® CTec2 50

FPU/ g substrate and with 10 v/v% of K. marxianus TISTR 5925 at 45 C added after 12-hr
°
enzymatic hydrolysis. Ethanol yield achieved was 73.37 % of the theoretical yield. Pretreated
OPEFB adjusted to have initial moisture content of 20 wt% and mixed with tapioca starch 10

wt% could be pelletized successfully with satisfactory characteristics. Xylose rich hydrolyzate

solution obtained from OPEFB hydrothermal pretreatment could be converted to hydrogen
by dark fermentation process, with rate of approx. 0.21 L H /L·d and yield of 1.51 mol H /mol
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xylose. Subsequently, dark fermentation effluent was converted to hydrogen by microbial

electrolysis cell with a rate of 1,324 mL H /L·D and a yield of 33.0 mmol H /g COD. The
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experimental results obtained from this research project illustrate the approaches and
feasibility of utilizing OPEFB under bio-refinery concept to produce high-value fuel and can

be further scaled-up to industrial level.

Keywords: hydrothermal pretreatment, yeast fermentation, pelletization, dark fermentation,
microbial electrolysis