Oil palm empty fruit bunch (OPEFB) is one of the prominent lignocellulosic wastes from the oil palm industry, and it has the potential for feedstock in biobased products. However, delignification must be applied. This study investigated the effect of microwave-assisted alkaline pretreatment of OPEFB by using response surface methodology with Box-Behnken design (BBD) to find the optimum pretreatment conditions. OPEFB (30-mesh) was treated with various concentrations of aqueous sodium hydroxide. The effect of three variables, microwave power (280840 W), NaOH concentration (13% w/v), and reaction time (39 min), was evaluated to improve lignin removal. The quadratic model indicated that microwave power of 832.9 W, NaOH concentration of 2.7% (w/v), and a reaction time of 8.9 min resulted in the highest lignin removal: 88.10%. FTIR and SEM analysis was also conducted on the untreated and treated OPEFB to evaluate the effectiveness of the pretreatment. These results showed that microwave-assisted alkaline pretreatment of OPEFB could effectively remove the lignin under a relatively short time period and low alkaline concentration.

Oil Palm Empty Fruit Bunch (OPEFB) is one of the main types of solid waste which is continuously produced from palm oil mills. OPEFB contains lignocellulose to which the hemicellulose can be converted into furfural, an important precursor material used for producing high value chemicals, by means of a hydrolysis reaction. This process must be preceded by pretreatment in order to disrupt compact lignocellulose structure of OPEFB and to expose hemicellulose for further hydrolysis reaction. In this study, the optimum pretreatment conditions of OPEFB for hemicellulose recovery by microwave assisted alkali method with aqueous sodium hydroxide is evaluated by using response surface methodology (RSM) based on three-level three-factorial Box-Behnken design. OPEFB powder with different size ranging from 30 - 40 mesh was immersed into sodium hydroxide solution at 1 : 10 solid-liquid ratio. Variations of sodium hydroxide concentrations (1; 2; 3%), microwave power (280; 560; 840 Watt), and radiation time (3; 6; 9 minutes) were examined in this study. The quadratic model showed that pretreatment at 593.43-Watt and 1.15 % sodium hydroxide concentration for 5.99 minutes recovered the highest hemicellulose of OPEFB i.e. 23.22%.

Formic acid is the simplest carboxylic acid which has myriad applications in food, textiles, agriculture, pharmaceutics, and chemicals. Formic acid can be synthesized from hydrolysis of lignocellulosic biomass. Oil palm empty fruit bunch (OPEFB) is lignocellulosic biomass produced by oil palm industries to which cellulose content has potential for conversion into formic acid by hydrolysis. We investigated effects of three parameters in acid-catalysed hydrolysis reaction of OPEFB such as reaction time (20, 40, 60 minutes), temperature (140, 160, 180 °C), and H2SO4 concentration (0.3; 0.5; 0.7 M) and optimized them to obtain maximum formic acid concentration by using response surface methodology. Microwave assisted alkaline pretreatment of OPEFB sample under microwave radiation at 840 Watt for 9 minutes with 2% NaOH concentration was done prior to hydrolysis. The pretreatment was effective to reduce lignin content of OPEFB from 28.9% to 7.6%. The highest actual formic acid concentration we obtained from the experiment was 2725 ppm at 180 °C, 60 minutes reaction time, and 0.5 M H2SO4. While according to the polynomial model, the optimal condition for obtaining maximum formic acid concentration of 2890.673 ppm was at 180 °C, reaction time of 60 minutes, and 0.3 M H2SO4.

Indonesia is the largest producer of palm oil in the world. Around one-fifth of the palm oil processing, weight end up as solid waste, named as oil palm empty fruit bunch (OPEFB). OPEFB is lignocellulosic biomass which contains cellulose, hemicellulose, lignin and minerals. The utilization of cellulose and hemicellulose requires pretreatment to open the lignin bond. This study examines the pretreatment of OPEFB using microwave assisted dilute ammonia. The OPEFB (30 - 40 mesh) was pretreated by ammonia solution with solid-liquid ratio of 1:10 under variated parameters such as ammonia concentration (7.5; 10; 12.5 %), microwave power (280; 560; 840 Watt) and reaction time (3; 6; 9 minutes).The hemicellulose content of all samples was characterized according to SNI 01-1561-1989. The results were optimized using response surface methodology with Box-Behnken model. The model showed that the highest hemicellulose content of 27.3% can be reached at pretreatment conditions of 665-Watt microwave power at 7.5 % ammonia concentration for 3 minutes.