초록
Over the past years, lack of energy fossil has become an important issue around the world, especially in developing countries such as Indonesia. Alternative energy is needed to replace utilization of fossil fuels. Bioethanol is providing one window of potential alternative energy. Lignocellulosic from oil palm empty fruit bunch (EFB) could be a promising bioethanol raw material because it will not interfere food supply. Pretreatment is a one of the steps in the bioconversion of lignocellulosic material. Pretreatment also contributed the largest cost in the bioethanol production. Black liquor as the waste of pretreatment provides significant environmental impacts. Black liquor recycling is expected to increase economic efficiency by reducing the cost of pretreatment and the amount of wastewater. This experiment used black liquor with NaOH addition as a pretreatment solution. The pretreatment process was conducted at 5 liter reactors at 150<SUP>o</SUP>C and 160<SUP>o</SUP>C. The result using black liquor was not significant different with using NaOH solution in the pretreatment process at 160<SUP>o</SUP>C, delignification and cellulose content were84.01% and 77.10%, respectively, but the results in pretreatment at 150<SUP>o</SUP>C gave the lower value. The maximum ethanol concentration in variation of pretreatment solutions: NaOH solutions, black liquor with NaOH addition at 150<SUP>o</SUP>C, and at 160<SUP>o</SUP>C are 67.42 gl<SUP>-1</SUP>, 61.14 gl<SUP>-1</SUP> and 67.03 gl<SUP>-1</SUP>, respectively, at a pretreated biomass loading of approximately 15% (w/v) with an enzyme dosage of 30 FPU g/dry biomass.