It has been widely accepted worldwide that global warming is by far the greatest threat and challenge in the new millennium. In order to stop global warming and to promote sustainable development, renewable energy is a perfect solution to achieve both targets.
The RPS is rapidly emerging as a popular mechanism among policy makers to increase the penetration of renewable energy in the electricity market. Renewable Portfolio Standards (RPS) is a regulation that requires a renewable energy generated from eco-friendly energy sources such as biomass, wind, solar, and geothermal. The RPS mechanism generally is an obligatory policy that places on electricity supply companies to produce a designated fraction of their electricity from renewable energies.
The domestic companies to supply electricity largely rely on wood pellets in order to implement the RPS in spite of undesirable situation of lack of wood resources in Korea. This means that the electricity supply companies in Korea must explore new biomass as an alternative to wood. EFB and PKS are valuable lignocellulosic biomass that can be used for various purpose. The annual amount of lignocellulosic residues generated by the oil palm industry is 140 million ton, which corresponds to 17 Mtoe (million tons of oil equivalent). If EFB and PKS are used as alternative raw materials for making pellets instead of wood, wood could be saved for making pulps or other value-added products. Palm kernel shell (PKS) and empty fruit bunch (EFB) as oil palm wastes can be used as raw materials used for making pellets after their thermochemical treatment like torrefaction. In this study, we focused on torrefaction of empty fruit bunches (EFB), and kernel shell of oil palm. During torrefaction the biomass is changed to obtain a much better fuel quality for combustion applications. Torrefaction is a pretreatment process which serves to improve the properties including heating value and energy densification through a mild pyrolysis at temperature typically ranging between 200 and 300℃ in the absence of oxygen under atmospheric pressure. The torrefied biomass product has a brown/black color, reduced volatile content and increased energy density. Torrefaction of oil palms wastes at above 200℃ contributed to the increase of fixed carbon with the decrease of volatile matters, leading to the improvement of their calorific values over 20.9 MJ/kg (=5,000 kcal/kg) up to 25.1 MJ/kg (=6,000 kcal/kg). In particular, EFB is more sensitively torrefied than PKS and hardwood chips because of its physical properties like fiber bundles, compared to PKS and hardwood chips. Torrefaction of oil palms wastes after torrefaction contributed to the increase of energy density. After torrefaction, it was cleary shown that the high energy density ranging from 1.3 to 1.6 was created.
In conclusion, it was found that torrefaction treatment of PKS and EFB could greatly contribute to the implement of RPS of the electricity supply companies in Korea through the increased co-firing biomass with coal.