Vegetable oil from oil palm (Elaeis guineensis) is one of the most important commercial products in Indonesia, which produces about 25 million tons of crude palm oil (CPO) annually, with an average growth higher than 2 % in 2012 . In Indonesia, oil palm trees are located in rural areas, spread mostly on Sumatera and Kalimantan islands. In recent years, Indonesia has successfully encouraged the expansion of the crop in more remote locations on the islands of Kalimantan (Borneo), Sulawesi, and Papua. The Ministry of Agriculture of the Republic of Indonesia estimated the oil palm area of 22 plantations to be approximately 11 million hectares in 2013.
Palm oil mills separate CPO and palm kernel oil (PKO) as main products, leaving residues such as wastes of shells, fibers, fronds, palm kernel cake, and empty fruit bunch (EFB), which is the main by-product of the palm fruit. Palm oil is used in a wide variety of food products such as cooking oil, shortenings, and margarine, whereas PKO is a raw material in the production of non-food products including soaps, detergents, toiletries, cosmetics, and candles. EFB and fronds are expected to be further processed into paper and paperboard, while fibers and shells can be utilized as a boiler fuel to generate steam in palm oil mills. However, most of the residues are not utilized, and most of the EFBs are left rotting in the plantation site without further processing.
This study aimed to investigate the production of dissolving pulp (DP) from empty fruit bunch (EFB) of oil palm (Elaeis guineensis) as a non-wood material using a combination of prehydrolysis, soda-anthraquinone (AQ) cooking, and elementary chlorine-free (ECF) or totally chlorine-free (TCF) bleaching. Prehydrolysis was performed for 90–180 min at 150 °C. Subsequently, the prehydrolyzed EFB was subjected to several soda-AQ cooking conditions with active alkali (AA) dosages of 19, 20, and 21 % at 160 °C. The obtained pulps were bleached following ECF and TCF sequences with oxygen (O), chlorine dioxide (D0), extraction with peroxide (Ep), chlorine dioxide (D1), and peroxymonosulfuric acid (Psa) stages.
The results showed that the optimal duration of the prehydrolysis was 180 min, while the best AA dosage of the soda-AQ cooking was 20 %. The determination of pulp qualities showed that ECF bleaching with the Psa–D0–Ep–D1 sequence reached 90.7 % ISO brightness, 8.5 cP viscosity, 98.6 % α-cellulose, and that TCF bleaching with the O–Psa–Ep–Psa–E sequence attained 81.6 % ISO brightness, 9.6 cP viscosity, and 95.9 % α-cellulose. The results indicated a promising potential of EFB for DP production.