PPF is an elongated fibrous (cellulosic) residue of palm oil fruits generated after oil extraction processes. PPF constitutes about 16% of the solid biomass of FFB. The strands of PPF which measure about 30-50 mm in length have been found to con­tain about 5-7% of residue oil after screw-press extraction of CPO (Choo et al. 1996; Sanagi et al. 2005).

Malaysia being the current world’s leading exporter of palm oil generates about 12 million tonnes of PPF annually (Lau et al. 2008; Mazaheri et al. 2010). PPF is mainly combusted as a solid boiler fuel for the production of steam and electricity in the oil mill (Yusoff 2006).

The physico-mechanical properties of PPF include 150-500 pm diameter (Sreekala and Thomas 2003), 0.7-1.55 g/cm3 density (Sreekala and Thomas 2003), 13.71% tensile strain, 3.38 pm cell wall thickness, 1.37 mg/m fibre coarseness, 55.43 x 10-4 rigidity index and 50-400 MPa tensile strength (Sreekala et al. 1997).

PPF contains about 39% fatty acid, 35% moisture content by wet weight, 75.99% volatile matter, 12.39% fixed carbon, 5.33% ash, 50.27% carbon, 7.07% hydrogen, 0.42% nitrogen, 0.63% sulphur and 36.28% oxygen (Azali et al. 2005). The heating value of PPF is about 20.64 MJ/kg. Considering sugar contents on dry basis, PPF consists of about 41-61% alpha cellulose, 42-65% cellulose, 17-34% hemicellu — lose, 13-25% lignin, 18-21% pentosan, 1.3% mannose, 2.5% arabinose, 33.1% xylose, 1.0% galactose and 66.4% glucose (Law et al. 2007; Abdul Khalil et al. 2006; Rozman et al. 2007). About 2.8-15% extractives can be obtained from PPF with 4,000-6,000 ppm of vitamin A and 2,400-3,500 ppm of vitamin E (Choo et al. 1996).

The inorganic composition of PPF expressed in % ash (moisture free) includes 3.54% Si2O, 0.24% K2O, 1.15% CaO, 0.13% MgO, 0.24% Fe2O3, 0.57% Al2O3 and 0.19% P2O5 (Chaiyaomporn and Chavalparit 2010). PPF fuel density is about 1,400 kg/m3 (Mohammed et al. 2012).