Two common potential biofuels from oil palm biomass are producer gas from gas­ification and biogas via anaerobic digestion. A pilot scale compartmented fluidised — bed gasifier was set up in MPOB Experimental Palm Oil Mill in Labu to produce syngas using palm shell and mesocarp fibre (Rahman et al. 2011).

POME contains high concentrations of organics (BOD = 18,225-23,904 ppm, COD=45,818-54,861 ppm) and suspended solids. Through decomposition of organic matters in anaerobic pond by microorganism, biogas with 60-70% methane (CH4), 30-40% carbon dioxide (CO2) and trace amount of hydrogen sulphide (H2S) is produced (Loh et al. 2011) . An estimated biogas production form POME of around 1,560 million m3 a year (2010) is attainable.

To capture biogas from POME, two common technologies have been used: digester and covered lagoon. The biogas trapped can be used in various applications such as on and off grid electricity generation, CHP for steam and heat, co-firing in biomass boiler and diesel generator set to reduce the utilisation of palm shell and diesel and lastly gas bottling as an emerging filed but has yet to be fully exploited.

Under NKEA, all palm oil mills have to construct biogas trapping facility by 2020. The current status of biogas trapping facility in the palm oil industry is as follows: 57 plants completed, 15 under construction and 149 under planning (MPOB survey 2012). The palm oil industry has a potential to be a major player in mitigating GHG emis­sions, with a potential of 16-20 million tonnes of CO2 equivalent per year mitigated.

Other feedstock for second-generation biofuels is jatropha which was initiated by the government and is currently ongoing under the National Jatropha Programme led by SIRIM.

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).

An alternative catalyst for conventional transesterification is homogeneous acid catalyst. Sulfuric acid (H2SO4) and hydrochloric acid (HCl) are usually preferred as acid catalysts. They are preferred to base catalyst when the amount of FFA in feed­stock is high due to its high tolerance and less sensitivity towards high FFA concen­tration. The application of acid catalyst can avoid formation of soap.

This is because FFA is esterified to produce fatty acid alkyl esters, and potassium or sodium ions, which can lead to the unwanted saponification reaction, are absent from the process. Moreover, esterification and transesterification can be done simul­taneously using acid catalyst, thus eliminating the need to use basic catalyst and preventing saponification problem.

Marchetti and Errazu (2008) conducted the esterification of oleic acid using acid catalyst (H2SO4) and refined sunflower oil as feedstock. The conversion reached
almost 100% even when the FFA content in the feedstock was 27.22% w/w. Increasing the FFA content in oil feed allows a higher final conversion and also increased the reaction rate. The formation of soap was minimal for this catalyst as the FFA was reduced to 0.54% w/w. Also, the results showed that the process was highly depen­dent on the amount of catalyst. The initial reaction rate was increased as more amount of catalyst is used, but it did not affect much of the final conversion.

Even though the catalyst can tolerate high amount of FFA in feedstocks, using H2SO4 for biodiesel synthesis caused the drawback related to its strong acidic char­acter. Equipments involved in the process are susceptible to corrosion problem, while wastewater used for removing acid catalyst from the resultant biodiesel is hazardous to the environment. Furthermore, acid catalyst is less preferable than basic catalyst because of the slower reaction and requires severe operating condi­tions for high biodiesel yield. Although the productivity can be increased with high temperature and high concentration of H2 SO4, in return it would affect the yield because catalyst could burn some of the oil (Sharma et al. 2008).

Another alternative for usually employed Brqrnsted acid (i. e., H2SO4 and HCl) is Lewis acid, which also can catalyze transesterification of oil into biodiesel. Cardoso et al. (2008b) employed two different acid catalysts for converting oleic acid into ethyl oleate: H2SO4 as a Brqrnsted acid catalyst and tin (II) chloride dehydrate (SnCl22H2O) as a Lewis acid catalyst.

Among the advantages of Lewis acid are less corrosion of the reactors and also being inexpensive. They concluded that there was virtually no difference between the conversion and selectivity of ethanolysis of oleic acid catalyzed by SnCl2 and H2SO4. Also, the activation energy of esterification using SnCl2 was found approxi­mately similar to previous work of H2SO4-catalyzed esterification of FFAs in sun­flower oil.

“Immobilization” refers to localization or physical confinement of an enzyme (bio­catalyst) in a certain defined region of space on to a solid support or on a carrier matrix with retention of its catalytic activity. The main purpose of immobilizing an enzyme is for reuse so that the high cost of enzyme can be overcome to a certain extent. The term “immobilized enzyme” was recommended at the first Enzyme

Engineering Conference in 1971. Several factors determine the choice of a carrier material such as mechanical strength, microbial resistance, chemical durability, thermal stability, hydrophobic or hydrophilic character, loading capacity, ease of regeneration, and finally the cost (Karube et al. 1977). The main objective of enzyme immobilization is its economic application. Ease of control and uniformity of con­versions can also be derived by immobilizing the enzymes.

Lipases (triacylglycerol hydrolase, EC 3.1.1.3) are enzymes that can catalyze the hydrolysis of carboxylic ester link in the triacylglycerol moiety to form free fatty acids, di-monoglycerides, and glycerol. In addition to the main function which is hydrolysis of ester bonds, lipases can also catalyze the esterification, the creation of this link between alcohol hydroxyl groups and carboxyl groups of carboxylic acids. Lipases have a wide spectrum of biotechnological applications since they can cata­lyze esterification, hydrolysis, transesterification, alcoholysis, acidolysis, and ami — nolysis. In short, lipases are serine hydrolases which are of considerable physiological significance and industrial potential that can catalyze a number of reactions (Pandey et al. 1999; Jaeger and Eggert 2002; Vulfson 1994).

14.2.1 CO2 Emissions and Environmental Concerns

As of 2009, the total CO2 emissions from the combustion of fossil fuels were esti­mated to be ~29,000 MT. The transportation industry contributed more CO2 emissions than any other sector, accounting for more than 37% of the total. Scientists have indicated that CO2 emissions are more likely to harm the environment than to pro­vide any benefit. One of the greatest effects of CO2 emissions may result from its contribution to the greenhouse gas (GHG) emissions that are associated with global climate change. CO2 is the second largest contributor to climate change, making up 30% of the GHG emissions that cause global climate change and threaten ecologi­cal systems. The latest report from the World Meteorology Organization showed that the La Nina event that occurred in 2010 and 2011 ranked among the strongest of the past 60 years and that large parts of Central Africa and Southern Asia were likely to have the warmest year on record (WMO 2008, 2011).

Antarctic and arctic ice also showed declines that were even more rapid than has been forecast through the years, causing increases in the sea level (Stroeve et al. 2007; Swingedouw et al. 2008). Over the last century, the sea level has risen about 17 cm, forcing some communities in Fiji, Papua New Guinea, Panama, and Vanuatu to relocate (Mattson 2010). The sea level in Malaysia, specifically in the west coast peninsular and Kuala Baram in Miri, also has increased and is expected to increase by an additional 10-13 cm over the next 100 years (The Star Online 2010). If there are no efforts to prevent the release of CO2 to the atmosphere, it is likely that large land areas will be covered by water in the future.