Production of biodiesel is relied on either strong base or strong acid homoge­neous catalysts in the transesterification reaction. The examples of base catalysts are potassium hydroxide (KOH) and sodium hydroxide (NaOH), while sulfuric acid (H2SO4) is commonly used as an acid catalyst (Freedman et al. 1984). The alkali — catalyzed transesterification is economically feasible process as both NaOH and KOH catalysts are cheap. The alkali-catalyzed transesterification pro­cess is carried out under a low temperature (methanol boiling reflux) and atmo­spheric pressure environment, and the conversion rate is high with no intermediate steps (Leung and Guo 2006). However, the alkali homogeneous catalysts are highly hygroscopic. They also form water when dissolved in the alcohol reactant and this will affect biodiesel yield [Eq. (10.1)]. Therefore, they should be prop­erly handled.

KOH or NaOH + CH3OH ^ CH3O — K or CH3O — Na + H2O (10.1)

Today, the alkali-catalyzed process produces most of the biodiesel. The conven­tional transesterification process for biodiesel manufacturing process consists of four main principal steps (Cheng 2009):

Table 10.2 Advantages and disadvantages of catalysis for transesterification reaction Type Advantages Disadvantages

1. Pretreatment of the crude feedstock to remove component (water or FFAs) that is unfavorable to subsequent processing steps.

2. Transesterification reaction: the pretreated oils or fats are reacted with alcohol (normally methanol) to form mono-alkyl esters and by-product glycerol.

3. Alkyl ester (biodiesel) purification: the excess methanol, catalyst, and glycerol are removed by water washing step and chemical treatment. The methanol will recycle for the next reaction.

4. Glycerol purification: methanol and catalyst in glycerol phase are recycled and removed by water washing and chemical treatment step to produce higher grade glycerol for commercialization.

Figure 10.1 show the industrial process for homogeneous catalyzed transesterifi­cation reaction.

Stability of lipases in organic solvents is a vital factor for many industrial applica­tions. This feature of lipase is beneficial in transforming substrates which are poorly soluble or unstable in water. Moreover, at low water activity, lipases favor esterifica­tion reaction rather than hydrolysis which can be an added advantage in its applica­tion. Stability of immobilized B. cepacia lipase were tested in different solvents like phosphate buffer of pH 7, ethanol, methanol, isopropanol, 1-butanol, and я-hexane. The immobilized beads were incubated in the above-selected solvents at 25°C for 1 h. Thereafter, the solvent was decanted, and the catalytic activities of immobilized lipase were done in accordance with Sect. 12.5.2. The activity of immobilized lipase in phosphate buffer pH 7 was taken as reference for calculating relative activities of other solvents.

The solvent stability of immobilized lipase in hybrid matrix of alginate/к — carrageenan after cross-linking with glutaraldehyde is shown in Table 12.6. No dis­integration of the matrix was observed in any of the solvents used. This study showed that immobilized B. cepacia lipase was more stable in alcohols like ethanol, metha­nol, and isopropanol but showed lesser stability in acetone and butanol.

First-generation biofuels refer to biodiesel and/or bioethanol derived from bio­resources, e. g. sugar, starch, corn, vegetable oil or animal fats using conventional technology (use established processes and mainly food products as feedstock). As such, food vs. fuel debate arises, and thus, there is a need to address issues like food security vs. energy security, food shortage and food price rises.

The feedstock for second-generation biofuels is generally derived from non-food biomass and non-food crops. Second-generation biofuels can also be defined based on the type of feedstock or technologies used.

For third-generation biofuels, the feedstock used is mainly algae and microbes (advanced biofuels). Table 1.1 illustrates briefly the different generations of biofuels which can exist in many different forms.

S. K. Loh (*) • Y. M. Choo

Malaysian Palm Oil Board (MPOB), Selangor, Malaysia e-mail: lohsk@mpob. gov. my

R. Pogaku and R. Hj. Sarbatly (eds.), Advances in Biofuels,

DOI 10.1007/978-1-4614-6249-1_1, © Springer Science+Business Media New York 2013

Figure 4.3 represents a typical mass spectrum obtained for the durian sample at 300°C. The peaks at m/z 41, 55, 71, 83, 129, 157, 161, and 189 are observed. The peaks with low intensities at m/z 41, 55, and 71 are assigned to [H2S + Li]+, [SO+Li]+, and [SO2+Li]+, respectively. These species in durian as volatile compounds was reported in other reports (Neti et al. 2011; Wong and Tie 1995).

The H2S and SOx peaks are detected at low intensity. H2S is known to be derived from arils in ripe durian fruits (Greve 1974). Moser et al. reported negligibly small amount of H2S from immature fruits (Moser et al. 1980). For detailed investigation of reaction process of these compounds in hydrothermal reaction, the peaks were detected by SIM for quantitative analysis.

Figure 4.4 shows the relationship between the reaction time and the amount of generated sulfur compound during the hydrothermal process of durian at the sub­critical temperatures of 250, 300, and 350°C.

At all the temperatures, the released sulfur compounds increase along with the time elapsing. The compounds, except for H2S and SOx, would be resulted from extraction processes. The peak intensities, corresponding to the amounts of these sulfur compounds, drastically rise up from 250 to 300°C. However, the intensities decrease at 350°C, suggesting that the decomposition process started at this temperature.

During the hydrothermal reactions, two mechanisms likely occur, i. e., extraction and decomposition. By extraction in the reactor, the higher molecular weight com­pounds could be yielded. Decomposition of the higher molecular compounds occurs, and the lower molecular compounds could be produced at high tempera­tures, as below:

Durian ^ 1 — propanethiol, methyl phenyl disulfide, etc. (lowtemperature) (4.6)

Durian ^ H2S, CO, CO2,SO, SO2,SO3etc. (high temperature) (4.7)

Most of the established biodiesel production lines are based on chemical methods. The catalysts used are acid catalyst, such as H2 SO4, or alkaline catalysts, such as NaOH and sodium methoxide. The alkaline method is better than acid catalysis due to the high FAME yield and short reaction times. Generally, large molar ratio of methanol to oil is needed for alkaline catalysis process to achieve high yield, and a distillation process will be needed for methanol recovery and biodiesel refining. Chemical methods give high conversion of triacylglycerols (TAG) to methyl esters (biodiesel) in relatively short times (4-10 h). However, they have drawbacks such as high energy consumption, difficulty in recovering the glycerol, and significant amount of alkaline wastewater. The fatty acid alkaline salts (soaps) are by-products which have to be removed by washing with water. The chemical catalysis process is still the most popular method for industrial scale use due to the high cost of lipase (Tan et al. 2010).

To overcome the disadvantages of chemical catalyst, biocatalyst especially enzy­matic transesterification can be the solution for the production of biodiesel. Table 8.2 presented the comparison between enzymatic technology and chemical method using alkaline and acid process.

In contrast to chemical transesterification, enzyme-catalyzed processes are promising due to high selectivity of enzyme in reaction under mild operating con­ditions (Salis et al. 2003, 2004; Jaeger and Eggert 2002; Schimd et al. 2002). Furthermore, recovery of FAME is simple to accomplish (Fukuda et al. 2001). When compared to base catalysis, FFA concentration in the oil is not critical to enzymatic transesterification because fats containing triglycerides and FFA can be enzymatically converted to biodiesel in a one-step process. Lipases are able to catalyze both transesterification and esterification reactions (Szczesna Antczak et al. 2009). Production of cheaper an. robust lipase preparations together with system development that favors for long-term, iterative use of biocatalyst can give

rise to the replacement of chemical processes with enzymatic route (Gerpen 2005; Meher et al. 2006; Ma and Hanna 1999; Ranganathan et al. 2007; De Greyt 2004; Marchetti et al. 2007; Akoh et al. 2007).

Though at present, the high cost of enzyme production may be a major obstacle for commercialization of enzyme-catalyzed processes, recent advances in enzyme technology, such as the use of solvent-tolerant lipases and immobilized lipases, making catalyst reutilization possible, have been made to develop cost-effective systems (Oliveira et al. 2006; Rosa et al. 2008). In addition, if the lipase is immobi­lized, then it becomes an independent phase within the reaction system, which may easily be retained in the reactor with concomitant advantages in preventing con­tamination of the products and extending its useful active life. Further, increasing the temperature generally increases the rate of lipase-catalyzed reaction per unit amount of active enzyme; however, increasing the temperature also leads to a higher thermal deactivation rate of the lipase itself, thus yielding decreasing amounts of active enzyme. Because immobilization provides a more rigid external backbone for lipase molecule, temperature optima are expected to increase, which results in a faster reaction rate (Al-Zuhair et al. 2006).

The ET Process® was developed to address common problems in enzymatic bio­diesel production. The process consists of primary and trim reactors. Typically, a reaction occurs at room temperature (25-30 °C) and ambient pressure.

The reaction time is in the range of 10-60 min, depending on the feedstock oil and alcohol reactant used. A well-mixed solution of oil, alcohol reactant, inert sol­vent and biodiesel is fed into a primary packed bed reactor or CSTR. The output of the primary reactor is separated into two liquid phases by evaporation of inert solvent, unreacted alcohol and water. The residue contains one phase composed of
crude biodiesel and another phase containing crude glycerol, which includes traces of solvent and alcohol. Crude biodiesel is re-mixed with inert solvent and make-up alcohol and allowed to proceed to completion. Evaporation again separates crude biodiesel from crude glycerol. Figure 11.2 shows the simplified flowsheet and photo of the mini-ET Process®.

Fig. 11.2 (continued)

At the end of the reaction, inert solvent and reactant alcohol are recovered, separated and reintroduced into the process. Trace water from oil, reactant alcohol and inert solvent or that produced from the reaction is discharged.

The final pure glycerol is obtained by removing residual solvent, alcohol and water through an evaporator. Pharma-grade glycerol can be obtained by decoloriza — tion of the glycerol product. Table 11.2 shows the typical product specifications.

The lipase source and immobilization process will affect the efficiency of the reaction. A good immobilization process can produce competitive catalyst perfor­mance, even when starting out from different lipase sources. The immobilized lipase can be used in the process for 12-18 months under normal operating condi­
tions, exhibiting steady activity within this period of time. The half-life of the bio­catalyst can reach more than 60 months. The amount required for the process is typically a few percent of a stream day capacity.

According to Costa and Morais (2010), algal biomass can be converted into biofuel, yielding a CO2-neutral energy carrier comparable to biofuels produced from other biomass sources. There are many advantages of using bioethanol compared to gaso­line. Bioethanol has a higher octane number (i. e. 107), broader flammability limits, higher flame speeds and higher heats of vaporisation. Octane number is a measure of the gasoline quality and can be used for prevention of early ignition which leads to cylinder knocks. Higher octane numbers were preferred in internal combustion engines. An oxygenate fuel such as bioethanol provides a reasonable anti-knock value. Ethanol contains 35% oxygen, which reduces particulate and NOx emissions from combustion. Also, as it contains oxygen, fuel combustion is more efficient, reducing hydrocarbons and particulates in exhaust gases. The complete combustion of a fuel requires the right amount of stoichiometric oxygen in existence and the amount of stoichiometric oxygen. Oxygen content of a fuel increases its combustion efficiency. Because of this, the combustion efficiency and octane number of bio­ethanol are higher than those of gasoline (Balat et al. 2008). With these properties, bioethanol is higher in compression ratio, shorter in burning time and leaner in burn engine, which leads to theoretical efficiency advantages over gasoline in an internal combustion engine (Balat and Balat 2009). Some properties of alcohol fuels are shown in Table 13.2.

Several papers have been published on macroalgae fermentation to produce bio­ethanol. Among them, they were Horn et al. (2000a, b) who reported the fermenta­tion process from extraction of Laminaria hyperborea pretreated with water at pH 2 and 65% for 1 h and fermentation using Zymobacter palmae instead of yeast to produce bioethanol. This was in contrast with Adams et al. (2009) who found that the pretreatments were not required for the fermentations with Saccharina latis — sima. It was found that higher ethanol yields were achieved in untreated fermenta­tions than in those with altered pH or temperature pretreatments. Besides that, Lin et al. (2000) also report that acid hydrolysis could be performed at 0.4 M, at 100% for 3 h after extraction of carrageenan from seaweeds Eucheuma serra. The work by

Lin and coworkers was used as the pretreatment of E. cottonii as this raw material belonged to the same species.

The present work explores the suitability of macroalgae E. cottonii as fermenta­tion feedstock for bioethanol production via yeast fermentation. The effect of differ­ent acid hydrolysis conditions, such as the temperature and acid molarity on the concentration of bioethanol, was investigated.

To gain maximum environmental benefits, the current biogas harnessing technology in POME ponds must be strategically moved towards achieving zero emissions for the processing of POME. Biogas can be trapped and either used for electricity and steam generation for use in the mill or used in any other viable applications. The solid sludge discharged after the anaerobic digestion can be dried and used as natural fertiliser in the plantation. Many other applications such as recovery of wastewater discharge via reverse osmosis and ultrafiltration as drinking water can also be considered to provide a total solution to the environment.

Oil palm tree is a golden crop that produces oil as food and abundance of bio­mass that can be used for many different applications. A strategic approach to dis­tribute the oil and the biomass available for each possible application is required so that a sustainable palm resource management can be achieved to maximise the use of the resources to benefit the palm oil industry taking into consideration to fulfil the requirement for sustainability.

To ensure sustainable biomass resources management, perhaps government pol — icy/initiative is needed to drive the industry, so as to ensure consistent supply of the feedstock material to support the RE policy. The establishment of a National Biomass Strategy/National Biomass Consortium recently formulated could be of good shape to facilitate economic scale utilisation of oil palm biomass. At the same time, standards development and conformity assessment is an enabler for bioenergy development in the country.

Besides using oil palm biomass for biofuel production, other areas worth pursu­ing beyond oil palm biomass are fine chemicals or minor components that fetch high value although they present in small quantity. MPOB will intensify the R&D in these new growth areas. The chemical components such as C5 and C6 sugar mol­ecules in oil palm biomass can be a promising precursor and building block to construct medium and long chain (higher) hydrocarbon chain chemicals.

1.2 Conclusion

Malaysia (as a whole) and the oil palm industry have huge potential to become pro­ducer for RE besides producing oil to feed the world. The oil palm industry plays an important role in supporting the nation’s energy requirement in transportation, elec­tricity and industrial sectors. To encourage and realise RE deployment especially using palm oil, EFB and POME, the long-awaited attractive incentives and practical framework have been put forward as the drivers for the country to go green. Development of green fuels will contribute significantly to reduction of GHG emis­sions and mitigate climate change.

Palm kernel cake (PKC) is the by-product or solid residue resulting from the mechanical screw pressing of palm kernels which contains some residual oil. In Malaysia alone, ~2.2 million tonnes of PKC were produced in 2007 which increased to about 2.4 million tonnes in 2009 (MPOB 2012) due to expansion of the palm oil industry. The global generation capacity of PKC in 2011 was estimated at 3.5 mil­lion tonnes (MPOB 2012).

PKC is being used currently as fattening steers in feedlots (Akpan et al. 2005). Depending on the amount of PKS in the PKC, crude protein content of PKC may range from 160.0 to 180 g/kg DM. PKC again contains high amount of minerals including copper an. zinc which have no significant disadvantage (such as mortality in ruminants fed with PKC) as reported by Hair-Bejo et al. (1995). PKC contains about 78% hemicellulose in the form of mannan and 12% cellulose (Sundu and Dingle 2003).

PKC has dry matter content of 883 g/kg DM, 126-131 g/kg DM extractives,

39.4 g/kg DM ash content,131 g/kg DM crude fibre, 460.5 g/kg DM ADF and 682 g/kg DM NDF (Ramachandran et al. 2007; Akpan et al. 2005). PKC has been analysed by Ogbuagu (2008) to contain high values of carotenes or vitamin A (0.16 mg/100 g), thiamine (0.07 mg/100 g), riboflavin (0.07 mg/100 g), nitrates (3.05 mg/100 g) and nitrites (0.29 mg/100 g).

High conversion and yield of biodiesel can be achieved with the application of solid base catalysts. However, the sensitivity towards FFA in the feedstock limits their performance. To overcome this problem, heterogeneous acid catalysts are suitable alternatives than their counterpart as they are more tolerant towards feedstock pos­sessing high acid value. In addition, the catalysts can also be used to simultaneously catalyze esterification and transesterification, which eliminates the requirement for two-step processes of biodiesel production. They are good alternatives to the homo­geneous acid as they simplified the separation of catalyst from the reactants and can be recycled for further use. These catalysts significantly simplify biodiesel synthe­sis and, at the same time, reduce the production cost.

Among solid acid catalysts, zirconia has received considerable attention due to its high thermal stability and amphoteric nature, which can behave as both as an acid and as a base. Zirconia can be modified by incorporating suitable anions, such as sulfate ions to form a highly acidic or superacidic, depending on the required conditions.

Lopez et al. (2008) studied the catalytic performance of titania zirconia (TiZ), sulfated zirconia (SZ), and tungstated zirconia (WZ) for esterification of carboxylic acids and transesterification of triglycerides. Although SZ was the most active cata­lysts for the processes, the problem related to leaching of its sulfur loading was observed during the catalyst reusability test. The author suggested that WZ was more suitable for long-term use and can be easily regenerated by calcination in the air. The application of tungsten oxide zirconia (WO3/ZrO2), sulfated zirconia, and Amberlyst-15 in production of biodiesel was investigated by Park et al. (2010b). WO3/ZrO2 showed the highest activity among them, and there was also no apparent loss or leaching of WO3. Increasing the reaction temperature solved the low activity of the catalyst in feedstock with high FFA content.

The potential of ion exchange resin as catalyst for producing biodiesel has also been studied by researchers. Acidic ion exchange resin, such as Amberlyst-15, is inexpensive and commercially available as solid acid catalyst. This resin enables hassle-free separation step, aside from its excellent performance especially for esterification of FFA. Talukder et al. (2008) reported that Amberlyst-15 was a better choice than Novozym 435 (commercial enzyme for biodiesel catalysis) because of higher biodiesel yield and also low catalyst cost. The presence of organic solvent does not affect the performance of Amberlyst-15, instead increases the biodiesel yield. However, Amberlyst-15 performed worse than Novozym 435 when the water content in the feed was equivalent to 4 wt%, due to the hygroscopic nature of the catalyst and water may have been adsorbed on its surface.

In another study, Park et al. (2010a) confirmed that the esterification of FFA using Amberlyst-15 was hindered by water produced during the process. Another heterogeneous acid resin, Amberlyst BD20 maintained its catalytic activity even with water present. Characterization of the catalyst showed that it does not have pores on the surface, which prevents the adsorption of water on the surface.

Heteropolyacids (HPAs) possess high activity and stability, strong Brqrnsted acidity, and also excellent water tolerability. They can be employed as either hetero­geneous or homogeneous catalysts depending on their composition and the reaction medium. Tungstophosphoric acid (H3 PW12O40) was employed as the catalyst for promoting esterification of saturated and unsaturated fatty acids (Cardoso et al. 2008a). The conversion of oleic acid to ethyl oleate using HPA catalyst was compa­rable with those using catalysts such as H2 SO4 and PTSA. The catalyst was less productive with the inhibition of water, which resulted in decreased ester yield. On the brighter side, the catalytic activity of H3PW12O40 remained unchanged even after several recovery cycles.

A one-step solgel co-condensation was applied for incorporating tantalum per­oxide with tungstophosphoric acid to produce mesoporous composite catalyst, H3PW12O40/Ta2O5 of different H3PW12O40 loading (Xu et al. 2008). The catalyst hav­ing H3 PW12O40 loading of 10.8% demonstrated the highest catalytic activity. Any value higher than this would result in decreased porosity of the composite, which leads to blockage of the pores of Ta2O5 matrix. Complete esterification of myristic acid was achieved, and the yield from transesterification of soybean oil exceeds 75% using the synthesized catalyst. However, extended reaction time was required (24 h). No leaching of catalysts into biodiesel phase was reported for this study.

Xu et al. (2009) continued to further study the previously used catalyst. The hybrid catalyst was produced with the addition of either methyltrimethoxysilane (MeTMS) or phenyltrimethoxysilane (PhTMS) and silica (SiO2). The integration of the hybrid catalysts with both alkyl groups not only increased the yield for trans­esterification of soybean oil but also tuned the hydrophobic/hydrophilic balance of the catalyst. As a result, higher activity and much lower catalyst deactivation were obtained compared to alkyl-free catalysts. However, the preparation of the catalysts is complex when taking into account of the materials and processes required for this part.