Biodiesel can be produced from J. curcas oil through a number of ways. Out of these, chemical (alkali/acid/supercritical alcohol-catalyzed) and enzymatic trans­esterification have shown promising results. Various process parameters which influence biodiesel yield are free fatty acid (FFA) content, oil-to-alcohol molar ratio, water content, enzyme loading, reaction temperature, stirring rate, and reac­tion time. Crude Jatropha oil has very high amount of FFA. Improper handling and inappropriate storage lead to an increase in FFA of the oil due to oxidation. Presence of high FFA content in the oil leads to soap formation during alkali-catalyzed trans­esterification. In order to bring down the FFA level to <1%, a pretreatment step has been put forward. But this process is time-consuming. On the other hand, in enzy­matic transesterification, the FFA is converted to biodiesel, and so, there is no need for the pretreatment step (Berchmans and Hirata 2008; Goodrum 2002).

Membrane contactors allow two different phases, such as a gaseous phase and a liquid phase, to be in direct contact with each other without involving additional reactions that could change the properties of both phases. A membrane contactor differs from conventional membranes that are used for liquid filtration processes, such as reverse osmosis, ultrafiltration, and microfiltration. These membranes are not capable of removing gases from liquid phases, and they are not capable of trans­ferring gases into liquid phases. The process of dispersing gases into liquid phase involves three stages, i. e., (1) The transfer of gases from the gas phase to the gas-membrane interphase; (2) transfer of the gases through the membrane to the liquid-membrane interface; and (3) transfer of the gases into the liquid bulk phase. This can be illustrated as shown in Fig. 14.1.

Unlike a conventional membrane, the main driving force for a membrane contac­tor is a concentration gradient rather than a pressure gradient. Membrane contactors were researched actively a few years ago for use in the advanced separation and

purification processes in gas/liquid and liquid/liquid industries to reduce the depen­dency on conventional separation devices. Conventional separation processes, such as absorption towers and column mixers, achieve low mass transfer efficiency due to the low interfacial contact area between the two different phases and the low dispersion rate (when a device is used to aid the dispersion process) due to various side effects, including flooding, the formation of emulsions, and foaming, all of which can be solved by using a membrane contactor. However, membrane contac­tors also have their limitations. In the application of a membrane contactor to aid the mitigation of CO2 by microalgae, the membrane device must be hydrophobic to prevent the microalgae cells from clogging the pores of the membrane.

Biomass is densified into pellets, briquettes, chips, logs and bales in order for it to be utilised as solid fuel. In this form, the mass per unit volume of biomass is increased, thus improving its transportation capacity and efficient storage. The challenge in utilising biomass as solid fuel is to reduce its moisture content, to increase its energy density per volume and to reduce biomass loss due to fragmenta­tion. Incorrect evaluation of its mechanical and physical property will lead to higher transportation cost, higher compacting pressure and additive content. Typical den — sification process variables are temperature, pressure and pressure application rate, holding time and die geometry (Zachry Engineering Corporation 2009).

Conditioning of biomass through pretreatment process by chemical, biological or thermal methods helps to improve its property to be utilised as solid fuel. To pro­duce a fuel briquette, inflammable material is pressed under high pressure in a bri­quette press. Briquetting uses a reciprocating ram or piston to force the ground material through a tapered die. The produced briquettes can be in the form of pucks, logs, etc. of varying diameters and thickness depending upon the equipment and selected die geometry. Roll press briquetting is a well-established technology for the densification of powdery granular materials such as minerals, food products, detergent, coal and sludge (Plistil et al. 2005). Through briquetting, higher energy per volume and uniformity of size and shape is achievable. Proper storage of these solids fuel is crucial since they are moisture sensitive. In addition, solid fuel will emit great amount of smoke at early combustion stage due to high volatile matter content, which led to losses of un-burnt fuel gas (da Rocha 2006). Torrefaction and briquetting will improve the energy content of the solid fuel and is able to overcome the said disadvantages. Briquette is suitable to be used as fuel for boiler having capacity larger than 500 kW. Among the referred standards for wood briquette are Austrian ONORM M 7135 and German DIN 51731. Specifications of solid fuel referred to the standards include chemically untreated biomass, moisture must be <10 wt%, particle density 1-1.09 kg/dm3, diameter in the range of 25-125 mm and length range is 50-400 mm, ash content on dry matter basis <0.7 wt%, additives <2 wt% and net calorific value is 16.9 MJ/kg (Alakangas et al. 2006).

For pelleting raw materials and pellet processing, the produced pellets must meet similar criteria as briquette with fines must be <2 wt%, diameter of 6 mm and length of five times the diameter and sulphur to be <0.05 wt% of dry matter. For usage in screw feeder boilers, wood chips used are originated from stem wood; moisture is <20-30 wt% with net calorific value of more than 900 kW/bulk m3.

5.3.10.1 Textiles and Woven Household Materials

Most indigenous areas of Africa and Asia have been using OPL petioles for weav­ing mats, baskets, fans, hats, sacks, carrier bags, etc. Due to lack of technical know­how and capital cost of producing these materials in commercial quantities, their potential uses have been nipped in the bud.

Also, useful cord or rope is made by rolling OPL into strands which are further used to tie thick bands of items. The OPL strands are again useful in making nets for transporting cargo and forage. Net for catching fish is also made traditionally from OPL. OPW fibres are also used to stuff mattresses, sofa, etc.

Recently, researchers have developed heterogeneous catalytic system which involves a continuous flow for biodiesel reaction that neither deactivates nor consumes the catalyst and that minimizes or eliminates the need for multitudinous downstream separation and purification steps. The solid base and solid acid catalyst used in transesterification reaction are shown in Tables 10.3 and 10.4 . Utilization of solid

catalyst is a potential catalyst which is able to offer some relief to biodiesel producers by improving their ability to process alternative cheaper feedstock by promoting a shortened and less expensive manufacturing process (Bournay et al. 2005) .There are three important characteristics of catalyst that have a significant impact on the cost of biodiesel, namely, catalytic activity, catalyst life, and catalyst flexibility (Fig. 10.2) which would greatly influence the efficiency of the catalyst in converting oils into biodiesel.

The newly invented heterogenized technology (Fig. 10.3) in biodiesel production technology shall replace conventional biodiesel production (homogeneous cata­lyzed process) to improve the reaction process and reduce the production cost. With the introduction of heterogeneous catalyst, productions are now easily set up any­where in the nation, and the flexibility of the catalyst towards the feedstock oil low­ers the requirement for feedstock oil compared to previous catalyst used in biodiesel production. The catalyst can now catalyze most type of oils with maintained yield and remain its reusability to an extent which is more superior than most of the other homogeneous catalyst in the market. Biodiesel produced using heterogeneous cata­lyst contains lower ash content, and cleaner burning process makes biodiesel another substitution option to replace petroleum as the fuel for our industries as well as our mass transportation system.

Solid base catalyst

The Michaelis-Menten kinetics of the hydrolytic activity of both free and immobi­lized lipase were determined by measuring the initial velocity of the reaction by varying the concentration of the substrate at a constant enzyme concentration. The apparent kinetic constants of the immobilized lipase were determined with 524 mg of immobilized beads which is equivalent to 50 |rl of free enzyme taken under the same reaction conditions. The free and immobilized lipase in pH 7.0 was incubated with different concentrations of p-NPP substrate (100, 150, 200, and 250 |rg) for 1 min at 25°C.

Michaelis constant K and the maximum reaction velocity V are evaluated from the Lineweaver-Burk plot of 1/V versus 1/S. The Km values of free and immobilized lipase as calculated from Fig. 12.6 are 0.39 and 0.45 |iM, respectively, and corre­sponding V values are 10 and 9.09 amol/min. An increase in K after immobiliza­tion indicates that immobilized enzyme has an apparent lower affinity for the substrate which may be caused by the following reasons: (1) steric hindrance of active site by the support, (2) loss of enzyme flexibility necessary for substrate binding, and (3) dif — fusional resistance to solute transport near the particles of the support.

Reduced enzyme leakage, higher thermal stability, and better storage stability were the salient features achieved by this method of enzyme immobilization. By this work, an improved entrapment approach of lipase cross-linking followed by entrapment onto a hybrid matrix of alginate and к-carrageenan was studied. This enhanced cross-linked matrix is a step closer in design of a better immobilized lipase for the biodiesel industry.

Malaysia with a population of 29.570 million people (Department of Statistics 2013) and gross domestic product (GDP) estimate of US$247.781 billion (Global Finance 1987-2011 V2.1) is heavily dependent on fossil fuels—the transport and industrial sectors being the major users of petroleum, natural gas and coal in 2005. The trans­port sector took up 38% of total energy consumption; biofuels can lighten this demand from fossil fuel. The energy production was dominantly derived from coal, petroleum and natural gas, with renewable being only ~4.1% in 2006. Of this, Malaysia achieved only 1.8% for grid-connected renewable electricity (Malek 2010).

Effect of alkali addition is shown in Fig. 4.5. At 350°C (20 min after reaction starts), the decomposition process was detected for all sulfur compounds.

It is suggested that at this higher temperature the sulfur compounds of higher mass would be decomposed into simple sulfur compounds such as H2S, SO, or SO2. The alkaline reagent neutralizes these acidic compounds to suppress the emission to the gas phase by trapping them in the liquid and solid phases as mentioned above. This phenomenon of alkali addition at various temperatures was directly observed for the first time by online system measurement.

4.4 Conclusion

The sulfur species produced in the gas phase from the hydrothermal reaction of biomass sample were directly detected with high sensitivity by an online analysis with a reaction cell directly coupled with ion-attachment mass spectrometer. The sulfur species were found in gas phase. L-cysteine during hydrothermal reaction produces H2S as well as CO and CO2 gases. Hydrothermal reactions promote the extraction mechanism of sulfur compounds from the durian fruit at certain times: 15 min at 250 and 10 min at 300 and 350°C. Adding Ca(OH)2 to the reaction system of L-cysteine, H2S, CO, and CO2 gases were decreased. For durian, alkali addition at first gave a promoting effect to the sulfur release but later promoted the decom­position of these compounds.

Lipid source or feedstock for production of biodiesel can be categorized into two major groups which are edible oil/fats and nonedible oils. Edible oils include palm oil, corn oil, soybean oil, and olive oil. Among those oils, demand for palm oil is the highest in Asian region especially in Malaysia not only as a source of cooking oil but also for biodiesel production. Malaysia is one of the largest producers and exporters of palm oil in the world, accounting for 11% of the world’s oils and fats production and 27% of export trade of oils and fats. The oil palm is tropical peren­nial plant and grows well in lowland with humid places, and therefore, it can be cultivated easily in Malaysia (Ong et al. 2011). Oil palm tree will start bearing fruits after 30 months of field planting and will continue to be productive for the next 20-30 years of its life span of 200 years (Ong et al. 2011). Thus, this will ensure a consistent supply of feedstock for production of biodiesel especially in this region.

Not only palm oil is used in its original form but also the waste cooking oil (espe­cially palm oil) could be used as source lipid for biodiesel production. Waste cooking palm oil from restaurants and household is inexpensive compared with crude palm oil. By utilizing waste oil, it is a promising alternative for biodiesel production and avoiding the competition of palm oil for food consumption. Furthermore, the produc­tion of biodiesel from waste cooking palm oil is one of the better ways to utilize it efficiently and would partly decrease the dependency on petroleum-based fuel. In addition, waste cooking palm oil can be disposed safely and recycled to be an energy source that is useful to human beings. Without a proper disposal method, waste oil may contaminate environmental water. The production of biodiesel from waste cook­ing palm oil is one of the better ways to help reduce the environmental problem.

The second group of oil that can be used as lipid source for biodiesel production is nonedible oils. There are many examples of nonedible oil such as jatropha, cot­tonseed, and castor oil. The use of nonedible vegetable oils is of significance because of the great need for edible oil as food. The advantage of nonedible vegetable oil is that the production cost of biodiesel could be reduced caused by higher cost of edible vegetable oils (No 2011). An oil extracted from Cerbera odollam (sea mango), which is less expensive and known as nonedible oil, is a promising alterna­tive to vegetable oil for biodiesel production. Cerbera odollam, commonly known as the suicide tree, pong-pong, and othalanga, is a species of tree native to India and other parts of Southern Asia. The fruit, when still green, looks like a small mango, with a green fibrous shell enclosing an oval kernel measuring ~2 cm x 1.5 cm and consisting of two cross-matching white fleshy halves. Figure 8.1a, b shows the fresh Cerbera odollam fruit, while Fig. 8.1c shows the dry Cerbera odollam fruit. Cerbera odollam seed is shown in Fig. 8.1d. Upon exposure to air, the white kernel turns violet, then dark gray, and ultimately brown or black. The plant as a whole yields a milky white latex (Chopra et al. 1956).

This cheap feedstock is therefore expected to help the biodiesel to be competi­tive in price as compared to the use of raw materials from food-grade vegetable oils. The production of biodiesel fuel from Cerbera odollam oil is considered an impor­tant step for reducing the use of edible vegetable oil. Based on the extraction

process, the oil extracted from C. odollam seeds was 54%. This value is comparable to those of palm oil which stands at 45-50%, indicating that it can be a promising source of oil for biodiesel production. The fatty acid composition of C. odollam oil is mainly oleic (45.3%), followed by palmitic (24.7%), linoleic (19.3%), and stearic (8%). This composition is similar to those of palm oil, only without myristic acid. Table 8.3 lists lipid’s source by categories for biodiesel production using enzymatic reactions.

In any discussion of the enzymatic approach for biodiesel, one comes across two major bottlenecks. The first is the deactivation of the biocatalyst, usually within a period so short that the whole process is deemed to be not cost-effective. The second bottleneck is the high cost of enzyme and the cost associated with its need for con­stant replacement.

In studies conducted by SBC, the lipase is observed to be deactivated due to glycerol, methanol or ethanol when inert solvent is absent. When the reaction pro­ceeds to form the product, glycerol droplets present as a secondary phase gradually poison the catalyst. Some techniques make use of dilute portions of the lipase in a CSTR design to avoid this problem. However, all this does is lower the probability of contact between catalyst and glycerol. The disadvantage is the increased reaction time, which can be prolonged to several hours. If the reaction time is to be short­ened, a higher amount of lipase will have to be used. However, in this case, glycerol amount will also increase rapidly, thereby deactivating the catalyst. Shifting to a packed bed design will result in glycerol clogging up the bottom of the reactor after the reaction progresses for quite some time.

In the ET Process®, the problem of catalyst poisoning is solved with the use of an inert solvent. The solvent dissolves glycerol and produces a homogeneous solution. Without a secondary phase, the immobilized lipase maintains optimum performance and converts 100% of the oil (natural triglyceride and FFA) into products. The short reaction time and long lipase life span are two of the most important features of a tech­nology that is industrially viable and competitive in the market. Without the use of the inert solvent, the lipase cost problem cannot be overcome. Both CSTR and packed bed design can be used with the inert solvent, although the latter is more highly preferred.

Another feature that can complete the formation of a sustainable, green energy business is low cost. That cost is important is undeniable. In the history of any green energy business, novel ideas alone cannot force mass adaptability of a technology. The solution to fossil fuel dependence needs to address not just environmental con­cern but also economic practicality. Only then will it have widespread use and be called a truly sustainable technology.

Characteristics of the immobilized lipase used in the ET Process® are good enough to render its cost contribution in the process insignificant over its life span. The current lipase cost is USD 350/kg. Over the lifetime within which the immobi­lized lipase is used, the cost contribution to the biodiesel product will be USD 0.029/ kg or less. A further extension to 18 months will decrease it to USD 0.019/kg. To date, there are more than ten different lipases that could meet the requirements of

the process. When this kind of biocatalyst is regularly used in the future, mass pro­duction will reduce the cost even more.

The value of the technology is in its pioneering method of prolonging biocatalyst life span and, in doing so, minimizing the operating cost. This is previously unreach­able with an enzymatic biodiesel process. Another significant effect is the reduced cost allocation for the feedstock. The enzymatic process allows for flexible feedstock acceptance, such that oils with high FFA content can be used without expensive purification steps.

In the past, a biodiesel production system assigns 70-90% of expenses to feed­stock procurement. Sourcing is affected by strict requirements for low FFA level and low water content, while output is affected by catalyst removal, soap formation and absence of profitable co-products. The ET Process® can reduce feedstock cost allocation to lower than 50%. This is the major cost-saving factor. The profit­boosting factor comes from the co-production of pharma-grade glycerol, phyto­chemicals and zoochemicals. The mild reaction inherent to the enzymatic process and absence of basic and acidic catalysts allow these substances to be extracted through downstream processing. Other applications can also produce high value — added products like fatty acid isopropyl esters or similar products from the reaction of oil with higher alcohol reactants.

Table 11.3 Typical composition of crude palm oil (Hui 1996)