3. Characteristic of non-edible oils

Characteristics of vegetable fats and oils depend on the length and degree of un-saturation of the fatty alkyl chains. Thus, the fatty acid plays an important role in determining biodiesel characteristics. Amount of each fatty acid, chain length, and number of double bond present in the hydrocarbon chain influences the biodiesel properties [31]. The stability of biodiesel also depends on the feedstock properties used for biodiesel production. The most abundant fatty acids in the oil samples were oleic, linoleic, linolenic, palmitic, and stearic fatty acid. Oleic acid comprises of a major portion of the total fatty acid irrespective of non-edible oil summarized in Table 1. All oils have high unsaturated fatty acids (up to 80%) which mean they have good low



The presence of double bond in the fatty acid brings diesel on poor stability. This decomposi-

Non-Edible Vegetable Oils as Renewable Resources for Biodiesel Production: South-East Asia Perspective

The amount and type of free fatty acid (FFA) in the biodiesel determines the viscosity, one of the most important characteristics of biodiesel. Due to the presence of higher amount of long

viscosity compared to others. Karanja and mahua oil has similar viscosity, due to the presence of same FFA. Iodine value represents the degree of unsaturation and relatively high iodine value is reported in range 69.3 in neem to 135 in rubber seed oil (Table 1 and Figure 1). These properties are relatively applicable in cold climates. From calorific value, non-edible oils have

Cetane number (CN) is widely used as diesel fuel quality parameter related to the ignition delay time and combustion quality [14, 32]. Higher cetane numbers in all vegetable oils listed in Table 1, will give better ignition properties. Cetane number increases with the increase of saturated fatty acid, and increases linearly with the chain length, decrease with number of double bonds and carbonyl groups move toward the center of the chain. High level of saturated fatty acid (C14:0, C16:0, C18:0) raise cloud point, cetane number, NOx, and improve stability, while more polyunsaturated (C18:2, C18:3) reduce cloud point, cetane number, sta-

Generally, non-edible oil has high free fatty acid content of 2.53–22% in weight basis. Alkaline transesterification is not feasible for oil containing high free fatty acid for producing biodiesel [33, 34]. It generates soap, consumes more catalyst and reduces the effectiveness of catalyst. Subsequently, soap causes the solution to be more viscous, and leads to the formation of gel and foam that inhibits purification of biodiesel from glycerol [35]. To overcome this dilemma, biodiesel production from non-edible oils that has high free fatty acid was conducted by several methods; two/three stages reaction, acid-catalyzed esterification and alkaline-catalyzed transesterification; enzymatic process; and supercritical methanol [36, 37]. In enzymatic process, water content in the raw material does not interfere to the reaction conducted in low temperature. Lipase reaction occurs at the interface between the aqueous and oil phase [38] which generates alkyl ester with high purity and easy separation [39]. Due to deactivation of catalyst and time cut in a few minutes, supercritical transesterification in high temperature and

pressure can tolerate presence of high percentage of water in the feedstock [40–42].

Several studies have shown that there exists an immense potential for the production of plantbased oil to produce biodiesel. Azam et al. [11] studied the prospects of fatty acid methyl esters (FAME) of some 26 non-traditional plant seed oils as potential biodiesel feedstocks. Among

5. Biodiesel production from non-edible oil

/s) seed oils may have a slightly higher

http://dx.doi.org/10.5772/intechopen.73304

207

/s) and rubber (76.4 mm<sup>2</sup>

4. Barrier of transesterification process for non-edible oils

tion occurs very fast at an exponential rate.

chain FFA, polanga (72.0 mm<sup>2</sup>

potential to be biodiesel feedstocks.

bility, and raise NOx.

Sources: Azam et al. [11], Ghadge and Raheman [35], Karmee and Chadha [42], Puhan et al. [30], Ramadhas et al. [5, 29], Tiwari et al. [16], Sahoo and Das [20], Islam et al. [53].

Table 1. Characteristic and composition of several non-edible oils compared to diesel.

temperature properties and are suitable as biodiesel feedstocks (Figure 3). Higher concentrations of saturated fatty acids can increase cloud point (CP) and cold filter plugging points (CFPP), which makes them undesirable as liquid fuel [31, 32]. On the other hand, unsaturated fatty acids helps to maintain oil in liquid form, but if the concentration of polyunsaturated fatty acids exceeds certain limit they can form polymers under heat which can block the fuel system of a vehicle [11]. The oils with larger proportion of saturated fatty acids will be more stable than those having larger portion of unsaturated fatty acids. But again, higher proportion of saturated fatty acids lowers the temperature for becoming solid even in the room temperature.

Figure 3. Distribution of fatty acid and its influence on the characteristics of biodiesel in different non-edible oils.

The presence of double bond in the fatty acid brings diesel on poor stability. This decomposition occurs very fast at an exponential rate.

The amount and type of free fatty acid (FFA) in the biodiesel determines the viscosity, one of the most important characteristics of biodiesel. Due to the presence of higher amount of long chain FFA, polanga (72.0 mm<sup>2</sup> /s) and rubber (76.4 mm<sup>2</sup> /s) seed oils may have a slightly higher viscosity compared to others. Karanja and mahua oil has similar viscosity, due to the presence of same FFA. Iodine value represents the degree of unsaturation and relatively high iodine value is reported in range 69.3 in neem to 135 in rubber seed oil (Table 1 and Figure 1). These properties are relatively applicable in cold climates. From calorific value, non-edible oils have potential to be biodiesel feedstocks.

Cetane number (CN) is widely used as diesel fuel quality parameter related to the ignition delay time and combustion quality [14, 32]. Higher cetane numbers in all vegetable oils listed in Table 1, will give better ignition properties. Cetane number increases with the increase of saturated fatty acid, and increases linearly with the chain length, decrease with number of double bonds and carbonyl groups move toward the center of the chain. High level of saturated fatty acid (C14:0, C16:0, C18:0) raise cloud point, cetane number, NOx, and improve stability, while more polyunsaturated (C18:2, C18:3) reduce cloud point, cetane number, stability, and raise NOx.
