**4. Discussion**

The great potential exists for using non-edible seed oil as biodiesel, which has been highlighted in this chapter. The plant sources explored were *Koelreuteria paniculata*, *Rhus typhina*, *Acacia farnesiana* and *Albizzia julibrissin*.

Biodiesel can be synthesized from vegetable oils, animal fats or algae oils [51]. The Soxhlet extraction allows the sample to repeatedly bring into contact with fresh portions of extracting materials, hence facilitating the equilibrium. It remains at relatively high temperature and no filtration is required [52]. In the present study, *Koelreuteria paniculata* produced highest biodiesel oil content by Soxhlet extraction (28–30%) followed by the *Albizzia julibrissin* (19–24%), *Acacia farnesiana* (23%), *Rhus typhina* (20–22%) than the mechanical extraction.

The biodiesel production largely depends upon the choice of appropriate, costeffective and environment friendly catalysts [53] based on the nature of oil which greatly help in transesterification of oil. Density optimization is a vital biodiesel factor having huge impact on fuel quality as well the cost incurred [54]. The density for all plant sources ranged from 0.83–0.87 @ 15°C (g/cm3). The kinematic viscosity ranged from 3.75–6.3 (mm2 /s) among all the plant sources. Our results show that densities of all plant sources were within the ASTM (D6751) and (EN14214) standards.

The 1H-NMR procedure is used to evaluate the un-saturation and "residual" fatty acid composition [55]. In our study, the biodiesel 1H NMR (300 MHz) spectrum was noted with a cycle delay of 1.0 s, and eight times scans with a pulse duration of 30°. 13C NMR spectroscopic data represented the chemical shift values matching to various structural features in FAMEs.

The metals such as Cu, Co, Fe, Mn and Ni are known to catalyze oxidative degradation reactions in vegetable oils and biodiesel [56]. The presence of some metals, such as Al, Ca, Cr, Cu, Fe, Mg, Pb, V and Zn, among other, in fuel is undesirable due to their release into the atmosphere upon fuel combustion [57]. *Koelreuteria paniculata* had highest Na (5456.2), Cr (1246.8), Ni (658.36), and Al (346.87) elemental concentrations (μg/g) than other plant sources. Moreover, Al, Cr, Sn, V, Cu, Bi, Cd were not detected in *Acacia farnesiana* and *Albizzia julibrissin* and both showed comparable Zn, K, Ni, Mn, Ca, and Co concentrations with petro diesel. The metal elements in biodiesel result into engine degradation, operational as well as cause environmental pollution [58]. In our study, the elemental percent of C, H, N, and O of biodiesel ranged from 72.54–76.86, 11.25–13.34, 1.97–2.73, and 9.86–12, respectively.

Flash point of fuels is imperative to determine the prerequisites for transportation and storage temperature [59]. The flash point was highest in the biodiesel oil of *Rhus typhina* (168°C), *followed by Albizzia julibrissin* (160°C)*, Acacia farnesiana* (158°C), *Koelreuteria paniculata* (147°C) which was comparable to EN 14214 (Min. 120°C), ASTM D-6751 (Min. 130°C) petro diesel (60–80°C) standards.

The main shortcomings of biodiesel are related to the low-temperature performance and oxidation stability. The oxidation stability (110°C, h) was recorded as 18.3 *in Rhus typhina*, 4.71 in *Albizzia julibrissin*, −1.86 in *Acacia farnesiana* and these fall in the recommended values of EN 14214 (Min. 6), ASTM D-6751 (Min. 3) and petro diesel (25.8). This highlights that the saturated fraction of biodiesel has a positive effect on its stability as in the case of our results, but the long-chain saturates may compromise fuel performance at lower temperatures [60].

Metal-containing fuel additives and un-removed catalysts are the major contributors of sulfated ash [61]. The sulphated ash content (%) was not detected in *Rhus typhina*, *Acacia farnesiana*, *Albizzia julibrissin* and it was 0.003 in *Koelreuteria*  *Optimization and Characterization of Novel and Non-Edible Seed Oil Sources for Biodiesel… DOI: http://dx.doi.org/10.5772/intechopen.97496*

*paniculata* as compared to the EN 14214 (Max.0.02) standards, hence these plant sources can be used for biodiesel production.
