Abstract
Recently, intensifying energy crises accompanying ecological crises due to the decline in fossil-fuel reserves and extensive greenhouse gas emissions have triggered the exploration of renewable substitutes for petro-diesel. In this scenario, biodiesel is the best alternative to non-renewable finite conventional fuels due to its cost-effectiveness, sustainability, renewability, biodegradability, and eco-friendly nature. Hence, the current research was designed to utilize scanning electron microscopy to investigate and identify the micro-morphological characteristics of selected seed-bearing crops. Light-microscopy (LM) indicated discrete variations in macro-morphological characters such as seed shape (ovoid, ovate, oblong, semi-spheroid, or discoid), seed size (3.5-14 mm in length and 2.25 to 6.5 mm in width), seed color (yellow to black), and number of seeds per kilogram (from 6000 to 260,000). Chemical extraction via Soxhlet apparatus resulted in the estimation of oil content within the range of 20.3-48.0% (wt./wt.), FFA content (0.63-6.91 mg KOH/g), and maximum product, i.e., 98% biodiesel yield was achieved. Multivariate analysis via principal component analysis (PCA) was done using PAST 3 software to investigate similarities and differences among factors/variables. SEM examination exhibited ultra-morphological characters and distinct variation in cell-wall ornamentation; hilum occurrence, position, and level; wall-sculpturing variations such as ruminate, verrucate, wrinkled, or striate; cell arrangement (anticlinal or periclinal); and cell shape and margins. To conclude, SEM could be an advanced technique to disclose the ultra-micromorphological characteristics of oil-bearing energy crops providing a convenient way for scientists to determine correct identification, authentication, and classification.