17.15. Advantage of Biodiesel Over Higher Plants
Algae from either eukaryotes or prokaryotes are wide diverse group of photosynthetic organisms and have attracted significant attention as renewable energy feedstocks due to their rapid growth rate, biomass production, and great potential to synthesize fatty acids which can be converted to biodiesel [131,132] when compared to oleaginous plants [133]. In addition, its oil content is usually between 10% and 50% of their dry cell weight and in some cases some species can produce 80% of oil under certain growth conditions [134,135].
Microalgae possess the following advantages over higher plants:
1. They grow at high rates and can synthesize and accumulate large quantities of neutral lipids (20–50% dry weight of biomass).
2. They can exceed the oil yield of the oilseed crops of all year round production because it can grow in continuous cultures for long time providing a reliable and continuous supply of oil.
3. The consumption of water by microalgae is less than that for terrestrial crops, therefore it saves freshwater resources in case of cultivation of freshwater algae species.
4. Microalgae cultures do not require herbicides or pesticides application.
5. They can reduce emissions of greenhouse gas through exploiting CO2 from flue gases emitted from fossil fuel–fired power plants and other sources in photosynthesis process.
6. They can grow on wastewater from different sources, such as agricultural runoff, animal feed wastes, industrial, and municipal wastewaters, and have the ability for bioremediation by removal of ammonia, nitrate, phosphate, and toxic metals.
7. They can be cultivated in saline water on nonaerable land and do not compete for resources with conventional agriculture.
8. According to the microalgae species, other valuable compounds may also be extracted, which can be used in different industrial sectors, including a large range of fine chemicals and bulk products, such as polyunsaturated fatty oils, antioxidants, polysaccharides, pigments, and natural dyes.
10. Microalgal biodiesel has a higher photon conversion efficiency and produces nontoxic and highly biodegradable biofuels [139].
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