Fatty Acid Profiles and Fuel Properties of Oils from Castor Oil Plants Irrigated by Microalga-treated Wastewater

Abstract

Microalgae can function as a bio-fertilizer and a bio-filter for wastewater treatment, thus allowing the re-use of wastewater for the irrigation of plants that produce abundant bio-oils and for the irrigation of low-quality soils. Chlorella vulgaris was grown in Om El-Resh drain water as growth medium, after enrichment with nitrogen and phosphorous. Castor seeds were cultivated in a greenhouse at the Algal Biotechnology Unit, National Research Centre, Egypt. Fifteen days later, transplants were irrigated by untreated wastewater (WW); wastewater treated with microalgae (WW+A); or wastewater treated with microalgae followed by removal of microalgae (WW-A). Oil extraction was performed by seed warming and grinding with n-hexane, followed by soaking, filtration, and passage through Silica gel 60. Esterification was performed, and then fatty acid methyl esters (FAMEs) were determined. The results indicated that the wastewater treatment markedly affected seed oil content. The WW+A treatment led to the highest seed oil yield (41.8%), followed WW-A treatment (28.14%), and the WW treatment (25.12%). FAME analysis indicated that the presented fatty acids of castor oil were C16 and C18 and ricinoleic acid (C18:1) was the most abundant (83.1 to 84.63%). In spite of the higher seed oil content when plants were grown in WW+A, there were differences in the fuel proprieties of seed oils in the different groups, based on American Society for Testing and Materials criteria. Our results suggest that wastewater can be successfully used for irrigation of soils that have poor fertility to produce bio-oils during land reclamation.