Synthesis and characterization of Salicornia bigelovii and Salicornia brachiata halophytic plants oil extracted by supercritical CO2 modified with ethanol for biodiesel production via enzymatic transesterification reaction using immobilized Candida antarctica lipase catalyst in tert-butyl alcohol (TBA) solvent

A renewable clean energy is sine qua non for mitigation of toxic and greenhouse gas emissions, preservation of natural ecosystem, biodiversity and its sustainability. Hence, this research work focuses on the evaluation of biofuel potential characteristics of Salicornia plant's oil (halophytes) that grows in arid and salt water environment devoid of suitable edaphic and ecological factors that could support the growth and development of normal vegetable plants. Two species of the Salicornia plants were investigated. These are Salicornia bigelovii and Salicornia brachiata. A supercritical fluid extraction (SFE) process using carbon dioxide (CO2) modified with ethanol as extraction solvent yielded 32.14% of S. bigelovii oil and an oil yield of 26.58% S. brachiata. The fatty acid compositional analysis was determined by Agilent, HP6890 gas chromatograph with flame ionization detector (GC-FID). A 30% concentration of Candida antarctica lipase catalyst that was immobilized on a macro-porous, acrylic resin particles was used for the transesterification process. While biodiesel yield of 92.80% and 81.30% were obtained with t-butanol solvent, a yield of 59.34% and 48.76% was obtained in solvent-free system for S. bigelovii and S. brachiata, respectively. Finally, S. bigelovii biodiesel exhibited better cold flow properties but with very poor fuel critical characteristics, such as low cetane number, high iodine value and low heating value, which when applied in diesel engine could result in abnormal combustion, performance and emission behaviour. Whereas, S. brachiata showed a superlatively promising biodiesel fuel characteristics that is typical of those recommended by American and European biodiesel standards, and thus a technically viable diesel alternative in compression-ignition engines.