Bioconversion of chemically captured carbon dioxide into microalgal lipids, a potential source of biodiesel: An integrated technique

Abstract

The rise of atmospheric carbon dioxide (CO2) concentration due to extensive anthropogenic activity besides rapid exhaustion of non-renewable energy sources demands evolution of clean and ecofriendly alternative fuel source. Recently, lipid rich microalgal biomass is being considerably researched for generation of biodiesel conversely, the expenses incurred on production of microalgal biomass is a substantial obstacle. Almost 80 % of the production cost is generated from the cultivation medium which majorly consists of carbon, nitrogen and phosphate. CO2 absorption by means of aqueous amine solvents is known to be a mature technology and could be integrated with microalgal cultivation unit for efficient utilization of the captured CO2. In this current investigation, piperazine (PZ) promoted aqueous blend of methyldiethanolamine (MDEA) having mass percentage ratio of (8/22 wt%) was used a CO2 capturing agent and then the captured CO2 was utilized as an inorganic carbon source for growing Chlorella sorokiniana BTA 9031 for biodiesel production. The CO2 absorption rate was governed by series of process variables namely, absorption temperature, initial CO2 concentration, solvent flow rate, gas flow rate and the optimal conditions were 315 K, 15 kPa, 3.6 × 10−4 m3 min−1 and 4 × 10−3 m3 min−1 respectively. The highest biomass strength of Chlorella sorokiniana BTA 9031 was observed to be 1.20 ± 0.028 g L−1. The fatty acid methyl esters (FAME) profile was determined after acid transesterification of the extracted microalgal lipids. It was observed to contain fatty acids suitable for biodiesel production.