Utilization of unfiltered LPG-burner exhaust-gas emission using microalga Coelastrella sp.

Abstract

This present study evaluated the potential of an untapped thermo-tolerant microalga, Coelastrella sp. FI69 as a promising candidate for scalability, CO2 bio-sequestration and biomass production. The microalga is preliminarily cultivated in elevated CO2 and finite NO3− growth habitat at outdoor field, and developed from lower to higher volume culture. The scaled up culture is eventually used as seed (in two different initial inoculum density, 0.01 and 0.1 g L−1 DW11Dry weight), in 200 L open rectangular pond (ORP22Open rectangular pond) reactor aerated with LPG combusted exhaust-gas streams (10 vol. % of CO2, 150 ppm of nitrogenous gases at atmospheric pressure and 30–40 °C) for 8–10 days for biomass production. The biomass production rate (BPR33Biomass production rate), maximum specific growth rate (μmax44Maximum specific growth rate), CO2 bio-fixation rate (CBFR55CO2 bio-fixation rate) and maximum biomass density (DB-max66Maximum biomass density) of the microalga culture achieved in the exhaust-gas aeration at 0.01 and 0.1 g L-1 are found as 0.065 ± 0.005 and 0.116 ± 0.011 g DW L-1, 0.467 ± 0.014 and 0.426 ± 0.007 day-1, 0.112 ± 0.008 and 0.202 ± 0.002 g CO2 L-1 day-1, and 0.529 ± 0.037 and 1.047 ± 0.022 g DW L-1, respectively. The harvested biomass had heating values of 20.2–21.7 MJ kg-1, contained 16–20% of lipids, and a theoretical methane potential of 586.2 mL CH4 gVS-1. From the biomass energy potential analysis, the microalga cultivation system, which designed to utilize the combustion-gases for biomass production, could reach a promising higher net energy ratio. This study mostly highlights the significance of using the strain for utilization of CO2-rich gas streams.