Using seawater-based Na2CO3 medium for scrubbing the CO2 released from Bio-CNG plant for enhanced biomass production of Pseudanabaena limnetica

Sagar Jayant Rambhiya,Chaitanya Sampat Magar,Manjushri Arun Deodhar

doi:10.1007/s42452-021-04271-7

Sagar Jayant Rambhiya, Chaitanya Sampat Magar + Show 1 more

Open Access

https://doi.org/10.1007/s42452-021-04271-7

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Abstract

The concentration of CO2, one of the most important greenhouse gases (GHG), has reached to 409.8 ± 0.1 ppm in 2019. Although there are many carbon capture and storage (CCS) methods, they are very costly and their long term use raises concern about environmental safety. Alternatively, bio-sequestration of CO2 using microalgal cell factories has emerged as a promising way of recycling CO2 into biomass via photosynthesis. In the present study, Indigenous algal strain Pseudanabaena limnetica was cultivated in pneumatically agitated 60-L flat-panel photobioreactor system. The gas was released from Bio-CNG plant as by-product into Na2CO3-rich medium and cultivated in semicontinuous mode of operation. It was observed that when CO2 was sparged in seawater-based 0.02 M Na2CO3 solution, maximum CO2 was dissolved in the system and was used for algal cultivation. Control system produced 0.64 ± 0.035 g/L of biomass at the end of 15 days, whereas CO2 sparged Na2CO3 medium produced 0.81 ± 0.046 g/L of biomass. When CO2 from Bio-CNG station was fed, it resulted in biomass production of 1.62 ± 0.070 g/L at the end of 18 days compared to 1.46 ± 0.066 g/L of biomass produced in control system which was not fed with gas released from Bio-CNG plant as by-product. Thus, feeding CO2 directly into Na2CO3 medium and operating the system semicontinuously would be efficient for scrubbing CO2 from commercial Bio-CNG plant. This study proves that feeding CO2 gas from Bio-CNG plant into Na2CO3-rich alkaline system can be used to feed algae for enhanced biomass production.

Highlights

Global warming is being caused due to emission and increase in three greenhouse gases (GHGs), namely CO2, methane and N 2O
Indigenous halophilic strain Pseudanabaena limnetica (Lemm.) Komárek was used for CO2 sequestration studies along with mass cultivation. CO2 sequestration studies were carried out in previously designed, constructed and operationally optimized 60-L flat-panel photobioreactor system for growth of P. limnetica
To enhance maximum C O2 dissolution and holdup, different alkaline systems were studied in seawater and tap water out of which 0.02 M N a2CO3 in seawater was the best solutions which could hold maximum CO2

Summary

Introduction

Global warming is being caused due to emission and increase in three greenhouse gases (GHGs), namely CO2, methane and N 2O. Atmospheric C O2 concentration in 2018 was 407.3 ppm which increased by 2.5 ± 0.1 ppm in 2019 [1]. The Kyoto Protocol and the Paris Agreement (2015) have asked the participating countries to curb climate change impact by setting up policies out of which crucial are CO2 emissions by reducing fossil fuel usage and increasing carbon capture and sequestration [2, 3]. Most of chemical or physical means of capture of CO2 from smoke stack emission involve three major steps which are carbon capture, separation and storage which enormously increase the cost of project. Microalgae possess inbuilt mechanisms to capture C O2 from the atmosphere even in smallest concentrations. These mechanisms are referred to as carbon capture mechanisms

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