Enrichment of Biogas by Microalgal Scrubbing System and Value added Products Synthesis

Abstract

Biogas is composed of CH4 (50-60%) and CO2 (40-50%), therefore scrubbing (removal) of CO2 from biogas is imperative as high concentration of it reduces the calorific value and limits its end application. Problems associated with physiochemical process can be alleviated through microalgae as they are efficient in utilizing the CO2 as its carbon source that can be technically termed as CO2 sequestration. This study aims to apply the use of a microalgae CO2 capturing system using Chlorella sorokiniana and Scenedesmus obliquus that have higher photosynthetic capacity and sequestration of carbon dioxide subsequently and transforming into biomass. Chlorella sorokiniana had a total biomass yield of 1.59 g/L and 1.98 g/L for unpurged and purged respectively. Scenedesmus obliquus on the other had a better yield over Chlorella sorokiniana with an overall biomass of 1.7 g/L for unpurged and 2.4 g/l under mixotrophic condition. Upon analysis of lipid content in the biomass, the cultures that were grown under mixotrophic condition were found to yield 3.45 and 3.28 fold higher as compared to unpurged sample in Chlorella and Scenedesmus respectively. Under purged conditions, Chlorella sorokiniana had the maximum yield of 5.5 mg/g of vitamin E compared to Scenedesmus obliquus with a comparatively lower yield of 2.32 mg/g. Overall, the increase in the specific growth rate and doubling time indicated that a better adaptability and utilization of carbon source in the purged sample which was provided in the form of 50% citric acid and carbon dioxide. This provides evidence in support of Chlorella sorokiniana for having a higher potential in the area of nutraceuticals. Along with purifying the biogas produced from an anaerobic digester fed with food waste.