Bioenergy generation from components of a Continuous algal bioreactor: Analysis of lipids, spectroscopic and thermal properties

Abstract

Influx of sewage into surface water results in nutrient enrichment and consequently leads to algal bloom and voluminous organic sludge production in urban areas as in case of Bangalore. The lack of utilities of algae and resulting sludge has lead to anoxia and GHG emissions. Environmental friendly ways of sludge and algal biomass utilities as well as disposal are scant. Testing for biofuel and thermal properties can be beneficial to meet the energy requirement to run treatment plants that might have better fuel value to increase the net energy gain in the system. As the volume of algal biomass and quantity of sludge has increased over the past few years, sustainable means of biomass and sludge utilization needs to be devised for beneficial purposes, to keep the surface waters clean and regulate the biomass productivity of such systems. Therefore the biomass and sludge characterization becomes imperative for any further utilities. In the present study the indigenous suspended algae and the algal bioreactor sludge were characterized for the different functionalities and presence of bio-chemicals (carbohydrates, proteins and lipids) through Infrared Analysis (ATR-FTIR). The total lipids and fatty acid methyl esters (FAME) composition were studied. The heat values and thermal decomposition pattern were analyzed by [Thermogravimetry (TGA)/Differential Thermal Analysis (DT) and Differential Scanning Calorimetry (DSC)]. The algae were found to have a better total lipid content of >34 % compared to 22% in case of wastewater sludge with quality FAME for better biofuel properties. However there were higher number of FAME in wastewater sludge (>30) where C16 and C18 members dominated. Algal biomass showed higher calorific value of 17.96 MJkg-1 compared to 10.33 MJkg-1 of wastewater sludge.