Biodiesel Production and Characterization from Indigenous Mixed Algal Biomass

Abstract

Rapid urbanization and industrialization in 20th and 21st century brings the scarcity of fossil fuel resources. On top of that, these are the main causes of greenhouse gas emission and global warming. Research works on alternative fuels including biofuels are taking place throughout the world. Many of the resources and sources for energy production have been invented and discovered in last few decades. Biodiesel, one of the alternative and renewable source of energy, produced from different oils and fats has become prominent in these days. But it is economically incompatible with petroleum diesel. Algal fuel, on that perspective, is very new but might be one of the most promising fuel sources in near future. Algae’s faster growth rate along with high oil content has drawn the attention of researchers worldwide. First world countries like USA is investing billions of dollars for the research on algal fuel. But in India, where the necessity is much more, very few research works are taking place. Researchers have proved that all three types of biofuels i.e. biodiesel, bioethanol and biogas can be produced from algal mass. Algae, on the other hand, utilize CO2 for their growth and can be minimized some sort of pollution. In Punjab, India, algae grow rapidly in several water-bodies. But all those are not used by anybody for any purpose. This biomass was used to produce biodiesel in this research work. The algae were collected from pisciculture- ponds and a canal called Simlapuri Nahar. The growth parameters of these algae were optimized in terms of maximum yield of biomass with paramount oil content. It was found4l/pond CDS, 30ml/l CO2, 0.5m water depth, 5°C- 10°C temperature and ‘every 1.5h’ mixing intensity are the optimized conditions for the growth of these algae. Almost 12kg of algae was produced from 5kg of algae and the oil content of the increased to almost 12% from 8.9% under optimized conditions. A statistical analysis proved that the most contributing parameters, for the growth of these algae and increase of oil content of the same, were the nutrient (cow dung slurry) and the temperature. Experiment was done to find out a solvent with most capacity of oil extraction. An amount of 8.9% of algal oil was extracted by the mixture of hexane and acetone (1:1). The lowest quantity of oil was extracted, from dried algae, by methanol (3.4%). In the transesterification reaction for biodiesel production, methanol to oil molar ratio of 6:1, catalyst concentration of 3%, reaction temperature of 60ᵒC and reaction time of 60minutes were found to be the optimum conditions to get maximum FAME of 96% and minimum free fatty acid (FFA) content of 0.18%. A statistical analysis for the transesterification procedure also were carried out to find out the contribution of parameters. For, highest yield of biodiesel, catalyst concentration was found to be the dominant contributing parameter. On the other hand, for lowest FFA content, methanol to oil molar ratio exerted highest contribution. To find out percentage of conversion of algal oil to algal biodiesel was calculated by means of the NMR graph of algal biodiesel. The conversion was found to be of around 96%. Therefore the yield of the biodiesel, from indigenous mixed algal biomass used in this experiment was almost 93%. Important properties of the FAME produced like viscosity (3.12 mm2/s), cloud and pour point (−1 ᵒC and −6 ᵒC respectively), flash and fire point (153 ᵒC and 158 ᵒC), Carbon residue content (0.03%), acid number (0.36 mg of KOH/gm) were within the range of concerned limits of ASTM/ BIS standards. It was found that apart from NOx, the emission of other gases (CO, CO2 and hydrocarbon) were lower for the combustion of this algal biodiesel than that of petro- diesel. While CO and HC emission were found to decrease with increasing engine load, the emission of CO2 and NOx increased with increasing engine load. Same incident was found to be occurred for the combustion of algal biodiesel- petro- diesel blends. Therefore the biodiesel produced in this experiment was found to be very eco- friendly and engine- friendly.