The adverse effect of global warming and the energy crisis due to fossil fuel depletion has paved the substitutive way for the development of green energy production. Presently, conventional energy sources such as coal, petroleum, and natural gas fulfill 80% of primary energy demand across the world but are consequently depleting rapidly and causing an increase in greenhouse gas (GHG) emissions. The major pollutants are carbon dioxide (CO2), nitrous oxide (NO2), and methane (CH4), which cause changes in climatic conditions. Consequently, there is an urgent need for the evolution of renewable and sustainable energy resources like biofuels. Biofuels derived from plants, food, and non-food crops have been highly criticized by the scientific community and technocrats due to their extensive land usage, leading to the food versus fuel dilemma. Therefore, researchers have turned their attention towards biofuel production from eukaryotic photosynthetic microbes-microalgae.
Microalgae have the innate ability to capture atmospheric CO2, reducing climate change impact. Microalgae are considered a source of third-generation biofuel and are among the fastest proliferating photosynthetic biomass on earth, with a high intracellular lipid content categorizing them as a green and sustainable source of fuel. There are various sequential steps that are usually involved in microalgae biodiesel production including cell cultivation, harvesting, lipid extraction, and fatty acid methyl ester (FAME) generation. In order to grow, algae require water, CO2, and micronutrients, which are termed a “culture medium”. Most of the algal strains are photoautotrophic in nature where light energy is harvested and CO2 is used as a carbon source. However, the photoautotrophic cultivation mode is quite insufficient for high biomass and lipid production from algae as less light penetration and mutual shading of the algal cells cause light inadequacy and hence, the growth rate decreases earlier.
In the case of a few algal species, like Chlorella pyrenoidosa, Chlorella sorokiniana, Scenedesmus sp, etc., a mixotrophic culture condition exists where CO2 and organic carbon both are utilized simultaneously in the metabolic pathways of photosynthesis and respiration. The cells are provided with organic carbon supplementation leading to enhance biomass production with improved lipid accumulation making them a better source for biofuel application. Techno-economic evaluation of microalgae-derived lipid production is a key factor for cost analysis, which may lead to commercially viable biodiesel development. Microalgae are being eagerly explored for commercial and industrial applications.
The use of microalgae biomass for the production of pigments, antioxidants, proteins, and natural colorants in food, and wastewater treatment has been successfully reported. Microalgae have emerged as a feasible source in the major application of life sciences such as bio-hydrogen, bio-fertilizers, bioelectricity, food supplements, and biofuels. In the field of sustainable energy sources, biofuels-liquid fuels from numerous biological resources have achieved great momentum due to lower emission levels than petrol. Extensive research is underway on biofuel synthesis from microalgae to address the current energy crises. During the oil crises in the 1970s, numerous renewable energy programs were implemented involving microalgae biofuels by NREL formerly known as US Aquatic Species Program. In recent years, the expansion in the field of microalgae biodiesel production is mainly due to the increasing pressure to find fossil fuel alternatives. Environment and cost consideration are also important topics for further study. The cost of cultivation can be reduced by growing microalgae in rural areas, where land prices are comparatively lower than in urban areas. Furthermore, microalgae cultivation with fish or shrimp uplifts the productivity of animals and improves the quality of water. Microalgae can be grown in wastewater effluents in order to replace synthetic media, as a cost-effective approach.
Hence, we could envisage that sustainable and renewable energy production from microalgae could play an essential role in a successful biodiesel synthesis, serving as an eco-friendly green solution.
Dr. Anwesha Khanra
Assistant Professor
School of Biosciences
IMS - Ghaziabad
(University Courses Campus)
