Perspectives in desulfurization of coal using microbes

Coal is one of the most commonly utilized fossil fuel for energy production across the globe leading to higher amount of emission of sulfur dioxide (SO2) in the atmosphere. Combustion of coal containing higher contents of sulfur is a major factor responsible for acid rain and associated environmental degradation. The currently used physicochemical approaches for removal of sulfur from coal are expensive, toxic in nature, and inappropriate for different types of coal. The application of microbial resources for removal of sulfur from coal is an ecofriendly technique and could be successfully employed at industrial scale after laboratory scale process optimization. The process of sulfur removal by microbes is carried out by enzymes and is considerably influenced by different factors, including pH, temperature, nutrient composition, shaking or standing condition, coal types, and most importantly type of microorganisms used. Different bacteria and fungi isolated from coal contaminated site as well as noncontaminated site exhibiting sulfur removal potential can be used as next generation tool for the development of clean coal technology. Furthermore, through the application of modern genetic manipulation techniques, enhanced expression of genes responsible for desulfurization can be performed in order to accelerate the process of sulfur removal from coal. The present chapter is prepared with an aim to discuss the diverse microbial population participating in desulfurization, their efficiency, mechanism of sulfur elimination, role of important environmental factors along with possible applications, and challenges in industrial scale sulfur removal.