This special issue mainly focusses on waste to energy production such as agricultural waste and all other organic waste to energy production processes, fossil fuel processing specially low quality coal upgradation, CO₂ Capturing and conversion into different chemicals, catalytic processes for waste water treatments such as photo catalysis and adsorption, Anaerobic solid waste and waste water treatment process and related field of broad scope application of nano-material for energy and environmental  and chemical engineering processes applications.