This book provides information on the applications of lignocellulosic wastes, aquatic weeds, algal biomass and microbes in biofuel production, climate change mitigation, eco-restoration, environment protection and development of roadmap for circular economy. Approximately eighty percent of the current energy requirements are fulfilled from fossil fuels which may be exhausted in the next fifty years if their exploitation rate continues with the same pace. Additionally, many health-related disorders like respiratory diseases, cancer and tumour are directly associated with the release of toxic gases during burning of fossil fuels. Therefore, transition from fossil fuels derived energy to low-carbon source energy is required for reduction in global carbon footprint. Excessive exhaustion of fossil sources and their high cost and adverse effects on environment have compelled researchers to develop alternative energy sources. Thus, biomass to bioenergy conversion technologies have been considered as the most promising approach for environment protection and sustainable development. This book comprises latest information on advanced technologies and future directions for researchers and scientists working in the field of biorefinery, wastewater and solid waste treatment and carbon neutrality for environmental safety. It can also serve as a guide to environmentalists, microbiologists, biotechnologists, environmental engineers and managers, policy makers, and industrialists, working in this field.