**Abstract**

Processing of biomass feedstocks to produce energy, fuels, and chemicals via a combination of different applied technologies is considered a promising pathway to achieve sustainable waste management, with many environmental and economic benefits. In this chapter, we review the current state of the main processes associated with energy recovery and biofuel production under the concept of waste biorefineries. The reviewed technologies are classified into thermochemical, biological, and chemical, including combustion, gasification, steam explosion, pyrolysis, hydrothermal liquefaction, and torrefaction; anaerobic digestion, fermentation, enzymatic treatment, and microbial electrolysis; and hydrolysis, solvent extraction, transesterification, and supercritical conversion. Their brief history, current status, and future developments are discussed within a perspective of valorization and managing of current waste streams with no solution.

**Keywords:** biorefineries, biofuel production, energy recovery, waste-to-fuels, waste-to-energy, circular economy
