The term "residual biomass" refers to waste products from biomass resources that can be used to generate electricity. Residual biomass can be found in manufacturing processes or in the environment as an unwanted component. Biomasses are valuable renewable resources that can be exploited to solve the energy problem while reducing greenhouse gas (GHG) emissions at the same time. Residual biomass feedstock is widely available around the world, and it can be used to recover not only energy, but also biofuels and biomaterials. Using residual biomass offers the dual benefit of reducing the quantity of trash that must be disposed of in landfills while also lowering the demand for fossil fuels, lowering greenhouse gas and pollutant emissions. Biomass can thus provide a renewable energy source that can be exploited today and in the near future, improving the economy and ensuring energy security in a sustainable manner. To directly produce energy or extract biofuels and biomaterials, thermochemical, biochemical, or physical–chemical conversion pathway operations are required due to the chemical and physical composition of biomass.