The processing procedures and technologies applied for the conversion of biomass depend mainly on the targeted biomass use, e.g. food, feed, materials or energy, and are mainly determined by the origin, components and physical/general characteristics of the biomass. Biorefining is an integrative and multifunctional overall concept that integrates different processes and technologies (upstream, midstream and downstream operations) using biomass as a diverse source of raw materials to generate a spectrum of intermediate or final products for diverse purposes. Biorefineries can be characterised according to the raw materials used, the processing technologies applied, the platforms, the intermediate and final products they provide, and their size. In this section, the practical functioning of biorefineries is illustrated using the examples of a sugar factory and a pulp mill as traditional biorefineries. A grass biorefinery for the production of biocomposite materials is presented as an example of a more recently developed biorefinery concept. Common to all biorefinery technologies is that they make full use of biomass for different products and incorporate the principle of circularity to close material and energy cycles.