Bio-based products can be classified into three categories: Biofuels (biodiesel, bioethanol, biogas), bioenergy (heat and power), and bio-based chemicals and materials (fine chemicals, cosmetics, polymers, plastics, composites). In a biore­finery, the biomass conversion processes are integrated in such a manner that almost all types of feedstocks can be converted to the above-mentioned products. Biofuels are produced in higher volumes and are responsible for increasing the carbon credits of the industry, whereas other products such as fine chemicals, pharmaceuticals, and polymers are produced in comparatively lower quantities, but, being high value products, increase the profitability of the biorefinery.

Biomass processing in a biorefinery involves two major transformations [3] the first transformation involves a bulk separation or extraction of the biomass using processes such as grinding, followed by fractionation or cracking by biological or physicochemical techniques. This step leads to release of such molecules from the biomass which are capable of undergoing second transformation involving pro­cesses such as fictionalization to yield a variety of molecules. These transforma­tions give rise to a large number of bio-based products in which the most important one can be considered to be biofuels/energy (Fig. 1.21).

Integrated biorefineries employ various combinations of feedstocks and con­version technologies to produce a variety of products, with the main focus on producing biofuels. Side products can include chemicals (or other materials) and heat and power.

This section focuses only on the energy aspects of biorefinery, though, other valuable products are also available from biorefinery [36, 37].