11. Biorefineries: Focusing on a Closed Cycle Approach with Biogas as the Final Step

The increasing energy demands as a consequence of fast-growing global population and higher living standards over the last few decades have triggered huge interest in finding new energy resources. In this context, biomass is an environmentally friendly renewable resource with huge potentials to generate power as well as various useful chemicals and fuels. Biorefineries which are analogous to today’s petroleum refineries are identified as a processing facility that can use biomass as feedstock to produce these value-added products. Although being promising, biorefineries face some serious limitations and constraints as well. For instance, for upscaling biorefineries, a considerable infrastructure would be required to make possible the collection and storage of a large amount of biomass. The economic and sustainable processing of raw materials in biorefineries requires advanced and sophisticated technologies most of which are still at a pre-commercial stage. Food security, high energy demand, production cost, seasonal diversity, land use change effect, etc. are also among the other important topics in question. The objectives of this chapter are to review the concept of biorefinery, introduce different types of biorefineries and their classifications, overview associated barriers and obstacles to biorefineries, and evaluate various potential feedstocks for biorefining process. Finally, the potential of integrating anaerobic digestion to biorefinery platforms is discussed and the advantages and drawbacks are reviewed.