A shift to utilize more renewable energy sources has been motivated by issues of energy security, environmental protection, and sustainable development. Biofuels are among the promising forms of renewable energy as they can be produced from a wide variety of feedstocks (e.g., traditional agriculture crops, energy crops, forestry products, municipal solid waste, etc.). Biorefineries are processing facilities that convert biomass into value-added products such as biofuels, specialty chemicals, and pharmaceuticals. To enhance material and energy recovery within processing facilities, an integrated biorefinery is proposed. Since the potential pathways and products in an integrated biorefinery are extensive, product allocation is a complex task. The main challenge in designing an integrated biorefinery is to synthesize a sustainable biorefinery with maximum economic performance while causing minimum environmental impact. Since such objectives are often conflicting in nature, fuzzy mathematical programming is adapted in this work to synthesize a sustainable integrated biorefinery that fulfills both considerations simultaneously.