Brewer's spent grain (BSG) is one of the most important byproducts of the brewing industry and its composition offers opportunities for developing value-added products. The objective of the research was to investigate the application of the biorefinery approach for production of xylitol, ethanol and polyhydroxybutyrate from BSG. The techno-economic and environmental aspects of two biorefinery scenarios, with and without heat integration, were studied. Results indicated that a standalone production of fuel ethanol from BSG was not feasible, the production of polyhydroxybutyrate was feasible only with heat integration and that the production of xylitol was feasible either with or without heat integration. Results indicated a calculated total production cost of 0.35, 3.63 and 3.36 USD/kg for xylitol, ethanol and polyhydroxybutyrate, respectively. Results suggested that heat integration allowed reducing the energy consumption associated with manufacturing all of the products in the biorefinery by 43%. Results of the environmental assessment indicated that heat integration lowered the potential environmental impact of the BSG processing. Results of the study thus indicated the superiority of a biorefinery for BSG processing that includes heat integration, from both the techno-economic and environmental impact points of view.