Biomass is a promising feedstock for a future sustainable economy. A systematic approach is used in this research work to develop an optimization framework for the optimal design of a sustainable biorefinery that produces biofuels and bioproducts. The superstructure is developed and implemented in the General Algebraic Modelling System (GAMS) software. This study considered a multi-objective optimization approach in which Economic and Environmental impact are the objectives to be optimized under prospective conditions. The economic objective function considers the total net profit of the biorefinery which represents the difference between the income and the total cost. The income accounts for the sales of products while the total cost includes the capital and operational cost. A modular approach and open source simulation software BioSTEAM is used to calculate the capital cost estimation of wheat straw biorefinery system. Organosolv pre-treatment method is used in this study. Although organosolv pre-treatment is more costly than other pre-treatment processes, but it has the potential to yield valuable products and by-products. The aim of this study is to utilize a superstructure approach in order to optimize the organosolv pre-treatment method for a wheat straw biorefinery system, with the goal of producing low-cost and environment friendly biofuels and biochemicals.