Sugar crops or starch based integrated biorefinery incorporates second (2G) generation ethanol production based on abundant lignocellulose feedstock into first (1G) generation ethanol production process with a possibility to issue various co-products such as sugar, molasses, electricity etc. This novel concept is promising to enhance the traditional 1G biorefinery and replace refinery based on fossil fuels. However, further economic and environmental investigations are required. This chapter presents a comprehensive analysis of the existing approaches and key issues in the life cycle assessments (LCA) methodology applied to evaluate environmental performance of sugar or starch based integrated biorefineries. Moreover this chapter includes an economic analysis and details of process design and technological achievements in integrated biorefineries. Several scenarios of integrated sugar based biorefineries that could produce 1G and 2G ethanol, sugar, molasses, C5 syrup (for animal feed) and electricity were evaluated and compared according to the proposed methodology.