Recent work regarding biorefineries resulted in many competing concepts and technologies for conversion of renewable bio-based feedstock into many promising products including fuels, chemicals, materials, etc. The design of a biorefinery process requires, at its earlier stages, the selection of the process configuration which exhibits the best performances, for a given set of economical, technical and environmental criteria. To this end, we formulate a computer-aided framework as an enabling technology for early stage design and analysis of biorefineries. The tool represents different raw materials, different products and different available technologies and proposes a conceptual (early stage) biorefinery network. This network can then be the basis for further detailed and rigorous model-based studies. In this talk, we demonstrate the application of the tool for generating an early stage optimal biorefinery concept for a lignocellulosic biorefinery. More specifically we highlight the required information management (management of various sources of data), the superstructure which is needed to represent the design space, generic but simple models covering all the processing steps of biorefineries, and the formulation and solution of an MINLP problem to identify the optimal processing route for multiple raw materials and products. Finally, economic, sustainability and LCA analysis are performed.