Value Chain Optimization Model for a Softwood Biorefinery Based in Scotland

There is a push towards sourcing chemicals and materials from renewable feedstock such as lignocellulosic biomass. Value chain assessment is used to evaluate the feasibility of the use of a certain technology and feedstock to produce various chemical sources in a given location. In this work an optimisation model for the value chain assessment of a lignocellulosic biorefinery was developed using mixed integer linear programing. The model allows for a comparison of two product sources which undergo mechanical and/or chemical pretreatment prior to processing by the biorefinery into three product streams, delivered to the customer. Optimisation identifies the optimal source or sources of feedstock and the locations of intermediate storages, pretreatments, biorefinery(ies) and customers with respect to maximising profit. The model was verified based on a case study detailed in Scotland. The case study evaluates the use of felled softwood and/or to the use of sawmill by-products with the production of hemicellulose, lignin and cellulose. The results and implications of the optimisation of the scenario are discussed with respect to costs of transport, processing and product values.