Sustainability Multidimensional Optimization of Multiproduct Biorefineries: The Case Study in a Sub-Saharan African Country

Multiproduct biorefineries are promising industries to diversify the economy of developing countries. This work proposes a sustainability multidimensional optimization model for multiproduct biorefineries to evaluate the technical, economic, environmental, and social viability and support a multicriteria decision-making. The proposed model was used to evaluate the implementation of new biorefineries in Guinea-Bissau for bunches of fresh palm fruits (PF) and peeled castor seeds (CS) processing into higher added value products. The PF products evaluated in this study were crude oil, refined oil, stearin, and kernel oil, while those of CS were crude oil, refined oil, and stearin. The installation of seven biorefineries in Guinea-Bissau was defined to supply regional markets with these products. Mathematical programming was implemented from optimization models to maximize gross profit and job generation and minimize the transported distances of raw materials and greenhouse gas (GHG) emissions. The biorefineries were subject to water and energy supply constraints, wastewater management, and raw material availability and demand. The data were obtained from secondary sources and compiled in Python programming language. To increase the robustness of the model, an uncertainty evaluation was conducted using Monte Carlo simulation. An availability of 3.66 × 10⁵ ton a year of PF and 1.8 × 10⁴ tons a year of CS was estimated in the base scenario. The model solution indicated the quantity of each product to be produced in the biorefineries to achieve a gross profit of 5.13 × 10⁸ US$ in the base scenario, while it achieved 7.69 × 10⁸ US$ in the optimized scenario for profit maximization. GHG emissions in the base scenario were 1.75 × 10⁸ kg CO₂eq, while these were 9.60 × 10⁷ kg CO₂eq in the optimized scenario. Job generation was 1.24 × 10⁵ in the base scenario and 1.80 × 10⁵ in the optimized scenario. There was a trade-off between profit maximization and GHG emissions minimization. The profit maximization increased GHG emissions by 150%, while by minimizing GHG emissions the gross profit decreased by 63%. Carbon offsetting for partial (only the additional emission) and total GHG emissions in the profit maximization scenario was also simulated at 0.03 US$ (kg of CO₂)⁻¹ and 0.10 US$ (kg of CO₂)⁻¹, which indicated a gross profit increase up to 3.12%. In this regard, it is feasible to offset the total GHG emissions to enable the profit maximization in the evaluated biorefineries.