In a typical palm oil processing plant, which is also known as palm oil mill, various types of palm based biomasses (e.g., empty fruit bunch (EFB), palm press fibre (PPF), palm kernel cake (PKC), palm kernel shell (PKS), sludge cake, etc.) are generated from the processing of fresh fruit bunches (FFBs) to produce crude palm oil (CPO) as the main product. At the initial stage, these biomasses are considered as low-value by products or waste. However, due to the maturity of palm biomass processing technologies and new initiatives given by Malaysian government, many of the palm oil mills have started to further process those biomasses into higher value products, such as biofuels, biochemicals, and bio-based food. This paper presents a novel application of the concept of systematic optimisation approach to retrofit a palm oil mill into a sustainable palm oil-based integrated biorefinery. In this work, the retrofit of an existing palm oil processing plant is analysed based on economic performance and the total potential environmental impact of the entire plant. In this context, the challenge lies in maximising the former whilst minimising the latter simultaneously. In the light of addressing this concern, fuzzy optimisation approach is adapted into this work to synthesise a sustainable palm oil-based integrated biorefinery which fulfils the two important objectives. Pareto optimum analysis is also performed to this new retrofit design case in order to determine the optimum pathway with the consideration of both objective functions. Sensitivity analysis is also conducted in this work to determine the effects of cost and price fluctuations on the economic performance. A palm oil mill case study is presented to collectively illustrate the proposed approach. (C) 2012 Elsevier B.V. All rights reserved.