• Energy Research

Abstract Palm oil mill effluent (POME) is recognised as one of the biggest sources of pollution due to its eutrophying nature and methane emitting treatment. Although biogas recovery and utilisation are promoted through government initiatives, the motivation and support from mills still reported low in Malaysia. This paper aims to discuss the benefits and drawbacks of POME utilisation in the palm oil supply chain based on environmental, social and economic concerns to review the favourability of POME elimination. A zero effluent approach is introduced based on POME evaporation technique, undiluted clarification practice and water recycling strategy as an alternative for conventional POME management approaches. An integrated palm oil complex concept is proposed which includes new palm oil processing approach that eliminates POME and provides industrial symbiosis possibilities within palm oil upstream and downstream sectors to promote sustainability of palm oil industry with balanced economic and environmental advantages. A comparative study between POME utilisation (Case 1 and 2) and POME elimination (Case 3) in different perspectives is included in this work. In the economic view, the payback period of Case 3 is shorter (4 y) compared to Case 1 and 2 (4.3–8.3 y). In comparison, POME elimination technology is more environmentally friendly due to smaller water and land footprint, zero methane emission and minimum waste generation. Approximately 0.3% improvement in oil extraction rate can be potentially achieved by the proposed mill configuration in Case 3. One of the challenges in POME elimination implementation is the additional 0.25 kg steam requirement associated with evaporation of 1 kg water. The study provides insights on the feasibility of the proposed sustainable concept in Malaysia with consideration of government policies and programmes. The suggested POME elimination-based complex provides alternative option to mill owners who are uninterested to invest in biogas capturing facilities.

Abstract Palm oil mill effluent (POME) elimination has been considered recently as the alternative to expensive biogas recovery to conquer environmental criticisms in the palm oil industry involving the release of biogas (i.e., a primary contributor towards climate change), during POME treatment. With POME elimination and mill-refinery integration considered, the integrated palm oil-based complex (POBC) serves as an appropriate system for sustainable food-energy-water (FEW) nexus evaluations. In this respect, multi-objective optimisation and debottlenecking of POBC has been suggested to address the economic and environmental trade-offs in palm oil mill (POM) for cleaner production. In this study, a stepwise debottlenecking framework was proposed to include previous fuzzy multi-objective optimisation approach and a new debottlenecking method to improve the fuzzy optimal POBC design and evaluate the impact of process on FEW nexus contributions. Each process creates distinctive impact or influence on the POBC performance. Shapley-Shubik Power Index (SSI) has been applied in the notion of power for yes-no voting systems. By evaluating the operate-fail possibilities of internal processes, SSI can be utilised to allocate the power of each process in achieving or failing the POBC performance target, prior to identifying the system bottleneck (SB) in terms of process stage. Therefore, a novel process-level debottlenecking approach with SSI incorporation for a sustainable FEW system was proposed. The SB of greatest impact on overall POBC performance within the fuzzy optimal flowsheet was identified based on SSI allocation and weightage assignment considering decision-maker's interest in multiple goals. Subsequently, the debottlenecked POBC flowsheet with improvement in SB process parameter was generated subjected to profit maximisation and environmental constraints. In this study, the nut/kernel separation and biomass cogeneration system was identified as the SB of fuzzy optimal POBC. The debottlenecked results show 0.8% and 51% of profit and net energy improvement upon 30% increment of boiler efficiency. The debottlenecked flowsheet is validated in the benefit-to-drawback ratio analysis with a feasible score of 3.9. The POME-eliminated POBC generated via the integrated multi-objective optimisation and debottlenecking framework is applicable for POM retrofit to secure 13%, 97% and 47% of improvements in terms of economic potential, greenhouse gas emissions and water footprint compared to the status quo biogas utilisation scenario. The results of the study could aid palm oil holders in real-life planning of budget distribution and maintenance schedule for process stages in the retrofitted POM.

Abstract The challenge in clean palm oil production falls on the management of palm oil mill effluent which is a notable source of greenhouse gas emissions and water pollution. To address these critics against edible palm oil, an integrated palm oil-based complex (POBC) considering effluent elimination and refinery integration is suitable for environmental-food-energy-water (EFEW) nexus development. Optimal retrofit of palm oil mill into EFEW nexus-integrated POBC requires multi-objective considerations to balance the trade-offs between profitability, energy contribution, greenhouse gas, water and land footprints via fuzzy optimisation. With limited practical knowledge, potential flowsheet modifications should be investigated for flexible POBC design. In a cooperative game context, interconnecting processes act as multiple players cooperating to achieve the goal of the game, i.e., POBC performance, where each player has a distinctive impact on the outcome. In this work, such process performance was suggested to be distributed using cooperative game model, to target the EFEW-based anchor process, i.e., the process stage of greatest contribution in the weighted EFEW nexus, for desired flowsheet advancement. Considering these aspects, an integrated fuzzy and cooperative game optimisation framework was developed to identify the anchor process of an EFEW nexus-integrated POBC. EFEW objective-based process performance allocation in the fuzzy optimal POBC was weighted by the decision-maker to allocate the anchor process using developed models and Excel tools. Nut/kernel separation and cogeneration stage is the EFEW-based anchor process in the fuzzy optimal POBC with EFEW nexus score of 41% in this work. A comparative analysis between the proposed method with other approach was done. The favourability of EFEW contributions by POBC in terms of benefit-drawback ratio increased with the percentage of boiler efficiency increment within the targeted anchor process. Targeting anchor process aids planning for process maintenance and advancement to avoid resource wastage on sub-critical processes.

Abstract To reduce greenhouse gas (GHG) impact while sustaining palm oil mill (POM) profitability, Malaysia has recognised POME-derived biogas as a renewable energy. Biogas utilisation for on-site fuel replacement and grid electricity contribution is encouraged by government schemes such as Feed-in-tariff (FiT). Nevertheless, adoption rate of biogas facility is still low among Malaysian POMs. An integrated palm-oil based complex (POBC) was proposed for GHG mitigation by integrating POM and refinery processes while addressing sustainability concerns. This study presented a multi-objective optimisation model-based approach to aid POBC planning at maximised economic potential and net energy, while minimising its GHG emission, water footprint (WFP) and land footprint (LFP) for environment protection. Trade-offs between biogas recovery and POME elimination strategies were considered. The developed fuzzy model was applied to case study and analysed under different multi-objective scenarios. In comparison with baseline study, the economic potential of sustainable POBC increase by 6.7% at USD 39.31 × 106 with 88%, 74% and 91% improvements in GHG footprint, WFP and LFP by compromising 76% net energy. Effect of FiT revenue towards POBC synthesis was investigated. Pareto front was generated to verify the fuzzy results and visualise the relationship between objective functions. The optimisation model and optimal results shall provide input to Malaysian POMs on the sustainability benefits of POBC.