Multi Objective Optimisation and Sustainable Modelling of Waste Management Systems in Trinidad and Tobago

Trinidad and Tobago exhibit one of the highest waste generation per capita in the world and also is one of the most heavily industrialized countries in the Caribbean and hence a large GHG emitter. The primary method of waste treatment is landfilling which results in heavy environmental burdens and the country must prioritise more sustainable methods in order to achieve its 15% GHG reduction pledge by 2030 according to the Paris Agreement. This study presents a multi-objective mixed integer linear programming framework to optimise waste management plans involving disposal methods of incineration, recycling of plastics and landfilling which is then compared against the optimised current waste management in the country. Results offer quantitative insights into economic and environmental performance, balancing trade-offs between minimising both total cost and greenhouse gas (GHG) emissions levelized to 1 tonne of municipal solid waste (MSW). The findings indicated that the cost of MSW sorting was the most economic intensive operation accounting for roughly 50% of the total cost. Furthermore, incineration and landfilling were the two factors for the trade-off between the economic vs. environmental whereby incineration optimised the environmental while landfilling optimised the economic. Trade-off Pareto optimal solutions were analysed to identify reasonable trade-off configurations between the two objectives for all 3 cases examined. The best case offered a levelized cost of $127.58 USD/tonneMSW and a 70% reduction in GHG emissions overall. Th increased levelized cost was mainly due to high cost incurred by MSW sorting. Moreover, findings showed that an optimal MSW composition comprising of 27-19% organic fraction coupled with roughly 20-21% exists for improved economic and environmental performance. Thus, from the results of this study, the addition of incineration as a new waste disposal method which lessens the quantity of waste landfilled should be carefully considered for a more sustainable waste management process.特立尼达和多巴哥（Trinidad and Tobago）是全球人均垃圾产生量最高的国家之一，同时也是加勒比地区工业化程度最高的国家之一，因此属于温室气体（Greenhouse Gas, GHG）排放大国。该国当前的垃圾处理主流方式为卫生填埋，由此带来了沉重的环境负荷。根据《巴黎协定》，特立尼达和多巴哥必须优先推广更可持续的处理技术与模式，方能实现其到2030年温室气体减排15%的承诺。本研究构建了多目标混合整数线性规划（Multi-objective Mixed Integer Linear Programming）框架，对涵盖焚烧、塑料回收与卫生填埋的垃圾处置方案进行优化，并将该优化方案与该国当前已优化的垃圾管理模式开展对比分析。研究结果从经济与环境绩效维度提供了量化视角，平衡了两项核心优化目标的权衡关系：一是最小化总成本，二是将温室气体排放平准至每吨城市固体废物（Municipal Solid Waste, MSW）的排放水平。研究结果显示，城市固体废物分拣是经济投入占比最高的作业环节，其成本约占总成本的50%。此外，焚烧与卫生填埋是构成经济-环境权衡关系的两大核心因素：焚烧更利于优化环境绩效，而填埋则更能优化经济绩效。本研究对权衡后的帕累托最优解（Pareto Optimal Solution）进行了分析，为所考察的全部3个案例确定了两项优化目标间的合理权衡配置方案。最优案例的平准化成本为127.58美元/吨城市固体废物，整体温室气体减排幅度可达70%。此次升高的平准化成本主要源于城市固体废物分拣环节的高额投入。此外，研究结果表明，当城市固体废物的组分构成为27%~19%的有机组分搭配约20%~21%的其他组分时，可实现更优异的经济与环境绩效。综上，本研究结果表明，为构建更可持续的垃圾管理体系，应审慎考虑新增焚烧作为新型垃圾处置手段，以减少填埋垃圾的总量。