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.