The climate and energy nexus have drawn global attention towards sustainable solutions for synthetic processes, such as waste management. Innovative policies can amend waste management systems to be more sustainable, as in Hong Kong, where besides the conventional landfilling, alternatives like incineration and biological treatment methods are being considered to develop an integrated system. However, the outcomes appear uncertain and need to be analysed for best possible integration. This study proposes a customized methodology for impact assessment of these waste treatment technologies and evaluates five integrated scenarios in terms of net greenhouse gas emissions (GHEs) and energy use by applying classified modelling approaches. The baseline results revealed that compared to the landfilling alone, integration of landfilling with combined anaerobic digestion and composting (ADC) reduced up to 56% of net GHEs. Incineration with ADC saved up to 87% GHEs and ranked as the best-case scenario in both impact categories. Considering carbon sequestration as a credit suggested that landfill-linked scenarios were suitable for GHEs saving, while landfilling alone remained the worst case. The uncertainty propagation and sensitivity analysis revealed that some key parameters can alter the ranking order of scenarios, when variated by the reported uncertainty. The study provides useful modelling insights into the critical nature of these technologies and can be considered as a decision-making tool locally, as well as a generic calculation template.