A comprehensive waste collection cost model applied to post-consumer plastic packaging waste

Post-consumer plastic packaging waste (PPW) can be collected for recycling via source separation or post-separation. In source separation, households separate plastics from other waste before collection, whereas in post-separation waste is separated at a treatment centre after collection. There are also two collection schemes, either curb side or via drop-off locations. These different schemes have impact on total costs of collection at the municipal level. It can also influence the facility choices and network design. Therefore, a method which can compare costs of various collection schemes is needed.A comprehensive cost model was developed to compare costs of municipal collection schemes of PPW. The ‘municipal waste collection cost model’ is based on variables including fixed and variable costs per vehicle, personnel cost, container or bag costs as well as on emission costs (using imaginary carbon taxes). The model can be used for decision support when strategic changes to the collection scheme of municipalities are considered. The model takes into account the characteristics of municipalities, including urbanization degree and taxation schemes for household waste management.The model was applied to the Dutch case of post-consumer plastic packaging waste. Results showed that that in general post-separation collection has the lowest costs and curb side collection in urban municipalities without residual waste collection taxing schemes the highest. These results were supported by the conducted sensitivity analysis, which showed that higher source separation responses are negatively related to curb side collection costs. Greenhouse gas emission costs are a significant part of the total costs when collecting post-consumer plastic packaging waste due to the low density to weight ratio of the materials collect. These costs can amount to 15% of the total collection costs.     

Efficiency evaluation for regional urban water use and wastewater decontamination systems in China: A DEA approach

Rapid economic growth and urbanization in China have resulted in great water consumption in recent years. China has been facing increasingly severe water shortage crisis, especially in urban areas. This paper focuses on performance analysis for regional urban water use and wastewater decontamination systems in China. To this end, a DEA-based approach is developed. In the proposed approach, the efficiency of the system is decomposed into water use efficiency and wastewater decontamination efficiency. In the wastewater decontamination sub-system, the purified wastewater (reusable water) is treated as a desirable output; while in the water use sub-system, it is incorporated as a fixed input, which cannot be decreased in the process of efficiency optimization. The efficiency of the system is defined as the average of the two sub-systems’ efficiencies. The proposed approach can find inefficiencies caused by the internal factors between sub-systems, which cannot be identified using the traditional DEA approaches. We finally apply the proposed approach to analyze the efficiencies of regional urban water use and wastewater decontamination systems in China. Based on the application results, some findings and implications for efficiency improvement of urban water management in China are achieved.