Life Cycle Sustainability Assessment of Single Stream and Multi-Stream Waste Recycling Systems

An increasing trend of moving towards single-stream waste management systems is occurring in many municipalities. This is because of the ability to process greater quantities of materials, minimize material management costs, and maximize recycling convenience and participation. Research on evaluating comprehensive sustainability (economic, environmental, and social) of the two streams is very limited. This study looks to gain an in-depth understanding of two waste management systems and assist in the decision-making processes of municipalities. To achieve this, the study provides a framework for evaluating economic, environmental, and social impacts as well as a sustainability assessment of single- vs. multi-stream waste management systems within the scope of a typical North American college town. A life cycle assessment framework was employed. The scope of the assessment includes production of materials, collection, sorting, and processes included in a material recovery facility (MRF). The functional unit is 1 ton of municipal solid waste. The case study was conducted on a North American college city during its transition from multi-stream recycling to single-stream recycling. The sustainability assessment result of the case study reveals that the single-stream recycling collection cost is slightly lower (USD 86.96/ton) than the multi-stream recycling collection cost (USD 89/ton). Additionally, the GHG emissions for the single-stream recycling system (10.56 kg CO2eq/ton) are slightly higher than for the multi-stream recycling system (9.67 kg CO2eq/ton). This is due to the complexity of the processes involved in the MRF. Nevertheless, recycling rate is the determining factor for life cycle GHG emissions and costs. Municipal solid waste policymakers could benefit from this study by using the framework and study results for tactical and strategic decision-making.