Greenhouse gas impact of dual stream and single stream collection and separation of recyclables

Over the past decade communities and municipalities have been increasingly switching their recycling systems from dual stream (DS) to single stream (SS). Accordingly, material recovery facilities (MRF) have been constructed and retrofitted in order to accommodate fully commingled input streams. This transition has been driven by a variety of factors, including a general understanding that SS tends to result in increased waste diversion rates for participating communities. This paper examines the greenhouse gas emissions, or “carbon footprint,” of recycling systems before and after the transition from DS to SS. This investigation aims to assess the environmental impact of trends in the recycling industry from a holistic perspective. In our analysis we consider several communities around the U.S. on the bases of tonnage and type of material recycled, fuel and electricity consumed in collection and separation, and avoided virgin materials consumption. By examining data from a small range of communities and MRF, we arrive at three main conclusions. First, a change from DS to SS results in approximately a 50% increase in production of recyclable commodities. Second, the net result of the DS–SS transition is approximately 710kgCO2-equiv. avoided per metric ton of collection. Third, the emissions associated with collection and MRF operation are small in comparison to avoided emissions from avoided consumption of virgin materials.