The impact of allocation methods on carbon benefits - a case study of construction waste recycling

Recycling is crucial to address environmental issues caused by increasing wastes. Recycled materials can replace primary materials and offset greenhouse gas emissions, resulting in a carbon benefit. The environmental burdens and benefits of recycling cause broad discussions about the allocation of the burdens and benefits in life cycle assessment. The recycling situations and recyclability of different materials may be different, therefore, different allocation methods shall be selected. However, a common procedure for selecting the allocation method is missing, which led to difficulty in fairly and reasonably assessing the recycling benefits of wastes from the end-of-life product. In this work, we investigated the impact of carbon emissions in the end-of-life stage with a case of construction wastes. Five allocation methods were selected. A sensitivity analysis was conducted to identify factors influencing carbon benefit outcomes. Based on the case studies, we summarized the strengths and limitations of different allocation methods. Finally, a policy-oriented framework for selecting an allocation method was proposed. Our work serves as a basis for allocation method selection and also as a reference for quantifying the carbon benefit of recycled wastes.