The influence of recycling schemes on the composition and generation of municipal solid waste

To ensure the transparency and comparability of life cycle assessment (LCA) studies of waste management systems, a comprehensive waste data is necessary. We sampled and characterised municipal household waste in Denmark to investigate the impact of recycling schemes on the composition and generation of residual household waste (RHW), provide detailed waste data to waste management authorities as well as LCA practitioners. In total, 20 ton of waste, taken from 1,800 households in seven Danish municipalities in 2011 and 2017, was manually sorted. These municipalities had in common the systems for source separation of paper, cardboard, metal and glass, whereas the recycling of food and plastic varied among them. The waste sorting campaigns provided detailed composition of individual recycling scheme including (1) food, (2) plastic, (3) paper, (4) cardboard, (5) metal, and (6) glass as well as (7) RHW. For each of the six recycling schemes, waste was sorted into two different waste catalogues containing 48 and 50 fractions. Such a detailed waste composition enables waste management authorities to design comprehensive guidelines for waste sorting, while providing LCA practitioners with data that can significantly improve the validity and certainty of their results and recommendations. The results show that the highest misplacement rate was found in waste bins dedicated to food, plastic and RHW. The statistical analyses show that source separation of food and plastic waste reduces significantly (11%) the total amount of household waste, suggesting that, in addition to the environmental benefit of diverting food and plastic waste from landfill and incineration, source segregation may as well contribute to waste prevention. Moreover, the source-sorting of food waste, independently of whether plastics were sorted or not, significantly influences the composition of the RHW.