Urban Material Flow Analysis of Plastics

Abstract

Global plastic production increased from 200 million metric tons in 2002, to 359 million metric tons in 2019. It is estimated that plastics in the marine environment weigh more than 150 million metric tons and by 2050 could even outweigh the mass of fish in the ocean. Over half of the world population (55%) nowadays lives in urban areas and consumes large amounts of materials and turns them into waste, including plastics. Thus, it necessary to understand the plastic mass balance of a city. The goal of this thesis is to assess plastic flows and stocks for an urban area, using the well-established method of Material Flow Analysis (MFA). By using MFA, material flows through society can be assessed in a systematic way. This research answers the following research question: “How can the plastic mass balance of an urban area be modelled using Material Flow Analysis?” This is done by developing a generic framework, which includes eight consumption sectors, three distinguishable littering processes and two subsystems (surface water system and soil). A bottom-up approach is applied and the municipality of Leiden in the Netherlands is used as a case study. The surface water system is analysed as a subsystem, which stores plastics but also transports them through physical forces, like water flow outside of the system. Crowd-sourced data is analysed and its usage for urban MFA assessed. The analysis shows that the biggest plastic flows are packaging flows (4 146 t), plastics in building waste (1 342 t) and plastics in End-of-life transportation systems (570 t). The highest plastic stocks are in buildings (86 080 t), transportation (14 020 t) and electronics devices (10 326 t). It is concluded that the crowd-sourced data set Litterati includes for 2019 for the case of Leiden to little data points in order to represent the plastic litter quantity in the system accurately. This thesis adds to MFA theory by investigating the surface water system and its connection to the environment through physical forces like water flow and wind.