Life cycle assessment of plastic grocery bags and their alternatives in cities with con fi ned waste management structure: A Singapore case study

Plastic grocery bags are one of the most ubiquitous single-use packaging products. Recently, 'ecofriendly' options of plastic grocery bags have gained traction such as kraft paper, cotton, biodegradable, and reusable polypropylene non-woven bags. However, the impact of using various grocery bags in cities with dense population, well-developed infrastructure and thermal treatment as an end-of-life waste management option has been insufficiently documented. In this study, commonly found single-use (HDPE, biodegradable plastic, kraft paper) bags and reusable (cotton, polypropylene non-woven) bags were considered for the life cycle assessment (LCA). The usage characteristics (reusability, dimensions, carrying capacity) of bags, the production process (raw materials extraction, production processes), and emissions were determined as the significant factors contributing to the negative environmental im-pacts. In a model city with confined waste management, the assessment determined that the reusable polypropylene non-woven bag (PNB) caused the least overall negative environmental impacts when there are 50 instances of reuse, followed by single use HDPE plastic bag (HPB). The global warming potential (excluding biogenic carbon) was 14, 81, 17 and 16 times higher for HDPE plastic, kraft paper, cotton woven and biodegradable polymer bags, respectively, when compared to PNB. Moreover, kraft paper or cotton woven bags demonstrated the highest negative impacts for the impact categories including abiotic fossil depletion, freshwater-, marineand terrestrial-ecotoxicities, human toxicity, acidification and eutrophication potentials. Further, sensitivity analysis indicated that the inflexion point for the PNB was minimum 4 reuses to avoid emission equivalent to the HPB. Singapore was adopted as the model city with confined waste management structure that imports most of the grocery bags, either as finished goods or as raw materials. Through comprehensive insights based on the new outlook of the integrated LCA model (cradle-to-grave) that included full-scale transportation component, the usage of the real case data from a city to develop the life cycle inventory, and consideration of the existing grocery bags options, the environmental assessment along with critical evaluation was conducted. (C) 2020 Elsevier Ltd. All rights reserved.