Citation: Aldhafeeri, Z.M.; Alhazmi, H. Sustainability Assessment of Municipal Solid Waste in Riyadh, Saudi Arabia, in the Framework of Circular Economy Transition. Sustainability 2022, 14, 5093. https:// doi.org/10.3390/su14095093 Academic Editor: Antonella Petrillo Received: 4 March 2022 Accepted: 21 April 2022 Published: 23 April 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). sustainability Article Sustainability Assessment of Municipal Solid Waste in Riyadh, Saudi Arabia, in the Framework of Circular Economy Transition Zaid M. Aldhafeeri and Hatem Alhazmi * National Center for Environmental Technology, King Abdulaziz City for Science and Technology, Riyadh 11442, Saudi Arabia; zaldhafeeri@kacst.edu.sa * Correspondence: halhazmi@kacst.edu.sa Abstract: Life cycle assessment (LCA) tools can be used for the environmental assessment of munici- pal solid waste management (MSWM) systems. The present study aims to evaluate the impact of an MSWM system in Riyadh, Saudi Arabia, under three different scenarios based on the Strategy for 2045 of Riyadh. The current scenario (S0) considers that municipal solid waste (MSW) is landfilled, scenario one (S1) considers waste to energy (WtE) as the main treatment while dry recyclables and organic waste collection schemes are introduced, and scenario two (S2) considers dry recyclables and organic waste collection schemes at the maximum level while the residual portion is treated as WtE. The system boundaries include MSW treatment and disposal by recycling, incineration, composting, and landfilling methods. The scenarios were compared using SimaPro 9.1.1.1 software, and the ReCiPe 2016 Midpoint (H) V1.04/World (2010) H method was used to assess global warming, ozone formation (human health), fine particulate matter formation, terrestrial acidification, freshwater eutrophication, mineral resource scarcity, and fossil resource scarcity. S0 was found to be the scenario with the least impact if considering just the waste treatment. However, S1 and S2 allow material and energy recovery that avoids the impact of obtaining primary resources. S1 and S2 reduced greenhouse gases (GHG) emissions by 55% and 58%, respectively, compared to S0. According to the SV2030, 2% of the electricity generated by the Kingdom would have to come from WtE, but based on the calculations, the maximum electricity from waste would be obtained with S1 fully implemented and would contribute a maximum of 1.51% to Saudi Arabia’s electricity demand. This study con- tributes by providing useful insights that could help decision-makers to understand the potential environmental impacts by assessing each step considered by the Strategy for 2045 for Riyadh along with the consequences on material and energy supply by using the material and energy potential of MSW. Keywords: municipal solid waste; life cycle assessment; alternative scenarios; landfill; incinera- tion; composting 1. Introduction Population growth, urbanization, limited land resources, and insufficient planning policies are restricting waste management efforts in cities [1]. As a result, serious challenges and environmental concerns are mounting due to inefficient systems. This is particularly true among developing countries, where landfilling remains the chosen route due to economic factors or a lack of technical expertise in other options, such as biological and/or thermal treatment [2]. Life cycle assessment (LCA) is a thorough process that evaluates all environmental impacts. As a result, all effects on the environment across the whole life cycle of a product or process are quantified [3]. Although LCA is hardly a scientific tool, it uses a scien- tific approach for understanding the environmental impacts of products and systems [4]. There is a steady rise in the use of LCA for solid waste management systems, notably in decision-making processes and strategy planning. Utilized since 1995 for sustainable MSW Sustainability 2022, 14, 5093. https://doi.org/10.3390/su14095093 https://www.mdpi.com/journal/sustainability