Editing IPCC:AR6/WGIII/Chapter-8 (section)

==== 8.4.5.2 Avoiding, Minimising, and Recycling Waste ====

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The waste sector is a significant source of GHG emissions, particularly CH 4 ( [[#Gonzalez-Valencia--2016|Gonzalez-Valencia et al. 2016]] ; [[#Nisbet--2019|Nisbet et al. 2019]] ). Currently, the sector remains the largest contributor to urban emissions after the energy sector, even in low-carbon cities ( [[#Lu--2019|Lu and Li 2019]] ). Since waste management systems are usually under the control of municipal authorities, they are a prime target for city-level mitigation efforts with co-benefits ( [[#EC--2015|EC 2015]] , 2020; [[#Gharfalkar--2015|Gharfalkar et al. 2015]] ; [[#Herrero--2018|Herrero and Vilella 2018]] ; [[#Zaman--2019|Zaman and Ahsan 2019]] ). Despite general agreement on mitigation impacts, quantification remains challenging due to differing assumptions for system boundaries and challenges related to measuring avoided waste ( [[#Zaman--2013|Zaman and Lehmann 2013]] ; [[#Bernstad%20Saraiva%20Schott--2015|Bernstad Saraiva Schott and Cánovas 2015]] ; [[#Matsuda--2018|Matsuda et al. 2018]] ).

The implementation of the waste hierarchy from waste prevention onward, as well as the effectiveness of waste separation at source, involves socio-behavioural options in the context of urban infrastructure ( [[#Sun--2018a|Sun et al. 2018a]] ; [[#Hunter--2019|Hunter et al. 2019]] ). Managing and treating waste as close to the point of generation as possible, including distributed waste treatment facilities, can minimise transport-related emissions, congestion, and air pollution. Home composting and compact urban form can also reduce waste transport emissions ( [[#Oliveira--2017|Oliveira et al. 2017]] ). Decentralised waste management can reinforce source-separation behaviour since the resulting benefits can be more visible ( [[#Eisted--2009|Eisted et al. 2009]] ; [[#Hoornweg--2012|Hoornweg and Bhada-Tata 2012]] ; [[#Linzner--2013|Linzner and Lange 2013]] ). Public acceptance for waste management is greatest when system costs for citizens are reduced, there is greater awareness of primary waste separation at source, and there are positive behavioural spill-overs across environmental policies ( [[#Milutinović--2016|Milutinović et al. 2016]] ; [[#Boyer--2017|Boyer and Ramaswami 2017]] ; [[#Díaz-Villavicencio--2017|Díaz-Villavicencio et al. 2017]] ; [[#Slorach--2020|Slorach et al. 2020]] ). In addition to the choice of technology, the costs of waste management options depend on the awareness of system users that can represent time-dependent costs ( [[#Khan--2016|Khan et al. 2016]] ; [[#Chifari--2017|Chifari et al. 2017]] ; [[#Ranieri--2018|Ranieri et al. 2018]] ; [[#Tomić--2020|Tomić and Schneider 2020]] ). Waste management systems and the inclusion of materials from multiple urban sectors for alternative by-products can increase scalability ( [[#Eriksson--2015|Eriksson et al. 2015]] ; [[#Boyer--2017|Boyer and Ramaswami 2017]] ; [[#D’Adamo--2021|D’Adamo et al. 2021]] ). As a broader concept, circular economy approaches can contribute to managing waste (Box 12.8) with varying emissions impacts ( [[IPCC:Wg3:Chapter:Chapter-5#5.3.4|Section 5.3.4]] ).

The generation and composition of waste varies considerably from region to region and city to city. So do the levels of institutional management, infrastructure, and (informal) work in waste disposal activities. Depending on context, policy priorities are directed towards reducing waste generation and transforming waste to energy or other products in a circular economy ( [[#Diaz--2017|Diaz 2017]] ; [[#Ezeudu--2019|Ezeudu and Ezeudu 2019]] ; [[#Joshi--2019|Joshi et al. 2019]] ; [[#Calderón%20Márquez--2020|Calderón Márquez and Rutkowski 2020]] ; [[#Fatimah--2020|Fatimah et al. 2020]] ). Similarly, waste generation, waste collection coverage, recycling, and composting rates, as well as the means of waste disposal and treatment, differ widely, including the logistics of urban waste management systems. Multiple factors influence waste generation, and regions with similar urbanisation rates can generate different levels of waste per capita ( [[#Kaza--2018|Kaza et al. 2018]] ).

Under conventional practices, municipal solid waste is projected to increase by about 1.4 Gt between 2016 and 2050, reaching 3.4 Gt in 2050 ( [[#Kaza--2018|Kaza et al. 2018]] ). Integrated policymaking can increase the energy, material, and emissions benefits in the waste management sector ( [[#Hjalmarsson--2015|Hjalmarsson 2015]] ; [[#Fang--2017|Fang et al. 2017]] ; [[#Jiang--2017|Jiang et al. 2017]] ). Organisational structure and programme administration poses demands for institutional capacity, governance, and cross-sectoral coordination for obtaining the maximum benefit ( [[#Hjalmarsson--2015|Hjalmarsson 2015]] ; [[#Kalmykova--2016|Kalmykova et al. 2016]] ; [[#Conke--2018|Conke 2018]] ; [[#Marino--2018|Marino et al. 2018]] ; [[#Yang--2018|Yang et al. 2018]] ).

The informal sector plays a critical role in waste management, particularly but not exclusively in developing countries ( [[#Linzner--2013|Linzner and Lange 2013]] ; [[#Dias--2016|Dias 2016]] ). Sharing of costs and benefits, and transforming informality of waste recycling activities into programmes, can support distributional effects ( [[#Conke--2018|Conke 2018]] ; [[#Grové--2018|Grové et al. 2018]] ). Balancing centralised and decentralised waste management options along low-carbon objectives can address potential challenges in transforming informality ( [[#de%20Bercegol--2019|de Bercegol and Gowda 2019]] ). Overall, the positive impacts of waste management on employment and economic growth can be increased when informality is transformed to stimulate employment opportunities for value-added products with an estimated 45 million jobs in the waste management sector by 2030 ( [[#Alzate-Arias--2018|Alzate-Arias et al. 2018]] ; [[#Coalition%20for%20Urban%20Transitions--2020|Coalition for Urban Transitions 2020]] ; [[#Soukiazis--2020|Soukiazis and Proença 2020]] ).

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