Editing IPCC:AR6/WGIII/Chapter-13 (section)

=== Box 13.10 | Policies to Limit Emissions of Non-CO2 Gases ===

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Non-CO 2 gases weighted by their 100-year GWPs represent approximately 25% of global GHG emissions, of which methane (CH 4 ) accounts for 18%, nitrous oxide (N 2 O) 4%, and fluorinated gases (HFCs, PFCs, SF 6 and NF 3 ) 2% (Minx et al. 2021). Only a small share of these emissions are subject to mitigation policies.

'''Methane (CH''' 4 ''').''' Anthropogenic sources include agriculture, mainly livestock and rice paddies, fossil fuel extraction and processing, fuel combustion, some industrial processes, landfills, and wastewater treatment ( [[#EPA--2019|EPA 2019]] ). Atmospheric measurements indicate that methane emissions from fossil fuel production are larger than shown in emissions inventories ( [[#Schwietzke--2016|Schwietzke et al. 2016]] ). Only a small fraction of global CH 4 emissions is regulated. Mitigation policies focus on landfills, coal mines, and oil and gas operations.

Regulations and incentives to capture and utilise methane from coal seams came into effect in China in 2010 ( [[#Tan--2018|Tan 2018]] ; [[#Tao--2019|Tao et al. 2019]] ). Inventory data suggest that emissions peaked and began a slow decline after 2010 ( [[#Gao--2020|Gao et al. 2020]] ) though satellite data indicate that China’s methane emissions, largely attributable to coal mining, continued to rise in line with pre-2010 trends ( [[#Miller--2019|Miller et al. 2019]] ). Methane emissions from sources including agriculture, waste and industry are included in some offset credit schemes, including the CDM and at national level in Australia’s Emissions Reductions Fund ( [[#Australian%20Climate%20Change%20Authority--2017|Australian Climate Change Authority 2017]] ) and the Chinese Certified Emission Reduction (CCER) scheme ( [[#Lo--2017|Lo and Cong 2017]] ).

'''Nitrous oxide (N''' 2 '''O).''' N 2 O emissions are produced by agricultural soil management, livestock waste management, fossil fuel combustion, and adipic acid and nitric acid production ( [[#EPA--2019|EPA 2019]] ). Most N 2 O emissions are not regulated and global emissions have been increasing. N 2 O emissions by adipic and nitric acid plants in the EU are covered by the ETS ( [[#Winiwarter--2018|Winiwarter et al. 2018]] ). N 2 O emissions are included in some offset schemes. China, the United States, Singapore, Egypt, and Russia produce 86% of industrial N 2 O emissions offering the potential for targeted mitigation action ( [[#EPA--2019|EPA 2019]] ).

'''Hydrofluorocarbons (HFCs).''' Most HFCs are used as substitutes for ozone depleting substances. The Kigali Amendment (KA) to the Montreal Protocol will reduce HFC use by 85% by 2047 ( [[#UN%20Environment--2018|UN Environment 2018]] ). To help meet their KA commitments developed country parties have been implementing regulations to limit imports, production and exports of HFCs and to limit specific uses of HFCs.

The EU, for example, issues tradable quota for imports, production and exports of HFCs. Prices of HFCs have increased as expected ( [[#Kleinschmidt--2020|Kleinschmidt 2020]] ) which has led to smuggling of HFCs into the EU (European Commission 2019b). HFC use has been slightly (1–6%) below the limit each year from 2015 through 2018 ( [[#EEA--2019|EEA 2019]] ). China and India released national cooling action plans in 2019, laying out detailed, cross-sectoral plans to provide sustainable, climate friendly, safe and affordable cooling ( [[#Dean--2020|Dean et al. 2020]] ).

'''Perfluorocarbons (PFCs), sulphur hexafluoride (SF''' 6 ''') and nitrogen trifluoride (NF''' 3 ''').''' With the exception of SF 6 , these gases are emitted by industrial activities located in the European Economic Area (EEA) and a limited number (fewer than 30) of other countries. Regulations in Europe, Japan and the USA focus on leak reduction as well as collection and reuse of SF 6 from electrical equipment. Other uses of SF 6 are banned in Europe ( [[#European%20Union--2014|European Union 2014]] ).

PFCs are generated during the aluminium smelting process if the alumina level in the electrolytic bath falls below critical levels ( [[#EPA--2019|EPA 2019]] ). In Europe these emissions are covered by the EU ETS. The industry is eliminating the emissions through improved process control and a shift to different production processes.

The semiconductor industry uses HFCs, PFCs, SF 6 and NF 3 for etching and deposition chamber cleaning ( [[#EPA--2019|EPA 2019]] ) and has a voluntary target of reducing GHG emissions 30% from 2010 by 2020 ( [[#World%20Semiconductor%20Council--2017|World Semiconductor Council 2017]] ). Europe regulates production, import, export, destruction and feedstock use of PFCs and SF 6 , but not NF 3 ( [[#EEA--2019|EEA 2019]] ). In addition, fluorinated gases are taxed in Denmark, Norway, Slovenia and Spain.

In some jurisdictions, the analysis of regulatory instruments is subject to an assessment on the basis of a shadow cost of carbon, which can influence the choice and design of regulations that affect GHG emissions (Box 13.11).

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