Editing IPCC:AR6/WGIII/Chapter-11 (section)

==== 11.4.1.4 Other Industry Sectors ====

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The other big sources of direct global industrial combustion and process CO 2 emissions are light manufacturing and industry (9.7% in 2016), non-ferrous metals like aluminium (3.1%), pulp and paper (1.1%), and food and tobacco (1.9%) ( [[#Bataille--2020a|Bataille 2020a]] ; [[#Crippa--2021|Crippa et al. 2021]] ; [[#Lamb--2021|Lamb et al. 2021]] ).

Light manufacturing and industry represent a very diverse sector in terms of energy service needs (e.g., motive power, ventilation, drying, heating, compressed air, etc.) and it comprises both small and large plants in different geographical contexts. Most of the direct fossil fuel use is for heating and drying, and it can be replaced with low-GHG electricity through direct resistance, high-temperature heat pumps and mechanical vapour recompression, induction, infrared, or other electrothermal processes ( [[#Lechtenböhmer--2016|Lechtenböhmer et al. 2016]] ; [[#Bamigbetan--2017|Bamigbetan et al. 2017]] ). [[#Madeddu--2020|Madeddu et al. (2020)]] argue up to 78% of Europe’s industrial energy requirements are electrifiable through existing commercial technologies and 99% with the addition of new technologies currently under development. Direct solar heating is possible for low temperature needs (&lt;100°C) and concentrating solar for higher temperatures. Commercially available heat pumps can deliver 100°C–150°C but at least up to 280°C is feasible ( [[#Zühlsdorf--2019|Zühlsdorf et al. 2019]] ). Plasma torches using electricity can be used where high temperatures (&gt;1000°C) are required, but hydrogen, biogenic or synthetic combustible hydrocarbons (methane, methanol, ethanol, LPG, etc.) can also be used ( [[#Bataille--2018a|Bataille et al. 2018a]] ).

There is also a large potential for energy savings through cascading in industrial clusters similar to the one at Kalundborg, Denmark. Waste heat can be passed at lower and lower temperatures from facility to facility or circulated as low-grade steam or hot water, and boosted as necessary using heat pumps and direct heating. Such geographic clusters would also enable lower-cost infrastructure for hydrogen production and storage as well as CO 2 gathering, transport and disposal ( [[#IEA--2019f|IEA 2019f]] ).

Demand for aluminium comes from a variety of end uses where a reasonable cost, light-weight metal is desirable. It has historically been used in aircraft, window frames, strollers, and beverage containers. As fuel economy has become more desirable and design improvements have allowed crush bodies made of aluminium instead of steel, aluminium has become progressively more attractive for cars. Primary aluminium demand is total demand (100 Mt yr –1 in 2020) net of manufacturing waste reuse (14% of virgin and recycled input) and end-of-life recycling (about 20% of what reaches market). Primary aluminium consumption rose from under 20 Mt yr –1 in 1995 to over 66 Mt primary ingot production in 2020 (International Aluminium Institute change to 2021c). The [[#International%20Aluminium%20Institute--2021a|International Aluminium Institute (2021a)]] expects total aluminium consumption to reach 150–290 Mt yr –1 by 2050 with primary aluminium contributing 69–170 Mt and secondary recycled 91–120 Mt (as in-use stock triples or quadruples). The OECD forecasts increases in demand by 2060 for primary aluminium to 139 Mt yr –1 and for secondary aluminium to 71 Mt yr –1 ( [[#OECD--2019a|OECD 2019a]] ). Primary (as opposed to recycled) aluminium is generally made in a two-stage process, often geographically separated. In the first stage aluminium oxide is extracted from bauxite ore (often with other trace elements) using the Bayer hydrometallurgical process, which requires up to 200°C heat when sodium hydroxide is used to leach the aluminium oxide, and up to 1000°C for kilning. This is followed by electrolytic separation of the oxygen from the elemental aluminium using the Hall-Héroult process, by far the most energy-intense part of making aluminium. This process has large potential emissions from the electricity used (12.5 MWh per tonne aluminium BAT, 14–15 MWh per tonne average). From bauxite mine to aluminium ingot, reported total global average emissions are between 12 and 17.6 tCO 2 -eq per tonne of aluminium, depending on estimates and assumptions made [[#footnote-005|22]] ( [[#Saevarsdottir--2020|Saevarsdottir et al. 2020]] ). About 10% of this, 1.5 tonnes of direct CO 2 per tonne of aluminium are currently emitted as the graphite electrodes are depleted and combine with oxygen, and if less than optimal conditions are maintained, perfluorocarbons can be emitted with widely varying GHG intensity, up to the equivalent of 2 tCO 2 -eq per tonne of aluminium. PFC emissions, however, have been greatly reduced globally and almost eliminated in well-run facilities. Aluminium, if it is not contaminated, is highly recyclable and requires 1/20 of the energy required to produce virgin aluminium; increasing aluminium recycling rates from the 20–25% global average is a key emissions reduction strategy (Haraldsson and Johansson 2018).

The use of low- and zero-GHG electricity (e.g., historically from hydropower) can reduce the indirect emissions associated with making aluminium. A public-private partnership with financial support from the province of Québec and the Canadian federal government has recently announced a fundamental modification to the Hall-Héroult process by which the graphite electrode process emissions can be eliminated by substitution of inert electrodes. This technology is slated to be available in 2024 and is potentially retrofittable to existing facilities ( [[#Saevarsdottir--2020|Saevarsdottir et al. 2020]] ).

Smelting and otherwise processing of other non-ferrous metals like nickel, zinc, copper, magnesium and titanium with less overall emissions have relatively similar emissions reduction strategies ( [[#Bataille--2018|Bataille and Stiebert 2018]] ): (i) Increase material efficiency; (ii) Increase recycling of existing stock; (iii) Pursue ore-extraction processes (e.g., hydro- and electro-metallurgy) that allow more use of low-carbon electricity as opposed to pyrometallurgy, which uses heat to melt and separate the ore after it has been crushed. These processes have been used occasionally in the past but have generally not been used due to the relatively inexpensive nature of fossil fuels.

The pulp and paper industry (PPI) is a small net-emitter of CO 2, assuming the feedstock is sustainably sourced (Chapter 7), but it has large emissions of biogenic CO 2 from feedstock (700–800 Mt yr –1 ) ( [[#Tanzer--2021|Tanzer et al. 2021]] ). It includes pulp mills, integrated pulp and paper mills, and paper mills using virgin pulpwood and other fibre sources, residues and co-products from wood products manufacturing, and recycled paper as feedstock. Pulp mills typically have access to bioenergy in the chemical pulping processes to cover most or all of heat and electricity needs, for example, through chemicals recovery boilers and steam turbines in the kraft process. Mechanical pulping mainly uses electricity for energy; decarbonisation thus depends on grid emission factors. With the exception of the lime kiln in kraft pulp mills, process temperature needs are typically less than or equal to 150°C to 200°C, mainly steam for heating and drying. This means that this sector can be relatively easily decarbonised through continued energy efficiency, fuel switching and electrification, including use of high-temperature heat pumps ( [[#Ericsson--2018|Ericsson and Nilsson 2018]] ). Electrification of pulp mills could, in the longer term, make bio-residues currently used internally for energy, available as a carbon source for chemicals ( [[#Meys--2021|Meys et al. 2021]] ). The PPI also has the capabilities, resources and knowledge, to implement these changes. Inertia is mainly caused by equipment turnover rates, relative fuel and electricity prices, and the profitability of investments.

A larger and more challenging issue is how the forestry industry can contribute to the decarbonisation of other sectors and how biogenic carbon will be used in a fossil-free society, for example, through developing the forest-based bioeconomy ( [[#Pülzl--2014|Pülzl et al. 2014]] ; [[#Bauer--2018|Bauer 2018]] ). In recent years the concept of biorefineries has gained increasing traction. Most examples involve innovations for taking by-products or diverting small streams to produce fuels, chemicals and bio-composites that can replace fossil-based products, but there is little common vision on what really constitutes a biorefinery ( [[#Bauer--2017|Bauer et al. 2017]] ). Some of these options have limited scalability and the cellulose fibre remains the core product even in the relatively large shift from paper production to textiles fibre production.

Pulp mills have been identified as promising candidates for post-combustion capture and CCS ( [[#Onarheim--2017|Onarheim et al. 2017]] ), which could allow some degree of net-negative emissions. For deep decarbonisation across all sectors, notably switching to biomass feedstock for fuels, organic chemicals and plastics, the availability of biogenic carbon (in biomass or as biogenic CO 2 ; Chapter 7) becomes an issue. A scenario where biogenic carbon is CCU as feedstock implies large demands for hydrogen, completely new value chains and more closed carbon loops, all areas which are as yet largely unexplored ( [[#Ericsson--2017|Ericsson 2017]] ; [[#Meys--2021|Meys et al. 2021]] ).

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