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

==== 11.4.1.1 Steel ====

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For the period leading up to 2020, in terms of end-use allocation globally, approximately 40% of steel is used for structures, 20% for industrial equipment, 18% for consumer products, 13% for infrastructure, and 10% for vehicles ( [[#Bataille--2020b|Bataille 2020b]] ). The global production of crude steel increased by 41% between 2008 and 2020 ( [[#World%20Steel%20Association--2021|World Steel Association 2021]] ) and its GHG emissions, depending on the scope covered, is 3.7–4.1 GtCO 2 -eq. It represented 20% of total global direct industrial emissions in 2019 accounting for coke oven and blast furnace gases use ( [[#Crippa--2021|Crippa et al. 2021]] ; [[#Lamb--2021|Lamb et al. 2021]] ; [[#Minx--2021|Minx et al. 2021]] ; Olivier and Peters 2018; [[#World%20Steel%20Association--2021|World Steel Association 2021]] ; [[#IEA--2020a|IEA 2020a]] ) (Figure 11.4 and [[#_idTextAnchor023|Table 11.1]] ). Steel production can be divided into primary production based on iron ore and secondary production based on steel scrap. The blast furnace-basic oxygen furnace route (BF-BOF) is the main primary steel route globally, while the electric arc furnace (EAF) is the preferred process for the less energy and emissions-intensive melting and alloying of recycled steel scrap. The direct reduced iron (DRI) route is a lesser-used route that replaces BFs for reducing iron ore, usually followed by an EAF. In 2019, 73% of global crude steel production was produced in BF-BOFs, while 26% was produced in EAFs, a nominal 5.6% of which is DRI ( [[#World%20Steel%20Association--2021|World Steel Association 2021]] ).

An estimated 15% energy efficiency improvement is possible within the BF-BOF process (Figure 11.8). Several options exist for deep-GHG emissions reductions in steel-production processes ( [[#Fischedick--2014|Fischedick et al. 2014]] b; [[#Leeson--2017|Leeson et al. 2017]] ; [[#Axelson--2018|Axelson et al. 2018]] ; [[#Vogl--2018|Vogl et al. 2018]] ; [[#Bataille--2020a|Bataille 2020a]] ; [[#Holappa--2020|Holappa 2020]] ; [[#Rissman--2020|Rissman et al. 2020]] ; [[#Fan--2021|Fan and Friedmann 2021]] ; [[#Wang--2021|Wang et al. 2021]] ).Each could reduce specific CO 2 emissions of primary steel production by 80% or more relative to today’s dominant BF-BOF route if input streams are based on carbon-free energy and feedstock sources or if they deploy high-capture CCS:

• '''Increasing the share of the secondary route''' can bring down emissions quickly and potential emissions savings are significant, from a global average 2.3 tCO 2 –1 per tonne steel in BF-BOFs down to 0.3 (or less) tCO 2 –1 per tonne steel in EAFs ( [[#Pauliuk--2013a|Pauliuk et al. 2013a]] ; [[#Zhou--2019|Zhou et al. 2019]] ), the latter depending on scrap preheating and electricity GHG intensity. However, realising this potential is dependent on the availability of regional and global scrap supplies and requires careful sorting and scrap management, especially to eliminate copper contamination ( [[#Daehn--2017|Daehn et al. 2017]] ). There is significant uncertainty about how much new scrap will be available and usable ( [[#Xylia--2018|Xylia et al. 2018]] ; [[#IEA--2019b|IEA 2019b]] ; [[#Wang--2021|Wang et al. 2021]] ). Most steel is recycled already; the gains are mainly to be made in quality (i.e., separation from contaminants like copper). End-of-life scrap availability and its contribution to steel production will increase as in use stock saturates in many countries ( [[#Xylia--2016|Xylia et al. 2016]] ).

'''•''' '''BF-BOFs with CCU or CCS.''' [[#Abdul%20Quader--2016|Abdul Quader et al. (2016)]] and [[#Fan--2021|Fan and Friedmann (2021)]] indicate that it would be difficult to retrofit BF-BOFs beyond 50% capture, which is insufficient for long-term emission targets but may be useful in some cases for avoiding cumulative emissions where other options are not available. However, BF-BOFs need their furnaces relined every 15–25 years ( [[#IEA--2021a|IEA 2021a]] ; [[#Vogl--2021b|Vogl et al. 2021b]] ), at a cost of 80–100% of a new build, and this would be an opportunity to build a new facility designed for 90%+ capture (e.g., fewer CO 2 outlets). This would depend upon access to transport to geology appropriate for CCS.

'''•''' '''Methane-based syngas (hydrogen and carbon monoxide) direct reduced iron (DRI) with CCS''' . Most DRI facilities currently use a methane-based syngas of H 2 and CO as both reductant and fuel (some use coal). A syngas DRI-EAF steel-making facility has been operating in Abu Dhabi since 2016 that captures carbon emitted from the DRI furnace (where it is a co-reductant with hydrogen) and sends it to a nearby oil field for enhanced oil recovery.

'''•''' '''Hydrogen-based direct reduced iron (H-DRI)''' is based on the already commercialised DRI technology but using only hydrogen as the reductant; pure hydrogen has already been used commercially by Circored in Trinidad 1999–2008. The reduction process of iron ore is typically followed by an EAF for smelting. During a transitional period, DRI could start with methane or a mixture of methane and hydrogen as some of the methane (≤30% hydrogen can be substituted with green or blue hydrogen without the need to change the process). If the hydrogen is produced based on carbon-free sources, this steel-production process can be nearly CO 2 neutral ( [[#Vogl--2018|Vogl et al. 2018]] ).

'''•''' '''In the aqueous electrolysis route''' (small-scale piloted as Siderwin during the EU ULCOS programme), the iron ore is bathed in an electrolyte solution and an electric current is used to remove the oxygen, followed by an electric arc furnace for melting and alloying.

'''•''' In the ''molten'' '''oxide electrolysis''' route, an electric current is used to directly reduce and melt the iron ore using electrolysis in one step, followed by alloying. These processes both promise a significant increase in energy efficiency compared with the direct reduced iron (DRI) and blast furnace routes ( [[#Cavaliere--2019|Cavaliere 2019]] ). If the electricity used is based on carbon-free sources, this steel-production process can be nearly CO 2 neutral. Both processes would require supplemental carbon, but this is typically only up to 0.05% per tonne steel, with a maximum of 2.1%. Aqueous electrolysis is possible with today’s electrode technologies, while molten oxide electrolysis would require advances in high-temperature electrodes.

'''•''' '''The''' '''HIsarna® process''' is a new type of coal-based smelting reduction process, which allows certain agglomeration stages (coking plant, sintering/pelletising) to be dispensed with. The iron ore, with a certain amount of steel scrap, is directly reduced to pig iron in a single reactor. This process is suitable to be combined with CCS technology because of its relatively easy to capture and pure CO 2 exhaust gas flow. CO 2 emission reductions of 80% are believed to be realisable relative to the conventional blast furnace route ( [[#Abdul%20Quader--2016|Abdul Quader et al. 2016]] ). The total GHG balance also depends on further processing in a basic oxygen furnace or in an EAF. The HIsarna process was small-scale piloted under the EU ULCOS program.

• '''Hydrogen co-firing''' '''in BF-BOFs''' can potentially reduce emission by 30–40%, referring to experimental work by the Course50 projects and Thyssen Krupp, but coke is required to maintain stack integrity beyond that.

Reflecting the different conditions at existing and potential future plant sites, when choosing one of the above options a combination of different measures and structural changes (including electricity, hydrogen and CCU or CCS infrastructure needs) will likely be necessary in the future to achieve deep reductions in CO 2 emissions of steel production.

In addition, increases in material efficiency (e.g., more targeted steel use per vehicle, building or piece of infrastructure) and increases in the intensity of product use (e.g., sharing cars instead of owning them) can contribute significantly to reduce emissions by reducing the need for steel production. The [[#IEA--2019b|IEA (2019b)]] suggested that up to 24% of cement and 40% of steel demand could be plausibly reduced through strong material efficiency efforts by 2060. Potential material efficiency contribution for the EU is estimated to be much higher – 48% ( [[#Material%20Economics--2019|Material Economics 2019]] ). Recycling would cut the average CO 2 emissions per tonne of steel produced by 60% ( [[#Material%20Economics--2019|Material Economics 2019]] ), but globally by 2050 secondary steel production is limited to 40–56% in various scenarios ( [[#IEA--2019b|IEA 2019b]] ), with 46% in the [[#IEA--2021a|IEA (2021a)]] and up to 56% in 2050 in [[#Xylia--2016|Xylia et al. (2016)]] . It may scale up to 68% by 2070 ( [[#Xylia--2016|Xylia et al. 2016]] ). CCU and more directly CCS are other options to reduce GHG emissions but depend on the full lifecycle net GHGs that can be allocated to the process ( [[#11.3.6|Section 11.3.6]] ). Bio-based fuels can also substitute for some of the coal input, but due to other demands for biomass this strategy is likely to be limited to specific cases.

Abatement costs for these strategies vary considerably from case to case and for each a plausible cost range is difficult to establish; compare this with '''Table 11.3''' ( [[#Fischedick--2014|Fischedick et al. 2014]] b; [[#Leeson--2017|Leeson et al. 2017]] ; [[#Axelson--2018|Axelson et al. 2018]] ; [[#Vogl--2018|Vogl et al. 2018]] ; [[#Fan--2021|Fan and Friedmann 2021]] ; [[#Wang--2021|Wang et al. 2021]] ). A key point is that while cost of production increases are significant, the effect on final end uses is typically very small ( [[#Rootzén--2016|Rootzén and Johnsson 2016]] ), with significant policy consequences (see [[#11.6|Section 11.6]] on public and private lead markets for cleaner materials).

'''Table 11.3 | Technological potentials and costs for deep decarbonisation of basic industries.''' Percentages of maximum reduction are multiplicative, not additive.

{| class="wikitable"
|-
! Sector

! Current intensity (tCO 2 -eq t –1 )

! Potential GHG reduction

! NASA TRL

! Cost per tonne CO 2 -eq

(USD2019 tCO 2 -eq –1 for percentage of emissions)

? = unknown

! Year available, assuming policy drivers

|-
| colspan="6"| '''Iron and steel'''

|-
| Current intensity – all steel (worldsteel)

| 1.83

|
|-
| Current intensity – ~BF-BOF/Best BF-BOF and NG-DRI (with near-zero GHG electricity)

| 2.3/1.8 and 0.7

|
|-
| Current intensity – EAF (depends on electricity intensity &amp; pre-heating fuel)

| ≥0

| Up to 99%

|
|-
| Material efficiency (IEA 2019 ‘Material Efficiency…’)

|
| Up to 40%

| 9

| Subject to supply chain building codes and education

| Today

|-
| More recycling; depends on available stock, recycling network, quality of scrap, availability of DRI for dilution

|
| Highly regional, growing with time

| 9

| Subject to logistical, transport, sorting and recycling equipment costs

| Today

|-
| BF-BOF with top gas recirculation and CCU/S a

|
| 60%

| 6–7

| USD70–130 t –1

| 2025–2030

|-
| Syngas (H 2 &amp; CO) DRI EAF with concentrated flow CCU/S

|
| ≥ 90%

| 9

| ≥USD40 t –1

| Today

|-
| Hisarna with concentrated CO 2 capture b

|
| 80–90%

| 7

| USD40–70 t –1

| 2025

|-
| Hydrogen DRI EAF c – fossil hydrogen with CCS is in operation, electrolysis-based hydrogen scheduled for 2026

|
| Up to 99%

| 7

| USD39–79 t –1 and USD46 MWh –1 d

| 2025

|-
| Aqueous (e.g., SIDERWIN) or Molten Oxide (e.g., Boston Metals) Electrolysis (MOE) e

|
| Up to 99%

| 3–5

| ?

| 2035–2040

|-
| colspan="6"| '''Cement and concrete'''

|-
| Current intensity, about 60% is limestone calcination

| 0.55

|
|-
| Building design to minimise concrete ( [[#IEA--2019b|IEA 2019b]] , 2020a)

|
| Up to 24%

| 9

| Low, education, design and logistics related

| 2025

|-
| Alternative lower-GHG fuels, e.g., waste (biofuels and hydrogen, see above)

|
| 40%

| 9

| Cost of alt. fuels

| Today

|-
| CCUS for process heating &amp; CaCO 3 calcination CO 2 (e.g., LEILAC, possible retrofit) f

|
| 99% calc., ≤90% heat

| 5–7

| ≤USD40t –1 calc. ≤USD120t –1 heat

| 2025

|-
| Clinker substitution (e.g., limestone + calcined clays) g

|
| 40–50%

| 9

| Near zero, education, logistics, building code revisions

| Today

|-
| Use of multi-sized and well-dispersed aggregates d

|
| Up to 75%

| 9

| Near zero

| Today

|-
| Magnesium or ultramafic cements d

|
| Negative?

| 1–4

| ?

| 2040

|-
| colspan="6"| '''Aluminium and other non-ferrous metals'''

|-
| Current Al intensity, from hydro- to coal-based electricity production. 1.5 tCO 2 are produced by graphite electrode decay

| 1.5 t –1 + electricity required (i.e., 10 t –1 (NG) to 18 t –1 (coal))

|
|-
| Inert electrodes and green electricity h

|
| 100%

| 6–7

| Relatively low

| 2024

|-
| Hydro/electrolytic smelting (with CO 2 CCUS if necessary)

|
| Up to 99%

| 3–9

| Ore-specific

| &lt;2030

|-
| colspan="6"| '''Chemicals (see also cross-cutting feedstocks above)i'''

|-
| Catalysis of ammonia from low-/zero-GHG hydrogen H 2

| 1.6 (NG), 2.5 (naptha), 3.8 (coal)

| ≤99%

| 9

| Cost of H 2

| Today

|-
| Electrocatalysis: CH 4 , CH 3 OH, C 2 H 5 OH, CO, olefins j

|
| Up to 99%

| 3

| Cost: elec., H 2 , CO x

| 2030

|-
| Catalysis of olefins from: (m)ethanol, H 2 and CO x directly

|
| 9%

| 9, 3

| Cost: H 2 and CO x

| &lt;2030

|-
| End-use plastics, mainly CCUS and recycling

| 1.3–4.2, about 2.4

| 94%

| 5–6

| USD150–240 t –1

| 2030?

|-
| colspan="6"| '''Pulp and paper'''

|-
| Full biomass firing, including lime kilns

|
| 60–75%

| 9

| About USD50 t –1

| Today

|-
| colspan="6"| '''Other manufacturing'''

|-
| Electrification using current tech (boilers, 90 °C –140 ° C heat pumps

|
| 99%

| 9

| Cost: elec. vs NG

| 2025

|-
| Using new tech (induction, plasma heating)

|
| 99%

| 3–6

|
| 2025

|-
| colspan="6"| '''Cross-cutting (CCUS, H''' ''2'' ''', net zero C''' ''o'' '''O''' ''x'' '''H''' ''y'' '''fu''' '''els/feedstocks)'''

|-
| CCUS of post-combustion CO 2 diluted in nitrogen e

|
| Up to 90%

| 6–7

| ≤USD120 t –1

| 2025

|-
| CCUS of concentrated CO 2 e

|
| 99%

| 9

| ≤USD40 t –1

| Today

|-
| H 2 production: steam or auto-thermal CH 4 reforming with CCS e

|
| SMR ≤90% ATR &gt;90%

| 6*, 9**

| 56% @≤USD40 t –1 chem**, ≤USD120 heat*,+20%/kg

| ≤2025

|-
| H 2 production: coal with CCUS e

|
| ≤90%

| 6

| 25–50% per H 2 kg –1

| ≤2025

|-
| H 2 production: alkaline or PEM electrolysis k

|
| 99%

| 9

| About USD50 t –1 or &lt;USD20–30 MWh –1

| Today

|-
| H 2 production: reversible solid oxide fuel electrolysis j

|
| 99%

| 6–8

| About 40USD t –1 or &lt;USD40 MWh –1

| 2025

|-
| H 2 production: CH 4 pyrolysis or catalytic cracking l

|
| 99%

| 5

| ?

| 2030?

|-
| Hydrogen as CH 4 replacement

|
| ≤10%

| 9

| See above

| Today

|-
| Biogas or liquid replacement hydrocarbons

|
| 60–90%

| 9

| Biomass USD per GJ –1 ; ≥USD50 t –1 , uncertain

| Today

|-
| Anaerobic digestion/fermentation: CH 4 , CH 3 OH and C 2 H 5 OH m

|
| Up to –99%

| 9

| Biomass cost

| Today

|-
| Methane or methanol from H 2 and CO x (CCUS for excess). Maximum –50% reduction if C source is FF

|
| 50–99%

| 6–9

| Cost: H 2 and CO x

| Today

|-
| 850°C woody biomass gasification with CCS for excess carbon: CO, CO 2 , H 2 , H 2 O, CH 4 , C 2 H 4 and C 6 H 6 n

|
| Could be negative

| 7–8

| About USD50–75 t –1 , uncertain

| Today

|-
| Direct air capture for short- and long-chain C o O x H y o

|
| Up to 99%

| 3

| Cost: E, H 2, CO x about USD94–232 t –1

| ≤2030

|}

a Data for CCS costs for steel-making: [[#Birat--2012|Birat (2012)]] ; [[#Leeson--2017|Leeson et al. (2017)]] ; and [[#Axelson--2018|Axelson et al. (2018)]] .

b Data for Hisarna: [[#Axelson--2018|Axelson et al. (2018)]] .

c Data for hydrogen DRI electric arc furnaces: [[#Fischedick--2014b|Fischedick et al. (2014b)]] and [[#Vogl--2018|Vogl et al. (2018)]] .

d Converted from EUR2018 34–68 t –1 and EUR2018 40 MWh –1 .

e Data for Molten Oxide Electrolysis (also known as SIDERWIN): [[#Fischedick--2014|Fischedick et al. 2014]] b and [[#Axelson--2018|Axelson et al. 2018]] . The TRLs differ by source, the value provided is from [[#Axelson--2018|Axelson et al. (2018)]] , based on UCLOS SIDERWIN.

f Data for making hydrogen from SMR and ATR with CCUS: [[#Leeson--2017|Leeson et al. (2017)]] ; [[#Moore--2017|Moore (2017)]] ; and [[#IEA--2019f|IEA (2019f)]] . The cost of CCS disposal of concentrated sources of CO 2 at USD15–40 tCO 2 -eq –1 is well established as commercial for direct or EOR purposes and is based on the long-standing practice of disposing of hydrogen sulphide and oil brines underground: [[#Wilson--2003|Wilson et al. (2003)]] and [[#Leeson--2017|Leeson et al. (2017)]] . There is a wide variance, however, in estimated tCO 2 -eq –1 break-even prices for industrial post-combustion capture of CO 2 from sources highly diluted in nitrogen (e.g., [[#Leeson--2017|Leeson et al. (2017)]] at USD60–170 tCO 2 -eq –1 ), but most fall under USD120 tCO 2 -eq –1 .

g Data for clinker substitution and use of well-mixed and multi-sized aggregates: [[#Fechner--2012|Fechner and Kray 2012]] ; [[#Lehne--2018|Lehne and Preston 2018]] ; and [[#Habert--2020|Habert et al. 2020]] ).

h Rio Tinto, Alcoa and Apple have partnered with the governments of Québec and Canada to form a coalition to commercialise inert as opposed to sacrificial graphite electrodes by 2024, thereby making the standard Hall-Héroult process very low emissions if low-carbon electricity is used.

i Data and other information: [[#Bazzanella--2017|Bazzanella and Ausfelder (2017)]] ; [[#Axelson--2018|Axelson et al. (2018)]] ; [[#IEA--2018a|IEA (2018a)]] ; [[#De%20Luna--2019|De Luna et al. (2019)]] ; and Philibert (2017b,a).

j See [[#De%20Luna--2019|De Luna et al. (2019)]] for a state-of-the-art review of electrocatalysis, or direct recombination of organic molecules using electricity and catalysts.

k Data for hydrogen production from electrolysis: [[#Bazzanella--2017|Bazzanella and Ausfelder (2017)]] ; [[#Philibert--2017a|Philibert (2017a)]] ; [[#Philibert--2017b|Philibert (2017b)]] ; [[#IEA--2019f|IEA (2019f)]] ; and [[#Armijo--2020|Armijo and Philibert (2020)]] .

l Data for methane pyrolysis to make hydrogen: Abbas and Wan Daud (2010). Data for hydrogen production from methane catalytic cracking: [[#Amin--2011|Amin et al. (2011)]] and [[#Ashik--2015|Ashik et al. (2015)]] .

m Data for anaerobic digestion or fermentation for the production of methane, methanol and ethanol: [[#De%20Luna--2019|De Luna et al. (2019)]] .

n Data for woody biomass gasification: [[#Li--2019|Li et al. (2019)]] and [[#van%20der%20Meijden--2011|van der Meijden et al. (2011)]] .

o Data on direct air capture of CO 2 : [[#Keith--2018|Keith et al. (2018)]] and [[#Fasihi--2019|Fasihi et al. (2019)]] .

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