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Solutions for producing greener steel

Marianne boix
Marianne Boix
Lecturer at Toulouse INP-ENSIACET
Fabrice Patisson
CNRS researcher and Professor at Nancy Ecole des Mines and head of the Energy-Processes Masters at University of Lorraine
Key takeaways
  • The steel industry is the world’s biggest emitter of greenhouse gases, accounting for 7% of global emissions.
  • In response to the new Green Industry Act and the demand for steel and iron, the sector is seeking to decarbonise the manufacture of these metals.
  • According to the IEA, the circular economy is an avenue in the short term, though sobriety should be encouraged as a priority.
  • “Direct carbon avoidance” and “intelligent carbon use” technologies are already proving their worth, but still need to be developed.
  • The EU and France are committed to a policy of relocalising industrial activity in order to minimise costs and environmental impact.

The Green Indus­try Act was passed on 11th Octo­ber 2023. Its main aim is to decar­bonise exist­ing indus­tries. The stakes are high: in France, indus­try account­ed for 18.1% of green­house gas (GHG) emis­sions in 20221. The iron and steel indus­try is one of the biggest sec­tors to be decar­bonised. In France, it is the 4th largest indus­tri­al sec­tor in terms of GHG emis­sions (20% of indus­tri­al GHG emis­sions, or 4% of the country’s total emis­sions). But on a glob­al scale, the sec­tor is in first place: around 2.8 bil­lion tonnes of CO2 are emit­ted every year in steel pro­duc­tion, or 7% of glob­al GHG emis­sions2. Yet demand is soar­ing. Steel and iron are essen­tial for con­struc­tion, mobil­i­ty, and the pro­duc­tion of renew­able ener­gy – a wind tur­bine is made up of more than two-thirds steel! Accord­ing to pro­jec­tions by the Inter­na­tion­al Ener­gy Agency (IEA), glob­al demand could increase by more than a third by 20503.

Note: STEPS = Stat­ed Poli­cies Sce­nario, SDS = Sus­tain­able Devel­op­ment Sce­nario
Source: IEA analy­sis informed in part by Pauliuk, Wang and Muller (2013), Cullen, All­wood and Bam­bach (2012) and Gibon et al. (2017)

How is steel made?

There are two main meth­ods used around the world to pro­duce steel, an alloy of iron and car­bon. 70% comes from the cast iron process4: iron ore is intro­duced into a blast fur­nace in the pres­ence of coke (pro­duced from the pyrol­y­sis of coal) and trans­formed into cast iron through chem­i­cal reduc­tion. Dur­ing this stage, the car­bon com­bines with the oxy­gen con­tained in the ore to form CO2. The cast iron is then trans­formed into steel in a con­vert­er. Anoth­er process used is the elec­tric arc fur­nace. This method is wide­ly used to recy­cle scrap met­al, which is melt­ed in an elec­tric arc fur­nace. There are sev­er­al alter­na­tive meth­ods: for exam­ple, ore can be used in the elec­tric arc process. In this case, the iron is extract­ed from the ore by direct reduc­tion using coal or nat­ur­al gas, before being trans­formed into steel in the elec­tric arc furnace.

Steel­mak­ing requires large quan­ti­ties of ener­gy: for exam­ple, melt­ing reach­es 1,500°C in the blast fur­nace. Yet in 2019, three quar­ters of the ener­gy con­sumed by the sec­tor was sup­plied by coal. To date, recy­cling with­in the elec­tric­i­ty sec­tor is the most car­bon-free option. It requires only one eighth of the ener­gy of steel pro­duced from ore, and main­ly in the form of elec­tric­i­ty rather than coal. “We need to increase the recy­cled pro­por­tion, but this sec­tor is lim­it­ed by resources: a large pro­por­tion of steel, for exam­ple, is immo­bilised for decades in build­ings,” explains Fab­rice Patisson.

Several effective short- and long-term solutions

In the short term, the cir­cu­lar econ­o­my is the most promis­ing dri­ver. Tech­no­log­i­cal inno­va­tions for decar­bon­i­sa­tion are based on renew­ing the pro­duc­tion fleet, which has an aver­age age of 13 years world­wide, or less than a third of its tra­di­tion­al lifes­pan. In its for­ward-look­ing sce­nario aim­ing for a 50% reduc­tion in the sector’s emis­sions by 2050, the IEA points out that 40% of the cumu­la­tive reduc­tions in GHG emis­sions between 2020 and 2050 are based on the cir­cu­lar econ­o­my. Sim­ply put, this is the lever for ener­gy sobri­ety: by reduc­ing demand, emis­sions are reduced. This main­ly involves extend­ing the lifes­pan of build­ings, but also improv­ing man­u­fac­tur­ing effi­cien­cy, reduc­ing the use of cars and mak­ing them lighter, improv­ing build­ing design and reusing steel.

At the same time, a num­ber of oth­er solu­tions are avail­able. It is impos­si­ble to meet ris­ing demand with­out pro­duc­ing pri­ma­ry steel. One of the major levers for decar­bon­is­ing pro­duc­tion? Mov­ing away from coal. The steel industry’s high GHG emis­sions are main­ly due to the for­ma­tion of CO2 in blast fur­naces through chem­i­cal reac­tions, and the high tem­per­a­tures required. “Green” iron would be pro­duced by the direct reduc­tion of iron ore using elec­tric­i­ty or green hydro­gen (H2), instead of coke. It can then be inte­grat­ed into the usu­al elec­tric­i­ty chain and trans­formed into steel in an elec­tric arc fur­nace. This tech­nol­o­gy is known as “direct car­bon avoid­ance”. “To date, the direct reduc­tion process is well known and wide­spread – it accounts for around 7% of the world’s steel – but it relies on the use of syn­gas (a syn­thet­ic gas derived from nat­ur­al gas), which con­tains around 60% H2,” explains Fab­rice Patis­son. “The biggest chal­lenge is to go to 100% H2 on an indus­tri­al scale.”

The hydro­gen route is the most advanced: of the 60 steel decar­bon­i­sa­tion projects iden­ti­fied in Europe in Novem­ber 2022, 42 are based on the use of hydro­gen5. In Swe­den, the Hybrit pilot project has been pro­duc­ing the world’s first tonnes of steel using this process since 2021. It could reduce CO2 emis­sions by 85%6. “From now on, the devel­op­ment of the sec­tor depends on the will­ing­ness and capac­i­ty of steel­mak­ers to invest,” says Fab­rice Patis­son. As for elec­tric­i­ty require­ments – if hydro­gen is pro­duced by elec­trol­y­sis of water, they would amount to 370 TWh to decar­bonise all the EU’s pri­ma­ry steel pro­duc­tion7, or 14% of cur­rent total elec­tric­i­ty pro­duc­tion8.

There is anoth­er tech­no­log­i­cal route – one that is com­ple­men­tary to the car­bon avoid­ance route – and that is the “intel­li­gent use of car­bon”. This involves opti­mis­ing exist­ing pro­duc­tion process­es. Even if the indus­try has mas­tered blast fur­naces, there is still room for improve­ment. It has been shown, for exam­ple, that more than half of the ener­gy pur­chased by steel­mak­ers is lost dur­ing the process9. Using the best avail­able tech­nolo­gies and opti­mis­ing process­es could make it pos­si­ble to reduce the sector’s cumu­la­tive glob­al emis­sions by 21% between 2020 and 2050, accord­ing to the IEA’s for­ward-look­ing sce­nario, which aims to reduce the sector’s emis­sions by 50% by 20503. This involves deploy­ing heat recov­ery sys­tems, improv­ing coke qual­i­ty, par­tial­ly replac­ing coal with nat­ur­al gas or bioen­er­gy, and imple­ment­ing pre­dic­tive main­te­nance tools.

Car­bon cap­ture and stor­age is an effec­tive option in the short term, before clean tech­nolo­gies – such as hydro­gen – are deployed

Intel­li­gent use of car­bon also involves its recov­ery. As in many indus­tri­al sec­tors, the cap­ture and recov­ery or stor­age of CO2 is seen as essen­tial if we are to make a suc­cess of the tran­si­tion by 2050. Accord­ing to the IEA, this could make it pos­si­ble to cap­ture 6% of the emis­sions gen­er­at­ed between 2020 and 2050, with the cap­ture rate ris­ing to 25% per year by 2050. Only one com­mer­cial CO2 stor­age unit cur­rent­ly exists in the world, in the Unit­ed Arab Emi­rates. A few recov­ery projects are cur­rent­ly under devel­op­ment. “CO2 cap­ture is eas­i­er in the steel indus­try than in oth­ers,” adds Fab­rice Patis­son. “Cap­ture and stor­age is an effec­tive option in the short term, before clean tech­nolo­gies – such as hydro­gen – are deployed.”

Final­ly, the EU and France are com­mit­ted to a pol­i­cy of relo­cat­ing indus­tri­al activ­i­ty. Gone are the emis­sions asso­ci­at­ed with trans­port­ing prod­ucts. France’s ener­gy mix, with its rel­a­tive­ly low car­bon foot­print, is also an advan­tage in terms of GHG emis­sions. One of the avenues being explored is the devel­op­ment of clus­ters of activ­i­ty based on an indus­tri­al ecol­o­gy approach. “The aim of this approach is to design activ­i­ty clus­ters, like eco­parks, that opti­mise the exchange of flows between dif­fer­ent man­u­fac­tur­ers,” explains Mar­i­anne Boix. “By pool­ing ser­vices, the sup­ply chain, ener­gy and raw mate­ri­als, envi­ron­men­tal impacts and costs are min­imised.” GHG emis­sions can be cut by up to 75% com­pared with the same plant with­out coop­er­a­tion10. The Arcelor­Mit­tal site in Dunkirk is a case in point: the slag – a by-prod­uct of the blast fur­naces – is recy­cled as a build­ing mate­r­i­al, and the waste heat is fed into Dunkirk’s munic­i­pal heat­ing net­work11. Two new EPR nuclear reac­tors are due to be built there, as well as a green hydro­gen pro­duc­tion unit… which will be able to sup­ply ArcelorMittal’s future direct hydro­gen ore reduc­tion unit12. Mar­i­anne Boix con­cludes: “Inte­grat­ing the hydro­gen vec­tor into eco­parks makes the process prof­itable, both eco­nom­i­cal­ly and envi­ron­men­tal­ly. It’s a very inter­est­ing oppor­tu­ni­ty in this context.”

Anaïs Marechal
1Citepa, 2023. Gaz à effet de serre et pol­lu­ants atmo­sphériques. Bilan des émis­sions en France de 1990 à 2022. Rap­port Secten éd. 2023
4Site inter­net con­sulté le 04/10/2023 : https://​world​steel​.org/​a​b​o​u​t​-​s​t​e​e​l​/​a​b​o​u​t​-​s​teel/
5Site inter­net con­sulté le 04/10/2023 : https://​www​.euro​fer​.eu/​i​s​s​u​e​s​/​c​l​i​m​a​t​e​-​a​n​d​-​e​n​e​r​g​y​/​m​a​p​s​-​o​f​-​k​e​y​-​l​o​w​-​c​a​r​b​o​n​-​s​t​e​e​l​-​p​r​o​jects
7Sylvie Cornot, « La sidérurgie européenne se pré­pare pour être à la pointe de la décar­bon­a­tion », Notes de l’Ifri, Ifri, jan­vi­er 2023.
11Site inter­net con­sulté le 05/10/2023 : https://​france​.arcelor​mit​tal​.com/​e​n​g​a​g​e​m​e​n​t​s​/​e​n​v​i​r​o​n​n​e​m​e​n​t​/​e​c​o​n​o​m​i​e​-​c​i​r​c​u​laire
12 Site inter­net con­sulté le 05/10/2023 : https://​france​.arcelor​mit​tal​.com/​n​e​u​t​r​a​l​i​t​e​-​c​a​r​b​o​n​e​/​d​r​i​-​h​y​d​r​ogene

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