Why is European steel lower carbon than UK steel?


Why is European steel lower carbon than UK steel?

The lower average carbon footprint of European steel production is simply a function of the steel production split within Europe compared to that in the UK.

Steel is predominantly manufactured by either of two process routes, namely the primary or basic oxygen steel-making route (BF-BOF) and the secondary, electric arc furnace (EAF) route.

In Europe the production split (for all steel) is around 60:40 (BF-BOF:EAF). In the UK the production split is currently 80:20 (BF-BOF:EAF).

Typically, the EAF steel-making process has a carbon footprint around 20% that of BF-BOF steelmaking. Therefore, the European and UK average carbon footprint values for steel reflect these different production splits.

As a globally traded product, a UK average production mix for steel sections is meaningless. Instead, and where the steel supplier is unknown, for example at the early design stage, the BCSA recommends the following average UK emissions factors for embodied carbon assessments of structural steelwork:

• For Modules [A1-A3], 1.74 tonne CO2e per tonne of sections.
• For Module [D], − 0.93 tonne CO2e per tonne of sections.

Although on average this may be true, it is not the case on an individual company or individual steel mill basis. This is one of the downsides of using average production values for steel making carbon emissions. The lower average carbon footprint of European steel production is simply a function of the production split within Europe compared to that in the UK, as explained below.

Steel is predominantly (> 99% globally) manufactured by either of two process routes, namely the basic oxygen steel-making route (BF-BOF) and the electric arc furnace (EAF) route. Globally, in 2019, the production split was circa 70% BF-BOF and 30% EAF [3].

In basic oxygen steelmaking, molten iron is produced from iron ore, using a Blast Furnace (BF), and then refined in a BOF converter to which scrap steel is also added (up to 30%). The actual proportion of scrap is dependent upon a number of factors including the availability and price of scrap and the specification or quality of the steel being produced. In addition to saving iron ore, the scrap is an important part of the steel-making process, i.e. it is used to regulate the temperature of the steel in the furnace. EAF production is primarily a scrap-recycling route, which involves melting 100% steel scrap to which small amounts of fluxes and reducing agents are added.

In Europe, both steel-making routes are used, the production split (for all steel) being around 60:40 (BF-BOF:EAF) in 2019. In the UK the production split is currently 80:20 (BF-BOF:EAF) [3].

Typically, the EAF steel-making process has a carbon footprint around 20% that of BF-BOF steelmaking. Therefore, the European and UK average carbon footprint values for steel reflect these production splits.

As a globally traded product, a UK average production mix for steel sections is meaningless. Instead, and where the steel supplier is unknown, for example at the early design stage, the BCSA recommends the following average UK emissions factors for embodied carbon assessments of structural steelwork:

  • For Modules [A1-A3], 1.74 tonne CO2e per tonne of sections.
  • For Module [D], − 0.93 tonne CO2e per tonne of sections.

Whereas there are historical and other reasons why the production split varies between different countries and regions, globally the ability to make steel via the EAF route is limited by the availability of steel scrap. This explains why, despite unrivalled end-of-life recovery rates for steel products, see [8], it is not currently possible for all designers to specify EAF steel. This will change however as the stock of steel in buildings and infrastructure in developing countries grows and stabilises. At this point, a steady state will exist in which demand for new steel can be met entirely through the supply of scrap and no further BF-BOF or primary steel production is required, see Box 1 for further information. The challenge for the steel industry and wider society, is how we transition to this sustainable ‘steady state’ against the backdrop of addressing the current climate emergency.

Although there is some variation in BF-BOF carbon emissions between steel companies, this variation is small and is mainly a function of the proportion of scrap used in the process. BF-BOF production is highly efficient, and the average energy intensity of steel making is now within 10% of best practice and best practice is just double the unattainable absolute theoretical limit. No other industry operates so close to its theoretical performance limit [4]. BF-BOF emissions for structural sections and plates are around 2.4 tCO2e per tonne.

EAF carbon emissions vary depending primarily on the electricity grid mix in the country or region of production. EAF emissions for structural steel sections in Europe is currently around 0.5 tCO2e per tonne. Policies to decarbonise the electricity grid should reduce these emissions further.

Transition of the global steel industry from primary to secondary steelmaking

Figure 2 shows a prediction of global steel demand to 2050. Although it is difficult to predict the future with certainty, experience shows that as countries develop their per capita requirement for steel levels off at a stock of around 12 tonnes of steel per person.

Figure 3 shows the rise in steel stock in five developed countries over time as GDP increases [4].
Demand for steel after this ‘saturation point’ is for replacement, i.e. recycling, rather than expansion through BF-BOF production from iron ore.

Combining this ‘saturation value’ with the predicted life expectancies of steel products, it is possible to predict future global demand and, assuming that most future scrap arisings are recycled, how the global split of BF-BOF and EAF production and associated carbon emissions, will evolve over time. Figure 4 shows this.

Global steel demand will eventually reach a limit when steel stocks stabilise and the requirement for primary production reduces to (nearly) zero, as future requirements are met entirely through recycling.
Further grid decarbonation will enable us to have a truly sustainable, zero carbon, global steel industry. The challenge the steel industry is now tackling is how to reduce BF-BOF carbon emissions while we still need steelmaking from iron ore and we transition to steel-making based solely on recycling scrap and reuse.

Combining this ‘saturation value’ with the predicted life expectancies of steel products, it is possible to predict future global demand and, assuming that most future scrap arisings are recycled, how the global split of BF-BOF and EAF production and associated carbon emissions, will evolve over time. Figure 4 shows this.

Global steel demand will eventually reach a limit when steel stocks stabilise and the requirement for primary production reduces to (nearly) zero, as future requirements are met entirely through recycling.

Further grid decarbonation will enable us to have a truly sustainable, zero carbon, global steel industry. The challenge the steel industry is now tackling is how to reduce BF-BOF carbon emissions while we still need steelmaking from iron ore and we transition to steel-making based solely on recycling scrap and reuse.