How much methane is emitted into the atmosphere each year due to steel making?

The answer, surprisingly, seems to be that no one really knows.

To date, estimates of steel’s methane emissions have focussed on the sector’s use of ‘metallurgical coal’. Metallurgical coal includes various grades of coal used for coke making (‘coking coal’), as well as coal that is crushed and injected directly into a blast furnace – referred to as ‘pulverised coal for injection’ (PCI)¹.

Metallurgical coal comprises more than 10% of all global coal production. However, because it tends to occur in deeper, more compressed seams than the ‘thermal’ coal (also known as ‘steam’ coal) that is used for power generation, it is associated with around 30% of coal’s total methane emissions.

In addition to the use of coke and PCI in the blast furnace, there are at least four other aspects of steel production that may be associated with the emission of methane:

• The extraction, transportation and use of metallurgical coal for the production of ferro-metallics
• Charcoal making for the production of pig iron
• The extraction, transportation and use of natural gas for the production of direct reduced iron (DRI)
• The extraction, transportation and use of thermal coal and natural gas for the generation of electricity

I couldn’t find any figures for steel’s GHG emissions including these sources of methane. In the absence of anything better, I have tried to estimate them myself. Let me be the first to acknowledge that these are back-of-the-envelope guesstimates. If anyone can point me towards better estimates, please do – I will be happy to update!

Let’s take them one at a time.

Metallurgical coal is used not only for the production of iron, but also for the production of ferro-metallics such as ferro-chromium and ferro-silicon. However, these ferro-metallics are themselves inputs for the production of stainless steel and steel more generally. For the purposes of this post I have assumed that the steel sector is responsible for essentially all consumption of metallurgical coal – whether it is used directly in the production of iron or steel, or indirectly for the production of ferro-metallics. The global consumption of metallurgical coal was estimated to be 1.1 billion tonnes in 2023², so that is the figure I have attributed to the steel sector.

The IEA estimated that mines producing coking coal emitted 10.5 million tonnes of methane in 2023³ . But the IEA statistics for coking coal do not include PCI coal, which is allocated to the steam (i.e thermal) coal category. If we assume that PCI coal constitutes 20% of all metallurgical coal, and that coking coal and PCI coal have approximately the same level of methane emissions per tonne, then we need to add 20% to the IEA figure for coking coal, giving an estimate for the annual methane emissions for all metallurgical coal of 12.6Mt.

What about charcoal? Statisistics for the global consumption of charcoal for steel making are sparse, as are estimates for the methane emissions associated with that production. An IEA report from 2013 estimated that 5 Mt of charcoal was used for steelmaking, mainly in Brazil⁴. A 2016 thesis study referenced a much higher figure of 12 Mt for the consumption of charcoal for steelmaking in Brazil⁵. Estimates for the methane emissions of charcoal making vary quite widely, depending on the technology and efficiency of the production process, but a figure of 25 kg of methane emitted per tonne of production seems to be a reasonable estimate for Brazilian production^6,7 . Using the lower, IEA figure of 5Mt for charcoal use for steelmaking, that gives an estimate of 0.1 Mt of emitted methane.

As for natural gas, based on work by L. D. Danny Harvey⁸ the steel sector consumed an average of about 2.49 EJ of energy from natural gas between 2016 and 2020. IEA gives a figure of 138.7 EJ for all natural gas supply in 2019⁹, implying that the steel sector consumed around 1.8% of total global production. According to the IEA Methane Tracker, the natural gas supply chain as a whole is responsible for emitting about 30 Mt of methane into the atmosphere each year. Pro rata, that would make the steel sector responsible for another 0.5 Mt of methane.

And finally, we can consider the methane emissions associated with the generation of electricity. IEA’s Methane Tracker estimates the methane emissions associated with global electricity production at 115 Mt per year. Global generation of electricity was about 25,065 TWh in 2019¹⁰, and the steel sector’s consumption of electricity between 2016 and 2020 was estimated to average 1,267 TWh¹¹. Pro rata, that would make the sector responsible for around 5.1 Mt of methane¹².

Material	Scope (for steelmaking)	Steel sector consumption (year)	Associated methane emissions
Metallurgical coal	Scope 3, Category 1	1,1 Mt (2023)	12.6 Mt (2023)
Charcoal	Scope 3, Category 1	5 Mt (2013)	0.1 Mt (2013)
Natural gas – DRI, etc	Scope 3, Category 1	2.49 EJ (2019)	0.5 Mt (2019)
Imported electricity	Scope 2/ Scope 3, Category 3	1,267 TWh (2019)	5.1 Mt (2019)
Total			18.3 Mt

Table 1. Estimated steel sector methane emissions for 2022

Table 1 summarises these values, giving an overall estimate of 18.3 Mt of methane emitted each year due to steelmaking.

If this is at least in the right ball park, how significant is it?

18.3 Mt of methane doesn’t seem like much compared to the steel sector’s annual emissions of 3,700 Mt of CO₂ (see ‘6%, 7%, 8%, 9%, 10%, 11%…’).

The problem is that methane is a far more powerful greenhouse gas than carbon dioxide.

But how much more powerful? How to compare steel’s methane footprint with its carbon dioxide footprint? And are there any other greenhouse gases we need to consider?

I’ve tried to address these questions in the next post: ‘Steel’s GHG footprints’…

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1. The terms ‘coking coal’ and ‘metallurgical coal’ are often used interchangably, however metallurgical coal includes PCI coal, whereas coking coal does not. PCI coal is typically classified as a form of ‘thermal’ or ‘steam’ coal in trade statistics, rather than as coking coal. This can be confusing. ↩︎
2. Coal 2023: Analysis and forecast to 2026. IEA (2023) ↩︎
3. IEA Methane Tracker, data updated March 2024 ↩︎
4. Large Industrial Users of Energy Biomass, IEA (2013) ↩︎
5. Silva (2016) Utilização de moinha de biorredutor e pneu inservível na produção de coque metalúrgico ↩︎
6. Sparrevik et al (2015) Emissions of gases and particles from charcoal/biochar production in rural areas using medium-sized traditional and improved “retort” kilns ↩︎
7. Pennise et al (2001) Emissions of greenhouse gases and other airbone pollutants from charcoal making in Kenya and Brazil ↩︎
8. Harvey (2024) A bottom-up assessment of recent (2016–20) energy use by the global iron and steel industry constrained to match a top-down (International Energy Agency) assessment  ↩︎
9. IEA Data and Statistics ↩︎
10. IEA Data and Statistics ↩︎
11. Electricity consumption estimated by Harvey (2024) as 4.56 EJ/year ↩︎
12. Steelmakers commonly use IEA grid emission factors to determine their Scope 2 emissions. Until 2023 these grid emission factors excluded all emissions upstream of power generation. In 2023 IEA started to provide additional data, including these upstream emissions. In future, therefore, it should be possible for steelmakers to incorporate these additional data, either by using these inclusive Scope 2 emission factors, or by including these upstream emissions separately as Scope 3 category 3 emissions. ↩︎