Industry: the IPCC’s solutions for decarbonizing it

We present here the chapter on industry from the 3rd working group of the 6th IPCC report.

The industrial sector includes: mineral extraction, manufacturing, construction [error?] and waste management. This chapter focuses on heavy industry, which accounts for 65% of the sector’s greenhouse gas emissions.

Getting it to zero emissions will require not only using the “traditional toolbox of energy and process efficiency, fuel switching, electrification and energy decarbonization”, but supplementing it with other measures: “demand management and efficiency, circular economy, non-fossil feedstocks, carbon capture and utilization (CCU) and carbon capture and storage (CCS).” (p.1165)

Trends and data in industrial development

Industrial emissions have been driven up by rising GDP and held back by improvements in the energy efficiency of processes. Recycling has also made it possible to limit the need for certain “virgin” materials, whose extraction and initial refining consume a lot of energy.

When we look at the quantities of materials “stored” in things (=buildings, machines…), the bulk is obviously made up of building materials. Mineral building materials are mainly (94.6%) minerals (concrete, asphalt, bricks, aggregates and glass), with cement alone accounting for 43.5% of the total weight. There are also metals (3.5%) and wood (1.4%). In 2018, there would have been 478Gt of concrete, containing 88Gt of cement. More broadly, iron/steel is estimated to represent 25 to 35Gt, plastics 2.5-3.2Gt and aluminum 1.1Gt. (p.1169)

The extraction of basic materials has increased considerably since 1990. In 2019, it was more than 3.5 times higher for aluminum, steel and plastic, and almost 2.5 times higher for steel, while the population is only 1.5 times higher.

This increase is set to continue, and the global stock of materials in use could multiply by a factor of 2.2-2.7 by 2050, reaching between 2215 and 2720Gt. 140 to 200Gt of material could be extracted every year by 2060. This increase is mainly concentrated in emerging countries. In particular, it is estimated that India could increase its steel consumption by a factor of 4 by 2050. Conversely, Western countries tend to have a stable stock of materials.

In fact, certain materials, such as steel, cement, aluminum and copper, have reached saturation levels. (p. 1177)

Recycling of metals is higher than for other materials, exceeding 50% for 13 metals and between 25% and 50% for 10 others. Nevertheless, even with a recycling rate close to 85%, recycled steel only accounts for 35-38% of total production, ranging from 22% in China to 69% in the USA. For paper, recycling is relatively high: over 50% in 2014-18. For plastics, on the other hand, it’s only 9-10%.

Industry is the main energy consumer, directly consuming 40% of the total.

Energy intensity nevertheless fell by 12% between 2010 and 2018. (p.1171) Greenhouse gas emissions come from :

  • industrial fuel (7.1 GtCO2eq)
  • indirectly from electricity and heat production (5.9 GtCO2eq)
  • industrial processes themselves (4.5 GtCO2eq)
  • product use (?) (0.2 GtCO2eq)
  • waste (2.3 GtCO2eq) (p.1172)

Overall, industrial emissions represent 14.1 GtCO2eq of direct emissions (2’%) and 20 GtCO2eq if indirect emissions are added (34% of the total).

The IPCC points out that taking into account “embodied” emissions in international trade increases industrial emissions by 130% for the US, 50 for the EU and >200% for the UK. On the contrary, for China and Russia, it reduces them by 33%… He points out that “exports from countries with lower carbon intensities can lead to overall lower emissions than if production took place in countries with high carbon intensities”. (p.1176)

The main points

“Modeling suggests that material stocks per capita are saturating in developed countries and decoupling from GDP. “p.1177

  • Limiting demand: demand for materials is one of the main drivers of energy consumption in the industrial sector. In general, improving material efficiency contributes to this, since it’s a question of doing more with less. [The passage is unclear: it refers to the saturation effect of the main materials (cement, steel, etc.) in circulation, but this is not the case for plastics. This saturation would promote material efficiency (?). Achieving climate targets will require the construction of a great deal of infrastructure. Overall, they don’t describe any solutions, passing the buck to material efficiency and circular design]
  • Material Efficiency (ME) means offering the same service with fewer materials. This may involve making products lighter, optimizing their durability and intensity of use, following circular economy principles, or using more efficient design processes. It should be noted that certain strategies can have short-term effects (e.g. optimizing design) or long-term effects (e.g. service life, recyclability).
  • Circular economy and industrial waste. The circular economy consists in closing the life cycle of products, using their waste to make new products. [This applies to the management of both material and immaterial waste, such as waste heat] It can be applied on several scales: micro (a single company), meso (an industrial park) and macro (a larger scale).
  • Energy efficiency. For example, this would involve reusing waste heat, representing a potential gain of 300TWh per year, of which 50% is below 200°C and 25% above 500°C. Steel industry strategies could already save 1.8 GJ per tonne of steel. (p.1181) Waste heat to power systems could also be used. Smart Energy Management systems and, more broadly, Industry 4.0 could improve the overall energy efficiency of industry.
  • Electrification, hydrogen and fuel switching. This involves moving away from coal (0.09 tCO2/GJ), petroleum products (0.07 tCO2/GJ) and gas (0.05 tCO2/GJ) towards less polluting fuels, or replacing them with electricity, which we know how to produce using low-carbon processes. Depending on the scenario, this electrification could multiply electricity consumption several times over. For example, while the steel industry currently consumes 75 TWh of electricity in Europe, this could rise to between 214 and 355 TWh.
    • For some processes, electrification will not be possible. Hydrogen could be the answer. More broadly speaking, this field is important in two ways: by decarbonizing existing uses (e.g. ammonia production) and with new applications, such as the creation of industrial heat, energy storage and so on. Its production represented 830 MtCO in 2015.
  • CCS, CCU, sources of carbon and materials. Carbon capture (at the end of the process) varies widely from one industry to another, notably due to the variety of volumes and densities of gases to be reprocessed. Carbon is a central atom in industry, and is present in many fuels, organic compounds and materials. CCU poses the problem of the subsequent release of captured carbon. (p.1185)

P.1188 presents a table summarizing how the various players (engineering companies, manufacturers, international organizations, public organizations and civil society) can act in each of these areas.

Strategies by sector

Strategies vary according to each industrial sector.

The steel industry

In 2020, 40% of steel will be used for structures, 20% for industrial equipment, 18% for consumer products, 13% for infrastructure and 10% for vehicles. Crude steel production increased by 41% between 2008 and 2020, with emissions ranging from 3.7 to 4.1 GtCO2-eq. It is divided into two routes: one based on iron ore refining and the other on recycling. The former mainly uses the BF-BOF (basic oxygen furnace route) process, and the latter the EAF (electric arc furnace) process. In 2019, the former accounted for 73% of production and the latter for 26%. However, the first route can also use the EAF process via “direct reduction” (DRI). This accounts for 5.6% of the total.

The BF-BOF process is the most polluting, using CO2 and very high heat to reduce the iron. However, it is estimated that its energy efficiency can be improved by 15%. Carbon capture is difficult to implement on existing plants beyond 50% capture. A new process, “HIsarna”, revisits this process, making it more compatible with carbon capture. It is also possible to add hydrogen to coke (= carbon) for iron reduction, reducing the need for the latter and thus overall emissions.

The best solution is to encourage the recycling of existing steel, but this is already being promoted and developed.

Another option is direct iron reduction. This could be based on syngas (a mixture of hydrogen and carbon monoxide) produced from methane, or on the use of hydrogen. It would also be possible to reduce iron by electrolysis. This can take place in an aqueous solution, as in the Siderwin project, or in a solid oxide.

Beyond these avenues for decarbonizing production, an increase in material efficiency and intensity of use would make it possible to reduce demand.


The cement sector is seen as one where decarbonization options are particularly limited.

The sector emitted between 2.1 and 2.5 GtCO2-eq in 2019, 40% of which comes from heat generation [a very high-temperature flame is required] and 60% from the chemical reaction produced itself, i.e. the extraction of carbon from calcium carbonate. This occurs when the rock is transformed into “clinker”.

There are several ways of influencing demand. Firstly, by improving the mix when designing concrete. In addition, builders (engineers and contractors) tend to use cement (rich in clinker), even when they could use other materials. This replacement could reduce cement use by 20 to 30%.

To decarbonize production itself, carbon capture could not be avoided. Emissions from heat production could be reduced by using biofuels, biomass or biogas.

Alternatives to clinker are being sought, including the use of carbonatable calcium silicate-based clinker and magnesium oxide-based cements. Nevertheless, the changes would involve extensive modifications to the construction sector, from practitioner training to regulatory codes.

The chemical industry

The chemical industry includes plastics, fertilizers, solvents, pharmaceuticals and food additives. Emissions were between 1.1 and 1.7 GtCO2-eq in 2019, mainly due to the production of ammonia, methanol, olefins and chlorine. The former alone accounts for 30% of these emissions, which could be reduced by decarbonized hydrogen or CCS.

[To be reread, many details to be understood]

Plastic production now stands at over 400 million tonnes. Each tonne would produce on average (which varies according to the raw material used, the plastic produced and the energy system) 1.8 tCO2-eq per tonne in the USA and 2.3 CO2-eq in Europe.

Aluminum and other non-ferrous metals

Demand for aluminum was estimated at 100 Mt/year in 2020, of which 14% from industrial scrap and 20% from recycling. Primary production has risen from 20Mt in 1995 to over 66Mt in 2020, and could reach 139Mt/year by 2060, according to the OECD. Its production process involves first extracting aluminum oxide from bauxite ore using Bayer’s hydrometallurgical process. The oxide is then reduced by the Hall-Héroult process, which uses large quantities of electricity: 14 to 15 MWh per tonne on average.

Part of the process emissions, around 1.5tCO2eq per tonne produced, comes from the degradation of the graphite electrodes, which combine with the oxygen in the water. In addition, perfluorocarbons can be emitted if the process is poorly controlled, which would represent 2tCO2eq per tonne produced.

Recycling is much simpler, requiring 20 times less energy. Increasing the current rate (20-25%) is one interesting avenue.

The strategy for decarbonizing aluminum and other non-ferrous metals is similar: improve material efficiency, recycling and develop extraction processes based on electricity as an alternative to current pyrometallurgy.

Pulp and paper

Assuming its energy is biobased, the pulp and paper industry emits little “net” CO2, but does emit 700 to 800Mt of CO2 that could be recovered through carbon capture.


The potential of each solution is presented and summarized in a comprehensive and extremely interesting table, p.1197-1198.

The authors discuss the different trajectories on pages 1199-1207.

They then discuss existing industrial infrastructures and their propensity to “block” change, the regulatory context, and then the other benefits, in terms of sustainable development goals, of the strategies presented. Finally, they discuss regulatory approaches and strategies.

These sections are too complex to go into detail and summarize at present. I’ll come back to them later.

An important quote:

A very large and important uncertainty is the availability of biomass for deep decarbonisation pathways due to competition for biomass feedstock with other priorities and the extent to which electrification can reduce the demand for bioenergy in the industry, transport and energy sectors.IPCC, WGIII, p.1223