According to the International Energy Agency (IEA), the industrial sector accounted for a quarter of direct global energy system emissions in 2022. Reducing these emissions is urgent if the world is to limit global warming and reach net zero goals. Most importantly, under the Paris agreement, countries agreed to limit greenhouse gas emissions so that the long-term average temperature increase is limited to 1.5 °C above the pre-industrial (1850-1900) average. The IEA notes that to get on track with 2050 emissions targets, industrial emissions must decrease by 43% by 2030, compared to 2019 emissions, and continue declining thereafter.

As decarbonization technologies such as solar panels and batteries have matured, scientists are now turning their attention to industrial decarbonization. Since industrial facilities have an average lifespan of 20 years, it’s critical that facilities installed from 2030 onward must be non-emitting, and that means industries need technological solutions now. We analyzed the CAS Content Collection^TM, the largest human-curated repository of scientific information, and found a sharp uptick in publications relating to decarbonization since 2019 (see Figure 1).

Growth in journal publications has been notable, suggesting that research is flourishing while commercialization may still be a few years away. Decarbonizing heavy industries like steel and cement production has proven challenging since these processes use extreme heat generated by fossil fuels to drive various production processes and reactions. Replacing fossil-fuel-based processes has largely been technologically and economically infeasible.

However, there is no time to lose as the world continues to break temperature records, including surpassing 1.5 °C for the first time in 2024, and experiences worsening storms, droughts, and wildfires. To help sustainability efforts, we examine five major pathways to industrial decarbonization that are now benefiting from better technologies and wider applications.

5 pathways to successful industrial decarbonization

1. Electrification: Direct fuel combustion is responsible for 73% of global industrial energy usage, while only 27% is from electricity. There is ample opportunity to electrify more industrial processes, just as transportation and heating have increasingly electrified. To make meaningful progress on emissions reductions, however, electrical sources used for industrial processes must be renewable, like wind and solar.

2. Energy efficiency: Industrial energy efficiency is mostly focused on procuring more efficient equipment, but designing integrated systems based on energy efficiency could yield up to 90% energy savings. Major considerations include steam systems and heat recovery, since these account for extensive industrial energy usage. For example, the use of oxygen-enriched air to react with fuel can ensure complete combustion and higher concentrations of CO₂ in the exhaust gases, which can then be captured before being emitted into the atmosphere.

3. Carbon capture and storage: Industrial processes like cement production use high temperatures, which are achieved with fossil fuels easily and cheaply. It has been difficult to reach these temperatures and match current methods with decarbonized energy sources. In these situations where using fossil fuels is the only viable option, industries can use carbon capture and storage (CCS), where captured CO₂ is liquified and geologically sequestered deep underground. In certain cases, captured CO₂ can be used as feedstock in chemical production.  

The global capture rate is predicted to reach between 2-12 GtCO₂/year with most of this amount captured by industries. Interest in CCS has been growing recently with over 700 projects in various stages of development around the world, but this strategy will need to be accelerated and scaled up to meet net zero goals.

4. Green fuels: Shifting to emissions-free fuels will be crucial for industrial decarbonization. These can include hydrogen, which releases no emissions when burned as a fossil fuel replacement but can be challenging to produce in a sustainable manner .  

Currently, most hydrogen is produced by methane steam reforming, but this is an emissions-intensive process. To decarbonize it, industries can either use CCS or pursue green hydrogen. This is achieved by using electricity generated by renewable sources to split water molecules into oxygen and hydrogen. The hydrogen can then be stored for future use, either as a fuel or a feedstock for green ammonia.  

Biofuels can also be used in place of fossil fuels, for example, in aviation fuel, or as a feedstock for various chemicals. These often are derived from biomass, typically agricultural waste, wood, and other organic wastes.

5. Recycling: Recycling is expected to play a major role in decreasing the world’s demand for raw materials, particularly in the steel, aluminum, and plastics industries. Metal recycling rates generally reach over 50%, but it was estimated in 2022 that just 9% of global plastics were recycled. There is an urgent need for technological innovations to improve plastics recycling processes and expand both the collection and usage of recycled materials.

Decarbonizing the three highest-emitting industries

Not all industries produce the same amount of greenhouse gas (GHG) emissions. As seen in Figure 2, the three highest-emitting industries are steel/iron, chemicals/plastics, and cement. Each of these industries can benefit from the various paths to decarbonization, and as technologies become commercially available, they will also be more economically viable. Though emissions from aluminum are currently low, its use is poised to grow due to the need of lightweight materials to improve energy efficiency (ref).

1. Steel/Iron: Electrification, CCS, green fuels. The steel industry accounts for 7% of global GHG emissions. The most used method for steel production is a blast furnace (BF) or basic oxygen furnace (BOF). Iron ore is reduced by heating it with coke (purified coal) in a BF. Further modification of the carbon content and alloying of the steel take place in a BOF. Up to 30% of recycled scrap steel (secondary steel) is also added in the BOF to limit the need for raw iron ore.  The average emissions from the BF/BOF process ranges from 1.8-2.8 tons per ton of steel.  Coal combustion used in the BF/BOF, coke used for reduction, and carburization are the major sources of CO₂ emissions.

The IEA estimates that to achieve net zero emissions by 2050, CO₂ emissions from the steel industry must decrease to 600 kg per ton of steel. Strategies to meet this goal include decreasing the use of BF from the current 70% to 30%, doubling the use of electric arc furnaces (EAFs) for scrap steel recycling, carbon capture, and using hydrogen as clean fuel. Other processes are being explored to reduce emissions from the steel industry, such as EAFs in place of BOFs and the HIsarna process to eliminate high-emissions steps in the production process. Using biofuels or hydrogen — either CCS or green hydrogen— to power BFs/BOFs is also a workable strategy:

2. Chemicals/plastics: Electrification, energy efficiency, CCS, green fuels, and recycling. Petrochemicals account for 5% of global GHG emissions and 18% of industrial CO₂ emissions. More than 85% of emissions from chemical production are emitted when fuels are combusted to provide heat or steam, since many of the production processes require high temperatures. The other major sources of emissions are the generation of hydrogen from fossil fuels for chemical synthesis, production of chemical raw materials from fossil fuels, and the energy needed for the distillation and filtration steps.

To meet net-zero targets, the industry must reduce emissions by 30-45% from current levels. Out of the total reduction in emissions needed, process optimization and energy efficiency improvements, such as better separation methods and heat management, are expected to contribute to 25%. The replacement of coal with natural gas or electricity can contribute to another 25%. Plastics recycling and carbon capture are expected to contribute 15% and 35% reduction in emissions, respectively.

3. Cement: Energy efficiency, CCS, and green fuels. The cement industry releases 8-9% of global total of GHG emissions, consumes 2-3% of global energy demand, and accounts for 9% of industrial water withdrawals. The production of 1 kg of ordinary Portland cement releases about 0.86 kg of CO₂ on average. Cement is the most-used material in the world, so even though the CO₂ emitted per kg of cement production is lower than other materials, its high production volumes make cement a vital industry to decarbonize.  

Cement production involves a process called kilning, which needs high temperatures (~1500 °C) to produce the base materials, called “clinker,” which react with water to form concrete. The two major causes of CO₂ emissions during cement manufacturing are the emissions from burning fuels to reach the high temperatures required in the kilning process and the CO₂ emissions from the breakdown of CaCO₃ (limestone) to CaO (lime), a key ingredient of the clinker. Reducing the amount of heating necessary to the process will be important to reducing emissions, so greater energy efficiency, capturing unavoidable CO₂ emissions, and shifting to green fuels will be necessary.  

New patents can drive decarbonization innovation

Although journal publications showed the largest increase in the CAS Content Collection, there have also been many important patented advances that could bring key innovations to commercial usage. We developed a landscape of patents using the international patent classification codes (IPC) to further analyze recent activity (see Figure 3). The patents related to decarbonization belong to two major sections — chemistry/metallurgy and operations/transport. The operations section mostly contains processes related to carbon capture using chemicals and sorbents. The chemistry/metallurgy section contains patents related to the manufacturing of steel, cement, hydrogen, and alternative fuels.

Researchers have also explored what a timeline to industrial decarbonization would look like (see Figure 4). Various countries may achieve these goals earlier than the dates specified, but this framework can be a general guide for policymakers, industry leaders, and scientists.

Decarbonizing heavy industry has proceeded slowly for many reasons — most notably because the right technologies either haven’t existed or been economical. However, increased research in the past few years is changing this situation, such as large-scale green hydrogen facilities and the growth of renewable energy sources to power electrification. The challenges are still considerable, but momentum is growing, and industrial processes are poised to wind down their emissions.