Reducing Industrial Emissions: Steel and Cement

Innovations and startups creating a greener future in steel and cement

Summary

• Steel and cement alone contribute to 15% of global emissions.

  • 7% comes from steel production, and 8% comes from cement production.

• For $278 billion, steel could be made with zero carbon emissions by 2050, with green hydrogen playing a significant role in this process.

• Startups like Boston Metal, Blastr, and Green Steel are trying to reduce CO₂  emissions in the steel manufacturing process by replacing coke - a fuel used in the steel manufacturing process that’s created by heating coal in the absence of air and fossil fuels with renewable energy sources and green hydrogen.

• The best way to reduce greenhouse gas emissions from cement production is by replacing concrete with a polymer or other material so it isn’t produced at all. 

• Startups like CarbonCure, Geoprime Betolar, and Solidia are working to replace cement or concrete with lower CO₂ emitting substances.

Carbon Emissions from Steel

Direct CO₂ emissions from crude steel production are 1.4 tons per ton of steel, making it one of the largest carbon emitters globally, contributing ~7% of global emissions.

The country that produces the most steel is China (~1.875 billion per year), which leads to carbon emissions of 3.375 billion tons. The production-to-emissions ratio in China is higher because the majority of the steel they produce comes from the blast furnace method. With this method, iron ore is heated to 1500 degrees Celsius, and oxygen is blasted on liquid iron to remove impurities. Heating iron ore to such a high temperature is, of course, incredibly energy-intensive. 

More recently, manufacturers have discovered a secondary method, one that emits less CO₂. It’s called the electric arc furnace method (EAF), where the primary raw material in this process is steel scrap that’s heated in the electric arc furnace at 3500 degrees Celsius. Where emissions from the blast furnace process are 1.987 tonnes of CO₂ per ton of steel, the electric arc furnace process emits just 0.357 tonnes of CO₂ per ton, an 82% reduction in emissions. 

There are two reasons why the electric arc furnace method for steel production emits less CO₂ as compared to the blast furnace method:

1. Raw Material Used: Blast furnaces primarily use iron ore as a raw material, which must undergo a reduction process involving coke (made from coal) to extract the iron. This process emits a significant amount of carbon dioxide. Whereas EAFs use a substantial proportion of recycled steel (scrap) as a raw material, which doesn't require a reduction process and reduces the associated CO₂ emissions.

2. Energy Source: Blast furnaces require significant amounts of carbon-intensive energy sources such as coke and coal, which release large amounts of CO₂ when burned. Electric arc furnaces use electricity, which can come from renewable sources that reduce carbon emissions significantly. 

Carbon Emissions from Cement

According to the EPA, every metric ton of cement produced emits 0.776 tons of carbon dioxide. Due to the increasing demand for cement year over year, it’s becoming more difficult to reduce CO₂ emissions. 

Cement acts as the binder between aggregates (fine and coarse rocks) in the formation of concrete and is primarily produced via a dry process where several elements - limestone, shells, and chalk or marl are combined with shale, clay, slate, blast furnace slag, silica sand, and iron ore by heating. These ingredients are heated at high temperatures to form clinker and then cement.  During the clinker production stage in the kiln, limestone (calcium carbonate) is heated and breaks down to form lime (calcium oxide), releasing CO₂ in the process. This chemical reaction is referred to as calcination. Roughly 60% of emissions from cement production are due to this process.

CaCO₃ → CaO + CO₂

Reducing Carbon Emissions from Steel Production

1. Green Hydrogen Usage in Furnaces and Heating

By 2050, green hydrogen has the potential to become the cheapest fuel for steel products and capture 31% of the market share. BloombergNEF found that, with additional investments of $278 billion, steel could be made with zero carbon emissions by 2050, and green hydrogen will play a significant role in this process. Right now, a whopping 70% of steel is produced using coal-fired blast furnaces:

Direct reduced iron and electric arc furnace methods are the methods that use green hydrogen to manufacture steel, so the world needs many more of those types of plants. China, being the dominant player in the steel industry (57% of the world’s total steel production), will set the direction for the industry as a whole. Their current focus is on increasing recycling and energy efficiency before adopting new technologies like green hydrogen and carbon capture to strive toward net zero.

2. Blast Furnace/Blast Oxygen Furnace Efficiency Programs

BF/BOF efficiency programs can improve efficiency and decrease production losses by:

• Optimizing the BF burden mix through maximizing the iron content in raw materials, decreasing the usage of coal as a reductant.

• Replacing coke by introducing an alternative fuel into the furnace, such as natural gas, biomass, or hydrogen.

• Using Pulverized Coal Injection technique to replace coke. It’s a technique that involves grinding coal into a fine powder and then injecting it into the blast furnace. 

• Using coke oven gas in the BF as an energy source.

3. Biomass Reductants

Replacing fossil fuels with biomass reductants like heated and dried sugar, energy cane, or pyrolyzed eucalyptus can significantly reduce carbon emissions during steel production. However, the major challenge with using reductants is their availability. For example, the biomass reductants mentioned above are available in abundance in South America and Russia, but it’s tough to decarbonize the steel industry just by using reductants in Europe as it doesn't have reductants in abundance.

4. Carbon Capture and Storage

CCS involves capturing CO₂ emissions from large point sources like power plants and industrial facilities and transporting and storing the gas in underground geological formations. 

5. Increase Share of Scrap-Based EAFs

By increasing steel production by EAFs, producers can produce more environmentally friendly steel. However, the main challenge to scaling the EAF process is the availability of high-quality steel scrap and the need for abundant renewable electricity. Overcoming these challenges is critical because recycling via EAF is crucial in decarbonizing the steel industry.

Startups Decarbonizing Steel Production

1. Boston Metal

Boston Metal is trying to electrify the entire steel industry with direct, efficient, and modular solutions and decarbonizing the sector as soon as possible. The company has developed an electrical steel production process that eliminates the use of coal and instead uses direct electric current to separate chemical compounds into their constituent parts. The raw material used in their method of steel production is ferrous oxide (iron ore - Fe₂O₃) that reacts with an electron to split into iron and oxygen:

Fe₂O₃ + e^- → Fe + O₂

The benefit of this process is that it can also turn low-quality iron ore into high-quality molten iron, saving millions of dollars that manufacturers spend buying high-quality iron.

2. Blastr

Blastr Green Steel is taking a huge step towards zero carbon emissions in the steel industry by replacing coal and coke with hydrogen in the steel production process. Their mission is to challenge the status quo in the steel industry by developing integrated, decarbonized, and scalable value chains for ultra-low CO₂ steel production. They use a direct-reduction pellet plant to convert high-grade iron ore into steel.

3. H2 Green Steel

Situated in Boden, North Sweden, H2 Green Steel can produce steel with 95% less carbon emissions than the traditional method. Just like the companies mentioned above, H2 Green Steel replaces coal with hydrogen; water and heat are the only primary emissions. They aim to produce 5 million tons of steel annually by 2030 and avoid 0.3 billion tons of CO₂ emissions, about 1% of total annual emissions.

Reducing Carbon Emissions During Cement Production

1. Finding Clinker Alternatives

CO₂ emissions in cement manufacturing are directly proportional to the amount of clinker used. The more clinker produced during the process, the more carbon is emitted. So the first significant step to reduce emissions is to replace clinker with something that emits comparatively less or, in the best possible scenario - no carbon. 

Many cement producers have started using less polluting substitutes like natural and calcined pozzolans. Pozzolans are naturally occurring siliceous and aluminous materials that possess no cementitious value. But when finely divided in the presence of water, it reacts with calcium hydroxide at normal temperature. Other alternatives include industrial byproducts such as fly ash.

2. Alternative Fuel

A shift to less carbon-intensive alternative fuels, such as waste and biomass, for heating kilns (a furnace used to produce cement) could decrease direct CO₂ emissions from global cement production by 9% by 2050. However, the feasibility of this shift depends on the availability of alternative fuels and the development of local supply chains. 

3. Carbon Cured Concrete

This technology injects CO₂ captured during cement production and “locks in” CO₂ in the end product. The technique also helps accelerate the curing process. Low-carbon cement technologies can sequester up to 5% of CO₂, potentially up to 30% in the future. Sixty million tons of CO₂ per year are projected to be stored via carbon-cured concrete by 2050.

Startups Decarbonizing Cement Production

1. CarbonCure

CarbonCure creates carbon removal technologies to help the concrete industry build more efficient businesses and produce cleaner concrete. Their technology introduces recycled CO₂ into fresh concrete and reduces the carbon footprint without compromising quality. Once injected into the concrete, this CO₂ undergoes a chemical reaction and transforms into a mineral, improving the compressive strength of the concrete.

2. Geoprime Betolar

Geoprime is a sustainable and cement-free infrastructure solution for a range of concrete product applications. This concrete substitute emits 80% lower CO₂ and has the same toughness as concrete. Geoprime is made from geopolymer - an inorganic polymer that’s used to create new materials. 

Geoprime Betolar aims to use it in infrastructure projects, including paving blocks, poles, and construction blocks. R&D on Geoprime is still in the process of discovering more ways to use it as a replacement for concrete. 

3. Solidia

Solidia is a cement and concrete technology company offering green solutions that make using CO₂ to create superior and sustainable building materials easy and profitable. Solidia said their tech could eliminate a minimum of 1.5 gigatons of CO₂ annually.

The company provides two core technologies:

1. Sustainable Cement Manufacturing Technology: Can be produced in kilns but with less energy and reduces carbon emissions by 30-40%.

2. Sustainable Concrete Curing Technology: Curing concrete with CO₂ instead of water consumes 240 kgs of CO₂ permanently and saves ~3 trillion liters of water annually.

Wrapping Up

Industrial emissions, specifically steel and cement production, are major contributors to global CO₂ emissions. To reduce emissions in the steel industry, companies should increase the use of green hydrogen as an alternative fuel for coke and coal as much as possible. However, to reduce greenhouse gas emissions in cement production, the best way is to replace concrete with new innovative materials to avoid cement production altogether.

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