Washed PKS for Decarbonization of Iron and Steel Plants

The steel industry contributes 8% of global CO2 emissions, with each ton of steel produced producing an average of 1.85 tons of CO2 emissions. Compared to iron ore mining, iron and steel production contributes significantly more to CO2 emissions. Decarbonization efforts in the steel industry begin with the use of renewable energy for smelting. Biomass-based fuels, such as charcoal, which has a high carbon value, can replace the use of coke derived from coal. The use of hydrogen from renewable energy sources is the ultimate decarbonization target for the steel industry.

Currently, the steel industry largely uses coal as an energy source or reducing agent. This coal is processed into coke and used in blast furnaces. It is estimated that approximately 70% of global steel production uses the blast furnace or BF-BO process, and in China, over 90% of steel production uses the BF-BOF process. To reduce carbon intensity, natural gas is used as the fuel. The use of natural gas as a gaseous fuel also acts as a transition medium and, because it is derived from fossil fuels, is also a carbon-positive fuel.

Nearly all CO2 emissions in the steel production sector come from blast furnaces (BFs), which refine iron ore into crude iron or pig iron. The challenge is significant: there are approximately 1,850 steel mills worldwide, with approximately 1,000 using blast furnaces, producing approximately 1.5 billion tons of pig iron annually.

The use of charcoal in a blast furnace not only reduces carbon dioxide (CO2) emissions but also sulfur dioxide (SO2) emissions due to its very low sulfur content (approximately 100 times lower) than coke. Likewise, the use of limestone is reduced, thereby automatically reducing slag production. This also makes the blast furnace's operation acidic.

The use of biomass-based carbon fuel (biocarbon) in the form of charcoal has a better climate impact because it is carbon-neutral. Furthermore, technically, because it is a solid fuel, similar to coke derived from coal, it requires little or no changes or modifications to the smelting furnace. However, the availability of high-quality charcoal, large volumes, and a continuous supply remain major constraints.

This makes the use of charcoal to replace coal-based coke in blast furnaces crucial. Charcoal, derived from biomass, is a renewable, sustainable material used as a reducing agent or fuel in blast furnaces. The chemical reaction separates oxygen atoms from iron atoms, emitting CO2. This converts iron ore (Fe2O3) into crude (pig) iron.

However, the difference lies in the fact that the carbon source used as a reducing agent or fuel in a blast furnace comes from renewable and sustainable sources, making it a carbon-neutral process. Conversely, using coke from coal, as it comes from a fossil fuel, is a carbon-positive process. Similarly, using natural gas as a carbon source for reducing agents or fuel in a blast furnace, although it is said to have lower carbon intensity, is also considered a carbon-neutral process.

The use of charcoal or biocarbon materials for metallurgy or steelmaking has actually been commonplace for some time. In the early 1900s, global charcoal production reached its peak, exceeding 500,000 tons. In the 1940s, charcoal production declined to nearly half its early 1900s levels due to the replacement of other carbon materials, such as coke from coal, in the manufacture of steel and other metals.

Charcoal is a fuel and reducing agent derived from biomass that has significant potential for use during this transition phase. Palm kernel shells (PKS) are a potential biomass raw material for charcoal production. Palm kernel shells (PKS) are available in the millions of tons, ensuring a reliable supply. Charcoal, a product of biomass carbonization or pyrolysis, has a high calorific value, high fixed carbon content, and stability. However, another factor, ash chemistry, influences the quality of the resulting steel. This is somewhat similar to the ash chemistry of wood pellets from calliandra or gliricidia energy plantations.

When used as a reducing agent in blast furnaces, charcoal must have a low phosphorus content, while wood pellets from calliandra or gliricidia energy plantations must have low potassium, sodium, and chlorine content. The potassium, sodium, and chlorine content of wood pellets affects the quality of the wood pellets and their use in power generation. Pulverized combustion power plants, widely used worldwide, will reject wood pellets with this quality. Similarly, blast furnaces will reject charcoal with a high phosphorus content.

To achieve this quality, low-phosphorus content, the palm kernel shells (PKS) must first be washed. After washing, the phosphorus content decreases, and they are then dried and pyrolyzed, or carbonized, to produce palm kernel shell charcoal (PKSC). The same applies to wood pellets. The only difference is that wood pellet production doesn't involve pyrolysis or carbonization; instead, after drying and achieving the desired particle size, the pellets undergo biomass densification in a pelletizer.

Steel production requires an average of 6,000 MJ of energy per ton (equivalent to 50 kg of hydrogen) or 200 kg of charcoal, and requires approximately 600-800 kg of woody biomass as raw material. With a calorific value nearly identical to woody biomass, this is equivalent to using palm oil mills (PKS), which are plantation or agro-industrial waste.

Meanwhile, demand for low-carbon steel is growing rapidly as steel industries and governments worldwide commit to reducing carbon emissions from fossil fuels. The use of charcoal or biocarbon in blast furnaces is a key component of low-carbon steel production, as 100% of the steel is not yet produced using renewable energy. 

Biochar-Based DRI / Sponge Iron Production

In the steel industry, carbon neutral production will be achieved when iron and steel production use 100% renewable energy. Electric arc furnaces (EAFs) can be used as long as the electricity is generated from renewable energy sources. However, EAFs, which still use electricity from fossil fuels, can be a transitional medium before 100% carbon neutral production due to their lower CO2 emissions compared to blast furnaces (BF) using coke from coal. The raw materials processed with EAFs are steel scrap and direct reduced iron (DRI/sponge iron). Steel scrap or DRI (sponge iron) is directly fed into the electric arc furnace (EAF) for steelmaking, resulting in lower carbon emissions compared to the blast furnace (BF) method. CO2 emissions from the blast furnace (BF) are approximately 2.33 tons for each ton of crude iron/pig iron, while with the EAF, they are only approximately 0.66 tons for each ton of crude steel.

Currently, approximately 80% of steel scrap is recycled using EAFs. Globally, EAFs account for approximately 22% of steel production (based on scrap and sponge iron). India is the largest producer of sponge iron, or DRI. Other major producers include Iran, Russia, Mexico, and Saudi Arabia. In 2023, India produced 49.3 million tons, while Iran produced 33.4 million tons. Global sponge iron, or DRI, production reached 135.5 million tons in 2023, while pig iron reached nearly 1.5 billion tons.

And the fact is that currently, to achieve the goal of producing carbon neutral steel is still far away because the construction of blast furnaces - basic oxygen furnaces (BF -BOF) is still being carried out a lot, which should be EAF (Electric Arc Furnace) or currently only about 30% globally the iron and steel industry uses this EAF. The construction of new blast furnaces does tend to increase, in fact, by mid-2024, around 207 million tons per year of new production has been announced and around 100 million tons per year is under construction.

Sponge iron, or DRI, is produced from iron ore that has been processed to remove oxygen, resulting in a porous, sponge-like material. The process for producing DRI is called direct reduction. Direct reduction processes can be roughly divided into two categories: gas-based and coal-based. Just as coal can be used, so charcoal (biochar) can be used as the carbon source. The difference is that charcoal (biochar) is derived from wood or biomass, which are renewable resources. The process typically involves a rotary kiln where iron ore and coal or charcoal (biochar) are fed together, and the reduction reaction occurs in the solid state. India is a major producer of coal-based DRI, with production increasing substantially in recent years, as shown in the map below. Other major producers of DRI, or sponge iron, generally use natural gas-based processes.

The availability of biochar that meets specifications and sufficient volume, as well as its sustainable supply, is needed to substitute coal in DRI production. Therefore, on the upstream side, the availability of biomass raw materials from forestry waste, wood processing, agricultural waste, and agro-industrial waste is crucial for the sustainability of biochar production, including the establishment of energy plantations for this purpose. In addition to replacing the reductant or fuel from coal to charcoal (biochar) in DRI or sponge iron production, efforts to reduce carbon emissions in steel production on the DRI-EAF route also include replacing the EAF electrode from fossil-based synthetic graphite to biochar-based biographite. For more details, read here. 

Decarbonization of the Iron and Steel Industry Part 3: from Low Carbon Production to Carbon Neutral Production

When the decarbonization target must be achieved according to the specified deadline, various efforts will also be made, including through a transition phase. The transition phase in the iron and steel industry is from low carbon production to neutral carbon production. There are a number of factors that influence towards this goal, especially the readiness of the market to buy iron and steel products produced from the production process and also the readiness of fuel and reducing agents for blast furnaces in the iron and steel industry. Charcoal is a fuel and reducing agent derived from biomass which has great potential for use in this transition phase. Charcoal as a carbonization or biomass pyrolysis product has a high calorific value, high fixed carbon and is stable.

Meanwhile, carbon neutral production conditions will be achieved when iron and steel production in the industry uses 100% renewable energy. The use of an electric furnace (EAF/Electric Arc Furnace) can be done as long as the electricity is produced from renewable energy sources. Likewise, the use of hydrogen fuel in blast furnaces (with electrical energy for plant operations also from renewable energy) is also able to achieve carbon neutral production conditions, and even the use of hydrogen fuel in blast furnaces is considered to be the ultimate goal in decarbonization of the iron and steel industry. With the target of achieving net zero emissions by 2050 and the average service life of blast furnaces being 20 years, the iron and steel industry's efforts to achieve the target must be well formulated and programmed. Even if efforts to replace blast furnaces do not follow this target time, it will put the achievement of net zero emissions by 2050 in jeopardy.

In fact, currently it is still far from achieving this goal because the construction of blast furnaces - basic oxygen furnaces (BF -BOF) is still being carried out, which should be EAF (Electric Arc Furnace) or currently only around 30% of the global iron and steel industry uses this EAF. Even the International Energy Association (IEA) highlighted this critical issue to achieve the Paris Agreement's net-zero target by 2050. CO2 intensity in this industry has only slightly decreased so that the use of renewable energy becomes increasingly important and accelerated.

A case example is the Japanese iron and steel industry. As a steel producer of more than 85 million tons per year with main use in domestic construction projects and automotive manufacturing and with more than 25% (more than 21 million tons) being exported, the Japanese steel industry has a significant influence on the global market. The dominant dependence on coal is the main problem of decarbonization and moreover, Japan is also the third largest coal importer in the world. Furthermore, decarbonization in Japan is considered inadequate because the Japanese steel industry lags behind other major world steel producers. Japan is a G7 country that does not implement a coal phaseout period.

Nippon Steel has even been labeled a climate laggard or slow to respond to the climate crisis in the Asian region. This is because the decarbonization strategy is inadequate or not in accordance with the IPCC's 1.5°C warming pathway or the IEA's net-zero pathways. This condition threatens national and global decarbonization targets and puts Japan's steel industry at risk. Meanwhile demand for low-carbon steel is increasing rapidly because steel industries and governments around the world are committed to reducing carbon emissions from fossil fuels. The Japanese steel industry needs to immediately decarbonize to remain competitive in the global market. Decarbonizing by investing in low-carbon steel production will address these risks and can position the Japanese steel industry as a leader in the green transition of the global steel industry.

 

Regarding the issue of fuel or renewable energy sources, biomass has a strategic position and role, namely in blast furnace operations, charcoal, which is a product of biomass carbonization, is used as a fuel and reducing agent, while in electricity production for iron and steel plant operations, biomass can be used as a renewable energy sources or biomass power plants. This is why the availability of biomass is very important so that the creation of energy plantations as a source of biomass is very necessary. Not only is the plantation a source of energy, it can also play a role in the production of food and feed, both of which are very beneficial for human life. And of course optimizing the use of the plantation by utilizing all parts of the tree (whole tree utilization) also provides maximum financial / economic benefits and with good management it will also provide benefits or improve the environment. And ideally by 2050 the steel industries will use electric arc furnaces / EAF, 100% hydrogen in blast furnaces and even a combination of carbon capture, to achieve net zero emissions in 2050 or even negative emissions so it is very good for the climate.