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 in the Steel Industry Part 2: Charcoal as Fuel and Reductant in Blast Furnace

Basically, the conditions in each steel industry vary so that the decarbonization process is also carried out using different and gradual routes to achieve net zero emission conditions. The conditions of each steel industry have a unique configuration of production technology, raw materials and energy sources, capacity and yield, regulatory requirements and so on. To achieve Net-zero by 2050, a number of things need to be done, such as efficient use of raw materials, increasing the portion of reuse and recycling, retrofit and advanced technology, and especially efforts to use renewable energy sources as fuel and reductant in the iron and steel industry. But the fact is that 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, but there are transition efforts that can be made as described below. The transition is influenced by market demand, policy interventions, and incentives given to producers to reduce emissions in steel production.

To create policies related to this transition, providing incentives to reduce emissions for producers and creating market demand for "green steel", a clear definition is needed between low emissions vs. almost zero emissions (near zero emissions) vs zero emissions (net-zero emissions). It is estimated that in 2021 CO2 gas emissions from this industry will be 3.8 Gt globally (this has not even taken into account methane emissions from coal mining). Meanwhile, for Net-zero 2050 conditions, direct CO2 emissions from the global iron and steel industry must be reduced to 1.8 Gt CO2 in 2030 and 0.2 Gt in 2050. It seems that a lot of hard work is still needed to achieve this target, even with the current conditions. Many people are pessimistic.

One use of biomass as a carbon neutral fuel in the iron and steel industry is the use of charcoal as a fuel and reductant. Biomass such as wood must be carbonized or pyrolyzed to become charcoal. The use of charcoal in blast furnaces not only reduces carbon dioxide (CO2) emissions, but also sulfur dioxide (SO2) emissions because the sulfur content of charcoal is very low (around 100 times lower) than coke. Likewise, the use of limestone will decrease so that slag production will also automatically decrease. Likewise, it makes the blast furnace operation acidic.

Apart from a number of advantages obtained as above, it turns out that there are drawbacks to using charcoal in blast furnaces, namely in large blast furnaces which causes operational problems because the strength of charcoal is usually lower than coke. As a solution, there are three methods of using charcoal in the blast furnace process. First, with pulverized charcoal injection (PCI). With this method the charcoal must be crushed into a powder and injected into the blast furnace. Second, with charcoal powder mixed with coke powder into pellets or briquettes called charcoke. By making this charcoke, its strength is sufficient for use in conventional blast furnaces. And third, by replacing coke with lump charcoal for small capacity blast furnaces (inner volume 60 – 550m3). In small capacity blast furnaces, the compression pressure on each charcoal particle is much smaller than in large capacity blast furnaces. Sintering and pelletisation are not required in this case.

Energy plantations or biomass plantations can be created specifically to supply raw materials for charcoal production. The energy plantation will also absorb carbon from the atmosphere (carbon sink) in a certain volume. The volume of carbon from the atmosphere can be maintained in such a way that its function as a carbon sink can be carried out, namely by the amount of wood harvested for charcoal production not exceeding the growth rate of the wood biomass. In this way, the energy plantation cannot be finished in one harvest but is sustainable while maintaining its volume or area.

With continuous pyrolysis technology, charcoal production can be optimized. With this continuous pyrolysis technology, apart from the large charcoal production capacity, multi-use by-products are also produced, such as gas products which can be used as an energy source as well as biooil. Biooil can also be used as a raw material in the chemical industry. Charcoal production of tens to hundreds of tons per day is also possible with continuous pyrolysis technology.

And especially in Indonesia, as the owner of the largest oil palm plantations in the world, which is estimated at more than 15 million hectares and with palm oil mills reaching around 1,000 units, there is a lot of palm oil waste that can be utilized, especially empty palm fruit bunches or EFB (empty fruit bunch). The potential for charcoal production from EFB is also very large. Apart from that, as the 5th largest coal producer in the world with production of around 570 million tons per year, coal also needs to be processed into coke. Charcoal from empty bunches or EFB can be made into powder for PCI or into charcoke by compacting it, namely making pellets or briquettes with coke.