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Glossary · Energy industry & energy transition

Hot Briquetted Iron, HBI

Hot briquetted iron HBI Direct Reduced Iron steel Industry hydrogen Decarbonization

Definition

Hot Briquetted Iron, HBI for short, is hot-briquetted direct reduced iron. It refers to Direct Reduced Iron (DRI) that is pressed into pillow-shaped briquettes directly after reduction while still hot. Under the definition customary in the industry, this takes place at more than 650 °C. The apparent density of an individual briquette is then above 5.0 g/cm³, i.e. above 5,000 kg/m³. It is measured according to the ISO 15968 standard. HBI is not finished steel. It is a metallic feedstock that still has to be melted and further processed in the steel plant.

The difference from DRI can be pictured as follows: Unbriquetted DRI, often called sponge iron in German, is porous and has a large internal surface area. It therefore reacts easily with atmospheric oxygen and water. In doing so it can heat up and release hydrogen gas. Hot pressing greatly reduces the pore space. Midrex, a supplier of direct reduction plants, states that HBI is about one hundred times more resistant to reoxidation than conventional DRI, absorbs around 75 percent less water and generates fewer fines during handling. Even so, HBI is not entirely non-reactive. Soaked HBI can temporarily heat up, release hydrogen and, in closed storage spaces, remove oxygen from the air.

Production

The basis is direct reduction. In this process, oxygen is removed from iron ore, usually in the form of high-quality direct reduction pellets, in the solid state. Unlike in the blast furnace, the ore is not melted. In the shaft furnaces common today, the reducing gas is usually obtained from natural gas. It is a mixture of carbon monoxide and hydrogen. Newer plants are intended to run wholly or partly on hydrogen. For HBI, the hot DRI is withdrawn from the reactor at 650 °C or more. It is then distributed to briquetting machines: two rolls with pockets press the material into a strand of briquettes. This strand is then separated into individual briquettes and cooled.

Several parameters are important for quality: total iron content, metallic iron content, degree of metallization, carbon content, gangue (that is, non-reducible accompanying substances such as silica) as well as density and strength of the briquettes. The International Maritime Solid Bulk Cargoes Code (IMSBC Code) describes the material as hot-moulded briquettes with at least 88 percent by mass of total iron. According to IIMA data, the bulk density, i.e. the density of a loosely poured heap, is about 2,500 to 3,300 kg/m³. Carbon helps later during melting. However, very high contents make compaction more difficult: according to Midrex, at more than 3.0 percent carbon the required density of 5.0 g/cm³ may no longer be achievable. HBI is traded in tonnes, not in an energy unit.

Why HBI exists: transport and storage

HBI arose as a response to a safety problem in sea transport. After the International Maritime Organization had established rules for shipping DRI in the early 1980s, a plant in Malaysia opted for hot briquetting. The first HBI cargo was shipped in 1984. Today the IMSBC Code lists HBI as a separate category: DRI (A), hot-moulded briquettes. According to Midrex, only this form does not have to be transported under inert gas at sea. Loose DRI grades are subject to stricter requirements. Nevertheless, industry guidelines prescribe precautions, such as ventilation, no loading in rain and monitoring for hydrogen. Proof of density is also provided for.

Distinction from related terms

  • DRI is the umbrella term for direct reduced iron. HBI is a compacted form of it that is better suited for transport. In addition, there are cold DRI (CDRI) and hot DRI (HDRI), which is fed directly into an adjacent steel plant.

  • Pig iron is produced in the blast furnace or by smelting reduction as a carbon-rich melt. HBI, by contrast, is never melted and therefore contains no impurities from coke or fluxes.

  • Steel scrap is recycled steel. Depending on its origin, it contains accompanying elements such as copper, tin, nickel or chromium, which can hardly be removed. HBI contains little of these elements, provided the ore is pure.

  • Iron ore pellets are still oxidic ore and not metallic iron. They are the starting material of direct reduction.

Use in the steel plant

HBI is used mainly in the electric arc furnace. There it dilutes the accompanying elements and the sulphur from the scrap. This makes high-quality steel grades possible, for example for flat steel, which could not be reliably achieved with scrap alone. It also allows cheaper scrap to be used for simple grades. Because the briquettes are dense, they sink quickly through the slag layer. They can be fed in batches or continuously. Blast furnaces can also use HBI in order to get by with less coke. In the electric furnace, electricity, lime, alloying agents and usually carbon carriers are still needed. Because HBI brings gangue with it, slag is also produced. Low-gangue ore is therefore particularly important for this route.

Energy demand and the power system

If the hydrogen is produced by electrolysis, every tonne of HBI embodies a large upstream electricity demand. A widely cited process study (Vogl et al., 2018) calculates about 51 kg of hydrogen including losses and about 3.48 MWh of electricity per tonne of liquid steel. The electrolyser needs the largest part of this. Extrapolated, this means roughly 3.5 TWh of additional electricity demand per million tonnes of steel. These values are model assumptions. The actual demand depends on the efficiency of electrolysis, the hydrogen excess in the reactor, the scrap share and heat integration. The study also emphasizes that both hydrogen and HBI can be stored. This allows production to respond more flexibly to a fluctuating electricity supply.

For the power system, what matters is that HBI separates reduction and steelmaking spatially. Reduction can take place where inexpensive renewable electricity, ore, water and a port come together. The steel plant then melts the briquettes elsewhere. In this case the electricity for hydrogen production is consumed in the exporting country. National statistics on electricity consumption and emissions of the importing country do not capture this upstream chain. For industrial regions this changes the planning of electricity and hydrogen networks. It can also mean, however, that value creation migrates away from the reduction stage.

Climate balance: HBI is not automatically green

HBI describes only a material form, not a climate profile. Natural-gas-based HBI causes less CO₂ than the blast furnace route, but is not emission-free. According to the study cited, hydrogen-based direct reduction can come down to only a few percent of the CO₂ emissions of a blast furnace. The prerequisite is electricity from renewable sources. If, on the other hand, the hydrogen is produced by steam reforming from natural gas or with fossil-influenced grid electricity, the advantage shrinks or disappears entirely. The label green HBI or an assignment to green steel therefore requires evidence: on the origin of the hydrogen and the electricity, on pellet production and on transport. A life cycle assessment captures this chain most completely. HBI is also not a hydrogen carrier: it contains no usable hydrogen. What is traded is metallic iron, and hydrogen is only a process agent.

Regulation in the EU (as of November 2026)

In the EU, direct reduced iron falls under CN code 7203, which also covers HBI. It is thus among the iron and steel goods of the Carbon Border Adjustment Mechanism (CBAM, Regulation (EU) 2023/956). Since the start of the definitive phase on 1 January 2026, importers have had to surrender CBAM certificates for the embedded emissions. For iron and steel, in principle only direct emissions are counted. Indirect emissions from electricity consumption do not count; an exception applies, for example, to sinter. In the transitional phase until the end of 2025, by contrast, importers also had to report indirect emissions. Which upstream emissions of hydrogen are counted in an individual case depends on the implementing acts. This question should be examined separately for each product.

Sources

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Edited by eCMS on 12.11.2026 05:06

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