Exploring the prospects for metallurgical biocoal

Held in Ghent, Belgium in mid-February and organized by Bioenergy Europe, some 70 or so participants joined the aptly named “Prospects of Biocoal for the Metallurgical Industry” workshop that marked part of a grand finale of a three-year EU project called “Market Uptake Support for Intermediate Bioenergy Carriers” (MUSIC).

Co-funded under the EU’s Horizon 2020 research and innovation program, the overall aim of the project is to “facilitate the further introduction of intermediate bioenergy carriers (IBCs) by developing feedstock mobilization strategies, improved logistics, and IBC trade centres” with the specific IBCs being torrefied biomass, fast pyrolysis bio-oil (FPBO), and microbial oil.

Coordinated by BTG Biomass Technology Group, this workshop focused on the former IBC – biocoal.

An enormous challenge

Setting the context and providing perspectives, Åsa Ekdahl, Head of Environment & Climate Change, World Steel Association (worldsteel), a Brussels-based non-profit organization whose members account for around 85 percent of global steel production, noted that 2022 saw 1.9 billion tonnes of crude steel produced, an increase of 120 percent since 2000.

In 2020, which also saw almost 1.9 billion tonnes of global crude steel production, the average emission was 1.9 tonnes of carbon dioxide (CO₂) per tonne of steel produced, while the total direct emissions were of the order of 2.6 billion tonnes, representing between 7 percent and 9 percent of global anthropogenic CO₂ emissions.

Biomass can make an important contribution

These numbers aside, Ekdahl offered valuable insight into how and where biomass could make an important contribution as part of a suite of carbon intensity reduction technologies and measures for the steel industry.

Two of these measures were later exemplified by Association member and project partner ArcelorMittal, the world’s second-largest steel producer.

The company has implemented demonstrations that serve as one of the project’s case studies at its steel mill in Ghent.

Biomass can play an important role by replacing a proportion of fossil carbon resources – as a reductant, as a source of alloying carbon, and as a replacement for fossil energy in other processes. The potential for biomass-derived products to mitigate CO₂ emissions in the Blast Furnace Basic Oxygen Furnace (BF-BOF) route is substantial, Åsa Ekdahl said.

Most steel in Europe is produced by either the BF-BOF route or the Electric Arc Furnace (EAF) route.

However, Ekdahl highlighted that despite the fact that historically, wood-derived charcoal had been used right up to the pre-industrial age before being replaced by fossil carbon, steelmaking has in modern times, evolved processes and scale.

The low-carbon transition of the steel industry will involve new or redesigned production processes and input materials. Charcoal or biochar cannot be swapped 100 percent like-for-like with coal using existing technology but needs to be tailored to provide specific co-product properties. Furthermore, robust supply chains will need to be developed to collect biomass at volume, convert, process, and deliver it reliably to steel manufacturing facilities, without undermining steel quality, existing biomass uses, or compromising sustainability, Åsa Ekdahl said.

Challenges in the ferroalloy industry

Dr Sten Yngve Larsen, a Senior R&D Specialist with Eramet Norway, part of Eramet Group, a major player in the mining and processing of metals such as manganese (Mn), and nickel (Ni), as well as mineral sands such as ilmenite (a titanium-iron oxide mineral – FeTiO₃) and zircon (a zirconium (IV) silicate – ZrSiO₄), gave a detailed account into the ferroalloy industry, using Norway as an example.

The metallurgical industry is one of Norway’s largest land-based industries. However, fossil carbon is not used as an energy source, but as a reductant utilizing chemical potential to extract the ore and produce metal. The Norwegian ferroalloy industries have ambitious plans to increase the biocarbon share in their reductant mix towards 2030, revealed Dr Sten Yngve Larsen.

However, challenges lie ahead for biocarbon as the technical quality requirements for use in ferroalloy processing are very demanding.

Low reactive metallurgical coke (metcoke) is the benchmark for manganese reductants in closed submerged arc furnaces, the dominant furnace type in Norway.

There is a highly complex relationship between the reductant properties and furnace performance. The quality demand for manganese is challenging to meet and a biobased reductant resembling metcoke properties for use in a closed submerged arc furnace simply does not exist in the market today. On the other hand, the properties of biocarbon are close to a perfect match for other metallurgical processes such as silicon (Si) and ferrosilicon (FeSi), said Dr Sten Yngve Larsen.

Just as relayed by Åsa Ekdahl for iron and steel, apart from the furnace process and maintaining end-product quality, the biocarbon needs to be able to meet other criteria including transport, handling, storage, and off-gas cleaning.

Tests at two of our manganese alloy facilities in Norway that have closed submerged arc furnaces show that low blends of charcoal, under 10 percent, could be possible without disturbing the furnace and gas cleaning processes. In Brazil, where smaller, open and semi-closed submerged furnaces are used, up to 70 percent charcoal is being used, said Dr Sten Yngve Larsen, citing Maringá Group, the second largest ferroalloy producer in South America, which is also self-sufficient in biocarbon reductants that it produces from its own Eucalyptus plantations.

That said, the ferroalloy industry in Norway is benefiting from strong support from Norwegian Governmental institutions to support biocarbon development with over ten R&D projects of which five are ongoing.

Taking Eramet Norway as a case, Dr Larsen highlighted that the company uses around 240 000 tonnes per annum of fossil carbon reductants.

Replacing 43 percent with a biocarbon equivalent of metcoke would mean 100 000 tonnes of biocarbon.

This would require 1 million m³ of woody biomass, which in roundwood terms corresponds to roughly 10 percent of the average annual forest harvest in Norway.

Woody biomass including logging residues is available in Norway, but prioritization may become necessary as well as widening the scope to other biomass sources, ended Dr Sten Yngve Larsen highlighting offshore kelp as one example.

Deploying TorrCoal tech at ArcelorMittal

As mentioned, the industrial case in the project for torrefied biomass as an IBC is ArcelorMittal Ghent, which is in the finishing stages of installing a TorrCoal torrefaction plant onsite at its steel mill in Ghent.

This in itself is part of another EU co-funded large-scale demonstration project called “TORrefying wood with Ethanol as a Renewable Output” (TORERO) that aims to demonstrate “a cost-, resource-, and energy-efficient technology concept for producing bioethanol from a wood waste feedstock, fully integrated into a large-scale, industrially functional steel mill.”

Using waste wood as feedstock, this is converted to biocoal by torrefaction, and the biocoal replaces a share of fossil powdered coal in a steel mill blast furnace.

The carbon monoxide (CO) in blast furnace exhaust gas is captured and microbially fermented to bioethanol for use as fuel or as a biochemical.

The latter part of the TORERO project – the bioethanol part – has already been implemented as a separate project, the Carbalyst (Steelanol) project, and the 80 million litre per annum plant was inaugurated late last year.

In the blast furnace 50 percent of the carbon is powder coal and 50 percent is coking coal. With TORERO, the aim is to replace 5 percent of the powder coal with biocoal, said Wim van der Stricht, CTO of Technology Strategy, CO₂ and Circular Economy at ArcelorMittal, adding that the feedstock is regionally sourced category B waste wood for which there is no recycling option other than energy recovery.

On an annual basis for the project, around 180 000 tonnes of waste wood to provide 75 000 tonnes of biocoal.

This will be supplied by the waste management company, and TORERO project partner, Renewi which is expanding an existing waste recycling facility in close proximity to the torrefaction plant.

Licensed from TorrCoal, also a TORERO partner, the torrefaction plant is being built in-house by ArcelorMittal and comprises a storage area, infeed hopper, belt dryer, TorrCoal technology from Perpetual Next – an indirectly heated rotating drum reactor with four separate heat zones, off-gas combustor with heat recovery and flue gas cleaning, and biocoal cooling screw discharge.

The plant is to begin commissioning later in 2023.

Although not part of the MUSIC project, two other carbonization technology providers, Envigas and Airex Energy also held presentations.

Both are providing or aiming to provide biocarbon to the metallurgy industry using proprietary technologies, and as such have experiences to share.

The former operates a 500 kg per hour biocarbon pilot demo plant in northern Sweden operational since 2019, and the latter a 2 tonne per hour commercial demo facility in Québec, Canada, operational since 2016.

MUSICal recommendations

Closing out the workshop Manolis Karampinis noted that the MUSIC project as a whole had arrived at four policy recommendations for stimulating IBC market uptake of which perhaps consistency and longevity in biomass sustainability criteria, along with the adoption of a “soft” cascading principle were the most critical.

The Renewable Energy Directive (REDII) sustainability criteria have not yet been fully implemented or evaluated, and yet the REDIII proposals lean toward forest sector regulation that historically, is a Member State competence area. With high uncertainties over what is considered and what is not considered sustainable, thus eligible for support, investors will simply refrain from making decisions for IBCs project development. One framework regulation that governs sustainability criteria irrespective of end-use and that is congruent across other regulations, for example, Taxonomy is what is needed, remarked Manolis Karampinis.

Regarding biomass cascading, Karampinis said that a mandatory cascading principle would be hard to implement citing Sweden’s wood fibre law in the 1980s as an example of a failed previous attempt.

Properly functioning markets can ensure that IBCs and other bio-products will find use in the higher added value applications, provided there is local-regional demand. IBC producers should be allowed the flexibility to respond to changing market conditions as they see fit, Manolis Karampinis said.

Another MUSIC project recommendation was to set minimum targets for IBCs instead of quotas, as the latter is dependent on the overall level of energy consumption and may be affected by market shocks as demonstrated by Russia’s war on Ukraine.

Setting minimum targets, for example, “replace 1 million tonnes of metallurgical coal with torrefied biomass by 2030”, sends a strong political message to IBC investors and project developers, said Manolis Karampinis, using the biogas industry’s 35 billion m³ (bcm) of sustainable biomethane by 2030 target as an example.

The final MUSIC recommendation was the need to continue to promote and provide funding for innovative applications and bringing emerging technologies to market.

While torrefied biomass and fast pyrolysis bio-oil (FPBO) can be considered to be at Technology Readiness Level nine (TRL9), significant improvements in production processes can still be anticipated. Likewise, current or emerging applications in heat and power, or transportation can still be improved, while new end-uses for IBCs, with lower TRLs, may also materialize in the hard-to-abate industries with demand for fossil carbon as we have heard from the metallurgical industries. Therefore, along with the other policy recommendations, continued access to funding for innovative, first-of-a-kind projects and for improving current technologies will be instrumental in unlocking this potential, ended Manolis Karampinis.