Liquid sludge left over as a
residual from wastewater plants is usually dried and then either burned or
dumped, which is expensive and polluting. After drying, these are often known
as biosolids. A new process developed by researchers at the Polytechnic
University of Turin in Italy first heats the sludge without oxygen (pyrolysis)
to “carbonize” it into biocoal, or biochar. This further enriches the
biocoal in carbon, which can then be used for steelmaking. Methane from biogas
plants, or biomethane, is processed using this biocoal as a catalyst to produce
hydrogen in the process known as methane pyrolysis.
It is part of an EU research
initiative called H2STEEL that brings together academics and steel industry
experts from several European countries. The steel industry is responsible for
about 8% of global carbon emissions. The steel industry is notoriously
difficult to decarbonize, and this is an attempt to do that. The EU's Emissions
Trading System (ETS) puts a high price on carbon emissions, so steel is
susceptible to this pressure to decarbonize.
The process has three
outputs: 1) carbon-enriched biocoal, 2) hydrogen, and 3) phosphorus as a
byproduct that is used for fertilizer. Both the hydrogen and the biocoal can
replace some of the coal used in traditional steelmaking.
TechXplore notes:
“The team is now building a 4-meter-tall processing
machine in Turin to demonstrate the technology. "We break the biomethane
into carbon and hydrogen by using the carbonized sludge at 900°C,"
explained Chiaramonti. "That's how we turn it into biocoal and circular
hydrogen."
The process is also a
desirable solution due to its circular economy credentials, taking a waste
product and diverting it for beneficial use. ArcelorMittal, the second-largest
steel producer in the world with headquarters in Luxembourg, is an H2Steel
partner that is optimistic about the process.
The process is being trialed,
and it is hoped to be improved and become more economical so it can be deployed
in a few years and more widely after that. Costs are incurred in gathering the
sludge, transforming it, and delivering it to steel plants.
“A patent is already pending, and the partners are eager
to see results from the demonstrator. "What we're doing looks very
promising," said Chiaramonti. "Now it's a question of taking the last
steps."
The H2Steel Website describes
the process and what has been achieved so far:
“H2STEEL combines the conversion of biowaste and bioCH4
through innovative catalytic methane pyrolysis, to fully convert biowastes into
green hydrogen and biocoal, addressed to the steel making companies. At the
same time, the H2STEEL value chain enables the recovery of critical (inorganic)
raw materials from the biochars produced, which can be used as low-cost
biomethane pyrolysis catalysts.”
“The core of the project is the development of the
biomethane pyrolysis process carried out in a brand new, ad hoc designed, and
proof-of-concept (POC) reactor.”
Thus far, the process has
involved identifying and characterizing different waste sludge streams in terms
of annual production volumes, chemical composition, disposal cost,
availability, and inorganic compound content. The reactor and biochar quality
are still being tweaked.
The biomethane is converted
to hydrogen in a process known as methane pyrolysis, which involves heating the
methane without oxygen. This process for making hydrogen is much less
carbon-intensive than the steam reforming of methane to make hydrogen,
especially when energy inputs come from low-carbon sources.
The progress for the first
year of the project has been good, and further objectives include validation
and optimization:
“Validation and parametric optimization of the new
catalytic biomethane pyrolysis process in ad-hoc POC unit will be performed at
the final stage of the project, for assessing the continuous performances. Once
obtained the technical and performances validation of the H2STEEL concept, the
proposed system will be assessed considering the whole proposed value chain.”
References:
From
sewer to furnace: How wastewater sludge is greening steel production. Tom
Cassauwers. TechXplore. November 13, 2025. From sewer to furnace: How wastewater
sludge is greening steel production
Green
H2 and circular bio-coal from biowaste for cost-competitive sustainable Steel.
European Commission. Green H2 and circular bio-coal from
biowaste for cost-competitive sustainable Steel | H2STEEL | Project | Fact
Sheet | HORIZON | CORDIS | European Commission
H2STEEL:
Green H2 and circular bio-coal from biowaste for cost-competitive sustainable
Steel. H2Steel. Website. Home - H2Steel
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