Can green power rid steel and concrete of their carbon heavy reputation?

The government’s repeated refusal to block a planning application for a new coal mine in West Cumbria was condemned by many environmentalists and climate scientists as hypocritical given its previous commitment to create a green, industrial revolution and rapidly cut greenhouse gas emissions.

Support for the facility, which is intended to produce coking coal for use in steel ­production, seems unthinkable in the midst of a climate emergency (it has now finally been called for a planning inquiry), but is perhaps indicative of the difficulties associated with decarbonising heavy industrial processes.

Bill Gates calls this the ‘75% problem’, how do we cut the three quarters of global emissions mostly generated through large-scale industrial and agricultural processes, which lie at the heart of many of the products we enjoy in modern life? Steel, concrete, glass and aluminium are all highly energy ­intensive to produce and difficult to address using traditional renewables.

Architects and engineers are, of course, in a strong position to cut embodied carbon in buildings through more intelligent design and specification choices, for example by designing more efficient structures that require less material, but the world’s reliance on high-impact construction materials also demands more fundamental changes to production.

Fortunately, a number of innovative technologies, and souped-up existing ones, are being developed. The race is on to see which will be ready to deliver at scale as the climate clock ticks down.

‘There are a number of promising technologies on the horizon,’ says Stephen Richardson of the World Green Building Council. ‘But with investment cycles in heavy industry in the order of 20 to 30 years, whatever companies invest in now is still going to be in use in 2050. So we need to use every lever we possibly can to persuade them to do it right this time.’

At source
The steel and cement sectors each generate around seven per cent of global CO₂ emissions, according to the International Energy Agency, a figure that must fall precipitously, even as demand for their outputs increases. 

These industries are considered tough to abate, largely because they rely on fossil fuels to generate the high temperature heat needed for certain processes. For example, blast furnaces used to produce iron for steel making operate at temperatures above 1,500°C.  

Getting the same heat from electricity, which can come from renewables, especially at large scale, is currently impractical and costly (cement kilns would require a complete redesign), and limited supplies of sustainable biomass exclude it as a substitute.

Many are pinning their hopes on green hydrogen which can be burnt to create high temperatures with no pollution, creating water as the only byproduct. Joe Jack Williams, an associate and researcher at architect FCB Studios which is a longstanding proponent of sustainable building, says: ‘There’s been an awful lot of talk about hydrogen, it produces great high grade heat and the real benefit is that you can generate it when you’ve got a surfeit of green energy that you can’t store elsewhere, for example from UK wind farms. Industrial uses are where it should be used and I can see that coming forward.’

Hydrogen-powered plants in Sweden are expected to produce the first market-ready zero carbon steel in Europe some time in the mid-2020s. A £17 million pilot plant and storage facility, operated by steel maker SSAB, iron ore producer LKAB and energy company Vattenfall, is already up and running in northern Sweden, using hydrogen instead of coal as the ‘reducing agent’ to remove the oxygen from iron ore. 

Another 800MW plant is being built by H2 Green Steel in the region, which is home to Europe’s largest iron ore mines, with a targeted annual production capacity of 2.5 million tons by 2026.

Not wanting to be left behind, a £6 million project in the UK is investigating how a combination of hydrogen and plasma technology could significantly cut emissions in cement and lime production, two highly polluting processes in concrete manufacturing. The Fuel Switching Project, run by the Mineral Products Association and funded by the Department for Business, Energy and Industrial Strategy, is due to begin trials in summer 2021 at sites operated by Tarmac and Hanson Cement. 

And a feasibility study has shown that electrical energy delivered by plasma torch could boost the combustion of biomass to generate higher temperatures and alongside green hydrogen could deliver net zero fuel for a cement kiln. 

‘The research is valuable to the government because it has to make some really big decisions about whether the UK goes down the hydrogen route or the electrification route, or if we do a bit of both,’ says Richard Leese, director of MPA Cement. ‘If fully deployed it would save about 0.6% of UK CO₂, equivalent to about 266,000 households.’

Souped-up solar 
For decades, the solar industry has been trying to produce the scintillating temperatures needed by heavy industry and now a project – backed by the world’s richest man, Bill Gates – appears to have made it work.

Heliogen sounds like something from the plot of a James Bond film. Artificial intelligence automatically controls a giant array of mirrors to align to reflect sunlight onto a target to generate burning hot temperatures of up to 1,500ºC.

That’s hot enough to fry a spy or, more usefully, power cement or steel making. It can be harnessed to split molecules to make green hydrogen. Heliogen is planning initial commercial deployments, but given Britain’s penchant for cloudy weather don’t expect to see it here any time soon.

Other metals benefiting from solar energy include aluminium. In a world first the Mohammed bin Rashid’s UAE solar park has started powering its production, which is being supplied to German car maker BMW.

Eliminating fossil fuel is one thing, but emissions from chemical reactions inherent to many production processes are often even tougher to address. For example, the CO₂ produced by the calcination reaction needed to produce clinker, the active ingredient in cement, accounts for around two-thirds of direct emissions in the sector. 

Options on the table include a fundamental shift away from conventional production processes and using different raw materials or binding agents. Many industries are backing the development of Carbon Capture Usage and Storage (CCUS) technologies that suck CO₂ directly from the air at source then store it, usually underground.

Tata Steel estimates that a combined approach, using a pilot technology it developed to remove certain pre-processing steps, and CCUS, could cut CO₂ in production by 80%.

‘Even if we look at fast and rapid decarbonisation, CCUS technologies will be required and used by the steel industry to rapidly decarbonise emissions to air,’ says Barry Rust,  marketing manager for energy & sustainability at Tata Steel. ‘Ideally, “carbon usage” would go into developing products that are infinitely recyclable so you’ve got a closed loop for the carbon.’

Scaling ambition
But despite billions of dollars of investment in CCUS and high profile backing from international governments, most technologies remain unproven at a commercial scale. 

Norway is about to launch the first full-scale carbon capture and storage project, named Longship, which will initially capture CO₂ emissions from the Norcem Heidelberg cement plant in Brevik near Oslo. In the UK, Hanson Cement is a partner in the HyNet North West consortium, which aims to create an exemplar low carbon industrial cluster involving carbon capture and storage, with CO₂ piped to permanent storage in depleted gas reservoirs in Liverpool Bay.

Wider investment and strong backing by the government is needed to make CCUS a strategic priority, says Leese: ‘We need a business model to help finance it and a plan for the infrastructure, it’s no good capturing CO₂ in a cement plant if you’ve got nowhere to put it. Similar to the grid electricity system, you need a grid to transport and store it.’ 

Technological innovations in heavy industry will be critical to achieving net zero, but also important are the design decisions architects and engineers can make today to reduce the impact of energy intensive materials and find alternatives that work.

Studies have shown that buildings are often overspecified because engineers choose standard sized steels and don’t have a mindset to reduce the amount of material going in. Alongside cement replacements like geo­polymers and alkali activated materials, concrete mixes can significantly increase the amount of recycled cementitious materials, depending on the application. 

‘Most engineers are quite happy to put 20-30% fly ash into a concrete mix as a like for like replacement for cement,’ explains Pat Hermon, technical lead on sustainable products at BRE. ‘People who think about it more carefully can achieve up to 70% direct replacement. It requires more work at the design stage, but often produces a stronger concrete.’ 

Such agile thinking will be key in the years ahead – one of a number of demand side signals needed to drive manufacturers and wider supply chains to innovate to head off a climate catastrophe.