Anything that reduces the carbon emissions associated with construction projects is welcome. Product innovations such as fossil-free steel and low carbon concrete will undoubtedly play an important part in a more sustainable construction industry in the future.
It’s also important to understand what some of these terms mean in practice and how much impact they can make on current construction projects.
Can Steel be Fossil-Free?
By replacing blast furnaces with electric arc furnaces it’s feasible to produce steel without burning fossil fuels. To be completely fossil-free, the electricity used to power the furnaces would need to come from 100% renewable sources.
Carbon emitted during raw material extraction and transport and subsequent fabrication of the steel produced by the plant would also have to be accounted for if we’re looking for truly net zero options.
To put emissions and net-zero steel into context, the global economy produced 1.9 billion tonnes of steel in 2020. As a result 3.7 gigatonnes (Gt) of carbon dioxide was emitted to the atmosphere – 2.6 Gt in direct emissions and a further 1.1 Gt of indirect emissions.
From 3.7 Gt to zero by 2050 is an astronomical target. Fossil-free steel is not due to be scaled-up to mainstream production for several years.
Low Carbon Concrete
Low carbon technology can reduce the carbon emissions from concrete by 35% or more. That’s a significant contribution when you consider that making a tonne of concrete is responsible for 600 kg of carbon dioxide. But is it really ‘low carbon’, even with this reduction?
Eliminating the remaining 65% of emissions could be achieved partly by carbon capture and storage and by pumping CO2 into the concrete mix. The technology to do any of this at scale doesn’t exist. The industry also expects to rely on offsetting to make up some of the balance. Offsetting doesn’t actually reduce carbon emissions and to some it is just ‘greenwashing’.
If using concrete or steel for a particular construction project is unavoidable, clearly it makes sense to seek out the lowest carbon alternatives. But, you also need to look beyond reassuring terms such as fossil-free and low carbon and evaluate the full carbon cost of material choices.
For the foreseeable future, the most reliable way to reduce the carbon emissions from construction is to specify methods such as SIPs and structural timber that have effectively negative levels of embodied carbon.
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