How to Reduce Carbon Footprint in Construction
Cement accounts for 2.2Gt of CO2 emissions in 2014, including 1.2Gt of process emissions and 0.75Gt of emissions from heat1. Decarbonizing the cement sector poses one of the most difficult challenges in the shift to a low-carbon economy due to process emissions, which are particularly difficult to avoid. New cement chemistries could be less carbon-intensive, but there is a risk that these new chemistries can only make a moderate contribution to emissions reductions due to scarcities of local resource supply and differences in the resulting cement properties.
Eliminating process emissions will require the use of carbon capture, which will inevitably add some cost, even if the CO2 is then used as input to concrete rather than simply stored. Meanwhile, carbon emissions from heat used in cement production could be reduced via a switch from coal to gas (particularly in China) and could eventually be eliminated via heat electrification, the use of biomass or the use of hydrogen.
But, each of these three routes would likely entail significant additional costs. Reducing carbon emissions from cement will therefore also entail better demand management. Cement is an essential construction material, key to the development of regions like India and Africa which are still in the process of urbanizing and building up key infrastructure. Unless there is a major shift to use timber as a substitute for buildings material, which is not without its own challenges, total global cement production will continue to grow rapidly.
However, demand growth could be slowed down via greater materials efficiency in building design, waste reduction and some materials circularity. Given these challenges, cement decarbonization is likely to imply a significant increase in cement prices and could account for circa 60% of the global costs of decarbonizing all the harder-to-abate industrial sectors2. But these costs can probably be absorbed by the economy without adverse consequences, given the inherently local nature of cement production and distribution, and the limited impact on end consumer prices.
Demand Trends to 2050
Cement is a vital input to concrete, which in turn plays a fundamental role in the construction of most modern buildings and infrastructure, for instance for roads, dams, airports and wind turbine bases. Current global demand of circa 4.2 billion tons per year is forecasted by the IEA’s Reference Technology Scenario to grow to 4.7 billion tones by 20503.
The biggest increase in demand for cement is not expected in developed economies such as the US and Europe, but rather in the rapidly growing and urbanizing economies, which are still going through a major construction phase. While the US and Europe account for only 13% of global cement production, China’s 2.5 billion tones currently account for 60%4.
This figure is likely to fall as the huge Chinese construction boom is coming to an end. By contrast, cement production in India and Africa is likely to more than triple over the next 35 years as urbanization drives huge demand for concrete.
Accordingly, CO2 emissions per ton of cement can be broken down as follows:
- Direct process emissions, which are inherent to the chemical reaction, are about 0.5 tons of CO2 per tonne of cement produced and are the same regardless of the energy source of the heat production but can vary depending on the feedstock.
- Emissions resulting from the combustion of fuel to produce heat, which are on average about 0.3 tons of CO2 per tonne of cement today, will vary considerably depending on the fuel input and could potentially be brought down to zero in future.
- Smaller indirect emissions resulting from the generation of electricity used in the various crushing and grinding processes, which amount to less than 0.1 tons of CO2 per tonne of cement, given the typical carbon intensity of electricity generation today.
Reducing Carbon Emissions Through Cement Demand Management
Decarbonizing cement production while possible through a variety of different routes is almost certain to result in significant additional costs. Moreover, the potential role of carbon capture and storage as a route to eliminate process emissions may be limited in specific geographies by a lack of storage capacity. It is therefore vital to explore all possible routes to reduce the demand for cement while continuing to provide the end products or services which deliver customer benefits.
The Material Economics analysis considers 3 ways in which materials use in buildings could be reduced through greater materials recirculation, more efficient use of materials in buildings, and by getting greater value out of each square meter of building during its life.
Reaching Net-zero Carbon Emissions from Steel
Energy related emissions from the iron and steel industry currently amount to circa 2.3Gt CO2, accounting for 7% of total global emissions from the energy system. However, under a business-as-usual scenario, they would grow to 3.3Gt by 2050, representing 7.5% of global emissions and 34% of the industry sector emissions.
To tackle the major impact of these emissions on the economy, it is essential to assess whether total demand for steel could be reduced, or whether demand could be met by more scrap based (recycled) steel, which is less carbon-intensive than ore-based (primary) production. However, as production per capita is still expected to grow strongly in most developing regions with the exception of China, it will not be possible to achieve the necessary emissions reductions without developing and deploying zero-carbon ore-based production routes, through radical process changes. The two main routes to decarbonization will certainly be hydrogen-based reduction and carbon capture, combined with either storage or use (CCS/U), but the optimal decarbonization pathway will differ by location depending on local electricity prices, and CCS (copper clad steel) cost and feasibility.
The ETC (Energy transition commission) is confident that a complete decarbonization of the steelmaking industry is achievable by mid-century, with a modest impact on end-consumer prices and a limited cost to the overall economy. However, given that steel is an internationally traded commodity, an uneven transition on a global scale may create competitiveness issues. An internationally coordinated carbon price coupled with downstream levers, like the implementation of “green steel” standards and labels across the steel value chain, are therefore essential to mitigate the risks of competition distortion.
These proposed steps taken together can substantially reduce carbon foot prints in construction.