The Caribbean countries are highly exposed to climate events, and buildings, especially housing, are particularly vulnerable. Those countries with a higher use of resilient materials perform better against climate impact and have smaller overall economic losses.
Cement and steel are among the most important resilient building materials in the Caribbean, but also require large amounts of energy to produce with correspondingly high levels of embodied carbon.
The fifth publication of the series “Building a more resilient and low carbon Caribbean” has examined three potential options to reduce the embodied carbon from the use of cement and steel in Caribbean buildings:
Option 1: Prioritizing the least carbon-intensive sources for cement and steel
Nine countries within the Caribbean produce cement, and these countries provide the majority of the cement supplied to Caribbean countries that do not produce it. By contrast, steel used in construction is largely sourced from outside the region, including as far away as China, Turkey, Brazil, and Canada. Trinidad and Tobago is the only country in the region with a history of significant steel exports.
The embodied carbon emissions related to the supply of cement and steel to the Caribbean include carbon emissions from the production as well as those resulting from shipping from the country of origin to the Caribbean region, with shipping accounting only 7% of the total embodied carbon for imported cement, and 9% of the total embodied carbon for imported steel, reflecting a very small role of shipping and impactful role of production in the total embodied emissions.
Changing supply chains so that all cement used in the region was sourced from the country with the lowest production embodied carbon was found to reduce embodied carbon by 26%. A similar shift for steel would reduce the embodied carbon by 39% (if it were able to be sourced from Trinidad and Tobago). Such a shift, however, could be limited by the source countries’ ability to produce sufficient materials, logistical constraints, and by contractual and trade relationships among suppliers. Shifting to the sources with the lowest embodied carbon could also increase the cost of cement and steel imports as current trade arrangements likely reflect a preference to source materials from the least-cost suppliers.
Option 2: Substituting traditional cement and steel with less carbon-intensive alternatives.
Another approach to reducing the carbon intensity of building materials is to use less carbon-intensive versions of standard building materials. While green steel is not yet commercially available, green cement with reduced carbon content and other alternative alternatives are available:
- Green cement (cement with reduced embodied carbon that is manufactured with reduced clinker content using alternative binding chemistries or manufactured with carbon-neutral fuels), is currently available and produced in the Caribbean, and has between 15% and 70% less embodied carbon than regular cement.
Option 3: Reducing the volume of cement and steel used per building through alternative designs and elements.
A free software was used to examine the potential reductions in embodied carbon emissions from applying different options, in a theoretical construction project. The greatest reduction in embodied carbon came in the outer walls, with a potential 72% decrease from conventional construction. The inner walls had the second highest reduction and the highest in percentage terms: replacing the brick and plaster walls with plasterboard on timber frames cut 83% of the embodied carbon. The floor and roof slabs each had a greater than 50% reduction in embodied carbon.
Using the material and design option with the least embodied carbon for each of the four building components, results in a 63% reduction in embodied carbon per square meter compared to the standard materials.
What’s the most effective way to reduce carbon emissions?
Opting for designs that require less steel (filler slabs for the floor and roof) or materials with less embodied carbon emissions (timber and plasterboard inner walls and cellular concrete block outer walls) – Option 3 – have the greatest impact on reducing embodied carbon emissions.
Changing the source of the cement and steel – Option 1 – or using green concrete – Option 2 – showed incremental reductions in the embodied carbon emissions, but these improvements were much less than the difference in embodied carbon emissions than changing the design solution.
Do you want to know more about this topic?
Download the full Report Decarbonization Pathways for the Caribbean Construction Industry!
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