Precast and Carbon Emissions

At current rates, global carbon emissions are 36 billion tons annually and rising.  With a new focus on reducing carbon emissions to help counteract climate change, the precast industry has begun focusing on improving their processes and educating design professionals on the sustainability that concrete can bring in the long-term.

How much carbon does precast contribute to global emissions? 

Cement accounts for 3% of global emissions because of its use of clinker and limestone which emits carbon during production. This percentage also includes the actual energy inputs needed to produce the cement itself.

What is the comparison to timber?

Precast is often compared to timber when designers are considering sustainable materials to use in their structures.  Deforestation is responsible for 2.2% of global emissions (which is the difference between carbon from deforestation and the positive offset of replanting), with 8-10% of timber in the construction industry coming from deforestation.  Most timber comes from forest degradation which means trees are selected to be cut down leaving other trees intact.  

The actual carbon emissions of the timber industry is not fully analyzed because there are no international standards for tracking it.  Wood harvested from one country can be shipped to another with the carbon emissions impacted only being counted in one country or not counted at all. 

For example, each year 80,000 hectares of trees in North Carolina are cut down to produce wood pellets that are then burnt in power plants in the UK, as well as for paper and timber. The state does not count the resulting emissions. This makes it nearly impossible to determine the actual global emissions from the timber industry and compare it to precast.

Although it is true that if managed correctly for long-term carbon storage timber is an amazing carbon storage device, currently timber is harvested well before trees can fully store their potential for carbon making it less efficient in comparison to precast.

What ways can precast help with its emissions?

New technologies to capture or reduce carbon 

Since there are no other construction materials like concrete, professionals have been trying to implement new technologies to help reduce its carbon footprint.  There are a variety of methods being tested including direct-air capture (DAR) which is a machine that acts as an artificial tree collecting CO2 particles out of the air passed through it.  There are also ideas such as capturing CO2 from smokestacks and putting that carbon into cement products to replace certain high carbon materials in concrete like limestone with other less carbon producing compounds.

New greener concrete formulas

Concrete professionals are currently working on other types of cement to help counteract the carbon emissions of current products.  One of these newer innovations is called PLC or Portland-Limestone Cement.  This concrete provides the same durability and resilience, but has a reduced carbon footprint of 10%. It can be used for basically any structure with no modifications to mix design or placing procedures.

Reduces waste over the long term 

At its core, precast is inherently resistant to storms and provides protection from wind, surge, and flying debris.  This storm resistance has been confirmed through numerous impact tests.  But aside from its resistance, precast structures are able to recover quickly after storms. Because the precast is mold/mildew resistant, it is able to not only withstand flooding, but recover without long lasting damage. This resiliency translates into structures that last longer and withstand much more than timber structure which have to be replace more frequently and end up causing more materials to be sent to the landfill.

The Takeaway

Improvements in both the timber and precast industries could mean larger impacts on reducing global carbon emissions for the construction industry as a whole.  Working together they could significantly cut their emissions together and provide designers solutions that meet their clients long-term carbon and sustainability needs.