Can concrete be sustainable?

By Oliwia Krupinska

Concrete is everywhere--in our homes, sidewalks, schools--and has been a staple of construction for hundreds of years. Despite all the utility it provides, recent studies indicate that the process of making concrete is responsible for a significant amount of worldwide carbon emissions. In the era of decarbonization, improved concrete production practices have to become part of the solution to climate change, and proper legislation can encode those practices into law.

So far, within the Northeast, only New York has passed the Low Embodied Carbon Concrete Leadership Act (LECCLA), which creates pathways for state construction projects to use low-carbon concrete. New England also is poised to lead the way towards decarbonizing the construction industry, and its states could use New York’s experience thus far as a resource in implementing their own versions of it.

What is LECCLA

LECCLA refers to a variety of legislative strategies that open the door to prioritizing or mandating the use of low embodied carbon concrete in construction projects conducted by state agencies and establishing verification and certification systems. Given the wide array of ways that concrete can have its carbon footprint lowered, these bills do not define appropriate production practices but rather they prescribe performance based standards which consider things like cement content and total carbon emissions.

Why Low Carbon Concrete?

Among the many facets of the industry that could see emission reductions lies an often overlooked, yet highly carbon-intensive component of nearly every building: concrete. This omnipresent building material is the second most used material in the world, only behind water, and is responsible for 4-8% of the planet’s carbon emissions, most of which are concentrated in the creation of cement, the glue that holds it all together. Thanks to this easily identifiable, yet significantly influential source of carbon emissions, policy makers have an opportunity to take action on concrete production that could easily lower worldwide emissions.

Embodied Carbon

In order to achieve decarbonization goals, LECCLA leverages embodied carbon, the carbon emissions associated with producing concrete (think extraction of raw materials, transport and manufacturing) and gives preference to lower-emission concrete in state building projects.

For a long time, there was no metric that encompassed all the carbon emissions associated with construction of new buildings, leaving us with a severe underestimate of their environmental impact. The embodied carbon metric allows us to track which building material is more environmentally friendly and give us a much more accurate picture of the environmental cost of building new structures. In fact, traditional concrete production emits as much as 0.93 pounds of CO2 into the atmosphere for each pound of concrete, which adds up quickly when you try to build a home, office building, roadway or bridge that uses tons of concrete.

So What Can We Do?

Carbon emissions of concrete can be lowered in a variety of ways, from simple improvements in building practices to major innovation in the manufacturing process. Lowering the embodied carbon of a construction project can be as simple as not buying excess material, choosing the right concrete mix and adding more reinforcement.

In addition to these practices, many organizations are now using less polluting production strategies. These technological advancements include using carbon-cure technology, in which concrete is cured with CO2 rather than with water, lowering the cement content by using fillers like fly ash and slag, and opting for natural gas instead of coal during heating processes.

Environmental Responsibility

This is not to say that LECCLA is a silver bullet. Some environmental advocates raise concerns that LECCLA fails to mention potential health hazards that come with some low carbon practices.

In the New York LECCLA, the Act creates a stakeholder advisory group which includes a variety of professionals such as industry representatives, engineers, and environmental advocates, who work together to ensure that all aspects of the LECC shift are balanced and certification standards are set to reach optimal outcomes. As LECCLA makes its way into new state legislatures, states can assess whether existing occupational safety provisions should be included in their versions of the bill.

Moving Forward

LECCLA is a promising move towards lowering the carbon emissions of a major industry and should be considered and passed by New England states in the upcoming legislative cycle. By requiring state projects to use low embodied carbon concrete, the legislation shows that small but frequent decarbonizing steps can provide a reliable pathway toward a decarbonized future. Based on New York’s experience, we can take advantage of the lessons learned thus far and pass improved versions of this legislation, custom tailored to individual state needs.

Although there are technological advancements under way that may one day move the industry away from concrete, LECCLA is something New England states can do today. And in a climate crisis that the world has stalled on for so long, the sooner we act, the better.