New Research on the Environmental Impact of Concrete
(Concrete Helper 1-16-2012) Nearly 500 representatives from industry, government and academia convened at MIT in August for a day-long symposium on the environmental impacts of concrete – a topic of no small importance, given that concrete is the most widely used man-made material on earth and that its use contributes about 5% of global CO2 emissions.
Sponsored by MIT’s Concrete Sustainability Hub – a collaborative research center involving the School of Architecture + Planning and the School of Engineering – the meeting featured the release of two important new reports on the carbon emissions of concrete buildings and pavements over the course of their life cycles, and included a new set of analyses to help designers and builders determine which of their construction options involve the lowest environmental costs.
With governments all over the world demanding major carbon cuts, the need for such research is clear, especially when it comes to buildings: the International Panel on Climate Change has identified buildings as the most cost effective of all sectors for achieving carbon reductions; in the US, buildings are the largest consumers of energy and the largest source of greenhouse gas emissions; and in acknowledgment of both those assertions, the AIA has embraced an initiative called the 2030 Challenge – a call to reduce carbon emissions for any given building type by 100% by 2030.
Led by professors John Ochsendorf and Les Norford from the Building Technology Group in SA+P’s Department of Architecture, the newly-released life cycle research analyzed the overall performance of residential buildings, commercial buildings and highway pavements for different climatic regions, considering all phases of their life cycle from production and transportation through construction, maintenance and operations and finally through disposal.
Considering three classes of buildings – a 12-story commercial building; a four-story multifamily building, and a two-story single family house – the analysis demonstrated that greenhouse gas emissions due to building operations are typically responsible for more than 90% of the building’s life cycle emissions. The research went on to explore specific strategies for reducing the carbon footprint of each life-cycle phase, and their implementation costs.
In terms of reducing emissions in the operations phase, simple approaches such as using more efficient lighting and windows, making smarter use of insulation and better use of thermal mass can all not only have a substantial impact on emissions but can also save money in the long run. When it comes to embodied emissions – the release of CO2 during the production phase – infusing concrete with industrial byproducts such as fly ash or blast furnace slag turns out to be highly cost effective, in part because less cement is required.
In addition to quantifying the options for reducing life cycle CO2 emissions, the research promotes a standardized metric of global warming potential. While the field of life cycle assessment has been around for several decades, the lack of standardized metrics has impaired its ability to benchmark current practices, compare concrete with competing materials and understand the importance of different phases of the life cycle. In support of standardization, the research proposes good-practice concepts including an adequate level of transparency with regard to the data, functional units and other important parameters.
The research also aims to develop greater ‘carbon literacy’ among architects, builders and clients by providing methods to track the carbon footprint of a project over the course of its lifetime so they can make more informed decisions on how to minimize environmental impact.
The meeting in August also featured presentations on two other areas of research at the Concrete Sustainability Hub – concrete materials science and the econometrics of sustainable development. Research in concrete materials sciences is focused on the basic molecular structure of cement in hopes of producing a ‘greener’ concrete, possibly by swapping one chemical element for another to reduce emissions during manufacturing, or by designing a stronger concrete that would require less material for construction projects. Research on econometrics is focused on concrete’s impact on the economy in terms of job creation, system dynamics and the input-output effect of policy. To learn more about that research, and to download copies of the two life-cycle assessment reports, visit mit.edu/cshub.
The Concrete Sustainability Hub was established in October 2009 with an initial grant of $10M from the Portland Cement Association and the Ready Mixed Concrete Research & Education Foundation, with the goal of accelerating emerging breakthroughs in concrete science and swiftly transferring those research advances into industry.
The Portland Cement Association conducts market development, engineering, research, education, and public affairs programs; the RMC Research and Education Foundation supports research and educational programs that will increase quality, professionalism and environmental stewardship in the ready mixed concrete industry.