Host intro: This month, Northwest Public Radio looks at green building practices in a special on-air and online series. We know that the construction industry is a major contributor to carbon emissions. However the industry is just beginning to tally the energy and emissions that go into construction materials and assembly. Correspondent, Mary Hawkins spoke with architect, Sadie Martin, about her study called “Constructing a Carbon Conscienceness”.
Listen to the feature here.
Mary Hawkins: Sadie Martin, a recent graduate of the WSU masters in architecture program, is passionate about “CO2” reduction in her field of building design and construction. She recently set out to help map the carbon footprint of the construction industry – by studying one site in Bothell, Washington: the Cascadia Community College ’s Center for Global Learning and Arts.
(photo: Cascadia's new, Gold LEED-certified Center for Global Learning and Arts).
Her goal is to help identify all of the carbon emissions or “embodied carbon” in the building process. Embodied carbon is the total energy consumed during extraction, transportation, manufacturing and fabrication of a product – in this case, a building.
Sadie Martin: If we can track materials better from the raw extraction point to the construction site, we’ll have a much better idea of exactly what the impact of that material is.
Hawkins: Last summer, Sadie Martin set out to track one construction material at one job site: concrete. Cement, the key ingredient in concrete, is one of the most energy intensive of all industrial manufacturing processes, and a significant industrial polluter.
Her work technique was very simple.
Martin: I showed up on the job site and I had a stopwatch and I timed how long it took for mixers to deliver a load and how many loads we’d get in a day and then observed what other kind of equipment was running at the same time that the concrete was being delivered.
Hawkins: Martin and another Hoffman Construction intern tallied hundreds of hours of travel and idle time for a number of vehicles, including large diesel pump trucks. Each pump truck or mixer consumes about 6 gallons of diesel each hour, which means 133 pounds of CO2 emissions. The total of what they call “delivery emissions” for concrete on that job is estimated at 180 metric tons of CO2. According to one carbon calculator, it would take a 45 acre forest one year to absorb that much CO2.
That’s a 45 acre forest to offset just the jobsite delivery emissions of concrete for ONE project.
To minimize transportation emissions, the U.S. Green Building Council's LEED certification criteria specifies a 500 mile radius for materials to be determined as “sustainable”. Sadie Martin’s building site in Bothell performed pretty well with one notable exception…
Martin: We had ingredients coming from south Seattle, Everett, Arlington, and then…China. (laughs)
Hawkins: And so you had things that were from 50 miles away and some things that were from several thousand miles away?
Hawkins: I don’t know how many miles away China is...?
Martin: It’s about 5,000, I approximated.
Hawkins: How did you know it was from China?
Martin: Because I called the concrete manufacturer and I asked them where they were getting their cement. He told me from China…and so I did some research on major cement processing locations in China and I had to make an assumption about the distance it was going… but…when it’s being processed over there and you have no information exactly where or who’s doing it, you don’t know where the lime is coming from or the other ingredients that you need to make the cement. …that’s a whole ‘nother addition to the embodied carbon of concrete.
There’s a sense of depression late at night when I’m calculating these numbers. But one of the things that I had to keep telling myself is that our industry will always contribute to the atmospheric CO2. But being in an industry with so much control over our natural resources, we have the opportunity to become the leaders in the fight against climate change.
Hawkins: Architect Sadie Martin works for Miller Hull in Seattle.
Using local materials in construction not only reduces carbon emissions, it could strengthen our strapped regional economy. Other carbon reduction solutions include: providing offsetting fees, requiring low-carbon materials, minimizing the footprint of buildings, making equipment operations more efficient and creating aggressive legislation regarding carbon emissions.
For more information about CO2 and the construction industry, go to “Our Northwest” at N-W-P-R dot org. For Northwest Public Radio, I’m Mary Hawkins.