Concrete, Flyash, and the Environment - Proceedings
A forum held 8 December 1998 - Sponsored by EHDD Architecture and Pacific Energy Center
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Environmental Impacts of Cement and Flyash
Scott Shell EHDD Architects
| Our office, EHDD Architects, has a long history of working on projects
that are related to or directly address environmental issues; ranging from aquariums
to zoos to environmental research labs. So we're aware of these issues and we work
closely with scientists who talk to us in a very compelling manner about the critical
importance of various environmental issues. Whether it's the Monterey Bay Aquarium
research scientists concerned about the impact of warming ocean waters, or the UC
Irvine's Earth Systems Science Laboratory researchers describing their efforts to
reconstruct historical temperatures from coral samples, they express deep concern
about what we are doing to our ecosystem. But in the last year something different has happened, something that at least for our firm hasn't happened before. We have been approached by eight prospective clients asking us if we can design "green buildings", if we know how to design a building from a sustainable point of view that will reduce environmental impacts. These clients tend to be the savviest of clients, some of the best clients with projects that we'd really like to get rather than you other architects out there. They included within the past year the Exploratorium, the New England Aquarium, a new Headquarters for the Rand Corporation, all of the work in the Presidio, Patagonia, Residential clients, the Golden Gate Recreational Association, and a major school district. The total value of construction for these clients alone is over $200 million. When clients are hiring architects based partly on these issues, we take it very seriously, and we assemble a team of consultants that take it seriously as well. It is essential in sustainable design to have an integrated team approach with all of our engineers and consultants each contributing their expertise. We architects only spec a certain percentage of the building, we spec finishes, cladding, roofing, etc. A great deal of the mass of the building is in the structure, or in areas designed by mechanical, electrical, or plumbing engineers, and others. We've been able to find several mechanical and electrical engineers with an interest and knowledge of sustainable design to work on our projects, but there don't seem to be many structural engineers in this area, and our clients want them and we need them. To be successful, this is absolutely going to take teamwork. Environmental Impacts As I mentioned, these clients tend to be the savviest and best informed clients, and what's driving this from their point of view is an understanding of the environmental impacts that our buildings are having. Most of us tend to think that cars are the source of our environmental problems and yes, they are a big source. But buildings are responsible for a larger percentage of most environmental impacts. Energy is often used as an indicator for other environmental impacts such as emissions, pollution and so forth, and buildings consume about 40% of all the energy used in the U.S.(1) (figure 1.2). All transportation including cars is only about 28%. Raw material use is the same way (figure 1.3), buildings consume about 30% of all raw material flows in this country(2), this is huge. Think of all the environmental impacts at all the factories producing 30% of our raw materials. Buildings are responsible for about 40% of all air emissions, and the list goes on and on. Part of those emissions are due to the cement that we use in our concrete. With concrete it is the cement that is responsible for the largest percentage of environmental burdens. And most of these environmental burdens happen in the cement kiln(3). A cement kiln is the largest piece of moving industrial equipment in the world. You put minerals in one end, which others will describe later, and heat it up to 2,700 degrees Fahrenheit. It takes an enormous amount of energy to heat millions of tons of raw materials up to 2,700 degrees, basically you're melting stone. Most of the energy used is coal, and coal releases very large amounts of Carbon Dioxide (CO2), Nitrous Oxides (NOx), Sulfur Oxides (SOx), particulates, and other things that we don't particularly want to have in our atmosphere. So many impacts are due to the energy used in the manufacturing process. There is also another very large source of CO2, and that is the chemical reaction that takes place. Calcining limestone into lime releases as part of that chemical reaction very large amounts of CO2 (figure 1.4). You can see the combined CO2 emissions here, with the energy and the chemical reaction totaling about 631 pounds per cubic yard of concrete based on an ordinary concrete mix. That's a lot of CO2. Another stat is that one ton of cement produces over one ton of CO2, and world cement production was around 1.3 billion tons a few years ago, so we're putting an equal or larger amount of CO2 into the atmosphere(4). This is about 8% of CO2 emissions worldwide, a huge percentage for one industry(5). Impacts of Carbon Dioxide Emissions So what's the big deal with CO2? As many of you know, it is the primary greenhouse gas that is contributing to global warming. A lot of the general public perceives that there is split in the scientific community about global warming. That's not true. There is a very clear consensus among scientists that global warming is happening, and that it is a very real issue. The United Nations has put together the Intergovernmental Panel on Climate Change (IPCC), 2,500 top scientist from around the world to advise governments at the negotiations in Kyoto and elsewhere. And they've told us that not only is global warming real, but that its here now, that we are seeing its signature in our current climate. That we have already affected the climate on a global scale, mostly from burning fossil fuels(6). The greenhouse effect itself is a natural phenomenon and if it were not for the greenhouse effect, the earth would be about 60 degrees colder than it is now. Basically the greenhouse effect is water vapor and CO2 in the atmosphere that insulates the earth and retains some of the radiant heat from the sun. For the last 100,000 years or so, CO2 levels in the atmosphere have been fairly constant, below 280 parts per million(7). You can see in this graph (figure 1.5) that goes back to the year 1000 A.D., there is a level line along the bottom around 280 ppm. As we get into the 19th century and the industrial revolution, CO2 levels are going up very very steeply. They've gone up 30% in the last century, we are now at 360 ppm(8). This has never happened before. If you add onto this the fact that the population is expected to double in the next century, and many developing nations like China with huge coal reserves are rapidly industrializing, then you can see why this CO2 projection is headed straight off the graph. Atmospheric CO2 levels are expected to double in the next century. Scientists tell us that we're seeing global warming now. Figure 1.6 shows the temperature record going back to the year 1400, based partially on ice-core measurements. The horizontal line is the mean temperature for that time period(9). You can clearly see what the trend is, it's going up. The 1980is were the hottest decade on record, 1990-95 was the hottest half decade on record. 1990, 1995, 1997, and 1998 were the hottest years on record. |
Figure 1.1 - Prospective Clients Requesting Green Buildings New England Aquarium |
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Figure 1.2 - U.S. Energy Use by Sector
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Figure 1.3 - Environmental Impacts of Buildings
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Figure 1.4
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Figure 1.5 Historical and Projected CO2 Levels
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Figure 1.6 Historical Global Temperature variation from 1400 to 1997 from the National Climatic Data Center / NES-DIS/ NOAA  |
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| Each of the last 15 months has set a record for being the hottest ever for that month (figure 1.7). These are records going back 140 years since temperature records have been taken(10). Global temperatures have already increased about one degree, and are expected to increase another 3-5 degrees in the next century, this is a consensus estimate. Now 3-5 degrees, plus the one degree we've already had doesn't sound like a whole lot, but the last ice age was only about 8 degrees colder. It's a significant amount if you consider that it is a global average. Certain regions will warm much greater than that(11). | ||||||||||||||||||||||||
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Figure 1.7 Average
global temperature vs. previous record for each month May
1997 - October 1998
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Impacts of Global Warming I'll try and spare you most of the details, but I have to mention a few. Sea level has risen around eleven inches in the last century and is expected to go up another 22 inches in the next century. This is expected to flood about 5,000 square miles including a large percentage of our wetlands which will have a significant impact on our aquatic ecosystems, and perhaps on our aquarium business. The other issue is that these changes are happening much quicker than happened in previous natural climate shifts, some scientists estimate that it is happening 10-100 times quicker than the normal rate of change when we've had other climate shifts. There is a lot of concern among scientists that the ecosystems will not be able to migrate quickly enough to keep up, especially ecosystems that are hemmed in by a specific geographic boundary such as the Everglades or Glacier National Monument. At higher latitudes it is expected to more warm much more, and more quickly. Alaska has already warmed up about 5 degrees, the glaciers are retreating very quickly, and the permafrost is thawing. As the permafrost thaws, the water collects on the ground, turns to swamp, and kills the trees, as the ground melts it collapses and the trees lean over in what's called a drunken forest(12). Ocean temperatures have also been the warmest on record last year. A number of scientists at the Buenos Aries conference on climate change have attributed this to Global Warming and reported that it has killed most of the coral reefs in the Indian Ocean and in parts of the Pacific Ocean(13). EPA scientists have ranked environmental risks into three broad categories (figure 1.8). The things that we normally think of as the most important environmental issues such as oil spills or nuclear power plant disasters are from their point of view the least important. It is the impacts that have a global scale that are of most concern, including global warming(14). The Role of Cement and Flyash So the question is what can we do about all this? Well, we can ride the bus and turn back our thermostats and so forth, but those impacts are relatively small and require large numbers of people to make a big difference. Most of us in this room, however, have an incredible opportunity in that we design buildings. Professionally we can have a tremendous impact by carefully designing and specifying our buildings, an impact literally 1,000is of times larger than we can ever have in our personal lives. One piece of this puzzle is to use more flyash in our concrete. I'll leave most of this to others to talk about, but basically flyash is a waste product from coal burning power plants. About 75% of it is currently landfilled, this amounts to about 26 cubic miles. It has been successfully used for a long time. It was used in the concrete for the dome of the Pantheon 2,000 years ago(15) and it's still there (figure 1.9). Louis Kahn used it in the concrete for the Salk Institute, and got some beautiful concrete. A lot of specs I've seen in the Bay Area (figure 1.10) restrict flyash use to around 15%, its been creeping up a little bit. Cal-Trans now requires a minimum of 25% flyash in their standard spec and allows up to 35% which is double what many common specs permit. CANMET in Canada has been pioneering the use of high volume flyash including a seven story office building that used 55-60% class F flyash(16). Here locally the Sonoma State Environmental Technology Building which is under construction uses concrete with 25% flyash plus 25% ricehull ash. We have several people here tonight that worked on this project including Loring Willie at Degenkolb Engineers & Bruce King, George Beeler at AIM Associates is the architect. So, the question is can this make a difference? Well, we took a few projects from our office, and calculated how much concrete they used, and converted it to CO2 emissions. This is the Napier Residence (figure 1.11), Glennis Briggs is in the audience, she is the architect on this project. The building uses about 160 CY of concrete, and each CY is responsible for about 631 pounds of CO2, for a total of 100,000 pounds of CO2 emissions. To give some sense of scale to this, an average car releases about 1 pound of CO2 per mile driven(17), so this house is equivalent to about 100,000 vehicle miles. On a larger scale we have the Long Beach Aquarium (figure 1.12), and I know we have a number of architects and engineers here that worked on this project. It has about 24,000 CY of concrete, which is around 15,000,000 pounds of CO2, or around 15,000,000 vehicle miles. George Loisos was calculating what these distances are and determined that for the Long Beach Aquarium it was about 625 trips around the world or 31 round trips to the moon, the residence is about 4 circumnavigation's of the globe. [Audience: "I hope you're going to do that on a concrete road"] When I first did these calculations, I was astonished at the size of these numbers. And they are sobering. But on the other hand, you can flip this around and see it as an incredible opportunity. Many of us in this room, we personally can make a huge difference just on the buildings that we design. Many of are in a position to change our specs, or work to change our standard office specs, or at least educate those in our offices who make these decisions. We can participate in a testing and demonstration program which can lead the way for the rest of the country. In the end, this is an optimistic realization. We can, by replacing a large percentage of the cement in our concrete, perhaps 50%, we can cut these impacts in half. And who knows where we'll go after that. From my point of view this is an incredible opportunity that we should all work to take advantage of. Will we get there in one step? Some of us will, but many of us will not. But can we do some research and testing, some demonstration projects and so forth that can make it happen? I think we can. Just here in this room tonight we have some of the best engineers, architects, and concrete experts anywhere in the country. I'm certain that if we work together we can do it. I've talked to people all over the U.S. and Canada that are interested in this issue, and if a few of us here tonight can lead the way, we can change the way concrete is made throughout the entire country. |
Figure 1.8 EPA Risk Assessment
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Figure 1.9 The dome of the Pantheon uses concrete made with pozzolans similar to flyash
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Figure 1.10 Percentage of flyash permitted in four specifications
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Figure 1.11 This average sized residence contains 160 CY of concrete.
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Figure 1.12 The Long Beach Aquarium contains 24,000 CY of concrete.
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References
Click on a number to return to its position in the body of the article.
1. Energy Use by Sector
2. Levin, H., A. Boerstra, and S. Ray, 1995, Scoping U.S. Buildings Inventory Flows and Environmental Impacts in Life Cycle Assessment, Presented at Society for Environmental Toxicology and Chemistry (SETAC), Impacts assessment work group meeting, Alexandria, Virginia.
3. Cement and Concrete: Environmental Considerations, Environmental Building News, Vol. 2, Number 2, March/April 1993.
4. Malhotra, V. M., Role of Supplementary Cementing Materials in Reducing Greenhouse Gas Emissions, submitted for publication in Concrete International, 1998.
6. 1995 Intergovernmental Panel on Climate Change (IPCC), working Group II. United Nations Advisory Panel to Global Climate Change Negotiations; and Richard Wolfson, Lecture Series Entitled: Energy and Climate: Science for Citizens in the Age of Global Warming, Middlebury College.
7. United States Environmental Protection Agency Global Warming Web Site: www.epa.gov/oppeoee1/globalwarming; see also reference 6 above.
8. Wolfson, Richard, Lecture Series Entitled Energy and Climate: Science for Citizens in the Age of Global Warming, Middlebury College.
9. EPA Global Warming Website.
10. National Climatic Data Center/National Oceanic and Atmospheric Administration Website: www.ncdc.noaa.gov/ol/climate/research/1998/oct/18record.
11. EPA Global Warming Website.
12. Stevens, William K., Dead Trees and Shriveling Glaciers as Alaska Melts, The New York Times, Science Times, August 18, 1998.
13. Woodard, Colin, Caribbean's Endangered Reefs, San Francisco Chronicle, Nov. 16, 1998.
14. Adapted from Reducing Risk: Setting Priorities and Strategies for Environmental Protection, The Report of the Science Advisory Board Relative Risk Reduction Strategies Committee to the EPA, September 1990; see Environmental Building News, September/October 1995.
15. Sir Banister Fletcher's A History of Architecture, Eighteenth Edition, Revised by J.C. Palmes, 1975, p. 268.
16. Langley, Wilbert, and Gordon Leaman, Practical Uses for High-Volume Fly Ash Concrete Utilizing a Low Calcium Fly Ash, in Flyash Silica Fume, Slag and Natural Pozzolans in Concrete, Volume 1, edited by V.M. Malhotra, Sixth CANMET International Conference, ACI SP 178.
17. Personal Communication with J. Moore, Greenhouse Gas Inventory Specialist with the Greater Vancouver Regional District, British Columbia.