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Trash or treasure? Putting coal combustion waste to work.

Tenenbaum DJ - Environ. Health Perspect. (2009)

View Article: PubMed Central - PubMed

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Approximately 33% of the gypsum that was used to make U.S. wallboard in 2008 was FGD gypsum, says Michael Gardner, executive director of the Gypsum Association, a trade group, who adds, “Only cutbacks in construction due to the recession have prevented the use of even more FGD gypsum. ” The heat of coal combustion eliminates compounds such as dioxins and polycyclic aromatic hydrocarbons that could form during combustion, according to “PAHs and Dioxins Not Present in Fly Ash at Levels of Concern,” a presentation by Lisa Bradley and colleagues at the 2009 World of Coal Ash meeting, a biennial conference organized by the ACAA and the University of Kentucky Center for Applied Energy Research... Can they leach from construction materials as well? For safety purposes, LifeTime Composites tests fly ash before using it in its LifeTime Lumber product. “We do not want to run the risk of having a product that exceeds limits [for heavy metals] in our system,” says Mahler. “Our process encapsulates the ash [in polyurethane] to the point where no heavy metals are released in any way to humans, pets, or plants. ” At the 2007 World of Coal Ash meeting Liu reported on a test simulation of heavy rain at a construction site where Greenest Bricks were stored. “We compared the water sample to the EPA standard for drinking water, and every item—lead, selenium, and so on—was 10, 100, or 1,000 times less than the standard,” he says... Senior and colleagues published in the July 2009 issue of the Air & Waste Management Association’s EM magazine. “The wide variation in mercury loss (2 to 55%) from seven FGD gypsum samples [taken from five plants] was attributed to the different conditions under which each gypsum sample was generated,” the authors wrote. “Any remaining mercury in the finished FGD-wallboard could be released during use or subsequent disposal or recycling of the wallboard. ” The authors noted that research is under way at the EPA to evaluate the fate of mercury and other metals through each stage of wallboard’s life cycle... Heavy metals tend to stay put in conventional concrete, says Kosmatka, who cites a 2007 PCA-financed study of concrete that passed the EPA’s toxicity characteristic leaching procedure (TCLP) test despite containing cement carrying up to 0.1% lead, cadmium, and chromium... The study, titled Comparison of Mortar Leaching Methods, concluded that cement containing less than 500 mg/kg of these elements would even be usable in drinking water systems... Harold Walker, an associate professor of civil and environmental engineering at The Ohio State University, measured the release of airborne mercury while concrete containing fly ash cured for 28 days. “Less than 0.022% of the total quantity of mercury present from all mercury sources in the concrete was released during the curing process,” Walker and colleagues wrote in volume 23, issue 4 (2009) of Energy and Fuels, “and therefore, nearly all of the mercury was retained in the concrete. ” The authors noted that the addition of powdered activated carbon appeared to play an important role in reducing the total amount of mercury released... They also pointed out that their calculations did not address the potential release of mercury if the concrete were eventually crushed and landfilled... The degree of heavy metal leaching from highway applications “depends on the chemical character of the ash, the hydrologic setting, and whether the surface will be concrete or asphalt,” Benson says. “In almost all cases, the heavy metals get bound up with minerals after they move out of the CCW layer [and into soil or subsoil]. ” The EPA requirement that many electric generators remove mercury from their chimney emissions poses twin challenges for fly ash recycling... First, depending on the mercury removal technique used, the amount of mercury in the fly ash rises by up to 184 times, according to tests reported by Amy Dahl of Frontier GeoSciences at the 2008 MEGA Symposium, a meeting sponsored by the EPA, the Department of Energy, the Electric Power Research Institute, and the Air & Waste Management Association... Evans, a former EPA official who has testified before Congress in favor of some types of CCW recycling, favors a middle-ground option: designating the waste as hazardous when it is disposed but not when recycled into certain products, including cement and wallboard... Recycling can attenuate the overall greenhouse impact and the hazards associated with ash storage, but millions of tons of CCW are now put to “beneficial uses” that, absent adequate monitoring, raise environmental questions... Increased recycling may reduce more questionable forms of “beneficial use” along with the risks and environmental costs of waste disposal... Pounds takes another view: “The coal will be consumed to produce power regardless of the end use or designation of the [CCW]—and the challenge of replacing coal power with cleaner alternatives will remain urgent... The alternative—to simply landfill fly ash and to not take the significant environmental benefits from substituting fly ash for cement and other applications—would be irresponsible. ” Evans makes a similar point. “The increased disposal costs brought by national minimum standards for coal ash landfills and closure of unsafe coal ash impoundments will greatly increase the incentive for power plants to recycle, not dispose of the wastes,” she says. “Federal regulations that require greater scrutiny and monitoring of beneficial reuse applications will go a long way toward promoting safe recycling and eliminating the reuses that pose serious threats to health and the environment. ”

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A retrofit of the San Francisco Oakland Bay Bridge involves more than 30 different concrete mixes, each of which confers specific advantages. For instance, according to the U.S. EPA, concrete containing more than 50% fly ash resists the cracking and corrosion associated with seawater.Reuters/Robert Galbraith
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f1-ehp-117-a490: A retrofit of the San Francisco Oakland Bay Bridge involves more than 30 different concrete mixes, each of which confers specific advantages. For instance, according to the U.S. EPA, concrete containing more than 50% fly ash resists the cracking and corrosion associated with seawater.Reuters/Robert Galbraith


Trash or treasure? Putting coal combustion waste to work.

Tenenbaum DJ - Environ. Health Perspect. (2009)

A retrofit of the San Francisco Oakland Bay Bridge involves more than 30 different concrete mixes, each of which confers specific advantages. For instance, according to the U.S. EPA, concrete containing more than 50% fly ash resists the cracking and corrosion associated with seawater.Reuters/Robert Galbraith
© Copyright Policy - public-domain
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2801204&req=5

f1-ehp-117-a490: A retrofit of the San Francisco Oakland Bay Bridge involves more than 30 different concrete mixes, each of which confers specific advantages. For instance, according to the U.S. EPA, concrete containing more than 50% fly ash resists the cracking and corrosion associated with seawater.Reuters/Robert Galbraith

View Article: PubMed Central - PubMed

AUTOMATICALLY GENERATED EXCERPT
Please rate it.

Approximately 33% of the gypsum that was used to make U.S. wallboard in 2008 was FGD gypsum, says Michael Gardner, executive director of the Gypsum Association, a trade group, who adds, “Only cutbacks in construction due to the recession have prevented the use of even more FGD gypsum. ” The heat of coal combustion eliminates compounds such as dioxins and polycyclic aromatic hydrocarbons that could form during combustion, according to “PAHs and Dioxins Not Present in Fly Ash at Levels of Concern,” a presentation by Lisa Bradley and colleagues at the 2009 World of Coal Ash meeting, a biennial conference organized by the ACAA and the University of Kentucky Center for Applied Energy Research... Can they leach from construction materials as well? For safety purposes, LifeTime Composites tests fly ash before using it in its LifeTime Lumber product. “We do not want to run the risk of having a product that exceeds limits [for heavy metals] in our system,” says Mahler. “Our process encapsulates the ash [in polyurethane] to the point where no heavy metals are released in any way to humans, pets, or plants. ” At the 2007 World of Coal Ash meeting Liu reported on a test simulation of heavy rain at a construction site where Greenest Bricks were stored. “We compared the water sample to the EPA standard for drinking water, and every item—lead, selenium, and so on—was 10, 100, or 1,000 times less than the standard,” he says... Senior and colleagues published in the July 2009 issue of the Air & Waste Management Association’s EM magazine. “The wide variation in mercury loss (2 to 55%) from seven FGD gypsum samples [taken from five plants] was attributed to the different conditions under which each gypsum sample was generated,” the authors wrote. “Any remaining mercury in the finished FGD-wallboard could be released during use or subsequent disposal or recycling of the wallboard. ” The authors noted that research is under way at the EPA to evaluate the fate of mercury and other metals through each stage of wallboard’s life cycle... Heavy metals tend to stay put in conventional concrete, says Kosmatka, who cites a 2007 PCA-financed study of concrete that passed the EPA’s toxicity characteristic leaching procedure (TCLP) test despite containing cement carrying up to 0.1% lead, cadmium, and chromium... The study, titled Comparison of Mortar Leaching Methods, concluded that cement containing less than 500 mg/kg of these elements would even be usable in drinking water systems... Harold Walker, an associate professor of civil and environmental engineering at The Ohio State University, measured the release of airborne mercury while concrete containing fly ash cured for 28 days. “Less than 0.022% of the total quantity of mercury present from all mercury sources in the concrete was released during the curing process,” Walker and colleagues wrote in volume 23, issue 4 (2009) of Energy and Fuels, “and therefore, nearly all of the mercury was retained in the concrete. ” The authors noted that the addition of powdered activated carbon appeared to play an important role in reducing the total amount of mercury released... They also pointed out that their calculations did not address the potential release of mercury if the concrete were eventually crushed and landfilled... The degree of heavy metal leaching from highway applications “depends on the chemical character of the ash, the hydrologic setting, and whether the surface will be concrete or asphalt,” Benson says. “In almost all cases, the heavy metals get bound up with minerals after they move out of the CCW layer [and into soil or subsoil]. ” The EPA requirement that many electric generators remove mercury from their chimney emissions poses twin challenges for fly ash recycling... First, depending on the mercury removal technique used, the amount of mercury in the fly ash rises by up to 184 times, according to tests reported by Amy Dahl of Frontier GeoSciences at the 2008 MEGA Symposium, a meeting sponsored by the EPA, the Department of Energy, the Electric Power Research Institute, and the Air & Waste Management Association... Evans, a former EPA official who has testified before Congress in favor of some types of CCW recycling, favors a middle-ground option: designating the waste as hazardous when it is disposed but not when recycled into certain products, including cement and wallboard... Recycling can attenuate the overall greenhouse impact and the hazards associated with ash storage, but millions of tons of CCW are now put to “beneficial uses” that, absent adequate monitoring, raise environmental questions... Increased recycling may reduce more questionable forms of “beneficial use” along with the risks and environmental costs of waste disposal... Pounds takes another view: “The coal will be consumed to produce power regardless of the end use or designation of the [CCW]—and the challenge of replacing coal power with cleaner alternatives will remain urgent... The alternative—to simply landfill fly ash and to not take the significant environmental benefits from substituting fly ash for cement and other applications—would be irresponsible. ” Evans makes a similar point. “The increased disposal costs brought by national minimum standards for coal ash landfills and closure of unsafe coal ash impoundments will greatly increase the incentive for power plants to recycle, not dispose of the wastes,” she says. “Federal regulations that require greater scrutiny and monitoring of beneficial reuse applications will go a long way toward promoting safe recycling and eliminating the reuses that pose serious threats to health and the environment. ”

Show MeSH