Tag Archive: environmental engineering

  1. Water Supplies Could be Strongly Affected by Climate Change


    Ground WaterIt’s no simple matter to figure out how regional changes in precipitation, expected to result from global climate change, may affect water supplies. Now, a new analysis led by MIT researchers has found that the changes in groundwater may actually be much greater than the precipitation changes themselves.

    For example, in places where annual rainfall may increase by 20% as a result of climate change, the groundwater might increase as much as 40%. Conversely, the analysis showed in some cases just a 20% decrease in rainfall could lead to a 70% decrease in the recharging of local aquifers—a potentially devastating blow in semi-arid and arid regions.

    But the exact effects depend on a complex mix of factors, including soil type, vegetation, and the exact timing and duration of rainfall events, so detailed studies will be required for each local region in order to predict the possible range of outcomes.

    The research was conducted by Gene-Hua Crystal Ng, now a post-doctoral researcher in MIT’s Department of Civil and Environmental Engineering (CEE), along with King Bhumibol Professor Dennis McLaughlin and Bacardi Stockholm Water Foundations Professor Dara Entekhabi, both of CEE, and Bridget Scanlon, a senior researcher at the University of Texas.

    The analysis combines computer modeling and natural chloride tracer data to determine how precipitation, soil properties, and vegetation affect the transport of water from the surface to the aquifers below. This analysis focused on a specific semi-arid region near Lubbock, Texas, in the southern High Plains.

    Predictions of the kinds and magnitudes of precipitation changes that may occur as the planet warms are included in the reports by the Intergovernmental Panel on Climate Change (IPCC)and are expressed as ranges of possible outcomes. “Because there is so much uncertainty, we wanted to be able to bracket the expected impact on water supplies under the diverse climate projections,” Ng says.

    “What we found was very interesting,” Ng continues. “It looks like the changes in recharge could be even greater than the changes in climate. For a given percentage change in precipitation, we’re getting even greater changes in recharge rates.”

    The team presented the results as a range of probabilities, quantifying as much as possible “what we do and don’t know” about the future climate and land-surface conditions, Ng says. “For each prediction of climate change, we get a distribution of possible recharge values.”

    For more study results, go to http://web.mit.edu/newsoffice/2008/agu-groundwater-1218.html.

    Read more about civil engineering and climate change at www.GraduatingEngineer.com.

  2. Clean, Carbon-Neutral Hydrogen on the Horizon

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    Hydrogen as an everyday, environmentally friendly fuel source may be closer than we think, according to Penn State researchers.“The energy focus is currently on ethanol as a fuel, but economical ethanol from cellulose is 10 years down the road,” says Bruce E. Logan, the Kappe professor of environmental engineering. “First you need to break cellulose down to sugars and then bacteria can convert them to ethanol.”Logan and Shaoan Cheng, research associates, suggest a method based on microbial fuel cells to convert cellulose and other biodegradable organic materials directly into hydrogen in a recent issue of the Proceedings of the National Academy of Sciences online.

    The researchers used naturally occurring bacteria in a microbial electrolysis cell with acetic acid-the acid found in vinegar. Acetic acid is also the predominant acid produced by fermentation of glucose or cellulose. The anode was granulated graphite, the cathode was carbon with a platinum catalyst, and they used an off-the-shelf anion exchange membrane. The bacteria consume the acetic acid and release electrons and protons creating up to 0.3 volts. When more than 0.2 volts are added from an outside source, hydrogen gas bubbles up from the liquid.

    “This process produces 288% more energy in hydrogen than the electrical energy that is added to the process,” says Logan.

    Water hydrolysis, a standard method for producing hydrogen, is only 50% to 70% efficient. Even if the microbial electrolysis cell process is set up to bleed off some of the hydrogen to produce the added energy boost needed to sustain hydrogen production, the process still creates 144% more available energy than the electrical energy used to produce it.

    For those who think that a hydrogen economy is far in the future, Logan suggests that hydrogen produced from cellulose and other renewable organic materials could be blended with natural gas for use in natural gas vehicles.

    “We drive a lot of vehicles on natural gas already. Natural gas is essentially methane,” says Logan. “Methane burns fairly cleanly, but if we add hydrogen, it burns even more cleanly and works fine in existing natural gas combustion vehicles.”

    The range of efficiencies of hydrogen production based on electrical energy and energy in a variety of organic substances is between 63% and 82%. Both lactic acid and acetic acid achieve 82%, while unpretreated cellulose is 63% efficient. Glucose is 64% efficient.

    Another potential use for microbial-electrolysis-cell produced hydrogen is in fertilizer manufacture. Currently fertilizer is produced in large factories and trucked to farms. With microbial electrolysis cells, very large farms or farm cooperatives could produce hydrogen from wood chips and then through a common process, use the nitrogen in the air to produce ammonia or nitric acid. Both of these are used directly as fertilizer or the ammonia could be used to make ammonium nitrate, sulfate or phosphate.

  3. California Flood Risks a “Disaster Waiting to Happen”

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    While flooding in California’s Central Valley is “the next big disaster waiting to happen,” water-related infrastructure issues confront almost every community across the country, according to engineers at the University of Maryland’s Clark School of Engineering in separate reports to California officials and in the journal Science.  An independent review panel chaired by Clark School Research Professor of Civil Engineering Gerald E. Galloway said the area between the Sacramento and San Joaquin river floodplains faces significant risk of floods that could lead to extensive loss of life and billions of dollars in damages. The panel’s report, “A California Challenge: Flooding in the Central Valley,” was commissioned by California’s Department of Water Resources.The panel pointed out that many of the area’s levees, constructed over the past 150 years to protect communities and property in the Central Valley, were poorly built or placed on inadequate foundations. Climate change may increase the likelihood of floods and their resulting destruction. The panel recommends that state and local officials take swift action to reduce the risk to people and the environment.The comprehensive flood-risk abatement strategy the panel recommends focuses on land-use planning and integration with other basin water management activities.

    “The challenges that California faces are widespread across the nation,” Galloway says. “The recent failure of a levee in a Nevada irrigation canal points out growing infrastructure problems.”

    Another civil engineering researcher from the Clark School, Dr. Lewis “Ed” Link, also served on the California panel.

    “I believe the State of California is taking a very enlightened approach to difficult issues,” Link states. “Supporting this study is a good example, as is their examination of risk for the entire Central Valley. They are looking strategically at measures that can create long-term solutions, a model for others to follow.”

    Galloway is also co-author of an article in the January 18, 2008 issue of Science-”Aging Infrastructure and Ecosystem Restoration”-which calls for the targeted decommissioning of deteriorated and obsolete infrastructure in order to support the restoration of degraded ecosystems.

    “As we move forward with infrastructure enhancement, we must consider how, in the process of carrying out these activities, we can restore and enhance the natural and beneficial functions of the floodplain, which can at the same time reduce flood losses,” Galloway explains.

    Link and Galloway were prominent figures in the review of the levee system around New Orleans after Hurricane Katrina devastated the area.

    Link served as director of the federal government’s Interagency Performance Evaluation Task Force, which evaluated the hurricane protection system around New Orleans. Galloway is a former brigadier general with the Army Corps of Engineers and has been part of the State of Louisiana review team looking at long-term plans for restoration of the Gulf Coast.