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Earth Talk
Written by the Editors of E/The Environmental Magazine   
Monday, 18 October 2010 09:02

From Dear EarthTalk: What, if anything, fills the empty space underground created by the extraction of billions of gallons of oil? Could oil drilling be one of the causes of increasing amounts of land settling and sinkholes in oil rich areas? Can it cause earthquakes?   -- Linda Anderson, Sedona, AZ

"The U.S. Geological Survey cites
several cases throughout the 20th
century which they say demonstrate
how accelerated withdrawal of oil
and gas from some reservoirs can
lower land elevation, cause minor
earthquakes and activate faults
around oil fields.”Credit this image
to "Richard Masoner, courtesy Flickr."

The crude oil (and natural gas) we drill for the world over is, for the most part, stored in tiny pores within rock up to only about three miles deep in the Earth’s hugely dense crust. At such depths, the oil there is under fairly high pressure. When it is removed, other liquids—usually water—move in to take its place, equalizing the pressure in the process. Sometimes oil extractors pump water into one side of an oil field to push oil toward wells on the other side, and the water replaces the oil accordingly.

In cases where other liquids don’t move in, such as in the North Sea off The Netherlands, the porous rock layer that harbored the oil originally can collapse after extraction, causing slight amounts of land settling (known as “land subsidence”) in the rock layer surfaces above, but typically no more than a few tenths of an inch per year.

Here in the U.S., land subsidence induced by the large volume extraction of underground resources including oil and gas “is more common than most people realize,” according to the U.S. Geological Survey (USGS), a government agency which collects, monitors, analyzes and provides scientific understanding about natural resource conditions, issues and problems. Flat coastal plains and wetlands near sea level are most at risk from this potential side effect.

Written by the Editors of E/The Environmental Magazine   
Monday, 11 October 2010 08:17

Dear EarthTalk: Is there a way to utilize the energy in my dogs’ poop? I have three dogs and lots of poop and would like to dispose of it in a “greener” manner.          -- Mary C., Wallace, ID

No doubt creating a way to do so is possible, as large systems called anaerobic digesters (or biogas digesters) are often used in landfills to wring energy out of trash, as well as on some big farms and ranches where large amounts of cow manure provide plenty of feedstock. In such systems microbes generate methane gas—which can be captured and used for power—once they are set free on manure or trash. The economics of putting biogas digesters in landfills or big cattle operations can make the up-front expense tolerable—money can be made or saved by selling or utilizing the resulting power—but doing so in one’s back yard might be a different story.

Not to say it can’t be done: This past September artist Matthew Mazzotta, armed with a $4,000 grant from the Massachusetts Institute of Technology (MIT)—where he earned a master's degree in visual studies last year—created the ingenious Park Spark poop converter system that uses dog poop to power a gas lantern that illuminates a corner of the Pacific Street Dog Park in Cambridge, Massachusetts.

Written by the Editors of E/The Environmental Magazine   
Monday, 04 October 2010 08:33

Dear EarthTalk: What is “BPA” used in plastics, and why should I worry about it? Are there certain household items or food containers to avoid because of BPA? -- Tina Sillers, via e-mail

According to the U.S. Department of Health and Human Services (HHS), Bisphenol A (also known as BPA) is a chemical that has been in use for upwards of four decades in the manufacture of many hard plastic food containers, including baby bottles and reusable cups and the lining of metal food and beverage cans (including canned liquid infant formula). The agency further reports that “trace amounts of BPA can be found in some foods packaged in these containers.”

The non-profit Natural Resources Defense Council (NRDC) reports that “growing amount of scientific research has linked BPA exposure to altered development of the brain and behavioral changes, a predisposition to prostate and breast cancer, reproductive harm, diabetes, obesity and cardiovascular disease.” The group adds that more than 93 percent of Americans have some BPA in their bodies, primarily from exposure through food contamination and other preventable contact.

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