October 25, 2014

Energy

Energy on Ice

The side effects of the Gulf oil spill could include pushing a potential new source of energy into the spotlight

Mark R. Howard | 9/1/2010

The Gulf of Mexico has a leaky bottom. Each year, about 15 million gallons of oil and other hydrocarbons ooze out of fissures in the seabed called "oil seeps." Unlike the gusher unleashed by the failure of the Deepwater Horizon well, the leaks from the seeps are small, distributed widely across the floor of the Gulf and don't harm the underwater ecosystem.

An oceanographer at Florida State University, Ian MacDonald, uses images from special cameras and satellite photos to chart the oil seeps and to estimate how much oil is being discharged. Using satellite data, he was among the first scientists to question BP's estimates of how much oil was escaping from its damaged well.

FSU professor Ian MacDonald
FSU professor Ian MacDonald is an expert in methane hydrates, substances that form when methane and water, under pressure, combine and create an ice-like substance. MacDonald says the Gulf of Mexico "is one of the few places where you can actually see hydrates exposed on the seafloor."?
[Photo: Ray Stanyard]

MacDonald is also an expert in what happens to the oil and gas that leaks from the seeps, including the formation of substances called methane hydrates.

He explains that methane, the gas that's the main component in the natural gas we use to cook and heat, is produced naturally in the Earth's crust. Typically, methane remains trapped deep underground. In many coastal areas, however, some of the gas leaks out along with the oil from the seeps.

In shallow, warmer waters, the methane rises through the water and dissipates into the atmosphere. At depth, however, cold temperatures and high pressure trap some of the methane in a web of water molecules on or just under the seafloor, creating ice-like substances called methane hydrates. MacDonald says the hydrates look like frozen snow or hard white ice; if more oil is mixed in, the hydrate deposits look yellow to dark brown.

The Gulf, MacDonald says, "is one of the few places where you can actually see hydrates exposed on the seafloor."

Scientists have understood the basic chemistry of methane ice, as hydrates are also called, since the 1800s. But it wasn't until recently that they began to appreciate how much methane hydrate is distributed in coastal ocean sediments and permafrost around the world — and there are very compelling reasons for them to want to learn more about where it forms and how much there is.

"If we can produce gas from the deep ocean and replace coal, then that's a real win for the planet," says Ian MacDonald, an expert in methane hydrates.

For one, methane hydrates represent "the Earth's biggest potential source of hydrocarbon energy," according to the U.S. Department of Energy — more carbon, possibly, than is contained in all the other known coal, gas and oil on the planet and enough to meet global demand for gas for hundreds of years. A 2005 estimate by the U.S. Geological Survey puts the potential resources of methane hydrates in the U.S. alone at the equivalent of around 200,000 trillion feet of natural gas.

Mass Spectrometer
Scientists were taking measurements in the Gulf — coincidentally not far from the Deepwater Horizon explosion — in 2009, looking for the flow of methane from deepwater hydrates. [Photo: SRI]
In addition to deposits on and beneath the seafloor in the Gulf and off the Carolina coast, there are huge amounts of methane hydrates onshore, trapped near the surface in the frigid permafrost of Alaska's North Slope. "If only 1 percent of that gas can be recovered, the nation would more than double its natural gas resources," according to the USGS.

The other side of that coin is that while methane emits much less carbon dioxide than gasoline or coal, it's still a potent greenhouse gas. Some fear that even without any methane-mining, current climate trends — rising temperatures in the permafrost, for example — could release masses of methane into the atmosphere that could bring huge climate changes. Some scientists believe — there is no consensus on the topic — that massive methane releases are responsible for mass extinctions millions of years ago that have been revealed by fossil and geologic studies.

Tags: Energy & Utilities

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