Fire and ice: methane hydrates energy solution, or worst idea ever?
Global reserves of methane hydrates are estimated at 100 times greater than conventional natural gas resources. In the US alone, the Department of Energy (DOE) reports that if just one percent of domestic hydrate reserves were recoverable, it would more than double the nation's remaining natural gas supplies. This is big news for a country that is projected to increase its demand for natural gas by 40 percent by the year 2020.
Unfortunately, methane hydrate deposits are inherently unstable. Warming seawater could melt them, leading to rapid global warming. The Intergovernmental Panel on Climate Change (IPCC), a partnership between the World Meteorological Organization and the United Nations Environment Programme, says that climate change during the 21st century has the potential to lead to future large-scale and possibly irreversible changes in Earth systems resulting in impacts at continental and global scales. One of the proposed mechanisms of climate change is the melting of methane hydrates.
Methane hydrates are formed in two geologic settings: in permafrost regions where cold temperatures dominate within shallow sediments, and beneath the sea at depths greater than 1,500 feet. The hydrate layer, which may be several meters thick, often forms a seal that keeps free flowing methane gas below from seeping towards the surface.
In permafrost, deeply buried organic matter is heated from the Earth's core and rises until it finds a zone where the combination of pressure and temperature favors the formation of methane hydrates.
In the sea, bacteria generate the methane as they break down organic matter. As the gas moves through the sediments, high pressure squeezes chilled water and methane molecules into a solid. These seafloor methane hydrates, found along outer continental margins worldwide, are the most abundant kind.
It is in the deep-water seafloor where methane hydrates provide energy for newly discovered forms of marine life. Ice worms burrow into the gas hydrates, forming colonies hundreds of animals thick. Off the coast of Chile, a purportedly new species of clam has been found. More deep-water species are likely to follow.
Methane hydrates were first discovered in 1810. In the 1930s, engineers identified methane hydrates as the stuff responsible for clogging natural gas pipelines in colder regions.
Methane hydrates remained a nuisance and scientific oddity until 1964, when the Soviets realized the potential of a major hydrate deposit discovered in Siberian permafrost. This discovery initiated a worldwide search for more deposits. In the 1970s, methane hydrates were found in the ocean floor. The world took notice.
The US Geological Survey (USGS) has been investigating methane hydrates since 1979. In 1981, a National Science Foundation-sponsored drilling program unexpectedly retrieved a core sample containing methane hydrates off the coast of Guatemala. Methane hydrates had been encountered before; this time researchers were able to retrieve an intact sample. And so began America's search for this energy Grail.
Beginning in 1982, DOE spent over $8 million researching the distribution and physical properties of methane hydrates. In 1997, DOE began formulating a multi-agency natural gas hydrate research and development program. After small outlays for research and development over the next two years, DOE allocated half a million dollars for methane hydrate research in 1999. The following year DOE requested almost two million dollars for continued research. Congress increased the appropriation to $2.96 million.
This activity culminated with President Clinton signing into taw the Methane Hydrate Research and Development Act of 2000, authorizing $49 million over the next five years. The Act calls for a consortium of governmental agencies, universities, and oil companies to research methane hydrate's role in oil and gas drilling safety, global climate change, seafloor stability, and future energy supplies. One of the main goals of the Act is to achieve commercial production of natural gas from methane hydrates by 2015. Funding ran out in October, 2005.
Enough to go around
Worldwide methane hydrate reserves are estimated by the USGS to be about twice the reserves of all other fossil fuels on earth. Estimates of nearly 400 quintillion cubic feet compare to five quadrillion cubic feet of known natural gas reserves. Natural gas accounts for a quarter of the world's energy consumption, and there is roughly a 60-year supply.
A USGS survey estimates US methane hydrate reserves at 200 quintillion cubic feet. Large reserves have been found in Alaska, along the west coast from California to Washington, the East Coast--particularly off the Carolinas--and in the Gulf of Mexico.
Oil and natural gas currently provide 62 percent of the US's energy and almost 100 percent of transportation fuel. Sixteen percent of US electricity is generated by natural gas. America now imports 60 percent of its oil.
On its National Energy Policy Web site, the White House estimates that by 2020 natural gas demand will increase by half, while demand for oil will grow by one third. More dramatically, the amount of natural gas used to generate electricity is projected to triple in the same time frame.
Worldwide production of methane hydrates will not be economically feasible for another 30 to 50 years, predict USGS scientists, except for those countries where strong economic or political motivations drive research. These countries could begin production within a decade.
The US's oil supply is expected to decline over the next two decades. Energy researchers believe current US reserves of natural gas are sufficient to meet the rapidly growing demand over the next two decades. After that, natural gas demand will likely outstrip domestic production leaving the US either importing even more from foreign producers--if they have it--or sharply curtailing energy use. Some see methane hydrates as offering the possibility of a few more decades of fuel.
The bad news is that methane is a powerful greenhouse gas: It traps heat 20 times more effectively than carbon dioxide. Methane hydrates bind approximately 3,000 times as much methane as is now in the atmosphere. A huge accidental release of methane hydrates could dramatically warm the planet.
Such a dramatic temperature increase could start positive climate feedback loops. When ice melts, more land and open water is exposed to the sun's rays. Land and water absorb more solar energy than does ice, warming the planet further.
As permafrost melts it releases more carbon dioxide and methane into the atmosphere, further contributing to the greenhouse effect. As the seas warm, additional methane hydrate deposits may be destabilized, causing further releases.
Methane hydrates are being investigated as a possible cause of at least three major warming episodes and several smaller fluctuations in the history of life on Earth.
Approximately 600 million years ago, the Earth was almost completely covered in ice. Even the oceans may have frozen over. With so much of its surface reflecting the sun's heat, the earth remained persistently cold. Until recently, scientists have believed that a release of carbon dioxide may have warmed the earth from its deep freeze. However, in 2003, scientists at the University of California, Riverside reported evidence found in China that points to a release of two to four trillion tons of methane hydrates as a possible cause of the warming. This may have been the biggest release of methane in the Earth's history.
About 55 million years ago, between the Palaeocene and Eocene epochs, a period of extreme global warming occurred--an event known as the Palaeocene-Eocene thermal maximum. Some geoscientists hypothesize that methane hydrates decomposed on a massive scale, warming the planet by more than 5[degrees]C. This would have warmed even the deep sea, making the ocean significantly more acidic. Off the coast of Africa, scientists have found evidence of a period lasting more than 50,000 years in which the ocean became so acidic that it dissolved the calcite shells of many bottom-dwelling organisms, leading to their extinction. Recovery took 100,000 years.
Another hypothesis suggests that excessive methane in the atmosphere caused the Permian extinction 248 million years ago, in which 90 percent of all plants and animal species perished. Some think that the methane combined with oxygen in the atmosphere, leaving only 12 percent atmospheric [O.sub.2], as opposed to the 20 percent we now enjoy--equivalent to being at an elevation of 16,500 feet.
Several warming events in more recent times also point to large releases of methane hydrates into the atmosphere. Scientists have evidence of sudden massive eruptions of methane hydrates off the coast of Santa Barbara, California during the last glacial period 70,000 to 12,000 years ago.
Yet these hypotheses remain controversial. Some disagree whether methane hydrates have had any role in raising global temperatures. Dr. Keith A. Kvenvolden, Emeritus Organic Geochemist at the USGS, says "I think that methane hydrates, if anything, have ... buffered any sort of changes that have happened in terms of the global climate."
Whichever proves true, says climate change researcher James P. Kennett at the University of Santa Barbara, there is "no question methane hydrates are a player" in global climate conditions.
It is known that changes in either pressure or temperature can melt hydrates. Computer modeling shows the oceans need warm only a few degrees to set methane hydrate release in motion. One possibility is that as the earth warmed after an ice age, rising seas submerged methane-hydrate-containing permafrosts. The water melted the hydrates, releasing their methane.
Melting at the base of the hydrate layer can destabilize sloping seafloors. This can lead to massive submarine landslides, such as those found at Blake's Ridge off the North Carolina coast, where the ocean floor is pocked with huge craters formed by methane released from hydrates. Other evidence of landslides exists off the coasts of Alaska, British Columbia, Norway, and Africa. Such seafloor collapse, of course, could spawn tsunamis.
Other triggering possibilities include changes in ocean currents that alter bottom water temperatures, and erosion at continental slopes. One trigger of special concern is oil and gas platforms sitting atop hydrate reserves, as the search for new oil and gas sources moves into deeper waters where thick layers of hydrate lie near the seafloor surface. Hot fluids from deep within the earth coursing through pipelines may melt the hydrates and shift the seafloor, posing significant safety hazards to personnel, equipment, and the environment.
Most long-term climate change has occurred in sudden jumps, especially in the last 150,000 years. Geophysicists caution that this stepwise instability may provide a window into the consequences of current day global warming through greenhouse effects. Seemingly incremental change may build to a "breaking point," at which even the slightest event might trigger massive climate change.
The Arctic is particularly vulnerable to climate change. Arctic permafrost has warmed by 2[degrees]C in recent decades, and the extent of ice cover has decreased by 7 to 9 percent per decade since 1981. Some of the changes have been touted as positive, such as the lengthening of the Arctic navigation season and easier offshore drilling of oil and gas. But melting ice adds more flesh water to the oceans, potentially affecting ocean currents that bring heat from the tropics northward, making Northern Europe livable. Severe coastal erosion, flooding coastal wetlands, forests replacing large expanses of tundra and tundra vegetation moving into polar regions, increased insect outbreaks and forest fires, and a surge in animal diseases spreading to humans are other potential consequences of Arctic climate change.
"There are key areas that I would tend to be more concerned about, particularly in the Arctic Ocean," says Kennett. That's an area where gas hydrates ... occur at relatively shallow water depths on the margins around high-latitude continents. Those are potentially vulnerable to instability with even a one degree temperature warming of bottom waters. And we know the Arctic is warming up."
The Intergovernmental Panel on Climate Change (IPCC) says that global temperature increase--which in the current worst-case scenarios may amount to 6[degrees]C in this century--could result in increased death and illness in the aged and urban poor; range extensions of pests and disease vectors; intense precipitation increasing floods, landslides, avalanches, and mudslides; lower crop yields; decreasing water quantity and quality; and more wildfires. Increased tropical storm strengths and precipitation will result in increased disease epidemics, coastal erosion, and further damage to coastal ecosystems such as coral reefs and mangroves.
Where we stand today
Promising inventories of methane hydrates have been described in Alaska, Antarctica, the Canadian Arctic, India, the continental shelf off Japan, Nigeria, the South China Sea, Norway, Peru, and Australia. Most promising for the US are Alaska's North Slope, Blake's Ridge, and the Gulf of Mexico.
The first research site explored--Mallik, in the Canadian Northwest Territories--lies atop one of the most concentrated known terrestrial deposits of methane hydrate. In 1998, an international consortium drilled the first research well there. In March of 2002, the team made history by using heated water to melt trapped methane, showing that natural gas production from methane hydrates is feasible.
Off the coast of Japan, the first offshore well to test the potential of methane hydrates in the seafloor was drilled in 1999. A second round of drilling here took place in 2003. Japan may be the first country to produce methane from hydrates on a commercial basis. But the head of DOE's hydrate program has said that the US is determined to be the first to mine them.
Yet things are not always as they seem--some of the latest efforts have yielded disappointing results. The Gulf of Mexico has often been described as having an inexhaustible supply of methane hydrates. However, this year a research team from Georgia Tech, Rice University, and the Scripps Institution of Oceanography reported that the marine sediments in the Gulf are likely too warm and salty to hold the amount of methane hydrates once thought to exist there. The team has recommended that estimated reserves for the region be adjusted sharply downward.
Another highly touted reservoir of hydrates has been the permafrost in Alaska's North Slope. Although permafrost reservoirs are estimated to be only a fraction of those found offshore, drilling technology on the North Slope is well understood and the infrastructure is in place. In fact, the existing infrastructure is partly responsible for the methane hydrates push in the US. In April 2004, Gale A. Norton told the Juneau Chamber of Commerce that "the [Alaska] Pipeline may not be around that long unless we work to develop new fields to maintain sufficient amounts of oil to pay its operational expenses." Methane hydrate exploration is being conducted in the vicinity of existing oil operations.
Initial estimates put the suspected Alaskan hydrate find at over 590 trillion cubic feet. However, when the first dedicated hydrate well in Alaska, known as the Hot Ice No. 1 well, was drilled on the North Slope in February 2004, DOE subsequently announced that oil was found, but no methane hydrates.
Drilling continues, but the future of the nascent industry is uncertain. "I think there will be some production from hydrates, for example, in permafrost areas where they are a bit easier to get to," says Kvenvolden. "But to think about vast deposits that will be commercially exploitable, it's my opinion it just won't happen."
Carrie Black is an Earth Island Journal in tern.
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|Publication:||Earth Island Journal|
|Date:||Jan 1, 2006|
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