According to the IPCC, various technologies have been identified to enable and increase ocean CO2 storage. One suggested option is to store a relatively pure stream of CO2 that has been captured and compressed. The CO2 could be loaded onto a ship and injected directly into the ocean or deposited on the seafloor. CO2 loaded on ships could be either dispersed from a towed pipe or transported to fixed platforms feeding a CO2 lake on the seafloor. The CO2 must be deeper than 1.9 miles (3 km) because at this depth CO2 is denser than seawater.
Relative to CO2 accumulation in the atmosphere, direct injection of CO2 into the ocean could reduce maximum amounts and rates of atmospheric CO2 increase over the next several centuries. Once released, it is expected that the CO2 would dissolve into the surrounding seawater, disperse, and become part of the ocean carbon cycle.
C. Marchetti was the first scientist to propose injecting liquefied CO2 into waters flowing over the Mediterranean sill into the middepth North Atlantic, where the CO2 would be isolated from the atmosphere for centu-ries—a concept that relies on the slow exchange of deep ocean waters with the surface to isolate CO2 from the atmosphere. Marchetti's objective was to transfer CO2 to deep waters because the degree of isolation from the atmosphere increases with depth in the ocean. Injecting the CO2 below the thermocline would enable the most efficient storage. In the short term, fixed or towed pipes are the most viable methods for oceanic CO2 release because the technology is already available and proven.
One proposed option is to send the CO2 down as "dry ice torpedoes." In this option, CO2 could be released from a ship as dry ice at the ocean's surface. If CO2 has been formed into solid blocks with a density of 1.5tm-3, they would sink quickly to the seafloor and could potentially penetrate into the seafloor sediment.
Another method, called "direct flue-gas injection" involves taking a power plant fire gas and pumping it directly into the deep ocean without any separation of CO2 from the flue gas. Costs for this are still prohibitive, however.
It will be possible to monitor distributions of injected CO2 using a combination of shipboard measurement and modeling approaches. Current analytical monitoring techniques for measuring total CO2 in the ocean are accurate to about ± 0.05 percent. According to the IPCC, measurable changes could be seen with the addition of 99 tons (90 metric tons) of CO2 per 0.2 mi3 (1 km3). This means that 1.1 gigaton (1 metric gigaton) of CO2 could be detected even if it were dispersed over an area 2.4 million mi3 (107 km3 or 5,000 km x 2,000 km x 1 km), if the dissolved inorganic carbon concentrations in the region were mapped out with high-density surveys before the injection began.
There are several proposed methods of CO2 sequestration in the world's oceans. (IPCC)
In the case of monitoring the injection of CO2 into the deep ocean via a pipeline, several monitoring techniques are employed. At the point of entry from the pipeline into the ocean, an inflow plume is created of high CO2/low pH water extending from the end of the pipeline. The first monitoring array consists of sets of chemical, biological, and current sensors; and underwater cameras in order to view the end of the pipeline. An array of moored sensors monitors the direction and magnitude of the resulting plume around the pipe. Monitors are also set along the pipeline to monitor leaks. A shore-based facility provides power to the sensors and is able to receive real-time data. In addition, a forward system monitors the area and can provide data over broad areas very quickly. Moored systems monitor the CO2 influx, send the information to surface buoys, and make daily transmissions back to the monitoring facility via satellite.
As briefly touched on in chapter 2, a major project to pump CO2 underground in an ocean sequestration storage project is proposed for the ocean region just off the coast of the U.S. Pacific Northwest. In a report from the Seattle Times in July 2008, David Goldberg, a geophysi-cist at Columbia University's Lamont-Doherty Earth Observatory said, "It's hard to deny the size of the prize."
The research team involved believes it is possible to devise a system where CO2 emissions from power plants could be captured, liquefied, and pumped into porous basalt layers roughly 0.5 mile (0.8 km) beneath the ocean floor. They currently estimate there is enough storage space in the geologic formation to easily store more than a century's worth of CO2 emissions from the United States.
Taro Takahashi, also a scientist at Lamont-Doherty on the project, says, "In principle, the type of reservoir we propose on the ocean floor is one of the safest—if not the safest—way of storing liquefied CO2 for a long, long, time."
The proposal has met with some opposition, however. Some complain that the project will be too costly. Others raise questions about whether there will be possible ecological impacts or seismic hazards. The Juan de Fuca Plate, where the project would be located, is the tectonic plate that subducts under the North American continent and there have been questions raised as to whether the project could trigger earthquakes.
In response, the scientists on the project—David Goldberg and Taro Takahashi—say they have mapped out a 30,000-square-mile area (78,000 km2) that avoids the seismically active regions of the plate.
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Proposed carbon storage area
This area represents the site currently being considered for long-term carbon storage off the coast of the Pacific Northwest of the United States. The storage site is located well within the plate boundary to avoid instability.
Other critics are environmentalists who are critical of carbon sequestration in general, claiming that it is just a temporary measure delaying the immediate use of greener energy alternatives, which they feel is a better direction to take.
Angela Slagle, a marine geologist on the project concerned about wildlife habitat, said they would also avoid drilling new hydrothermal vents, where a myriad of unique sea life exists. Instead, the wells would be located more than 100 miles (161 km) from the coastline.
The research team also stresses that undersea basalts can trap and hold CO2 in several different ways, which in turn provide multiple layers of protection against leaks.
Kurt Zenz House, a Harvard researcher who was one of the first to propose undersea carbon storage, says, "Under immense pressure and cold temperature below the seafloor, CO2 forms a very dense liquid that is much heavier than seawater. In addition, gravity would prevent the liquefied gas from seeping upward, just as it prevents water in a well from flying into the air."
According to a report in MSNBC News in September 2006, Dr. James E. Hansen, a global warming expert at NASA/GISS, says the world has a 10-year window of opportunity to take positive action on global warming to avoid an impending catastrophe. He stresses that it is critical that governments worldwide adopt "an alternative scenario to keep CO2 emission growth in check and limit the increase in global temperatures to 1.8°F (1°C). I think we have a very brief window of opportunity to deal with climate change . . . no longer than a decade at the most."
In attendance at the Climate Change Research Conference, he stressed that if people continue to ignore the building evidence that global warming is happening and continue their lifestyles in a "business as usual" manner, atmospheric temperatures will rise 3.6-7.2°F (2-3°C) and "we will be producing a different planet." He also warns that under that warmer world drastic changes would be inevitable, such as the rapid melting of ice sheets (which would put most of Manhattan under water), prolonged droughts, severe heat waves, powerful hurricanes in new areas, and the "likely extinction" of 50 percent of the species on Earth.
MITIGATION—ONE STEP AT A TIME: HEADING IN THE RIGHT DIRECTION
According to an article in the New York Times in November 2007, the United States could shave up to 28 percent off the greenhouse gases it emits for a relatively inexpensive cost and a few small technological innovations. Most of the reductions could come about through steps that would also lower energy bills for both individuals and businesses and should be done just on the notion that they make good sense, according to energy experts at McKinsey and Company. Reported as well in a June 17, 2008, article on NewGeography.com, McKinsey and company developed a "blueprint" that shows how the United States could reduce those emissions by 2030 while "maintaining comparable levels of consumer utility." According to McKinsey, this means "no change in thermostat settings or appliance use, no downsizing of vehicles, home or commercial space and traveling the same mileage." They stress that to be effective and to avoid reducing the standard of living, efforts to reduce GHG emissions must be based upon sound economic analysis. The starting point is an evaluation of strategies to determine the least expensive in terms of cost per ton removed and the least invasive to the way people live and work.
Jack Stephenson, the director of the study, says most of the changes are simple: changes in lighting, and the heating and cooling of buildings would have a significant impact. As an extra incentive, they would also save energy payers money.
A major step consumers can make when purchasing items such as furnaces, stoves, ovens, washers, dryers, televisions, and computers is to
In a report issued by NASA, due to the increasing challenges caused by climate change and global warming, several scientists and policy makers in the United States have come together to take a part in the newly established United States National Assessment on the Potential Consequences of Climate Variability and Change—called the National Assessment for short.
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