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Environmental Science Ch. 11 Section 3 to the end of the chapter
Terms in this set (29)
Crude oil is separated into a variety of products based on their different boiling points. After being heated, they are separated in a fractionation tower, which is about 30 m (100 ft) tall. The lower the boiling point, the higher the compounds rise in the tower.
Most important energy source
Although coal was the most important energy source in the United States during the early 1900s, oil and natural gas became increasingly important, particularly after the 1930s (In 2009, oil supplied approximately 37.3% and natural gas 24.7% of the energy used in the United States. In comparison, other U.S. energy sources included coal (20.9%), nuclear power (8.8%), and renewables (8.3%))
a systems approach in which natural gas is used to produce both electricity and steam; the heat of the exhaust gases provides the energy to make steam from water to be used for heating (see Figure 10.6). Cogeneration systems that use natural gas provide relatively clean and efficient electricity.
In contrast to petroleum, natural gas contains only a few different hydrocarbons: methane and smaller amounts of ethane, propane, and butane. Propane and butane are separated from the natural gas, stored in pressurized tanks as a liquid called liquefied petroleum gas, and used primarily as fuel for heating and cooking in rural areas. Methane is used to heat residential and commercial buildings, to generate electricity in power plants, and for a variety of purposes in the organic chemistry industry.
Natural gas as a fuel for trucks, buses, and automobiles offers significant environmental advantages over gasoline or diesel.
The main disadvantage of natural gas is that deposits are often located far from where the energy is used. Because it is a gas and is less dense than a liquid, natural gas costs four times more to transport through pipelines than crude oil. To transport natural gas over long distances, it is first compressed to form liquefied natural gas (LNG), then carried on specially constructed refrigerated ships
Natural gas is more plentiful than oil. Experts estimate that readily recoverable reserves of natural gas, if converted into a liquid fuel, would be equivalent to between 500 billion and 770 billion barrels of crude oil, enough to keep production rising for at least 10 years after conventional supplies of petroleum have begun to decline. However, if the global use of natural gas continues to increase as it has in recent years, then its supply will not last as long as current projections predict.
Large amounts of natural gas have recently been discovered in shale formations around the United States, and it is likely that similar deposits are waiting to be discovered elsewhere in the world. Removing shale gas can be more expensive and environmentally disruptive than the resources we have been accessing, but shale gas extraction is taking place in an increasing number of places around the country
Petroleum, or crude oil, is a liquid composed of hundreds of hydrocarbon compounds. During petroleum refining, the compounds are separated into different products—such as gases, gasoline, heating oil, diesel oil, and asphalt—based on their different boiling points (Figure 11.10). Oil is also used to produce petrochemicals, compounds in such diverse products as fertilizers, plastics, paints, pesticides, medicines, and synthetic fibers.
Underground geologic structures that tend to trap any oil or natural gas if it is present.
Geologists use a variety of techniques to identify structural traps that might contain oil or natural gas. One method is to drill test holes in the surface and obtain rock samples. Another method is to produce an explosion at the surface and measure the echoes of sound waves that bounce off rock layers under the surface. These data are interpreted to determine whether structural traps are present. However, many structural traps do not contain oil or natural gas.
Distribution of oil and natural gas deposits
Enormous oil fields containing more than half of the world's total estimated reserves are situated in the Persian Gulf region, which includes Iran, Iraq, Kuwait, Oman, Qatar, Saudi Arabia, Syria, the United Arab Emirates, and Yemen
Also known as "Hubbert's Peak," after the U.S. geologist who first developed the concept; it is the point at which global oil production has reached a maximum rate; by some estimates, Peak Oil is already past.
Some experts think that global oil production has already reached Peak Oil, the point at which the oil is being withdrawn at the highest possible rate. About 80% of current production comes from oil fields discovered before 1973, and most of these fields have started to decline in production. These analysts say the world must move quickly to develop alternative energy sources because the global demand for energy will only continue to increase even as production declines.
The Marcellus Shale
The Marcellus Shale may contain as much as 400 TCF of natural gas; many see this resource as an opportunity to reduce our reliance on imported energy resources and shift away from more environmentally damaging coal.
Shale gas is much more difficult to extract than is gas found above oil in sandstone deposits, where natural gas In contrast, gas must be freed from shale, which means that after a well is drilled, water is pumped down and used to break the shale apart. This process, called hydraulic fracturing (or fracking), uses high-pressure water to open or widen gaps that allow natural gas flow. Hydraulic fracturing produces wastewater with high concentrations of salts and hydrocarbons; the wastewater can also include toxic metals and radioactive uranium. While technologies are being developed to recycle the wastewater in place, the standard way to dispose of it now is to pump it back into the ground. In many places, the water must be trucked hundreds of kilometers to suitable disposal sites.
In order to extract gas from shale, a deep vertical well is drilled, with a horizontal hole bored into the rock layer of interest. Water is then pumped into the well. The pressure breaks natural gas and other hydrocarbons free from the shale; the gas is then extracted from the wellhead at the top. The well must be carefully lined where it crosses an aquifer (thin blue line near top) to prevent contamination.
Shale gas deposits are also often found much deeper than are the resources we have already accessed. Drilling, fracturing, and pumping are more intense, and wells must be located closer together than most current natural gas wells. Shale gas removal can be environmentally and socially disruptive, as shale gas removal wells are dug near communities. Shale gas extraction can be noisy and odorous; it can also increase traffic and adversely impact roads and bridges. Spills or leaks of hydraulic fracturing liquid can contaminate groundwater or surface water.
GLOBAL OIL DEMAND AND SUPPLY
One difficult aspect of the oil market is that the world's major oil producers are not its major oil consumers. In 2009 North America and Western Europe consumed 42.7% of the world's total petroleum (down from 50.0% in 2006), yet these same countries produced only 23.8% of the world's crude oil. In contrast, the Persian Gulf region consumed 8.1% of the world's petroleum but produced 28.9% of the world's crude oil.
Two sets of environmental problems are associated with the use of oil and natural gas
the problems that result from burning the fuels (combustion) and the problems involved in obtaining them (production and transport).
Pros and Cons of natural gas and oil
As with coal, the burning of oil and natural gas produces CO2. Every gallon of gasoline you burn in your automobile releases an estimated 9 kg (20 lb) of CO2 into the atmosphere. As CO2 accumulates in the atmosphere, it insulates the planet, preventing heat from radiating back into space. The global climate is warming more rapidly now than it did during any of the warming periods following the ice ages, and the environmental impact of rapid global climate change could cause substantial human suffering in the future.
Another negative environmental impact of burning oil is acid deposition. Although burning oil does not produce appreciable amounts of sulfur oxides, it does produce nitrogen oxides, mainly through gasoline combustion in automobiles, which contributes approximately half the nitrogen oxides released into the atmosphere. Nitrogen oxides contribute to acid deposition and, along with unburned gasoline vapors, the formation of photochemical smog.
The burning of natural gas, on the other hand, does not pollute the atmosphere as much as the burning of oil. Natural gas is a relatively clean, efficient source of energy that contains almost no sulfur, a contributor to acid deposition. In addition, natural gas produces far less CO2, fewer hydrocarbons, and almost no particulate matter, as compared to oil and coal.
One of the concerns in oil and natural gas production is the environmental damage that may occur during their transport, often over long distances by pipelines or ocean tankers
The Largest Oil Spills in the United States
In approximately the last two decades, two extremely damaging oil spills have taken place off the coast of the United States—in the Gulf of Mexico (Deepwater Horizon Oil Spill) and in Prince William Sound (Exxon Valdez oil spill). Deepwater's spill was larger.
Deepwater oil drilling
Deepwater oil drilling has a much greater potential for oil spills than does shallow-water drilling, because of both the difficulty in building and maintaining the connection to the well and, as was learned from the Deepwater Horizon event, the extreme challenge of plugging a spill so far below the ocean surface.
Deepwater Horizon Oil Spill
the Deepwater Horizon, a drilling platform in the Gulf of Mexico, exploded , around 5 million barrels (210 million gallons) of oil gushed from the well
Exxon Valdez oil spill
spilled 260,000 barrels (10.9 million gallons) of crude oil into Prince William Sound along the coast of Alaska, creating the largest oil spill from a tanker in U.S. One positive outcome of the disaster was passage of the Oil Pollution Act of 1990.
Oil Pollution Act of 1990
This legislation establishes liability for damages to natural resources resulting from a catastrophic oil spill, including a trust fund that pays to clean up spills when the responsible party cannot; a tax on oil provides money for the trust fund. The Oil Pollution Act requires double hulls on all oil tankers that enter U.S. waters by 2015. Had the Exxon Valdez possessed a double hull, the disaster might not have occurred because only the outer hull might have broken.history.
The Largest Global Oil Spill
The world's most massive oil spill occurred in 1991 during the Persian Gulf War, when about 6 million barrels (250 million gallons) of crude oil were deliberately dumped into the Persian Gulf
History of the Arctic National Wildlife Refuge
In 1960 Congress declared a section of northeastern Alaska protected because of its distinctive wildlife. The Department of the Interior was given permission to determine the potential for oil discoveries in the area, but exploration and development could proceed only with congressional approval.
Support for and Opposition to Arctic National Wildlife Refuge
Supporters cite economic considerations as the main reason for drilling for oil in the refuge. The United States spends a large proportion of its energy budget to purchase foreign oil. Development of domestic oil could, for a DECADE OR SO, improve the balance of trade and make us less dependent on foreign countries for our oil.The oil companies are eager to develop this particular site because it is near Prudhoe Bay (has large oil deposits).
Conservationists think oil exploration poses permanent threats to the delicate balance of nature in the Alaskan wilderness, in exchange for a temporary oil supply. Further, they point out that using domestic oil is a short-term fix and will in the long run lead to greater dependence on foreign oil. They prefer investing in renewable energy sources and energy conservation—permanent solutions to the energy problem.
synfuels (short for synthetic fuels)
materials similar in chemical composition to oil or natural gas, have long been considered possible future sources of fossil fuels. Synfuels include tar sands, oil shales, gas hydrates, liquefied coal, and coal gas. Although more expensive to produce than oil and natural gas, synfuels may become economically competitive as fuel prices rise. Although synfuels are promising energy sources, they have many of the same undesirable effects as fossil fuels (CO2 into atmosphere).
A synfuel. Tar sands, or oil sands, are underground sand deposits permeated with bitumen, a thick, asphalt-like oil. The bitumen in tar sands deep in the ground cannot be pumped out unless it is heated underground with steam to make it more fluid. Once bitumen is obtained from tar sands, it must be refined like crude oil.
A synfuel. Sedimentary "oily rocks" that contain a mixture of hydrocarbons known as kerogen; to yield oil, oil shales must be crushed, heated to high temperatures, and refined after they are mined. It is not yet cost-effective to process oil shales because the mining and refinement require a great deal of energy.
Reserves of ice-encrusted natural gas located in porous rock in the arctic tundra (under the permafrost) and in the deep-ocean sediments of the continental slope and ocean floor. Not cost-effective, but oil companies are becoming interested.
A synfuel. The process by which solid coal is used to produce a synthetic liquid fuel similar to oil.
A synfuel. The technique of producing a synthetic gaseous fuel (such as methane) from solid coal.
Fossil Fuels in China
China is the world's second-largest importer of oil, importing almost half its oil.
Attempting to limit its dependence on oil imports, the Chinese government wants to develop domestic oil sources and to substitute other fuels for oil. Thus far, China's oil supplies have proved less than promising, and coal and hydropower are the only major alternatives.
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