Environmental Problems, Their Causes, and Sustainability 1

Currently, oil has a high net energy ratio becausemuch of it comes from large, accessible, and cheap-toextractdeposits such as those in the Middle East. Whenthose are depleted, the net energy ratio of oil will declineand prices will rise.Conventional nuclear energy has a low net energyratio because of the large amounts of energy needed tomake it available. We have to extract and processuranium ore, convert it into nuclear fuel, build and operatenuclear power plants, dismantle the highly radioactiveplants after their 15–60 years of useful life,and store the resulting highly radioactive wastessafely for 10,000–240,000 years depending on the typesof radioisotopes they contain. Each of these steps inwhat is called the nuclear fuel cycle uses energy andcosts money. Some analysts estimate that ultimatelythe conventional nuclear fuel cycle will lead to a netenergy loss; we will have to put more energy into itthan we will ever get out of it.17-2 OILWhat Is Crude Oil, and How Is It Extractedand Processed? Gooey Stuff to Which We AreAddictedCrude oil is a thick liquid containing hydrocarbonsthat we extract from underground deposits andseparate into products such as gasoline, heating oil,and asphalt.Petroleum, or crude oil (oil as it comes out of theground), is a thick and gooey liquid consisting of hundredsof combustible hydrocarbons along with smallamounts of sulfur, oxygen, and nitrogen impurities.We have oil today because of a series of three lucky geologicalevents taking place over millions of years. Thefirst event occurred when sediments buried dead organicmaterial raining down onto seafloors faster thanit could decay. The next event took place eons laterwhen the seafloor sediments ended up with the rightdepth for pressure and heat to slowly “cook” or convertthe buried organic material into oil. The third geologicalbreak came about because the oil was able tocollect in porous limestone or sandstone rock coveredby an impermeable cap of shale or silt to keep it fromescaping (Figure 17-2) and thus making it and otherfossil fuels part of the carbon cycle (Figure 4-29, p. 78).Any change in this fortunate chain of eventswould have meant no oil, which provides about athird of the energy we use today to heat our homesand other buildings and to run our motor vehicles. Oiland its chemical cousin natural gas also provide uswith food grown with the help of hydrocarbon-basedfertilizers and pesticides. This type of oil is also knownas conventional oil or light oil.Today’s global oil industry is a marvel of technologyand management skills. Satellites help findpromising oil deposits. Sophisticated computers andsoftware programs analyze seismic data to create 3-Dimages of the earth’s interior. High-tech equipmentcan drill oil and natural gas wells to a depth of almost6 kilometers (4 miles). Drilling platforms on the highseas are engineering marvels that can withstand majorhurricanes. The incredibly complex process of managingand coordinating the discovery, production,marketing, and distribution of oil throughout theworld to billions of users is an amazing process.Deposits of crude oil and natural gas often aretrapped together under a dome deep within the earth’scrust on land or under the seafloor (Figure 17-2). Thecrude oil is dispersed in pores and cracks in undergroundrock formations, somewhat like water saturatinga sponge. To extract the oil, a well is drilled into thedeposit. Then oil drawn by gravity out of the rock poresand into the bottom of the well is pumped to the surface.On average, producers get only about 35–50% ofthe oil out of an oil deposit—although some believethat improved drilling technology may increase the recoveryrate to 75%. The remaining heavy crude oil is toodifficult or expensive to recover. As oil prices rise, it canbecome economical to remove about 10–25% of this remainingheavy oil by flushing the well with steam andwater. But this lowers the net energy yield for the recoveredoil.Drilling for oil causes only moderate damage tothe earth’s land because the wells occupy fairly littleland area. But drilling for oil and transporting itaround the world results in oil spills on land and inaquatic systems. In addition, harmful environmentaleffects are associated with the extraction, processing,and use of any nonrenewable resource from the earth’scrust (Figure 16-13, p. 343).According to oil producers, improved extractiontechnologies can increase oil production without seriousdamage to environmentally sensitive areas. Onemethod allows oil and natural gas producers to drilldeeper in most locations. In addition, oil producerscan now use one drilling rig (derrick) on a pad to drillseveral gas or oil pockets at the same time. Anothernew technology allows oil or gas extraction from distancesas far away as 8 kilometers (5 miles) by drillingat angles (slant drilling).After it is extracted, crude oil is transported to a refineryby pipeline, truck, or ship (oil tanker). There it isheated and distilled in gigantic columns to separate itinto components with different boiling points (Figure17-8, p. 356)—another technological marvel basedon complex chemistry and chemical engineering.However, refining oil decreases its net energy yield. Inthe United States, for example, petroleum refining accountsfor about 8% of all U.S. energy consumption.http://biology.brookscole.com/miller14355