Page 543 - Environment: The Science Behind the Stories

70 and exploring the seabed of the Arctic. We are also using
more potent extraction methods, such as hydraulic fracturing
60
(pp. 180–181), to free gas from rock layers. And we are pursu-
50 ing new types of fossil fuels, including oil sands, shale oil, and
methane hydrates. These fuels are more expensive and lower
40
EROI 30 in quality, but they are increasingly being extracted as market
prices of fossil fuels rise and make their extraction profitable.
There is, however, another way we can respond to the
20
1400 depletion of conventional fossil fuel resources. This is to has-
10 ten the development of clean and renewable energy sources
1200
0 to replace them. By transitioning away from fossil fuels and
1000 toward renewable sources, we can gain energy that is sustain-
1950 1960 1970 1980 1990 2000 2010 able in the long term while greatly reducing pollution, health
800
EROI 600 Year impacts, and the emission of greenhouse gases that drive cli-
mate change (Chapters 18, 20, and 21).
This transition has begun to occur, but it is apparent that
400
we will continue to gain much of our future energy from fossil
200 fuels. Alas, so far our ability to control pollution has lagged
0 behind our capacity to consume energy. Many scientists now
1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 warn that if we do not immediately step up energy conservation
and accelerate our shift to renewables, we will drive our plan-
Year et’s climate into unprecedented territory, threatening impacts
on our economy, our quality of life, and our society’s future.
FIGURE 19.5 EROI values for discovering oil and gas in the
United States have declined over the past century. Data from
Guilford, M., et al., 2011. A new long term assessment of energy return on
investment (EROI) for U.S. oil and gas discovery and production. Pp. 133–154 in Fossil Fuels and Their Extraction
Sustainability, Special Issue, 2011, eds. C. Hall and D. Hansen, New studies in
EROI (Energy return on investment).
The three conventional fossil fuels on which our modern indus-
trial society was built, and on which we rely today, are coal,
(FIGURE 19.5). This means that we used to be able to gain 30 units natural gas, and oil. Additional fossil fuels we are beginning to
of energy for every unit of energy expended, but now we can extract or considering for the future include oil sands, shale oil,
gain only 11. EROI ratios for oil and gas declined because we and methane hydrates. We will first consider how each of these
extracted the easiest deposits first and now must work harder fossil fuels is formed, how we locate deposits, how we extract
and harder to extract the remaining amounts. For the Alberta oil these resources, and how our society puts them to use. We will
sands, EROI ratios are still lower, because oil sands are a low- then examine some of their environmental and social impacts.
quality fuel that requires a great deal of energy to extract and
process. EROI estimates for oil sands from studies so far range Fossil fuels are formed from ancient
from 1.5:1 to 9:1, with most estimates around 3:1 to 5:1.
organic matter

Where will we turn in the future for energy? The fossil fuels we burn today in our vehicles, homes, indus-
tries, and power plants were formed from the tissues of organ-
Throughout the 20th century, abundant and inexpensive coal, isms that lived 100–500 million years ago. The energy these
oil, and natural gas powered the astonishing advances of our fuels contain came originally from the sun and was converted
civilization. These extraordinarily rich sources of energy to chemical-bond energy by photosynthesis. The chemical
helped to bring us a standard of living our ancestors could energy in these organisms’ tissues then became concentrated
scarcely have imagined. as these tissues decomposed and their hydrocarbon com-
We began by extracting the fossil fuel deposits that were pounds were altered and compressed (FIGURE 19.6).
readily located and accessed, and we took advantage of bound- Most organisms, after death, do not end up as part of a
less energy at cheap prices. Yet because fossil fuel deposits are coal, gas, or oil deposit. A tree that falls and decays as a rotting
finite and nonrenewable, we gradually began depleting them. As log on the forest floor undergoes mostly aerobic decomposi-
easily accessible supplies of the three main fossil fuels became tion; in the presence of air, bacteria and other organisms that
depleted, EROI ratios rose, and fuels became more expensive. use oxygen break down plant and animal remains into simpler
In response, we have developed technology to reach carbon molecules that are recycled through the ecosystem.
deeper and farther, expending more money and energy in Fossil fuels are produced only when organic material is broken
order to continue obtaining fossil fuel energy. We have down in an anaerobic environment, one that has little or no oxy-
returned to sites that were already extracted, bringing power- gen. Such environments include the bottoms of lakes, swamps,
ful new machinery and approaches to squeeze more fuels from and shallow seas. Over millions of years, organic matter that
known locations. We are now reaching into formerly inac- accumulates at the bottoms of such water bodies may be con-
542 cessible places by drilling deeper, moving further offshore, verted into crude oil, natural gas, or coal, depending on (1) the

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