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Unformatted text preview: The leading sources of CO 2 emissions in the U.S. are coal-fired power plants like this one.There are increased efforts to regulate major greenhouse gas polluters, and new emphases on developing so-called “clean coal” technologies of carbon capture and “sequestration” (burial). But the benefits of these measures are uncertain, and sequestration is in its infancy.As with nuclear waste, the question becomes: how long can buried coal gases stay buried? That aside, most U.S. coal now comes from mountain-top removal mining (see back cover and chapter four) which is transforming the glorious mountains of several states into waste- lands, and will never qualify as “clean.” In any case, coal reserves are far lower than have been reputed, making long term viability doubtful. ISTOCK Two NINE KEY CRITERIA: COMPARING ENERGY SYSTEMS AND THEIR LIMITS w I N EVALUATING ENERGY SOURCES , it is essential first to give attention to the criteria being used. Some criteria give us good information about an energy source’s usefulness for specific applications. For example, an energy source like oil shale that is a solid material at room temperature and has low energy density per unit of weight and volume is highly unlikely to be good as a transport fuel unless it can first somehow profitably be turned into a liq- uid fuel with higher energy density (i.e., one that contains more energy per unit of weight or vol- ume). Other criteria gauge the potential for a specific energy source to power large segments of an entire society. Micro-hydro power, for example, can be environmentally benign, but its yield cannot be sufficiently increased in scale to provide a significant portion of the national energy budget of the U.S. or other industrial countries. In general, it is important to identify energy sources that are capable of being scaled up to pro- duce large quantities of energy, that have high economic utility, and that have minimal environ- mental impacts,particularly those impacts having to do with land use and water requirements, as well as with greenhouse gas emissions. Only sources that pass these tests are capable of becoming our future primary energy sources—that is, ones capably of supplying energy on the scale that fossil fuels currently do. The economic utility and scalability of any energy source are determined by three main factors: the size of the resource base, the energy density of the resource itself, and the quantity and nature of other resources and infrastructures needed to process and employ the energy source in question. Economist Douglas Reynolds, in a paper dis- cussing the energy density of energy sources (which he terms “energy grade”), writes: Energy is the driving force behind indus- trial production and is indeed the driving force behind any economic activity....
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This note was uploaded on 09/04/2011 for the course CHEM 1B taught by Professor Fossum during the Spring '10 term at Laney College.
- Spring '10