18.1 million Btu per ton of product, which is 22 percent more than the practical minimum energy consumption of about 14 million Btu per ton (AISI, 2003). These energy losses are a result of the production energy embedded in yield losses and process inefficiencies.

Energy consumption per ton of steel has decreased 27 percent since 1990, while CO2 emissions fell by 16 percent. For 2002–2005, energy intensity per ton of steel decreased by 12 percent. Energy-use improvements from avoiding yield losses would contribute another 20 percent in savings.

In 2005, the American Iron and Steel Institute announced a goal of using 40 percent less energy per ton of steel in 2025 than what steelmakers were using in 2003 (AISI, 2005); this goal will require the development and implementation of “transformational technologies.” The most promising opportunities include EAF melting advances, BOF slag-heat recovery, integration of refining functions, heat capture from EAF waste gas, and increased direct carbon injection. The majority of these technologies may be available before 2020, assuming continued R&D. Several revolutionary new steelmaking technologies and concepts—the use of hydrogen as an iron-ore reductant or furnace fuel, for example, or electrolytic or biometallurgy-based iron and steel production—could be ready in the 2020–2035 timeframe.

Cement

The cement industry accounts for 5 percent of the energy used in the U.S. manufacturing sector, or 1.3 quads (DOE, 2002), and about 9 percent of global industrial energy use (IEA, 2007). The industry is also responsible for about 5 percent of worldwide anthropogenic CO2 emissions and for 2 percent in the United States (Worrell et al., 2001; Worrell and Galitsky, 2004).

Cement plants increase in efficiency with size, and advanced dry-kiln processes are substantially more efficient than older wet-kiln processes. In the United States, energy consumption varies from 6.2 million Btu per ton of clinker (the cement precursor produced from limestone and other chemicals in cement kilns) for smaller wet plants to 3.8 million Btu per ton of clinker for dry preheater-precalciner kilns (van Oss, 2005). Coal is the chief fuel consumed in U.S. plants, although they utilize an increasing proportion of waste materials, used tires, and petroleum coke.

Energy use also varies with the process and characteristics of a plant, but in general, about 90 percent of the energy use, and all of the fuel use, occurs in the



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