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Sustainability and the U.S. Energy System

March 27, 2009

Contact: Allan Chen,

The United States has made progress toward a more sustainable energy system since 2000 in some areas, and has moved away from sustainability in others, according to an analysis by Berkeley Lab scientists Mark Levine and Nathaniel Aden. Their analysis is published in a chapter of a new book, Agenda for a Sustainable America. The volume was published by the Environmental Law Institute and contains contributions from 41 experts on various aspects of sustainability.

On the positive side, from 2000 to 2006, the energy and carbon intensity of gross domestic product (GDP) continued its long-term decline even as GDP increased. Energy intensity is the amount of energy consumed in the U.S. divided by the GDP; carbon intensity is the amount of greenhouse gas emissions divided by GDP. Declining intensity values show that the U .S. has increased its economic output without increasing energy use and greenhouse gas emissions commensurately.

Per capita energy use remained constant. In 2000, per capita electricity use was 12.76 megawatt-hours (MWh) per person per year. It was slightly lower in 2006 despite a 16 percent increase in GDP over the same period.

However, “increased fossil fuel consumption, stagnant energy efficiency standards and expanding corn-based ethanol production have moved the energy system in the opposite direction, toward a less sustainable energy system,” say Levine and Aden in the new report.

Levine and Aden used the definition of sustainability articulated in the 1987 Brundtland Commission report: “meeting the needs of the present without compromising the ability of the ability of future generations to meet their needs.”

A comprehensive analysis of sustainability in America

Edited by Widener University professor of law John Dernbach, and published by the Environmental Law Institute, the book’s 31 chapters authored by 41 writers assesses trends in 28 separate areas of American life—including forestry; transportation; oceans and estuaries; religion; and state, local, and national governance.

The chapter by Levine and Aden, scientists in Berkeley Lab’s Environmental Energy Technologies Division examines and assesses trends in the U.S. energy economy. “From 2000 to 2006,” the authors say, “the U.S. energy system moved both toward and away from sustainability.” The aforementioned decreasing trends in energy and carbon intensity, increased energy efficiency and improved air quality all indicate improvement.

At the same time the U.S. also increased fossil fuel combustion, especially of coal (which increases greenhouse gas emissions). The nation has also seen increases in the use of corn ethanol, which is not an efficient source of fuel, and slowness in implementing stricter energy efficiency standards as mandated by acts of Congress.

Lower carbon intensity, higher efficiency

Carbon intensity has declined two percent per year from 2000 to 2006, comparable to a long trend that has been taking place in the U.S. since 1970. The authors suggest that if this decline were about twice as high—three to four percent per year—through increased energy efficiency, the U.S. would be well on course to achieve carbon goals that are sought by many.

The U.S. annual energy consumption per capita declined even as the per capita GDP grew from $34,883 in 2000 to $36,122 in 2006 (in year 2000 dollars). Per capita electricity consumption remained constant during these years, another positive sign. Without energy efficiency, electricity use tends to increase in industrialized nations, where it is the preferred form of energy use. These indicators suggest to the authors that the economy has become more energy-efficient as its output increased.

Air quality in the U.S. has improved between 2000 and 2005. For example, air quality monitoring stations throughout the U.S. showed that 4.5 percent of air quality readings were above ozone standards between 1999 and 2001. However, between 2003 and 2005, this percentage dropped to 2.1 percent. Other indicators of air quality also showed improvement during these years.

Increased use of coal noted

Levine and Aden note that from 1970 to 2000, the U.S. economy saw a reduction in the carbon intensity of energy use, but from 2000 to 2006, this trend reversed itself. The increased use of coal is one reason for this change.

“It is important to recognize how far outside the norm of energy use and carbon emissions per capita the United States is in comparison with other industrialized countries,” they write. The U.S. emits 2.5 times the per capita carbon dioxide emissions of the major European Union nations. This number has changed very little over 35 years.

Ethanol analysis indicates new approaches needed

From 2000 to 2006, the consumption of biomass in the U.S. grew at an average rate of one percent annually. The use of wood declined seven percent while biofuel consumption tripled. “However, the current American production of biofuels through corn-based ethanol is unsustainable,” write the authors, citing three reasons.

The energy return from ethanol is low: between 1.2 and 1.6 units of energy are returned for each one unit used to manufacture ethanol, while the same ratio is 15:1 for petroleum. This means that much more energy is required to produce the same amount of energy in liquid fuels.

Second, the increase in biofuel demand has led to a problematic rise in food prices. Maize production has risen to historic levels, but its cost increased from $78/ton in December 2000 to $142/ton in December 2006.

Finally, various studies have suggested that there is insufficient production capacity in the U.S. for ethanol to replace petroleum as a fuel that could meet U.S. demand. Dedicating all current U.S. corn and soybean production would meet only 12 percent of gasoline, and six percent of diesel demand.

Recommendations for moving forward

Levine and Aden suggest the U.S. can develop a more sustainable energy system if it increases its energy efficiency through standards and better technology. There is considerable technical and economic opportunity to increase appliance efficiency standards, and to improve the energy efficiency of cars, light- and heavy-duty vehicles. They also urge support of R&D for energy-efficient commercial buildings, for technologies that can move these buildings toward zero net-energy use.

Another priority should be on research leading to higher-efficiency biofuels that that would supplant the use of ethanol, and to technologies that would lead to the economy’s transition to a modern solar energy-based energy system. They argue that the use of either taxation on energy production and consumption of carbon, or a cap-and-trade system of carbon emissions can help reduce these emissions by aligning private-sector incentives with the societal costs of energy production.

Finally, they argue that the U.S. should set targets for industrial sector carbon emissions, because U.S. industry is less energy-efficient, “in many cases by a substantial margin” than industry in other developed countries.

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