Will the Laws of Physics Prevent Manufacturers from Improving Energy Efficiency?

April 8, 2013

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Cement plant, California. Credit: Rick Hall, CC BY 2.0.

Cement plant, California. Credit: Rick Hall, CC BY 2.0.

The manufacturing sector is doing a great job improving energy efficiency, said a group of researchers from MIT and other institutions in a recent study. There's just one problem, the authors cautioned: The laws of thermodynamics are going to make progress on individual materials increasingly difficult and eventually impossible.

MIT mechanical engineering professor Timothy G. Gutowski and colleagues analyzed the energy requirements of making steel, cement, paper, plastics, and aluminum, the five materials “that dominate energy used in material production.” What would it take, they asked, to double production of these materials between now and 2050, while cutting in half the energy required to make them -- in other words, a 75-percent reduction in energy intensity? This goal would be in line with economists' projections that global demand for materials will double by 2050, as well as the Intergovernmental Panel on Climate Change's (IPCC) recommendation of a 50 percent reduction in greenhouse gas (GHG) emissions by that time.

The investigators found that through strategies such as application of technologies and recycling it should be possible to achieve a 50- to 56-percent reduction in energy intensity for these key materials -- impressive, but significantly short of the 75-percent goal. “Ultimately,” they wrote, “we face fundamental thermodynamic as well as practical constraints on our ability to improve the energy intensity of material production.”

Gutowski's prediction of growing efficiencies in material production fits generally with the historical trend revealed in the Energy Information Agency's (EIA) Manufacturing Energy Consumption Survey (MECS). The survey finds that from 2002 to 2010, energy consumption in the U.S. manufacturing sector decreased by 17 percent, whereas gross output decreased by only 3 percent, pointing to a reduction in energy intensity. EIA says the decline “reflects both improvements in energy efficiency and changes in the manufacturing output mix.”


Historical improvement in energy efficiency for aluminum production. Credit: International Energy Agency.

Historical improvement in energy efficiency for aluminum production. Credit: International Energy Agency.

But Is Material Production the Only Place to Look for Savings?

Other researchers point to the importance of manufacturing energy efficiency as a way to optimize growth while holding down industrial climate impacts and resource depletion. However, energy efficiency in production of materials is not the only path to reducing those impacts. Manufacturing might be able to find ways to improve energy productivity in the larger picture through measures not directly related to the production of materials.

Will O'Brien, a sustainability expert and executive-in-residence at Clark University in Worcester, Mass., encouraged me to think about the possible role of standards such as LEED and Energy Star that can “reduce energy consumption in manufacturing facilities for existing buildings or new constructions.” He particularly points to the potential of Integrative Design as envisioned by Amory B. Lovins's Rocky Mountain Institute (RMI), a non-profit research organization focused on resource efficiency. Integrative Design, O'Brien said, “rigorously applies orthodox engineering principles, but achieves radically more energy- and resource-efficient results by asking different questions that change the design logic.” RMI “has demonstrated remarkable reductions in energy consumption,” he told me.

In his 2011 book, Lovins estimates that “compared to theoretically perfect processes, the U.S. economy is only about 13 percent efficient, the global economy, around 10 percent. Even the most efficient industrial processes today use two or three times the energy that's theoretically necessary.”

Lovins says cement production could theoretically reduce its energy intensity by 63 percent, aluminum by 81 percent, bulk chemicals by 88 percent, and pulp and paper by 44 percent. Industry uses so much more energy than required because of such practices as “operating at temperatures or pressures higher than required” or by employing “high-quality energy when low quality energy would serve.” One example could be “heating a room with electric resistance heating,” which “uses 100 percent of its quantity but only 6 percent of its quality.”

The Alliance to Save Energy (ASE) earlier this year produced a paper that lays out scenarios that could achieve as much as 2.75 percent improvement per year in energy productivity, depending on the extent to which public policy, R&D, technology commercialization, capital investment, and other influences might be brought to bear.

Scenarios for improvement in industrial energy intensity. Courtesy of Alliance to Save Energy.

Scenarios for improvement in industrial energy intensity. Courtesy of Alliance to Save Energy.

Rodney Sobin, senior policy manager at ASE, who worked on the report, tells me that the conclusion in the MIT report “that a 50 percent improvement in energy intensity -- or roughly doubling energy productivity -- for iron and steel and for pulp and paper as a theoretical limit broadly agrees with” the table used in his report. However, he cautions, “in projecting potential manufacturing energy consumption and intensity broadly one should consider what the future composition and structure of production may look like.” Industry might continue to approach thermodynamic limits to energy efficiency -- which, in fact, would be a very good thing, Sobin stresses. But beyond that, he told me, it is hard to say right now that energy productivity on a broad scale can't be improved in unanticipated ways:

There is still scope for reduced scrap, more efficient end-use, improved reuse and recycling, and for substitute materials. In the meanwhile, other materials and processes may arise or take on new uses. For example, if we did a study on theoretical energy intensity or productivity of broad manufacturing -- versus individual processes -- 60 years ago, we might try to calculate theoretical potential energy intensity for making vacuum tubes, picture tubes, electromechanical phone switches, typewriters and so on, and scarcely consider semiconductor processing or monoclonal antibody-based pharmaceuticals ... underestimate the proportion of production requiring rare earths, and not have seen the rise of aluminum and plastic for food and beverage packaging at the expense of steel and glass.
In other words, it's hard to predict the kinds of qualitative changes in manufacturing that might radically affect energy productivity in the future.

Material Efficiency

In the MIT study, Gutowski insists that the “fundamental barriers” of the laws of physics will prevent industry from cutting in half the world's energy consumption while doubling demand, even with “very aggressive improvement scenarios.” However, in harmony with some of the other researchers I consulted, Gutowski thinks alternative strategies could prove fruitful. He suggested that “we could greatly reduce material energy requirements if we could reduce demand” through a program of what he calls “material efficiency”:

The essence of material efficiency is to be more efficient in how materials are used in the design of new products, to make products last longer, and to optimize the operational intensity of the material goods (e.g., serve more people with a given product -- to share). By themselves, these ideas are not new ideas. But they have not yet been explored in any depth as a means to reduce our global energy use and carbon emissions.
Such a strategy, Gutowski believes, “would require new thinking about how we use materials” and “is decidedly not a business-as-usual scenario, but is worth looking into in more detail.”


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