ences, 1989). At over 50 kg per day per American, even the rough profile developed here demonstrates the need for meshing environmental and materials research. Metrics highlight the locations and relative urgency of incorporating environmental goals into materials research programs. Significantly, these goals often overlap with factors affecting the bottom line such as reducing inputs, improving efficiency, recycling, and complying with environmental regulations.

Future materials fluxes, including both products and by-products, may even exceed contemporary ones in size. To make them environmentally compatible, we need better methods for analyzing their current condition and anticipating future changes. To achieve the goal of a more circular economy, society needs to consider its materials legacy as a dowry to future generations, rich in valuable ore. By capitalizing on the "mines above ground" or scrap piles for materials, wastes from extraction and disposal grow dispensable. We can imagine an industrial ecosystem in which emissions, including carbon and water vapor, are captured and complex waste streams are separated to recover the value and utility of their components. The discipline of creating national materials metrics is a useful start to creating a consistent, realistic long-range technical vision.

Acknowledgments

We are indebted to Donald Rogich, Jim Lemons, and Grecia Matos at the Bureau of Mines for data and ideas on materials taxonomy.

Notes

  • 1.

    In this paper we draw on other work by the authors (Wernick and Ausubel, 1995) that contains detailed data supporting the metrics presented here.

  • 2.

    Domestic stock refers to materials embedded in structures and products not discarded for a period longer than 1 year.

  • 3.

    We include atmospheric nitrogen fixed into NOx emissions as well as for ammonia production. We omit estimates of the mass of soil eroded during agricultural operations.

  • 4.

    A clear example of this is annual total U.S. dioxin and furan emissions, which are counted in kilograms rather than tons, yet have considerable environmental impact (Thomas and Spiro, 1995).

  • 5.

    A complete net carbon balance for forests includes annual carbon flows in trees, soil, forest floor, and understory vegetation. Since 1952, the amount of carbon stored in U.S. forests has grown 38 percent, adding about 9 billion metric tons of carbon (Birdsey et al., 1993).

References

Agarwal, J. C. 1990. Minerals, energy, and the environment. Pp. 389-395 in Energy and the Environment in the 21st Century, J. W. Tester, D. O. Wood, and N. A. Ferrari, eds. Proceedings of a conference held at Massachusetts Institute of Technology, Cambridge, Mass., March 26-28, 1990.



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