. "Appendix E: Assessing the Sustainability of Biofuels: Metrics, Models, and Tools for Evaluating the Impact of Biofuels." Expanding Biofuel Production: Sustainability and the Transition to Advanced Biofuels: Summary of a Workshop. Washington, DC: The National Academies Press, 2010.
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Expanding Biofuel Production and the Transition to Advanced Biofuels: Lessons for Sustainability from the Upper Midwest - Summary of a Workshop
ronment, equity, economy), holds that to be sustainable an organization must consider the environmental and social aspects of its actions as well as economic returns.
The Natural Step. The Natural Step defines a sustainable society as one in which “nature is not subject to systematically increasing (1) concentrations of substances extracted from the earth’s crust, (2) concentrations of substances produced by society, or (3) degradation by physical means; and, in that society, (4) human needs are met worldwide” (Nattrass and Altomare, 1999).
The Ecological Footprint. Here, sustainability, defined as “living within the regenerative capacity of the biosphere” (Rees and Wackernagel, 1994; Wackernagel et al., 2002), involves comparing the amount of land required to produce food and other goods for, and to absorb wastes from, society to the amount of land available. Wackernagel et al. (2002) calculated that human demand may have been in excess of the Earth’s regenerative capacity since the 1980s, and is currently 20 percent above capacity.
Graedel and Klee’s Sustainable Emissions and Resource Usage. Graedel and Klee (2002) quantify a sustainable activity in the following steps: (1) Establish the available supply or limit of the chosen resource or product. (2) Choose a time period over which the use of the resource or creation of the product cannot exceed the supply or limit (e.g., 50 years). (3) Account for recapture (e.g., recycling, sequestration). (4) Using this information, derive the maximum acceptable rate of use or production and compare it to the current rate. If the current rate is higher than the maximum rate, it is unsustainable.
Marshall-Toffel Sustainability Hierarchy. Marshall and Toffel (2005) review previous frameworks, and then prioritize sustainability goals into a four-level hierarchy, starting with the most important as follows: “(1) Actions that, if continued at the current forecasted rate, endanger the survival of humans. (2) Actions that significantly reduce life expectancy or other basic health indicators. (3) Actions that may cause species extinction or violate human rights. (4) Actions that reduce quality of life or are inconsistent with other values, beliefs, or aesthetic preferences.”
As Marshall and Toffel (2005) highlight, each of the frameworks listed above has strengths and weaknesses. For example, the Triple Bottom Line provides a method for corporations to increase their sustainability, but critics point out that it is arbitrary to stop at three constraints when other factors (e.g., ethics) are also important. The social and environmental performance of a company can also be difficult to quantify.
A strength of the Natural Step is that it presents quantifiable indicators for sustainability. However, it does not address the relative importance of specific criteria. Also, it is difficult to relate the Natural Step criteria to physical effects