Life Cycle Assessment has become a popular approach for evaluating the broader environmental impacts of technological alternatives. The benefits of LCA are likely to be most significant for emerging technologies and at early stages of decision making. This realization is driving the promotion of LCA for evaluating new technologies such as nanotechnology, green chemistry, and new fuels. Unfortunately, traditional LCA is best suited for evaluating more mature technologies due to its reliance on detailed data about emissions throughout the life cycle and their impact. Such data are often not available for emerging technologies due to a sheer lack of information or the slow pace of toxicological studies. In contrast, data about material and energy inputs to even emerging technologies is much more readily available.

This talk will explore whether LCA based only on input data can provide a proxy for life cycle impact. Techniques for input-side LCA that will be considered include those based on mass, energy, industrial cumulative exergy (ICEC) and ecological CEC (Hau and Bakshi, 2004). Thermodynamics is expected to play a unique role in connecting life cycle inputs with LCA impacts, because all ecological and industrial processes are networks of energy flows. Exergy is the measure of the available energy. If more exergy is consumed in a process, it results in a larger increase in entropy of the surroundings which may translate into a bigger environmental impact. Therefore, life cycle cumulative exergy consumption may be a proxy for life cycle impact.

The relationship between input-side LCA metrics and output-side LCA metrics will be explored with the help of a thermodynamic input-output model of the US economy (Ukidwe and Bakshi, 2004). Statistical regression and hypothesis testing will be used to determine whether a statistically valid correlation exists between input- and output-side LCA metrics. If validated, such a correlation is expected to be very useful for preliminary screening and evaluation of emerging technologies and at early stages of decision making. As more information about emissions and impact become available, they may be incorporated in the thermodynamic LCA approach.

Reference: Ukidwe, Nandan U., Bakshi, Bhavik R., Thermodynamic Accounting of Ecosystem Contribution to Economic Sectors with Application to 1992 U.S. Economy, Environmental Science and Technology, 2004, 38(18), 4810-4827 Hau, Jorge L., Bakshi, Bhavik R.，Expanding Exergy Analysis to Account for Ecosystem Products and Services, Environmental Science and Technology, 2004, 38(13) 3768-3777