n impact assessments "“ Air emission impacts from tailpipes and production facilities accrue within years and can be allocated to the year of emissions without discounting. GHG emission impacts are distributed over decades and even centuries using integrated assessment models, and are often discounted. Decisions about discounting can strongly influence the outcome of impact assessments, yet there is not a clear rational basis for making these decisions.
* Assessing transitions as well as end states - In addressing transitions, emerging technologies could profoundly change the assumptions that underlie biofuel LCAs. For example, changes in protein production and consumption patterns or in urban land-use policies could open up substantial agricultural land for biofuel production, an action that would fundamentally change a biofuel LCA.
* Confronting uncertainty and variability - Addressing uncertainty is among the greatest of LCA challenges, not only for biofuels, but for other LCA efforts as well. To confront uncertainty and variability, the "doable" and "knowable" must be separated from assumptions that are conditional components of the LCA.
In their report, the authors of the EBI study say that confronting these seven grand challenges for a biofuels LCA requires a good balance between the needs of technology momentum and adaptive decision making, something, they say, that has not always been well-articulated among practitioners of LCA.
"We must recognize that LCA is not a product but an ongoing process for organizing information and prioritizing information needs," McKone says. "LCAs should be viewed as tools for building scenarios from which one can learn, rather than truth-generating-machines. We do not see the grand challenges outlined in this report as hurdles to be cleared, but rather as opportunities for the practitioner to focus attention on making LCA more useful to decision makers."
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