Given the multiple resource requirements and potential environmental effects, specific sustainability concerns cannot be viewed in isolation from others. Any one life-cycle assessment (LCA) for a single resource use or environmental effect is insufficient to determine the overall sustainability of an algal biofuel production system. Challenges arise regarding how to assess the overall environmental sustainability of algal biofuels holistically and how to balance the environmental objectives against the economic and social objectives of sustainable development. An overall and comparative assessment of sustainability is complicated by the fact that some sustainability objectives can be estimated on the basis of mass balance or engineering principles and compared across systems—for example, nutrient budgets, energy balances, and GHG emissions—while others are region specific. Other sustainability objectives are specific to region and maybe species, and the environmental effects in one region might not be directly comparable to another—for example, land-use change (LUC) and biodiversity.

The committee proposes a stepwise framework (Figure S-2) to aid DOE in its decisionmaking process that would help ensure sustainable development of algal biofuels. The framework uses a variety of tools for assessing overall sustainability including LCAs that integrate a particular aspect of sustainability through the supply chain, cumulative impact


FIGURE S-2 A potential framework for assessing sustainability of algal biofuels during different stages of development.

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