FIGURE 4-7 Estimated mean annual algal oil production (L/ha per year) under current technology in the continental United States, predicted by a GIS-based analysis. The insets illustrate finer-level detail at two northern and two southern locations.

SOURCE: Wigmosta et al. (2011). Reprinted with permission from the American Geophysical Union.

4.3.3 Opportunities for Mitigation

Opportunities for mitigating land requirements for algal biofuel systems lie in productivity— the only way to reduce the area required is to increase the productivity per unit area. Thus, developing more highly productive algal strains, engineering different pond designs, or using photobioreactors rather than ponds all would reduce land requirements. The related topics of impacts of land use and how to mitigate those effects are discussed in Chapter 5.

4.3.4 Sustainability Indicators

Indicators of sustainability of land requirements for algal biofuel production include the following:

•  Liters of fuel produced per hectare.

•  Kilograms of fuel produced per hectare.

•  Energy return on land invested (MJ/ha), analogous to EROWI.

•  Land required to meet various production targets relative to existing national usage or supply.

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