species for light in natural waters (Sayre, 2011). Moreover, removing bicarbonate pumps, which increases fitness in the cultivation environment with high CO2, could reduce the competitive ability to take up inorganic carbon in natural waters (Sayre, 2011). If algicides are used, they would be effective against non-target organisms. Terminator genes that cause released cells to die could be developed so that those genes would be suppressed in a photobioreactor but derepressed in natural environments (Sayre, 2011). If algal strains that cannot produce toxins are used, potential risk is minimized. If genetically engineered organisms are released, monitoring should be undertaken so that effects of particular organism-environment combinations can be better understood (Snow et al., 2005).

5.8.4 Sustainability Indicators

Sustainability indicators for genetically engineered algae generally would be the same as indicators for native algae. That is, if effects of concern include biodiversity or water quality, appropriate metrics are described in those chapters. However, the sustainability goals for genetically engineered algae likely would include two other issues:

•  Minimizing dissemination of genetically engineered algae.

•  Establishing methods to determine whether an observed effect was caused by a genetically engineered alga.

Abundance of genetically engineered algae released to water could be measured through species-specific tests if the species were not native. Moreover, some modified traits, such as altered antennae, might be detectable microscopically and thus quantifiable in water. Particular DNA sequences also might be detectable. Moreover, markers could be added to algae to allow easy measurement in specific media.

5.8.5 Information and Data Gaps

The ecological risks of a release of genetically engineered microorganisms have to be carefully assessed before they are used in commercial-scale algal biofuel production. Whether there are plausible scenarios under which genetically engineered algae, or organisms that acquire genes from the genetically engineered algae, could proliferate to levels that might harm humans or the environment in some way needs to be examined. More information is needed on potential relationships between traits that are targets for modification and behavior of cyanobacteria or microalgae that could alter rates of release, survival, growth, transport, genetic exchange, and ecological or human health effects. Little research to date has been conducted in the United States on behavior of genetically engineered algae in open ponds, in part because EPA notification guidelines can lead to delays for researchers. Information is needed on the social acceptability of the use of genetically engineered algae for biofuels, particularly in open systems.

5.9 WASTE PRODUCTS

5.9.1 Potential Environmental Effects

Sustainability of a production process is enhanced by recycling raw materials and minimizing of waste. If the oil-extracted biomass is recycled or made into coproducts, a



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