5.3.3. Data and Method Gaps
The data gaps for estimating energy use and the method gaps in reducing energy use discussed in the section Energy (Chapter 4) apply to reduction of GHG emissions.
5.3.4 Sustainability Indicators
An appropriate sustainability indicator for GHG emissions is the amount of CO2 equivalent emitted per unit energy produced, which has been selected as an indicator for GHG emissions of biodiesel and commonly has been used in discussing energy-related GHG emissions (GBEP, 2011; Mata et al., 2010).
5.4.1. Potential Environmental Effects
The introduction of large bodies of water in arid or semi-arid environments could alter the local climate of the area by increasing humidity and reducing temperature extremes. Similarly, the introduction of large-scale, open-pond algal cultivation systems in arid or semi-arid environments, where much of algae production in the United States is projected to take place (see Chapter 4), could affect local climate and ecosystems. The use of photobioreactors would not likely alter local climate.
Studies of reservoirs provide some useful ecological information. Reservoirs created by the damming of rivers could affect evaporation rates of the surrounding landscape, leading to changes in vegetation cover and terrestrial species diversity (Huntley et al., 1998). Large dams can affect surrounding climate and precipitation, particularly in Mediterranean and semi-arid climates (Degu et al., 2011).
5.4.2 Sustainability Indicators
The sustainability indicators for potential changes in local climate are trends in relative humidity and trends in temperature distribution statistics.
5.4.3 Information and Data Gaps
While parallels can be drawn from the introduction of large reservoirs in arid regions, the variability in size, geography, and production methods that will emerge as the algae industry grows will necessitate additional research to fully understand and address the impacts associated with local climate alteration.
5.5.1 Potential Environmental Effects
The air quality impacts of algal biofuel production will depend on system design. Different air quality issues arise in conjunction with the different steps of the algal biofuel supply chain. Thus, this section is organized by the steps along the production pathways. The wide range of potential organisms for producing algal biofuels and the wide range of final fuel products result in a broad range of possible air emissions.