Scaling up production of biofuels from algae to meet at least 5% of US transportation fuel needs would place unsustainable demands on energy, water, and nutrients, a new National Research Council report said.
The concerns are not a definitive barrier to future production, however, and innovations requiring research and development could help realize algal biofuels' full potential, added the Oct. 24 report by the council, which is part of the National Academies of Science.
Biofuels from algae and cyanobacteria are possible petroleum fuel alternatives and could help the US meet its transportation fuel needs while reducing carbon dioxide and other greenhouse gas emissions, the report noted.
Algal biofuels offer potential advantages over biofuels made from land plants, including algae's ability to grow on noncropland in cultivation ponds of fresh, salt, or waste water, it said.
"The number of companies developing algal biofuels has been increasing, and several oil companies are investing in them," the report said. Consequently, the US Department of Energy's Office of Renewable Energy and Energy Efficiency asked the National Research Council to identify sustainability issues associated with algal biofuels' large-scale development, it said.
Concerns related to that development include the relatively large quantity of water required to cultivate algae; the magnitude of nitrogen, phosphorous, CO2, and other nutrients required for cultivation; the amount of land necessary to contain algae-growing ponds; and uncertainties about GHG emissions, according to the report.
Necessary returns
"Moreover, the algal biofuel energy return on investment would have to be high, meaning more energy would have to be produced from the biofuels than what is required to cultivate algae and convert them to fuels," it said.
It also would be necessary to research, develop, and demonstrate wastewater or recycled harvest water could be used to cultivate freshwater algae for biofuels, the report indicated.
To determine whether the potential amount of algal biofuels could be produced in the US, it said there also would need to be a national assessment of land requirements to cultivate algae that considers climatic conditions; freshwater, inland, and coastal saline water, and wastewater resources; sources of CO2; and land prices.
The committee preparing the report proposed steps to help DOE determine whether sustainable development of algal biofuels is a practical possibility.
"The environmental, economic, and social effects of algal biofuel production and use have to be compared with those of petroleum-based fuels to determine whether algal biofuels contribute to improving sustainability," it observed.
The report recommended that producers, consumers, environmental groups, residents near potential algae cultivation or biofuel refinery sites, and other stakeholders be involved from the outset to help assure that sustainability goal tradeoffs are acceptable.
