Based on this discussion, there are at least four metrics that should be included in life cycle studies of algae-to-energy technologies:

• Net energy

• GWP

• Land use

• Water use

Net energy is important because efforts to use algae for fuel production are predi­cated on the assumption of a positive net energy balance. Similarly, GWP is impor­tant because of the expectation that algae-to-energy systems will be no more carbon intensive than conventional fossil fuels. In addition, land use and water use should be considered because of algae’s high productivity relative to terrestrial crops and its unique requirements for water that set it apart from other sources of bioenergy.