Over one-third of today’s global GHG emissions come from transportation and manufacturing, and reducing their GHG significantly will likely require abundant, inexpensive low-carbon liquid fuels. With promising technologies, including artificial photosynthesis, algae-based fuels, and conversion of CO2 to fuel, still in R&D, how does their performance and economics compare? What production scale is needed for them to reach that potential? What changes would be needed to existing fuel transport and delivery infrastructures? What are their obstacles to move toward commercialization, and how can they surmount them?