One of the biggest hurdles biofuels need to overcome is replicating the energy density of liquid transport fuels at lower cost. It’s been said that a scientist will never say something is impossible given unlimited funding. Unfortunately, the most brilliant theoretical energy innovations remain confined by economic realities.

Breaking Energy recently covered the potential for making value-added products from waste carbon dioxide, as opposed to treating it as a costly hazardous waste to be sequestered underground. Our colleagues at Scientific American shared an earlier piece that considered similar solutions for turning waste CO2 into fuel.

The article features several promising technologies, but also recognizes that gasoline’s energy density makes the fuel extremely efficient:

“The utility of liquid fuels is clear: one gallon of gasoline contains as much energy as 55,000 gallons of water pumped uphill to the height of Hoover Dam and then dropped back through turbines, and the best batteries offer 200 watt-hours per kilogram of energy whereas gasoline delivers 140,000 watt-hours per liter, according to Caltech’s Lewis. ‘There is nothing that can come close to the gravimetric and volumetric density of liquid fuel,’ ARPA–e’s Toone notes. ‘It’s hard to see how you electrify long-distance trucking and impossible to see how you electrify long-distance flight.’” – Scientific American