The Greenbox would be installed in the vehicle exhaust system and is supposed to be able to capture up to 95 percent of the greenhouse gases from a tankful of fuel. The box could be exchanged for an empty one at each fill up. The greenbox would be sent an algae bioreactor where the CO2 would be used to feed the algae. The algae would then be used to produce biodiesel. The fuel would then be used as a clean alternative to petroleum.
If this thing actually works it could both solve the problem of carbon emissions and renewable fuels. We'll just have to wait for some more independent test results.
[Source: Reuters, thanks to Manu for the tip]