Hajji, the car I ran on waste vegetable oil was technically zero emissions, as the CO2 it produced was already a result of carbon capture by the plants that supplied the oil (zero emissions, if you discount the comments about mobile BBQs). 100% solar powered. I would guess that it would be far more efficient to use the sewage for palm plantations to produce a high yield palm oil and run cars on that. The distribution systems are already in place, the fuel is relatively safe as it is not easily ignited and is completely non-toxic and it will run in existing Diesel engines with a slight modification; and older Diesels with no mods.
