And now for some slightly useless information. Someone has actually been able to do the hard data & calculations. Before we give the answer i'd be nice to see in a poll what you think. Bonus points if you tell us by what margins. Not to get all scientific on you but its assuming we are comparing the same amount of energy expended. (pollution = CO2) So go ahead, let us know what you think and the answer after the break... Back from the break... First of all there were some mention as to CO2 is a pollutant or not. It depends on how you define a 'pollutant'. Just about anything can become toxic in high enough a concentration. Let us just say to assuage some sensibilities the terminology should have been "higher rate of CO2 emmission" although it's a mouthful. And please do not take this too seriously, this is just a fun exercise. There's too many variables but at least it provides a bit of a picture. All numbers are metric it's easier to calculate. So here we go... 1L of gas gives off 2.88kg CO2 after combustion. Or volumetric mass of gasoline = 0.75 Where 750g of gas = 2.88kg of CO2 in addition 1g of gas generate 13.35 Wh Therfore 1lbl gas generate 6008W But a 1lbl of wood generate 8500BTU = 2428W It means that if it takes 15 Litres (4 US Gallons) of gas to travel 300 Kms (185 miles) it would take you 28.12kg (62 lbs) of wood to develop the same energy. 15L of gasoline will emit : 43,2kg of CO2 28.12kg of wood : 4.22kg of CO2 Which means a car emits about 10 times more CO2! Yah baby, my Ferrari does 150 miles per face cord!