| Quick 'back of the envelope' (literally) calculations: Toyota Camry [0] Dual VVT-i engine gets 7.9L/100km and 183gm/km emissions. That roughly works out as 2.3kg CO2 per 1L petrol. Therefore, a tonne of CO2 is produced for every ~430L petrol. Petrol is around AUD $1.40/L, so about AUD $600 of petrol. Carbon credits [1] are worth about $14 euros per tonne of CO2, which is say AUD $19. Therefore 'carbon neutral' petrol adds about AUD$20 to AUD$600 worth of fuel, or about 3-4%. Sound about right? I could stomach that, considering the fuels price goes up and down all the time anyway... [0] http://www.toyota.com.au/camry/features/economy-and-environm... [1] http://www.goldstandard.org/blog-item/carbon-pricing-what-ca... EDIT: formatting... |
(This page confirms Toyota's number: http://www.eia.gov/tools/faqs/faq.cfm?id=307&t=11 )
The answer, which took me far too long to realize, is that the oxygen pulled from the air makes up the bulk of the mass of the CO2. Oxygen has an atomic mass of ~16 to Carbon's ~12, which means that 1kg of pure carbon can be combined with oxygen to produce ~3.7kg of CO2.
So yes, your calculations sound about right. Contrary to my first impression they do not violate the law of conservation of mass.