Wasn't there a thing on Mythbusters where they compared bike and car emissions and the bike didn't come out well?
Not sure on that one, Will check it out But I know my bike runs along at loads more revs than my diesel does
I think the argument is that the test is flawed as cars get tested around 2-3k rpm in top gear to get a measurement but bikes get tested around 6-7k rpm in top gear which means the bike would be doing around 90-100mph which they say you wouldnt be doing normally and the car would be doing around 70mph. the test they did in Belgium used real world figures and found bikes were producing less emissions.
this was the bmf one Motorcycle Emissions - Bikes Go Greener cant find the belguim report atm, was on a facebook link but did find this Why commuting by motorcycle is good for everyone - Telegraph but the test needs to be changed as when you got bikes that do have higher co2 than some cars they were at the same time using less fuel so there was less particles in the emitted gas and its these particles that do the environmental damage, most manufactures refuse to even test their bikes which is why you will notice the majority of the time you wont see a co2 rating on your log book.There is a write up also somewhere from cambridge particle emissions that also showed that even the highest co2 producing bike was really low in harmful particles and would still pass the latest euro emissions laws.