Hur de har räknat framgår säkert av studien men i
sammanfattningen står redan lite om det:
Citat:
E-bikes in China are the single largest adoption of alternative fuel vehicles in history, with more than 100 million e-bikes purchased in the past decade and vehicle ownership about 2× larger for e-bikes as for conventional cars; e-car sales, too, are rapidly growing. We compare emissions (CO2, PM2.5, NOX, HC) and environmental health impacts (primary PM2.5) from the use of conventional vehicles (CVs) and electric vehicles (EVs) in 34 major cities in China. CO2 emissions (g km–1) vary and are an order of magnitude greater for e-cars (135–274) and CVs (150–180) than for e-bikes (14–27).
CO2 utsläppen blev alltså bara något större för elbilar än vanliga bilar i varje fall om man tar ett snittvärde av siffrorna.
Citat:
PM2.5 emission factors generally are lower for CVs (gasoline or diesel) than comparable EVs. However, intake fraction is often greater for CVs than for EVs because combustion emissions are generally closer to population centers for CVs (tailpipe emissions) than for EVs (power plant emissions). For most cities, the net result is that primary PM2.5 environmental health impacts per passenger-km are greater for e-cars than for gasoline cars (3.6× on average), lower than for diesel cars (2.5× on average), and equal to diesel buses[/u]. In contrast, e-bikes yield lower environmental health impacts per passenger-km than the three CVs investigated: gasoline cars (2×), diesel cars (10×), and diesel buses (5×). Our findings highlight the importance of considering exposures, and especially the proximity of emissions to people, when evaluating environmental health impacts for EVs.
De väger alltså in att elcentralerna står utanför tätbefolkade områden men trots det är skillnaden i utsläpp så stor att hälsoeffekterna pga PM2.5 halterna i luften ändå blir negativt för elbilarna jämfört med bensinbilar. Det tycker jag är ganska anmärkningsvärt eftersom man skulle tro att elbilar hur som helst ger renare stadsluft och de kallas ju även ZEV (zero emmission vehicles).
Etanol och biogasbilar borde stå sig ännu bättre i jämförelsen eftersom de har lägre partikelutsläpp än bensinbilar.