When it comes to transportation, "green" has something in common with sports cars. The more sporty (or green) your transportation, the less practical it is for a family with three kids and a mortgage.

But let's say that's not your situation. You don't have any kids to drive to school and grandma doesn't expect you to run her to the store every week. You're in your 20's and everywhere you need to go is within fifteen miles of your apartment. Let's say also that living green is a major priority in your life. What's the greenest possible way to travel?

For green living, you obviously you can't beat walking or bicycling. It's a lifestyle that works well for many people in urban and campus settings.

If you need to go beyond personal power, public transportation is the next best possibility. Wikipedia claims that "for every passenger mile traveled, public transportation uses less than one half of the fuel of private automobiles, producing 5% as much carbon monoxide and less than 8% as much as the other pollutants that create smog."

If this is true, public transportation could be greener than even plug-in hybrid vehicles. Check out the graph below. This graph compares CO2 emissions from conventional cars with standard hybrids and plug-in hybrids with a 20 mile electric range. The thought here is that by moving CO2 emissions from individual engines to an electric power plant, CO2 emissions would be 60% less with a plug-in hybrid than a conventional car. That's pretty good, but it's not the 90+% less that Wikipedia claims for public transportation.

Another argument for public transportation is the environmental cost to manufacture vehicles. Any vehicle, no matter how green it is during its lifetime, has an environmental impact when manufactured. Certainly manufacturing a bus or subway train has an environmental impact. But when that impact is spread, pro rata, over the life of the train and the commuter-miles it logs during its lifetime, I'd wager it would win over any private vehicle.

But let's say that you need something that's faster than a bicycle and the last train's run for the night. What's the greenest private vehicle option?

Randall Parker wrote a couple of days back about the arrival of electric motorcycles. Electric motorcycles are the pinnacle of green for private vehicles.

Electric vehicles are always greener than vehicles powered by internal combustion - even when EV's are powered by coal-burning electric plants. It's an economy of scale: we get more power per unit of pollution from a single large electric plant than we do from many individual internal combustion engines.

Further, an electric motorcycle is greener than an electric car because less electric power is needed to push the smaller mass of the motorcycle.

But even among electric motorcycles there is a green hierarchy. One of the motorcycles that Randall Parker mentioned in his post – the Vectrix – gets demoted immediately because it uses nickel metal hydride batteries. Phil recently pointed out the environmental impact of those batteries.

The two motorcycles that use environmentally friendly lithium ion batteries tie for "greenest private vehicle." They are the "Zero" and the "Enertia."

The Zero

The Enertia

The Zero is being marketed as an eerily-silent motocross replacement. The Enertia is a commuter-bike. Both are plagued with a short 40 mile range and a slow 50 mph top speed. The Zero people are promising an optional 80 mile range in the future, but not yet.

These bikes are a humble beginning for electric motorcycling. I expect this to change quickly as better batteries allow greater speed and range.

UPDATE:

It's remarkable how often Phil and I, without planning, get on the same wavelength. He's got more on electric motorcycles over at L2SI.

UPDATE II:

I certainly don't live as green as the elites that this post is aimed at. I live in a rural setting with four kids and a wife. Personally, I'm looking forward to a green solution that has mass appeal - plug-in diesel hybrids.