Author Topic: Car decision & general thought/question on environmental impacts  (Read 367 times)

Huskie87

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I recently purchased a new home with the intention of being able to bike to work, which I'm looking forward to.  I used to have a 20 mile round trip commute, now I'll be biking 4 miles a day.

With us essentially cutting down to one car, and me being concerned with environmental issues, I've been thinking about the best vehicle we could purchase.  Initially I was excited to go test drive a new Rav4 Hybrid (40 mpg) but my wife and I were both a bit disappointed with the quality of the interior of the vehicle, considering the $30-40,000 price tag. 

I also thought about a Tesla, but charging my vehicle with electricity generated by the local coal fired power plant doesn't seem like a net-benefit to the environment.

This got me thinking about older, less fuel efficient vehicles.  We know that a significant portion of the environmental impact of a car comes during manufacturing.  Taking cars out of service to buy new ones that are more energy efficient isn't necessarily a net-benefit to the environment.  Couldn't an argument be made that buying a used car, say with 120,000 miles, and taking really good care of it, would be the most environmentally friendly form of car ownership? 

Say you're able to squeeze 40,000 extra miles out of a car that gets 20mpg, versus buying a new one at 40mpg.  That's going to mean you'll burn 2,000 gallons of gas vs. 1,000 gallons.  On a pure fuel basis, you're definitely not helping the environment, but that ignores the fact that you're delaying the manufacturing of an entire vehicle for years.  Sure, some pieces of a vehicle can be reused, but not without significant energy, and most of the pieces are thrown in the garbage.  I have to believe this route is better for the environment.

Appreciate any help as I try to think through the right decision here.

robartsd

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Re: Car decision & general thought/question on environmental impacts
« Reply #1 on: July 09, 2019, 10:10:43 AM »
Energy to make a typical American car: 119,150 MJ

Energy in a gallon of gasoline: 120 MJ/gal * 1000 gal = 120,000 MJ

If you attribute all of the energy to make the car to those last 40,000 miles, you might be right. However, the embodied energy should deduct the reduced energy to recycle materials vs. processing new materials. It takes about 4x as much energy to create steel from ore than to recycle it - about 98% of steel in cars is recycled - recycling 500 lbs of steel saves about 12000 MJ of coal. Also the embodied energy of the car should be amortized over it's entire life. Extending the live of the car from 120k miles to 160k miles you can claim to be saving 25% of the embodied energy or about 27000 MJ. Net extra energy used: 93,000 MJ. If some of the embodied energy was renewable rather than fossil fuel, the picture is even worse.


RWD

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Re: Car decision & general thought/question on environmental impacts
« Reply #2 on: July 09, 2019, 10:32:06 AM »
But there are also older vehicles that also get good fuel economy. It's not necessarily one or the other.

[vehicle], [KBB retail price], [combined mpg]
2011 Nissan Leaf, $6k, 99 MPGe
2010 Toyota Prius, $9k, 50 mpg
2009 Honda Fit, $6k, 29 mpg
2006 Honda Civic Hybrid, $4k, 42 mpg
2005 Honda Insight, $4k, 52 mpg
2005 Toyota Prius, $5k, 46 mpg

Syonyk

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Re: Car decision & general thought/question on environmental impacts
« Reply #3 on: July 09, 2019, 12:25:36 PM »
I also thought about a Tesla, but charging my vehicle with electricity generated by the local coal fired power plant doesn't seem like a net-benefit to the environment.

If 100% of your power, all the time, is generated by coal, you're about a wash with a Prius in terms of emissions.

If less than 100% of the power is coal, and/or your area is adding solar/wind production, that becomes cleaner over time.

In any case, buy a used Volt: https://syonyk.blogspot.com/2019/07/i-bought-used-chevy-volt-and-you-should-too.html

Chaplin

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Re: Car decision & general thought/question on environmental impacts
« Reply #4 on: July 09, 2019, 08:01:42 PM »
If 100% of your power, all the time, is generated by coal, you're about a wash with a Prius in terms of emissions.

This fits with various versions of maps I've seen of the US showing the MPG you would have to get in a gas-powered car to have the same emissions as an EV charging on the local grid. Here's one version of those maps: https://energypost.eu/charging-an-electric-vehicle-is-far-cleaner-than-driving-on-gasoline-everywhere-in-america/

Bottom line: even on a 100% coal-fired grid (which is now rare and generally moving in a better direction), an EV will have similar emissions (including embodied emissions) to a Prius over a reasonable lifetime.

Spondulix

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Re: Car decision & general thought/question on environmental impacts
« Reply #5 on: July 09, 2019, 09:10:27 PM »
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