Greenhouse Gas Emissions and Miles Per Gallon – Have We Got It Wrong?

 Carbon Footprint

There is a drive now, from many sources, to have the US achieve an 80% reduction in greenhouse gas emissions by 2050.  This is a laudable goal that, on the face of it, seems to be achievable.

We owe it to ourselves, though, to understand just what it means to reduce carbon emissions by 80%.

In 2006 the US emitted 5.8 billion metric tons of carbon dioxide. That is about 20 tons a year for each of us.  That means that a US goal of an 80% reduction would put us close to 1 billion tons by 2050.  If the Census Bureau has figured things right our population should be about 420 million which means that per capita emissions would have to fall to about 2.5 tons per person.

The last time the US had carbon emissions of a billion metric tons was probably around 1910 when the population was 92 million people.  So even back then carbon emissions were about 10 tons per capita.

So how do you get to 2.5 tons per person?  The only nations that emit at that low a rate are so poor that you wouldn’t want to live there.  Somalia?  Belize?  Would you want to live in poverty without adequate sanitation and clean water for the sake of carbon emissions? 

Looking at the industrialized nations that have the lowest carbon emissions is an eye opener.  France and Switzerland both generate almost all their electricity from non-fossil fuels yet they still emit 6.5 metric tons per person.

Our cars and truck consume about 180 billion gallons of fuel every year.  This would have to drop to 31 billion gallons in order to meet the 2050 goal.  Even if everyone only drove Toyota Priuses we would still exceed the goal by 40%.

Much of the information I used above was gleaned from the 2008 Index of Leading Environmental Indicators which is available online.


Gallons per Mile

The old joke about measuring a Hummer’s fuel consumption in gallons per mile instead of miles per gallon may just be the better approach to establishing a vehicle’s fuel efficiency.  How can that be?  A couple of professors from Duke started posing questions to each other during their daily commute in a hybrid car.

For instance:  Which saves more money for the car owners – changing from a car that gets 10 mpg to one that gets 20 mpg or changing from a car that get 25 mpg to one that gets 50 mpg?

Doing the actual math provides a surprising answer.  In the first case the consumption goes from 10 gallons per 100 miles to 5 which save the cost of 5 gallons per 100 miles driven while the second case goes from using 4 gallons per 100 miles to 2 or a reduction of only 2 gallons per 100 miles.

Watch the video and see what they mean:

This entry was posted in Cars. Bookmark the permalink.

4 Responses to Greenhouse Gas Emissions and Miles Per Gallon – Have We Got It Wrong?

  1. Noel says:

    Seems to me the reduction goals are not realistic and need to be adjusted to be in line with reality. But then it’s the government that is setting these goals and they’ve been out of touch with reality for a very long time.

    Some of the carbon footprint stuff is smoke and mirrors from organizations with an agenda. That’s OK, but it makes getting to real numbers pretty hard. For example, in my household we are conservative with electrical usage, use laptops instead of desktop computers, have only one TV, only use air conditioning when it’s really hot, don’t commute (2 work at home businesses), drive 4-cylinder cars, and heat with a combination of oil and wood (this in New Hampshire). Seems like we’d be good. But no.

    I happen to fly about 60,000 miles a year. So my carbon footprint looks like we are really bad people who waste energy right and left. Is there a truly accurate way to measure it? I don’t know, but it sure would be nice to find one.

  2. Tim says:

    I’ve seen the gallons per mile discussion before and it certainly would make things easier for people who don’t want to *think* about what they are doing.

    5 gallons per 100 miles, or 10 gallons per 100 miles? Gee, which consumes more fuel and by how much? Even the dumbest of the dumb should be able to get that one. But wait, we’ll be surprised by someone…

  3. Noel says:

    The car I rented last month in Germany and Switzerland had a trip computer that showed fuel usage but did it more on the gallons per mile model.

    The fuel calculator used liters per 100 kilometers, which when you see it displayed in digits on the dash, is a lot more graphic than MPG figures. A liter is about a quart, so you need four of them to make about a gallon. Now if the car computer is showing you, say 10 liters per 100 km, you are getting about 23.5 mpg. But if you are showing 7 liters per 100 clicks, you’re pulling down 33 mpg. On the other hand, blasting down the A3 and A5 at 160-180 kph, I was getting about 16 MPG at 15 liters per 100 km. Climbing one long pass in the Alps, it was more like 20 liters per 100 km.

    The point is that the gauge really showed *consumption* in a more informative way. We think of cars as *getting* a certain mileage. This showed how much I *used.* Once I understood what was happening it was fun to see how little I could use.

  4. Mark says:

    On the macro level , I have 2 problems with all of this and wonder why more people haven’t cried foul ball, given the direction our policies are headed.

    First off – the entire focus to counter global warming is on greenhouse gases, like C02. That’s really only part of it. We are not looking at the changing thermal behavior of the planet. We are paving everything, and all the concrete and asphalt is collecting solar energy, storing it as heat, and readiating it back into the atmosphere. The temperature does not drop at night as much as it used to. I don’t hear ANY talk about this. Why not?

    Second, even focused on CO2 – it’s an equation, and we are ONLY putting legislation toward reducing the production. Well, guess what? WE produce it ourselves everytime we exhale, and there are more and more people everyday, plus more animals for pets and for food. But nature designed a great system, and our green friends, the plants just so happen to take in that CO2 and return O2 to us in it’s place.

    So yes, we could curb production of CO2, AND / OR we could increase the vegetation density. Oh, bad news on that Jim, we are clearing the trees away as fast as we can to make room for more heat sinks, I mean shopping malls and sub-divisions with a few ornomental trees put back here and there.

    Why does nobody get this? The answer is in front of all of us, and yet?


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s