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: