According to this energy.gov web page, I consume about 130,000,000 Btu's each year. 130 million Btu's translates to about 38,000 kWh. A 1500 watt hair dryer running for an hour uses 1.5 kWh, so 38,000 kWh is a lot of hair-drying, like 25,000 hours worth.
An important consequence of my energy consumption is the carbon dioxide generated as a result. A really neat and easy-to-use calculator at nature.org tells me that I'm personally responsible for 30 tons of carbon dioxide every year through my energy use (assuming I drive a gasoline-powered car; more on this shortly). The average American is responsible for 27 tons, and the world average is 5.5 tons. I'm quite a carbon dioxide hog.
My energy use is divided into several portions -- transportation, heating, electricity -- the big three -- and some others.
In this post, I'll look at my transportation energy use, and what I can do with transportation to reduce my carbon dioxide footprint.
Transportation can be divided into several portions itself, including getting myself around, and getting the stuff I buy transported from where it is made to where I buy it (often across an ocean and then by land across a continent). In this post, I'll focus just on the transportation energy to get myself around.
Assuming I have a gasoline-powered car, and drive it, say, 12,000 miles each year, and get an average of 30 mpg, I use 400 gallons of gas per year. One gallon of gas produces 18 lbs of carbon dioxide, so my driving produces 7200 lbs; rounding up to 8000, this is 4 tons. So of my 30 tons, 4 tons results from driving.
About a year ago, we purchased an electric vehicle (EV), a Nissan Leaf. A question is whether driving an EV can significantly reduce the carbon dioxide produced by getting me around.
Let's assume I drive the same 12,000 miles with the Leaf. The Leaf averages about 4.8 miles per kWh (if I don't drive it aggressively or excessively fast), which means the Leaf consumes 2500 kWh in one year. For each generated kWh of electrical energy, about 1.25 lbs of carbon dioxide are produced, which means that the carbon dioxide produced by the electricity generation for the Leaf is 3125 lbs, or about 40% of the carbon dioxide my gasoline car produces. This is disappointing. I was hoping to find that the Leaf made my driving carbon dioxide generation essential nothing.
However the above overly-simplistic calculation cuts the Leaf short. For local driving, especially in traffic jams that are common in Massachusetts during commute time, the Leaf really shines. Let's see how taking that into account changes the carbon dioxide calculation.
In a traffic jam, especially during the first few miles when the engine is warming up, my gasoline car gets as little as 5 to 7 mpg (it has a display that shows mileage history, so I'm pretty confident in this number). The Leaf, in the meantime, gets as much as 7 or 8 miles per kWh under these conditions.
Let's say that one fourth of my driving is in congested traffic, or 3000 miles per year, at, say, 7 mpg for the gasoline-powered car. This corresponds to about 425 gallons of gasoline, resulting in 7700 lbs of carbon dioxide. So in slow traffic, the gasoline-powered car produces more carbon dioxide than it would all year if it never encountered traffic jams (should we be so lucky! :-) ).
Meanwhile, in traffic jams, the Leaf gets (conservatively) 7 miles per kWh. Driving 3000 miles at this mileage causes the Leaf to use only 425 kWh, which corresponds to about 530 lbs of carbon dioxide -- about a quarter of a ton. By comparison, the gasoline-powered car generates nearly 4 tons!
For the remaining 9000 miles of non-traffic jam driving, the gasoline-powered car produces 5400 lbs, or more than 2.5 tons, while the Leaf produces about 2400 lbs, or about 1.25 tons.
The bottom line, then, is that the gasoline-powered car's yearly output of carbon dioxide is 4 + 2.5 equals 6.5 tons, while the Leaf puts out 0.5 + 1.25 tons equals 1.75 tons, for a net reduction of about 5 tons!
So of my 30 tons of annual carbon dioxide output, probably a realistic figure is that about six tons would result from driving my gasoline-powered car. I drive the Leaf almost all of the time, and by doing so, my annual carbon dioxide output is five tons less than the calculator claims I produce. Thus my total yearly carbon dioxide output when I drive the Leaf is 25 tons, not 30.
It sounds like driving an EV makes sense if you're concerned about the rising carbon dioxide. Even better, it sounds like driving less, and especially avoiding traffic jams, would help significantly.
The next post will discuss some unfortunate things we've done to lock ourselves into high energy usage and carbon dioxide output.
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