As of the start of 2007, I am living in Cambridge, Massachusetts, and commuting 16 miles round trip by car at 35 mpg to GreenMountain Engineering in Waltham 250 days/year. That’s about 125 gallons of diesel per year, and I drive an additional 20% for other reasons. That’s around 150 gallons * 155 MJ/gallon = 25000 MJ/year = 25 GJ/year. Increase that by about a third to include the amortization of the energy used to build the car and transport the fuel before sale, according to the Institute for Lifecycle Environmental Assessment (summary of study by Maclean and Lave of Carnegie Mellon, 1988). That’s 33 GJ/year.

Additionally, I live in a house that consumes an average of 100 therms of natural gas and 400 kWh of electricity per month year-round. The total for the house is (100 therms * 105 MJ/therm) + (400 kWh * 3.6 MJ/kWh) = 10500 + 1440 MJ = 11940 MJ/year. I share the house with my girlfriend, so count this as 6 GJ/year. My office is similar in size to our house, but we have 4 employees, so add another 3 GJ/year. The total is now 42 GJ/year.

I eat about 2500 kilocalories of food per day, and that reflects 7500 kilocalories of energy used, once farming and transportation energy costs are included. I probably do slightly better than that buying local produce and eating mostly vegetarian. (The 3:1 ratio is from a 2002 paper by Leo Horrigan, et al., of the Johns Hopkins Bloomberg School of Public Health.) That’s the same as 7500 kilocalories * ~4 kJ/kcal = 30000 kJ = 30 MJ/day, which corresponds to 11 GJ/year. The total is 53 GJ/year. Virtually all of it comes from non-renewable resources (diesel, natural gas, and electricity from mostly coal).

This omits the amortized manufacture and transportation energy for the physical goods I buy–computers, books, furniture, clothes.

For reference, I’ve read of typical consumption rates for North America in the range of 200-300 GJ/year.

This entry was posted on Saturday, February 10th, 2007 at 4:59 pm and is filed under Alternative energy, Cambridge, Engineering, Green power, Renewable energy. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.