MIT tracks carbon footprints of different lifestyles

The analysis was carried out by Gutowski and 21 students in his 2007 class “Environmentally benign design and manufacturing.” They derived a system for making such comparisons, which they call ELSA-Environmental Life Style Analysis.

Unlike some other attempts to quantify people's carbon emissions, Gutowski and his students took great care to account for often-overlooked factors such as the “rebound effect.” That's when someone makes a particular choice-for example, buying a hybrid car instead of a gas-guzzler-but then uses the money saved from their reduced gasoline costs to do something else like taking a long trip by airplane. The net impact, in such a case, may actually be an overall increase in carbon emissions.

“When you save energy, you save money,” Gutowski explains. “The question is, how are you going to spend that money?”

The students looked at the factors within each person's control that might lead to a reduction in their carbon output. They found that achieving significant reductions for the most part required drastic changes that would likely be unacceptable to most people. As a result, they said, “this all suggests to us very significant limits to voluntary actions to reduce impacts, both at a personal level and at a national level.”

In a continuation of the class this semester, another group of students are exploring this question in more detail, looking at just what kinds of things people really can do to limit their environmental impact. The question they are addressing, Gutowski says, is “can average Americans tighten their belts” in a way that would make a significant difference. Once again, the class will be interviewing people living in a wide variety of ways, including an Amish farmer. Then, after analyzing the results and possible changes, they will go back to the same people and ask, “would you consider these alternatives?”

In general, spending money on travel or on goods that have substantial energy costs in their manufacture and delivery adds to a person's carbon footprint, while expenditures on locally based labor-intensive services-whether it's going to a therapist, taking an art class, or getting a massage-leads to a smaller footprint.

But the biggest factors in most people's lives were the well-known obvious energy users: housing, transportation and food. “The simple way you get people's carbon use down is to tax it,” Gutowski says. “That's a hard pill to swallow-politicians don't like to step up” to support such measures. Absent such national actions, he says, it is important to study “what role consumer choices can play” in lowering the nation's carbon emissions.

If nothing else, the members of this class got a whole new perspective. “The students really got into it,” Gutowski says. “It raised everybody's awareness about the issues.”

Written by David Chandler, MIT News Office