May 1, 2008
Homeless Americans have big carbon feet
Americans who consume the lowest amount of energy are still producing carbon emissions per head more than double the global average. That’s according to a class of students at MIT, US, who calculated the carbon footprint of lifestyles ranging from homeless people, Buddhist monks, and five-year-old children to multimillionaires such as Bill Gates and Oprah Winfrey.
In general, emissions rose as income increased – the class estimated Bill Gates’ impact as about 10,000 times the average.
"Regardless of income, there is a certain floor below which the individual carbon footprint of a person in the US will not drop," said Timothy Gutowski, a mechanical engineering professor at MIT, who led the study.
While the students found that the average annual carbon dioxide emissions per person in the US was 20 metric tons, the world average is four tons. Even the US lifestyle with the lowest emissions – a homeless person who ate in a soup kitchen and slept in homeless shelters – had a footprint of 8.5 tons.
One factor behind this seemingly too high footprint is that the class divided equally emissions from government services available to everyone in the US, such as police, roads, libraries, the court system and the military. Carbon from education and Medicare (health) services, on the other hand, was allocated only to people who made use of them.
The students examined 18 lifestyles, using published sources to determine the carbon footprints of the rich, and detailed interviews to evaluate the others. They derived a system they dubbed ELSA – Environmental Life Style Analysis.
The lifestyle with the lowest energy usage was that of a Buddhist monk who lived in the forest for six months of the year and spent $12,500 annually. This gave him a carbon footprint of 10.5 tons.
Unlike some other footprint studies, the team was careful to take the "rebound effect" into account. This includes an analysis of how a person might spend the money they’ve saved by making an environmentally-friendly choice – such as using a hybrid car instead of a "gas-guzzler". If this extra cash goes on a long-haul flight, for example, the individual’s carbon emissions may actually increase overall.
"When you save energy, you save money," said Gutowski. "The question is, how are you going to spend that money?"
As expected, the biggest emissions factors in most people’s lives were housing, transportation and food. The students found that achieving significant reductions in an individual’s output would on the whole require drastic changes likely to be unacceptable to most people. This suggested significant limits to voluntary actions to reduce impacts, both at a personal and national level.
"The simple way you get people’s carbon use down is to tax it," said Gutowski. "That’s a hard pill to swallow – politicians don’t like to step up to support such measures."
The students will present their work at the IEEE International Symposium on Electronics and the Environment in San Francisco, US, in May.