Like a thumb, carbon footprint is unique

UC BERKELEY (US) — Who you are and where you live have more of an impact on the size of your carbon footprint than what kind of grocery bags or light bulbs you use.

“Everyone has a unique carbon footprint,” says Christopher M. Jones, a staff research associate at University of California, Berkeley. “There is no one-size-fits-all set of actions that people should take.”

Carbon footprints are a measure of the greenhouse gases released during the production, use and disposal of products and services. The production phase includes all of the processes between the time raw materials are extracted from the Earth until they reach consumers as finished products in stores.

A new study, published in the journal Environmental Science & Technology, considers the carbon footprint of all household economic activity, including transportation, energy, food, goods, services, water, and waste.

The report highlights the carbon footprints of two fictitious households: an upper-income couple living in San Francisco with no children, and a middle-income family with three children living in St. Louis, Mo. Each of these households contributes to the atmosphere about the same amount of greenhouse gases per year, but the sources of those emissions are very different.

Motor vehicles and air travel are the largest sources of emissions for the San Francisco couple, while electricity and food dominate emissions for the St. Louis family, so the opportunities to reduce emissions are vastly different.

For the West Coast household, improving the fuel efficiency of their motor vehicles from 20 miles per gallon to just 25 miles per gallon would save the equivalent of completely eliminating electricity in their home. In environmentally conscious San Francisco, going further by driving gas-sipping hybrids may also enhance the couple’s social status.

The Midwest family, on the other hand, can save over $100 per month, or 5 percent of their monthly net income, by making healthier low-carbon food choices, such as reducing calories and buying chicken, fruits, and vegetables instead of red meat, dairy, and processed foods. Cutting electricity consumption by 20 percent would save them an additional $30 per month. Driving a slightly more efficient vehicle could save the household $50 per month and much more with ultra fuel-efficient vehicles, but this benefit must be balanced with safety concerns and convenience, given the demands of raising three children.

The study analyzed typical household carbon footprints in all 50 U.S. states, 28 regions, six household sizes, and 12 income brackets for a total of several thousand possible combinations of household types.

The analysis is summarized in an online carbon calculator, that can be used by consumers to estimate his or her carbon footprint and identify the areas where lifestyle changes would create the largest reduction in greenhouse gas emissions.

“Our primary message is simple: If you are concerned about reducing your carbon footprint, or the carbon footprint of others through policy, it is important to focus on the actions that lead to the greatest reductions,” says Daniel Kammen, professor of energy and resources.

“Comparative feedback is very important. People want to know how well they are doing compared to people like themselves,” Jones said.

For typical U.S. households, the report claims about one-third of emissions are from transportation, a little more than 20 percent are from household energy, and about 15 percent are from food. All other emissions are from goods, services, housing construction, water, and waste.

“If you want an effective program to reduce emissions, it is essential to recognize that individuals have different values, attitudes, beliefs, habits, and abilities,” Jones says.

“Most people are willing and many are actively seeking how to live more climate-friendly lifestyles. The question is whether we can do it fast enough to reduce some of the worst impacts of climate change. Figuring out what makes the greatest impact seems like a good first place to start.”

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