The calculator helps you determine how much you pollute and generates a cash donation level that will be used to plant trees

By Mark Berkey-Gerard

How many trees do you have to plant in Fairmount Park to make up for the environmental impact of driving to work, heating your house, and taking an airplane trip to Florida for vacation?

Last week, the city released a Web-based tool called Erase Your Trace, which aims to get Philadelphia residents to consider that question and take action to reduce individual greenhouse emissions.

Philadelphia’s carbon calculator — which is similar to ones created by the EPA,  environmental groups, private companies, and Al Gore — asks residents to enter their heating and electric bill, record recycling habits, track how far they drive annually, and account for all business and vacation air travel. It then totals up all the carbon dioxide emissions and offers suggestions to reduce them.

At the end of the process, participants are given a dollar amount and a direct link to make a donation to the Fairmount Park Conservancy. The average Philadelphian produces 10.2 tons of carbon dioxide annually, “costing” the environment approximately $200 each year – roughly the cost of planting one tree in an urban area,  according to the city.

The carbon calculator is designed to educate residents about the environmental impact of their daily routine and offer concrete ways to respond locally.

“I’ve donated money to these types of things before, but often it goes to plant trees in India or to build a wind turbine in Texas,” said Christine Knapp of the environmental organization PennFuture and member of the mayor’s sustainability advisory board. “This meets the specific needs of the city.”

Given the recession and the city’s budget woes, it is also a direct effort to raise money for Mayor Michael Nutter’s ambitious goal of planting 300,000 trees by the year 2015.

But how accurate is the city’s carbon calculator? And what makes it unique to Philadelphia?

While there are dozens of these Web based tools, there is no one standard for calculating an individual’s carbon footprint.

Fred Heutte, the chair of the Sierra Club’s Global Warming and Energy Committee, has surveyed many different carbon calculators and says that each one is built on assumptions. And it is impossible to get a precise measurement because there are so many variables for each person and each action. For example, if an airline flight from Philadelphia to London is full of passengers, the calculation is different than if there are only a few passengers.

However, Heutte said that many of the assumptions used to Philadelphia’s calculator are particular to the area.

While the tool uses national formulas from U.S. Forest Service and the Environmental Protection Agency, it also uses specific electricity rates from PECO, local rates for natural gas, and considers the kinds of items that can be recycled in Philadelphia. He also noted that a number of environmental organizations – both national and local – that had contributed to the project, which demonstrated that the city didn’t just replicate a generic tool with a new design.

“It’s good information, but the question is if it actually makes people change their behavior,” said Heutte.

Even trying the Philadelphia’s carbon calculator takes some effort.

The tool does not yet have a prominent spot on the city’s Web site or even on Greenworks, the Web page for the Office of Sustainability. And users must dig out electric and gas bills and then spend 15 minutes or so navigating the site. Then there is the donation to plant a tree.

“People should be prepared,” said Knapp. “My fear is that people will look for an instant calculation.”

Mark Berkey-Gerard teaches online journalism at Rowan University in Glassboro, New Jersey.