Which Philadelphia-area zip codes have the biggest carbon footprints?

Philadelphia households have much smaller carbon footprints than their suburban counterparts.

That's what a new interactive map, posted online by University of California-Berkeley researchers, shows.

Cities nationwide contribute far less greenhouse-gas emissions per person than the less-dense suburbs, the scholars found.

The Berkeley study, which is being published in the journal Environmental Science & Technology, used 37 variables to approximate the greenhouse-gas emissions produced by transportation, food, goods, services and home energy use in nearly all U.S. zip codes.

In the Philadelphia region, emissions per person vary greatly among city and suburban zip codes.

The zip code 19103, near Rittenhouse Square in Center City, has an average yearly household carbon footprint equivalent to 28.3 metric tons of carbon dioxide. The 19107 zip code in Society Hill has an even lower footprint, equivalent to 24.6 metric tons.

But those numbers skyrocket in the suburbs. Some of the highest in the region include 19035 in Gladwyne, Montgomery County, with an average annual footprint of 81.7 metric tons of CO2; 18954 in Richboro, Bucks County, at 73 tons; and 19373 in Thornton, Delaware County, at 72.1 tons.

In general, Philadelphia and Camden zip codes emit CO2 loads in the 20-to-40-ton per household range, while most suburban zip codes have footprints of 40, 50 or 60 (or more) tons per household.

The cities and suburbs in the region also differ in the types of emissions they produce.

In the suburbs, most greenhouse-gas emissions are from transportation. But in Philadelphia and Camden, housing generally makes up the largest part of the carbon footprint, with food ranking above transit in many zip codes.

"The goal of the project is to help cities better understand the primary drivers of household carbon footprints in each location," Berkeley's Daniel Kammen, a professor and and director of the Renewable and Appropriate Energy Laboratory, said in a statement. "We hope cities will use this information to begin to create highly tailored climate action plans for their communities."