New work from UC Berkeley shows the difference in household carbon intensity across the US by zip code, and probably affirms what many suspect – the suburbs are responsible for more carbon pollution on a per household basis then their core cities. Households in the center of large urban areas were found to emit 50% below the national average, while their suburban counterparts were found to emit 50% more. The study produced some great maps you can use to explore your region.
A couple of things are unique/interesting about this study over other core/burbs environmental footprinting efforts, however. This one used econometric data and accounted for consumption of goods and services, not just the typical bubble-over-the-city approach which only looks at things coming out of tailpipes and chimney stacks. Household income and expenditure surveys were used to estimate greenhouse gas footprints from goods and services, a key piece that is missing from many inventories.
By looking at economics as well, this study captured more nuance about urban form and emissions:
Increasing population density alone, for example, appears not to be a very effective strategy for reducing emissions. A 10-fold increase in population density in central cities corresponds to only 25 percent lower greenhouse gas emissions, and “high carbon suburbanization results as an unintended side effect,” Jones said.
Increasing population density in suburbs is even more problematic, he said. Surprisingly, population dense suburbs have significantly higher carbon footprints than less dense suburbs, due largely to higher incomes and resulting consumption.
What’s up in the Twin Cities? There’s definitely a range in emissions with the expected pattern, but most of the difference is due to transportation and housing size, not so much the difference in goods and services consumed. And if you look at the map of just household energy carbon footprint, you can see emissions from the home are dominated by electricity, since we’re in the coal-heavy Midwest. Many western states have very low electricity emissions, but have higher transportation emissions.
Carbon solutions should be tailored to their location, the study notes. In the suburbs, there’s a lot more space for solar, and that solar could be used to electrify the transportation system. A separate Australian study found that urban locations up to 12 dwelling units per acre would much produce more than their daytime consumption (keep in mind Australia is a sunny place), with the excessive being used for the transportation system.
The UC Berkeley study is producing estimates, not actual measurements, but they are fairly robust. They use local emissions coefficients for electric grids, for example. Transportation and income data come from the Census and other sources. The fact that they’ve added consumption data to help broaden the conversation beyond our buildings and cars alone makes this a significant contribution. Plus the cool maps.
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