Denver's Expanded Greenhouse Gas Inventory Grabs International Attention
How do you measure a city’s “real” carbon footprint? It’s a question scientists have asked for decades, and one that Anu Ramaswami has finally answered.
The engineering professor, along with her Ph.D. students at the University of Colorado at Denver, has pioneered the first-ever expanded carbon footprint computation. University officials say it’s the most sophisticated formula yet for measuring an entire city’s greenhouse gas emissions.
And scientists across the globe are taking note.
Ramaswami, who directs the university’s sustainable urban infrastructure programs, is now collaborating with researchers in nine international cities interested in replicating Denver’s method. These include Toronto, London, Geneva, Bangkok, Barcelona and Capetown. She’s also working with Portland, Seattle, and New York, among other major U.S. cities, as well the county of Los Angeles and a handful of Colorado towns.
So how does it work? Typically, cities measure carbon emissions within city limits. But Ramaswami’s methodology asks them to look further afield. Her formula includes emissions from airline travel, commuting trips, and the production of food, water, transportation fuel and cement, all activities central to urban life.
In developing the broader greenhouse gas inventory, Ramaswami worked closely with the city of Denver, which incorporated the new formula into its comprehensive climate action plan.
As part of the plan, Denver passed a law requiring that all city government projects use a concrete mix that is 20 percent fly ash–a byproduct of power plants that is typically thrown away.
“Unlike other cities that only measure common air pollutants,” says Ramaswami, “Denver counts the effect of producing its building materials as well.”
Because concrete is made outside of the city, manufacturing emissions are not included in typical greenhouse gas inventories.
“But if you’re counting the impact of concrete use in Denver,” says Ramaswami, “you have to include this.”
Denver is the first city in the country to require the use of green concrete.
The Environmental Protection Agency lists cement as the second largest emitter of carbon dioxide after fossil fuels. Producing one metric ton of cement emits one metric ton of carbon dioxide into the atmosphere, Ramaswami says. Using fly ash in concrete significantly reduces the amount of carbon dioxide that would otherwise be released into the air.
Ramaswami’s study, “A Demand-Centered, Hybrid Life-Cycle Methodology for City-Scale Greenhouse Gas Inventories,” was recently published by the Journal of Environmental Science & Technology.
“It’s inspiring to be able to work together with cities,” says Ramaswami. “It’s very collaborative and very exciting.”
(Photo courtesy of the University of Colorado, Denver)
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