Carbon emissions are typically tracked at the country or city level, with the focus occasionally narrowed even more onto a county or Census tract. On a global scale that approach provides a pretty helpful window onto problem areas. If metro areas hope to reduce greenhouse gases further, however, they need to zoom in on those precise spots in the city doing the most damage to the environment.
That's the concept behind a new software system called "Hestia," after the Greek goddess of the hearth, capable of tracing carbon emissions down to individual urban buildings and roads. The Hestia project runs numerous public data sources — local air pollution reports, traffic counts, tax assessment information, and the like — through a modeling system that spits out high-resolution, site-specific greenhouse gas maps of a metro area. The system is sophisticated enough to discern fluctuations in each site's emissions on an hourly basis.
As Smithsonian's "Surprising Science" blog reported last week, the research group developing Hestia just released its initial results in a recent issue of the journal Environmental Science & Technology. The researchers, led by Kevin Gurney of Arizona State University, reported their analysis of carbon emissions for the city of Indianapolis. Gurney and company created three-dimensional maps of the city's commercial, residential, and industrial buildings; major and minor roads; and other energy producers from power plants to airports:
The buildings of Indianapolis show some pretty clear emissions patterns. Residential buildings form a satellite of carbon clusters outside the city center along the routes into suburban subdivisions. Commercial emissions form several spokes extended out from a concentrated area in central Indianapolis. Industrial emissions are a bit more scattered but generally follow major transport routes across the metro area. Hourly reports show, predictably, that commercial buildings emit more gases during daytime hours and residences emit more at night.
Major roads are home to most of the city's transportation-related emissions. Though urban interstates and major arterials make up just 15 percent of Indianapolis roadways, they produce 62 percent of its road carbon emissions. Minor arterials, while making up just under 10 percent of road length, produce 22 percent of emissions. Local roads are the most extensive but the least pollutive. Again, as expected, a spike in greenhouse gases occurs during the morning and evening rush hours.
The Hestia system pinpoints the two biggest climate offenders in the metro area as the Harding St. Power Station, a coal-burning plant near the city center, and Indianapolis International Airport. Both are located in Decatur, which is tops among the metro's nine townships in Hestia's emissions rankings for the city. The system also showed a seasonal trend toward greater production in winter — the result of increased heating. Hestia developers released a video of their Indianapolis results along with their paper last week:
The Hestia team is in the process of expanding its analysis to Los Angeles and Phoenix. Gurney and colleagues consider the system "general enough to be applied to any large U.S. city" and hope to create emissions data assessments for every major metro area in the country. Ultimately they believe the tool will help cities target environmental trouble spots and prepare specific, efficient policy responses. They conclude:
High-resolution emissions quantification with functional detail can also aid in the decision making necessary to achieve lowest cost emission mitigation efforts. Knowing the quantities and spatial distribution of fossil fuel CO2 emissions in a city allows for targeting areas with high-impact/low-cost solutions.
Map image via Gurney, K.R. et al., "Quantification of Fossil Fuel CO2 Emissions on the Building/Street Scale for a Large U.S. City," in Environmental Science & Technology, dx.doi.org/10.1021/es3011282; video courtesy of The Hestia Project.