news Hestia carbon tracking model comes alive New model displays carbon emissions at street level BY A L E X M I LL E R E D I T O RS @N U V O . N E T
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team of researchers led by Kevin Gurney, a professor and researcher at Arizona State University, has recently developed a model that can predict carbon emissions on the street level. This model, named “Hestia” after the Greek goddess of the hearth, may prove essential in curbing and perhaps slowing the effects of global warming. One of the model’s first publicized runs utilized Indianapolis, providing the city with tangible emissions data while positioning Indianapolis as a strong representative for carbon emissions modeling nationally. Currently, the model tracks carbon emissions, particularly carbon dioxide, the compound most responsible for global warming. Carbon dioxide is one of many greenhouse gases. Other greenhouse gases include water vapor, methane, ozone and nitrous oxide. Despite common belief, carbon dioxide and other greenhouse gases are beneficial to Earth, and, without them, human life would not exist. Greenhouse gases trap infrared radiation, heating Earth to habitable temperatures. Without greenhouse gases, on average, Earth would be a chilling -0.67°F, a temperature well below the 59°F global average we enjoy today. When large amounts of anthropogenic carbon dioxide — carbon dioxide traced to human activity — are released into the atmosphere, however, Earth heats uncontrollably, resulting in global warming. For decades, scientists have studied carbon dioxide concentrations and their effects on the atmosphere. One of the first, and perhaps most famous, carbon dioxide stations in the United States is the Mauna Loa Observatory in Hawaii. It has been tracking atmospheric carbon dioxide concentrations since the late ’50s. Scientists have developed a number of computer-based models to measure carbon dioxide emissions. Taking data from various points across a region, researchers are able to project carbon dioxide emissions for a large area, typically the county- or Census tract-level. These models have left much to be desired. While these models can numerically predict carbon emissions on a regional level, they fail to pinpoint the exact coordinates of carbon emitters within a
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Kevin Gurney, professor and researcher at Arizona State University.
county. Instead of providing a precise location, they merely bunch all carbon emitters into one geographic result. The county itself becomes the carbon emitter, instead of each individual entity being a carbon emitter.
Along comes Hestia Hestia, unlike traditional carbon emissions models, measures carbon emissions at a much more granular level from roads and individual buildings. “I think we are the first effort to do something at this scale. We have taken a very different approach to solving this problem,” Gurney explained. Hestia uses traffic reports, among other data, to predict exact carbon emissions. The model can be modified for every part of the day and week, outputting results every hour. This flexibility allows researchers to compare high traffic times of the day, such as rush hour, with low traffic times of the day, such as the few hours after midnight. Gurney and his team chose Indianapolis for a number of reasons. For one, the majority of Indianapolis fits snugly within the boundaries of a single county. Furthermore, most of Indianapolis’ carbon dioxide emissions data is reported on the county level. Indianapolis also has flat and symmetrical terrain, and the city’s population is distributed fairly equally in all directions from the city center. Perhaps most important, Indianapolis is an “island” city, surrounded primarily by rural landscape. Because it is surrounded by rural land, most of the city’s pollution is from the city
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itself and not from surrounding areas. Using Indianapolis was also simply practical for Gurney and his team. “I was at Purdue at the time [of the research]. Indianapolis being physically proximal was helpful,” Gurney explained. By being so close to the team, Gurney could take regular trips to Indianapolis and talk with the city’s environmental staff. In addition, Indianapolis has an ideal terrain, which increases the accuracies of Hestia’s readings.
Planes, cars and coal As expected, Indianapolis’ major roads are the largest source of automobile carbon emissions. While the city’s major roads, interstates and highways make up just 15 percent of Indianapolis’ roadways, they are responsible for 62 percent of the city’s roadway carbon emissions. Moderately busy roads, which account for about 10 percent of Indianapolis’ roads, are responsible for approximately 22 percent of the city’s vehicular carbon emissions. The remaining 75 percent of Indianapolis’ roads, which are used lightly, account for the rest of the city’s roadway carbon emissions. Carbon emissions from roadways are highest during the morning and early evening rush hours. According to Hestia, the Harding Street Power Station, a coal power plant on the Near Southside, and Indianapolis International Airport are the largest individual sources of anthropogenic carbon emissions in the city. Both of these emitters are located in Decatur Township, which, coincidentally, emits more anthropogenic carbon than any other Marion County township. Gurney found Hestia’s results for the Harding Street Power Station particularly interesting. When asked if the power plant’s carbon footprint was surprising, Gurney responded, “I would say they were what we
expected. The power plant within the city limits is distinct, large and very noticeable. It is not necessarily surprising, but it is still alarming.” His results reflect general findings from the Harding Street Power Station. Data from the Commission for Environmental Cooperation, an early 2000 study, says the power plant released more than 3.6 million pounds of carbon dioxide per year. Still, city officials say they should not just focus on the largest emitters in the city. “While some sources are highlighted as larger emitting facilities, it is important to not lose sight of an important educational message from this project. Everyone can play a part in reducing emissions associated with energy and transportation,” explained Matt Mosier of the Indianapolis Office of Sustainability. While smaller emitters may not output as much carbon dioxide as the Harding Street Power Station and Indianapolis International Airport, together they release a substantial amount of air pollution. Elsewhere, Hestia found that the majority of carbon emissions from residential properties are emitted during the evening hours. The majority of carbon emissions from businesses, on the other hand, are emitted during the day. Seasonally, homes and businesses have a higher carbon footprint during the winter months, due to increased energy usage for heating.
Expansion of Hestia Gurney and his team have big plans for Hestia’s future. They plan to implement methane in their model, considering it is the second most abundant greenhouse gas in cities. They also want to expand Hestia’s reach. Gurney said a lot of cities including Los Angeles and Phoenix have already expressed interest in implementing Hestia. Still, Gurney and his team want to do more with Indianapolis. Other research groups have already taken note of Hestia and recognize what it may bring to carbon mapping. “This is a visually compelling view of carbon emissions, identified down to the individual building level,” explained Gabriel Filippelli, a professor and biogeochemist at IUPUI. “Given that no limits currently exist for carbon emissions, this model does a better job at present in developing public awareness of greenhouse footprints than in developing definitive policy actions.” In the future, Gurney could see Hestia being used as a policy tool in cities like Indianapolis. Before that can happen, however, the Hestia team wants to make their product more user friendly so that city officials can use it with ease on a day-to-day basis. City officials, such as Mosier, could see Hestia fitting nicely into their already dedicated environmental policy making. “[Already] the City has proactively led by example with aggressive energy efficiency improvement at city-county buildings, city operations and in promoting alternatives to residents and businesses,” Mosier said. “The Hestia project is an easy to understand simulation of carbon dioxide emissions from the Indianapolis community.”
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