A 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 degrees Fahrenheit, a temperature well below
the 59 degrees Fahrenheit 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 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
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
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 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
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
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
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
Elsewhere, Hestia found that the majority of carbon
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
"[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."