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We chose to use the Clean Air-Cool Planet calculator because it not only is used by many other colleges and universities, which enables us to compare our greenhouse gas emissions to other similar institutions but we have also used this calculator for past greenhouse gas reports, which means that we will be able to more accurately compare the changes in our greenhouse gas emissions from year to year.

Clean Air-Cool Planet GHG emissions calculator default coefficients

Fossil fuel usage in campus houses and electricity data were obtained from the invoices of our energy provider, XCel energy. Natural gas usage on the main campus was obtained from the Steam Plant (which accounts for almost all of the natural gas used on the main campus) production log, obtained from the Facilities department.

Fuel usage for campus vehicles was obtained from Campus Services (for the campus fleet data) and the Facilities department (for the Facilities fleet).

Commuting mileage for faculty and staff was calculated by Carleton's database administrator using zip codes of faculty and staff residence from our data warehouse and using the longitudinal and latitudinal distances from those zip codes to Carleton's location to get a rough estimate of total commuting distance for faculty and staff. This average distance per person was then calculated based upon number of faculty and staff.

Air travel data was obtained from the Off Campus Studies department and the business office. For the latter, data was only available for departure and arrival cities but total mileage had not been calculated. A computer science student at Carleton wrote a computer program to calculate the mileage for each flight (using an online flight mileage calculator).

Data from Carleton's waste hauler, Dick's Sanitation, was only available for October and November 2010. This data was averaged and applied to the entire year.


Data on fertilizer was obtained from one of the Student Farm interns.

Sequestration data for our Arboretum was obtained from a Carleton ecosystems ecology class (see below for details).

For further details, see the inventory narrative below.

Paper usage was classified as di minimis and emissions from paper were not included. From rough estimates of our paper usage, it seemed that paper made very little difference on our overall emissions. Additionally, we were not able to get data on the number of pounds of paper that Carleton consumes every year as only monetary values were recorded and pounds of paper could not be obtained. Additionally, there was no data available on the recycled percentage for each type of paper that we used. Therefore, considering the very small effect that paper usage has on greenhouse gas emissions overall, we decided not to include it as the data that we could have provided would have, at best, been very simplified estimations

Refrigerants and chemicals were also classified as di minimis as very little refrigerants and chemicals leak out of the system. In addition, those that do leak would be very hard to quantify so we decided to not include any data related to refrigerants and chemicals in our greenhouse gas inventory.

Finally, waste water was classified as di minimis as it was very hard to get data on how much and what type of waste water Carleton produces from the City of Northfield invoices that we had. Because waste water would not contribute to our total greenhouse gas inventory significantly, we decided that the effort in figuring out how much waste water Carleton produces on an annual basis would not be worth its small effect on Carleton's greenhouse gas emissions.

The biggest data limitation that was encountered was with commuting, as there is no database that records actual commuting information. Therefore, in order to calculate commuting mileage as described above, several assumptions about the commuting habits of faculty and staff (it was assumed that all students walk as all live on or near campus) had to be made. These included 1) Every faculty and staff member drives personal vehicles to school and no one carpools; 2) The longitudinal and latitudinal position of the zip code for each town marks the actual location of residence; 3) The drive from this zip code to Carleton is a straight line; 4) No staff took vacations or holidays (assumed worked every day of the year except for weekends) and no faculty member commuted to Carleton more than the number of days that classes were in session per year (30 weeks of classes and weekends were not included). Clearly, some of these assumptions are incorrect but it was felt that some balanced each other out and that this was the best that could be done given our limited data.

The solid waste data was also limited given that the only waste reports from October and November 2010 were available. Therefore, it was assumed that the solid waste on campus does not vary greatly from month to month, so the data from October and November was averaged and multiplied by 12 to get yearly solid waste data.

In addition, we only had fertilizer data from 2008 but we assumed that the amount applied would be similar in 2009 as the fields have not changed since 2008.

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A Carleton ecosystems ecology class calculated the number of metric tons of carbon that is stored in the Carleton College Cowling Arboretum, which is approximately 775 acres, in one year. Using data on the types of plants growing in the Arboretum along with their extent, they estimated that the Arboretum stores 653 additional metric tons of carbon dioxide per year.

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