A Review of Existing Carbon Calculators

In week one of the project, I investigated several existing online tools to estimate carbon footprints. These “carbon calculators” essentially measure your impact on the environment in terms of carbon dioxide emissions (typically in mass of CO2 equivalents produced per year). Generally, these tools target average people living in houses or apartments, as they use consumption rates from utility bills to calculate footprints associated with electricity, natural gas, and water usage. Thus, none of these calculators are appropriate for use by college students, since we don’t receive utility bills.

To investigate existing carbon calculators, I used a common set of assumptions in each calculator to estimate my carbon footprint for life after graduation, when I will be living and working in Houston. The results are listed below:

The results, detailed in the table below, vary widely – ranging from 10,500 lb CO2/year to 56,700 lbs CO2/year. From the seven calculators, my average carbon footprint was 24,960 lb CO2/year, with a standard deviation of 16,400 lb CO2/year. Clearly, these results are not in close agreement, to say the least, and a variety of factors could have led to this wide range:

  1. Each calculator considered a slightly different set of carbon sources. At minimum, each incorporated transportation and energy used in the home for heating and electricity. In fact, these are the only factors incorporated in the Warwick University calculator, which may explain why it is the lowest estimate. All of the other calculators considered at least one additional factor, and these varied between calculators, including shopping, education, public transportation, food, etc. The highest footprint (56,700 lbs CO2/year via Oroeco) encompassed the largest number of carbon sources.
  2. Online calculators seem to be designed primarily for maximum generality and ease of use, which makes sense, since the average American is not an expert in life cycle analysis and carbon footprinting. However, it was sometime difficult to gauge how to input specific quantities to obtain accurate results. For example, several of the calculators asked for the number of people in the household, presumably to properly apportion carbon impacts from heating, cooling, and electricity use in the home. However, it was unclear if the miles traveled by each reported vehicle were similarly divided among the members of the household. In my case, I plan to share an apartment with a roommate – thus splitting home energy costs – but have my own car, so it was tricky (and unclear) how to ensure it was correct. I eventually decided to say there were two people in my household, and then input two identical vehicles (with the same miles traveled per year and mpg).
  3. Following a trend in the other carbon analyses I have seen over the years (a trend that has become somewhat of a pet peeve), results given in “tons” generally do not specify if these are English tons (2000 lb/ton) or metric tons (2200 lb/ton). Using the wrong conversion from tons to pounds could introduce a relatively significant amount of error into the footprint. For example, for the “26 ton” Nature Conservancy footprint, the difference between English and metric tons represents about 10% of the footprint calculated with English tons. In general, I used English tons for calculators developed in the United States, and metric tons for calculators developed in Europe.

Of the seven, my favorite calculator was by far Oroeco. Not only does it consider the most comprehensive set of carbon sources, it also integrates with mint.com (a finance-tracking service) which theoretically gives a more detailed, accurate carbon footprint while simplifying the process for the user. It also integrates with Facebook, allowing you to compare carbon footprints with your friends and community. This adds social and competitive aspects to the numerical value, which I believe makes the results more meaningful and gives a larger incentive to reduce your footprint.

As I mentioned earlier, none of these calculators relevant to my current living situation, as I live on the Rice campus and do not have access to utility bills. However, in my research, I did find documentation for one carbon calculator geared towards college students: CarbonTerp. This tool was developed in 2008 specifically for students living in dorms at the University of Maryland. The student answers questions about electricity usage (for example, what electronics do you use and for about how long); the calculator uses the responses and generalized data for the student’s specific dorm to estimate a carbon footprint. Much like Oroeco, the tool also has the ability to compare carbon footprints between students. However, while there is full documentation for the tool online, the tool itself is not publicly available (as far as I could find). Even if it were, it is specific to the Maryland campus, and its results would not be accurate for Houston (since it is different buildings and climates). Thus, I was not able to use this tool to estimate my own footprint, though it would serve as a good example or template for future tools oriented towards college students.

Since I was unable to find a carbon calculator applicable in a Houston dorm setting, and given the large variance in seemingly over-simplified online calculator tools, my next step in this project will be to start calculations for my own carbon footprint.

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