Notre Dame tracks a number of metrics related to sustainability. These graphs represent the most prominent of those metrics: carbon emissions per gross square foot of building space, recycling rate, and water use per capita.
GSF (Gross Square Foot): Measurement of indoor building space from outside wall to outside wall.
MMbtu (Millions of British Thermal Units): Standard measure of energy output. One BTU is approximately 1,055 Joules. One standard cubic foot of natural gas yields ≈ 1030 BTU.
MTCO2e (Metric Tons of Carbon Dioxide Equivalent): Some greenhouse gases are more potent than others; emissions of gases other than CO2 are translated into CO2 equivalents so that their impacts can be directly compared. One metric ton is equal to 2,205 lbs.