Calculations and Assumptions

We used numbers and statistics from many different sources to calculate the environmental impact of each pledge actions. Here you can see our sources, assumptions and conditions for our calculations, and the numbers we used.

  • 1. I will compost  when eating in  the Dining Halls  and in Stamp,  and bring  other  food waste to  these places to  be  composted.

    Notes: One person  produces an  average of 20 lbs  of food waste per  month (NRDC)
    Assumptions for Calucations: 4 month semester, 4  week month, 7 day  week,  365 day year
    Source: National  Resources  Defense  Council

  • 2. I will use cloth  or other  reusable  bags  when I  go  shopping.

    Notes: 100 billion plastic  bags thrown away  in the US each  year.

    US population in  July 2008:  304059724

    100  billion/population  = 328 bags per  person per year

     1000 bags weigh  13.15 lbs, 328 bags  weigh 4.313 lbs

     savings of 4.312  lbs  per year

      Assumptions for Calucations: 4 month semester, 4  week month, 7 day  week,  365 day year

     Calculations made with  2008 population data  because WSJ article is  from 2008

     Source: Wall Street  Journal 2008, United  States Census,  Data Life Cycle  Assessment  prepared by  Boustead  Consulting &  Associates Ltd  for the  Progressive  Bag  Alliance

  • 3. I will recycle  paper products,  cans, and  bottles.

    Notes: 1 person  generates  4.4 lbs  of MSW  per day

     Nature  Conservancy's  carbon footprint  calculator  estimates that by  recycling all    materials "locally  recyclable" you  can save 0.5 tons  CO2/year

     Calculations for Assumptions: Use MD number of  0.000557075 MTCO2e  per kWh to find carbon  savings. 

     2,204.62262 pounds in  one metric ton.

     4 month semester, 4  week month, 7 day  week,  365 day year

     Source: Environmental  Protection  AgencyThe Nature  Conservancy

  • 4. I will carry a reusable water  bottle.

     Notes: Average of 4  bottles purchased  per person per  week.

     At a recycling rate  of 29%, giving up  plastic bottled  water diverts 2.84  bottles per week  from the waste  stream (147.68  bottles per year).

     12.7 grams per  bottle.

     12.7 g * 147.68  bottles = 1875.54  grams saved per  year --> 4.135  pounds per year

     Calculations for Assumptions: Assumes 4 bottles per  person per week.

     29% recycling rate  (EPA's given number for  PET bottle recycling)

     4 month semester, 4  week month, 7 day  week, 365 day year

     Source: National  Geographic International  Bottled Water  Association Environmental  Protection  Agency

  • 5. I will replace  one regular bulb  with a compact  fluorescent  bulb.

    Notes: Saves  32.85 kWh  per year or 40.34  lbs CO2/year

     Calculations for Assumptions: Use MD number of  0.000557075 MTCO2e  per kWh to find carbon  savings. 

     2,204.62262 pounds in  one metric ton.

     Assumes 2 hours a day  of usage  (energy.gov  number), or 730  hours/year

     Assumes 60 W  incandescent bulb and  15 W CFL

     4 month semester, 4  week month, 7 day  week, 365 day year

     Source: Washington  State  Department of  EcologyUS  Department of  EnergyUS  Department of  Energy

  • 6. I will wash clothes in cold  water.

    Notes: Energy Star  appliance  calculator: 1 wash  per week --> 61  kWh/year. 

     With our  assumption of 1  wash every 2  weeks --> 30.5  kWh/year.

     Washing in cold  water saves 86%  of  energy-->  savings  of 26.23  kWh/year  or  32.21  lbs  CO2/year

     Calculations for Assumptions: Assume Energy Star  washer.

     Assume 1 load laundry  every 2 weeks --> 26  loads/year or 8  loads/semester

     Use MD number of  0.000557075 MTCO2e  per kWh to find carbon  savings.

     2,204.62262 pounds in  one metric ton

     4 month semester, 4  week month, 7 day  week, 365 day year

     Source: US  Department of  EnergySierra Club

  • 7. I will eat vegetarian one day a week.

    Notes: 6 oz protein --> 0.158 kg serving

    27.0 kg CO2 (beef) - 2.0 kg CO2 (veg/tofu)

    Savings: 4.25 kg CO2/day --> 9.37 lbs CO2/day

    9.37*52 = 487.24

    9.37*16 = 149.92

    Calculations for Assumptions: Uses average USDA My Plate recommended protein numbers for adult men and women aged 19-30.  (Men 19-30 recommended serving: 6.5 oz. Women 19-30 recommended serving: 5.5 oz. Avg = 6.0 oz.)

    Assuming students taking the pledge will be within age range of 19-30.

    4 month semester, 4 week month, 7 day week, 365 day year. 19 Mondays in a semester and 52 Mondays in a year.

    Source: Environmental Working GroupUSDA My Plate

  • 8. I will reduce vampire power by unplugging my printer, computer charger, and phone charger when not in use - or by using a power strip.

    Notes: Printers: 12.78 kWh/year

    Computer charger plugged into wall, not charging computer: 39.78 kWh/year

    Computer charger plugged into wall, charging

    Computer in sleep mode: 141.93 kWh/year

    Phone charger plugged in, not charging phone: 2.34 kWh/year

    Total: 196.83 kWh/year = 241.73 lbs CO2/year

    Calculations for Assumptions: kWh based on average numbers for each item as listed on standby.lbl.gov website. 

    Total is sum of all device's standby averages.

    Use MD number of 0.000557075 MTCO2e per kWh to find carbon savings.

    2,204.62262 pounds in one metric ton

    4 month semester, 4 week month, 7 day week, 365 day year

    Source: Lawrence Berkeley National Laboratory, US Department of EnergyEnvironmental Protection Agency

  • 9. I will reduce my showering time by five minutes.

    Notes: Five minute showers use 10-25 gallons of water.

    Reducing your showering time by five minutes is a reduction of 10-25 gallons regardless of total time.

    Savings: 10-25 gallons per shower --> avg to 17.5 gallons Per day

    Calculations for Assumptions: Assumes 1 shower per day

    4 month semester, 4 week month, 7 day week, 365 day year

    Source: Environmental Protection Agency

  • 10. I will turn off the tap while brushing my teeth.

    Notes: 8 gallons per day

    Calculations for Assumptions: Assumes daily teeth brushing.

    4 month semester, 4 week month, 7 day week, 365 day year

    Source: Environmental Protection Agency

  • 11. I will check my faucets, showerheads, and toilets for leaks and call 4-WORK or my landlord when repairs are needed.

    Notes: Faucets (leaking 1 drip per second): 3,000 gallons per year

    Showerheads (leaking 10 drips per minute): 500 gallons per year

    Toilet (running constantly): 200 gallons per day

    Calculations for Assumptions: 4 month semester, 4 week month, 7 day week, 365 day year

    Uses total gallons from faucets, toilets, and showerheads

    Source: Environmental Protection Agency

  • 12. I will walk or bike short distances instead of driving.

    Notes: Walking or biking 5 miles a week instead of driving saves 4.9 lbs of CO2 each week

    Calculations for Assumptions: Use MD number of 0.000557075 MTCO2e per kWh to find carbon savings.  2,204.62262 pounds in one metric ton.

    Speed: 10-11.9 mph AND under 10 mph

    Weight: all weight ranges (144 or less, 145-174, 175 or more)

    Car size: compact and midsize

    4 month semester, 4 week month, 7 day week, 365 day year

    Source: Bike to Work Day

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