Viewpoint: Engineer a sustainable day

Doug Graul and Nick Stowe
Published December 8, 2010

We’ve all heard about carbon footprints, global climate change and the environmental evils of gas-guzzling SUVs. Odds are, however, that what we’ve heard has gained little traction in our lives. Perhaps we recycle more than we used to or skimp a bit more on heating than before. But in the end, we just haven’t seen enough tangible information to motivate change.

What if it was possible to calculate the environmental impact of the average University student in a line item-by-line item analysis of his or her day? While determination of the “average” may be subject to conjecture, the quantitative impacts of specific activities are actually quite simple to calculate. After being empowered with the information presented in the following analysis, what will you do to reduce your daily environmental impact?

Economic Input-Output Life Cycle Assessment (which we refer to as EIO-LCA) is a method that can be used to relate economic data and environmental outputs. As we calculated a student’s average day, we focused on the emissions produced during the use of products rather than considering the complete impact, which also includes manufacturing and disposal. We only counted activities that a student could directly change.

For instance, lighting in a shared computer lab wasn't counted but lighting in a house was. Using Carnegie Mellon University’s EIO-LCA web tool, we calculated the tons of Carbon Dioxide Equivalent Emissions — or CDEE — emitted per unit electrical consumption and distribution. Michigan’s electricity is generated by both nuclear- and carbon-based fuel sources, significantly impacting CDEE per kilowatt-hour. The ratios of these sources were considered and the cost of electricity and natural gas was calculated using a composite of averaged values from typical Detroit Edison Energy utility bills. Seasonal variations in usage were also accounted for.

What does an average day look like? Wake up in the morning, unplug the cell phone from the charger, turn on the coffee pot and make toast and eggs. Use the toilet, take a 10-minute shower and brush your teeth (turning the faucet off while brushing). Power a desktop computer at school, microwave lunch, print a few pages and turn on a desk lamp and an office light. We assumed the average student also plays video games, watches TV, cooks dinner and once each week does laundry. Throughout the day, the student indirectly uses hot water heaters, refrigerators and electronic devices that remain plugged in while not in use. In addition, students use air conditioning in the summer and gas heating in the winter.

What does this average day mean environmentally? The electrical usage of the average student results in almost 7 tons of CDEE emitted over one year while the water usage produces a scant .05 of a ton of CDEE per year. If students drive the typical 15,000 miles a year in a car that gets 24 miles per gallon, they also produce 5.6 tons of CDEE for a conservative composite annual total of 12.6 tons CDEE pollutants.

Let’s define a more sustainable student. Sustainability Sally takes the bus and rides her bike. She uses 15-watt light bulbs, turns off her computer when she’s not using it and opens a window instead of using air conditioning. Lastly, she uses a programmable thermostat in order to minimize the time her furnace is running. By altering her lifestyle, Sally saves enough electricity to power the average American home for four months. The emissions she doesn’t produce allow her to drive a Toyota Prius around the world twice before matching the average student’s CDEE.

If everyone in the world lived like the “average” student, the earth’s temperature would rise by 0.1 degrees Celsius each year. A mere four-degree Celsius global temperature increase is expected to have catastrophic effects, according to a 2006 Stern Review on the Economics of Climate Change. If everyone lived like Sally, the temperature increase would be reduced by almost 74 percent.

Let’s be honest. A single student’s projected temperature change impact is 0.00000000001 degrees Celsius per year. That's not much on any scale. But we have seen the impact of collective behavior and it is nontrivial. You have the data. You know what simple changes you can make to your lifestyle. The question remains, what will you change?

Greg Filip is a Naval Architecture and Marine Engineering Ph.D. student. Doug Graul is a Mechanical Engineering and Industrial and Operations Engineering masters student. Nick Stowe is a Naval Architecture and Marine Engineering Ph.D. student.