My law firm has established a green committee to study ways that the firm can become more green. The first measure that I’ve noticed is the abolition of styrofoam (Since Dow owns the tradmark for styrofoam I should call this expanded polystyrene foam) cups. This is a common “first strike” in company efforts to reduce greenhouse gas impacts, partly because it is so visible and partly because the waste involved in using a cup only once is so obvious. However, the actual impact reduction needs to be kept in perspective. There are other things that can be done to make a bigger impact. In fact, space heaters will release fifty times the amount of greenhouse gas (actually CO2 equivalents) as cutting back on styrofoam cups.
As an example, a single 1,500 watt space heater uses as much as 5,100 BTUs per hour. During a nine-hour work day, that space heater will generate 45,900 BTUs. In Iowa we use coal to provide electricity. Coal-based electricity generates 2 pounds of greenhouse gases per hour per killowatt. So, a single 1,500 watt space heater will generate 3 pounds of greenhouse gases (“GHG”) per hour, or 27 lbs per nine-hour day. Fifty 1,500 watt space heaters running for nine hours per day generate 1,300 lbs of GHGs per day. For a four month winter period, these same space heaters will generate 183,720 lbs of GHG. That is 91 tons.
Those styrofoam cups? Assuming that our law firm goes through 50 per day, that is 13,000 cups per year, or 8.060MBTU per year at 620 BTUs per cup. I could not find any source to convert BTU to GHG, but if we extrapolate the BTU ratio between cups and space heaters to get GHG emissions then we can develop rough approximation, assuming that the cup manufacturer uses coal to get its power. Assuming that 1,500 watt space heaters generate 3 lbs of GHG per hour and that they generate 5,100 BTU per hour, we get a ratio of .0005882 lbs of GHG per BTU. So, a single cup generates one third of a lb. of GHG, or .3646 lb. 13,000 cups generate 4,740 lbs of GHG, or a bit over two tons. This works out to 2.5% of the GHG production of the space heaters.
What about driving a fuel-efficent car verses driving an SUV? There is general agreement that each gallon of gasoline releases about 20 lbs of GHGs. So, a difference of 10 mpg between an SUV getting 20 mpg and a car getting 30 mpg for a 10,000 miles per year will save 167 gallons of gasoline. That works out to 3,340 lbs of GHG reductions per year. Note that the math does not generate the same ratio of savings as the two cars move up the mpg ladder. A difference of 10 mpg between a car that gets 40 mpg and a car that gets 30 mpg is only 83 gallons of gasoline. So, fifty employees driving more fuel-efficient cars instead of SUVs would save 167,000 lbs of GHG emissions per year.
What about switching from an SUV getting an average of 15 mpg to a Honda getting 40 mpg for a sixty mile round-trip commute? That works out to 260 days x 60 miles = 15,600 miles. Divided by 15 mpg we get 1,040 gallons. Divided by 40 mpg we get 390 gallons. The difference is 650 gallons. This works out to 13,000 lbs of GHG emissions.
Assumptions:
10,000 EPS 16 oz. hot cups generate 6.2 MBTU. This is 620 BTUs per cup.
The ratio of watts to BTU is 3.4. Therefore a 1,500 watt space heater generates 5,100 BTU per hour.
Assuming that the cup manufacturer uses sources that are equivalent to coal, the relative ratios of cups and space heaters can be estimated for GHG emissions.
Coal-sourced electricity generates 900 grams of GHG per KWh. There are 454 grams per pound. So, this is about 2 lbs per KWh.
Souces:
Iowa Environmental Compliance 