Hi, in the financial analysis module, we did in week three of the first class. The final assignment looked at whether switching from providing bottled water to giving employees reusable stainless steel water bottles was good financially. We assume that recyclable stainless steel was good and plastic was bad, but we can't just make assumptions like that. We're doing rigorous sustainability thinking, so we need to test our assumptions. In this lecture, we'll do a life cycle assessment to see whether the reusable stainless steel bottle is in fact better than a disposable plastic bottle. To remind you of the situation, a Brita Hydration Station would be purchased and employees would be given reusable stainless steel water bottles. The company would wash the bottles once a week for employees. Over the course of the year, this combination would replace 24,000 half liter, so that's 16.9 fluid ounce, plastic water bottles, 24,000. Here's some data I found out about these bottles. The stainless steel bottles each weigh about 210 grams and each of the plastic bottles weighs 13.3 grams. So the total weight of the materials for an entire year is 52.5 kilograms of stainless steel or 319.2 kilograms, if you use the plastic bottles. The weight of the materials is important, because that's how we'll compute the environmental impact. It's on a per kilogram basis. Now we go to the idea math or Idemat App, that's available for iOS devices like the iPhone or the iPad. It's a single score life cycle analysis tool. I choose open loop recycling. This means some recycling, but not total circular economy. First, we'll look at the bottle grade PET thermoplastic. Here's the Idemat data for PET or PET, the eco-cost is, and these are Euros, 1.51 Euros per kilogram. Later on, we'll change it to dollars. For our 319.2 kilograms, this is a total eco-cost of 482 Euros, or about $520.52 and I'm using an exchange rate of $1.08 per Euro, and we use that rate throughout this lecture. Next, we find the eco-cost for the stainless steel bottle. In Idemat, we go to common metals and we look for stainless steel. Now, there are a couple of choices. I picked stainless steel 316, which is a little more corrosion resistant than the alternative stainless steel of 304. You can see what the app displayed. It says the eco-costs per kilogram of stainless steel is euro 4.85. Again, this is in Euros, because the app and the database that supports it were developed at Delft University in the Netherlands. For our 250 stainless steel bottles, the total eco-cost would be 4.85 euros times 52.5 kilograms, or about 254.63 euros, which at our conversion rate of $1.08 is $274.98, or about $275. Now this is just for the stainless steel, but the stainless steel bottle has a plastic lid and we're washing them every week. So let's look at the lid first. The steel water bottle lid is made of HDPE, so high-density polyethylene and it weighs about 25 grams. So 250 bottle tops, 25 grams, 6.25 kilograms. I got that by multiplying the 25 grams times 250, then dividing the resulting 6,250 grams by 1,000 to get kilograms. The eco-cost of HDPE, this high-density polyethylene, is $1.36 per kilogram. So it added 8.5 euros to the total eco-cost of the bottles. Now we have to wash the bottles and that takes, and I just did this rough estimate. So 750 gallons of water for the number of dishwasher cycles required to wash every bottle once a week. The water has to be heated to about 120 or 130 degrees Fahrenheit. I found this great website, http://waterheatertimer.org, and then it's /Kwh-temp.html [COUGH] and it calculates the electricity required to heat water. Using that website's formula, heating 750 gallons of water from 50 degrees Fahrenheit to 125 degrees Fahrenheit requires 137.5 kilowatt hours, then there's the electricity to run the dishwasher. If each cycle is an hour long to sanitize the bottles and the dishwasher is 1,800 watts, that'll use 270 kilowatts to do 150 one hour-long cycles. So that's 1,800 watts divided by 1,000 watts per kilowatt times 150 hours and so on. So, the total electricity used is 407.5 kilowatt hours. Here is the Idemat screenshot for electricity. The eco-cost is $2.71 per 100 megajoules. Now things get a little bit tricky, because the cost is in 100 megajoules and it's based on a European electricity generation model. I'm going to have to modify the eco-cost for my location and I'm going to do it in Colorado. In Colorado, we have something called a renewable portfolio standard, so about 20% of our electricity comes from renewable sources, mostly wind, and the rest is from coal and natural gas. There are a couple ways we can customize the electricity eco-cost. We could find the CO2 emissions per kilowatt generated in Colorado and adjust that part of the eco-cost. Or we can use the Idemat detailed spreadsheet data, which is available for download from ecocostvalue.com, and it's going to be posted as a resource in this module. The spreadsheet has emissions for US coal and natural gas generated electricity. Here's that little piece of the spreadsheet. Per megajoule, the total eco-cost for US coal generated electricity is 0.0938 euros. And for natural gas it's 0.0445 euros. Colorado electricity generation is 59% coal, 19% natural gas and the rest is zero emissions, because it's renewable. So we compute our weighted average eco-price or eco-cost. We multiply 59% or 0.59 by the 0.0938 eco-cost to get the coal portion of the eco-cost for electricity, then we multiply 19% or 0.19 by the lower 0.045 eco-cost for natural gas. That gives us that last piece of the puzzle, the natural gas eco-cost. We could have included the renewables, but we'd be multiplying by 0 or something really close to 0 for their eco-cost, so it wouldn't contribute very much. Also, Idemat didn't have eco-cost for US electricity from renewable resources. So you can see that the weighted eco-cost in Euros for US electricity generated in Colorado is about 0.064 Euros per megajoule. So, 0.064 per megajoule. Now, we have to do a couple more conversions. I know this is getting old. 1 megajoule is 0.277 kilowatt hours. So our 407 kilowatt hours is equivalent to 1,467 megajoules. Now finally, after all of these conversions and whatnot, we get an answer. The eco-cost of the electricity is about 1,467 times 0.064, which is 93.97 euros. That was long deal. And again, I'm using this conversion rate of $1.08 per euro and that gives us in dollars an eco-cost of $101.49, and this is for the stainless steel bottle on top of the lids and the stainless steel. So we add up all the eco-costs of the stainless steel, [COUGH] the plastic lid, the electricity for washing the bottles, and we get a total eco-cost for 250 bottles for a year as euro 357 or about $385.68. Here are those amounts in dollars as well as the eco-cost of the PET plastic bottles. Now, there's a bit of rounding that caused me to lose a penny on the metal bottles somewhere. I'm not really sure where, but anyway that's just the way it is, but we see the stainless steel bottles are, as we suspected, better than the PET plastic bottles. Now this is a little bit a rough estimate, because I left some stuff out. The plastic bottles have caps made out of a slightly different type of plastic, high-density polyethylene instead of PET, that's that thermoplastic. Couldn't find how much the cap weighed, but the eco-cost per kilogram is close to that of PET. So this emission probably didn't have too large an effect. Did I leave anything else out? Probably. I mean, there's transportation, but that should be more for the bottled water than for the empty metal bottles. So it'd probably make the difference in eco-cost larger rather than smaller, and I can't really think of anything else. We'll have a discussion where you can just suggest things that I might've missed. Now let me quickly review what we did. We had two items that do the same job. They provide drinking water. We did our analysis on the basis of supplying a year's worth of water. We found their basic materials and the weight of those materials on a per bottle basis, then we went to Idemat, which is an iOS app, and we found the eco-cost per kilogram. Then we adjusted that number for the weight of our materials. This gave us [COUGH] the eco-cost for each alternative. Then we looked at the energy needed to wash the stainless steel bottles and found its eco-cost. What we've done is a simple life cycle assessment. It isn't perfect, but the difference between the stainless steel and the plastic bottles is so great that we don't need to be perfect. Stainless steel rules, in this case. In an earlier video, I suggested that doing a life cycle assessment was hard, and it used to be. Now with apps like Idemat, even normal people can do rough life cycle assessments without studying chemical engineering, and that's pretty neat. Thanks for your time.
