Part 3 – Lifecycle Analysis
One of my favorite projects in grad school was comparing two products using a lifecycle analysis (LCA) tool to assess the resource and energy inputs and equivalent waste and pollution outputs. My team decided to analyze the component parts, production energy, and transportation required to create one 12oz Starbucks paper cup and one 12oz Starbucks plastic travel mug. Reusable plastic mugs are more durable but more resource intensive, so since everyone we knew was buying them (and had kitchen cabinets full of them), we wanted to see how many times you’d have to use a reusable mug instead of a paper cup to make it worth the extra resources and energy to actually become the “environmentally friendly” option.
The primary benefit and drawback of running an LCA is that the results are completely determined by what information you include. Unfortunately, we chose to use a major brand name product in our comparison, and the company was unwilling to share any useful information about how the items were produced. We made some educated guesses about the types of materials used but knew nothing about the amount of energy necessary for the production process. Some internet research helped us learn that the plastic mugs were made in China and the paper cups were made in a factory in (if I remember correctly) North Carolina.
The best we could do for our analysis was to look at the weight of the various types of plastic used in the reusable mug and the various types of paper, cardboard, and plastic used in the single-use cup, and then calculate the transportation footprint of each on their way from each factory to our campus Starbucks. It was certainly not a comprehensive picture of which is “better,” but it was a great exercise in identifying and considering the different process inputs and making a decision based on available information. Although the report wasn’t as comprehensive as we had hoped, we still got an A.
My project team concluded that (given the transportation footprint alone) you would have to use the travel mug in place of a paper cup 665 times to make it worth the purchase.
10 years later, it looks a little worse for wear, but I think I’ve more than cleared the threshold.
Considering Implicit Bias
My point in telling that story is to illustrate that running an LCA on a product can provide detailed information about energy and resource inputs, as well as waste outputs, for a cradle-to-grave examination of a product’s lifecycle. A lifecycle analysis, however, is only as good as the reliability and availability of information plugged into the system, meaning the results can vary wildly based on assumptions that are made throughout the process. If you make a decision based on a lifecycle analysis from anyone (even/especially me!), make sure you understand what data was used and what assumptions were made in the process.
During Christmas week when I was finally diving back into this rabbit hole of roofing information, I found an article about building cladding materials that talked about the biases inherent in LCAs run by different industries. For example: Vinyl Siding Institute’s LCA “proves” vinyl siding is the environmentally responsible siding choice, Western Red Cedar Lumber Association shows cedar outperforming the other materials studied, National Brick Research Center claims brick is the best option, and Natural Stone Council describes granite cladding outperforming brick, limestone, aluminum, and precast concrete.[1]
Ironically, this well-written and balanced article from BuildingGreen was quoted out of context in an incredibly biased and unsupported metal roof “study” (which was sponsored by the Metal Construction Association) as an example of why non-biased LCA studies are so important… and also why metal is by far the best option for building cladding.[2] Anyone taking the time to follow the link would see that Building Green’s assessment of metal cladding is a little more measured. They first point out that there are many considerations when evaluating different materials for construction projects, listing these basic questions:
- How is it manufactured?
- What is the energy required to manufacture it?
- What is the energy required to transport it?
- Can it be maintained, repaired, and dismantled easily?
- What happens at the end of its service life?
BuildingGreen, which appears to be fairly even-handed and has a lot more time, resources, and information on the subject than I do, summarized the pros and cons of metal in the following verdict: “Metal cladding has a lot going for it: it’s lightweight, low maintenance, and lasts a long time. That’s enough to make it a strong choice in many applications, but don’t overlook the substantial manufacutring impacts, and think twice about it when close to sensitive welands and when onsite stormwater management is weak.”
Content source: [3]
Considering Biological Impacts
I was surprised to hear about runoff considerations of metal and other roofing materials, as I’ve always perceived asphalt to be the real offender in this area. Anyone who has ever purchased a new asphalt roof knows that you have to clean grit out of your gutters for a while, especially right after installation. I have even heard recommendations about disconnecting your rain barrel for the first year after getting a new asphalt roof.
However, other roofing systems seem to have their own problems. Several studies have shown elevated levels of zinc, which is harmful to waterways and aquatic ecosystems, in runoff from uncoated, galvanized steel roofs.[4], [5] Wooden roofing materials have high levels of copper (also toxic) in the runoff.[6] One study showed an increased level of arsenic from a green roof installation.[7]
We know asphalt roofs shed a lot of the rock granules, creating visibile waste from the roofing material. Additionally, if the shingles are coated with any compounds designed to increase resistance to algae or moss, those materials will slowly be washed into waterways as well, impacting the aquatic ecosystem. One of the studies mentioned above determined that the highest quality rainwater runoff came from metal and concrete tile.[8] However, in receiving a quote from a metal roofing contractor, we learned that most metal shingles are coated in fluoropolymers for protection against the elements, and that piece of information right there was enough to end the discussion as far as my husband was concerned.
Fluoropolymers are a group of perfluoroalkyl / polyfluoroalkyl substances, also known as PFAS. I wrote a four-part series on them after they came to mainstream attention through the documentary “The Devil We Know” and major motion picture “Dark Waters.”[9] In short, they were developed to make consumer products more durable, but they themselves are carcinogenic and do not break down in nature or in our bodies; they are present in virtually every living creature on the planet. While we ourselves would not be coming into contact with the shingles on our roof, we did not want any of it washed into local waterways over the course of the next five decades, nor did we want to contribute to the demand – and therefore production – of more PFAS if we could avoid it.
Image credit: [10]
Asphalt shingles, while they do contain zinc, hydrocarbons, and compounds to prevent moss and algae, appeared less concerning than I expected, based on the runoff studies I reviewed. It seemed that the biggest concern related to runoff with respect to asphalt shingles was the actual pieces of rock or aggregate detaching from the fiberglass backing and collecting in the gutters. The result here is higher levels of dissolved organic carbon in rainwater runoff, but not zinc, copper, arsenic, or PFAS. The place health concerns may come into play for asphalt shingles is during the manufacturing and (possibly) recycling stages.
Considering Recycling Options
The optics around asphalt shingles in an increasingly environmentally conscious world are not great. Asphalt is a petroleum product, tying it to an industry that is often seen as dirty, outdated, and harmful. Meanwhile, metal is often touted as a much more environmentally friendly option, as it is recyclable. Please note: I have made mention on this blog before (first post, in fact [11]) about the difference between if something is recyclable and if it is recycled. For example, if you still live in a municipality that accepts any type of plastic in your curbside pickup, rest assured that it is not all being recycled. Even though the packaging may say it can be recycled, if it is not cost effective to recycle it, it goes to the landfill. The same is true for asphalt shingles.
Eleven million tons of asphalt shingles go to the landfill every year in the US, despite the fact that recycling one ton of shingles can replace the equivalent two barrels of oil. (We will have around two tons of shingles coming off of our roof soon.) Hot Mix Asphalt (HMA), typically used for paving roads, generally uses up to about 5% recycled asphalt shingles. However, only nine states currently allow use of recycled shingle mix in private roads, parking lots, and for patch work.[12]
The primary health concerns I was able to find related to asphalt was in the emission of polycyclic aromatic hydrocarbons (PAHs) during the production of HMA, less so in the production or recycling of asphalt shingles. PAHs are produced through the incomplete burning of organic substances, and some are carcinogenic. It appears that the risk comes from the heating of organic materials in production of HMA, which releases PAHs into the air; they are not expected to leach from shingles or roads into waterways.[13]
Unfortunately, very few options are available for recycling asphalt shingles, and we will pick up there next week, in the last post of this series when I will do my best to summarize the various factors that played into our final decision.
~
Have you ever run a Life Cycle Analysis? What were the sticking points you encountered? What surprised you? I’d love to hear about it below.
Thanks for reading!
[1] https://www.buildinggreen.com/feature/cladding-more-just-pretty-fa-ade
[2] https://continuingeducation.bnpmedia.com/article_print.php?C=1913&L=563
[3] https://www.buildinggreen.com/feature/cladding-more-just-pretty-fa-ade
[4] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5086751/#B36-ijerph-13-01012
[5] http://www.harvesth2o.com/RWH_good_bad_ugly.shtml
[6] http://www.harvesth2o.com/RWH_good_bad_ugly.shtml
[7] https://www.sciencedirect.com/science/article/abs/pii/S0043135410008535?via%3Dihub
[8] https://www.engr.utexas.edu/news/archive/6853-rainwaterharvesting1
[9] https://radicalmoderate.online/the-devil-we-know-and-dark-waters-teflon-in-the-media-part-1/
[10] http://www.harvesth2o.com/RWH_good_bad_ugly.shtml
[11] https://radicalmoderate.online/new-recycling-guidelines-in-the-south-hills/
[12] https://www.forconstructionpros.com/asphalt/plants/article/10292429/quick-facts-about-asphalt-shingle-recycling-and-the-environment
[13] https://www.wisconsin.edu/waste-research/download/2013_student_reports/13%20MSN%20Chen%20RAS%20leaching.pdf
2 Comments
Will Carpenter · January 25, 2021 at 12:10 pm
Have you considered slate roof shingles? High upfront cost, but if locally sourced and with modern installation techniques, the LCA must be exceptional.
Alison · January 25, 2021 at 1:16 pm
Hi Will,
I would love slate, but unfortunately our roof isn’t steep enough. Also (more aesthetically) it would probably clash with our mid-century brick split-level.
If we lived in a Tudor, for example, I would have demanded we go with slate 🙂