What are the upfront carbon emissions of a cookie?

I learned a lot from my students this year, both about upfront carbon and about teaching.

My upcoming book, The Story of Upfront Carbon (New Society Publishers, May 2024), is all about the embodied carbon (or upfront carbon, as I prefer) in everything, from your food to your phone. Architects and engineers may understand the concept- although it seems that many don’t care- but carbon dioxide and its equivalents are emitted whenever anything is made, not just buildings. It comes from the materials, the manufacture, and the transportation, and it can be big; in an iPhone, 83% of its full lifecycle emissions happen before you take it out of the box.

To demonstrate the upfront carbon in everything, I asked my sustainable design students at Toronto Metropolitan University to pick an object and figure out the emissions from “cradle to gate”- from the mining or growing of the materials to its distribution point. In buildings, upfront carbon often includes delivery to the site and assembly or installation, but with Amy’s sweater, for example, the drive home from the Uniqlo store in the mall can emit more carbon than the sweater itself. They were asked to produce an “infographic” demonstration of their findings, a three-minute video presentation, and to provide references and documentation of their calculations. The results were sometimes surprising, sometimes hilarious, and often maddening.

I learned a lot about my students and about my teaching skills in this exercise. I leave my students a lot of room to figure out how they want to do an assignment, but in the first class, I showed them how to do a simple analysis and pointed them to a really well-done how-to manual from Allbirds (alas, no longer online), a shoe company promoting sustainability in the industry.

What I got was a whole lot of submissions about food, with percentages for agriculture, manufacturing and transport. It turns out that a website called Carboncloud lists carbon emissions of food products in percentages without giving insight into where the product comes from and where the cradle or the gate is. But hey, here was everything they thought they needed in one place, so they did food.

No more than half a dozen students actually did the calculations in the manner I requested in the first class and in the clarification I issued a few weeks later. Given that only about a third of them were at the first class, I had to ask myself, do I penalize them for not following the format, or do I look in the mirror and wonder if I laid out the problem clearly and gave proper instructions?

I didn’t say, “No Carboncloud! I don’t like the way it presents the information!” And I clearly wasn’t explicit enough about how I wanted it done. So I get these lovely graphic representations of potato chips and cookies and mangos and hamburgers, and my students and I have no idea where anything comes from and how it got here.

And guacamole. At least when I next write about the carbon footprint of food, I will have great sources and graphics.

Students were asked to do video presentations because I like to be able to share their work with a larger audience. Some just filmed themselves talking over the infographic, and some, like Esther’s cookie show, are epic. But enough of cookies and carrot cake and Carboncloud.

There are the students who make everything worthwhile, who do serious investigating and glorious presentations. Jessy presented this traditional Chinese ink stick, after asking me where she could find out the carbon emissions of animal glue and soot. I had no idea, but she figured it out and backed it up with sources.

Elliott spent time with me on the whiteboard, going through his calculations of a nuclear fuel bundle for a CANDU reactor. It’s a different process from making American nuclear fuel, and there is not a lot of information, and the math was serious.

Phillip did this incredibly detailed analysis of a Muji pen, working out the smallest detail.

And then there is Nuray, who calculated the carbon emissions of a Starlink satellite. Pages and pages of backup calculations of building the rocket and the satellite, even the factory, not forgetting that the rockets are recycled. 14.5 tons each, and they are firing up thousands of them, and they barely last three years before they fall back to earth and have to be replaced. Is this the best way to get our internet?

And listen to Mia here, she has a career in media ahead of her, so authoritative and clear.

I learned some valuable lessons from this class. The study of upfront and embodied carbon is so new that many play fast and loose with formats, especially when you get away from building materials and components. I can’t fault my students for finding a resource like Carboncloud and using it.

In such a world where things are not so clear, I have to be a lot more explicit about what I want, with instructions and examples, rather than a few minutes in the first class and a few notes. Looking back, I believe I failed them on this assignment. I won’t make that mistake again if I teach next year.

In the meantime, enjoy an analysis of Diet Coke, where 70% of the carbon is in the packaging, an aluminum can lined with BPA epoxy with Coke pretending that it is recycled in a “closed loop”- the real number is much higher. This is why I love teaching; I learn as much from my students as they do from me.