 Hi, my name is Aristide from Metabolism of Cities and in this video, we will explain why it is so difficult to measure circularity in cities. First of all, if you want to measure something, you have to define something. And in cities, it's something that is either lacking or still very new. Circular economy has been defined in many different ways. There was a paper back in the day that collected 114 definitions for circular economy. And at the end, the author proposed another one on top of all of them. In the case of cities, I guess this is still new because the interest was more placed at a higher economical level or scale. Let's say economies, national economies, global economies, sometimes companies. So there was this micro, the macro, but not the mezzo where the cities were lying. Anyway, some definitions of cities exist. For instance, the EMF talks about designing outways from cities. Others say that, for instance, the circular economy in cities is actually a means to an end rather than an end in itself. So circular economy in cities would mean that you use circular economy to achieve some of your own objectives, but which are not material per se. And some others explain circular economy as or say that circular cities is a city that includes circular economy principles in all of their activities. Now, all of this is great, but it doesn't really help us measure it, right? Because you cannot really measure how much a city designs outwastes or how much a city achieves its goals with circular economy and not achieving circular economy in itself. So in this video, I'll try to explain why it is so difficult to define it and why it's so difficult to actually measure it. First of all, there is a matter of scale. At which scale do we measure things? In material flow assessments and in assessments in general of carbon or of materials, we tend to have two different types of approaches. The territorial-based approach and the consumption-based approach. The territorial-based approach is the one that says, look, you have a city, you have a system, you draw a boundary around it and you just measure what comes in, what goes out, what's consumed locally. The good thing with it is that normally you can get accurate data and it's something that you can see with your own eyes, right? So you can, I don't know, you can go to the meter of water or the meter of electricity and see how much was consumed. With materials it's a bit more difficult, but still you can see how many trucks arrive to your city or through the ports or through railways. But this is great and this is accurate, but it hides a number of things. Today in a globalized economy, most of our flows come through elsewhere, but there are many steps in these supply chains, meaning that let's say a phone is designed, so Apple says, designed in California but then produced in probably China, but then the materials come from elsewhere in the world. So there is a number of points and segments in these supply chains, a lot of transportation and a lot of materials that are discarded within extraction or within the manufacturing process, a lot of pollution as well during the logistics etc etc. So it means that contrary to the territorial-based approach where you just measure what comes in, the consumption-based approach takes into account all of the supply chain. So really all of the activities that went into making the product. You just don't consume the product, you consume also all of its environmental impact. And this is called the consumption-based approach. So you can imagine that if you want to measure circularity, you can measure it with these two different approaches. One, the territorial-based approach will say that you have X amount of materials that you try to circularize. The consumption-based approach, because you take the entire supply chain, well you'll have, I don't know, three, four, five times more materials that you need to make it more circular. This brings in another topic as well, which is, for instance, we measured about how big these flows entering your city is or their environmental impacts, or sorry, their indirect resource use and indirect waste generation. But this also eludes to the fact that you can become circular at different spatial scales. So you can become circular, let's imagine you have a recycling plant within your own city. You try to circularize the flows within your own city and become self-sufficient, let's say, in these terms. Or you could say, well you collect all of the waste within your city, but then you bring it to another recycling plant in another place. And in both cases, theoretically, you are circular, but in one case you're very close to your city, in another case you're more far away. And you have to think of it as always a compromise between how much does it cost you, how much you need of a critical mass in order to create this infrastructure. So, you know, for plastics, when we banned, well, when China banned plastics, we realized that Europe is not really able to face this plastic ban because we don't have any infrastructure locally. So we have to become more circular on plastics within Europe, not anymore at the entire scale of the world. And this also brings to the fact that there are some materials that we cannot be self-sufficient. So let's say we want to be 100% circular, well, within a city, let's say directly that this is impossible, but let's imagine that we could grow our own food. Well, we probably don't have most of the ores that we need in order for us to produce all of the electronics. So it means that there are some parts that can be circular locally and other parts that we need the entire world to become circular. So this is one huge topic around why it's so difficult to measure circularity at the city scale. It's the scale perspective and which scope do you use? You know, in greenhouse gas emissions, we talk about scope 1, 2, 3. Do you use a scope 1 for circularity assessment or do you use a scope 3 for circularity assessment? But these are just what accounting technique you will use. There are some other facets to it because a lot of people say that circular economy is supposed to be an economy that creates jobs around environmental challenges. So we translate an environmental challenge into economic opportunity. Well, if we don't have economic values for these flows, we have no idea whether circulating these flows will create more jobs or whether these jobs are actually making the economy more circular We think that some jobs are more circular, repairing, recycling, etc. But who knows, there's not a direct causation between these two things. Another element is of course the environmental impacts of these flows. Making a city more circular does not necessarily mean making a city more sustainable or more environmental friendly or reducing all of its footprints. This is still to be demonstrated, if you will, or to be tested. So, recycling some flows, let's take steel for instance, consumes a lot of energy, a lot of water, a lot of resources. So, recycling it and keeping it in the loop might actually be more burdening to the environment than using, for instance, renewable materials such as wood. Or let's say we use a lot of wood because I just said it's better than steel, but using wood might take off wood that captures carbon. So what I'm saying with this is that in general when we talk about circular economy we're thinking about materials. But we have to think about all of the other aspects of these materials. So water footprinting as well, energy footprinting as well, carbon footprinting as well and other life cycle assessment points such as, you know, eutrophication, etc. So this is also one of the reasons why it's so difficult to measure things. It's how do you link environmental impacts with circularity assessment. And perhaps just the last point is a time frame. So when do you consider being circular? Because some products, let's say a building is built now but then you have 40 or 100 years' lifespan and perhaps the materials will be discarded later. So you have a number of elements that are within your stock and will be released as future waste or future resources depending on how you manage them. And therefore how do we consider circularity over time? You know, being circular today because the flows and the infrastructures are like that does not mean it will be the same thing in the future. So you see here that there are many layers of measuring circularity and in order to go ahead we kind of need to define properly a circular city what does it mean and define methods that we all agree and can be behind it. This has already happened with greenhouse gas emissions. We might as well start doing this for materials. We have done it through Eurostat for instance has done this for economy-wide material flow analysis. It would be nice that we start translating this into circularity in order to sometimes burst some bubbles or reinforce monitoring or help develop new policies. That's it for now. Let me know what you think about all of this in the comments and see you in the next video. Cheers!