 Over the years, you might have seen a number of studies called urban metabolism studies, material flow studies, circularity studies or circular scan studies throughout many academic studies but also produced by consultancy firms. In this video I want to show you how you can do them and what are the five essential steps to carry out one urban metabolism study. Let me just start by showing you what it is that I call an urban metabolism study or a material flow study and then I'll go through the five steps that you need to do. So let's start with the first study which is supposed or is characterized to be as one of the first urban metabolism studies. That was back in 1965 by Abel Wollman and he conducted the study on a hypothetical one million inhabitants US city and as you can see here what it did is to quantify some of the flows entering and exiting one city. Now why do you do this quantification analysis? It's in order to provide keys or insights about how to reduce the environmental impact of that city. Since then, numerous studies have existed and you can see them both in the academic word and in the consultancy word or even in the policy word. So let me just jump to one of the consultancy offices that are doing a lot of material flow analysis studies or circularity scans or urban metabolism studies. Over here you have circle economy from the Netherlands and you see a number of studies that they have carried out for numerous cities. What does it look like? Well, in general it's a report and in the report you will often see these type of diagrams, these Sankey diagrams that I'll explain into a future video what it is and how to do it. But in general you have reports and you have a quantification analysis and these type of diagrams. Their neighbors right next by in Amsterdam is metabolic and they have also done numerous urban metabolism studies or circularity studies for cities. Over here you have for instance Charlotte in the US and you see once again that's a report. You see a number of action points and you see one Sankey diagram here, a quantification of flows. Lastly over here it was a study I did back in the days for the urban metabolism of Brussels. So you see the region of Brussels and you see flows entering and exiting and once again it's a report where we also had a bunch of actions at the very end. So in case you want to learn more about what is an urban metabolism study where they have taken place around the world, we invite you to go to our library website so Metabolism of Cities Library and over here if you click on case studies you will see a map with all of the case studies of urban metabolism studies that exist out there. So if you zoom in for instance in Europe in France you have two of them over here and every time it tells you which one it is, who is the author and once you click on the study it gives you a bit more insights about what it is, where you can find it, what type of flows it has analyzed and where you can get the report. So you see here you can find many many studies depending where you live. Now let me now that I have given you an introduction about what is an urban metabolism study let me just give you the five steps you need to take if you want to carry out one yourself. All right if we go over these five steps that you'll need to carry out these urban metabolism studies or you can call them a material flow analysis study or circular, you know, circularity scan study let's say. These five steps consist of first of all defining the system that you want to analyze so when you do territorial metabolism study or a circular scan study what you do is you first define in space and time what it is you will be looking at. In the case of the previous case, you know, the examples I showed you in the case of Sherlock in the US well it might be the city, it might be the region, it might be the metropolis depending on what you're looking at. It could be also a neighborhood, you know, the spatial scale is up to you to define but you need to define it. Oftentimes you will define your system boundary, your spatial system boundary to where there is more data so it could be at an administrative scale or it could be a statistical scale or something like that. Then you need to define it in time what is the year of reference for which you are analyzing your system. Well, most oftenly it's, you know, the most recent year but it could also be the year for which you have more data so it could be a census year or it could be another year for which you know that most of your data align for because oftentimes you might find some data for one year for the energy flows and for water flows you might not find them and so what you want is ideally one year for which you have all of your data aligned. Then in your system definition you also say what do you count, what do you account, right? Let's say one study could be accounting all of the flows, another one could look just at the end of the system just the waste, the other one could look at let's say just energy flows so it really depends, right? It could be, it's up to you to say which of the flows and the processes are within your accounting exercise and which are without. This can also be let's say you can have a black box so you just look at what enters and what exits but no idea what happens really inside your system or you can have let's say a gray box where you know some of the activities inside but not all of them or you can really have a very detailed and explicit system where you know all of the activities, all of the actors, all of the flows together. So that's the first step, you define what you measure, what's included, what's excluded for what year you're measuring stuff and what is your spatial scale for which you will be accounting for. The second step is the measurement of the flows per se so what does that mean? Well, you need to start looking for data to collect data out there, information, data sets, maps, whatever that is. Sometimes you measure it yourself, sometimes it's secondary data, sometimes it's literature data, sometimes it's estimations. So you need to measure all of the flows for which you have said that you would include in your study, right? In step one. So step one, you say what are all the things that I need to measure? Step two, you start measuring them. Step three is what happens when you have some unknown quantities. So in most of the cases, you will not have all of the data there, right? So you will always have some unknown quantities, unknown flows and all of that. So how do you get there? Well, there are many ways. Either you do it by, let's say, mass conservation equations. So if you look at the method of the Bachini and Brunner that they have, the Material Flow Analysis Handbook, over there you have a number of equations that you can resolve in order to find your unknown quantities. Or you can, let's say, when you don't feel comfortable with this, you can always also downscale information from another spatial scale or estimate it from a smaller scale and then add it up to your scale. So you start doing some estimations and calculations over there. So step two and step three are really together, let's say. The first one, you look for data. The second one is if you don't have data, try to figure out how to, you know, fill the gaps, the data gaps. Then step four is once you have all of your data, you start illustrating your flows. If you remember well, in all of the studies, you had these Sankey diagrams, these illustrations, these diagrams, where we saw the flows entering and exiting, we saw that they had different proportions. These are proportional to the weight of the flows, to the mass of the flows. Or if it's not mass, it could be, you know, energy, kilojoules or kilowatt hours or whatever. So you start illustrating your flows, your stocks and all of that. Then what you do, you start interpreting what you have seen. So interpretation of flows means, well, I can clearly see from my diagram that water is the flow that dwarfs all of the other flows. Or that most of my energy goes to, I'm making this up, to heat homes or to heat buildings. Or that most of my CO2 emissions comes from transportation. So you start interpreting what you're seeing, right? I mean, you go from measuring all of the flows to start interpreting, you know, I have no extraction locally, but I import most of my flows. Therefore, my economy is very import dependent, let's say. So you start interpreting your data and your figure. That's step four. And finally, you start providing recommendations or actions about how to optimize your system or how to reduce the environmental impact of your system. So this could be, for instance, starts reusing construction materials locally by having a local storage space where you can, you know, deconstruct a building, then put all of the materials there and reuse it to a new building or to a renovated building in the future. Or it could be, it could be, let's say, an agricultural practice, a local that has no pesticides or something like that. Or it could be, you know, a very niche activity where you take the waste from a brewery activity, and you include it into, let's say breads or cookies or something like that, or vice versa, all of the stale bread that is unsolved by bakeries, you can reuse it for breweries, etc, etc. So you can have some recommendations of how to change one system, one flow in particular. And this can be very micro or it could be much more, you know, meso or macro, so it could be a big policy. You should have lower vats for, you know, reuse materials rather than new materials, etc, etc. So this is the part of recommendations. So these are the five main steps that you will see in most, you know, material flow analysis or urban metabolism studies. You will see, well, they define a method of calculation. This is often in the, in the system definition and the measurement processes, they tell you what they're going to measure, that's here, how they're going to measure it probably is here in measurement, then they illustrate this synthetically in the illustration interpretation. And at the end, there is an action plan or there are recommendations in terms of policies and actions in order to change the system. So that is it for this video. In the next videos, we'll try to dive in into some other parts of this urban metabolism studies, such as the illustrations. And if you have any questions, please don't hesitate to put them down below in the comments. And let us know what you would like to see next in the next videos. Thanks a lot. And we'll speak soon. Cheers.