The many layers of our environmental impact

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The water footprint of a product has long been difficult to evaluate. Where does the water come from? What technology is used to process and transport it? These are among the questions researchers have to answer in better measuring environmental impact.

An activity can have many consequences for the environment, from its carbon footprint, water consumption, pollution, changes to biodiversity, etc. Our impacts are so complex that an entire field of research has been developed to evaluate and compare them. At IMT Mines Alès, a team of researchers is working on tools to improve the way we measure our impacts and therefore provide as accurate a picture as possible of our environmental footprint. Miguel Lopez-Ferber, the lead researcher of this team, presents some of the most important research questions in improving our methods of environmental evaluation. He also explains the difficulty in setting up indicators and having them approved for efficient decision making.


Can we precisely evaluate all of the impacts of a product on the environment?

Miguel Lopez-Ferber: We do know how to measure some things. A carbon footprint, or the pollution generated by a product or a service. The use of phytosanitary products is another impact we know how to measure. However, some things are more difficult to measure. The impacts linked to the water consumption required in the production of a product have been extremely difficult to evaluate. For a given use, one liter of water taken from a region may generate very different impacts from a liter of water taken from another region. The type of water, the climate, and even the source of the electricity used to extract, transport and process it will be different. We now know how to do this better, but not yet perfectly. We also have trouble measuring the impact on biodiversity due to humans’ development of a territory.

Is it a problem that we cannot fully measure our impact?

MLF: If we don’t take all impacts into account, we risk not noticing the really important ones. Take a bottle of fruit juice, for example. If we only look at the carbon footprint, we will choose a juice made from locally-grown fruit, or one from a neighboring country. Transport does play a major part in a carbon footprint. However, local production may use a water source which is under greater stress than one in a country further away. Perhaps it also has a higher impact on biodiversity. We can have a distorted view of reality.

What makes evaluating the water footprint of a product difficult?

MLF: What is difficult is to first differentiate the different types of water. You have to know where the water comes from. The impact won’t be the same for water taken from a reserve under the Sahara as for water from the Rhône. The scarcity of the water must be evaluated for each production site. Another sensitive point is understanding the associated effects. In a given region, the mix of water used may correspond to 60% surface water, 30% river water and 10% underground water, but these figures do not give us the environmental impacts. Each source then has to be analyzed to determine whether taking the water has consequences, such as drying out a reserve. We also need to be able to differentiate the various uses of the water in a given region, as well as the associated socio-economic conditions, which have a significant impact on the choice of technology used in transporting and processing the water.

What can we determine in the impact of water use?

MLF: Susana Leão’s thesis, co-supervised by my colleague Guillaume Junqua, has provided a regional view of inventories. It presents the origin of the water in each region according to the various household, agricultural or industrial uses, along with the associated technologies. Before, we only had average origin data by continent: I had the average water consumption for one kilogram of steel produced in Europe, without knowing if the water came from a river or from a desalination process, for example. Things became more complicated when we looked at the regional details. We now know how to differentiate the composition of one country’s water mix from another’s, and even to differentiate between the major hydrographic basins. Depending on the data available, we can also focus on a smaller area.

In concrete terms, how does this work contribute to studying impacts?

MLF: As a result, we can differentiate between production sites in different locations. Each type of water on each site will have different impacts, and we are able to take this into account. In addition, in analyzing a product like our bottle of fruit juice, we can categorize the impacts into those which are introduced on the consumption site, in transport or waste, for example, and those which are due to production and packaging. In terms of life cycle analysis, this helps us to understand the consequences of an activity on its own territory as well as other territories, near or far.

Speaking of territories, your work also looks at habitat fragmentation, what does this mean?

MLF: When you develop a business, you need a space to build a factory. You develop roads and transform the territory. These changes disturb ecosystems. For instance, we found that modifications made to a particular surface area may have very different impacts. For example, if you simply decrease the surface area of a habitat without splitting it, the species are not separated. On the contrary, if you fragment the area, species have trouble traveling between the different habitats and become isolated. We are therefore working on methods for evaluating the distribution of species and their ability to interconnect across different fragments of habitat.

With the increasing amount of impact indicators, how do we take all of these footprints into account?

MLF: It’s very complicated. When a life cycle analysis of a product such as a computer is made, this includes a report containing around twenty impact categories: climate change, pollution, heavy metal leaching, radioactivity, water consumption, eutrophication of aquatic environments, etc. However, decision-makers would rather see fewer parameters, so they need to be aggregated into categories. There are essentially three categories: impact on human health, impact on ecosystems, and overuse of resources. Then, the decisions are made.

How is it possible to decide between such important categories?

MLF: Impact reports always raise the question of what decision makers want to prioritize. Do they want a product or service which minimizes energy consumption? Waste production? Use of water resources? Aggregation methods are already based on value scales and strong hypotheses, meaning that the final decision is too. There is no way of setting a universal scale, as the underpinning values are not universal. The weighting of the different impacts will depend on the convictions of a particular decision maker and the geographical location. The work involves more than just traditional engineering, but a sociological aspect too. This is when arbitration enters the realm of politics.

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