Julien Dossier “We don’t know how cities will respond to climate change”

As part of our second magazine ForHum, we met with Julien Dossier, founder of Quattrolibri and an expert in carbon neutrality.

Julien Dossier is one of those who remind us that there are 372 months left before we reach 2050. 372 months to achieve carbon neutrality and minimise the impacts of climate change. In his latest book on the ecological Renaissance, he lays out a new way of imagining and thinking about the society of tomorrow and the work that must be done to achieve it. Inspired by the past and rooted in his time, Julien Dossier seeks to create a new interest in the future. He has a forward-looking, lucid and expert take on how to transform these great challenges into great opportunities.

ForHum: By way of introduction, what do you put behind the term “low-carbon”?
It’s an expression that’s very much in use right now… 

Julien Dossier: The term “low-carbon” means nothing. In fact, I think that today we should prefer the term “carbon-neutral”, which is an objective that stems from COP 21. This is the bare minimum we need to reach in 2050. I am referring to the P1 pathway of the October 2018 IPCC report on the temperature rise of more than 1.5° which allows carbon sequestration after a huge mitigation effort has been made and which is based on biological sequestration technologies (forest, agriculture, soil). 

Land use thus becomes a major issue. Yet at the same time, cities are tending to develop, with growing populations… 

Population will increase and there will be population movements. Some areas will empty out and others will fill up. For example, we don’t know how cities will respond to climate change. In Paris, the urban heat island effect is +6° compared to the suburbs. One can imagine that in the future, La Riviera will become unlivable for the elderly, with population movements from the South to the North and to the West. There is also a growing desire for nature in cities. This may lead urban dwellers to think that the city as it is today is not the solution for tomorrow and push them towards suburbs with market gardening, or toward small cities. So we won’t necessarily have over-crowding in cities. 

How are cities preparing for these changes?

Some cities such as Paris have adopted a carbon-neutral trajectory. When they make these kinds of commitments, they inevitably need “short-circuit” eco-resources. For power, for energy, for materials, etc. They will need to create economic activities at their peripheries to feed their carbon-free metabolism. We’re looking at a local model that makes small cities attractive again by capitalising on friendliness, local resources and well-being. We can already feel it today, for example, in surveys on the desire of people living in and around Paris to leave the region. Big metropolises are unhealthy. They’ve reached a dead end. 

From this perspective, how do you think the production system will be organised in the future?

I see local production with the objective of maximising each locality’s eco-resources, with outside connections and exchanges as needed. We need to adapt our industrial fabric. Let’s take the example of cars. Today we have 40 million. They’re all obsolete. We’re going to need to transform our fleet. How do we do this? If we scrap them, it would mean considerable destruction of resources. Many of the components can be reused. For me, that’s the plant of tomorrow, being able to process resources close to home. They say cities are the mines of tomorrow. Today the third gold reserve is the trash bins in Japan!!

What issues do you think need to be addressed in the building and construction sectors?

We have to move towards a search for energy, carbon, and resource efficiency from the start to the finish of the process. Today, there’s almost no resource accounting. The entire construction site must be taken into account. For example, if I build far away from existing flows, it will require additional mobility, and therefore more energy. We need to move towards more simplicity. By first asking about the extent of transformation of a building, then the question of reuse and then the question of new materials. Bringing housing into a plant implies a lot of changes… Moreover, today we have to dismantle rather than destroy to maximise the reuse of materials. This is a completely different exercise for construction, which today assumes you have a plane surface available. You have to start with what already exists and ask yourself how to adapt it. 

You talk a lot about bio-based materials such as wood for construction. What about other materials such as concrete for example?

Above all, the question of new materials should come after considering the possibility of reuse. Hoffmann cement has many advantages, including the fact that it does not increase temperature. But if we take a global look at concrete by examining at the triptych of energy – carbon – resources, the big problem with concrete is the need for sand, which is not an inexhaustible resource. Wood, too, is facing major challenges. Today cross-laminated timber cannot be the solution. This type of wood comes from softwoods, which are synonymous with the clear-cutting that destroys habitat for biodiversity and has a strong impact on the soil. The equipment turns the soil over and releases old carbon contained in the humus. One centimetre of humus is 100 years. We should move toward continuous cover forestry. We need to think in terms of soil sequestration. Tree sequestration is very temporary. We’re still in the process of discovering bio-based supply. 

What is the impact, then, for building in cities?  

There’s construction on only 3% of the building stock each year. This pace is incompatible with emission reduction targets. We should currently have as many real estate renovation developers as real estate construction developers. There’s a profession to be invented. We also need to have a more humble mindset on the transformation of cities by asking how we extend the life of what exists. For example, the headquarters of the Council of Europe in Brussels has a façade of reused windows. But we’re still at the embryonic stage. It’s possible, but the “worksite” is huge. 

How can this circular economy be set up in industry?

We have several scales to keep in mind. At the first level, we need large-scale industrial ecology platforms, such as PIICTO at the port of Marseille, which creates synergy between industrial companies. At the second level, on the local scale, we are going to optimise the flow of materials with, for example, buffer zones to store materials taken from one site that can be used for another. But today, material that leaves a construction site becomes waste. We’re going to have to change standards and practices. The third level is that of the craftsman with small flows at the scale of a house. That’s where we need local resources. 

Which actors do you think will bring about these changes?

Those in finance and those who own land are the ones setting the standards. Financing entities are increasingly including climate risk in their calculations. To finance themselves, construction players will have to meet the new and increasingly demanding financial criteria to be compatible with the carbon neutrality scenario by 2050. Similarly, insurers who take a position on ten-year guarantees and the insurability of projects will have to provide much more supervision to architects, developers and planners. A third actor may be the Law with a tightening of the legal framework. We’re aiming for zero net artificialisation, so that means building where the environment is already built up, and not where we’re going to build. We can also see that the major companies are positioning themselves. So things are moving. The question is, how fast? 

Julien Dossier, founder of Quattrolibri, is an expert in carbon neutrality. He provides consulting to pioneers in the ecological transition. He also co-authored Paris’s carbon neutrality strategy (Paris Change d’Ère). He heads the SOLIDEO scientific council for environmental excellence (JO 2024) and teaches on the subject of sustainable cities at HEC business school. His book, “Renaissance Ecologique, 24 chantiers pour le monde de demain”, was published by Actes Sud.

This interview is taken from pages 30 & 31 of our magazine ForHum, currently available for free consultation on our website.