Prodded by new laws, designers join France’s emerging circular economy.

By Ilana Cohen

Architecture 2030 estimates that the embodied carbon of materials will account for 72 percent of emissions associated with new construction between now and 2030. The Sustainable SITES Initiative further underscores the importance of materials in the landscape context, as their selection accounts for up to 41 of 200 possible points in the project rating system—more than any other section. Worldwide, designers are looking for ways to create meaningful landscapes with lower carbon footprints through smart material choices. One approach is the reuse and recycling of construction materials. While such strategies are used in the United States, reuse is often rejected as expensive, logistically complicated, and difficult to implement in traditional design projects. But in France, reuse is becoming mainstream, and landscape designers are developing innovative approaches to reuse in new projects and recycling materials that cannot be reused.

François Vadepied, a cofounder of Paris-based Wagon Landscaping, is committed to recycling construction debris from on-site demolition into planting soil. Since founding Wagon nearly 15 years ago with partner Mathieu Gontier, Vadepied has been focused on design/build, deeply involved in the construction process of their projects, and relying on preexisting site conditions for both design inspiration and material sourcing. Intent on reducing the quantity of valuable agricultural soils imported onto landscape projects, Wagon has developed a process for crushing, sorting, and layering materials found on-site, using limited input of compost to infuse this mixture with nutrients. In 2021, the firm tested this strategy in a dense Parisian neighborhood, in collaboration with the social housing developer Élogie-Siemp. In an otherwise banal entry courtyard for an unassuming building in the city’s 11th arrondissement, Wagon transformed a hardscape surface into a thriving garden.

Unlike other similar projects in which asphalt is moved off-site to create room for vegetation, here, no demolished materials left the property. The aggregates and crushed concrete were the basis for the soils, mixed on-site. The broken asphalt topcoat became integral in the border detail and functioned as a mulch-like surface. The entire planting area is framed by a simple wooden edge, an important element in the design that reinforces the intentionality of the gesture. Loved by the residents and visible from the street, the lush vegetation belies the nutrient-poor composition of the soils. The firm has developed a planting palette of species accustomed to difficult, dry conditions, drawing heavily from alpine palettes and including pioneer species such as birches and hardy naturalized trees such as the empress tree (Paulownia tomentosa). Vadepied believes that the planting soils typically imported onto urban sites are richer than needed for plants to thrive. And in the face of climate change, he insists that we need to select more resilient species that can survive in poorer soils. Another project, the Jardin Joyeux in the Parisian suburb of Aubervilliers, is slightly larger and has a wilder aesthetic. Since its creation in 2016, no new materials have been added and there has been no irrigation. With its successes on these two small projects, Wagon is working with its clients to replicate these strategies on larger-scale projects.

Wagon has an unconventional methodology that facilitates experimentation with materials. This cultivates a creative environment within the firm that encourages innovation, but shifts in the materials economy have helped to push these ideas into more mainstream design/bid/build project structures and larger urban projects. In 2020, the French government passed a sweeping antiwaste law that, among other things, increased the cost of waste disposal; it also required extensive inventories of deconstructed site materials and provided incentives for their reuse. From this, a field of reuse consultants has developed, with more clients stipulating that these experts be integrated into project teams in RFPs. Reuse consultants perform diagnostic inventories of existing site materials prior to demolition and assess the potential for reuse on-site. They also support designers when developing details and writing specifications. As many architectural projects have a significant landscape scope, landscape architects are regularly involved in these collaborations. Violaine Dubin, a project manager for Paris-based Mobius Réemploi, notes that material reuse is often easier to achieve in the landscape than in architecture. She says landscape is much less regulated in France than architecture and is also more forgiving of materials’ diminished structural capacity, though she acknowledges that this applies only to durable materials that can withstand the elements, such as stone or brick.

While national regulations for waste management play a key role in setting the stage, municipal and regional actors play important roles in facilitating reuse. The city of Paris has a large facility in its eastern suburbs, the Center for Materials and Supply (CMA), which stores objects with reuse potential. Materials include tree grates, bollards, benches, and fencing, but especially stone pavers and curbs rescued from upward of 400 construction sites active annually within the Parisian public realm, where stone paving is found beneath asphalt. The quantities are impressive: 8,000 to 10,000 tons of pavers are recovered from Paris every year. By volume of stone extracted, the city can be compared to a quarry, but reused stone’s costs have become competitive with new stone. Louis Destombes, a project coordinator for the reuse consultancy Bellastock, notes that while typically reused material remains more costly than new, paving stone prices are lower than new pavers from a French quarry.

The CMA is not unique, and material depots both public and private exist throughout the country. Such local initiatives provide much-desired material stock for landscape architects interested in specifying reused materials at a competitive cost. Designers of the public realm interact with the CMA much like they would with any product vendor. Emma Blanc, the founding principal of Emma Blanc Paysage, describes the process: “We first had an exploratory visit where we saw the stock of stone of varied dimensions and colors; that permitted us to imagine a project and define what we wanted in terms of color, length, and shape. Then we developed material specifications that we transmitted, and they finalized the selection based on our detailed criteria.” Blanc used these materials to rehabilitate two iconic Parisian public spaces, the Place du Panthéon and the Place de la Bastille.

HUGO BRULEY SAYS REUSE HAS PUSHED HIM TO BE MORE FLEXIBLE.

At the Panthéon, visitors cannot help but notice the little stone benches that populate the plaza, in place since 2018. Through their repetition, they create a playful, slightly irregular field around the famed building. The solid, sturdy nature of their materiality contrasts with the delicate wooden feet on which they rest. This field of stone is interspersed with large wooden platforms. Benches, tilted surfaces, and a long picnic table are all supported by the same granite blocks that parade around the rest of the plaza. These humble chunks of granite, once curbstones, have carried Parisians as they traverse their city for generations. Blanc explains that, for her, the material choice was clear. Working on a site of national patrimony, using materials that have an important historic link to the site was critical, as was valorizing them in their original state. Even though the project was commissioned as a temporary installation, the materiality and detail give it durability that feels at home in this storied site.

Despite the advantages, there are design challenges. Hugo Bruley, the principal of Hugo Bruley Landscape Architecture (HBLA), also in Paris, notes that when specifying reused materials, he has to relinquish a certain amount of design control. Uniformity is not always possible, as it can be hard to find large material stocks from the same origin. With less control over sourcing, there may be surprises when the material arrives on the construction site. This can be tricky for designers such as Bruley, a self-described control freak. But he appreciates the challenge and says reuse has pushed him to be more flexible about modifying his project details during the construction process. He stresses that prototyping has become even more essential than before, and he includes extensive requirements when writing up specifications for project elements that incorporate recycled or reused materials.

This is particularly the case for projects on which materials are repurposed on-site. In one such project in the Lyon suburb of Vénissieux, Bruley designed benches from reused slabs of poured-in-place concrete found on-site. The project transforms the existing concrete esplanade of a social housing complex into a greener space that is more adapted to both climate concerns and community needs. The design cuts large rectangles of concrete and stacks them on top of one another to create benches. The resulting openings are then planted with trees and low ground cover that provide shade while maintaining visibility. The design plays with the slabs’ distinct surfaces: the finished top and the uneven underside of the original concrete pour. A thick layer of mortar binds the irregular slab bottoms, while the smooth finished surface becomes the top of the bench. The result resembles an enormous layer cake.

Currently in the prototype phase, Bruley is discovering the material’s properties and adjusting the design accordingly. The contractor has tested methods for removing the concrete using both saw-cutting and controlled jackhammering that result in more or less rough edges. They have also experimented with different thicknesses of mortar between the slabs to see how much is needed to ensure level surfaces. The client, a public housing authority, appreciates the prototype process, as it predetermines the site improvements to be made, is highly visible to the residents early in the construction project, and reinforces the housing authority’s commitment to the community.

Local development authorities have started to require that certain percentages of materials be obtained from recycled sources in their projects. Plaine Commune, an administrative district of the greater Paris region, and one such authority that manages public realm projects in the suburban northwest part of the city, has developed strict standards for integrating material reuse, requiring that 20 percent of landscape materials be derived from recycled or reused sources, with a minimum of 5 percent reused. Bellastock worked with the authority to determine how the circular economy could become integral to the region, which had the largest amount of demolition and construction projects in France between 2010 and 2020. Plaine Commune is also the home of the 2024 Olympic Village, and Solideo, the authority in charge of Olympic construction, has similarly instituted strict requirements. Bruley’s firm HBLA is one of many working in this area, and he believes that the games have proved that it is possible to systematize reuse in large projects. HBLA’s 11-acre public space in the Olympic Village, currently under construction, includes concrete made from recycled aggregates, recycled paving stone, and engineered soils made primarily from demolition debris.

The French are by no means alone in this materials renaissance. The European Union required that each member country enact legislation intended to reduce construction waste and encourage the circular economy by 2020. These laws have usurped cost and logistics concerns and given a green light for experimentation. Now that so many different strategies are being tested, the projects are making clear that the benefits to reuse clearly outweigh the costs.

Ilana Cohen is an adjunct instructor in the landscape architecture program at École Nationale Supérieure de Paysage de Versailles and a project manager and designer at Atelier Roberta in Paris.