Earth Factory

Earth construction is taking off in France, with a wave of new buildings appearing across the country. There also new networks supporting the growth of interest in the material, including Cycle Terre, the country’s first earth materials production facility in Sevran, northern Paris.

Photo Renou Schnepp/Cycle Terre

The air is thick with the pallor of construction the February morning I emerge out of the Paris outskirts station, Sevran Beaudottes. Lorries manoeuvre, cranes swing high above and the sounds of the building site ring out. Sevran, one of Paris’s banlieue districts North-east of the capital proper, will get a brand new station, becoming one node in what is currently Europe’s largest transport construction project: Grand Paris Express. The ambition is dizzying; the fully automated transit network features four new routes with 68 new stations and 200 kilometres of new track, the majority underground, at a budget of €22.6bn, part of plans to stitch together greater Paris into a connected metropolitan region and to all be ready by 2030.

Sevran Beaudottes’ clamour of construction is echoed across the other stations, rail track and tunnel sites. Not entirely surprisingly Grand Paris Express is a vast earth mover. For years, managing and excavating waste from construction sites has meant earth, soil, spoil and rubble transported and then dumped in landfill sites, creating man made mountains but not that much else bar hefty carbon footprints. Just imagine the numbers from 43 million tonnes of earth and waste materials, Grand Paris Express’s estimated excavated waste over its construction life cycle. Still Grand Paris Express big dig is dwarfed by the Ile-de-Paris’s anticipated next twenty year total construction figure: a staggering 400 million tonnes.

The Earth Cycle Factory, in Sevran, is a hybrid building in raw earth, wood and concrete. Photo Paul-Emmanuel Loiret

Now, though, a short distance from the Sevran Beaudottes station building site is a project that seeks to short circuit the logic of what for one person is waste, and for another is treasure going to waste. The realisation that the Grand Paris Express project would unearth vast amounts of the stuff underfoot, including at Sevran Beaudottes, initially propelled the idea forward. Rather than trucked to landfill management sites, an on the doorstep source and raw earth resource could be sifted, filtered, and turned into new earth materials. All of a sudden Sevran was the first site in the country where earth production is sourced from waste, and a textbook example of the circular economy.

Less grand than Grand Paris Express, and several notches simpler, Cycle Terre an initially three, now - after Covid and other delays – four-year experimental research project, has set out to do just this, that is creating virtuous materials cycles. Rather than going to waste mountains, earth, clay, and soils from the new station site is routed to a production facility to be turned into earth materials. One of the first in Europe, and the first earth production facility in France has been founded, literally, only a few blocks from the rail station site.

Photo Oliver Lowenstein

The production facility opened in December 2021. Almost a factory, and run as a Co-operative Collective, the Cycle Terre factory’s large open space is comprised of a set of raw earth storage bays, several pieces of specialist machinery, and further post-production storage bays. Set in an industrial estate with industrial warehouses each side, Cycle Terre stands opposite two neighbouring buildings, which at the time of my visit were, somewhat weirdly, being converted into an evangelical church and a mosque. The building, in effect a four pitched roof shed, with first floor admin and lab rooms, was designed by the now disbanded Paris studio, JolyLoiret Agence d’Architecture, whose co-founder, Paul-Emmanuel Loiret is an earth materials advocate and president of the Cycle Terre team. A primarily wood frame structure 12 metres high, featuring both compressed earth bricks and experimental earth coated panels. “It is mainly natural materials,” Loiret emphasises over the phone some weeks after my visit. “We wanted to make it open to the environment, so people could see what is happening in it, not a building closed off to the public.” The small scale of the multiple roofs is, continues Loiret, to emphasise the local in local production, and help spur a countrywide network of decentralised earth hubs into existence.


Photo Lasa Equipment

That at least is the ambition. A first showcase step towards creating future earth building network infrastructure, the facility is but a container for the main objective, spreading the word and the use of earth materials themselves. When I visited this February my guide, Silvia Devescovi, project manager of the Cycle Terre project, within Sevran Municipality noted the potential for such a network, though also a list of challenges. Size, for one, can be seen another way. The facilities relatively small footprint, 2400m2 constrains the site, and its production possibilities. The facility can produce up to 600, 000 bricks a year, Devescovi told me, as we walked round, the building, light glinting in through the open unwalled spaces. Devescovi walked over to one internal wall, pressed a button, and the doors gradually lifted revealing a large storage unit. Inside were stacks of compressed earth blocks (CEB) carefully stored away, this is the primary material slipping off the production line. The production number could have been higher, Devescovi said, had there been more storage space.

Four materials and three production lines were planned for the first stage of the factory’s life, compressed earth blocks, mortar, coatings and earth panels, although the latter is still at the experimental stage. Add to the material production and factory, Cycle Terre has involved the R&D required for technical certification, alongside a further dissemination programme aimed at popularising earthen building among developers, architects, and other urban professionals, as well as work to develop a network of regional earth production facilities. Within Sevran, there are also testing facilities and a slew of new kit to trial and try out. Like the larger scaled Grand Paris Express rail infrastructure, the programme unsurprisingly folds into regeneration and economic uplift for Sevran and its immediate environs. As one of Paris’s banlieues, Sevran’s population is one of France’s poorest districts with a predominantly north and sub-Saharan African population, a 2013 article in The Economist stating unemployment among the post school 18 year old age group was at the time over 40% - twice the national average. So far Fabrique Cycle Terre has created twelve jobs, not exactly a large number, although Devescovi believes the project will eventually train around two hundred people. A key objective is to turn Fabrique Cycle Terre into a training hub for local construction companies, creating social support, employment, and providing pathways for more economical enterprises. The technology, according to Devescovi, is easy to use, and training straight forward. Those making the compressed earth blocks can be fully skilled in the processes within a couple of days, even if considerably more experience is needed to ensure the necessary quality control processes and refining and adjusting the raw material mixes.

The mixing unit sat at the back of the factory. A mustard-coloured piece of machine technology developed by Fibo Intercon, a Danish concrete machinery company, the mixing unit can prepare different kinds of mixes for the Compressed Earth Blocks as well as plasters and mortars for dry mixes. There are different recipes composed of the core materials; soil, sand and water - dependent on the kind of finished materials needed – though almost all free from either cement or lime stabiliser. A few mixes are made with cement for small productions of Stabilised Compressed Earth Blocks (SCEB) and associated stabilised mortar, which are used in very specific uses when they are subject to high stresses (friction, water)

Devescovi and I walked from the back of the building to the large front bay area. We passed a robot arm sitting mute. When working, conveyer belts move the mixes from the unit to the CEB Press and Robot Arm for CEB production, or, if producing plaster and mortars to the Big-Bag Filling Station (developed by another company, Mecabag). There is a last independent machine; a bagger, to make bags of 25kg of mortar and plaster.

The tech involved, while limited is central to the production processes. The robot arm was developed by Etienne Gay, a young industrial machine designer from Grauhelt, near the southern city of Toulouse, who had first trialled and tested his Briques Technique Concept machine and had become the first French raw earth Compressed Earth Block manufacturer using robotics in France. Cycle Terre had bought and adapted one of his machines.

“CRAterre has been waiting for this to happen,” says Devescovi, speaking of the internationally respected earthen construction research centre based at the School of Architecture in Grenoble (ENSAG), which has been at the heart of the Cycle Terre project. “They thought that the research could be useful and could easily happen but were always constrained by lack of funding.” There was half a decade worth of development, grant bids and research to have reached this point. The recipient of a 2017 EU Urban Innovation Action (UIA) grant, CRAterre worked with the municipality and twelve other partners, working to a €6.5 million budget, some €3.2million of which went on the building and €800,000 on machinery.

Earth blocks prepared for testing by Cycle Terre’s in-house earth materials specialist in the factory’s first floor office spaces – photo Oliver Lowenstein

Would it work, though? That was the hundred thousand Euro question. Earth production facilities have been around for some time, at least as idea, even if physical realised facilities are far and few between. In Germany, there is Clay-Tec, in Belgium BC Materials, raw earth pioneers, and in Barcelona, Fete de Terra. Only one fifth of BC Materials’s work is earth block production, consultancy taking up the majority of their time. Vorarlberg earth master, Martin Rauch, had begun producing earth blocks in 2021, at his Erden factory, an earthy stone’s throw from his main Schlins LehmTonnErde workshop base. It had been preceded by earlier efforts during his 2014 building of the Ricola warehouse only to close again. In France there had been earlier small projects in the 80’s, but at the scale of Sevran, and indeed for France, Cycle Terre is a first. Not only this, but it is the first earth production facility across the whole of Europe which reuses waste rather than prepared earth.

Devescovi runs through some figures. 85% of the soil comes from the immediate environment, 15% from other regions. Cycle Terre aims to use 8000 tonnes of earth a year, though with a long-term goal of 25, 000 tonnes. The Grand Paris project station is one source of the soil. They deliver good enough quality earth, an arrangement with the corporate landfill management company and project partner, ECT. Interest, she says, has been “huge. There are visitors every day, groups of 40 are shown round every weekend, and regular small groups of architects, though it is still only a drop of water.”

Compressed Earth Bricks – Photos Cycle Terre
Photo Oliver Lowenstein

A drop, but a drop rippling outward and to increasingly responsive audiences and actors. A quiet revolution that has been gaining ground across France. Earth, Geo- or land materials, along with their Bio-based kin, have been taking off among young architects, engineers, and sustainably minded others in the building sector over the last decade. A significant network of radical builders, encompassing professionals and the public, have created a groundswell traceable back to the earlier 80’s generation, of activity, energy, and tangible projects which is inspiring and influencing the latest generations joining the building industry.



The Orangery, in Lyon’s Confluence eco-district by Swiss studio’s Joud & Vergely and Diener & Diener – Photo Benjamin Vergely

“It is a 11, 000 year old material,” says CRAterre’s Alix Hubert on a Zoom call she is sharing with Thierry Joffroy, explaining how complex working with earth is. “it’s complicated. You need to think about everything.” Both are CRAterre long timers, Joffroy, head of the research team, Hubert, an architect and senior researcher, and the discussion is circling round CRAterre’s role as principal source of the Cycle Terre project. Through much of the intervening decades since CRAterre first opened in 1979, the French earth building scene has been small scale, generally individual or two or three person set ups, serving the like-minded, individually, and communities and their networks. Overwhelmingly artisanal, France’s earth building scene, as elsewhere in Europe, can be divided between those who celebrate its artisanal, craft and skills sources, and those who believe earth construction’s potential is seriously limited and needs to be brought into the mainstream through industrialising parts of the process. In this age-old divide of approaches, Hubert states that they are at the practical end, believing that local moderate semi-industrialisation can benefit to local sustainable development. Like others, Hubert and Joffroy have been observing the sea change through the last decade. Up until the early 2010s nearly all projects were small, generally leaning to the rural, before the uptick in interest from towns and indeed, cities began to kick in. Urban projects, and quite large ones too, such as the three storey Orangery building (2021), a Swiss studio collaboration between Lausanne’s Joud & Vergely and Basel’s Diener & Diener, in Lyon’s Confluence eco-district, which was completed last year.

“The shift to land and bio-based materials has been taking off within the last five years:” says Hubert. Earth specialist and architect Loiret has also seen the same shift.

“When I was teaching students in 2017 they didn’t seem sufficiently radical for me”, he adds. “That has changed. It’s a big shift. They all know who Greta Thunberg is now.” Behind the renewed environmental activism inspired by a mixture of Thunberg and scary news about floods and fires around the planet, is new Governmental regulation, requiring 50% of all public buildings to be built from timber and other natural materials. Other influences too, like the knock-on emphasis of circular economy approaches, are helping spur earthen building as real and credible options for these young architects, engineers, and others across the sustainable end of France’s construction sector.

Committed to mainstreaming earth materials, the urban context has always been a priority for CRAterre. After all, as Joffroy points out over Zoom the regional geographic triangle stretching from CRAterre’s home city, Grenoble in the French Alps, to Lyon and Saint Etienne, and across to Clemont Ferrand in France’s Massive Central uplands has been a cradle for European earthen building. For the better part of 150 years, through the late 1700s and 1800s big cities and smaller towns saw hundreds and hundreds of urban earth buildings built across the region, a geological result of the region’s clays and soil being particularly suited to earth building.  In Lyon, there are probably over 2000 buildings still standing, with many up to six and seven storeys, a result of the era’s construction converging with industrialisation by the second half of the 18th century.

For CRAterre an earthen production facility within a major city made absolute sense. It would advance their efforts to bring earthen construction into urban centres. Close to construction developments meant a low material miles footprint. Nor did facilities need to be large. Rather, given the cost of land, a small setting was financially sensible, in effect localised industrialisation, close to where the earth is needed.

Paris, as the capital had an inevitable logic as the first site. At the same time, Hugo Gasnier, a recent PhD student, examined earth resources across the Ile-de-Paris region, highlighting the potential. JolyLoiret supported Gasnier, using his research on developing an earth tower concept. There was further input from Akterre, a small Rhone valley company who supported developing the production processes for mortars and plasters. Each added to the case CRAterre built for the project. The research would also generate new knowledge – such as earth block compression testing and acoustic evaluation and fire testing of CEB walls R&D - with the potential to spread more widely than earth constructions’ traditional base of the network of skilled artisans.

Gatinais Park information centre – Photo JolyLoiret

For those involved from the beginning, CRAterre and Loiret, the architect, suggest that the stars aligned for a moment to help the project into being. Sevran’s municipality made contact just at the right moment. Loiret, had for many years been immersed in earthen materials, having first become interested in their construction in the early 1990’s after witnessing many impressive vernacular earth buildings while undertaking military service in the ex-French colony, the Ivory Coast. Loiret’s fascination further deepened during travels in South America, through architecture school in 2000’s, and then several jobs in various Paris studios. Teaming up with an ex-Renzo Piano studio architect, Serge Joly, in 2007, their JolyLoiret Agence d’Architecture began to try to realise several earth projects. One early success was in the regional Gatinais park, about 70 kilometres south of the capital - an information centre facility in the park’s Milly la Foret. Completed in 2013, Loiret and the studio used adobe for the information centre’s ground floor. But generally, persuading people of earth’s merits proved an uphill grind. Another early project, featuring a climatic earth wall in Southern Paris, opened Loiret’s eyes. When it came to building the wall, he was stunned to realise there was “absolutely no local earth materials.” Nor any facilities, or factories. “There wasn’t anything.”

This regional blank canvas helped seed Sevran. The lack of projects spurred Loiret to take up part time research at CRAterre, in 2013, split between the lab and teaching. He would stay there for seven years, until 2020.

JolyLoiret’s experimental earth tower, part of their exhibition

The path to Sevran was involved and happened over several years. In 2016, the Paris Mayor, Anne Hilgado launched her city council’s Re-inventing Paris new buildings programme. JolyLoiret submitted their entry, an earth tower, responding to the first call for projects. Part of the same wave as Grand Huit Architecte’s Ferme du Rail, unlike GrandHuit, JolyLoiret weren’t awarded the project. But the tower did push buttons, not least Loiret’s argument accompanying the bid, the earth materials in the immediate Paris region for making earth buildings were there. According to Loiret this was met with some incredulity among the Re-Inventing Paris team and council members. But they were also curious. And after meetings and discussions JolyLoiret were invited to develop an exhibition and experimentation brief drawing attention to this massive yet unknown building resource.

He spent a summer criss-crossing Paris in search of sites where earth was potentially available. He also brought in CRAterre to be “part of the adventure.” In parallel, a considerably larger and more ambitious earth building project had been getting off the ground. JolyLoiret had managed to persuade the Chinese architect, Wang Shu, and his Amateur Architects studio, to head up a new entry. Rounded out by urban agriculturalist’s Topager, Manufacture sur Seine’s 50,000m2 site featured makerspaces and a photography university; nothing if not ambitious.

Earthly ambition - Manufacture sur Seine render

Where before JolyLoiret’s attempts had faltered, Manufacture sur Seine won through. So far, though, the project hasn’t begun. It will be, once it breaks ground, the largest earth materials project in France and Europe. One early snag, though, was that no-one was certain whether there was enough earth for the project. Nor, for that matter, at the time of its submission, were there the legal regulatory certification. And Loiret knew by now there weren’t any contractors with the required expertise in earth materials to be able to carry out the work come construction time.

And then, right at the critical moment, out of the blue, at least the way Loiret tells it, a few weeks after winning the competition Sevran Municipality and Grand Paris Aménagement contacted the studio asking if an earth project could be part of their EU UIA  bid. Loiret was reminded of the Grand Paris Express project. There would be a lot of digging going on in Sevran. Wouldn’t this be the place for an earth production facility? At first, Stéphane Gatignon, greater Paris’s first green mayor at the time, thought it wasn’t possible, but after meetings, further research, and discussions with CRAterre, the bones of the Sevran earth production facility fell into place.



That was then. Six years on Cycle Terre has happened. Sevran can now claim this out-at-the-edge earthen production line facility. The big question is will it work? Will it deliver as a financially viable set up? Cycle Terre, various of the conversations suggested, needs the orders today. Orders are coming in; Rosny-Sous-Bois’s radical bio-and land-based council architects have put in an order for 50,000 compressed earth bricks. Earth is increasingly a big deal with architects. Devescovi is being kept busy with visits and the surge in interest, particularly among young architects. And, according to Loiret, not just young and radical architects. There’s a major cultural and sports venue, Colisée-Grand-Paris, in near-by Tremblay-en-France, where corporate architects DVVD are planning to use earth materials in their design. He thinks he’s persuaded Jean Nouvel - where, after architecture school, he worked - to build in earth. The super-sized Manufacture sur Seine project is lined up, but won’t be happening for a few years, 2024/25 earliest, while Joly and Loiret have gone their separate ways, with Loiret now running MUE Mutation Ecologique Experiences (Experiences for ecological mutation), a hybrid material sciences-architectural studio, and symptom of changed futures. A new and expanding chapter in a joined-up network look to be beginning. Various cities, including Lyon and Toulouse, have shown interest in developing similar production facilities. There are, Thierry writes in a later email, increasing number of research teams and PhD’s happening across French architecture schools. The pool of research, from data through to practical research projects, is growing, making earth more mainstream accepted. Still, Thierry cautioned, the big issue remains “how far can we go in the industrialisation processes while keeping the spirit of ‘local’”!

“The robot piling the blocks in the factory is a good/bad example of this challenge to find the right balance. But what is certain is that more mechanised systems for manufacturing buildings materials/or building in situ are needed!” There are also other synergies too, not least with related circular economy initiatives emerging, developing towards the sorts of critical mass that a project like Sevran needs to get established.  Include major shifts in EU policy, the post-Covid, Fit for 55 build back greener agenda, and Fabrique Cycle Terre ought to have a bright future ahead. The stars aligned once for Cycle Terre; the hope is they shall do so again.



Photo Renou Schnepp/Cycle Terre