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How an ancient building technique could help solve the climate crisis

More than half a billion tons of construction and demolition materials end up in U.S. landfills every year. Reusing that rubble, as our ancient ancestors did, could offset the waste.

How an ancient building technique could help solve the climate crisis
[Photo: Courtesy liminal]
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On a rocky hillside in an agricultural village halfway between Rome and Naples, an ancient form of building is being revived. Dry stone masonry—a technique dating back thousands of years—is being used to help restore the rocky terraces that have enabled agricultural activity in communities across Italy. How those structures are being rebuilt hints at a new, more sustainable approach to architecture and construction.

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The terraces are the focus of architect Nicolás Delgado Álcega, a recent graduate of Harvard’s Graduate School of Design. Part of his thesis involved working in collaboration with an agricultural collective in the rural community of Vallecorsa to restore its terraces to allow cultivation. Terracing this land turns rocky hillside into arable soil.

“It’s a very old settlement, it’s pre-Roman. They had terraced about 2,000 hectares of land and really built soils and made arable land where there wasn’t any in order to sustain the growth of the population. It established a whole new environmental balance,” Delgado Álcega says.

But like many parts of rural Italy, the region’s economy has shifted and the population has shrunk. The terraces have been left to crumble. Delgado Álcega and his partner, Ginevra D’Agostino, expanded on his thesis work to help the agricultural collective in Vallecorsa to rebuild the terraces. Instead of bringing in new material or hiring contractors, the architects worked directly with the collective’s members to use existing rocky material from crumbling terraces and the landscape to recreate the dry stone masonry approach that was originally used to build the terraces. By creating these spaces for cultivation, farmers are able to use their land more productively, carving a path for environmentally and economically sustainable agriculture.

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[Photo: Courtesy Brandon Clifford]

This work was inspired partly by The Cannibal’s Cookbook, a publication exploring old and prehistoric building techniques, by MIT architecture professor Brandon Clifford. The Cannibal’s Cookbook offers a series of what Clifford calls recipes for rethinking architectural construction based on ancient forms of building, such as stone walls in Peru and Greece that date back thousands of years. Originally released in 2018 in a small printing of just 250 copies, Clifford’s book is now being more widely released by publisher ORO Editions. The concept involves “cannibalizing” existing structures, or using existing resources to build something new. While Delgado Álcega was still at Harvard, he used approaches from the book to build a small wall as a class project, and later took Clifford’s course at MIT.

“The mission of the cookbook is to offer the alternative point of view to what we’ve been doing since the industrial era, which is to produce buildings with the assumption that they’ll last forever, particularly concrete buildings,” Clifford says. “Since industrialization we’re essentially the only civilization that hasn’t found a way of reincorporating our building stock back into future buildings.” He says we have lessons to learn from Peruvian rubble walls that are nearly 1,000 years old and the structures at Machu Picchu that date back to the 1400s.

[Photo: Courtesy Brandon Clifford]

It’s a concept Clifford has explored through Matter Design, the Boston-based architecture studio he founded. One project used chunks of concrete from a demolished Motel 6 to build a precise and gently curving prototype wall. By scanning and processing building rubble, Clifford uses algorithms to automatically select pieces that can be minimally altered with robotic carving to fit together into walls and structures without any mortar required to hold them together. Based on old ways of building, these perfectly fitted pieces can form the basis of buildings that can stand for centuries, according to Clifford.

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This form of construction is only just beginning to be tested, and may only be viable for certain types of projects or in certain regions—retaining walls in seismically inactive areas as opposed to skyscrapers on fault lines. But with more exploration, it could be a way to overhaul how structures get built. Clifford says that by using the methods outlined in the book, builders may eventually be able to take the rubble of demolished buildings and use it to construct entirely new buildings, reducing the waste and landfilling of construction material and foregoing the production of new materials.

[Photo: Courtesy liminal]

The impact of this shift could be significant. More than half a billion tons of construction and demolition waste ends up in U.S. landfills every year, and the production of common building materials like concrete and steel have a significant environmental impact. “Concrete is really the central problem in the building industry,” Clifford says. “You’re casting a material that appears to be a permanent material but the reality is that it has a mortality embedded in it.”

The book suggests that concrete rubble from a demolished building or decommissioned bridge could easily be reused in projects like retaining walls or other infrastructural projects that would typically rely on newly cast concrete. Systematizing this kind of reuse, Clifford argues, can help reduce the environmental impacts of building.

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“Not only do we need to think about what we do with our buildings after they’re demolished, because we have all this rubble that we’re just landfilling, but the other side of it is we need to think about how we’re constructing our buildings,” Clifford says.

In Italy, Delgado Álcega and D’Agostino are putting this concept into practice, albeit at a small scale. Their work with the agricultural collective is about reusing material, but also restoring systems that the collective can use as a basis for renewed economic activity.

“For us this question of terracing became really exciting because terracing as a kind of a landscape infrastructure has some really interesting qualities that other technologies don’t have,” Delgado Álcega says. Instead of soil all washing down the rocky hills, it is captured in the terraces, building up over time to create arable land that supports biodiversity and improves the hydrological patterns of what would otherwise be a dry hillside. Without the terraces, the soil slips away and agriculture is nearly impossible.

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Delgado Álcega argues that recreating these terraces in Vallecorsa and other agricultural communities in Italy can be the basis of a broader economic rebirth, enabling people who may have left the region for city jobs to return and make a living. Making that happen is a complex task, Delgado Álcega concedes, but it might just start with rebuilding these ancient terraces.