Earth-and-cardboard bricks: can old Amazon boxes replace cement?

It’s a familiar scene: roadworks or a building site starts up at the end of the street and, overnight, the whole neighbourhood feels different.

Lorries, dust, concrete mixers, that heavy, grey smell that seems to cling to the air. On the surface, it’s just another building going up. Behind it, though, sits a quieter story - one about a material, cement, that is slowly choking the planet.

On a winter morning in Delft in the Netherlands, the atmosphere could not be more different. No metallic clatter, no spinning drums of wet concrete. Around a table, slightly bleary-eyed researchers stir bowls filled with… brown earth, clear water and torn-up bits of cardboard still printed with Amazon Prime branding. One of them lifts a dried block, thumps it with a fist, and the sound is crisp - like a knock on a brick. No one says much, but everyone smiles.

That block isn’t cement. And that’s where the story changes direction.

The day used cardboard replaced cement

Inside a small research shed, the concept sounds almost disarmingly straightforward: take local soil, combine it with water and fibres from recycled cardboard, then let nature do the rest. No heavy industry. No kiln at 1,400 °C. Just time, air and light. What you get are earth-and-cardboard bricks - they look a bit like rustic loaves, yet they can carry a surprising load.

In the lab, they call them “earthy bio-composites”. On site, builders simply refer to them as “cardboard bricks”. You can stack them, render them and drill them much like standard blocks. Snap one open and you can clearly see paper fibres threaded through the earth like a brown felt. This isn’t a living-room eco gimmick. It’s a material that could genuinely stand in for cement in certain types of construction.

The figures, however, are not so reassuring. Cement accounts for roughly 8% of global CO₂ emissions - more than aviation and shipping combined. Every bag carried onto a building site is a small carbon charge. Set against that, the earth–water–cardboard mix looks like something out of a grandparent’s kitchen. A pilot study found that these “low-tech” bricks can cut the carbon footprint of a load-bearing wall by up to 80%, depending on how local the soil is and how much recycled fibre is incorporated.

A concrete example comes from southern Spain, in a rural area where concrete houses crack under intense heat. A team of architects and researchers suggested building a small community library using only soil dug from the site and cardboard collected from nearby shops. Locals spent several weekends tearing up fruit boxes, moistening the earth and pressing bricks into wooden moulds.

The build felt more like a neighbourhood workshop than a conventional site. Children jumped on the mix to compact it; older residents talked about how people once built with raw earth. A year later, the building is standing, the walls “breathe”, and the interior stays cool even in the height of summer. Most striking is how little upkeep it needs: a few patches of render, a quick check on the joints, and that’s about it. Every brick already carries a story of local reuse.

So why does it hold together when we’re talking, quite literally, about soil and old boxes? The answer is microscopic. Cellulose fibres from the cardboard behave like organic reinforcement. They interlock with soil particles, help stop cracks from spreading and soak up small deformations. Where a simple earth block might split and crumble, the earth–water–cardboard blend acts like a kind of cold-made “plant-based concrete”.

Researchers have also found that certain slightly clay-rich soils bond especially strongly with paper fibres. There’s no need for complex chemical additives. Water alone is enough to trigger this unlikely marriage between mud and cardboard. Let’s be honest: hardly anyone is doing this in the garden every weekend. Still, the idea that a parcel delivered yesterday could end up in a school wall tomorrow completely upends how we think about waste.

How to build a wall from soil and Amazon parcels

The basic method reads almost like a recipe. You start by taking local topsoil, steering clear of patches that are too stony. It’s roughly sieved to remove stones and larger debris. At the same time, used cardboard is cut into strips and then into small pieces. It’s soaked until it turns into a fibrous pulp - a rough, DIY papier-mâché.

Then comes the mixing. Researchers trial different proportions, but a common ratio is around 70% earth, 25% cardboard fibre and 5% water, adjusted by feel. The right texture forms a ball in your hand without crumbling or becoming overly sticky. The mix is then rammed into wooden moulds, brick by brick, or applied in successive layers - like a modern take on rammed earth. Air drying can take anywhere from a few days to a few weeks, depending on the climate.

In a well-equipped laboratory, teams measure compressive strength, water sensitivity and freeze–thaw durability. In real-world trials, early adopters do something simpler: build a south-facing wall and watch what happens. The most common mistakes? Adding too much water, which weakens the block. Using soil that’s too sandy, so it doesn’t bind. Or not allowing enough drying time because a client in a hurry insists on pushing on regardless.

There’s also a very human worry about “living between cardboard walls”. Researchers respond slowly and carefully, with studies and demonstrations: these bricks can be less flammable than bare timber; the fibres are encapsulated within the mineral mass; and the thermal behaviour is gentler and more stable than a raw concrete wall. Ultimately, the hurdle isn’t only technical. It’s about collective trust in a material that doesn’t shine, doesn’t project the “solid” aura of cement, yet may age better as the climate shifts.

“The day we stop assuming that anything heavy, grey and industrial must be safer, we’ll open a huge door for low-carbon architecture,” says a materials engineer involved in these trials. “Our earth-and-cardboard bricks are modest, but they’re already changing the conversation about what a building can be.”

To make sense of it, some experts boil the post-cement shift down to three broad moves that are easy to remember:

• Replace part of load-bearing structures with bio-based or earth-based materials where feasible.
• Treat local waste such as cardboard not as a last resort, but as a primary resource.
• Design buildings to be reversible: demountable, repairable and adaptable without demolishing everything.

Whether you find it practical or not, a list like this gives you a simple lens for judging the next block of flats that appears opposite your home.

What if your future walls looked more like a landscape than a factory?

The question hovering behind earth-and-cardboard bricks is less “does it work?” than “how far are we willing to go to change the way we build?”. Technically, these materials already make sense for homes, schools and small-to-medium public buildings. Politically and culturally, cutting cement out - even partly - scratches at the sore spot of decades of standards, habits and mental images.

Many of us grew up with the promise that concrete was the ultimate symbol of strength, modernity and success. Accepting that a blend of local soil and recycled pizza boxes could do the same job - sometimes better - unsettles that promise. Cities could stop looking like forests of concrete and take on the colours of soils, chalks and clays, closer to the landscapes around them. Architecture that blends in rather than imposing itself.

For once, science isn’t offering a high-tech fix that’s out of reach. Instead, it puts very old gestures back on the table - building with earth - and connects them to a very current problem: mountains of packaging waste. Between the two sits a discreet, low-carbon material that won’t save the world on its own, but does open a gap. It’s easy to picture neighbourhoods where each delivered box doesn’t end up in a skip, but becomes part of a wall, a bench or an internal partition.

The work is still early, standards are slow to catch up, and cement manufacturers won’t step aside quietly. Yet the scene is already set: scientists kneading earth with their hands; residents raising walls from their old parcels; architects drawing buildings by first looking at what lies under their feet. Next time a cement lorry passes your window, the thought may stick: what if we could do without it - at least a little?

Key point	Detail	Why it matters to you
Cement is highly CO₂-intensive	Around 8% of global emissions come from its production	Understand why looking for alternatives isn’t just an expert’s whim
The earth–water–cardboard recipe	Local soil, recycled cardboard fibres, air drying, no firing	Picture how this new material is actually made
Bricks already tested in the field	Pilot projects for schools, libraries and rural homes	See that it’s moved beyond the lab and into real options

FAQ:

• Are earth-and-cardboard bricks really strong enough for a house? Yes. For small and medium-sized buildings that are properly designed, tests show sufficient strength for load-bearing walls, especially when the overall structure is well thought through.
• Do these materials cope with rain and damp? Walls are protected with suitable renders, roof overhangs and good foundation design; water must not be allowed to pool at the base of the walls.
• Is there a fire risk with cardboard inside the walls? Once encapsulated in earth, the cardboard fibres don’t behave like exposed cardboard; tests show a fire reaction comparable to some lightweight mineral materials.
• Can you self-build with these kinds of bricks? It’s possible for small structures, but it’s still wise to work with a professional or a specialist organisation, particularly to comply with local rules.
• Will these materials replace cement completely? Probably not everywhere or for every use, but they can significantly reduce reliance on cement in housing and modest buildings.

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