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Right now, the construction industry heavily relies on concrete and for some good reasons.  Concrete is cheap and it is a highly efficient way to build safe and secure buildings, but it's also so bad for the Earth.  It takes huge amounts of energy to produce and ship the stuff, and these days, concrete alone produces about 8% of global carbon emissions.  In 2018, that translated to almost 3 billion metric tons of carbon dioxide.  

So while concrete is convenient and all, it would be great if we could find an alternative and start making our buildings out of something else.  Well, maybe shockingly, we're not actually the first people to have had this thought.  Many scientists are already conducting research into the materials of the future, and some of their ideas are so off the wall that they just might work.  Here are six of them.

Let's kick things off with one of the weirder examples, synthetic bones.  Because, you know, living in a building made of real bones, that would just be too upsetting.  Scientists at Cambridge have been working on this project since around 2011 and although it may seem odd, there are several good reasons for using bone-like materials in construction.  For one, bones are incredibly strong for their size and weight.  A bone fragment the size of a sugar cube can support over 1500 kilograms, more than some types of concrete.  Also, thanks to their structure and composition, bones are very elastic and resistant to fracture and breaking.  They're made of minerals like calcium and phosphate along with the protein collagen.  That collagen clusters into long fibers and it combines with the mineral in just the right way to create a strong flexible matrix.

Your body made this kind of matrix over years of development, but to make synthetic bones, scientists have found ways to speed up that process.  To make their material, they dip a small template into a solution of calcium and collagen proteins.  Then, they dip that into a solution of phosphate and collagen proteins and then back again.  This process is repeated over and over, layer after layer, until it creates a sample that mimics the strength and structure of natural bones.

This method is great and if we could get it going on a large scale, it seems like it could be a cool alternative to concrete, but it does have its downsides.  Right now, the biggest problem is that the only good place to get collagen is from animals.  This protein is super hard to replicate in a lab, so if we wanted to build something from synthetic bone, we would need a lot of animal parts and while we could use waste from the meat industry, even that might not be enough, so until we figure out synthetic collagen, don't expect to see like, super goth bone cities anytime soon, but that doesn't mean they're off the table, so I want to see in your sci-fi short stories.

Next, the magic of mushrooms is at it again.  While some teams are looking for materials that outperform concrete, others are just looking for things that are safe for the environment, and that's led them down some weird paths.  Take the work of an architectural team known as the Living.  In 2014, they designed and built a 12 meter tall castle, the first and only building to be made of nothing but fungi.  The bricks of this tower were made of recycled mycelium, which are thin branching structures that look similar to roots.

The mycelium was collected from fungi that grew on agricultural waste, like corn and wheat crops, so it was a totally sustainable and renewable material and the bricks weren't that hard to make either.  To create them, researchers placed organic materials, anything from dirt to nutshells, full of mushroom spores into a brick mold, and in only five days, the mycelium had grown dense enough to make a brick.  

As a bonus, because these blocks are made from fungi, they're totally compostable.  If you throw them in a compost heap, they would be dirt again within 60 days.  Still, just because these bricks are ecofriendly doesn't mean they're strong.  They can withstand only about .02 megapascals of pressure, which is less than 1% of what concrete can handle.  Realistically, that means we will not be building mycelium cities.  Instead, researchers have suggested that we could combine the mycelium with other things to make more stable structures, so it's a start.

Both synthetic bone and mycelium are pretty futuristic materials and it's gonna take a lot of work to figure out how they might fit into our world, but this next example might be pretty easy to adopt.

In 2013, scientists at MIT developed 3D printed reusable bricks that function a lot like Lego bricks, except instead of being made of regular plastic, they're made from a carbon-reinforced epoxy resin.  Epoxy resins are a group of materials that easily form strong bonds with other materials like glass or carbon.  They're exceptionally strong and very resistant to erosion or damage, and in this case, since they're being 3D printed, they are customizable, too.   Engineers can make structures stronger or more elastic by assembling the resin bricks into different shapes. 

Now, to be clear, most epoxy resins aren't that environmentally friendly.  They're basically a type of plastic and plastic is, you know, terrible for the environment.  It requires a lot of natural resources to make and takes forever to disintegrate, but these bricks try to make up for that by being extremely reusable.  They're easy to retrieve when a building needs to be taken down and they can be used again and again for new buildings.  Also these things are surprisingly strong.  Structures made from them can withstand 12.3 megapascals of pressure, which is incredible for such small and light materials.

For comparison, average concrete can withstand 17 to 28 megapascals of pressure, and it's much heavier and worse for the planet.  Researchers believe these blocks might not be strong enough for skyscrapers, but they could be used in much smaller buildings like houses, and it's not hard to imagine a future where a crew shows up, stacks a bunch of blocks together, and creates the shell of a house, so again, if these bricks can be mass-produced, it could mean great things for construction.

The last three examples have been pretty innovative, but they've almost entirely ditched traditional building materials and gone in new directions.  That's great, because new ideas can lead to big places, but it also means that it might be a while before these things hit the prime time.  These next examples, though, are a bit different.  They're more practical and probably wouldn't be as expensive to implement on a larger scale, so you might be seeing them enter the market a bit sooner.

One option like this is called AshCrete and it's a modified version of concrete.  Standard concrete is made by using cement to bind together small aggregates like sand, gravel, or crushed stone.  This makes it heavy and hard to transport but also those aggregates aren't sustainable.  We only have so much sand and stone to throw around. 

Enter AshCrete.  It's an alternative concrete made using the ash from waste incineration facilities as the aggregate particles.  It can be used in many of the same places as traditional concrete and it allows those waste facilities to recycle some of their ash, so win-win.  Unfortunately, although it can solve some of concrete's problems, it's not perfect.

Most notably, making and transporting AshCrete requires the same amount of energy as concrete and this new material isn't great for all climates.  Compared to regular concrete, AshCrete can take longer to solidify and it's more succeptible to cracking from freeze/thaw cycles, since it doesn't trap as many insulating air particles.  

So it has its flaws, but if we want to start rolling out better materials for the planet soon, it might be a good place to begin, and besides AshCrete, there's also a number of other materials that try and improve upon things we have now.

For instance, scientists have also thought about trying to reinforce clay bricks with two of the most renewable substances we've got: wool and seaweed, which sounds weird but would work surprisingly well.  Although they don't get as much attention as concrete, regular clay bricks are a huge pollution problem because they require a ton of energy and natural resources to make.  Like, not only do you need things like soil, sawdust, sand, and lime to make the brick, but then you have to fire it and that means you have to burn things like wood or coal and that results in a bunch of carbon emissions.

One way companies try to clean up this process is by making what's called a non-fired brick, where you use a machine to smash a bunch of clay together and then let it dry in the Sun.  The problem here is that the final product typically isn't as durable as fired brick, but there might be a way to change that, at least according to a 2010 paper published in the journal Construction and Building Materials.

In that paper, two architects suggested using wool and seaweed to make these bricks even stronger.  In these blocks, wool fibers are mixed with a natural compound from seaweed called alginate.  Then, that's mixed into traditional non-fired clay bricks.  The alginate acts as a binder instead of sawdust and the wool fibers increase the strength and structure of the bricks, by a lot, actually.  Traditional non-fired bricks have an average strength of around 2.3 megapascals, but in a test, scientists demonstrated than when both alginate and wool are added to the blocks, the strength increased to around 4.4 megapascals, almost double.  That would make them great for things like walls, small houses, or decorating, and with much less of an impact on the planet.  

Finally, our last and most practical example, because look, sometimes the future starts small and that's okay.  Say hello to the pollution absorbing brick.  These bricks were developed in 2013 and admittedly, they are made of traditional concrete, since that allows them to be competitive with current materials, but they're trying really hard to make up for that. 


These blocks take in pollution from outside air and then release clean air into your building through a traditional ventilation system.  So these things have two main components.  The first is, of course, the brick itself, which faces the exterior of the building.  Each brick has a cyclone air filtration system in it, which creates a superfast spiral vortex inside the brick, sort of like a mini hurricane or a centrifuge.  As the vortex spins, the heavy pollutant particles drop to the bottom of the vortex and are deposited into a collection hopper at the bottom of the wall.  The second component is the recyled plastic couplers, which go between each of the bricks.  These couplers both help align the bricks and allow air to get into the center of the bricks and the filtration system.  

The blocks can trap about 30% of pollutants from the air they touch as well as 100% of coarse particles like dust.  This makes them a great potential way to passively clean up the air in our cities.  So even though it won't solve our concrete problem, it is a start and it could likely help us with at least some of our environmental woes.  

There's a ton of cool research being done into alternate construction methods and the list goes way beyond these six examples.  That's important to keep in mind because any one of these solutions probably can't make construction eco-friendly all by itself.  We're gonna need tons of alternative options so the more ideas there are, the better we might be, and things seem to be moving in the right direction, at least based on these projects, and one way or another, it's cool to see what kinds of solutions engineers are coming up with, even if I never get to live in like, a sweet bone building.

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