Imagine a material that is biodegradable, non-toxic, and endlessly reworkable into new types of material. Fungi ticks all the boxes, being a natural, biodegradable polymer with similar versatility to a petrochemical plastics, capable of being processed for different end applications.
One of the most promising uses of fungi is as a green construction material. As well as their physical plasticity, they are a low carbon tech and since fungi feed on diverse kinds of biomass, the fungal construction industry could support a wider circular economy by upcycling waste from agriculture, forestry, and the food sector.
Fungi can be used to make diverse building materials with different properties, ranging from spongy fungal blocks that are wholly biobased to composites that fuse concrete or other conventional construction materials with fungal spores.
The fungi life cycle
Fungi species can look radically different as it works its way through the life cycle. They begin as spores that swell under the right conditions to germinate, eventually forming extremely long, threadlike structures called hyphae, which are thin, branching structures that have the appearance of plant roots.
The hyphae stage of the fungi life cycle is important for industrial biotech as they are made from a mixture of industrially useful materials including chitin and other polysaccharides, such as glucans, manno-proteins, chitosan, polyglucuronic acid or cellulose, and smaller quantities of proteins and glycoproteins.
Eventually, the hyphal threads branch and fuse to form the whole mycelium, a structure that allows fungi to reproduce.
Filamentous scaffolds
The ethereal hyphae of a fungi may look delicate but its properties and chemical compounds are generating a lot of excitement in the area of sustainable construction. This is because they are resilient while still being capable of breaking down into non-toxic elements in the natural environment.
In 2017 researchers presented an example of filamentous fungi building blocks at the Seoul Biennale of Architecture and Urbanism 2017. The building blocks were made from feeding filamentous fungi Ganoderma lucidum on plant-based waste.
The hyphae threads of the fungi grew into a dense network that bonds with the loose substrate, fixing the waste in place to form a thick, sponge-like substance capable of being shaped into blocks. These organic building blocks could be used in temporary constructions.
Composites with fungal hyphae could also include mineral substances, making for far more permanent buildings. Astonishingly, there is evidence that fungi hyphae were instrumental in creating some impressively robust natural structures.
The Rimstone Dams in the Huanglong park of China’s Sichuan Province help contain thousands of large aquamarine-coloured pools. These natural dams were reportedly formed by fungal hyphae that originally served as a natural scaffolding for crystal calcium carbonate particles to latch onto.
The living hyphae are long gone but hyphae-sized holes in the core of the crystalline dams point to how these delicate growths were once the architectural foundations of this mineral monument.
Self-healing walls
Fungal building blocks have one performance advantage over ordinary concrete: they have the ability to autonomously heal themselves.
The demo block presented at the Seoul expo in 2017 was completely inert: the living fungi has all been killed off when the blocks were fired and dried. So too were the natural Rimstone Dams of Huanlong Park. These structures would not be able to repair themselves.
However, there are methods for keeping fungal organisms alive in a dormant state within the building material. This opens the possibility of creating self-healing and self-joining ‘concrete’ blocks.
Because hyphae can grow into a dense, malleable network that can work into cracks and bend around corners, building with living filamentous fungi would be very different from building with the inert minerals we use in construction today.
Rather than welding, pasting or nailing, building repairs would consist of the dormant living organism springing to life inside the blocks in response to a crack or damage, leaping around gaps and corners. Researchers have already demonstrated in labs that ‘living blocks’ of mycelium separated by a gap will be joined after just a couple of days.
Researchers have developed the concept of mineral-fungi material fusions that retain the strength and solidity of concrete but hold the automatic healing properties of the living organisms inside them.
Fungal spores and nutrients from the spores are added into the concrete mix in a way that protects them and keeps them dormant but alive. This is technically challenging but not impossible: fungi can survive and adapt to extreme environments with limited nutrients.
When cracks form, water and oxygen follow, waking up the dormant fungi in the concrete and inducing hyphae growth that, like in the natural dams in China, attract calcium carbonate particles that crystallise on them and fill in the gap. The calcium carbonate would consist of Ca2+-ions and the CO32−-ions shed from the concrete environment or due to fungal respiration.
The following are some filamentous fungi that show promise as materials for self-healing construction material:
- Trichoderma reesei
- Aspergillus nidulans
- Umbelopsis dimorpha
- Pseudophialophora magnispora
Self-healing structures are not just a gimmick for showcasing the capabilities of biotech. The capacity to self-repair would be extremely useful for structures that are in constant contact with water or other materials that corrode traditional concrete or metals, or where access for repair and maintenance is difficult. Bridges, marine structures, wastewater treatment plants, tunnels, and underground parking are just a few examples of the industrial relevance of the living fungi building block.
Green insulation
Beyond their use as structural elements, filamentous fungi could have uses in other elements of building design.
Because of its polystyrene-like nature, filamentous fungi could be a good material for insulating sustainable buildings. They have low thermal conductivity and fire safety properties that make them ideal for these purposes.
Another interior feature that today relies on the properties of petrochemicals are acoustic insulation foams. Mycelium composite acoustic insulation foams are already being marketed in the EU and USA.
Generally, working with mycelium composites will achieve greenhouse gas reductions compared to plastic insulation materials.
Overall, it is the energy used to power the manufacturing process that makes up the bulk of emissions impact. This means that rolling out renewable energy is fundamental in scaling the fungal construction industry in a sustainable manner.
In Africa and other developing countries, for example, biobased materials made from fungi and agricultural residues, can actually have a greater environmental impact than fossil-fuel-based materials because most electricity involved in their production will be coming from fossil sources like oil.
Improving the energy efficiency of the fungal manufacturing process and using renewable sources to fuel it will be essential to making sure the industry for mycelium building materials achieves as much greenhouse gas savings on their mineral and fossil counterparts as possible.
Fungal horizons
There are still gaps in our knowledge about the long term properties of using filamentous fungi in construction, particularly in long term uses where their structural integrity in buildings are key.
Researchers are also still sifting through the many millions of fungi species that exist. Only a few of these have been explored and tested in any detail and we may not know all the species that could be useful to the field of sustainable construction.
The use of filamentous fungi in construction and decoration is still in their early stages and functionality is still limited. However, their promising qualities mean that mycelium in some form or another is likely to become a much more widely used construction tool over the next century.
A recent EU project goes even further than exploiting the physical properties of fungi in building work. In a research abstract that approaches a scifi vision, the Horizon 2020 project says that fungal mycelium could function as a ‘carbon-free material’ that doubles as a ‘computing device for a smart and growing architecture’. Not only could fungi help create buildings that self-heal, they could be the basis for responsive, digitally programmed buildings.
What is exciting about the material is that, unlike other biobased materials like wood or grasses, fungi-based construction appears to have no historical precedent. Buildings made from fungi would be a genuinely novel development in the history of design, one that could become the basis of new types of architecture and construction fit for the age of climate change.
Fungal construction materials range in their strength and permanence but perhaps the most radical implications come from the purely biobased fungal building block. The impermanence of structures built with these materials may usher in new attitudes towards the very purposes of buildings.
Today, our homes and public spaces are constructed to last generations. Yet in a climate age where natural disasters, economic shocks and migration could become the norm, the ephemeral building constructed from low energy organic materials like fungi could gain an upper hand.
