SINGAPORE - A house or building made of mushrooms may sound far-fetched and fragile, but do not underestimate the strength of the mycelium, a hardy component of the fungi.

Researchers in Singapore and Switzerland are now studying the use of mycelium as a sustainable building construction material.

Mycelium is the vast underground root network of fungi.

The mushroom one sees is merely the fruiting body, making up just a small part of the fungus. This means the bulk of a fungus grows underground.

In a 2019 documentary titled Fantastic Fungi, it was reported that there are 480km of mycelium under every footstep one takes in the forest.

When cultured in the lab, a mass of mycelium looks like white fluff.

Although delicate-looking, this "fluff" is being turned into "mushroom bricks" for construction as part of a research project.

The branching threads are made of substances such as chitin and cellulose that are known to be strong, said Assistant Professor Hortense Le Ferrand, a co-investigator in the project under the Future Cities Lab (FCL) Global programme.

The programme was launched late last year at the Singapore-ETH Centre - a collaborative research centre between Singapore institutions and Swiss university ETH Zurich.

The research on using mycelium for building construction is one of eight projects in the programme focusing on enhancing the sustainability of cities and human settlements.

Buildings and construction generate about 40 per cent of planet-warming carbon dioxide, according to the 2019 Global Status Report for Buildings and Construction. A quarter of the emissions came from manufacturing building materials and products such as glass, cement and steel.

Between 2016 and 2019, construction and demolition generated the largest amount of waste in Singapore - between 1.4 million and 1.6 million tonnes a year - although 99 per cent of the waste is recycled here. This is where mycelium comes in handy.

Mycelium cannot turn into an eco-friendly building block on its own. It needs plant-based waste or food waste such as sawdust, bamboo or coffee grounds as a medium.

When a fungus is grown on a bed of sawdust or corn stalks, the mycelium branches out and snakes through the fragments of waste, binding to them. It takes three to four weeks for the mycelium network to grow and bond with every fragment of waste. The mass is then cast into a mould to be shaped into a mushroom brick. Once the material has lived through its lifespan, it can be composted instead of filling up landfills.

The mushroom brick has been around for a few years, mainly showcased in installations. Now, the researchers want to optimise the use of mycelium for building construction.

Mycelium's growth depends on factors including the species of fungi, type of plant-based waste, temperature and humidity, said Prof Le Ferrand at a virtual presentation hosted by FCL Global earlier this month.

Different species of fungi produce mycelium with different qualities.

"Studying the amount of chitin and cellulose that fungi produce is one way to find out which species and growth conditions yield the strongest mycelium," said Prof Le Ferrand, who is a faculty member at Nanyang Technological University's School of Materials Science and Engineering.

Over the next five years, Prof Le Ferrand and her team will conduct studies to optimise the growth of mycelium and explore how 3D printing can be used to build a mycelium-based structure.

The project's team in ETH Zurich is improving on the mushroom brick's function and exploring suitable architectural applications.

Dr Juney Lee, a senior researcher at the Swiss institute and another co-investigator of the project, said at the presentation: "These alternative and sustainable materials tend to be much weaker than concrete or steel, so they require an intelligent geometry and structural shape."

Mushroom Bricks

Scientists from Singapore and Switzerland have recently embarked on a five-year research project to find out how a hardy component in fungi, known as mycelium, can be used in construction. Here are some details on the process.

What is mycelium?

Mycelium is the underground root network of a mushroom, with threads that are measured in kilometres.

Under an electron microscope, mycelium threads branch out to form an intricate, interconnected web. A mass of mycelium has more networks than the number of neural pathways in a brain.

Why is mycelium a promising construction material?

Mycelium is rich in substances such as cellulose and chitin which are known to be mechanically strong.

It is also re-resistant, lightweight, and absorbs sound.

When a fungus or mushroom grows on plant-based waste such as sawdust or corn stalks, the fast-growing mycelium threads will bind the loose waste materials together into a mass - forming the building blocks of a "mushroom brick".

How is mycelium sustainable?

Mycelium is organic and biodegradable - once a structure or furniture made of mycelium and agricultural waste has ended its lifespan, the material can be composted. This means the renewable building block can return to the earth instead of taking up space in landfills.

In addition, mycelium does not need to grow on soil. It can grow within agricultural waste such as used coffee grounds, leaves and bamboo fragments, including food waste. The threads also do not need to compete for land with food crops.

How does mycelium work?

As a fungus grows on the waste, the mycelium net gets thicker, and acts like a natural glue to fuse the loose materials together. Mycelium secretes proteins that allow the threads to bind with the fragments.

This process takes three to four weeks of growth for the web to hold everything together.

Factors affecting mycelium growth include the size and type of agricultural waste, temperature, humidity, amount of light and water, and species of fungus.

How do they become bricks?

The mycelium-based mass goes into a mould to be shaped into a building block to form the bricks. The bricks will then be heated or baked to stop the mycelium from continuing to grow.

How are mycelium bricks used?

Building materials made of mycelium or other sustainable materials are much weaker than conventional concrete or steel. Mushroom bricks are weak in tension. Therefore, structures made of mycelium-based blocks need intelligent, structural shapes to make them stable.