Surprising Building Materials

Cultivated Building Materials could close the Resource Gap

Like the previous events, also the last web seminar of the series “Building Materials of the Future” was very well attended – even the unusual late afternoon timing did not discourage participants to learn about new innovative building materials. The seminar was kicked off by Dr Dirk Hebel, professor for sustainable construction at the Karlsruhe Institute for Technology (KIT), who presented insights into cultivated building materials and mycelium in particular. The importance of cultivated building materials lies in the fact that they could help close the current resource gap. Looking at the much-needed transformation in the building sector, Hebel summarizes “we need to cultivate our building materials, because other approaches just won’t be sufficient”.

Hebel and his team first laid eyes on mycelium as building material when they met artist Philip Ross who started using mycelium in the 1990s as a medium for sculpture. Ross is the Co-Founder and CTO of MycoWorks, a company that grows biomaterials out of mycelium.

Mycelium – More than just a Fungus

Using mushrooms as a building material actually means using its large root system, where the hypha fuse together and form the mycelium. The mycelium then functions as a glue when mixed with a specific substance. After mixing mycelium tissue with a sterilized substrate, the fungus starts to digest the nutrients and transforms into a dense substance, which can then be cast into different moulds. The cast mycelium then further densifies into its final shape. In a last step, the resulting building element is being dried in order to stop the growth process which can last between 6 and 10 days in total.

As mycelium follows a metabolic cycle, building elements or even whole constructions can be composted after their original use. The material can be grown locally, reducing both the energy and time required for transportation. And, as they are organic matter, they act to reverse carbon emissions through the absorption of carbon. The disadvantages however lie in the mycelium's low strength, large tolerance in production and low durability to insect infestation and moisture.

Hebel also presented some ongoing experiments, he and his team are currently conducting. They are for example using mycelium as glue in OSB panels and have built an entire wall with it in a building in Indonesia to test its behaviour in a hostile climate. As another practical example Dr Hebel also introduced “Myco Tree”, a joint project of the KIT in Karlsruhe, the ETH Zürich and the Singapore ETH centre. Myco Tree is a spatial branching structure made of load-bearing mycelium components and bamboo. It was designed using 3D graphic statics, keeping the weak material in compression only.

Innovation in the Building Sector is Happening Now

Following this presentation, Diana Drewes from HAUTE INNOVATION, an agency for material and technology based in Berlin, demonstrated how much innovation is already taking place in the development of sustainable building materials. After pointing out that concrete needs to be replaced with other materials due to its high carbon footprint, she presented several companies that are already innovating in that area. To name just a few:

• KENOTEQ: a tech company that has developed an unfired brick with 90% recycled content from demolition and construction waste.
• Oxara, a spinoff of the ETH Zürich which developed a non-toxic mineral based chemical “cleancrete” – a cement-free concrete using clay as a binder and reducing CO2 emissions by 90% compared to conventional concrete
• CarbiCrete: which has introduced a technology to produce a cement-free, carbon-negative concrete using industrial by-products and captured CO2.
• BioMason: where CEO Ginger Krieg Dosier invented a bio cement consisting of 85% granite from recycled sources and 15% bio cement
• Solidian: a German manufacturer of non-corrosive reinforcement made of carbon, glass or basalt fibres.

Finally, Drewes also presented some of her own research where she grew fungi by herself and used mycelium to create an MDF like material.

Printing Sustainable Buildings of the Future

Dr Sascha Peters, the founder of HAUTE Innovation, followed Drewes presentation and added to her list of innovations. For example, he brought up a low energy concrete by ETH Zürich which is replacing cement clinker by fly ash and Miniwiz and Watershed Materials which is producing cement with rice husks ash. Peters also named already finished constructions, that show the previously mentioned building materials in use, like the SKAIO wood tower in Heilbronn, the highest wooden tower in 2019 and introduced Criaterra, a company creating eco-innovative materials by using a so- called Circular Earth Technology. Looking to future building technologies, Peters highlighted 3D printing which in his opinion could also contribute to the transformation into a more climate friendly building sector especially when it is combined with natural printing materials, as for example in the TECLA habitat in Italy.

Carbon Fiber Stone – The Successful Combination of Algae, Sunlight and Stone

Kolja Kuse from TechnoCarbonTechnologies, kicked off the last presentation of this web seminar by introducing “Carbon Fiber Stone”. This building material, which consists of carbon fibres and stone, can be produced carbon neutrally, as the fibers can be won from algae and carbonized by sunlight: in a first step algae oil is extracted from the algae and used to produce fibers, which are then carbonized by exposing them to sunlight under exclusion from oxygen. The sunlight is also used to produce electrical energy which can be used in the next productions steps where carbon fibers and stone, often granite, are combined. The now created building material can replace aluminium, steel, or concrete, and it can be separated into its components after use. In addition, granite has the same weight and modulus of elasticity as aluminium while at the same time having 4 times the pressure and tensile stability as concrete. Kuse also introduced the Green Carbon Project, which is funded by the European Union. The project deals with the practical demonstration of the material recycling of CO2 into bio-based carbon fibre composites and is searching for new ways of integrating lightweight materials to realise a climate-centred energy transition.

New Building Materials Are Needed – But will They Suffice?

The discussion taking place at the end of the web seminar once again proved that while there are many ideas to transform the building sector with the use of different building materials, both old and new, there is no easy solution to transforming the building sector. While some presenters strongly believe that there is no way around to replace existing building materials with the new ones presented in this web seminar, others represented the opinion that a co-existence of both current building materials like concrete and new ones like cultivated materials should be striven for, at least for now. In the end one thought concluded the entire web seminar series very nicely: alternative building materials, as well as the entire building process are being discussed and evaluated. This should be seen as a reason to think positively when looking to the future of the building sector. A lot of work still has to be done, but at least a start has been made.

*This web seminar was part of the natureplus project "Baustoffwende" and was funded by the Federal Environment Agency (UBA) and the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety.