From breeding, cultivation, seeding and harvesting of future building materials

Prof. Dirk E. Hebel

Professorship of Sustainable Construction, Karlsruhe Institute of Technology
The world population has been growing steadily for decades. At the same time, economic prosperity is increasing in many countries of our planet with positive effects on education rates, poverty reduction and health care. However, with our current economic model, both developments also lead to increasing pressure on our natural environment, our climate and our resources.
Dirk Hebel
The vast majority of our materials used for construction are still extracted from the earth’s crust, used and then disposed of. They are literally consumed and used up and not borrowed from natural or technical cycles to be reabsorbed into them. This still dominant linear approach has profound consequences for our planet. We are seriously interfering with existing ecosystems, as evidenced by climate change, dying fauna and flora systems and dwindling natural material reserves. Sand, copper, zinc or helium will soon no longer be available from natural sources in a technically, ecologically and economically justifiable way.
Greenhouse gas emissions, material and energy consumption and waste generation

Future economic and environmental development is therefore strongly linked to where our resources for these come from. With our mines running dry and CO2 levels reaching alarming levels, we need to radically rethink all sectors of the economy. According to the latest European Union surveys, construction alone is responsible for 40% of our CO2 and other greenhouse gas emissions, 50% of primary energy consumption, 50% of primary raw material consumption and 36% of solid waste generation. In addition, 75% of Europe’s population already lives in urban areas, and the trend is upwards, with increasing specific living space requirements. It is therefore no coincidence that we are experiencing an incipient change in the mentality of our society, which sees its livelihoods threatened by climate change, resource scarcity and the littering of our environment.

Mehr.WERT.Pavillon, Heilbronn 2019
© Zooey Braun
Mehr.WERT.Pavillon, Heilbronn 2019 © Zooey Braun
The urban mine

Our built environment has a key role to play here. It must be seen as a repository and future resource provider, a new mine: the urban mine. Viewing this anthropogenic (man-made) repository as a temporary state aiming at an endless cycle of resources represents a radical paradigm shift for the building sector. The quantitative potential of the already existing urban mine as a material supplier is gigantic. The challenge is to develop new technologies to transform these materials into a new generation of qualitatively sustainable, i.e. ecologically non-harmful, technically pure and economically attractive – because endlessly recyclable – building materials. In this first step towards a circular-based construction industry, however, we still have to eliminate materials that do not meet these criteria – in the hope that we will soon be able to do so. These include a myriad of building materials which, as so-called composites, consist of several materials that can no longer be recovered by type. Groups of materials that are contaminated by synthetic adhesives, foams, coatings, paints or other treatments cannot yet be recycled without massive losses in quality. They are landfilled or incinerated, which in the end is tantamount to destroying resources.

We are seriously interfering with existing ecosystems, as evidenced by climate change, dying fauna and flora systems and dwindling natural material reserves.
Rethink the construction sector

However, new business fields are already developing today that break this principle for economic reasons. For example, there are companies that no longer sell their products, but only charge for their use, in order to return the material (which has been incorporated according to type) to the production process after use. In the process, the companies are developing new know-how and new technologies to ensure this. There is an enormous opportunity in this approach to ultimately rethink the construction sector completely and thus develop new business areas. Consequently, new construction principles have to be developed to make extraction technologically possible. Once this state of a truly circular construction industry has been achieved, so-called material passports must be created and linked to a digital cadastre system so that future generations will know where which materials will be available, in what quantity and when. However, we will not be able to meet the demand for resources from urban mining alone due to the technologies that do not yet exist to transform materials 100%. We need to increasingly fill this gap with a shift towards regenerative cultivation, breeding and cultivation of future building materials instead of continuing to rely on finite fossil, mineral and metal deposits.

MycoTree, FUTURIUM Berlin 2019
© Carlina Teteris
MycoTree, FUTURIUM Berlin 2019 © Carlina Teteris
Filling the gap sustainably

While the first industrial revolution led to an increased shift from regenerative (biological) to non-regenerative material sources (metallic and mineral) in the building sector, a new revolution may be just around the corner, bringing biological aspects back into an otherwise mechanised industrialised world. According to Klaus Schwab, founder and CEO of the World Economic Forum, this would be characterised by a fusion of technologies that blur the boundaries between physical, digital and biological spheres. The concept of industrialised construction within and respecting undisturbed natural cycles does not promote a regression to the pre-industrial age; it seeks to describe ways to progress within the given economic environment in order to modify and ultimately reinvent it. This also applies to the social conditions of production and the cultural acceptance of new materials and construction methods. The introduction of biologically controlled and digitally supported production processes could and must enable economic areas in less industrialised areas of our planet to participate in this revolution.

We will not be able to meet the demand for resources from urban mining alone due to the technologies that do not yet exist to transform materials 100%. We need to increasingly fill this gap with a shift towards regenerative cultivation, breeding and cultivation of future building materials.
Biological building materials

Some of the organic matter that could be transformed into building materials has, interestingly, so far been classified as undesirable or as repulsive in the construction industry. While the pharmaceutical industry, for example, has used bacteria with undisputed success, architecture and construction have not yet activated such capacities. However, bacteria can be used very successfully to make mineral building materials and buildings selfhealing and thus more durable, by using the property of certain bacteria to produce biominerals. Several research groups worldwide are also working on the question of whether this property could replace classic cement and thus revolutionise the concrete industry. The same applies to fungal mycelium. In the construction industry, fungi are associated as undesirable and even dangerous organisms. Yet there are species from which building materials can be grown. Here, the root system of the fungal organism, the so-called mycelium, acts as a cross-linking matrix (glue) of biological waste products, such as rice husks, grain stalks, husks or kernels. Depending on these aggregates, on the type of fungus and on the growth conditions, amazing building products can be obtained here, from insulation materials to new types of building boards. Bamboo, another material that has been used for centuries as a reliable resource for building, has also never reached the level of a successful industrialised building product, as it has always been trapped in the “traditional” drawer. As a new industrially-cultivated building material, however, bamboo’s potential lies in its extremely tensile fibre, which can easily rival today’s metallic building materials. The same applies to flax or hemp fibres. The extraction and industrial reconfiguration of these natural fibres opens up new possibilities in the creation of high-strength biological building materials and components. Added to this is the enormous scope for design offered by digital fabrication.

© Carlina Teteris
Bamboo © Carlina Teteris
A self-generating economy

In both cases, the conquest of the urban mine and the cultivation of new types of building materials, the cycles must be played with in a purely sorting manner. Here lie enormous opportunities for the construction industry to reinvent itself and establish new business areas. At the same time, the energy to serve these cycles must be obtained from regenerative sources in order to fulfil the overarching social mandate of a life-sustaining and self-regenerating economy.

Further information about the author

Prof. Dirk E. Hebel
Professor of Sustainable Construction and Dean of the Faculty of Architecture, KIT Karlsruhe