Spotlight on Sustainability

Biomaterials and Their Place in the Construction Industry

todayMarch 23, 2022

Background

The term biomaterials is used to describe building materials derived from living organisms including plants, animals and fungi. Increasing knowledge about microbiology and synthetic biology techniques is now allowing innovative biomaterials to enter the market.

With the construction industry responsible for 40% of global CO2 emissions, responsibility falls on the industry to make dramatic changes to improve its sustainability. New biomaterials are being created using waste products and microbes to solve these ecological problems, with timber or plant-based materials being net carbon sinks. The biomaterials that are being explored for use in the construction industry are diverse and varied, each aiming to solve a different problem within the industry.

Biomaterials have the potential to provide construction materials with the following benefits:

  • Capture and storage of carbon extracted from atmospheric CO2 by recent photosynthesis
  • Sustainable production as crops grown annually or as longer harvest-cycle forest.
  • Biodegradability at end of life. (Controlled decay inside an anaerobic digester would produce both organic fertiliser and bio-methane to supply energy)
  • Low or almost zero linear coefficients of thermal expansion
  • The property of controlling temperature and humidity in enclosed spaces by phase changes of water in cells
  • High vapour diffusivity and ‘Fickian’ vapour dispersal
  • Usually high specific heat capacity
  • Low thermal diffusivity
  • Often good performance-to-weight ratios
  • Lower embodied energy. 

Concrete – Are there better options?

Arguably the most commonly used material in the construction industry is also one of the most unsustainable. Concrete, serving as the backbone of most infrastructure, produces staggering amounts of carbon. It is estimated that around 10 billion tons of concrete is produced every year, with cement (a main element in mixing concrete), accounting for 8% of the annual carbon emissions around the world, and using around 10% of global drinking water, according to Dosier.

While concrete and cement are not sustainable materials, the construction industry is not going to stop using it over night. To address this fact, there are many companies who are designing and producing alternatives to traditional Portland-based cement, in an attempt to reduce its impact on the environment.

One such company is Basilisk, who are in the process of bringing “repairable concrete” to the market by embedding special limestone-producing bacteria into concrete. When the bacteria comes into contact with water, such as when moisture enters a crack, the spores are activated, leading to a growth of the micro organisms. The bacterial spores are hardy extremophiles, able to endure heat, drought and cold for years inside the concrete.

Image curtesy of biomason.com

By extending the lifespan of concrete, Basilisk can reduce the overall amount of concrete used thus making the material more sustainable. Despite the higher initial cost of self-healing concrete, Green Basilisk is working to convince the industry that the long-term savings in maintenance are well worth the expense.

“We can reduce shrinkage reinforcements by up to 50%. That would mean if we just add five kilos of Basilisk into the concrete mix we can save up to 30 kilos of fuel per cubic meter,” said Marc Brants, marketing and accounts manager at the firm. 

Another company is Biomason, a US-based company that grows cement through a biological process with a low carbon footprint. Their biocement technology grows in ambient temperatures, building with carbon and calcium to create controlled, structural cement. Where Portland cement is a calcium-silicate hydrate material that originally comes from liberating carbon from limestone through intensive heating, emitting carbon dioxide as a byproduct. The Biomason “Biocement” is a reversal of this process, where carbon and calcium are combined to produce a biologically formed limestone material. This means that high heat and fossil fuels are not required in their process, and their materials use carbon as a building block.

Mycelium

Mycelium forms part of the root structure of mushrooms and is also being explored in a number of ways for use in the construction sector.

Biohm, a UK based company, is currently developing a mycelium-based insulation panel. A key advantage of mycelium is that it can be grown on waste agricultural products and is biodegradable. It also contains chitin, which is a natural fire retardant.

“What we’re looking at is building on this idea of circularity … if we were to take the material back, we could break it down and then put it back into the growth process when we grow the mycelium pane. This is something that we’re experimenting with as well.”

London practice Blast Studio has developed a method for 3D printing with living mycelium and used it to form a column that could be harvested for mushrooms before serving as a structural building element. The column was constructed by mixing mycelium with a feedstock of waste coffee cups collected from around London and feeding it into a custom-made cold extruder, similar to the kind used for 3D printing with clay. Blast Studio is working to scale up the technology to print a pavilion and in the future, it hopes to construct entire buildings. Co-founder Paola Garnousset said this could effectively allow cities to grow architecture from their own waste while providing food for their inhabitants.

Hemp

Darshil Shah, who featured on Episode 15 of the Constructive Voices podcast, works with hemp as a biomaterial. Hemp can capture atmospheric carbon twice as effectively as forests while providing carbon-negative biomaterials, with numerous studies estimating that hemp is one of the best CO2-to-biomass converters. Industrial hemp absorbs between 8 to 15 tonnes of CO2 per hectare of cultivation. The fast-growing plant has been grown for thousands of years for its fibres, which were traditionally used for rope, textiles and paper. Today it is increasingly being used to make bioplastics, construction materials and biofuels.

In an interview with Dezeen, Shah says:

“The strong, stiff fibres that form the outside of the stem can be used to produce bioplastic products including automotive parts and even wind-turbine blades and cladding panels”

Darshil Shah

“With the hemp bioplastic cladding panels, we find that they are a suitable alternative to aluminium, bitumen-plastic and galvanised steel panels, requiring only 15 to 60 per cent of the energy in its production.” The shives, which are the woody inner part of the stem, can be used to make “hempcrete”, a non-load-bearing wall infill and insulation material.

Hemp is also being investigated as a construction material at the Rensselaer Polytechnic Institute in the US, where they have invented an alternative to steel rebar made using hemp. Not only will it reduce the amount of carbon emissions, they claim it will avoid the problem of corrosion.

Steel is subject to corrosion and rusting, particularly in structures such as bridges, roads, seawalls and buildings and areas with in environments with high salt concentration, which significantly reduces its lifespan. In highly corrosive environments, lass fibre reinforced polymer (GFRP) rebar are often used instead, which has a high environmental impact.

If there corrosion was no longer a factor, the team at Rensselaer Polytechnic Institute believe that the lifespan on the rebars would be three times more than it is now. This increase in service life will therefore reduce the carbon emissions even further.

While their hemp rebar is a viable alternative to existing products now, they expect the technology to become even more efficient in the future as extraction processes are refined and plants bred for their fibre.

Although there has been interest in developing new biomaterials for building for some time, the building industry is conservative and heavily price-driven, meaning acceptance has been slow. However, the increasing consumer demand for sustainability has heightened interest in these innovations, resulting in a more competitive environment for building materials. Learn more about innovations and practices within this topic with sustainability training here.

Which of these materials are you going to start using in your projects?

 

 

Written by: Tara Flanagan


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