As global temperatures rise, the need to scale climate adaptation technologies is becoming increasingly urgent.
Net temperature-related deaths could increase by 50 percent by the end of this century. Materials that cool our homes without damaging the environment are increasingly sought after as record-breaking temperatures become more frequent.
Although cutting emissions to prevent further global heating is our biggest priority, we also need to change the way we cope with volatile weather.
Certain biomaterials can form the basis of sustainable passive cooling systems. Unlike air conditioning, passive cooling is a lower-energy way of combating extreme heat. Biobased passive cooling tech does one better by safely biodegrading at the end of their product life.
Researchers are developing new biomaterials for climate-ready building design that protects inhabitants and cuts down energy use.
Elephants and fungi for cooler buildings
How do animals that live in the heat cool down? And how can humans borrow from them to improve their built environment? These were the questions driving research conducted by scientists from Nanyang Technology University in Singapore, who have developed cooling biobased tiles based on the texture of elephant skin.
The tile material itself is made from mycelium, the root systems of fungi. A network of fibrous, thin roots holds together bamboo shavings and other organic waste, creating blocks of firm material that can be cut to size easily.
The biomaterial’s cooling properties come from two components. First are the mycelium roots themselves. Mycelium composite materials are already renowned for their insulating properties.
The bumpy texture of the material is another component of the tile’s cooling capacities. The surface of the fungal tiles takes inspiration from the evolutionary adaptations of elephant skin, which scientists know help them live in scorching environments.
The cracks and wrinkles on an elephant skin’s surface help to cool down the animal. They increase skin surface area which means that more moisture is always evaporating from their bodies.
The test results showed promise. The elephant skin-inspired tiles showed a 25% greater cooling rate than flat ones.
The advantage grew to 70% when exposed to simulated rain. Just like in living elephant skin, the folds in the textures trap lots of rainwater, increasing the volume of water that evaporates and therefore cools the surface.
Already, scientists are moving towards commercialisation by working with Singapore start-up Mykilio to scale their idea and test it in the real world.
Traditional architecture, but biobased
Elsewhere too, researchers are exploiting mycelium as a biodegradable construction material for a warmer world.
In 2023, a study led by Kumar Biswajt Debath at the University of Technology Sydney developed a perforated screen made of mycelium designed to reduce indoor temperature and energy demand during extreme heat events.
The team called their device a ‘bio-jaali’. A jaali is an ornamental lattice common in Indo-Islamic and Indian architecture. The traditional jaali lattice was made from sandstone. Its many openings were designed to cool the air coming into a building.
The team aimed to redesign this functional architectural feature with biobased materials instead.
Their bio-jaali is made from mycelium roots grown around sawdust, wheat, or rice straw. In fact, any agricultural product can function as the filler material inside mycelium construction blocks, including agricultural byproducts.
An ideal candidate for local and circular filler material would be the agricultural ‘stubble’ left in fields after harvest.
This leftover material is a huge pollution hazard in India, where farmers burn the residue, a practice that causes severe air pollution during harvest time. Uses for the material in construction could make it pay for farmers to pick and sell the material rather than burn it.
Turning down the air con
These mycelium materials are examples of biobased ‘passive cooling’, a term that refers to design choices that reduce heat gain and increase heat loss without relying on energy-intensive ‘active cooling systems’ like air conditioning.
Examples of simple passive cooling in buildings are adding shade with trees, adding ventilation, and incorporating highly insulating elements to design.
Passive cooling systems are an important tool for both adapting to climate change and mitigating it. Active cooling systems such as air conditioning and electric fans are extremely energy intensive and contribute a lot to global warming.
Reducing their use as much as possible is key to moving towards more sustainable economies. Globally, the cooling industry accounts for 10 percent of emissions – more than aviation and shipping combined.
Cooling functions account for nearly a fifth of all building electricity. It is the fastest growing use of building energy globally and is set to triple by 2050.
Demand growth is especially skyrocketing in hotter developing countries as incomes and living standards rise, allowing citizens to more easily afford expensive goods like electronic cooling tech.
The extra energy demand required to fuel air conditioning makes it difficult for countries to move away from fossil fuel.
To cut electricity demand for space cooling, the International Energy Agency recommends government policy that mandates building designs that help maintain a comfortable temperature. Biomaterials could be a vital part of the push to design cooling properties into buildings from the get go.
Camel-inspired food packaging
Like air con, refrigeration is one of the most consequential modern technologies. It has radically reshaped the global food system, supply chains, and our eating habits.
Yet similar to air con, refrigeration tech has a huge environmental impact. Packaging materials that keep its contents cold for longer can help reduce demand for energy-hungry cooling processes.
Scientists at MIT have taken inspiration from camel hair to produce an insulating material that can cool its contents without a power source. It offers a low-energy way to transport temperature-sensitive goods like pharmaceuticals, for example.
Camel hair keeps animals cool in desert environments by allowing just enough sweat to evaporate to keep the skin cool while minimising moisture loss from the body.
The MIT material takes this lesson and recreates it using two layers of soft biomaterials. First, a hydrogel bottom layer holds a reservoir of water. Above, a layer of aerogel acts like camel fur, allowing some of the water beneath to evaporate and cool but trapping most of it and reserving it for later.
The system could be used to package food and medicine to prevent spoilage and loss through essential supply chains. While storage and transport trucks for these goods are refrigerated, the time taken up by loading and unloading can lead to spikes in temperature that affect product durability.
It could also preserve food for longer in a way that does not require an active power system – something that could help farmers and food distributors in hot countries.
The aerogel the researchers developed was made from silica. However, the two gel layers could be made from biological materials.
Nano-scale cooling films
Films and coatings that can be applied over large surfaces are an efficient way to make a building less prone to overheating – useful in retrofitting structures that were not initially built with heat protection in mind.
A biobased building can have many cooling elements. Using various biological feedstocks and biomaterials, we can increase its resistance to overheating one element at a time.
Windows are an important point of intervention for a passive cooling system. They are where light and heat most easily enters the building.
At Finnish R&S research and development organisation VTT, a team has developed a passive cooling nanomaterial from a very abundant biological material called cellulose.
Their new biobased nanomaterial adapts to environmental change, cooling when the temperature rises and trapping heat when it drops.
The material is a film made of plant-based nanocellulose for windows doped with particles whose optical properties shift with the environmental temperature.
In addition, it applies a thin reflective coating on one side of the film so it acts as a mirror that reflects bright sunlight in hot weather, preventing the room within from heating up as quickly as it would without the film application.
The team claims that in lab tests, their nano-coating achieved cooling by around 5 degrees celsius.
Many researchers are now trying to develop scalable layers that can be applied all over the buildings to cut energy demand for cooling quickly.
Biobased materials are most desirable from a sustainability perspective – most coating materials today are made from synthetic materials that are environmentally toxic and do not break down in nature safely.
Work done by material scientists at Stockholm University on biobased nanoparticles indicate that powerful heat-regulating materials do not need to rely on synthetic chemicals to work.
Their fully biobased coatings are partly made of lignin, a material found throughout the plant world. Lignin nanoparticles are embedded in chitosan, another highly abundant material found in shells of sea creatures, to form a material that blocks UV light.
Work like this shows how powerful renewable materials can be against heat, particularly when exploited at a nano-metre scale. Under their simulation, the coating led to a 58 percent reduction in temperature increase compared with uncoated glass.
The biggest human challenge of this century will be climate adaptation. Biobased cooling materials show the role that biological feedstocks will have in adapting to a warming world.
