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Green construction: sustainable alternatives to cement

By Anais Descleves - 30 April 2022

Awareness of the climate crisis has increased greatly. As the war against plastic is already firmly on, another greater polluter needs to be tackled: cement. Legislation and technological development are pushing towards greater sustainability, and therefore, helping a variety of green alternatives to cement arise. This article analyses some of these alternatives, with their pros and cons.

Why are alternatives to cement important

Concrete production today is a bigger environmental issue than plastic. According to The Guardian, taking in all stages of production, concrete is responsible for 4% to 8% of the world’s CO2. Producing cement is a heat-intensive process that releases a large amount of carbon dioxide. Transportation and extraction of the raw materials used in cement also contribute to the emission of CO2 at a high rate.

Dangerous for human health

Concrete can be very dangerous for public health. It can cause illnesses, some of which are disabling for workers, such as:

  • Skin irritation from fresh concrete leading to burns, dry skin or cracks
  • Ocular irritation
  • Respiratory pathologies due to inhalation of dry concrete and dust

Dangerous for the environment

Moreover, this material is also dangerous to the environment. Concrete causes damage to the most fertile layer of the earth, the topsoil. It also creates hard surfaces, therefore, contributing to surface runoff. This can lead to water pollution, flooding and soil erosion.

Water is one of the four basic components of concrete, along with sand, aggregates and cement. Concrete absorbs around one-tenth of the water used in the world’s industry. The large amount of water required to make concrete can accelerate drought in areas with very little humidity.

Sand is a common ingredient of concrete too. However, sand resources are becoming increasingly scarce. Because of the growing number of real estate and construction projects, it is now difficult to extract sand from the ground in many countries. The solution has been to get it from the ocean, as close to the coast as possible, but this is resulting in beach degradation. You may think the answer lies in the Sahara. Unfortunately, it is not possible to use desert sand because, as they are polished by the wind, grains have a rounded and regular shape which prevents sufficient aggregation.

With a lack of suitable sand, finding alternatives to traditional concrete is not only a positive move for the planet but a necessity for the future of the construction industry.

Recycling-based construction materials

More than ever, it is necessary to think differently about the life cycle of materials to avoid pollution and waste. The circular economy thus represents a response to the environmental challenge that has intensified over the last twenty years.

Circular economy

As the United Nations defines it, the circular economy is “a system of production, exchange and sharing that enables social progress, preservation of natural capital and economic development”. Resources are not infinite, and it is becoming urgent to preserve them.

The transition towards a circular economy aims to go beyond the linear economic model of extracting, manufacturing, consuming and throwing away. It calls for responsible consumption of natural resources and primary raw materials. It should prevent waste by reusing, recycling, or recovering of waste.

A wall constructed with recycled plastic.

Alternatives to cement from startups

European Union Legislation now requires 70% of all construction and demolition waste to be recycled. It is creating opportunities for startups leveraging construction waste to create concrete alternatives.

For example, the French-based startup Materrup has begun marketing its non-calcined clay cement. It should replace traditional cement in the composition of concrete. This solution would reduce carbon footprint. Using clay is also a way to make the most out of an abundant resource that is present everywhere.

Another example of a European startup creating alternatives is Kenoteq. It is a cleantech spin-out company, specialising in the development and delivery of highly sustainable building products based on a closed-loop and circular economy.

Steel by-products

Steel by-products can also be recycled as aggregate for concrete. Early Metrics rated a startup called CarbiCrete, using steel slag to make net carbon-negative concrete. Iron Shell, another startup, created the material known as Ferrock from waste steel dust. It is five times stronger and more flexible than cement. Moreover, it is far more resistant and sustainable, making it a promising substitute to cement.

Ashcrete, which uses ash from coal production to create a sustainable aggregate for concrete, also fits in the circular economy. It is a sustainable substitute for traditional concrete that relies on the use of fly ash (a waste byproduct produced in the combustion of coal).

Recycled Plastic

Recycled plastic is a material that is part of the sustainable building movement. It can be used for roofing, flooring, and insulation. Numerous startups have emerged using this kind of solution such as ByFusion, Arglite and Gjence Makers.

Using recycled plastic instead of traditional cement might seem like hitting two birds with one stone, as it could tackle both polluters. However, every piece of recycled plastic is a potential threat to the environment. The process of melting and recycling plastic produces volatile organic compounds that can harm plants and animals near the industrial site. Therefore, it also generates carbon emissions, which contributes to global warming.

Food waste

Next step in the recycling-based construction material sector would be the reuse of food waste to produce bio-plastics. It would be suitable for creating materials like Chips Board which is dedicated to developing bio-plastic composites made from industrial byproduct. It performs the same as conventional plastics whilst being biodegradable and recyclable post-use.

Plant-based alternatives to cement

Going back to timber and plant-based construction might seem like a step back to traditional building practices as well as participating to deforestation. But technology and research have meant some plants can now constitute safe and renewable alternatives to cement. It is possible to substitute aggregates with plants like Miscanthus shreds and others mentioned below.

Hempcrete is an alternative to cement which uses hemp, forming a renewable and strong plant-based material for construction.

Hemp

Choosing strong and fast-growing plants such as bamboo and hemp can prevent deforestation and ensure more lager scale supply. Hemp is indeed used in hempcrete, a bio-composite material. This plant is efficient at absorbing CO2 while growing, retaining the carbon and releasing oxygen. It is, therefore, a non-toxic building material that remove carbon from the air.

Bamboo

Bamboo is also a very attractive material. It is environmentally friendly and, above all, it is extremely strong and resistant. That’s why it has been used for many years, especially in Asia. Bamboo is a plant that grows at a very high speed, up to one meter per day, making it very profitable and reliable. It also reduces the amount of carbon dioxide in the air and diffuses more oxygen into the atmosphere. Therefore, bamboo is a very promising renewable raw material, as shown in the Research project Bamboo Europe that was launched recently. This research aims to show that bamboo can be used in construction to create a transparent, sustainable and local supply chain.

Startups like Widuz and Rizome have developed a new class of renewable and sustainable construction materials out of bamboo, with the hope of revolutionising the building industry.

Timber

Other startups are also developing innovative ways of using timber like timbercrete. Also known as woodcrete, it replaces typical aggregate with cellulose (i.e. wood pulp). The main advantage is these bio-based materials are renewable and supply chains for responsibly sourced wood pulp are already in place in many countries. Secondly, the carbon footprint of timbercrete is negative. Finally, using timber innovatively ensures buildings are well insulated in terms of heat and sound.

Unconventional materials to replace cement

The materials mentioned so far have a lot of potential, but they might not have seemed all that surprising. Let’s look at some more peculiar raw materials that could make our construction practices greener.

Mycelium bricks made from mushrooms represent one of the many surprising materials that could replace cement in future.

Fungi

Although fungi-based construction materials are in their early stage, they have the potential to become a viable, sustainable alternative to concrete. As shown by the EU commission’s article, mycelium, the vegetative part of a fungus, is a natural binder. Mycelium is a residual product of the cultivation of mushrooms. It could be integrated into concrete and therefore, we would be able to “grow buildings” from agricultural residues – materials that are inexpensive, sustainable, and biodegradable.

The mycelium composite is light and strong. Moreover, it contains air, which gives it excellent properties for construction or insulation. Our future homes could have living walls.

Innovative architecture techniques

Famous architects have also shown the potential of seemingly unreliable materials such as David Easton who revived rammed earth, a mixture of sand, loam, clay, and moisture to create massive solid mud walls. He advocated for and experimented with earth as a building material.  

Shigeru Ban is another architect famous for his creative mind. He created some innovative structures made of paper or cardboard tubes. With those constructions, he was able to build temporary prefabricated habitats for populations deprived of housing following disasters.

It is, therefore, necessary to think out of the box to generate sustainable alternatives to cement.

As demonstrated above, there are many viable candidates to reduce the impact of construction on the climate and the environment. The issue cannot be reduced to the choice of materials alone. It requires a transformation in the way we think, build and transform our living and working spaces. The link between startup innovation and ESG improvements is becoming clearer for incumbents in all industries. That is why EM supports large players in finding startup partners that can help them build a more sustainable future.

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