If concrete were a country, it would be the third-largest emitted of greenhouse gasses on Earth, trailing behind only China and the United States. New, innovative types of concrete and wood will could reduce carbon emissions by 70%, or even be Carbon negative. Dr. Winnie Tang explores the rise of new types of wood and cement, and how it can help reduce carbon emissions for a greener future.
“Cement is a major contributor to climate change,” says a report from the Royal Institute of International Affairs (RIIA). Also known as Chatham House, the British think-tank said that if concrete were a country, it would be the third-largest emitter of greenhouse gases on Earth, trailing behind only China and the United States.
About 1 kilogram of carbon dioxide (CO2) is released for every kilogram of cement produced. With over 4 gigatons (billions of tons) of cement produced annually in the world,, cement would account for around 8% of global emissions. Accompanying the global trend of urbanisation, carbon emission is expected to grow continuously in the next 30 years.
The Hong Kong government plans to reduce Hong Kong’s total CO2 emissions by 20% to 30% by 2030 using 2005 as the base. Can the construction industry try innovative technologies to help reduce carbon emissions?
In 2018, the government allocated HK$1 billion to set up the Construction Innovation and Technology Fund to encourage the industry to adopt new technologies. In the past three years, about half of the funding, that is, more than HK$500 million has been approved. This year’s Budget injects another HK$1.2 billion for its ongoing operation and enhancement measures.
Research from universities have found many low-carbon cement options that industries can consider.
For example, eco-friendly cement developed by Rutgers University in the United States is produced using a low-temperature chemical process as explored in my previous article. It uses more clay and less lime and does not need to be heated to 1,000 °C as with traditional methods, and can also lock CO2 within the concrete, thereby reducing carbon emissions by 70%. The Solida Technologies, a startup founded by a professor and student from Rutgers, is going to cooperate with a Swiss giant in the building materials industry to launch the eco-friendly product in the European and American markets first.
Another startup, BioMason, from North Carolina, thinks out of the box and grows construction bricks and tiles with bacteria to replace traditional bricks of cement. The technology involves placing sand in moulds and injecting it with microorganisms to initiate a biological process similar to the one that creates coral. Finally, the bio-cement is mixed with the recovered granite to form the concrete. The Swedish clothing chain H&M is interested in the eco-friendly material is planning to use it for the renovation of its chain stores. In addition, the University of Colorado Boulder published a study in international material science journal Matter, describing the use of a photosynthetic microorganism called “cyanobacteria” to produce low-carbon cement. Under the right conditions, these green microbes have the ability to heal cracks and absorb harmful substances in the air, it is also fairly durable. All these options sound amazing!
On the other hand, some are transforming timber into a new generation of building material. In Norway, an 85-metre-tall 18-storey building called Mjøstårnet completed in 2019, is currently the tallest wooden building in the world. But the record may soon be broken by a building in Chicago which has collaborated with the University of Cambridge to design an 80-storey residential building using wood as the major building material. At the meeting of the American Association for the Advancement of Science last year, the University of Cambridge introduced a new type of wood: it contains a composite of different layers, each designed to meet the requirements of structural components such as floors, panels, cross-braces and beams. It is 80% lighter than steel but has the strength to compare – to top it off, the material is also fireproof!
In terms of carbon emission reduction, building a 300-square-metre four-storey building with this new type of wood only emits 126 tonnes of CO2, compared to the 310 tonnes emitted by concrete and 498 tonnes emitted by steel. Moreover, building with wooden boards might actually be viewed as “carbon negative”. When trees grow, they lock up carbon in their wood tissue, in this case, the equivalent of 540 tonnes of CO2. Therefore, it could be a new driving force for sustainable development.
Recently, Hong Kong also has had encouraging progress in building a greener future. At the 2022 Special Edition of the Geneva International Exhibition of Inventions, a local company EcoBricks Limited utilising plastic waste to produce concrete won a Gold Medal with Congratulations of the Jury.
The company’s processing of concrete has no emissions and no pollutants, yet its eco-friendly products are strong enough and up to international standards.
I hope the award-winning products can give our local construction industry more confidence in adopting new materials so that the industry can take a bolder step toward a sustainable future.