Concrete is the world's second-most-used material. It's used to support bridges, buildings, patios, staircases, worktops, and more, and its use has tripled in the last four decades.
Water, coarse aggregates such as sand and gravel, and a binding agent—which is where cement, a particularly carbon-intensive product, comes in—make up the basic construction ingredient.
According to the International Energy Agency, the cement industry is the world's third-largest industrial energy user, accounting for 7% of total industrial energy consumption. It is also the world's second-largest industrial carbon dioxide emitter, accounting for 7% of worldwide emissions. When raw materials, such as clay and limestone, are heated to above 2500 degrees Fahrenheit to form the super-strong binding material, the majority of emissions occur. Per ton of cement produced, around 600 kilos of carbon dioxide are emitted.
However, given the environmental impact of regular cement, sustainable, "green" cement is becoming increasingly popular. Last year, researchers at the University of Tokyo, Kota Machida and Yuya Sakai, developed a cement manufactured from food waste. Although food waste has previously been utilized as a filler in cement substitutes, Machida and Sakai created the world's first technology for cement manufactured completely of food waste.
To get the components to cling together, the team spent months combining food waste with plastic. Finally, they discovered the optimal temperature and pressure for producing cement only from food waste without the need of additives. They combined the food waste powder with water and crushed it in a mold heated to 350 degrees Fahrenheit, using a "heat pressing" approach similar to that used to manufacture construction material from wood powder. The tensile or bending strength of the cement, according to the researchers, is more than three times that of standard concrete.
“The most challenging part was that each type of food waste requires different temperatures and pressure levels,” Sakai said in a statement. Tea leaves, orange and onion peels, coffee grounds, Chinese cabbage, and even lunch box leftovers have all been employed.
“Our ultimate hope is that this cement replaces plastic and cement products, which have worse environmental impacts,” stated Machida in an interview with the AP earlier this month.
Engineers and researchers have been working on ways to lower the carbon footprint of cement and concrete for years. In 2021, University of Tokyo scientists developed a concrete-making method that reuses existing concrete products (which are generally thrown away), warms materials at lower temperatures, and collects carbon dioxide from the environment.
Natural wastes from agriculture and aquaculture farms might partially replace coarse materials and binding elements in green concrete, according to researchers from Taiwan's National Taipei University of Technology and India's Water Resources Department. There are plenty of other options, and while these technologies are still in the early stages of research, they bring building materials closer to fulfilling carbon reduction objectives.
However, Sohan Mone, a structural design engineer at multi-national infrastructure giant Ferrovial, believes it will be difficult to persuade businesses to switch to food waste cement for use in buildings.
“To change how we use cement entirely would require a lot of fundamental changes in our industry,” Mone adds. “All of the infrastructure is geared towards how cement currently works, from how we install it to how we transport it, everything.”
That isn't to suggest it can't be done or isn't worthwhile, as Mone points out. However, one form of technology will not solve all of the problems in the construction business.
Cement makers and building businesses, for example, must guarantee that everything fulfills performance and safety criteria, according to Mone. The majority of large infrastructure projects are made of concrete, which is reinforced with rebar (steel). Without extra structural support, cement behaves like porcelain. Sinks and toilets made of ceramic may withstand compressive stresses, although they are not as sturdy as concrete.
“The second you apply a shearing force, like any tension or bending, [cement used on its own] shatters,” Mone explains. “It’s not good at taking tension.” Using food cement or cement substitutes in concrete for more complex and building-intensive uses, according to Mone, would need extensive safety and durability testing. The industry's regulators, as well as the contractors themselves, would have to be convinced of its feasibility.
“We’re heavily regulated, rightly so, and we’re not very free in terms of what materials we can use,” Mone said. “The life cycle of these structures can be hundreds of years, and it’s an open question about how some of these things perform when exposed to the environment over time. There’s always that fear of not knowing how something new will react. And concrete itself needs a lot of maintenance.”
Green products can be costly, which adds to the problem of persuading businesses to employ them, according to Mone. When it comes to large building projects, it's more customary for developers to select the most cost-effective option. However, converting to green cement may be worthwhile, especially as the consumption of concrete rises as emerging nations speed up construction projects and developed ones upgrade aged infrastructure.
According to the Mission Possible Partnership's Concrete Action for Climate proposal, global cement output might grow by as much as 23% by 2050. Cement and concrete have an impact on our built environment, and their effects have an impact on our climatic future.
To satisfy the Paris Agreement's climate change requirements, the cement sector will need to reduce yearly emissions by at least 16 percent by 2030. Because cement and concrete will be so important in the future, experts believe that making the material inputs for cement will be one of the most efficient methods to minimize emissions and environmental effect.
“Given the urgency of the challenge and the time taken historically for technology systems to evolve, a considerable push will be needed to get the next generation of low-carbon cements out of the lab and into the market. Not all will succeed, but those that do could have significant decarbonization potential,” according to Chatham House's Making Concrete Change: Innovation in Low-carbon Cement and Concrete study from 2018.
The pace of urbanization and infrastructure restoration isn't going to slow down anytime soon. However, because to recent advances in cleaner building materials, the carbon footprint of rejuvenating the built environment does not have to be as high.
Reviewed by Lilit
on
June 16, 2022
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