Concrete is the second most commonly used material in the world. We need it to support bridges, buildings, courtyards, stairs, countertops, and more – and its use has been increasing and tripling over the past forty years.
Essential building materials include water, coarse aggregates, such as sand and gravel, and a binding agent – which is where cement, a particularly carbon-emission heavy product, comes from.
According to the International Energy Agency, the cement sector is the world’s third largest industrial energy consumer, consuming seven percent of industrial energy use. It is also the second largest industrial emitter of carbon dioxide, accounting for seven percent of global emissions. Most embrittlement occurs when raw materials, typically clay and limestone, are heated to more than 2500 degrees Fahrenheit to become super-strong binding materials. About 600 kg of carbon dioxide is released per ton of cement production.
But, sustainable, “green” cement is becoming increasingly popular, especially given the environmental footprint of conventional cement. A recent example emerged from the University of Tokyo last year, when researchers Kota Machida and Yuya Sakai made cement from food waste. Food waste has previously been used as a filler in cement substitutes, but Machida and Sakai developed the world’s first process for cement made entirely from food waste.
The two spent months mixing food waste with plastic so the ingredients would stick together. In the end, they found the right combination of temperature and pressure to make cement from just food waste without additives. Using a commonly used “heat pressing” strategy to make building materials from wood powder, they mixed the food waste powder with water and pressed it into a mold heated to 350 degrees Fahrenheit. Researchers say that the tensile strength or bending strength of cement is three times greater than the strength of ordinary concrete.
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“The most challenging part was that each type of food waste required different temperature and pressure levels,” Sakai said in a press release. They have used tea leaves, peels of oranges and onions, coffee grounds, Chinese cabbage and even leftovers from lunch boxes.
“Our ultimate hope is that this cement will replace plastics and cement products, which have poor environmental impacts,” Machida said in an interview with the AP earlier this month.
Engineers and researchers have been developing innovations to reduce the carbon footprint of cement and concrete for years. In 2021, scientists at the University of Tokyo created a concrete-making process that reuses old concrete products (which can often go to waste), heats the material at low temperatures, and removes carbon dioxide from the atmosphere. Is.
In 2019, researchers from the National Taipei University of Technology in Taiwan and the Department of Water Resources in India found that natural wastes from agriculture and aquaculture can partially replace the coarse materials and binding materials in green concrete. Many more options exist, and although these innovations are early in their development, they bring building materials closer to meeting low-carbon emissions targets.
But when it comes to using food-waste cement for buildings, Sohan Monae, a structural design engineer at multi-national infrastructure company Ferrovial, says that persuading companies to swap can be challenging.
“We have to make a lot of fundamental changes in our industry to completely change the way we use cement,” says Mone. How we set up, how we transport it, everything.”
That doesn’t mean it can’t be done or isn’t worth it, Monáe says. But one type of technology won’t fix all of the building industry’s issues.
One of Mone’s concerns is that cement manufacturers and construction companies must ensure that everything meets performance and safety standards. Most large infrastructure projects use concrete, which uses rebar-steel to reinforce cement. Cement itself acts like porcelain, without additional structural support. Ceramic objects such as sinks and toilets can handle compressive loads, but ceramic is not as strong as concrete.
“The second you apply a shear force, such as any tension or bending, [cement used on its own] shatters,” says Mone. “It’s not good to take stress.”
Therefore, using edible cement or cement substitutes in concrete for more complex and building-intensive purposes will require significant safety and durability testing, Monae says. And organizations regulating industry and contractors have to be convinced of its viability.
“We’re heavily regulated, right, and we’re not very free in terms of what content we can use,” Monae said. “The life cycle of these structures can be hundreds of years, and it is an open question how some of these things perform when exposed to the environment over time. There is always a fear of not knowing how something new will react.” And the concrete itself requires a lot of maintenance.”
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Green materials can also be expensive, which Monae says has a hard time convincing companies to use them. In large construction projects, it is more common to see developers choosing the most economical plan. But switching to green cement may be worth the cost, especially as concrete use rises as developing countries accelerate construction projects and other countries update aging infrastructure.
Global cement production could increase by up to 23 percent by 2050, the Mission Possible Partnership foresees in its Concrete Action for Climate Plan. Just as cement and concrete are shaping our built environment, so are their impacts shaping our climate future.
Meeting the Paris Agreement on climate change standards would require the cement industry to reduce its annual emissions by at least 16 percent by 2030. And because cement and concrete will be critical to future development, the researchers argue that creating material inputs for cement will be one of the fastest ways to reduce emissions and environmental impact.
“Given the urgency of the challenge and the time taken historically to develop technology systems, considerable thrust will be required to bring the next generation of low-carbon cement from the laboratory and to market. Not all will be successful, But those may have significant decarbonization potential,” the policy institute Chatham House wrote in its 2018 Making Concrete Change: Innovation in Low-Carbon Cement and Concrete report.
Growing cities and repairing infrastructure certainly won’t be slow anytime soon. But, with new developments in green building materials, the carbon impact of revitalizing the built environment may not be as overwhelming.