Concrete is the second-most used material in the world. We need it to support bridges, buildings, patios, staircases, countertops, and more—and its use has been growing and tripling in the past forty years. 

The essential building material comprises water, coarse aggregates, like sand and gravel, and a binding agent—which is where cement, an especially carbon emissions heavy product, comes in. 

According to the International Energy Agency, the cement sector is the third-largest industrial energy consumer in the world, consuming seven percent of industrial energy use. It is also the second-largest industrial emitter of carbon dioxide, responsible for seven percent of global emissions. Most emissions occur when raw materials, typically clay and limestone, are heated to more than 2500 degrees Fahrenheit to become the super-strong binding material. Roughly 600 kilograms of carbon dioxide are released per ton of cement produced. 

But, sustainable, “green” cement is becoming increasingly popular, especially considering the environmental footprint of traditional cement. A recent example came out of the University of Tokyo last year, when researchers Kota Machida and Yuya Sakai made cement out of food waste. Food waste has been used as a filler in cement alternatives before, but Machida and Sakai developed the world’s first process for cement made entirely from food waste.

The duo spent months mixing food waste with plastic to get the materials to stick together. Finally, they found the right combination of temperature and pressure to make cement from just the food waste without additives. Using a “heat pressing” strategy typically used to make construction material from wood powder, they mixed the food waste powder with water and pressed it in a mold heated to 350 degrees Fahrenheit. The researchers say the tensile or bending strength of the cement is more than three times the strength of ordinary concrete. 

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