Building a Better World With Green Cement
âYou know, cement is everywhere,ââNikolaos Vlasopoulos, an environmental engineer at Imperial College in London, says while sitting in a brightly lit college conference room in a hulking seven-story building held up by the topic of conversation. âItâs all around us.â
Last year, the world produced 3.6 billion tons of cementâthe mineral mixture that solidifies into concrete when added to water, sand and other materialsâand that amount could increase by a billion tons by 2050. Globally, the only substance people use more of than concrete, in total volume, is water.
Cementâs virtues, Vlasopoulos says, have long been plain:âIt is inexpensive, pourable and, somewhat inexplicably, becomes hard as a rock. But one other important detail is seldom acknowledged: Cement is dirty. Not dirty as in it wonât come off your clothesâalthough that problem has dogged construction workers for centuries. The key ingredient is limestone, mostly calcium carbonate, the remains of shelled marine creatures. The recipe for making cement calls for heating the limestone, which requires fossil fuels. And when heated, limestone sends carbon dioxide gas wafting into the atmosphere, where it traps heat, contributing to global warming. Cement production is responsible for 5 percent of the worldâs human-produced carbon dioxide emissions; in the United States, only fossil fuel consumption (for transportation, electricity, chemical manufacturing and other uses) and the iron and steel industry release more of the greenhouse gas. And with booming countries such as China and India using cement to construct their rise, cementâs dirtiness looms as one of the foremost downsides of globalization.
If cementâs enormous contribution to air pollution is largely overlooked by the general public, Vlasopoulos, 31, has been aware of it for some time. He grew up in Patras, a Greek port. His father was an engineer and his mother worked in a bank, and during Vlasopoulosâ summers home from Dimokrition Panepistimion Thrakis college, where he studied enviÂronmental engineering, he worked in a cement factory with his uncle. This was fortuitous. His job was to assemble the equipment that measured carbon dioxide emission levels. They were high; typically, a factory produces nearly a ton of carbon dioxide for every ton of cement. Vlasopoulos thought the work was interesting, but he didnât see cement in his future. It was boring, it was old, it was dirty.
Then, one of his professors at Imperial College, where he was working on a masterâs degree in engineering, received funding to examine a new type of cement made by an Australian company. The professor, Christopher Cheeseman, persuaded Vlasopoulos to collaborate on the project and earn a PhD. âThis was a chance to do some nice work,â Vlasopoulos said in his typically understated manner.