Chapter 1: What is the main topic discussed in this episode?
It's TED Talks Daily. I'm Elise Hu. Climate change is one of the biggest challenges we face, and the stakes could not be higher. My colleagues at TED-Ed produced a video series to cut through the complexity and explain the science in a clear way. It's inspired by Bill Gates' new book, How to Avoid a Climate Disaster.
And today's lesson is about a material that's all around us, has a huge carbon footprint, and how to reinvent it.
Chapter 2: What is the significance of concrete in our modern world?
You can watch all seven lessons for free at ed.ted.com slash plan for zero. And that's plan F-O-R zero. One single word.
Thousands of years ago, the Romans invented a material that allowed them to build much of their sprawling civilization. Pliny the Elder praised an imposing sea wall made from the stuff as impregnable to the waves and every day stronger. He was right. Much of this construction still stands, having survived millennia of battering by environmental forces that would topple modern buildings.
Today, our roads, sidewalks, bridges, and skyscrapers are made of a similar, though less durable, material called concrete. There's three tons of it for every person on Earth, and over the next 40 years, we'll use enough of it to build the equivalent of New York City every single month. Concrete has shaped our skylines, but that's not the only way it's changed our world.
It's also played a surprisingly large role in rising global temperatures over the last century, a trend that has already changed the world and threatens to even more drastically in the coming decades. To be fair to concrete, basically everything humanity does contributes to the greenhouse gas emissions that cause global warming.
Most of those emissions come from industrial processes we often aren't aware of, but touch every aspect of our lives. Look around your home. Refrigeration, along with other heating and cooling, makes up about 6% of total emissions. Agriculture, which produces our food, accounts for 18%. Electricity is responsible for 27%.
Walk outside in the cars zipping past, planes overhead, trains ferrying commuters to work, transportation, including shipping, contributes 16% of greenhouse gas emissions. Even before we use any of these things, making them produces emissions. A lot of emissions. Making materials — concrete, steel, plastic, glass, aluminum, and everything else — accounts for 31% of greenhouse gas emissions.
Concrete alone is responsible for 8% of all carbon emissions worldwide, and it's much more difficult to reduce the emissions from concrete than from other building materials. The problem is cement, one of the four ingredients in concrete. It holds the other three ingredients, gravel, sand and water, together. Unfortunately, it's impossible to make cement without generating carbon dioxide.
The essential ingredient in cement is calcium oxide, CaO. We get that calcium oxide from limestone, which is mostly made of calcium carbonate, CaCO3. We extract CaO from CaCO3 by heating limestone. What's left is CO2, carbon dioxide. So for every ton of cement we produce, we release one ton of carbon dioxide.
As tricky as this problem is, it means concrete could help us change the world a third time by eliminating greenhouse gas emissions and stabilizing our climate. Right now, there's no 100% clean concrete, but there are some great ideas to help us get there. Cement manufacturing also produces greenhouse gas emissions by burning fossil fuels to heat the limestone.
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