On Earth Day 2013, we take a look at concrete, the single most widely used material in the world- with a carbon footprint to match. The world uses nearly 7 billion cubic meters of concrete per year, making it the most-used industrial material after water. Even though making concrete is less energy intensive than making steel or other building products, we use so much of it that concrete production accounts for 3 to 8% of global carbon dioxide emissions.
Civil engineers are developing greener concrete by replacing some of the cement (an ingredient of concrete) with byproducts of biofuels made from wood chips, wheat straw or other agricultural residue. This ash byproduct reacts chemically with the cement to make it stronger. Replacing 20% of the cement with the material increased the strength of the concrete by 32%. Using the byproduct in this way, rather than just landfilling it, has the added benefit of reducing the cost of bioethanol production.