Producing cement takes a massive toll on the environment. In fact, the energy-intensive process of making cement accounts for around 5 percent of global CO2 emissions. Researchers have turned to irradiated plastic bottles and tweaking calcium levels to improve cement production in the past, and now they have turned to volcanic ash, which they say has a number of advantages an ingredient in the cement manufacturing recipe. Volcanic ash is abundant around active and inactive volcanoes, its natural properties make it strong, and using it to make cement requires less energy than when making traditional cement.