CHEYENNE, Wyo. (AP) — Organizers of a $20 million contest to develop products from greenhouse gas that flows from power plants announced two winners Monday ahead of launching a similar but much bigger competition backed by Elon Musk. Both winners made concrete that trapped carbon dioxide, keeping it out of the atmosphere, where it can contribute to climate change. Production of cement, concrete's key ingredient, accounts for 7% of global emissions of the greenhouse gas, said Marcius Extavour, XPRIZE vice president of climate and energy.