Villager Ma Zhen boils water with marsh gas in Jingadao Village of Changzhi County, north China's Shanxi Province, Dec. 11, 2012. Jingadao Village of Changzhi County has formed a recycling economy. Villagers here use marsh gas as fuel after fermenting pig excrement, adopt clean sewage disposal system, produce natural fertilizer with animal excrement and plant green vegetables. (Xinhua/Yan Yan)