Photo taken on Dec. 17, 2012 shows Hong Kong's first zero-carbon building ZCB in Hong Kong, south China. The building, which generates on-site renewable energy more than operation needs from photovoltaic panels and biodiesel tri-generation system and exports surplus energy to offset embodied energy of its construction process and major structural materials, will be opened to the public on Jan. 5, 2013. (Xinhua/Lui Siu Wai)