Add diesel to the commodities flooding global markets from China. The nation exported a record volume of the fuel last month after already shipping unprecedented amounts of steel and aluminum overseas. The weakest economic growth since 1990 is sapping domestic demand for commodities, while refineries, mills and smelters grapple with excess capacity after years of expansion. “A lot of it has to do with slowing demand at a time when companies had plans for much a better demand environment, so capacities had been increased,” said Ivan Szpakowski, a commodities strategist at Citigroup Inc. in Hong Kong. “As demand slows, that’s led to an overcapacity in the domestic market and producers have sought to export the surplus.” Exports of Chinese raw materials are exacerbating a global glut that drove prices to the lowest since the 2008 financial crisis and prompted steel and aluminum producers around the world to protest against […]