Copper miners are boosting output at last after several years of anemic performance. But it may not be enough to meaningfully lift stockpiles from historically low levels, keeping supplies tight in a market critical to the energy transition. The reason is a bottleneck in capacity at the world’s smelters, whose role turning ore into metal makes them a crucial cog in the supply chain between miners and the manufacturers of products from mobile phones and air-conditioning units to electric vehicles. “There isn’t enough smelting capacity around,” said Ye Jianhua, an analyst at Shanghai Metals Market. A surplus of mine ... (full story)