BEIJING : Rio Tinto has signed a memorandum of understanding (MoU) with China Baowu, the world's biggest steelmaker by volume, to develop projects aimed at enabling lower grade ore to be used in low-carbon steelmaking, the miner said on Monday. The demonstration projects include building a pilot-scale plant at one of Baowu's steel mills in China that will allow Direct Reduced Iron (DRI) steelmaking using low and medium grade ores.