In most of today's smelting, aluminum ore, also known as bauxite, is first smelted into alumina through the Bayer Process. This step could be replaced by the Pedersen process -- either result in alumina. Unlike the smelting processes of iron and coal into steel or copper and tin into bronze, which require thermal energy, alumina must be smelted with electrical energy. This is done through the Hall–Héroult process, producing 99.5–99.8% pure aluminum.