Steel and metal industry waste

In 2013, the Swedish steel industry used approximately 5.6 million tonnes of metallic raw material. Approximately 200,000 tonnes remain after production, in slag, oxidised dust and sludge which are not recycled/reused at steelworks.

At steel mills, it is common to recover metals, for example iron and alloy metals, from the slag utilising with various types of metal extraction. Therefore, the slag from the steel mills generally contains low levels of recyclable metals.

Dust is formed in most of the steel industry’s hot processes and is disposed of in gas treatment plants. From the dust that is separated, the metal content of the constituent metal can be recycled. It may be, for example, iron, zinc, nickel, chromium and molybdenum. In addition to iron oxide, the dust produced in the manufacture of stainless steel also contains oxides of chromium and nickel.

Dust from scrap-based steel mills in particular often contains a significant amount of zinc. From ore-based steel production, dust and sludge from the gas purification have a relatively high content of iron oxide and carbon, and often very low content of other metals. Therefore, these materials have a value to reuse in their own processes. They are also used for the production cement, for example. Then, however, the metal content is lost from the cycle.

Vanadium in steel slag

Together with the main metals that are extracted, there are other metals that are not presently be used at the steel mills. This is due to that, for example, the costs are too high or because there are limitations in available technology. One example is vanadium found in iron ore. The iron ore that LKAB processes contain just over 0.1 per cent vanadium. SSAB, in turn, primarily uses such iron ore in its steel production. Vanadium ends up in complex oxides in the steel sheet that is difficult to extract for commercially marketable product. In 2013, SSAB in Sweden used almost four million tonnes of iron ore from LKAB. This means that the slag contained some 4,000 tonnes of vanadium, which corresponds to about half of Europe’s need for vanadium. For several years, SSAB has been exploring the possibility of recycling vanadium. However, this would require major investments in new processes and so far has not been deemed profitable.

The aluminium industry wants to recycle more

In Sweden, 130,000 tonnes of aluminium are extracted each year and 60,000 tonnes are recycled. Recycling is extremely profitable from an energy point of view, compared to primary extraction. It only takes one-twentieth of the energy. More than a third of Europe’s aluminium production is now re-smelted or recycled aluminium. Remelted aluminium is mostly process scrap. Today, the recycling rate is over 95 percent for aluminium from the construction and transport sector, while the average recycling rate is 73 percent. The aluminium industry expects to reach a recycling rate of 90 percent on average with a well-developed recycling system.

The foundry industry

Foundries manufacture many different castings and add a wide range of alloy metals. In total, around 300,000 tonnes of castings are produced per year in Sweden and the imports are about the same. Many of the potentially critical metals are used as an additive in one or more products. Recirculation of metals and minerals in the Swedish foundry industry has become more important over the years. Some residues are still deposited, as an example, in the form of slag (about 30,000 tonnes per year), dust and foundry tailings (about 70,000 tonnes per year). There is no estimate of how much metals these landfill residues contain. In contrast, about 60,000 tonnes a year are recycled metal shavings.

Other industrial landfills

There are an estimated 1,000 industrial landfills in Sweden. Some, such as landfills with the primary content of metal hydroxide sludge, may have a high metal content. Others, such as shaft depository or sawmill landfills, lack metals in scrap form. In these, there is also combustion ash that contains a significant number of metals.