Why Is a Significant Part of Mining Industry Side Streams Left Unused, and How Could We Make Better Use of Mineral Raw Materials?

In Finland, substantial investments are made in the utilisation of geological natural resources, and there is great potential in improving the recovery of extractive waste and side streams. In fact, the competence and necessary information related to waste management and side streams already exists, yet the utilisation rate remains low. Päivi Kauppila, Chief Expert at the Geological Survey of Finland GTK, explains what is causing the situation and what could be done to improve it.

Three workers in a factory. Two are looking together one part of the processa and one is whisking material in a big bowl. — GTK Mintec’s pilot plant and laboratories offer an opportunity to implement a comprehensive mindset on raw materials right from the start of the planning process.

In the EU countries, the level of waste treatment and recycling in relation to the actual amount of waste is the lowest in countries where most of the waste generated is extractive waste. In addition to Finland, these countries include Romania, Bulgaria and Sweden.

According to Eurostat statistics, on average 60% of all waste was treated in the EU in 2020: 39% was recycled, 15% was used for backfilling, and 6% for energy recovery. The remaining 40% was placed in landfills and extractive waste areas.

In Finland, approximately 16% of all waste streams were recovered in 2020, whereas 84% of the total waste amount was landfilled or deposited in extractive waste areas. The total amount of mineral waste in Finland was over 100 million tonnes, of which only about 7.5% was recovered.

In Finland, extractive waste is mainly used for earthworks in mining areas and for backfilling

Mining waste from industrial mineral mines and natural stone production is often easier to utilise in, for example, environmental construction than side streams from the mining of metallic ores, as extractive waste generated in the excavation of metallic ores is more likely to contain metals or minerals harmful to the environment than other extractive waste flows.

Waste rock generated in mining is primarily used in mine areas to complete earthworks, such as building dams and roads, and for backfilling. In addition, some of the waste rock can be used in earthworks outside the mines, as well.

Mine tailings generated during minreal processing can be used to raise dams in tailing areas and as backfill materials. Mine tailings can also be used outside the mines, such as in soil conditioning, in bricks, as a filling material in paint and concrete, and, to a certain extent, in the manufacturing of sulphuric acid.

As a case in point, pyrite-rich tailings from the zinc and copper mine of Pyhäsalmi Mine Oy have been used in the manufacturing of sulphuric acid, and Oy Nordkalk Ab’s production plant in Lappeenranta uses minerals such as calcite recovered from wollastonite production as soil conditioners.

At Yara’s phosphate mine and phosphorus plant in Siilinjärvi, numerous different substances are recovered from mine tailings. Consequently, calcite is used in water neutralisation, biotite is, among other things, used as a raw material in fertilisers designed for organic farming, and phlogopite is a suitable mineral filler for polymers and coatings. In turn, the gypsum generated in Yara’s fertiliser production is used to bind phosphorus in fields.

Keliber Oy is planning to recover feldspar and quartz from mine tailings as part of the lithium project in Kaustinen and turn them into separate products that can be used in the ceramics and glass industry. In addition, quartz can also be used as foundry sand. Furthermore, studies have been conducted to determine the suitability of mine tailings in concrete manufacturing and in asphalt coating materials. In turn, muscovite, which is separated from mine tailings, can be used as a filling material in the plastic industry, whereas biotite recovered from waste rock is well-suited as a raw material in fertilisers and can be used for the removal or retention of phosphorus from wastewater.

Why is it important to boost the utilisation of mining waste?

Reducing the overall quantity of waste is an EU-level target, which is also enshrined in the Finnish Waste Act. The primary goal is to reduce the quantity and harmfulness of waste, while other objectives include increasing the reuse, recycling and recovery of waste materials.

As mining activities are energy-intensive and produce substantial side streams, they should be carried out as sustainably as possible. The advantage of side stream recovery is saving virgin materials. In addition, more efficient use of already extracted and crushed or ground rock aggregates, such as mine tailings, saves energy and reduces carbon emissions. Such measures increase the sustainability of mining activities and support the circular economy.

Utilisation of extractive waste also reduces the amount of extracted waste to be deposited in mining areas and, at the same time, facilitates the management of waste, cuts operational costs, and reduces environmental risks. Moreover, measures that reduce risks also increase the acceptability of mining activities and, therefore, generate added value for both mining companies and the society.

In a preliminary study, published by the Ministry of Economic Affairs and Employment of Finland, mapping the possibilities of utilising waste rock and mine tailings, it was found that the cost of transportation in relation to the commercial value of mining waste is one of the most significant challenges for the utilisation of waste rock and mine tailings.

There are also legislative obstacles and challenges, especially if the material is already classified as waste. Dismantling these obstacles would promote the further use of side stream materials.

Mineral raw materials are left unused – one countermeasure is comprehensive thinking with a circular economy twist

In the recent years, major efforts have been made in Finland on discovering new utilisation possibilities – and new opportunities have indeed been found. However, the process of turning the research innovations into action and new products has been relatively slow, at least in some areas.

Introducing a more comprehensive mindset to the field is essential. When planning a mine, the goal is often to recover the most abundant and valuable substances found in the area, such as nickel, copper, gold or lithium. However, in addition to the main valuables, a deposit often contains other raw materials that could be utilised, but these will all end up as extractive waste if the possibilities of recovering them are not considered already in the planning of the mining operations. Indeed, it is challenging to utilise waste once it has already been disposed.

To increase and facilitate the utilisation of extractive waste, the circular economy must be introduced as a planning criterion for mining operations right from the start, with the aim of achieving the highest possible utilisation rate for the material to be extracted and processed. Consequently, the enrichment process can, for example, be modified to reduce the amount of waste, and waste rock can be sorted according to criteria that promote a high utilisation rate. As a result, the amount of waste to be disposed will be reduced.

Even at present, the mining sector continues to adhere to a single-operator model, which reduces the possibilities of side stream recovery. In contrast, partnering up with other operators would enable more extensive exploitation of material flows. The Outokumpu Mining Hub, which is currently under development in Outokumpu, aims to create and pilot new cooperation models for the mining sector between both small and large operators.

The forestry sector holds positive examples of how different business concepts can be applied on site and wood material utilised in a versatile manner, while also enabling the business operations of everyone involved. Metsä Group is just one example of such collaboration.

GTK boosts processes and promotes the circular economy

GTK has extensive knowledge and expertise in mineral materials, their research and processing, and the management of extractive waste. GTK maintains an extensive database of mineral deposits and collects data on secondary mineral raw materials. As one of the research themes, GTK is investigating the potential of putting old extractive waste areas to new use.

GTK Mintec’s pilot plant and laboratories offer an opportunity to implement a comprehensive mindset on raw materials right from the start of the planning process. For example, GTK Mintec has been able to separate the most harmful fractions from mine tailings, such as minerals containing arsenic, by modifying the enrichment process. This enables the production of mine tailings which have more potential for reuse and are more environmentally friendly to dispose.

Other research at GTK includes, for example, the following: utilisation of extractive waste in the ceramics industry, use of tailings and other side streams as backfill materials, utilisation of side streams and, biochar in the covering of extractive waste.

The separation of both harmful substances and valuable materials from waste requires a lot of energy and involves multiple work stages. A comprehensive economic cost-benefit analysis is needed in view of the process itself as well as the environment. The reality is that not all mineral waste can be recovered, at least not at the moment. However, a number of possibilities remain open.

GTK is currently building a test field at GTK Mintec in Outokumpu, and the site will be used to test the possibilities of using different side streams for the management of extractive waste. In addition, one of the future research topics will be the utilisation of extractive waste in growing media.

Päivi Kauppila, Chief Expert at the Geological Survey of Finland GTK, was interviewed for the article. She works on issues related to mining environments and the circular economy, as well as research questions pertaining to the management and utilisation of extractive waste.