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Using non-hazardous industrial residues in mine waste remediation is beneficial not only for the mining industry where substantial amounts of the waste generated have potential to produce acid rock drainage and pollute the environment, but also the providing industry, minimizing the waste landfilled. In this study green liquor dregs (GLD), residue from 15 different paper mills were characterized to valorize it as a potential product as a cover material. In another part of the study, one of the GLDs and a local till were characterized to determine the optimal mixture of GLD amended till to be used in a field application at the closed Näsliden Mine in northern Sweden. The study concluded 10% GLD-amended till to be the optimal recipe and was successfully applied at the Näsliden mine waste dump. However, the great variability in the characteristics of GLD creates challenges if it is to be valorized as a product., Validerad;2024;Nivå 2;2024-04-02 (hanlid);Funder: Boliden Mineral AB; RISE Processum AB;Full text License: CC BY 4.0This article has previously appeared as a manuscript in a thesis., GLAD, Paperchain

Using non-hazardous industrial residues in mine waste remediation is beneficial not only for the mining industry where substantial amounts of the waste generated have potential to produce acid rock drainage and pollute the environment, but also the providing industry, minimizing the waste landfilled. In this study green liquor dregs (GLD), residue from 15 different paper mills were characterized to valorize it as a potential product as a cover material. In another part of the study, one of the GLDs and a local till were characterized to determine the optimal mixture of GLD amended till to be used in a field application at the closed Näsliden Mine in northern Sweden. The study concluded 10% GLD-amended till to be the optimal recipe and was successfully applied at the Näsliden mine waste dump. However, the great variability in the characteristics of GLD creates challenges if it is to be valorized as a product., Validerad;2024;Nivå 2;2024-04-02 (hanlid);Funder: Boliden Mineral AB; RISE Processum AB;Full text License: CC BY 4.0This article has previously appeared as a manuscript in a thesis., GLAD, Paperchain

In Sweden, a dry cover solution is commonly used to stop sulfide oxidation and the production of acid rock drainage from unattended sulfidic mine waste. Recycling a non-hazardous industrial residue, such as green liquor dregs (GLD) generated during pulp production, in this cover solution is beneficial for both the mining industry where there is a great need for cover materials and the pulp production industry. The objectives of this field study were to install and evaluate the instrumentation of sealing layers made of GLD- and bentonite-amended till, and to evaluate the practical aspects of two different methods of installation: monitoring wells and pits. This practical field study demonstrated that it is difficult to properly seal the drill holes after installing the probes in observation wells and suggests that a better (easier and less costly) alternative for future instrument installation in a sealing layer might be to excavate a pit in the protective layer after installation of the soil cover and then drill the probes into the sealing layer from that pit., Validerad;2023;Nivå 2;2023-11-09 (hanlid);Funder: Boliden Mineral AB; RISE Processum AB;Full text license: CC BY

The oxidation of sulfide minerals in mine wastes is a possible threat to the environment as it might have potential to generate acid rock drainage (ARD). A common method to reduce ARD is to apply a dry cover on the mine waste deposit. Considering the massive amounts of mine waste produced in Sweden (104-million-ton in year 2018) there is a great need for suitable dry cover materials. Using non-hazardous industrial residues in the dry cover would be beneficial for both the mining industry and the providing industry as stricter waste management legislation incentivizes them to develop their waste management strategies. The objective of this study was to investigate if an addition of Green Liquor Dregs (GLD), a residue from pulp production, can decrease the hydraulic conductivity and increase the water retention capacity (WRC) of three different tills, with the purpose of improving the performance of a dry cover material on a mine waste deposit. Another objective was to investigate how the hydraulic conductivity and WRC are affected by the contents of fines and clays in the tills. The study concludes that the water retention capacity of the tills improves with GLD addition, however, the hydraulic conductivity did not decrease enough to reach the in Sweden required < 10−8 m/s. Even though, GLD could still successfully be used in the reclamation of mine sites as the high WRC can be seen as the most important factor in deterring acid rock drainage by keeping the sealing layer close to saturation. This study further indicates that there are other factors than the particle size distribution of the materials that controls the hydraulic conductivity of the mixtures, such as initial water content, dry density, and compaction effort., Validerad;2023;Nivå 2;2023-07-20 (sofila);Funder: Boliden Mineral ABLicens fulltext: CC BY License

In Sweden, a dry cover solution is commonly used to stop sulfide oxidation and the production of acid rock drainage from unattended sulfidic mine waste. Recycling a non-hazardous industrial residue, such as green liquor dregs (GLD) generated during pulp production, in this cover solution is beneficial for both the mining industry where there is a great need for cover materials and the pulp production industry. The objectives of this field study were to install and evaluate the instrumentation of sealing layers made of GLD- and bentonite-amended till, and to evaluate the practical aspects of two different methods of installation: monitoring wells and pits. This practical field study demonstrated that it is difficult to properly seal the drill holes after installing the probes in observation wells and suggests that a better (easier and less costly) alternative for future instrument installation in a sealing layer might be to excavate a pit in the protective layer after installation of the soil cover and then drill the probes into the sealing layer from that pit., Validerad;2023;Nivå 2;2023-11-09 (hanlid);Funder: Boliden Mineral AB; RISE Processum AB;Full text license: CC BY

The oxidation of sulfide minerals in mine wastes is a possible threat to the environment as it might have potential to generate acid rock drainage (ARD). A common method to reduce ARD is to apply a dry cover on the mine waste deposit. Considering the massive amounts of mine waste produced in Sweden (104-million-ton in year 2018) there is a great need for suitable dry cover materials. Using non-hazardous industrial residues in the dry cover would be beneficial for both the mining industry and the providing industry as stricter waste management legislation incentivizes them to develop their waste management strategies. The objective of this study was to investigate if an addition of Green Liquor Dregs (GLD), a residue from pulp production, can decrease the hydraulic conductivity and increase the water retention capacity (WRC) of three different tills, with the purpose of improving the performance of a dry cover material on a mine waste deposit. Another objective was to investigate how the hydraulic conductivity and WRC are affected by the contents of fines and clays in the tills. The study concludes that the water retention capacity of the tills improves with GLD addition, however, the hydraulic conductivity did not decrease enough to reach the in Sweden required < 10−8 m/s. Even though, GLD could still successfully be used in the reclamation of mine sites as the high WRC can be seen as the most important factor in deterring acid rock drainage by keeping the sealing layer close to saturation. This study further indicates that there are other factors than the particle size distribution of the materials that controls the hydraulic conductivity of the mixtures, such as initial water content, dry density, and compaction effort., Validerad;2023;Nivå 2;2023-07-20 (sofila);Funder: Boliden Mineral ABLicens fulltext: CC BY License

The mining industry generates massive amounts of waste that without treatment and in contact with atmospheric oxygen can cause the formation of acid rock drainage (ARD). In Sweden, the most common reclamation measure for mine waste is to apply a multi-layer cover on top of the waste deposit. The access to suitable cover-materials is, however, limited and can lead to extensive costs for the mining companies. This creates a driving force for alternative solutions, e.g., bentonite amendment to till. As bentonite production is costly both economically and environmentally, recycling of industrial residues to produce sealing layer material is an attractive option. The recycling is beneficial for the industry generating the residue, the mining industry using the residue and the society in its strive for zero waste. An industrial residue that has potential to improve the sealing properties of local till is green liquor dregs (GLD), a residue from pulp production. The main objective of this study was to, by laboratory studies and field application and evaluations, investigate if green liquor dregs amended till can be used as a sealing layer material on top of acid generating mine waste. The conclusion from the laboratory study is that the hydraulic conductivity does not decrease significantly with GLD addition to the silty till. However, the water retention capacity, which can be seen as the major important feature of a sealing layer to be used on top of sulfidic mine waste by keeping the layer close to saturation, shows significant improvements with GLD addition. In the field study the GLD amended till was applied successfully from a soil mechanical point of view (e.g., the compaction degree after application). The early results from the monitoring of the sealing layer indicate results comparable to the more frequently used bentonite amendment in a sealing layer, with soil moisture values reaching close to saturation. However, this study also concludes that the great variat

Hydraulic conductivity is often used as a measure to evaluate the effectiveness of a sealing layer material on top of mine waste. However, the most important soil parameter minimizing the oxygen diffusion to the mine waste is the water retention capacity (WRC) of the sealing layer, as a high saturation corresponds to a low oxygen diffusion rate. This study shows that an amendment of Green Liquor Dregs (GLD), an industrial residue, to a till increases its WRC and has therefore potential to be a more accurate method to evaluate the effectiveness of a sealing layer than hydraulic conductivity., Funder: Boliden Mineral AB

Hydraulic conductivity is often used as a measure to evaluate the effectiveness of a sealing layer material on top of mine waste. However, the most important soil parameter minimizing the oxygen diffusion to the mine waste is the water retention capacity (WRC) of the sealing layer, as a high saturation corresponds to a low oxygen diffusion rate. This study shows that an amendment of Green Liquor Dregs (GLD), an industrial residue, to a till increases its WRC and has therefore potential to be a more accurate method to evaluate the effectiveness of a sealing layer than hydraulic conductivity., Funder: Boliden Mineral AB

This report is the outcome of the SIP STRIM project StopOx-Utilization of industrial residuals for prevention of sulfide oxidation in mine waste implemented at Applied geochemistry, Luleå University of Technology running from 2015 to 2018. Boliden Mineral has been partner and co-funder of the project. Other partners in the project were Cementa, Dragon Mining, MEROX, Nordkalk, and SP Processum. The overall aim of the project was to develop prevention technologies to reduce the sulfide oxidation in mine waste, during and after operation, and thereby reduce the generation of acid mine drainage. The StopOx project has been focusing on sulfidic mine waste from the Boliden area which were disposed of and are causing acid mine drainage or have the potential. Industrial residues/products were supplied by BillerudKorsnäs, Cementa, MEROX, and Nordkalk. The report consists of chapters based on three subprojects. Chapter 1. Introduction Chapter 2. Inhibition technology with aim to minimize waste rock oxidation during operations by using residues from other industries (passivation of sulfidic surfaces by the formation of secondary minerals) Chapter 3. The suitability of green liquor dregs as substitutes for or additives to till in a sealing layer as part of a cover system Chapter 4. Weathering of waste rock under changing chemical conditions The research described in chapters 2 and 3 was performed by Ph.D. students and will continue until 2021, while the subproject in chapter 2 ended in 2018.

This report is the outcome of the SIP STRIM project StopOx-Utilization of industrial residuals for prevention of sulfide oxidation in mine waste implemented at Applied geochemistry, Luleå University of Technology running from 2015 to 2018. Boliden Mineral has been partner and co-funder of the project. Other partners in the project were Cementa, Dragon Mining, MEROX, Nordkalk, and SP Processum. The overall aim of the project was to develop prevention technologies to reduce the sulfide oxidation in mine waste, during and after operation, and thereby reduce the generation of acid mine drainage. The StopOx project has been focusing on sulfidic mine waste from the Boliden area which were disposed of and are causing acid mine drainage or have the potential. Industrial residues/products were supplied by BillerudKorsnäs, Cementa, MEROX, and Nordkalk. The report consists of chapters based on three subprojects. Chapter 1. Introduction Chapter 2. Inhibition technology with aim to minimize waste rock oxidation during operations by using residues from other industries (passivation of sulfidic surfaces by the formation of secondary minerals) Chapter 3. The suitability of green liquor dregs as substitutes for or additives to till in a sealing layer as part of a cover system Chapter 4. Weathering of waste rock under changing chemical conditions The research described in chapters 2 and 3 was performed by Ph.D. students and will continue until 2021, while the subproject in chapter 2 ended in 2018.

The mining industry produces massive amounts of waste that without treatment and in contact with oxygen can result in acid rock drainage (ARD) and increased leaching of metals. In Sweden, the common way to manage the mine waste after closure is to apply a dry coverage on top of the waste deposition. The access to a suitable cover-material is however limited and can lead to extensive costs for the mining company. This creates a great driving force for alternative solutions, e.g. bentonite amendment to till. However, bentonite production is costly both economically and environmentally due to time- and resource- consuming production. Recycling of industrial residues as a cover material is another option. The recycling is beneficial for many parts, i.e. the industry producing the residue, the mining industry that will use the residue and the society in its strive for zero waste. An industrial residue that has potential to improve the sealing layer qualities of a local till is Green Liquor Dregs (GLD), a residue from pulp production in a paper mill. In this study 5 to 20 wt. % of GLD from two different paper mills, with varying total solid content (TSC) and particle size distributions (PSD), were mixed with three tills also with varying PSD and TSC. The objectives of the study were to investigate if GLD addition can improve a till so it can be used in a sealing layer, how the fines- and clay content in the tills affects the hydraulic conductivity (HC) and the water retention capacity (WRC) of the till-GLD mixtures, and how the initial water content will affect the HC in the different mixtures. The HC of the mixtures based most of the tills studied improved, but not enough to reach the required 10-8 m/s. Only the material based on a more clayey silty till had an HC below 10-8 m/s, even if it increased with the addition of GLD. The WRC, on the other hand, shows promising results, especially for 15 wt. % GLD addition. An increase in WRC is seen the more GLD is added. Howeve

Sul dic mine waste le unattended and in contact with oxygen oxidize and have potential to produce acid rock drainage (ARD). A typical method in Sweden to stop sul de oxidation is to apply a dry cover on top of the mine waste. Using the non-hazardous industrial residue Green Liquor Dregs (GLD) in the cover is useful for the mining industry and the industry providing the residue and a large bene t for the environment. In this study, the e ectiveness of a mixture of till and 10 wt. % of GLD in a dry cover was studied by monitoring temperature, oxygen- and moisture content. e conclusion is that the sealing layer in una ected by frost, the oxygen concentrations are decreasing with time, but not in depth and the sealing layer with GLD-till mixture seem to be nearly saturated., paperChain, GLAD - MISTRA Closing the loop

Sul dic mine waste le unattended and in contact with oxygen oxidize and have potential to produce acid rock drainage (ARD). A typical method in Sweden to stop sul de oxidation is to apply a dry cover on top of the mine waste. Using the non-hazardous industrial residue Green Liquor Dregs (GLD) in the cover is useful for the mining industry and the industry providing the residue and a large bene t for the environment. In this study, the e ectiveness of a mixture of till and 10 wt. % of GLD in a dry cover was studied by monitoring temperature, oxygen- and moisture content. e conclusion is that the sealing layer in una ected by frost, the oxygen concentrations are decreasing with time, but not in depth and the sealing layer with GLD-till mixture seem to be nearly saturated., paperChain, GLAD - MISTRA Closing the loop

The mining industry produces massive amounts of waste that without treatment and in contact with oxygen can result in acid rock drainage (ARD) and increased leaching of metals. In Sweden, the common way to manage the mine waste after closure is to apply a dry coverage on top of the waste deposition. The access to a suitable cover-material is however limited and can lead to extensive costs for the mining company. This creates a great driving force for alternative solutions, e.g. bentonite amendment to till. However, bentonite production is costly both economically and environmentally due to time- and resource- consuming production. Recycling of industrial residues as a cover material is another option. The recycling is beneficial for many parts, i.e. the industry producing the residue, the mining industry that will use the residue and the society in its strive for zero waste. An industrial residue that has potential to improve the sealing layer qualities of a local till is Green Liquor Dregs (GLD), a residue from pulp production in a paper mill. In this study 5 to 20 wt. % of GLD from two different paper mills, with varying total solid content (TSC) and particle size distributions (PSD), were mixed with three tills also with varying PSD and TSC. The objectives of the study were to investigate if GLD addition can improve a till so it can be used in a sealing layer, how the fines- and clay content in the tills affects the hydraulic conductivity (HC) and the water retention capacity (WRC) of the till-GLD mixtures, and how the initial water content will affect the HC in the different mixtures. The HC of the mixtures based most of the tills studied improved, but not enough to reach the required 10-8 m/s. Only the material based on a more clayey silty till had an HC below 10-8 m/s, even if it increased with the addition of GLD. The WRC, on the other hand, shows promising results, especially for 15 wt. % GLD addition. An increase in WRC is seen the more GLD is added. Howeve