This paper captures some of the emerging consensus points that came out of the workshop "Mineral Resources in Life Cycle Impact Assessment: Mapping the path forward", held at the Natural History Museum London on 14 October 2015: that current practices rely in many instances on obsolete data, often confuse resource depletion with impacts on resource availability, which can therefore provide inconsistent decision support and lead to misguided claims about environmental performance. Participants agreed it would be helpful to clarify which models estimate depletion and which estimate availability, so that results can be correctly reported in the most appropriate framework. Most participants suggested that resource availability will be more meaningfully addressed within a comprehensive Life Cycle Sustainability Assessment framework rather than limited to an environmental Life Cycle Assessment or Footprint. Presentations from each of the authors are available for download [1].
The waste management is in need of a reliable and economical treatment method for metals in fly ashes from municipal solid waste incineration (MSWI). However, no state-of-the-art technique has gained wide acceptance yet. This Doctoral Thesis aimed at assessing the possibilities and limitations of carbonation as a stabilization method. Factors that were studied are the partial pressure of carbon dioxide, the addition of water, the temperature, and the reaction time. Laboratory experiments were performed applying methods such as factorial experimental design, thermal analysis, scanning electron microscopy (SEM), x-ray diffraction (XRD), and leaching assays including titration at static pH and sequential extraction. Leaching data were verified and complemented using chemical equilibrium calculations. Data evaluation was performed by means of multivariate statistics such as multiple linear regression, principal component analysis (PCA), and partial least squares (PLS) modeling. It was found that carbonation is a good prospect for a stabilization technique especially with respect to the major pollutants lead (Pb) and zink (Zn). However, a mobilization of cadmium (Cd) was observed, which requires further research on possible countermeasures such as e.g. metal demobilization through enhanced silicate formation.
The potential to damage the environment is the major motive to treat solid wastes. One main group of pollutants comprises metals such as cadmium, chromium, copper, mercury, nickel, lead, and zinc. This paper is a synthesis of five elsewhere published investigations focusing on the possibilities and limits to control the flux of metals from solid wastes using anaerobic processes. In particular, the treatment of sulfide forming elements and hexavalent chromium (Cr(VI)) were studied at both bench-, pilot-, and full-scale. It was found that two-step processes have the potential to significantly improve the quality of solid wastes. In a first step, metals were leached and transferred to the process water. In a second step, the metal-enriched process water was treated under methanogenic conditions facilitating metal trapping through precipitation as sulfides or hydroxides. Anaerobic hydrometallurgy is judged to be a promising technique that has the potential to gain wide acceptance in the treatment of metal-containing solid wastes from a wide variety of sources.
Waste management is in need of a reliable and economical treatment method for metals in fly ashes from municipal solid waste incineration (MSWI). However, no state-of-the-art technique has gained wide acceptance yet. This paper is a synthesis of five elsewhere published investigations covering a project which aimed to assess the possibilities and limitations of adding carbon dioxide (CO2) to fly ash as a stabilization method. Carbonation factors that were studied are the partial pressure of carbon dioxide (CO2), the addition of water, the temperature, and the reaction time. Laboratory experiments were performed applying methods such as factorial experimental design, thermal analysis, scanning electron microscopy (SEM), X-ray diffraction (XRD), and leaching assays including pHstat titration and sequential extraction. Leaching data were verified and complemented using chemical equilibrium calculations. Data evaluation was performed by means of multivariate statistics such as multiple linear regression, principal component analysis (PCA), and partial least squares (PLS) modeling. It was found that carbonation is a good prospect for a stabilization technique especially with respect to the major pollutants lead (Pb) and zinc (Zn). Their mobility decreased with increasing factor levels. Dominating factors were the partial pressure of CO2 and the reaction time, while temperature and the addition of water were of minor influence. However, the treatment caused a mobilization of cadmium (Cd), requiring further research on possible countermeasures such as metal demobilization through enhanced silicate formation.
Multivariate data analysis (MVDA), a new statistical approach in terms of landfill research, was performed at the evaluation of data sets from three investigations. The interrelationships among variables as well as variation between observations could be examined. Causal relations between experimental factors and response variables have been identified using scatterpott interpretation. The ease of using MVDA at data evaluation is proved. MVDA techniques as follows were applied: principal component analysis (PCA), partial least squares modelling (PLS) and partial least squares discriminant analysis (PLS-DA).
Multivariate data analysis (MVDA), a new statistical approach in terms of landfill research, was performed on the evaluation of three investigations. It gains advantage over classical statistical methods when multiple variables and their interactions have to be considered. In addition, it is tolerant for incomplete datasets. MVDA techniques as follows were applied: principal component analysis (PCA), partial least squares modelling (PLS) and partial least squares discriminant analysis (PLS-DA). The interrelationships among variables as well as variation between observations could be examined and illustrated by a few plots.
In Japan, expenses for landfilling yield about 400 US$ per t of ash, which gives an incentive to reduce the amount of landfilled ash. At NIES (National Institute for Environmental Studies) in Tsukuba, Japan, the AMT process (Accelerated Mineralization Technology) was developed aiming at the treatment of ashes and production of soil-like material for reuse. The objective of the project EJA was to evaluate the AMT process on the basis of available information and the possibilities the process could offer with respect to the conditions present in Sweden.With support of researchers at NIES, available literature including unpublished manuscripts on the AMT process was compiled, translated and evaluated. During treatment, the ashes are washed, aged and mixed with up to 5 weight-% of biodegradable organic matter. The material is stabilized at landfill. During up to several decades, metals are demobilized through a combination of three mechanisms, viz. carbonation, clay formation, and humification. Also persistent organic pollutants (POP) are demobilized due to humification products or they are degraded anaerobically. When the treatment is completed, the reuse of the material is envisaged.Due to the long treatment period, the AMT method might not be favored by ash producers in Sweden. In the future, landfill companies could be interested in the technology, since they are experienced to handle waste at long sight. This, however, requires that the legislation does not pose any hindrance for the implementation of the method, e.g. regarding the requirement to add organic matter to the ash. Above all, it remains several years of research on the AMT process to fully understand and evaluate the underlying biological and chemical processes as well as their interaction.
Increasing amounts of municipal solid waste incineration (MSWI) residues are treated prior to landfilling or reuse. In Japan, electric arc melting is used for bottom ash vitrification that generates a glasslike slag. The objective of this paper was to assess this pretreatment technique with respect to its effect on metal mobility and metal content. Both bottom ash and slag were sampled and analyzed on total solids (TS), fixed solids (FS), particle density (P), specific BET surface area, particle size distribution, and total element content. A six-step wet sequential extraction procedure was used for assessing metal mobility. The results were qualitatively verified by scanning electron microscopy. The major conclusion was that the availability of various metals was affected differently by electric arc vitrification. Metals were solidified, stabilized, and/or separated from the slag. The mobility of Cr, Cu, Zn, Pb, and Ca was reduced. In slag, major fractions of these elements were found in moderately reducible phases or in the residual slag lattice. The approximately three-fourths of Pb [174 ± 7 mg (kg of FS)-1] and half of Zn content [676 ± 352 mg (kg of FS)-1] were most likely removed from bottom ash through evaporation. The total content increases of Al, Cr, Ni, and Cd (51 ± 3, 621 ± 27, 138 ± 19, and 99 ± 32%, respectively) were probably caused by the wear of furnace refractories.
I förbränningsanläggningarnas flygaska koncentreras föroreningar från det avfall som förbränts. För att förhindra att dessa föroreningar sprids i samband med deponering kan askan stabiliseras. I Luleå utvecklas en ny metod för stabilisering av flygaska där koldioxid används i en process, så kallad karbonatisering, för att förhindra utlakning av bland annat miljöstörande metaller. Metoden utnyttjar den höga pH-halten i askan. Det är en betydligt enklare och billigare metod än de som tidigare prövats.
Discusses the two-step anaerobic degradation (TSAAD) system of the Boras plant in Sweden. Reasons for the decision of the municipality of Boras to choose the source separation refuse system; Anaerobic digestion technology used by the Boras plant; How the TSAAD works; Results of the evaluation of the operation.
Fly ash from municipal solid waste incineration (MSWI) is considered as hazardous waste that calls for a robust, reliable, and reasonable treatment technique. This investigation aims to assess the impact of CO2 partial pressure, water addition, time, and temperature on the stabilization of MSWI fly ash with particular emphasis on Pb, Zn, Cd, and Cr. Carbonation and element mobility were studied by applying thermal analysis and leaching assays on fly ash samples treated according to a 24 factorial design. The relationship between the factors and the response variables was evaluated using partial least squares modeling. Chemical equilibrium calculations were performed so as to complement the experimental findings. Decalcification of carbonated fly ash in a typical Swedish landfill was estimated at 0.13 mm.yr(-1) Treatment through carbonation reduced the availability of Pb and Zn about 100 times and also the carbonate alkalinity of 7.4 eq. (kg.FS)(-1) (FS represents the fixed solids) was remedied successfully. However, shortcomings that need to be resolved are the remobilization of Cr with time and the mobilization of Cd.
Dry scrubber residue from municipal solid waste incineration (MSWI) was characterized to identify critical inorganic pollutants and to suggest a conceptual treatment method. The key methods used were thermal analysis, including thermogravimetry (TG) and differential thermal analysis (DTA), pHstat titration, qualitative X-ray diffraction (XRD), scanning electron microscopy (SEM), chemical equilibrium calculations, and statistics such as error propagation, principal component analysis (PCA), and empirical modeling based on factorial designs. Based on EU directives, the major inorganic pollutants Cd, Cr, Pb, and Zn were found. In addition, the pH was too high. With dry scrubber residue stabilization in mind, the impact of carbonation and hydration was assessed and judged to be encouraging. In particular, chemical equilibrium calculations showed that carbonation has considerable potential to lower the pH and the availability of Pb, Zn, and Cr. The impact of carbonation on the mobility of Cd was found to be small. During carbonation, a metal-trapping calcium aluminosilicate hydrate (C–A–S–H) phase is also formed. Both processes together have the potential to lead to a robust, reliable, and reasonable stabilization method for dry scrubber residue. However, to control these processes, the decisive factors need to be identified and their effects need to be quantified. Ca, Cl, Na, and K might be abundant components which would be mobile even after stabilization.
Solid residues from municipal solid waste incineration (MSWI) can be categorized as air pollution control residues (AR) and bottom ash (BA). Both categories pose a particular environmental threat on account of the risk of the release of dioxins and metals. In Japan, handling of MSWI residues is of major concern and the treatment of AR prior to landfilling is stipulated. Accepted treatment: techniques are melting, cementitious S/S (stabilization and solidification), stabilization with a chemical agent and acid extraction. These methods are reviewed and evaluated in this paper with respect to: quality; quantity and utilization of end products; treatment costs; energy demand and process reliability. Thermal processes are superior regarding dioxin removal as well as material recovery and reuse, but treatment costs can be as high as 60 000 Y t(-1), i.e. one order of magnitude higher than for other processes. Cementitious SIS and chemical stabilization are characterized by the ease of operation, but the solid waste mass is increased by up to 40 and 10 wt.-%, respectively. Acid extraction is a proven and reliable technique and is inexpensive: nevertheless, it has the smallest share of the market.
Dissolved organic carbon (DOC) may affect the transport of pollutants from incineration residues when landfilled or used in geotechnical construction. The leaching of dissolved organic carbon (DOC) from municipal solid waste incineration (MSWI) bottom ash and air pollution control residue (APC) from the incineration of waste wood was investigated. Factors affecting the mobility of DOC were studied in a reduced 26-1 experimental design. Controlled factors were treatment with ultrasonic radiation, full carbonation (addition of CO2 until the pH was stable for 2.5 h), liquid-to-solid (L/S) ratio, pH, leaching temperature and time. Full carbonation, pH and the L/S ratio were the main factors controlling the mobility of DOC in the bottom ash. Approximately 60 weight-% of the total organic carbon (TOC) in the bottom ash was available for leaching in aqueous solutions. The L/S ratio and pH mainly controlled the mobilization of DOC from the APC residue. About 93 weight-% of TOC in the APC residue was, however, not mobilized at all, which might be due to a high content of elemental carbon. Using the European standard EN 13 137 for determination of total organic carbon (TOC) in MSWI residues is inappropriate. The results might be biased due to elemental carbon. It is recommended to develop a TOC method distinguishing between organic and elemental carbon.
The re-use of bottom ash in road construction necessitates a tool to predict the impact of trace metals on the surroundings over the lifetime of the road. The aim of this work was to quantify the effect of environmental factors that are supposed to influence leaching, so as to suggest guidelines in developing a leaching procedure for the testing of incineration residues re-used in road constructions. The effects of pH, L / S (liquid-to-solid ratio), leaching time, and leaching atmosphere on the leachate concentrations of Cd, Cr, Cu, Ni, Pb, and Zn were studied using a two-level full factorial design. The most significant factor for all responses was the pH, followed by L / S, though the importance of pH and L / S is often ignored in leaching tests. Multiple linear regression models describing the variation in leaching data had R2 values ranging from 61-97%. A two-step pH-stat leaching procedure that considers pH as well as L / S and leaching time was suggested.
Different phases of the life cycle of a landfill receiving municipal solid waste (MSW) were monitored in landfill simulation reactors (LSRs) with the aim of investigating the effects of co-disposal of wastes containing organic pollutants (OPs) with MSW. Two LSRs out of four filled with well-characterised MSW received waste materials containing OPs. These included two types of plasticised PVC flooring materials, freon-blown insulation and phosphorus- and nitrogen-based flame-protected materials. Each of the two LSRs was operated under acid fermentative and neutral methanogenic conditions, respectively as were their corresponding controls, i.e. without extra OP. The methanogenic consortia degrading MSW were hampered by the addition of wastes containing OPs, probably due to the presence of Freon R11 and its degradation product, R21. The concentrations of R11 and R21 ranged between 0.1 and 1800 mg m super(-3) depending on the biogas production rate in the OP-amended LSRs. Losses of butylbenzyl- (26%) and bis(2-ethylhexyl)phthalate (15%) from one of two flooring materials was observed, whereas the other remained unaffected. Methanogenic conditions favoured the loss of plasticisers as compared to acidogenic conditions. Total phosphorus was significantly higher in the OP-spiked LSRs, which indicated a transformation of the non-halogenated flame-retardants.
Our recently developed non-destructive imaging technique was applied for the characterisation of nanoparticles synthesised by X-ray radiolysis and the sol-gel method. The interfacial conditions between the nanoparticles and the substrates were observed by subtracting images taken by scanning electron microscopy at controlled electron acceleration voltages to allow backscattered electrons to be generated predominantly below and above the interfaces. The interfacial adhesion was found to be dependent on the solution pH used for the particle synthesis or particle suspension preparation, proving the change in the particle formation/deposition processes with pH as anticipated and agreed with the prediction based on the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory. We found that our imaging technique was useful for the characterisation of interfaces hidden by nanoparticles to reveal the formation/deposition mechanism and can be extended to the other types of interfaces.
Groundwater is an important source of drinking water where advanced knowledge in the area is of great importance in order to ensure the drinking water quality for future generations. Groundwater is chemically complex because it is formed from a large variety of water sources where the water comes from and passes through different geological and hydrological environments. Environmental forensics is an important area in environmental studies where a wide variety of analytical techniques are integrated to be able to trace and identify sources of pollution. In the Gäddvik project, environmental forensics is applied as a method for tracking pollution in naturally occurring waters. Concentrations of selected elements, oxygen- and hydrogenisotopes and cerium-anomalies have been used to show chemical differences between different water sources in groundwater reservoirs in the Gäddvik area. A sub-study at Kvarnträsket (a lake located in the Gäddvik area) has been carried out to track surface water intrusion in nearby groundwater used for drinking water. Different types of graphs and charts have been created from data on the area, where these have been used to give a simplified visualization of different geochemical trends for selected elements/isotopes. Quality differences between two nearby groundwater reservoirs have been studied and discovered, where one is Luleå’s main groundwater reservoir and the other is a backup groundwater reservoir. Surface water from the Luleå River has been detected in the main groundwater reservoir to a greater extent than in the backup groundwater reservoir. This may be since the main reservoir is under higher exposure and uses river water for artificial infiltration to the groundwater. Oxygen- and hydrogenisotopes have been shown to be useful for tracking and locating surface water infiltration in groundwater intended for drinking water.
CO2 capture is essential for both mitigating CO2 emissions and purifying/conditioning gases for fuel and chemical production. To further improve the process performance with low environmental impacts, different strategies have been proposed, where developing liquid green absorbent for capturing CO2 is one of the effective options. Ionic liquids (IL)/deep eutectic solvents (DES) have recently emerged as green absorbents with unique properties, especially DESs also benefit from facile synthesis, low toxicity, and high biodegradability. To promote their development, this work summarized the recent research progress on ILs/DESs developed for CO2 capture from the aspects of those physical- and chemical-based, and COSMO-RS was combined to predict the properties that are unavailable from published articles in order to evaluate their performance based on the key properties for different IL/DES-based technologies. Finally, top 10 ILs/DESs were listed based on the corresponding criteria. The shared information will provide insight into screening and further developing IL/DES-based technologies for CO2 capture.
Since energy efficiency in comminution of ores is as small as 1% using a mechanical crushing process, it is highly demanded to improve its efficiency. Using electrical impulses to selectively liberate valuable minerals from ores can be a solution of this problem. In this work, we developed a simulation method using equivalent circuits of granite to better understand the crushing process with high-voltage (HV) electrical pulses. From our simulation works, we calculated the electric field distributions in granite when an electrical pulse was applied. We also calculated other associated electrical phenomena such as produced heat and temperature changes from the simulation results. A decrease in the electric field was observed in the plagioclase with high electrical conductivity and void space. This suggests that the void volume in each mineral is important in calculating the electrical properties. Our equivalent circuit models considering both the electrical conductivity and dielectric constant of a granite can more accurately represent the electrical properties of granite under HV electric pulse application. These results will help us better understand the liberation of minerals from granite by electric pulse application.
Characterization of heterogeneous materials, such as particles from mechanically processed waste printed circuit boards, is a challenging task. The majority of characterization methods either give average information or information that is very limited and in a tiny area of specific interest. That said, capturing such heterogeneity is significantly important for any kind of processes. Degree of liberation, indicating how much the target component is liberated from the non-valuable components, is a key property to determine the success of subsequent process for valuable material recovery. This work analyzed the degree of liberation of metals within the products of hammer milling process via the combination of image acquisition and analysis. The digital microscope and a scanning electron microscope (SEM) coupled with the energy dispersive spectroscopy (EDS) were used for image acquisition and elemental mapping, in order to evaluate the selective liberation under different milling conditions (i.e., feed mass, milling time) for different metals (mainly Cu and Al) and particle size fractions. The obtained liberation degree was also modelled and determined the liberation parameters that were compared. The results showed that the degree of liberation significantly depend on the milling conditions and metals we analyzed, and well correlated with the selective metal enrichment behavior. Results between the two methods showed some similarities and discrepancies. The advantages and disadvantages of the above two methods were identified and discussed in the paper, in addition to their methodological developments.