Influence of leaching conditions for ecotoxicological classification of ash

The Waste Framework Directive (WFD; 2008/98/EC) states that classification of hazardous ecotoxicological properties of wastes (i.e. criteria H-14), should be based on the Community legislation on chemicals (i.e. CLP Regulation 1272/2008). However, harmonizing the waste and chemical classification may involve drastic changes related to choice of leaching tests as compared to e.g. the current European standard for ecotoxic characterization of waste (CEN 14735). The primary aim of the present study was therefore to evaluate the influence of leaching conditions, i.e. pH (inherent pH (～10), and 7), liquid to solid (L/S) ratio (10 and 1000 L/kg) and particle size (<4 mm, <1 mm, and <0.125 mm), for subsequent chemical analysis and ecotoxicity testing in relation to classification of municipal waste incineration bottom ash. The hazard potential, based on either comparisons between element levels in leachate and literature toxicity data or ecotoxicity testing of the leachates, was overall significantly higher at low particle size (<0.125 mm) as compared to particle fractions <1 mm and <4 mm, at pH 10 as compared to pH 7, and at L/S 10 as compared to L/S 1000. These results show that the choice of leaching conditions is crucial for H-14 classification of ash and must be carefully considered in deciding on future guidance procedures in Europe.     

An ecotoxicological approach for hazard identification of energy ash

Within the EU, ash should be classified by its inherent hazardous effects under criterion H-14 (ecotoxic) in the Directive on waste (2008/98/EC). Today, however, there are no harmonized quantitative criterions for such a classification, but it is stated that biological test systems can be used. In this study seven ash materials were leached and characterized, both biologically and chemically. The objectives were to evaluate if (a) clear concentration-response relationships could be achieved for the selected toxicity tests (bacteria, algae, crustacean and fish), (b) some test(s) are generally more sensitive and (c) the toxic responses were consistent with the chemical analyzes. Interestingly, our results indicate that high concentrations of non-hazardous components (Ca, K) influenced the toxicity of almost all ash eluates, whereas hazardous components (e.g. Zn, Pb) only influenced the toxicity of the eluates ranked as most hazardous. If considering both hazardous and non-hazardous substances, the observed toxic responses were relatively consistent with the chemical analyzes. Our results further showed that the (sub)chronic tests were much more sensitive than the acute tests. However, the use of extrapolation factors to compensate for using the less sensitive acute tests will likely lead to either over- or underestimations of toxicity. Our recommendation is therefore that classification of waste according to H-14 should be based on (sub)chronic test data. Finally, given that treatment of the eluates prior to toxicity testing has a major significance on the concentration and speciation of released substances, further studies are needed in order to propose a relevant testing scheme.     

Characterization of bottom ash in municipal solid waste incinerators for its use in road base

Incineration of municipal solid wastes (MSWs) produces by-products which can be broadly classified as bottom and fly ashes. Since MSW incineration started, possibilities other than landfilling the incineration residues have been sought; most initiatives in this sense tend to use these residues as aggregate substitute in pavements and other road construction elements. The main goal of the present work is the physical and chemical characterization of the local incineration bottom ash towards its eventual re-utilization. The study includes not only the specific aspects regarding its role as pavement element, but also the assessment of the environmental effects. Therefore, together with the determination of physical (moisture content, apparent and bulk densities, crystallinity, etc.) and engineering properties (particle size distribution, abrasion and impact resistance, etc.), full chemical characterization of the bottom ash and the study of leaching as a function of aging time have been undertaken. The results obtained indicate that the metal content of both the raw bottom ash and its leachates fulfill the environmental regulations provided that the bottom ash is stored for at least one month. Engineering properties of the bottom ash are close to those of natural aggregates and, thus, road-construction use of these residues seems to be feasible.     

Leaching from MSWI bottom ash: evaluation of non-equilibrium in column percolation experiments

Impacts of non-equilibrium on results of percolation experiments on municipal solid waste incineration (MSWI) bottom ash were investigated. Three parallel column experiments were performed: two columns with undisturbed percolation and one column with two sets of 1-month-long flow interruptions applied at liquid-to-solid (L/S) ratios of L/S 2L/kg and 12L/kg, respectively. Concentrations of Na, K, Cl(-), Ca, Si, SO(4)(2-), Al, Cu, Ni, Mo, Ba, Pb, Zn, and dissolved organic carbon (DOC) were monitored throughout the entire leaching period; geochemical modeling was used to identify non-equilibrium-induced changes in the solubility control. Despite both physical and chemical non-equilibrium, the columns were found to provide adequate information for readily soluble compounds (i.e., Na, Cl(-), and K) and solubility-controlled elements (i.e., Ca, SO(4)(2-), Ba, Si, Al, Zn, and Pb). The leaching of Cu and Ni was shown to depend strongly on DOC leaching, which was likely affected by physical non-equilibrium during flow interruptions. Consequently, the leaching of Cu and Ni in the undisturbed columns was shown to be by about one order of magnitude lower compared with the interrupted column. The results indicate that the leaching of DOC-related metals in laboratory column experiments may be considerably underestimated compared with full-scale scenarios in which the impacts from non-equilibrium may be significantly lower. The leaching of Mo (or MoO(4)(2-)) may be controlled solely by its availability in the mobile zone, which in turn appeared to be controlled by diffusion from the stagnant zone; no Mo controlling minerals were predicted by the geochemical modeling.     

Towards zero industrial waste: Utilisation of brick dust waste in sustainable construction

Laboratory investigations were carried out to establish the potential utilisation of brick dust (BD) in construction. The dust is a waste material from the cutting of fired clay bricks. Currently, the disposal of the dust is a problem to the brick fabrication company, and hence an environmental pollution concern. The dust was stabilised either used on its own or in combination with Pulverised Fuel Ash (PFA), a by-product material from coal combustion. The traditional stabilisers of lime and/or Portland Cement (PC) were used as controls. The main aim was to use a sustainable stabiliser material, where these stabilisers were partially replaced with Ground Granulated Blastfurnace Slag (GGBS), a by-product material from steel manufacture. Compacted cylinder test specimens were made at typical stabiliser contents and moist cured for up to 56 days prior to testing for compressive and California Bearing Ratio (CBR) strength tests, and to linear expansion during moist curing and subsequent soaking in water. The results obtained showed that partial substitution of the dust with PFA resulted in stronger material compared to using it on its own. The blended stabilisers achieved better performance. These results suggest technological, economic as well as environmental advantages of using the brick dust and similar industrial by-products to achieve sustainable infrastructure development with near zero industrial waste.     

Artificial carbonation for controlling the mobility of critical elements in bottom ash

In municipal solid waste incineration (MSWI), bottom ash, generated at a stoker grate type incinerator, the critical elements were identified in terms of EU regulation. The stabilizing effect of moderate carbonation (pH 8.28 ± 0.03) on critical contaminants was studied through availability and diffusion leaching protocols. Data from the performed tests were evaluated with the goal of reusing MSWI bottom ash as secondary construction material. To investigate the mobilizing effect of CO₂, suspended MSWI bottom ash was severely carbonated (pH 6.40 ± 0.07). The effect of CO₂ and its interaction with other leaching factors, such as liquid/solid (L/S) ratio, leaching time, pH, ultrasound treatment, and leaching temperature, were examined using a reduced 2^6-1 experimental design. Contaminants identified as critical were Cr, Cu, Mo, Sb, Cl⁻, and SO₄ ²⁻. Although moderate carbonation decreased the release of Cr, Cu, Mo, and Sb from compacted bottom ash, the main disadvantage remains its inability to demobilize Cl⁻ and SO₄ ²⁻. The hypothesized mobilizing effect of severe carbonation was proven. The treatment enhanced the separation of critical components (α = 0.05) (except for Cl⁻), i.e., about fivefold for Sb and about twofold for Cr, Cu, and S. Nevertheless, the prospect is good that severe carbonation could constitute the deciding key parameter to facilitate the technical feasibility of a future washing process for MSWI bottom ash.     

Preparation and characterization of sorbents prepared from ash (waste material) for sulfur dioxide (SO2) removal

Sorbents synthesized from various types of ash (coal fly ash, coal bottom ash, oil palm ash, and incinerator ash) for flue gas desulfurization were investigated. The sorbents were prepared by mixing the ashes with calcium oxide and calcium sulfate using the water hydration method. The effects of various sorbent preparation variables, such as the hydration period, the ratio of calcium oxide to ash, and the amount of calcium sulfate, on the Brunauer-Emmett-Teller (BET)-specific surface area of the resulting sorbent were studied using a two-level full factorial design. The surface area of the sorbents obtained range from 15.4 to 122.1m²/g. Regression models were developed to correlate the significant variables to the surface area of the sorbents. An analysis of variance (ANOVA) showed that the model was significant at a confidence level of 95%. It was found that apart from all the individual variables studied, interactions between variables also exerted a significant influence on the surface area of the sorbent. From the activity test results, it was found that sorbents prepared from coal fly ash and oil palm ash have the highest SO₂ absorption capacity. Scanning electron microscope (SEM) analysis showed that the sorbent was composed of a compound with a high structural porosity, while an X-ray diffraction spectrum showed that calcium aluminum silicate hydrate compounds are the main products of the hydration reaction.     

Monotonic aspects of the mechanical behaviour of bottom ash from municipal solid waste incineration and its potential use for road construction

Municipal solid waste incineration (MSWI) bottom ash is an atypical granular material because it may include industrial by-products that result from the incineration of domestic waste. The prospects for the beneficial use of this particular material mainly lie in the field of road construction, as a substitute for the traditional natural aggregates. However, its mechanical properties are still little known, particularly in term of stiffness and deformability, characteristics that are essential to the construction of a durable roadway. The purpose of this paper is to describe better the mechanical behaviour of this recycled material. In order to reach this objective, a large experimental campaign is presented. The first part of this paper presents and comments in detail on the results obtained from static monotonic tests. Oedometric and triaxial shear tests were performed on MSWI bottom ash both before and after treatment with a specific hydraulic binder. These tests allow specification of the mechanical characteristics of the MSWI bottom ash, such as the initial Young's modulus, Poisson's ratio, the compressibility index, the friction angle, and the contracting or dilating behaviour of the material. The results reveal a mechanical behaviour similar to that of initially dense standard materials (sands, unbound granular materials) and a dependence on the applied average pressure, characteristic of the mechanical behaviour of granular media. More laboratory data on other samples of MSWI bottom ash are required to ensure that this comparison is statistically valid.     

Concentrations of heavy metals in fly ash from a coal-fired power plant with respect to the new Finnish limit values

In Finland, the new limit values for heavy metals in fertilizers used in agriculture and in forestry came into force in March 2007, and for materials used as earth construction agents, in June 2006. From the utilization point of view, it was notable that the total heavy metal concentrations (Cd, Cu, Pb, Cr, Mo, Zn, As, Ni, Ba, and Hg) in fly ash from a coal-fired power plant were lower than those limit values. The concentrations of the easily soluble elements Ca, Mg, Na, P, and Zn in the fly ash were between 3.5 and 35 times higher than those found in the coarse mineral soils of Finland. Fly ash is a potential agent for soil remediation and for improving soil fertility. If inorganic materials and by-products are utilized in earthworks, the content of harmful compounds must be low and the harmful components must be tightly bound to the matrix. Therefore, a five-stage sequential extraction procedure was used to evaluate the extractability of different elements in fly ash into the following fractions: (1) the water-soluble fraction, (2) the exchangeable fraction (CH₃COOH), (3) the easily reduced fraction (NH₂OH-HCl), (4) the oxidizable fraction (H₂O₂ + CH₃COONH₄), and (5) the residual fraction (HF + HNO₃ + HCl).     

Use of co-combustion bottom ash to design an acoustic absorbing material for highway noise barriers

The present study aims to determine and evaluate the applicability of a new product consisting of coal bottom ash mixed with Portland cement in the application of highway noise barriers. In order to effectively recycle the bottom ash, the influence of the grain particle size of bottom ash, the thickness of the panel and the combination of different layers with various particle sizes have been studied, as well as some environmental properties including leachability (EN-12457-4, NEN-7345) and radioactivity tests. Based on the obtained results, the acoustic properties of the final composite material were similar or even better than those found in porous concrete used for the same application. According to this study, the material produced presented no environmental risk.     

The evaluation of an analytical protocol for the determination of substances in waste for hazard classification

The classification of waste as hazardous could soon be assessed in Europe using largely the hazard properties of its constituents, according to the the Classification, Labelling and Packaging (CLP) regulation. Comprehensive knowledge of the component constituents of a given waste will therefore be necessary. An analytical protocol for determining waste composition is proposed, which includes using inductively coupled plasma (ICP) screening methods to identify major elements and gas chromatography/mass spectrometry (GC–MS) screening techniques to measure organic compounds. The method includes a gross or indicator measure of ‘pools’ of higher molecular weight organic substances that are taken to be less bioactive and less hazardous, and of unresolved ‘mass’ during the chromatography of volatile and semi-volatile compounds. The concentration of some elements and specific compounds that are linked to specific hazard properties and are subject to specific regulation (examples include: heavy metals, chromium(VI), cyanides, organo-halogens, and PCBs) are determined by classical quantitative analysis. To check the consistency of the analysis, the sum of the concentrations (including unresolved ‘pools’) should give a mass balance between 90% and 110%. Thirty-two laboratory samples comprising different industrial wastes (liquids and solids) were tested by two routine service laboratories, to give circa 7000 parameter results. Despite discrepancies in some parameters, a satisfactory sum of estimated or measured concentrations (analytical balance) of 90% was reached for 20 samples (63% of the overall total) during this first test exercise, with identified reasons for most of the unsatisfactory results. Regular use of this protocol (which is now included in the French legislation) has enabled service laboratories to reach a 90% mass balance for nearly all the solid samples tested, and most of liquid samples (difficulties were caused in some samples from polymers in solution and vegetable oil). The protocol is submitted to French and European normalization bodies (AFNOR and CEN) and further improvements are awaited.     

燃煤电厂灰场环评技术评估中存在的问题与建议

在比较我国一般工业固体废物贮存处置场、生活垃圾填埋、危险废物贮存和危险废物填埋污染控制标准的基础上,结合欧共体和德国对固体废物的分类和填埋要求、德国灰场的防渗实例和我国燃煤电厂实际运行灰场对地下水的环境影响,分析了《一般工业固体废物贮存、处置场污染控制标准》(GB 18599-2001)存在的问题,并建议在干灰场环评技术评估中,燃煤电厂的灰渣和脱硫石膏除非按GB 5086规定方法进行浸出试验获得的浸出液中第一类污染物超过GB 8978最高允许排放浓度外,均应按第I类一般工业固体废物处理;同时对燃煤电厂的干灰场场址选择等方面的环保要求提出了建议.     

Evaluation of the use of a sequential extraction procedure for the characterization and treatment of metal containing solid waste

Metal containing wastes like MSWI fly ashes and blast furnace sludge form a major environmental problem as they are polluted with heavy metals. The ash has to be landfilled or can be used as a construction material, but a pretreatment is in general necessary. Washing of the ashes with water in order to dissolve soluble salts or extracting the heavy metals with chemicals are possibilities. Blast furnace sludge contains large quantities of iron and carbon and could be recycled in the blast furnace, if the zinc content were not that high. Using a hydrometallurgical process the zinc can be removed from the sludge particles. In order to evaluate such treatment methods knowledge of the leaching behaviour of the studied material is very important. One of the factors influencing the leaching behaviour is the composition and mineralogy of the solids. A sequential extraction procedure, whereby the material is sequentially leached with different leaching solutions, can be used as an aid to characterize the material and to determine which chemical conditions are needed to obtain a sufficient extraction efficiency. To verify the accuracy of the sequential extraction procedure, a method is tested on MSWI fly ash and evaluated by comparing the results with those of leaching experiments whereby the final pH of the leaching solutions is varied over a wide range. Based upon this evaluation some suggestions for the use of the sequential extraction procedure are made and an adapted procedure is suggested, and applied to a blast furnace sludge.     

Impacts of natural weathering on the transformation/neoformation processes in landfilled MSWI bottom ash: a geoenvironmental perspective

Natural weathering processes are significant mechanisms that noticeably affect the fundamental nature of incineration ash residues. To provide a greater understanding of these processes, a MSWI (mono)landfill site in the north east of the US was selected as the target for systematic investigation of the natural weathering of bottom ash residues. Samples of various ages were collected from locations A (1 yr), B (10 yrs), C (13-14 yrs) and D (20 yrs) of the landfill in 2009. We investigated the phase transformation of the collected bottom ash particles, neoformation processes as well as the behavior and distribution of certain heavy metals (Cu, Pb, Zn, Ni, and Cr) in the neoformed phases using optical microscopy, SEM-EDX, and bulk examinations. Key findings: at the preliminary stage, the waste metallic particles (Al, Fe, and Cu) and unstable minerals such as lime, portlandite, ettringite and hydrocalumite convert to oxide and hydroxide (hydrate) phases, calcite, alumina gel and gypsum. At the intermediate stage, the decomposition of melt products including magnetite spinels and metallic inclusions is triggered due to the partial dissolution of the melt glass. At the longer time horizon it is possible to track the breakdown of the glass phase, the extensive formation of calcite and anhydrite, Al-hydrates and more stable Fe-hydrates all through the older ash deposits. Among the dominant secondary phases, we propose the following order based on their direct metal uptake capacity: Fe-hydrates>Al-hydrates>calcite. Calcite was found to be the least effective phase for the direct sorption of heavy metals. Based on overall findings, a model is proposed that demonstrates the general trend of ash weathering in the landfill.     

Incorporation of gypsum waste in ceramic block production: Proposal for a minimal battery of tests to evaluate technical and environmental viability of this recycling process

Civil engineering-related construction and demolition debris is an important source of waste disposed of in municipal solid waste landfills. After clay materials, gypsum waste is the second largest contributor to the residential construction waste stream. As demand for sustainable building practices grows, interest in recovering gypsum waste from construction and demolition debris is increasing, but there is a lack of standardized tests to evaluate the technical and environmental viability of this solid waste recycling process. By recycling gypsum waste, natural deposits of gypsum might be conserved and high amounts of the waste by-product could be reused in the civil construction industry. In this context, this paper investigates a physical property (i.e., resistance to axial compression), the chemical composition and the ecotoxicological potential of ceramic blocks constructed with different proportions of clay, cement and gypsum waste, and assesses the feasibility of using a minimal battery of tests to evaluate the viability of this recycling process. Consideration of the results for the resistance to axial compression tests together with production costs revealed that the best formulation was 35% of plastic clay, 35% of non-plastic clay, 10% of Portland cement and 20% of gypsum waste, which showed a mean resistance of 4.64 MPa. Energy dispersive X-ray spectrometry showed calcium and sulfur to be the main elements, while quartz, gypsum, ettringite and nacrite were the main crystalline compounds found in this formulation. Ecotoxicity tests showed that leachate from this formulation is weakly toxic toward daphnids and bacteria (EC_20% = 69.0 and 75.0, respectively), while for algae and fish the leachate samples were not toxic at the EC_50% level. Overall, these results show that the addition of 20% of gypsum waste to the ceramic blocks could provide a viable substitute for clay in the ceramics industry and the tests applied in this study proved to be a useful tool for the technical and environmental evaluation of this recycling process, bacterial and daphnid tests being more sensitive than algae and fish tests.     

Techno-economic evaluation of ultrasound and thermal pretreatments for enhanced anaerobic digestion of municipal waste activated sludge

To enhance the anaerobic digestion of municipal waste-activated sludge (WAS), ultrasound, thermal, and ultrasound + thermal (combined) pretreatments were conducted using three ultrasound specific energy inputs (1000, 5000, and 10,000 kJ/kg TSS) and three thermal pretreatment temperatures (50, 70 and 90 °C). Prior to anaerobic digestion, combined pretreatments significantly improved volatile suspended solid (VSS) reduction by 29-38%. The largest increase in methane production (30%) was observed after 30 min of 90 °C pretreatment followed by 10,000 kJ/kg TSS ultrasound pretreatment. Combined pretreatments improved the dimethyl sulfide (DMS) removal efficiency by 42-72% but did not show any further improvement in hydrogen sulfide (H₂S) removal when compared with ultrasound and thermal pretreatments alone. Economic analysis showed that combined pretreatments with 1000 kJ/kg TSS specific energy and differing thermal pretreatments (50-90 °C) can reduce operating costs by $44-66/ton dry solid when compared to conventional anaerobic digestion without pretreatments.     

Characterisation of major component leaching and buffering capacity of RDF incineration and gasification bottom ash in relation to reuse or disposal scenarios

Thermal treatment of refuse derived fuel (RDF) in waste-to-energy (WtE) plants is considered a promising solution to reduce waste volumes for disposal, while improving material and energy recovery from waste. Incineration is commonly applied for the energetic valorisation of RDF, although RDF gasification has also gained acceptance in recent years. In this study we focused on the environmental properties of bottom ash (BA) from an RDF incineration (RDF-I, operating temperature 850-1000 °C) and a RDF gasification plant (RDF-G, operating temperature 1200-1400 °C), by evaluating the total composition, mineralogy, buffering capacity, leaching behaviour (both at the material’s own pH and as a function of pH) of both types of slag. In addition, buffering capacity results and pH-dependence leaching concentrations of major components obtained for both types of BA were analysed by geochemical modelling. Experimental results showed that the total content of major components for the two types of BA was fairly similar and possibly related to the characteristics of the RDF feedstock. However, significant differences in the contents of trace metals and salts were observed for the two BA samples as a result of the different operating conditions (i.e. temperature) adopted by the two RDF thermal treatment plants. Mineralogy analysis showed in fact that the RDF-I slag consisted of an assemblage of several crystalline phases while the RDF-G slag was mainly made up by amorphous glassy phases. The leached concentrations of major components (e.g. Ca, Si) at the natural pH of each type of slag did not reflect their total contents as a result of the partial solubility of the minerals in which these components were chemically bound. In addition, comparison of total contents with leached concentrations of minor elements (e.g. Pb, Cu) showed no obvious relationship for the two types of BA. According to the compliance leaching test results, the RDF-G BA would meet the limits of the Italian legislation for reuse and the European acceptance criteria for inert waste landfilling. RDF-I BA instead would meet the European acceptance criteria for non hazardous waste landfilling. A new geochemical modelling approach was followed in order to predict the leaching behaviour of major components and the pH buffering capacity of the two types of slags on the basis of independent mineralogical information obtained by XRD analysis and the bulk composition of the slag. It was found that the combined use of data regarding the mineralogical characterization and the buffering capacity of the slag material can provide an independent estimate of both the identity and the amount of minerals that contribute to the leaching process. This new modelling approach suggests that only a limited amount of the mineral phases that control the pH, buffering capacity and major component leaching from the solid samples is available for leaching, at least on the time scale of the applied standard leaching tests. As such, the presented approach can contribute to gain insights for the identification of the types and amounts of minerals that control the leaching properties and pH buffering capacity of solid residues such as RDF incineration and gasification bottom ash.     

A model for estimation of potential generation of waste electrical and electronic equipment in Brazil

Sales of electrical and electronic equipment are increasing dramatically in developing countries. Usually, there are no reliable data about quantities of the waste generated. A new law for solid waste management was enacted in Brazil in 2010, and the infrastructure to treat this waste must be planned, considering the volumes of the different types of electrical and electronic equipment generated.This paper reviews the literature regarding estimation of waste electrical and electronic equipment (WEEE), focusing on developing countries, particularly in Latin America. It briefly describes the current WEEE system in Brazil and presents an updated estimate of generation of WEEE. Considering the limited available data in Brazil, a model for WEEE generation estimation is proposed in which different methods are used for mature and non-mature market products.The results showed that the most important variable is the equipment lifetime, which requires a thorough understanding of consumer behavior to estimate. Since Brazil is a rapidly expanding market, the “boom” in waste generation is still to come. In the near future, better data will provide more reliable estimation of waste generation and a clearer interpretation of the lifetime variable throughout the years.     

Household waste behaviours among a community sample in Iran: An application of the theory of planned behaviour

Understanding the factors influencing recycling behaviour can lead to better and more effective recycling programs in a community. The goal of this study was to examine factors associated with household waste behaviours in the context of the theory of planned behaviour (TPB) among a community sample of Iranians that included data collection at time 1 and at follow-up one year later at time 2. Study participants were sampled from households under the coverage of eight urban health centers in the city of Qazvin. Of 2000 invited households, 1782 agreed to participate in the study. A self-reported questionnaire was used for assessing socio-demographic factors and the TPB constructs (i.e. attitude, subjective norms, perceived behavioural control, and intention). Furthermore, questions regarding moral obligation, self-identity, action planning, and past recycling behaviour were asked, creating an extended TPB. At time 2, participants were asked to complete a follow-up questionnaire on self-reported recycling behaviours. All TPB constructs had positive and significant correlations with each other. Recycling behaviour at time 1 (past behaviour) significantly related to household waste behaviour at time 2. The extended TPB explained 47% of the variance in household waste behaviour at time 2. Attitude, perceived behavioural control, intention, moral obligation, self-identity, action planning, and past recycling behaviour were significant predictors of household waste behaviour at time 2 in all models. The fact that the expanded TPB constructs significantly predicted household waste behaviours holds great promise for developing effective public campaigns and behaviour-changing interventions in a region where overall rates of household waste reduction behaviours are low. Our results indicate that educational materials which target moral obligation and action planning may be particularly effective.