Waste Management & Research: The Journal for a Sustainable Circular Economy

The paper investigates various approaches to an environmental policy regarding drinks containers in Georgia. Currently, most of the waste containers are landfilled or pollute the environment through littering, and separate collection and recycling of drinks containers are almost nonexistent.

The Association Agreement with the EU, which entered into force in July 2016, stipulates the development of up-to-date waste management activities in this transition country.

In accordance with the legal framework, this mini-review proposes an EPR policy for Georgia, based on the waste hierarchy. Various approaches for such an EPR policy are reviewed as regards their feasibility for a transition country, but in particular with regard to incentive compatibility: the policy should guide producers and consumers to comply with the regulations. Some cost estimates demonstrate the financial feasibility of the recommended solution. Practical experiences from Austria, Bulgaria, France and Germany provide a European context.

In this paper, the effect of particle size on the physico-chemical, mineralogical, and leaching behavior of Indian fly ash was studied. Experiments were carried out to study the leaching of different elements such as Mg, Cr, Zn, Pb, Mn, Fe, Cu, Co, Mo, and Ni from Indian fly ash. During the experiments, the liquid-to-solid (L/S) ratio of the fly ash was taken as 9/1, 8/2, 7/3, 3/2, 1/1, and 2/3. The effect of four different particle size ranges (below 53, 53–75, 75–106, and 106–150 μm) of fly ash was analyzed. The ASTMD-3987 method was used to analyze the presence of trace elements from fly ash. In the ASTM D-3987 method, distilled water was used for extraction of leachate. Fly ash slurry samples were agitated in a lubricating type temperature-controlled Remi orbital shaker for a time duration of 18 hours with speed of 100 revolutions per minute (rpm) at a temperature of 25ºC. Distilled water does not save cost as well as being easily available. The leaching test of trace elements from fly ash was investigated at different pH conditions in order to predict the environmental effect from the ash disposal on the groundwater quality. Results revealed that pH of slurry suspension increases with increase in particle size. The pH value of fly ash slurries was negligibly affected by the decrease in L/S ratio for all particle sizes. Fine particles of fly ash produce a more harmful effect as compared to the coarser range of fly ash particles.

This paper presents some of the results obtained in a research project focused on the use of paint sludge (PS) as a modifying agent in the production of bituminous binders for paving applications. The scope of the project was to provide an innovative, sustainable and profitable solution to waste management problems which automotive industries have to face worldwide as a result of the production of PS. The authors applied for a patent which defines the industrial process for the production of PS modified binders (PSMBs). Measurements and analyses which were considered relevant for the assessment of technological feasibility included evaluation of: PS physical characteristics, PSMB high-temperature viscosity and PSMB storage stability. Environmental issues were addressed by considering PS chemical composition, gaseous emissions during PSMB production, and leaching behavior of bituminous mixtures containing PSMBs. Obtained results show that with a proper adaptation of the PSMB production process (i.e., PS drying at a higher temperature than 105°C) it is possible to comply with technological and environmental requirements such as those related to storage stability and to gaseous emissions during PSMB production and laying of bituminous mixtures. Leaching tests, aimed to evaluate runoff water quality, show no substantial difference in the release of substances in water between standard bituminous mixtures and bituminous mixtures prepared with PSMBs.

Sustainable utilisation of solid waste has been influenced by the increasing population of the world. Benefits of using solid waste based on natural fibre in polymer material are biodegradability and cost effectiveness. In poultry farms, chicken poultry, one of the slaughterhouse wastes is confronted with 30 10⁶ kg of waste per year in Turkey. The evaluation of this waste, which is quite rich in keratin, is extremely important both for the solution of the waste problem and for maintaining a clean environment, bringing this valuable material to the economy. These fibres are stable, durable and biodegradable because they have a crystalline structure. However, this valuable waste will have a positive effect when used together with boron minerals, which both increase the mechanical properties, flame retardancy and biodegradation of composite material. In this study, it is the aim to manufacture superior polyester-based composite materials reinforced with three kinds of boron minerals, such as boron oxide, borax pentahydrate, borax decahydrate and fibres recycled from waste chicken feathers. The effect of different filling ratios of filling materials on the mechanical and physical properties of composite materials was examined. Flame retardancy properties of the composites with best mechanical results were investigated. After pouring by means of the pre-casting process, the water absorption and swelling thickness of final products, as well as density, bending strength, flexural modulus, limiting oxygen index, thermogravimetric analysis and scanning electron microscope analysis, was performed. Mixing prescriptions and conditions with the best properties were determined.

In this study, the use of a dual-chamber microbial fuel cell for the production of bioelectricity from a food residue biomass (FORBI) product was investigated. Food residue biomass was produced by drying and shredding the pre-sorted fermentable fraction of household food waste collected door-to-door in the Municipality of Halandri, Athens, Greece. Different organic loads of food residue biomass expressed as chemical oxygen demand (COD) were examined (0.7, 0.9, 1.4, 2.8, 6 and 14 g COD L⁻¹, respectively). It was observed that an increase of the initial concentration of the final extract resulted in a corresponding increase in the operating time.

The microbial fuel cell potential increased from 33.3 mV to 46 mV as the concentration was increased from 0.7 to 14 g COD L⁻¹. The best performance in terms of maximum power density (29.6 mW m⁻²) corresponding to a current density of 88 mA m⁻² was observed for 6 g COD L⁻¹. Setting the external resistance at its optimal value (R_ext = 2 kΩ) as determined by polarisation experiments, P_yield drastically increased to 13.7 and 17.3 Joule (g FORBI)⁻¹ in two consecutive cycles. The results demonstrate that readily biodegradable substrates, such as food residue biomass, can be effectively used for enhanced bioelectricity harvesting in a microbial fuel cell.

Remediation of electronic gas CF₄ using commercially available technologies results in another kind of greenhouse gas and corrosive side products. This investigation aimed to develop CF₄ removal at room temperature with formation of useful product by attempting an electrogenerated Cu¹⁺[Ni²⁺(CN)₄]¹⁻ mediator. The initial electrolysis of the bimetallic complex at the anodized Ti cathode demonstrated Cu¹⁺[Ni²⁺(CN)₄]¹⁻ formation, which was confirmed by additional electron spin resonance results. The degradation of CF₄ followed mediated electrochemical reduction by electrogenerated Cu¹⁺[Ni²⁺(CN)₄]¹⁻. The removal efficiency of CF₄ of 95% was achieved by this electroscrubbing process at room temperature. The spectral results of online and offline Fourier transform infrared analyzer, either in gas or in solution phase, demonstrated that the product formed during the removal of CF₄ by electrogenerated Cu¹⁺[Ni²⁺(CN)₄]¹⁻ by electroscrubbing was ethanol (CH₃CH₂OH), with a small amount of trifluoroethane (CF₃CH₃) intermediate.

The management of disposed waste in illegal landfills (ILs) is a significant problem in contemporary societies due to respective hazards for the environment and human health. This paper presents a characterisation of ILs on the islands of La Palma (LP) and Gran Canaria (GC) based on multivariable statistical analysis. Inspection of numerous sites on both islands revealed a total of 153 and 286 ILs on LP and GC, respectively. A geospatial database was created composed of different potentially explanatory features of different typology (177): waste type, control and vigilance, socioeconomic, accessibility, distance to elements of interest, visibility and physical. The degree of association between the explanatory features and the occurrence of ILs was analysed with the support of exploratory statistics and the multivariable analysis techniques of principal component analysis (PCA) and binary logistic regression (LR). PCA explained 82.34% and 81.83% of total data variance in LP and GC, respectively, considering 7 and 6 components (Kaiser–Mayer–Olkin; LP: 0.715; GC: 0.711). The LR models for LP and GC had an overall accuracy of 93.5% and 92.5%. In LP and GC, 6 of 23 features and 9 of 21 features were, respectively, selected. The features most associated with the occurrence of ILs were: in LP, building density, distance to agricultural spaces and distance to green zones; in GC, the industrial activity indicator, density of ground use transition to artificial covers, density of greenhouses and distance to communication routes.

This short communication focuses on the potential use of paper sludge ash, a waste product of the paper making industry, as an innovative binder partially replacing cement in concrete with glass aggregate. After preliminary testing using binary or ternary CEM-II mixes with paper sludge ash/pulverised fly ash, a suitable mix for concrete with glass aggregate was identified. Concrete mixes with partial or full natural sand replacement by waste glass aggregate were then produced and showed appropriate strengths and overall similar or better water absorption characteristics than control mixes with natural aggregates, without manifest alkali-silica reaction problems. This shows potential for applications in precast dry mix concrete units based on the required strengths that were achieved.

Chemical ground improvement of soils of poor quality for construction has been increasingly used as a means of promoting sustainable construction practices. The production of conventional soil stabilisers such as cement or lime involves non-renewable natural resource and energy consumption and high carbon dioxide emissions; therefore, alternative stabilisers are sought. This study used waste paper sludge ash (PSA) to treat three different clays. The aim was to assess PSA effectiveness as an alternative to lime or cement for clay stabilisation based on plasticity characteristics, unconfined compressive strength (UCS), water retention and volumetric stability. PSA-treated soil specimens were shown to perform well compared to lime-treated or cement-treated ones: (a) PSA considerably lowered the plasticity indices of the two expansive clays, in a similar way as lime; (b) in most cases PSA dosages equal to or greater than the initial consumption of lime gave UCS at least twice as high compared to those obtained using commercial limes at equivalent dosages (> 1 MPa for the two expansive soils after 7 or 28 days of curing) and in the inspected cases also higher UCS than cement; and (c) consistently with the plasticity results PSA-treated specimens swelled less during wetting and had lower volumetric strains upon drying (better volumetric stability) compared to lime-treated or cement-treated soils. Overall the results give promise for a valorisation route of this waste material in the field of ground improvement.

In order to obtain the kinetic parameters during typical medical waste pyrolysis, the typical medical waste is pyrolysed in a micro-fluidised bed reactor. The gases evolved from the typical medical waste pyrolysis are analysed by a mass spectrometer, and only H₂, CH₄, C₂H₂, C₂H₄, C₂H₆, C₃H₆, C₃H₈ and C₄H₄ are observed. According to the gaseous product concentration profiles, the activation energies of gaseous formation are calculated based on the Friedman approach, and the average activation energies of H₂, CH₄, C₂H₂, C₂H₄, C₂H₆, C₃H₆, C₃H₈ and C₄H₄ formation during typical medical waste pyrolysis are in sequence as 65.10, 39.98, 35.17, 38.71, 40.75, 41.79, 58.57 and 63.95 kJ mol⁻¹. Moreover, the activation energy with respect to the gases mixture formation is 52.70 kJ mol⁻¹. Hence, it is concluded that the activation energy of typical medical waste pyrolysis is 52.70 kJ mol⁻¹. The model-fitting method is used to determine the mechanism model of medical waste pyrolysis. The results indicate that the chemical reaction (n = 1) model (G(x) = –ln(1–x)) is the optimum.

The recycling of metallic iron is commonly the first step to fully use the converter slag, which is the biggest waste discharge in the steelmaking process. This study presents a proposed improved process of separating metallic iron from vanadium-bearing converter slag more efficiently. The mineralogical and morphological characteristics of the converter slag were first investigated, and the results showed that most of the iron was incorporated in the spinel and olivine. Grinding, sieving and magnetic separation were combined to recover metallic iron from the converter slag, and yielded approximately 41.5% of iron in which the iron content was as high as 85%, and the non-magnetic concentrate contains 8.56% vanadium with a yield of 95.3% and 8.63% titanium with a yield of 85.3%. The magnetic part can be used as the raw materials in the steel making process, whereas the non-magnetic part can be used as the raw materials for the further extraction of vanadium.

Wild Scotch broom (Cytisus scoparius (L.) Link) shrubs are widely distributed throughout the world and, in some countries, are considered to be a threat to other plant species. The use of plant biomass from Scotch broom as a fertiliser seems to be the optimum solution for its disposal because it contains considerable amounts of macronutrients. However, its direct application to soils may cause phytotoxicity due to the release of polyphenols, which could negatively affect crop growth. This study evaluated the efficiency of vermicomposting in processing this leguminous plant on an industrial scale. Vermicomposting substantially reduced the biomass of Scotch broom (by 84%), mainly as a result of the loss of volatile solids. Simultaneously, the initial population of earthworms (Eisenia andrei) increased remarkably throughout the process, offering the possibility of obtaining earthworm protein for animal feed. A nutrient-rich and stabilised peat-like material without polyphenol-associated phytotoxicity was obtained after 42 days of vermicomposting. Lower values of microbial biomass and activity, indicative of stabilised materials, were recorded at the end of the trial. These findings suggest that vermicomposting is an environmentally sound management system for Scotch broom and could easily be scaled up for industrial application.

In recent years, researchers focused their attention on biogas production more than ever to meet the energy demand. Especially, biogas obtained from algal wastes has become a trending research area owing to the high content of volatile solids in algae. The main purpose of this study is to determine the biogas production potential from algal wastes and examine the effect of temperature and particle size parameters on biogas yield. A comparison was made between the biogas production potential of microalgal wastes, obtained after oil extraction, and macroalgal wastes collected from coastal areas. It was found that algal biogas yield is directly proportional to temperature and inversely proportional to particle size. Optimal conditions for biogas production from algal wastes were determined as the temperature of 55 °C, a particle size of 200 μm, a residence time of 30 days and an alga–inoculum ratio of 1:4 (w:w). Highest biogas yield obtained under these conditions was found as 342.59 cm³ CH₄ g⁻¹ VS with Ulva lactuca. Under thermophilic conditions, both micro- and macroalgal biogas yields were comparable. It can be concluded that algal biomass is a good source for biogas production, although further research is needed to increase biogas yield and quality.

The mesophilic reactor (MR) exhibited advantages in biogas production and performance stability over thermophilic reactor (TR) during the long-term anaerobic digestion (AD) of food waste (FW) with stepwise organic loading rate elevating. It was interesting to explore the mechanism causing the divergences in performances between these two reactors. The microbial activity was compared on day 110 when TR began to deteriorate. The results show that MR had significantly higher specific acetoclastic methanogenic activities (SAMA) and specific propionate and butyrate oxidative activities (SPOA and SBOA) than TR. The SAMA, SPOA and SBOA in TR were only 50.3%, 18.6% and 46.4% of those values in MR, respectively. Remarkably, the specific hydrogenotrophic methanogenic activity of 15.5±2.1, 15.7±4.6 mmol CH₄·L⁻¹ original slurry·d⁻¹ in MR and TR was comparative with insignificant difference, which indicates that the microbial activity in TR had been inhibited widely apart from the hydrogenotrophic methanogenesis. Additionally, many particles with the diameters of 1–2 mm were observed to form in MR and identified as complexes of calcium and long chain fatty acids (LCFAs). The formation of calcium crystallization might alleviate the inhibition of LCFAs during AD of FW, which further supports the better performance in MR than TR.

The population of the Earth is moving towards urban areas forming smart cities (SCs). Waste management is a component of SCs. We consider a SC which contains a distribution of waste bins and a distribution of waste trucks located in the SC sectors. Bins and trucks are enabled with Internet of Things (IoT) sensors and actuators. Prior approaches focus mainly on the dynamic scheduling and routing issues emerging from IoT-enabled waste management. However, less research has been done in the area of the stochastic reassignment process during the four seasons of the year over a period of two years. In this paper we aim to stochastically reassign trucks to collect waste from bins through time. We treat this problem with a multi-agent system for stochastic analyses.