Inert Waste Research Articles

Landfill in a Sustainable Waste Disposal

Landfill is as old as mankind, and it is the most common and popular waste disposal globally; it is very likely to be the mostly used method for some time to come despite efforts to recycle and re-use waste materials. However, in many respects landfilling has been highly criticised by stakeholders and regarded as the opposite of sustainability because of the health hazard and environmental burden it constitutes. The efficiency of landfilling rests on technical, economic, and legal framework which seems to be inadequate in many countries. The essence of sustainable landfill is to ensure that the environmental parameters e.g., methane, leachate, etc. are reduced to acceptable risk level (inert waste) in order to prevent damage to humans and the environment. Many European countries in compliance with 2008/98/EC along with 94/62/EC Directive have been able to reduce heavy reliance on the landfill; however, this has raised the use of other waste management methods e.g., Sweden share of landfill disposal is 1% (Table I) this increases dependent on other methods of waste disposal e.g., incineration, 49%, waste treated biologically, 14% in 2011. Nevertheless, landfilling will still be required to dispose of waste which cannot be recycled or treated in other ways.

Physical and mechanical properties of waste ground at inert waste landfills.

The physical and mechanical properties of waste ground were examined at 14 locations across 4 inert waste landfills in Japan with the goal of establishing a safe and cost-effective design methodology specific to inert waste landfills. Composition analysis, basic physical properties, angle of repose, CASPOL impact value tests, and in situ direct shear tests were conducted. Inert wastes were comprised of three main components: fibrous, granular, and soil-like content, and their compositions varied between 3.6-54%, 13-45%, and 43-74%, respectively. As the fibrous content and age after reclamation increased, the water content increased but the percentage air voids decreased. The impact value (Ia), which is an indicator of the bearing capacity, increased as the dry density increased. For all locations, the angle of repose after avalanche (αa) was found between 34 and 44°. In direct shear tests, the cohesion (c) and internal angle of friction (φ) ranged from 2 to 21 kN/m2 and 22-59°, respectively. The shear stresses obtained from these c and φ values were higher than those for the municipal solid wastes, particularly for landfills with fibrous fractions ranging 14-31% under a normal stress of 25.55 kN/m2. c increased and φ decreased as the dry density increased. The correlation calculated for c and φ with Ia for inert waste landfill were c=4.10Ia-21.32 and φ = -4.61Ia+82.37. Finally, the utilization of the results obtained in this study is discussed in three design stages: planning, landfilling, and future expansion.

Storage facilities reclamation using dredged sediments from waterways: Growing media formulation for plants according to the EU Ecolabel requirements.

Dredged sediments display a great potential for growing media applications; however, there are few studies about their beneficial reuse for the waste storage reclamation. This research study aims at checking the agronomic values and environmental impacts of three growing media based on waterways sediments (WSs) and green waste (GW) according ecolabel requirements. For this purpose, three growing media named GW0, GW25, and GW50 were prepared at field pilot scale by co-composting WS and GWs during 12 months. Samples were submitted to ecolabel analyses package. Following to the ecolabel requirements, the growing media comply with criteria like pH, electrical conductivity, trace elements and polycyclic aromatic hydrocarbon contents, chlorides, and pathogens, whereas they are not in compliance with the EU Ecolabel guidelines for propagules, organic matter, and zinc contents. Results of laboratory leaching tests performed according to NF EN 12457-2 for GW0, GW25, and GW50 have shown that sulfates, soluble fraction exceed limit for inert waste storage. Lysimeter tests at pilot scale were performed during 6 months to check the leaching potential of pollutants from growing media under real field conditions, including a European ecolabel product. Results demonstrate that Ba, Mo, Sb, Zn, Se, and Sb are higher in GW0, GW25, and GW50 than in the European ecolabel. As, Cd, Cr, Ni, and F- are more soluble in the commercial product compared to other growing media. This study allowed to demonstrate that main characteristics are fulfilling for reusing these growing media in the specific field of waste storage reclamation.

Efficient treatment of mature landfill leachate with a novel composite biological trickle reactor developed using refractory domestic waste and aged refuse

Municipal solid waste classification is a major livelihood project, while the classified materials are deficiently utilized, especially the inert waste. In this study, a composite biological trickle reactor, packed with foam concrete, waste textile, animal bone and aged refuse, was developed for the treatment of mature landfill leachate, and the function of reaction factors were investigated systematically. Results indicated that under the optimum conditions with mixed filler, temperature of 30 °C, hydraulic loading of 40 L/(m3·d), and aeration rate of 1.8 L/(h·L), the average removal rates of chemical oxygen demand, total nitrogen, ammonia nitrogen and total phosphorus were 85.02%, 76.00%, 99.90% and 96.83%. The reactor presented well buffering performance after 100 days operation, with a slightly accumulation of organic and nitrogen substances. Biological analysis showed that the main phyla in all fillers were Actinobacteria and Proteobacteria. The microbial diversity and richness of waste textile were inferior to those of animal bone, aged refuse and foam concrete. In the operation system, the alternate aerobic–anoxic–anaerobic environment was structured, and the contaminants removal was due to the comprehensive function of adsorption, promotional biotreatment and chemical precipitation. All the results demonstrated that this novel trickle reactor was an excellent choice for leachate treatment because of the low cost and superior efficiency.

Multi-layer value stream assessment of the reverse logistics network for inert construction waste management

Reverse logistics (RL) concepts have brought sustainable solutions to the problems pertinent to inert construction waste (ICW) management. However, the involvement of different processes and facilities across the RL value chain makes it difficult to visualize and manage the whole process conveniently. Consequently, issues such as inadequate assessment of environmental hazards, unclear cost accrual patterns, misleading information to stakeholders, and other process-related deficiencies arise, thereby questioning the overall sustainability and alike circularity concepts. Despite the prominent role of lean management (LM) concepts in process improvements across various product-oriented sectors, its integration within RL management to solve ICW problems is almost non-existent. This paper presents a unique lean thinking-based multi-layer value stream assessment (MVSA) approach deriving from a conventional value stream mapping (VSM) technique to assess the overall RL network of ICW management. RL network design entails both facility-based and non-facility-based processes, with four different value streams, i.e., time, cost, environmental quality, and process efficiency aspects. A case study of Hong Kong demonstrates the developed MVSA approach. The case study features an assessment of the RL network's current and future states, considering multiple scenarios. Furthermore, a detailed sensitivity analysis is conducted to provide valuable insights and discussions. In the end, an agenda for continuous improvement related to the proposed MVSA approach is expounded. The research findings verify that the proposed MVSA approach can significantly contribute to the overall process improvement, better visualization, and RL network assessment, leading to effective waste management systems.

Synergism Red Mud-Acid Mine Drainage as a Sustainable Solution for Neutralizing and Immobilizing Hazardous Elements

Acid mine drainage (AMD) and red mud (RM) are frequently available in the metallurgical and mining industry. Treating AMD solutions require the generation of enough alkalinity to neutralize the acidity excess. RM, recognized as a waste generating high alkalinity solution when it is in contact with water, was chosen to treat AMD from South Africa at room temperature. A German and a Greek RM have been evaluated as a potential low-cost material to neutralize and immobilize harmful chemical ions from AMD. Results showed that heavy metals and other hazardous elements such as As, Se, Cd, and Zn had been immobilized in the mineral phase. According to European environmental standards, S and Cr, mainly present in RM, were the only two elements not immobilized below the concentration established for inert waste.

Analysis of Leachate Generation Dynamics in a Closed Municipal Solid Waste Landfill by Means of Geophysical Data (DC Resistivity and Self-Potential Methods)

The degradation of MSW in landfills occurs naturally from the beginning of the disposal, during landfill operation and even after its closure, over a period of several years. The monitoring of closed landfills can be quite costly when done only by direct methods, especially in areas where technical and financial resources are restricted. This work presents a case study in the extreme south of Brazil that represents the vast majority of landfills in the country: public landfills, in small ditches with little resources. The geophysical survey sought to identify leachate accumulation zones and verify their chemical stability in relation to the geological environment from the joint analysis of the electrical resistivity and self-potential data. Data acquisition took place on the same date (02/2018), with results that reveal leachate generation areas (−60 mV and ~ 30 Ωm), leachate accumulation (−40 mV and ~ 20 Ωm) and areas with a predominance of inert waste (> 40 mV), where previously existing organic matter was practically degraded. The combined use of geoelectric methods to understand the degradation dynamics of organic matter in landfills allows for the recognition of active zones of leachate generation, information that supports chemical stabilization projects and site remediation.

Analysis of durability (frost resistance) of MSWI fly ash modified cement composites

The research focused on effective utilisation of fly ash (FA) from municipal waste incineration plants. FA was found to have an effect on rheological characteristics (viscosity) of cement pastes, to suppress cement hydration processes. Evidence was obtained that up to 10% of FA in hardened cement paste and mortars does no impair compressive strength characteristics. XRD analysis and SEM tests revealed that FA modified cement composites contain Friedel salt compounds, which have an effect on frost durability of cement composites. Tests of heavy metal leakage from hardened cement paste showed that the amount of heavy metals leached from specimens containing 5–10% FA did not exceed the limit values of inert waste specified in Directive 2003/33/EC. Frost durability tests showed that FA can be utilised in the manufacturing of cement composites with improved durability properties.

Suitability of using borrow pit soils collected from Southwestern Nigeria as landfill liners

Effective waste disposal system is essential in preventing the infiltration of leachate into the groundwater and in achieving the sustainable development goal of ensuring clean water. One of the ways to provide an adequate disposal system is through the provision and use of engineered landfills for waste containment instead of open dumps. Consequently, this study evaluates the suitability of using soils from six borrow pits collected from six states in Southwestern, Nigeria. To assess the suitability of the soils, laboratory tests were carried out to determine the index properties, mechanical and hydraulic properties of the collected soil samples. The results showed that the soil samples collected from the selected borrow pits in Ogun, Oyo and Ekiti States could be effectively employed for the containment of inert waste. In contrast, the soil samples collected from the selected borrow pits in Osun, Lagos and Ondo States needs to be improved such that their unconfined compressive strengths satisfy the standard requirement (≥200 kN/m2). This study provides readily accessible soil data for use by engineering professionals involved in selecting suitable soil for use as landfill liners in Southwestern, Nigeri.

Investigating the bulk density of construction waste: A big data-driven approach

Construction waste contains inert (e.g., construction debris, rubble, earth, bitumen, and concrete) and non-inert materials (e.g., bamboo, plastics, wood, paper, and vegetation), while it is often a combination of the two when it is generated at source. The bulk density of construction waste is the yardstick information for many subsequent waste management efforts. One feasible way to derive the bulk density information is to segregate the mixture of inert and non-inert substances and examine their compositions, but clearly, this is an onerous task. This paper reports a data-driven approach to obtain the bulk densities of inert and non-inert construction waste by analyzing a big dataset of 4.9 million loads of construction waste in Hong Kong in the years 2017 to 2019. It is discovered that the means of bulk density are 336 kg/m3 for non-inert waste, 528 kg/m3 for mixed waste, and 991 kg/m3 for inert waste, and their coefficients of variation are 69%, 43%, and 29%, respectively. The research not only proved our heuristic rules concerning the bulk densities of the three generic types of construction waste, but also articulated, for the first time, their converged means and ranges. The findings can be used in adjusting the admission criteria as adopted in the governmental waste management facilities. Future research is recommended to further narrow down the bulk density ranges to provide more accurate references for construction waste management.

Assessment of the Odour Quality of the Air Surrounding a Landfill Site: A Case Study

In the present study, the authors assessed the odour quality of the air in the vicinity of a landfill site using a case study of a waste management plant that processes non-hazardous and inert waste as an example. An analysis of the impact of the facility under study on the odour quality of the air was performed based on a mathematical modelling system used to, among other things, assess the impact of investments in air quality both in Poland and worldwide. The most important element of the system is the puff dispersion model CALPUFF. In conclusion, the analysis of the plant’s odour impact clearly indicates a significant impact on the air quality in the studied area. The range of the impact may even reach up to 1.5 km; in the nearest locality, the odour perceptibility threshold may be exceeded for more than 3% of the hours in a year. However, taking into account the fact that the landfill is located within an agricultural area, the incidental odour impact in this area may also be associated with periods of intensive fertilization and a roadside ditch collecting municipal sewage from roadside households.

Generation, Composition and Management of Municipal Solid Waste at Rudraprayag, Garhwal Himalaya

The key objective of the current research effort was to investigate the generation and composition of the municipal solid waste and to assess the recent management practices for solid waste management. The study area was divided into nine wards and four zones on the basis of population size, their economic and living standards. The total solid waste generation during the study period was around 4-5 tonnes per day. The qualitative solid waste analysis of Rudraprayag reveals that it includes the biodegradable, non-biodegradable and inert waste. However, the quantitative solid waste analysis reveals that the highest generation of biodegradable waste was found in February (89.16 %) and lowest in May (79.06 %). Non-biodegradable waste was recorded highest during March (25.72 %) and lowest during June (7.73 %). The percentage of inert waste was maximum during April (2.87 %) minimum during June (0.037 %). The total waste generation was found maximum during February which was 5883.983 g. However, it was found minimum during May which was 2596.034 g.

Multi-stage network-based two-type cost minimization for the reverse logistics management of inert construction waste

The growing concerns for achieving sustainability has gained much attention from waste management experts with particular focus on reverse logistics, as it supports concepts like circular economy, material recovery, and improved environmental performances. This paper describes a multi-stage network-based model to minimize the overall cost for the reverse logistics management of inert construction waste across its entire life cycle. This model takes a unique two-type costing approach to overcome the ambiguities and deficiencies existing in previous models. Type-I cost refers to the facility-based costing (FBC) and Type-II cost refers to non-facility based costing (NFBC). The mixed-integer linear programming technique is applied using the LINGO software. A case study of construction waste management in Hong Kong is conducted to validate the developed model, which includes waste generation point as the starting node, public fill reception facility and recycling facility as an intermediate node, and landfill as an ending node. The result shows about 24% reduction in the total cost compared to the base case. Furthermore, to evaluate the impact of uncertainties on the cost parameters, a detailed scenario based sensitivity analysis is conducted. The optimal result shows that the larger portion of total cost come from the NFBC component. Therefore, NFBC is critical in defining the overall reverse logistics network and thus, should be given more emphasis in the design of an effective construction waste management system.

Mechanism of magnetizing the Bayer red mud and meanwhile improving the cementitious activity of its tailings by using biomass

Low-cost and harmless resource utilization of Bayer red mud (BRM) is a problem to be solved urgently. In this work, the effects of biomass as reductant and alteration agent on the hematite transformed into magnetite in BRM and cementitious activity of tailings (residue after extraction of iron components, abbreviated as REIC) were systematically investigated. The analyses were performed through XRF, XRD, TG, DSC, ICP-AES and compressive strength tests. The results showed that the activation energy of biomass pyrolysis was lower than 80 kJ mol−1. 650 °C was not only the temperature for biomass to completely reduce hematite to magnetite, but also the best thermal activation temperature of BRM. After magnetic separation, the iron ore concentrate with grade of 55.78% can be obtained, and the recovery rate of iron ore was 81.26%. The cementitious activity of REIC was significantly improved due to the increase of amorphous substances and small particles with loose structure. The compressive strength (28 d) of the cementitious material prepared by REIC and other solid wastes was 36.84 MPa, which was an eco-friendly material. This work can provide a new reference for the development and utilization of biomass, BRM, low-grade hematite and inert solid wastes, and shows the potential of biomass to save energy and reduce emissions in steel industry.

Trace Elements in Water-Soluble Fractions from Bulgarian Coal Fly Ashes and Their Technological and Environmental Importance

The composition of nine Bulgarian coal fly ashes (FAs) and concentrations of 69 elements in their water-soluble leachates were studied to elucidate the presence and associations of trace elements. Each FA or element has individual leaching behavior and is strongly dependent on the mineral composition of FAs, especially the abundance of water-soluble minerals among sulfates, oxyhydroxides, and carbonates, and, to a lesser extent, certain less soluble silicates, glass, and char. The water leachates have neutral to slightly alkaline pH values (7.2–7.7) and salty to brine total mineralization (0.6–9.0%). Most elements are insoluble in water or reveal insignificant (<0.1%) to low (0.1–0.9%) water extractable proportions from FAs. However, elements such as Ca, Cl, Li, Mg, Mo, Na, S, Sb, and Sr have significant (1–10%) to high (>10%) water-leaching proportions. Fourteen minor and trace elements, namely, As, B, Cr, Ge, Hg, Li, Mo, P, Rb, Sb, Sc, Sr, Ti, and V, have high to extremely high enrichment factors (10–1776 times) for FA water leachates in comparison with the Clarke values for surface water. The leaching behavior of these 14 elements was described due to their potential industrial interests. Another assemblage of elements in some FA leachates (Al, As, B, Ca, Cr, Fe, Hg, S, Sb, and Se) reveals contents higher than those of the water-quality guideline for drinking water. However, the FAs studied normally belong to inert wastes for landfilling (excluding Sb and Se for specific FAs and total dissolved solids) according to the waste acceptance criteria. Therefore, some FA leachates could provoke some environmental and health concerns during FA storage, weathering, and water processing.

Sürdürülebilirlik Açısından Mermer Atıklarının Karayolu İnşaatında Değerlendirilmesi: Ekonomik Analiz Örneği

Günümüzde mineral agrega kullanım alanları büyük bir hızla artmakta olmasına rağmen doğal agrega kaynakları giderek azalmaktadır. Buna karşılık ülkemizdeki mermer fabrikalarının atıklarının büyük bir kısmı değerlendirilememekte, işletme sahalarında veya yakınlarındaki depo alanlarında depolanmaktadır. Mermer işleme tesislerinde ham blokların işlenmesi ile ortaya çıkan artık miktarı genellikle %30 - %45 civarında olmaktadır. Mermer atıklarının yığınlar halinde biriktirilmesi hem çevreye olumsuz etkileri olmakta hem de ekonomik olarak kayıplara sebep olmaktadır. Bu çalışmada atık mermer agregasının yol üstyapısında temel tabakalarında doğal agrega yerine alternatif kullanımı düşünülerek, doğal malzeme ile mukayeseli olarak ekonomik analizi yapılmıştır. Çalışmada öncelikle atık malzemelerin ve doğal agreganın birim maliyetleri belirlenmiştir. Maliyet analizinde sökme - kırma - eleme – sınıflandırma - yükleme ve nakliye maliyetleri arasında olası senaryolar dikkate alınmıştır. Yapılan maliyet hesabı neticesinde mermer atıklarının ham madde maliyeti olmaması sebebiyle, birim maliyeti doğal agreganın %50’si kadar çıkmıştır. Elde edilen birim maliyet farklarından hareketle, sonuç olarak mermer agregasının ekonomik olarak taşınabileceği belirli bir mesafe (Me) belirlenmiştir. Başa baş mesafesi olarak bulunan bu uzaklığın göz ardı edilemeyecek ölçüde olduğu tespit edilmiştir.

Efficiency of Chemical and Biological Leaching of Copper Slag for the Recovery of Metals and Valorisation of the Leach Residue as Raw Material in Cement Production

Copper slags produced in vast quantities in smelting operations could be considered as secondary material sources instead of stockpiling them in landfills. This study investigates the recovery of valuable metals from copper slag and the valorisation of the leach residue as construction material in line with the principles of a circular economy. By taking into account that the environmental characterization of the as-received copper slag did not allow its disposal in landfills without prior treatment, chemical and biological leaching were tested for the recovery of metals. Pre-treatment with acids, namely HNO3 and H2SO4, resulted in the extraction of several target metals and the production of an almost inert waste. Despite the clearly better oxidative conditions prevailing in the bioleaching reactors, chemical leaching resulted in the higher dissolution of Cu (71% vs. 51%), Co (70% vs. 36%), and Zn (65% vs. 44%). The acid consumption was much lower during the bioleaching experiments compared to the chemical leaching. The bioleach residue was suitable for its use as supplementary cementitious material, showing a better performance than the reference sample without causing any detrimental effects to the calcium aluminate cement (CAC) quality. The complete valorisation of copper slags is expected to improve the economics of the process, by avoiding landfill costs and producing saleable products with high added value.

Sorting of suitable areas for disposal of construction and demolition waste using GIS and ELECTRE TRI

Inadequate construction and demolition waste disposal create severe environmental impacts in cities when it occurs in an uncontrolled manner. For waste with the possibility of recycling, the appropriate destination would be recycling plants or landfills. In the investigative process, no studies were found that considered the sorting procedure by compensatory and non-compensatory multi-criteria analysis integrated to the Geographic Information System to choose suitable landfills or recycling plants in cities. This study aims to fill this gap with a structured methodology for mapping suitable sites to receive inert waste from small and medium cities. For this, it was considered the identification of relevant criteria and weights definition by Analytic Hierarchy Process method and after performing a sorting procedure by ArcGIS 10.0 software (compensatory aspect) and ELECTRE TRI method (non-compensatory aspect). And then, an aggregate analysis in order to support the decision-making was also developed. An experimental study was carried out with the application of this methodology in a city of the south western of Parana, Brazil, allowing the analysis of criteria such as land use, soil type and slope, as well as distances to urban area, education and health institutions, roads and highways and hydrography network. We combined these data in a multi-criteria analysis to provide an aptitude mapping to identify suitable landfill areas with 5 km2, and sorted as low, medium and high aptitude classes by ArcGIS software and ELECTRE TRI method. With all that, it shows to be efficient, providing relevant practical and theoretical implications to this theme.

Greening effect of concrete containing granulated blast-furnace slag composite cement: Is there an environmental impact?

The “greening effect” refers to hardened concrete containing Granulated Blast-Furnace Slag (GBFS) that displays a vivid blue-green color after removal of formwork. This temporary coloration effect, which fades within a few days to weeks, has raised concerns about its potential impact on the environment. Three types of leaching tests were conducted to assess different potential release scenarios: a sprinkling test, a static monolith tank test and a batch test on crushed samples. Slag content was linked to a higher release of sulfur anions in the leachates, in the form of sulfides, thiosulfates and sulfates. Most of these anions came from the GBFS, where sulfur is mainly in the form of sulfides with thiosulfates and sulfates as the main products of sulfide oxidation. Sulfate levels, however, were lower than threshold limit values for both inert waste and alternate materials reused in road construction. Moreover, no chromium, or other hazardous metals, were detected in the leachates.

Material flow analysis and heavy hydrocarbon removal in a full-scale biopile and soil washing plant in northern Italy.

This study aimed to assess the mass fluxes and removal efficiencies of heavy hydrocarbons in a full-scale plant located in northern Italy. This plant receives and treats contaminated soil, soils and rocks from construction and demolition activities, incineration slags and street cleaning residues. The plant has three sections, consisting of bioremediation using biopile, a soil washing stage and a stabilization/solidification unit, which can perform independently or together with the others. The material flow analysis showed how the crisis in the construction industry changed the final destination of waste after the treatment: as the market demand for coarse material decreased, waste was sent directly to landfills for inert waste, instead of being recovered. Hydrocarbon mass fluxes showed that a considerable amount of pollutants was removed. In the period 2009-2014, the removal efficiencies of the bioremediation, the soil washing section and the entire plant were respectively 73%, 58% and 62%. The percentages of removal attained at the facility in study were sufficient to ensure the possibility of recovering the waste or disposing of it in different landfill categories, according to the national regulations.