A global prospective of income distribution and its effect on life cycle assessment of municipal solid waste management: a review

The crucial role of circular waste management systems in cutting waste leakage into aquatic environments

Waste leakage has become a major global concern owing to the negative impacts on aquatic ecosystems and human health. We combine spatial analysis with the Shared Socioeconomic Pathways to project future waste leakage under current conditions and develop mitigation strategies up to 2040. Here we show that the majority (70%) of potential leakage of municipal solid waste into aquatic environments occurs in China, South Asia, Africa, and India. We show the need for the adoption of active mitigation strategies, in particular circular waste management systems, that could stop waste from entering the aquatic ecosystems in the first place. However, even in a scenario representing a sustainable world in which technical, social, and financial barriers are overcome and public awareness and participation to rapidly increase waste collection rates, reduce, reuse and recycling waste exist, it would be impossible to entirely eliminate waste leakage before 2030, failing to meet the waste-related Sustainable Development Goals.

Prophet time series modeling of waste disposal rates in four North American cities

In this study, three different univariate municipal solid waste (MSW) disposal rate forecast models (SARIMA, Holt-Winters, Prophet) were examined using different testing periods in four North American cities with different socioeconomic conditions. A review of the literature suggests that the selected models are able to handle seasonality in a time series; however, their ability to handle outliers is not well understood. The Prophet model generally outperformed the Holt-Winters model and the SARIMA model. The MAPE and R2 of the Prophet model during pre-COVID-19 were 4.3-22.2% and 0.71-0.93, respectively. All three models showed satisfactory predictive results, especially during the pre-COVID-19 testing period. COVID-19 lockdowns and the associated regulatory measures appear to have affected MSW disposal behaviors, and all the univariate models failed to fully capture the abrupt changes in waste disposal behaviors. Modeling errors were largely attributed to data noise in seasonality and the unprecedented event of COVID-19 lockdowns. Overall, the modeling errors of the Prophet model were evenly distributed, with minimum modeling biases. The Prophet model also appeared to be versatile and successfully captured MSW disposal rates from 3000 to 39,000 tons/month. The study highlights the potential benefits of the use of univariate models in waste forecast.

Spatio-temporal evolution and the driving factors of municipal solid waste in Chinese different geographical regions between 2002 and 2020

Urbanization and economic development have contributed to the rapid and massive generation of municipal solid waste (MSW) and significant changes in spatial patterns, which are becoming a serious pollution problem. Previously, macroscopic studies on the driving factors of MSW have been widely conducted at the national level, but the exploration of the driving factors in different geographical regions on a regional scale has not received much attention in the previous literature. This study is based on China, spatial patterns were analyzed using spatial autocorrelation and movement of center of gravity, and time series clustering was used to explore temporal trends. Subsequently, Geodector was adopted to quantify the relationship between MSW generation and driving factors. The results of the study are as follows: 1) By analyzing the spatial pattern of MSW, this study found that MSW showed a spatial pattern of high in the southeast and low in the northwest during 2002-2020, and its separating line was the same as the Hu-line; the average center of gravity of MSW generation in the past 20 years was always located in Henan Province and shifted southward by 339.7 km. 2) The local spatial autocorrelation analysis results showed that the Low-Low clusters moved from southeast to northwest from 2002 to 2020, increasing to 20 cities. High-High clusters mainly appeared in the East Coast and South Coast regions, increasing from 8 to 17 cities in the last 20 years. 3) The analysis of driving factors by Geodetector revealed that Urbanization is the most critical dimension factor influencing MSW generation, with the strongest impact on the East Coast region. The next dimension is Economy, which has the most significant impact on MSW generation in the North West region. Energy is the third dimension that influences MSW generation, with the greatest impact on the North Coast region. The results of this study reveal trends in the spatial and temporal distribution of MSW in different geographic regions of China over the past 20 years and the impact of their driving factors, which can help the Chinese government take action to control MSW in a site-specific manner.

Estimation of Gas Emissions using the LandGEM Model from the Landfill of Baft County, Kerman, Iran

Over time, waste buried in landfills produces greenhouse gases (GHG) such as methane (CH4) and carbon dioxide (CO2). It is essential to know and investigate the type and amount of production of these gases from landfills as well as their effects, considering the environment's vulnerability to GHG. In the present study, the gases released from the landfill of Baft county were estimated using the landfill gas emissions model (LandGEM). CH4 production rate (k) and potential CH4 generation capacity (Lo) considering the semi-arid area for Baft county were considered 0.05 year-1 and 170 m3/Mg, respectively. According to the results, in 2054, an amount of 18703819 Mg/year of waste enters the landfill of Baft county. The emissions of landfill gases (LFG), including total landfill gas, CH4, and CO2, remained relatively constant between 2004 and 2044, followed by a period of increasing emissions until 2054. However, from that point onward, there was a decline in gas emissions that continued until 2144. In 2054, the estimated emissions for total landfill gas, CH4, CO2, and non-methane organic compounds (NMOC) are projected to be 3.043E + 05, 8.128E + 04, 2.230E + 05, and 3.493E + 03 Mg/year, respectively. Similarly, in 2144, the estimated emissions for total landfill gas, CH4, CO2, and NMOCs are projected to be 3.380E+03, 9.029E+02, 2.477E+03, and 3.881E+01 Mg/year, respectively. The potential to generate 18.25 MWh/year of electricity exists for the Baft county landfill in 2054. The study showed that a significant amount of CH4 and CO2 gases would be discharged into the atmosphere from the landfill site of Baft county, which can be recycled to help produce energy and improve air quality.

Life cycle assessment of municipal solid waste generated from hilly cities in India - A case study

Improper disposal of waste poses a grave environmental threat, contributing to pollution of air, water, and soil. It is necessary to address this issue in order to mitigate the adverse effects of solid waste on both the environment and public health. In many developing nations, municipal authorities of bigger cities are enduring significant challenges in proper management of waste. The present study evaluates the impacts of various waste management alternative scenarios for environmental impacts for the selected study locations using Life Cycle Assessment (LCA) methodology. The methodology comprised of five different scenarios of waste management including an existing baseline scenario. In this context, the environmental impact categories analyzed were Global Warming potential (GWP), Acidification potential (AP), Eutrophication potential (EP) and Human Toxicity potential (HTP). The results indicated that amongst all the proposed scenarios, Scenario 1 and 4 exhibited the maximum and minimum environmental impacts respectively. The study revealed that least greenhouse gas emissions, acidification potential, eutrophication potential and human toxicity potential were comparatively lesser for scenario 4 varying from 5.65 to 11.36 kg CO2eq t-1; 1.24-3.345 kg SO2eq t-1, EP 0.19-0.68 kg PO4eq t-1, and 0.35-4.22 kg 1,4-DBeq t-1 respectively. Further, a sensitivity analysis was also performed to evaluate the influence of recycling rate of valuable resources in all the considered scenarios. The sensitivity analysis indicated an inversely proportional relation between change in recycling rate and total environmental burdens.

Life cycle assessment of biowaste and green waste composting systems: A review of applications and implementation challenges

Composting is one of the most widely applied methods for recycling organic waste. This process has been proposed as one option that facilitates the reincorporation of materials into the production cycle. However, composting also generates environmental impacts. Life Cycle Assessment (LCA) is the most common approach to evaluate the environmental impacts of a process at different system stages. Nevertheless, applying LCA in composting facilities is challenging due to the extensive information required, the lack of standardization on the initial assumptions, the definition of system boundaries, and the high diversity of existing composting technologies. This paper systematically reviews LCA studies in biowaste and/or green waste composting. The study highlights the challenges that should be met in order to improving the application of LCA to evaluate the environmental impacts of this type or waste treatment strategy. The review protocol used identified 456 papers published between 2010 and 2022. After the screening, 56 papers were selected, read, and thoroughly analyzed. The results show that: i) about 68% of the studies aimed to compare composting with other solid waste management options; ii) there was a wide diversity among the impact categories considered, which predominantly included climate change and ozone depletion; iii) there was no consensus on the functional unit or the system boundaries; iv) the main gaseous emissions studied were ammonia, methane, and nitrogen oxide, which were generally determined by emission factors; v) the avoided environmental impacts associated with the end-product quality and its application as an organic amendment or soil improver were ignored. This work demonstrates the complexity of conducting credible and valid composting LCA studies and proposes seven recommendations for improving the application of this assessment methodology to analyze this waste management alternative.

Applicability of the Life Cycle Assessment Model in Solid Waste Management in Zimbabwe

Solid waste increase is inevitable globally due to anthropogenic activities. This adds burden to waste management systems in developing countries including Zimbabwe. Currently, life cycle assessment (LCA) model is used to achieve sustainability and circular economy (CE) in solid waste management. Therefore, the main goal of this paper was to unearth LCA model applicability in solid waste management in Zimbabwe. Data sources were retrieved from databases like Scopus, ScienceDirect and Springer, although government documents were also used. In Zimbabwe, organic and inorganic solid waste is generated from various sources, namely industries, institutions and households. Solid waste management in Zimbabwe is based on traditional linear approach where waste is collected and disposed through landfilling, burning, incineration, burying, open pits or illegally. Most disposal approaches occupy base of waste management pyramid, hence posing detrimental impacts to human health, terrestrial, aquatic and atmospheric ecosystems. Management approaches are far from Agenda 21, Sustainable Development Goals (SDGs), Zimbabwe Vision 2030 and National Development Strategy 1 demands. Literature revealed that LCA model can be utilised to achieve sustainable solid waste management in countries like Zimbabwe. LCA model is essential in management of solid waste in Zimbabwe, since it assists decision makers in selecting management approaches with less environmental health impacts. Moreover, LCA enables application of waste material reuse, recycle, repairing and recovery, thus narrowing the gap to achieve CE and economic growth in Zimbabwe. Owing to LCA model implementation of waste management legislation and policies which support energy recovery and circular economy became easier in Zimbabwe.

Municipal solid waste treatment for bioenergy and resource production: Potential technologies, techno-economic-environmental aspects and implications of membrane-based recovery

World estimated municipal solid waste generating at an alarming rate and its disposal is a severe concern of today's world. It is equivalent to 0.79 kg/d per person footprint and causing climate change; health hazards and other environmental issues which need attention on an urgent basis. Waste to energy (WTE) considers as an alternative renewable energy potential to recover energy from waste and reduce the global waste problems. WTE reduced the burden on fossil fuels for energy generation, waste volumes, environmental, and greenhouse gases emissions. This critical review aims to evaluate the source of solid waste generation and the possible routes of waste management such as biological landfill and thermal treatment (Incineration, pyrolysis, and gasification). Moreover, a comparative evaluation of different technologies was reviewed in terms of economic and environmental aspects along with their limitations and advantages. Critical literature revealed that gasification seemed to be the efficient route and environmentally sustainable. In addition, a framework for the gasification process, gasifier types, and selection of gasifiers for MSW was presented. The country-wise solutions recommendation was proposed for solid waste management with the least impact on the environment. Furthermore, key issues and potential perspectives that require urgent attention to facilitate global penetration are highlighted. Finally, practical implications of membrane and comparison membrane-based separation technology with other conventional technologies to recover bioenergy and resources were discussed. It is expected that this study will lead towards practical solution for future advancement in terms of economic and environmental concerns, and also provide economic feasibility and practical implications for global penetration.

A systematic review of life cycle assessment of solid waste management: Methodological trends and prospects

Solid waste disposal has led to increasing concerns over resource, health, and environmental problems. These issues have been investigated using the Life Cycle Assessment (LCA) technique which helps identify the roots of varying hazards and allows decision-makers to improve the environmental performance of waste management practices. However, there is a lack of review studies that conducted meta-analysis related to developments in critical methodological steps of LCA on solid waste management. To fill this gap, this review paper examines 15 elements comprising the preference of journals, 13 LCA method-related characteristics, and economic assessment. Insights on the limitations and current practices of LCA applications, along with trends for future research, are provided. 240 studies on the LCA of SWM from 2009 until 2020 were systematically reviewed and classified into two major year-groups (i.e., 2009-2014 and 2015-2020) to investigate the trend changes. Among the studied elements, it is found that energy-related applications are on the increase in LCA studies on solid waste management. Anaerobic digestion facilities nearly double in appearance in the second year-group (2015-2020). There is also a more frequent occurrence of certain characterization methods like ReCiPe and CML. Functional units become more diverse, but are overall mostly defined on a mass basis. A frequently identified issue of many LCAs on solid waste management is the ambiguity of data sources such as out-of-date literature or inconsistent geographical references. By addressing issues of methodological standardization, this review study provides a basis to further increase the reliability of results of future LCA studies on solid waste management.

Interval-Valued Pythagorean Fuzzy Similarity Measure-Based Complex Proportional Assessment Method for Waste-to-Energy Technology Selection

This study introduces an integrated decision-making methodology to choose the best “waste-to-energy (WTE)” technology for “municipal solid waste (MSW)” treatment under the “interval-valued Pythagorean fuzzy sets (IPFSs)”. In this line, first, a new similarity measure is developed for IPFSs. To show the utility of the developed similarity measure, a comparison is presented with some extant similarity measures. Next, a weighting procedure based on the presented similarity measures is proposed to obtain the criteria weight. Second, an integrated approach called the “interval-valued Pythagorean fuzzy-complex proportional assessment (IPF-COPRAS)” is introduced using the similarity measure, linear programming model and the “complex proportional assessment (COPRAS)” method. Furthermore, a case study of WTE technologies selection for MSW treatment is taken to illustrate the applicability and usefulness of the presented IPF-COPRAS method. The comparative study is made to show the strength and stability of the presented methodology. Based on the results, the most important criteria are “greenhouse gas (GHG)” emissions (P3), microbial inactivation efficacy (P7), air emissions avoidance (P9) and public acceptance (P10) with the weight/significance degrees of 0.200, 0.100, 0.100 and 0.100, respectively. The evaluation results show that the most appropriate WTE technology for MSW treatment is plasma arc gasification (H4) with a maximum utility degree of 0.717 followed by anaerobic digestion (H7) with a utility degree of 0.656 over various considered criteria, which will assist with reducing the amount of waste and GHG emissions and also minimize and maintain the costs of landfills.

Potential for future reductions of global GHG and air pollutants from circular waste management systems

The rapidly rising generation of municipal solid waste jeopardizes the environment and contributes to climate heating. Based on the Shared Socioeconomic Pathways, we here develop a global systematic approach for evaluating the potentials to reduce emissions of greenhouse gases and air pollutants from the implementation of circular municipal waste management systems. We contrast two sets of global scenarios until 2050, namely baseline and mitigation scenarios, and show that mitigation strategies in the sustainability-oriented scenario yields earlier, and major, co-benefits compared to scenarios in which inequalities are reduced but that are focused solely on technical solutions. The sustainability-oriented scenario leaves 386 Tg CO2eq/yr of GHG (CH4 and CO2) to be released while air pollutants from open burning can be eliminated, indicating that this source of ambient air pollution can be entirely eradicated before 2050.

Comparative life cycle analysis of municipal waste management systems: Kırklareli/Turkey case study

Waste-to-energy approaches are becoming increasingly important around the world, and municipal solid waste (MSW) as a renewable and sustainable energy source is of great importance to be considered in preventing climate change. On the other hand, since uncontrolled MSW is a threat to the environment and human health, sustainable municipal solid waste management should be evaluated to reduce negative environmental impacts. In this study, various municipal solid waste management options having energy production were selected and analysed by using SimaPro 9.0.0.49 to determine the most environmentally friendly waste management system. One-ton MSW in Kırklareli/Turkey was chosen as the functional unit. Environmental impacts were calculated via the CLM-IA method; impact groups were abiotic depletion, abiotic depletion (fossil fuels), global warming, ozone layer depletion, human toxicity, freshwater, marine and terrestrial ecotoxicities, photochemical oxidation, acidification and eutrophication. The first results indicated that energy recovery reduces the environmental impacts and future waste management plant of Kırklareli (material separation for recycling, biomethanisation and landfilling) is the best option within the scope of the environment at present.

Efficient electrokinetic remediation of heavy metals from MSWI fly ash using approaching anode integrated with permeable reactive barrier

During electrokinetic remediation (EKR) of heavy metals (HMs) (Pb, Zn, Cu, and Cd) from municipal solid waste incineration (MSWI) fly ash enhanced by a permeable reactive barrier (PRB), the nearer to the anode, the higher the concentration of H⁺ ions and the greater the remediation effect. Therefore, a potentially new method of PRB-enhanced EKR using an approaching anode (A-EKR + PRB) was studied to help H⁺ ions to quickly migrate to the sample near the cathode. Consequently, the HM leaching and total concentrations were reduced, while an energy reduction of nearly 40% was achieved. The results showed that the best remediation ability was obtained when MSWI fly ash was treated for 16 days at a voltage gradient of 2.5 V/cm, the approaching anode was moved after 4 days, and the PRB contained 10 g of activated carbon. After remediation, the environmental risk analysis showed that A-EKR + PRB reduced all the fractions of HMs, especially the acid extractable and oxidizable fractions, which might have been due to the enhancement of acid dissolution and oxidation by the approaching anode. In addition, the environmental risks of the remaining HMs were reduced, and the results indicated that A-EKR + PRB is an advisable choice for remediation of MSWI fly ash.

Sustainable metropolitan areas perspectives through assessment of the existing waste management strategies

Human activities are considered among the main producers of any kind of pollution. This paper, through a Driver-Pressure-State-Impact-Response (DPSIR) model analyses, focuses on the evaluation and assessment of the existing practices, procedures, and results obtained in order to determine whether the municipal solid waste (MSW) management implemented in three major Greek municipalities in the greater urban area of Attica, namely the municipalities of Nea Smirni, Vyronas, and Piraeus, could be considered viable and sustainable. The evaluation indicated that MSW in Greek cities have reduced over the last years, also suggesting a steady downward trend, which could be considered consistent with that of the per capita incomes in Greece due to the extended economic austerity, while at the same time the recycling indicator seems to optimize. The results are very useful for policymakers and local authorities towards taking actions related to the targets set from the circular economy strategies as well as the targets set from United Nation Development Program and the European Green Deal Strategy.

Application of Polyacrylamide Flocculant for Stabilization of Anaerobic Digestion under Conditions of Excessive Accumulation of Volatile Fatty Acids

Excessive accumulation of volatile fatty acids (VFA) is one of the major factors destabilizing methanogenic digestion of organic wastes in anaerobic bioreactors. Existing methods of stabilization of this process are mostly expensive and labor-intensive, often requiring removal of a considerable portion of acidified biomass from the bioreactor. We propose a method for methanogenesis restoration in such soured reactors by the addition of a cationic polyacrylamide flocculant (PAM) at 20 mg/g total solids. After flocculant addition, mixing should be minimized to prolong the existence of the floccules formed in the presence of the flocculant. While partial microbial degradation of the polyacrylamide flocculant was observed during the thermophilic anaerobic process, complete PAM mineralization did not occur. Significant inhibition of anaerobic processes, primarily in the activity of syntrophic propionate-oxidizing bacteria, was observed at PAM concentrations above 40 mg/g total solids.

Life Cycle Impact Assessment of Garbage-Classification Based Municipal Solid Waste Management Systems: A Comparative Case Study in China

Confronted with a series of problems caused by surging generation of municipal solid waste (MSW), the Chinese central and local governments have promulgated and implemented policies to deal with them, including promotions of the classification of MSW. However, to date, practical knowledge and understanding about benefits for garbage classification from its environmental performance perspective is still limited. The present study is purposed to comprehensively investigate the environmental effects of garbage classification on municipal solid waste management (MSWM) systems based on three proposed garbage classification scenarios in China, via a comparative life cycle impact assessment (LCIA). Taking advantage of Impact Assessment of Chemical Toxics (IMPACT) 2002+ method, this comparative LCIA study can quantitatively evaluate midpoint, endpoint, and single scored life cycle impacts for the studied MSWM systems. A Monte Carlo uncertainty analysis is carried out to test the effectiveness and reliabilities of the LCIA results. The LCIA and uncertainty analysis results show that MSWM systems based on various garbage classification scenarios have significant variations in the studied midpoint, endpoint, and single scored environmental impacts. Different garbage classification scenarios have their individual environmental-friendly superiority for specific impact categories. Overall, results of this study demonstrate that MSW treatment systems integrated with garbage classification are more environmentally friendly by comparison with non-classification; and that the more elaborate the level of MSW classification, the smaller its impacts on the environment.

Life cycle assessment of autoclaved aerated fly ash and concrete block production: a case study in China

With the rapid development of construction industry, consumption of concrete block has increased rapidly in China. As a kind of green building material and resource comprehensive utilization product, autoclaved aerated fly ash and concrete block have better performance in terms of heat preservation, sound insulation, and fire resistance. However, some typical issues are associated with autoclaved aerated fly ash and concrete block production process such as energy and material consumption as well as pollutant emissions. To examine the environmental and economic impacts of its production process is imperative. Choosing 1 m³ of autoclaved aerated fly ash and concrete block product as functional unit and "cradle to gate" as system boundary, a life cycle inventory is developed. The key processes and key materials with significant environmental impact are identified. Results show that the top four environmental impact categories are marine ecotoxicity, freshwater ecotoxicity, freshwater eutrophication, and human toxicity. Key processes are fly ash slurry production, lime grinding, and steam curing processes. These processes account for 46.58%, 26.00%, and 19.62% of the total environmental load respectively. The key materials are cement, lime, and natural gas, which account for 44.91%, 22.79%, and 20.61% respectively of overall environmental impact. Sensitivity analysis shows that the fly ash slurry production should be optimized preferentially, followed by lime grinding and steam curing processes. These findings are helpful to facilitate the sustainable production of autoclaved aerated fly ash and concrete block.

Environmental impact assessment of municipal solid waste management options using life cycle assessment: a case study

The goal of this study is to use life cycle assessment (LCA) tool to assess possible environmental impacts of different municipal solid waste management (MSWM) scenarios on various impact categories for the study area Dhanbad City, India. The scenarios included in the present study are collection and transportation (denoted as S1); baseline scenario consisting of recycling, open burning, open dumping, and finally unsanitary landfilling without energy recovery (denoted by S2); composting and landfilling (denoted by S3); and recycling and composting followed by landfilling of inert waste without energy recovery (denoted by S4). One ton of municipal solid waste (MSW) was selected as the functional unit. The primary data were collected through sampling, surveys, and literatures. Background data were obtained from Eco-invent data of SimaPro 8.1 libraries. The scenarios were compared using the CML 2 baseline 2000 method, and the results indicated that the scenario S1 had the highest impact on marine aquatic ecotoxicity (1.86E + 04 kg 1,4-DB eq.) and abiotic depletion (2.09E + 02 kg Sb eq.). S2 had the highest impact on global warming potential (9.42E + 03 kg CO₂ eq.), acidification (1.15E + 01 kg SO₂ eq.), eutrophication (2.63E + 00 kg PO₄^3- eq.), photochemical oxidation (2.12E + 00 kg C₂H₄ eq.), and human toxicity (2.25E + 01 kg 1,4-DB eq.). However, S3 had the highest impact on abiotic depletion (fossil fuels) (2.71E + 02 MJ), fresh water aquatic ecotoxicity (6.54E + 00 kg 1,4-DB eq.), terrestrial ecotoxicity (3.36E - 02 kg 1,4-DB eq.), and ozone layer depletion (2.73E - 06 kg CFC-11 eq.). But S4 did not have the highest impact on any of the environmental impact categories due to recycling of packaging waste and landfilling of inert waste. Landfilling without energy recovery of mixed solid waste was found as the worst disposal alternative. The scenario S4 was found as the most environmentally suitable technology for the study area and recommended that S4 should be considered for strategic planning of MSWM for the study area.

A review on technological options of waste to energy for effective management of municipal solid waste

Approximately one-fourth population across the world rely on traditional fuels (kerosene, natural gas, biomass residue, firewood, coal, animal dung, etc.) for domestic use despite significant socioeconomic and technological development. Fossil fuel reserves are being exploited at a very fast rate to meet the increasing energy demands, so there is a need to find alternative sources of energy before all the fossil fuel reserves are depleted. Waste to energy (WTE) can be considered as a potential alternative source of energy, which is economically viable and environmentally sustainable. The present study reviewed the current global scenario of WTE technological options (incineration, pyrolysis, gasification, anaerobic digestion, and landfilling with gas recovery) for effective energy recovery and the challenges faced by developed and developing countries. This review will provide a framework for evaluating WTE technological options based on case studies of developed and developing countries. Unsanitary landfilling is the most commonly practiced waste disposal option in the developing countries. However, developed countries have realised the potential of WTE technologies for effective municipal solid waste management (MSWM). This review will help the policy makers and the implementing authorities involved in MSWM to understand the current status, challenges and barriers for effective management of municipal solid waste. This review concluded WTE as a potential renewable source of energy, which will partly meet the energy demand and ensure effective MSWM.