Economic assessment and energy model scenarios of municipal solid waste incineration and gas turbine hybrid dual-fueled cycles in Thailand

Finding environmentally benign methods related to sound municipal solid waste (MSW) management is of highest priority in Southeast Asia. It is very important to study new approaches which can reduce waste generation and simultaneously enhance energy recovery. One concrete example of particular significance is the concept of hybrid dual-fuel power plants featuring MSW and another high-quality fuel like natural gas. The hybrid dual-fuel cycles provide significantly higher electrical efficiencies than a composite of separate single-fuel power plant (standalone gas turbine combined cycle and MSW incineration). Although hybrid versions are of great importance for energy conversion from MSW, an economic assessment of these systems must be addressed for a realistic appraisal of these technologies. This paper aims to further examine an economic assessment and energy model analysis of different conversion technologies. Energy models are developed to further refine the expected potential of MSW incineration with regards to energy recovery and environmental issues. Results show that MSW incineration can play role for greenhouse gas reduction, energy recovery and waste management. In Bangkok, the electric power production via conventional incineration and hybrid power plants can cover 2.5% and 8% of total electricity consumption, respectively. The hybrid power plants have a relative short payback period (5 years) and can further reduce the CO₂ levels by 3% in comparison with current thermal power plants.     

Life cycle assessment for optimising the level of separated collection in integrated MSW management systems

This life cycle assessment study analyses material and energy recovery within integrated municipal solid waste (MSW) management systems, and, in particular, the recovery of the source-separated materials (packaging and organic waste) and the energy recovery from the residual waste. The recovery of materials and energy are analysed together, with the final aim to evaluate possible optimum levels of source-separated collection that lead to the most favourable energetic and environmental results; this method allows identification of an optimum configuration of the MSW management system. The results show that the optimum level of source-separated collection is about 60%, when all the materials are recovered with high efficiency; it decreases to about 50%, when the 60% level is reached as a result of a very high recovery efficiency for organic fractions at the expense of the packaging materials, or when this implies an appreciable reduction of the quality of collected materials. The optimum MSW management system is thus characterized by source-separated collection levels as included in the above indicated range, with subsequent recycling of the separated materials and energy recovery of the residual waste in a large-scale incinerator operating in combined heat and power mode.     

Recent trends in recycling activities and waste management in Japan

Japan's basic approach to municipal solid waste (MSW) is (1) waste reduction, (2) promotion of recycling, (3) volume reduction by intermediate treatment, and (4) environmentally sound final disposal. A brief history of legislative trends in waste management is given as background for current waste management and recycling activities. The material recovery rate for MSW collected by local municipalities was only 5.6% in 1996. More than half of MSW, on a volume basis, consists of containers and packages, while great amounts of landfill space are also taken up by bulky wastes such as electric appliances. Therefore, in order to promote recycling and decrease landfill waste, Japan is targeting containers, packages, and electric appliances. A law promoting separate collection and recycling of containers and packages (Packaging Waste Recycling Law) and a law requiring the recycling of specific home electric appliances into new products (Home Electric Appliance Recycling Law) were introduced in June 1995 and June 1998, respectively. These laws are in line with the OECD policy Extended Producer Responsibility (EPR). Received: September 16, 1998 / Accepted: March 10, 1999     

Municipal solid waste disposal in Portugal

In recent years municipal solid waste (MSW) disposal has been one of the most important environmental problems for all of the Portuguese regions. The basic principles of MSW management in Portugal are: (1) prevention or reduction, (2) reuse, (3) recovery (e.g., recycling, incineration with heat recovery), and (4) polluter-pay principle. A brief history of legislative trends in waste management is provided herein as background for current waste management and recycling activities. The paper also presents and discusses the municipal solid waste management in Portugal and is based primarily on a national inquiry carried out in 2003 and directed to the MSW management entities. Additionally, the MSW responsibility and management structure in Portugal is presented, together with the present situation of production, collection, recycling, treatment and elimination of MSW. Results showed that 96% of MSW was collected mixed (4% was separately collected) and that 68% was disposed of in landfill, 21% was incinerated at waste-to-energy plants, 8% was treated at organic waste recovery plants and 3% was delivered to sorting. The average generation rate of MSW was 1.32 kg/capita/day.     

Material and energy recovery in integrated waste management systems. An evaluation based on life cycle assessment

This paper reports the environmental results, integrated with those arising from mass and energy balances, of a research project on the comparative analysis of strategies for material and energy recovery from waste, funded by the Italian Ministry of Education, University and Research. The project, involving the cooperation of five University research groups, was devoted to the optimisation of material and energy recovery activities within integrated municipal solid waste (MSW) management systems. Four scenarios of separate collection (overall value of 35%, 50% without the collection of food waste, 50% including the collection of food waste, 65%) were defined for the implementation of energetic, environmental and economic balances. Two sizes of integrated MSW management system (IWMS) were considered: a metropolitan area, with a gross MSW production of 750,000 t/year and an average province, with a gross MSW production of 150,000 t/year. The environmental analysis was conducted using Life Cycle Assessment methodology (LCA), for both material and energy recovery activities. In order to avoid allocation we have used the technique of the expansion of the system boundaries. This means taking into consideration the impact on the environment related to the waste management activities in comparison with the avoided impacts related to the saving of raw materials and primary energy. Under the hypotheses of the study, both for the large and for the small IWMS, the energetic and environmental benefits are higher than the energetic and environmental impacts for all the scenarios analysed in terms of all the indicators considered: the scenario with 50% separate collection in a drop-off scheme excluding food waste shows the most promising perspectives, mainly arising from the highest collection (and recycling) of all the packaging materials, which is the activity giving the biggest energetic and environmental benefits. Main conclusions of the study in the general field of the assessment of the environmental performance of any integrated waste management scheme address the importance of properly defining, beyond the design value assumed for the separate collection as a whole, also the yields of each material recovered; particular significance is finally related to the amount of residues deriving from material recovery activities, resulting on average in the order of 20% of the collected materials.     

Life cycle inventory analyses for five waste management options for discarded newspaper.

This paper presents the results of life cycle inventory (LCI) analyses that were carried out to determine the environmental impacts (emissions, resource extractions and land use) of different newspaper waste management options for the Helsinki Metropolitan Area (HMA). LCI analyses were performed for five product systems, in which discarded newspapers were divided into two streams: separately collected newspapers and newspapers in mixed waste. In all the options, the manufacturing and printing processes of newspaper were kept unchanged. The waste management alternatives included combinations of material recycling, energy recovery and landfilling. These product systems were modelled using the current collection rate of newspaper and four additional collection rates. The LCIs of the product systems showed that the life cycle phase causing the most environmental impacts was the paper mill. When comparing the different waste management systems, the energy recovery options were in general superior to landfilling. The ecological implications of the increased energy recovery and decreased material recycling of newspaper were, however, not yet considered in the study. These aspects were assessed in the life cycle impact assessment (LCIA), which was performed after the LCI phase.     

Life-cycle assessment of a waste refinery process for enzymatic treatment of municipal solid waste

Decrease of fossil fuel dependence and resource saving has become increasingly important in recent years. From this perspective, higher recycling rates for valuable materials (e.g. metals) as well as energy recovery from waste streams could play a significant role substituting for virgin material production and saving fossil resources. This is especially important with respect to residual waste (i.e. the remains after source-separation and separate collection) which in Denmark is typically incinerated. In this paper, a life-cycle assessment and energy balance of a pilot-scale waste refinery for the enzymatic treatment of municipal solid waste (MSW) is presented. The refinery produced a liquid (liquefied organic materials and paper) and a solid fraction (non-degradable materials) from the initial waste. A number of scenarios for the energy utilization of the two outputs were assessed. Co-combustion in existing power plants and utilization of the liquid fraction for biogas production were concluded to be the most favourable options with respect to their environmental impacts (particularly global warming) and energy performance. The optimization of the energy and environmental performance of the waste refinery was mainly associated with the opportunity to decrease energy and enzyme consumption.     

Environmental impact assessment of the incineration of municipal solid waste with auxiliary coal in China

The environmental impacts of waste incineration with auxiliary coal were investigated using the life-cycle-based software, EASEWASTE, based on the municipal solid waste (MSW) management system in Shuozhou City. In the current system, MSW is collected, transported, and incinerated with 250kg of coal per ton of waste. Based on observed environmental impacts of incineration, fossil CO(2) and heavy metals were primary contributors to global warming and ecotoxicity in soil, respectively. Compared with incinerators using excess coal, incineration with adequate coal presents significant benefits in mitigating global warming, whereas incineration with a mass of coal can avoid more impacts to acidification, photochemical ozone and nutrient enrichment because of increased electricity substitution and reduced emission from coal power plants. The "Emission standard of air pollutants for thermal power plants (GB13223-2011)" implemented in 2012 introduced stricter policies on controlling SO(2) and NO(x) emissions from coal power plants. Thus, increased use of auxiliary coal during incineration yields fewer avoided impacts on acidification and nutrient enrichment. When two-thirds of ash is source-separated and landfilled, the incineration of rest-waste presents better results on global warming, acidification, nutrient enrichment, and even ecotoxicity in soil. This process is considered a promising solution for MSW management in Shuozhou City. Weighted normalized environmental impacts were assessed based on Chinese political reduction targets. Results indicate that heavy metal and acidic gas emissions should be given more attention in waste incineration. This study provides scientific support for the management of MSW systems dominated by incineration with auxiliary coal in China.     

Review of municipal solid waste management options in Malaysia,with an emphasis on sustainable waste-to-energy options

A beautiful and clean environment is the desire of every society. Malaysia is facing an uncontrolled increase in municipal solid waste (MSW) generation due to population growth, economic advancement, and industrialization, but the current, most common waste disposal practice of landfilling is not sustainable. The increasing standard of living also saps more energy from the power generation systems in which fossil fuels are the major source of fuel for the plants. Malaysia generates about 0.5–1.9 kg/capita/day of MSW; a total of about 25,000 tonnes/day of MSW is currently generated and is estimated to exceed 30,000 tonnes/day by 2020. Malaysian MSW is mainly composed of 45 % food waste, 24 % plastic, 7 % paper materials, 6 % metal, 4 % wood and 3 % glass, which are commingled, and is thus characterised by 52–66 % moisture content. Currently, 80–95 % of collected MSW is landfilled and 5 % is recycled, while composting and energy recovery are rarely practiced. This paper reviews the solid waste practice in Malaysia and looks into alternative management options for sustainability. Malaysia MSW represents recyclable power and energy potential if properly sorted. This study considered the practice of sorting at the source and the use of combustible MSW components as fuel to generate heat for a hybrid solar, flue gas, chimney power plant.     

Energy recovery and greenhouse gas reduction potential from food waste in Japan

Waste-to-energy is one effective waste management approach for a sustainable society. The purpose of this study was to clarify the potential for energy recovery and greenhouse gas (GHG) reduction that could be achieved by introducing anaerobic digestion (AD) facilities in the process of reconstructing aging incineration facilities in Japan. Using statistical data from 1068 incineration facilities, four future scenarios were considered and compared with the current situation. As results, compared with the current situation the amount of electricity generated could increase by 60 % in 2030, by combining AD facilities for food waste with new, high-efficiency incineration facilities for remaining municipal solid waste (MSW). From a life cycle perspective, net energy recovery in 2030 was approximately three times greater than in 2011, and GHG emission could be reduced by 27 %. The introduction of AD facilities is attractive for small authorities, which currently treat <100 t/day of MSW through incineration facilities without energy recovery. An AD facility is also beneficial for large authorities. On the contrary, in middle-scale authorities that treat 100–299 t/day of MSW, the reconstruction of incineration facilities to include electricity production capabilities requires careful consideration, because it will significantly influence energy recovery and GHG reduction effects.     

Alternative strategies for energy recovery from municipal solid waste Part A: Mass and energy balances

This two-part paper assesses four strategies for energy recovery from municipal solid waste (MSW) by dedicated waste-to-energy (WTE) plants generating electricity through a steam cycle. The feedstock is the residue after materials recovery (MR), assumed to be 35% by weight of the collected MSW. In strategy 1, the MR residue is fed directly to a grate combustor. In strategy 2, the MR residue is first subjected to light mechanical treatment. In strategies 3 and 4, the MR residue is converted into RDF, which is combusted in a fluidized bed combustor. To examine the relevance of scale, we considered a small waste management system (WMS) serving 200,000 people and a large WMS serving 1,200,000 people. A variation of strategy 1 shows the potential of cogeneration with district heating. The assessment is carried out by a Life Cycle Analysis where the electricity generated by the WTE plant displaces electricity generated by fossil fuel-fired steam plants. Part A focuses on mass and energy balances, while Part B focuses on emissions and costs. Results show that treating the MR residue ahead of the WTE plant reduces energy recovery. The largest energy savings are achieved by combusting the MR residue "as is" in large scale plants; with cogeneration, primary energy savings can reach 2.5% of total societal energy use.     

Comparative environmental analysis of waste brominated plastic thermal treatments

The aim of this research activity is to investigate the environmental impact of different thermal treatments of waste electric and electronic equipment (WEEE), applying a life cycle assessment methodology. Two scenarios were assessed, which both allow the recovery of bromine: (A) the co-combustion of WEEE and green waste in a municipal solid waste combustion plant, and (B) the staged-gasification of WEEE and combustion of produced syngas in gas turbines. Mass and energy balances on the two scenarios were set and the analysis of the life cycle inventory and the life cycle impact assessment were conducted. Two impact assessment methods (Ecoindicator 99 and Impact 2002+) were slightly modified and then used with both scenarios. The results showed that scenario B (staged-gasification) had a potentially smaller environmental impact than scenario A (co-combustion). In particular, the thermal treatment of staged-gasification was more energy efficient than co-combustion, and therefore scenario B performed better than scenario A, mainly in the impact categories of "fossil fuels" and "climate change". Moreover, the results showed that scenario B allows a higher recovery of bromine than scenario A; however, Br recovery leads to environmental benefits for both the scenarios. Finally the study demonstrates that WEEE thermal treatment for energy and matter recovery is an eco-efficient way to dispose of this kind of waste.     

Life cycle impact assessment of various waste conversion technologies

Advanced thermal treatment technologies utilizing pyrolysis or gasification, as well as a combined approach, are introduced as sustainable methods to treat wastes in Singapore. Eight different technologies are evaluated: pyrolysis–gasification of MSW; pyrolysis of MSW; thermal cracking gasification of granulated MSW; combined pyrolysis, gasification and oxidation of MSW; steam gasification of wood; circulating fluidized bed (CFB) gasification of organic wastes; gasification of RDF; and the gasification of tyres.Life cycle assessment is carried out to determine the environmental impacts of the various waste conversion systems including global warming potential, acidification potential, terrestrial eutrophication and ozone photochemical formation. The normalization and weighting results, calculated according to Singapore national emission inventories, showed that the two highest impacts are from thermal cracking gasification of granulated MSW and the gasification of RDF; and the least are from the steam gasification of wood and the pyrolysis–gasification of MSW.A simplified life cycle cost comparison showed that the two most costs-effective waste conversion systems are the CFB gasification of organic waste and the combined pyrolysis, gasification and oxidation of MSW. The least favorable – highest environmental impact as well as highest costs – are the thermal cracking gasification of granulated MSW and the gasification of tyres.     

Life cycle assessment of solid refuse fuel production from MSW in Korea

Solid refuse fuel (SRF) produced from waste materials is a promising fuel that can be utilized for energy recovery in industries. This study considered both characterization and weighting modeling as life cycle assessment (LCA) results. This study aimed to analyze the flows of materials and energy and to evaluate the environmental impact of SRF plants using LCA and compared them with an incineration plant. Based on the results of material and energy flow analysis, SRF products had various energy potentials depending on the treatment method of municipal solid waste (MSW) and replaced the current fossil fuels by SRF combustion. Global impacts were mainly influenced by energy consumption, especially drying methods in the production of SRF, and affected the results of the weighting analysis. The SRF plant with a bio-drying option was evaluated as the best effective practice in the weighting analysis. The LCA results in this study indicated 0.021–9.88 points according to drying methods for SRF production and 1.38 points for incineration. In the sensitivity analysis, the environmental impact of SRF production was found to be significantly affected by the drying methods for MSW and the utilization of fossil energy. Thus, improvement of the drying options could significantly reduce the environmental impact.     

Optimal solid waste collection routes identified by the ant colony system algorithm.

In the present paper, the Ant Colony System (ACS) algorithm is used for the identification of optimal routes in the case of municipal solid waste (MSW) collection. The proposed MSW management system is based on a geo-referenced spatial database supported by a geographic information system (GIS). The GIS takes into account all the required parameters for solid waste collection. These parameters include static and dynamic data, such as the positions of waste bins, the road network and the related traffic, as well as the population density in the area under study. In addition, waste collection schedules, truck capacities and their characteristics are also taken into consideration. Spatio-temporal statistical analysis is used to estimate inter-relations between dynamic factors, like network traffic changes in residential and commercial areas. The user, in the proposed system, is able to define or modify all of the required dynamic factors for the creation of alternative initial scenarios. The objective of the system is to identify the most cost-effective scenario for waste collection, to estimate its running cost and to simulate its application. Finally, the results of the ACS algorithm are compared with the empirical method currently used by the Municipality of Athens.     

Eco-efficiency for greenhouse gas emissions mitigation of municipal solid waste management: a case study of Tianjin, China

The issue of municipal solid waste (MSW) management has been highlighted in China due to the continually increasing MSW volumes being generated and the limited capacity of waste treatment facilities. This article presents a quantitative eco-efficiency (E/E) analysis on MSW management in terms of greenhouse gas (GHG) mitigation. A methodology for E/E analysis has been proposed, with an emphasis on the consistent integration of life cycle assessment (LCA) and life cycle costing (LCC). The environmental and economic impacts derived from LCA and LCC have been normalized and defined as a quantitative E/E indicator. The proposed method was applied in a case study of Tianjin, China. The study assessed the current MSW management system, as well as a set of alternative scenarios, to investigate trade-offs between economy and GHG emissions mitigation. Additionally, contribution analysis was conducted on both LCA and LCC to identify key issues driving environmental and economic impacts. The results show that the current Tianjin’s MSW management system emits the highest GHG and costs the least, whereas the situation reverses in the integrated scenario. The key issues identified by the contribution analysis show no linear relationship between the global warming impact and the cost impact in MSW management system. The landfill gas utilization scenario is indicated as a potential optimum scenario by the proposed E/E analysis, given the characteristics of MSW, technology levels, and chosen methodologies. The E/E analysis provides an attractive direction towards sustainable waste management, though some questions with respect to uncertainty need to be discussed further.     

Municipal solid waste in Mostaganem city (Western Algeria)

The management of municipal solid waste (MSW) and valorisation is based on the understanding of MSW composition by its categories and physicochemical characteristics. In this study, we characterize and determine physicochemical parameters (density, fire loss, electric conductivity, average pH, moisture level, lower calorific value (LCV), total and organic carbon, and nitrogen) in order to establish MSW valorisation models for Mostaganem city (located in Western Algeria). The results show that organic matter represents 64.6% of waste, followed by paper-cardboard 15.9%, plastic 10.5%, glass 2.8%, textile 2.3%, metals 1.9%, and diverse materials 2%. These statistics are similar to results from developing countries, especially if organic matter, paper and plastic are taken into account, but differ from developed countries. This reflects the difference in lifestyle and consumption behaviour between the two communities. The parameters used to determine the possible valorisation model had the following average values: fire loss (63%); ash (37%); pH (6.1); electric conductivity (2.39 ms cm(-1)); total carbon (29.5%); nitrogen (1.5%); LCV (1028.6 kcal/kg), density (0.36), C/N (19.7) and moisture level (58.9%). The study shows that 31.1% of paper-cardboard, plastic, glass and metal wastes are recyclable. Incinerating MSW, with energy recovery, was a poor option because of the weak LCV (1028.6 kcal/kg). However, MSW produced a good methane yield of up to 1852.4 equivalent tons of oil per year. The agricultural benefits, C/N ratio values, levels of moisture and pH and the Tanner diagram all supported compost production.     

Methodology to design a municipal solid waste generation and composition map: A case study

The municipal solid waste (MSW) management is an important task that local governments as well as private companies must take into account to protect human health, the environment and to preserve natural resources. To design an adequate MSW management plan the first step consist in defining the waste generation and composition patterns of the town. As these patterns depend on several socio-economic factors it is advisable to organize them previously. Moreover, the waste generation and composition patterns may vary around the town and over the time. Generally, the data are not homogeneous around the city as the number of inhabitants is not constant nor it is the economic activity. Therefore, if all the information is showed in thematic maps, the final waste management decisions can be made more efficiently. The main aim of this paper is to present a structured methodology that allows local authorities or private companies who deal with MSW to design its own MSW management plan depending on the available data. According to these data, this paper proposes two ways of action: a direct way when detailed data are available and an indirect way when there is a lack of data and it is necessary to take into account bibliographic data. In any case, the amount of information needed is considerable. This paper combines the planning methodology with the Geographic Information Systems to present the final results in thematic maps that make easier to interpret them. The proposed methodology is a previous useful tool to organize the MSW collection routes including the selective collection. To verify the methodology it has been successfully applied to a Spanish town.     

Application of spatial and non-spatial data analysis in determination of the factors that impact municipal solid waste generation rates in Turkey

In studies focusing on the factors that impact solid waste generation habits and rates, the potential spatial dependency in solid waste generation data is not considered in relating the waste generation rates to its determinants. In this study, spatial dependency is taken into account in determination of the significant socio-economic and climatic factors that may be of importance for the municipal solid waste (MSW) generation rates in different provinces of Turkey. Simultaneous spatial autoregression (SAR) and geographically weighted regression (GWR) models are used for the spatial data analyses. Similar to ordinary least squares regression (OLSR), regression coefficients are global in SAR model. In other words, the effect of a given independent variable on a dependent variable is valid for the whole country. Unlike OLSR or SAR, GWR reveals the local impact of a given factor (or independent variable) on the waste generation rates of different provinces. Results show that provinces within closer neighborhoods have similar MSW generation rates. On the other hand, this spatial autocorrelation is not very high for the exploratory variables considered in the study. OLSR and SAR models have similar regression coefficients. GWR is useful to indicate the local determinants of MSW generation rates. GWR model can be utilized to plan waste management activities at local scale including waste minimization, collection, treatment, and disposal. At global scale, the MSW generation rates in Turkey are significantly related to unemployment rate and asphalt-paved roads ratio. Yet, significances of these variables may diminish at local scale for some provinces. At local scale, different factors may be important in affecting MSW generation rates.     

An environmentally sustainable decision model for urban solid waste management

The aim of this work is to present the structure and the application of a decision support system (DSS) designed to help decision makers of a municipality in the development of incineration, disposal, treatment and recycling integrated programs. Specifically, within a MSW management system, several treatment plants and facilities can generally be found: separators, plants for production of refuse derived fuel (RDF), incinerators with energy recovery, plants for treatment of organic material, and sanitary landfills. The main goal of the DSS is to plan the MSW management, defining the refuse flows that have to be sent to recycling or to different treatment or disposal plants, and suggesting the optimal number, the kinds, and the localization of the plants that have to be active. The DSS is based on a decision model that requires the solution of a constrained non-linear optimization problem, where some decision variables are binary and other ones are continuous. The objective function takes into account all possible economic costs, whereas constraints arise from technical, normative, and environmental issues. Specifically, pollution and impacts, induced by the overall solid waste management system, are considered through the formalization of constraints on incineration emissions and on negative effects produced by disposal or other particular treatments.