Municipal Solid Waste Treatment by Integrated Solutions: Energy and Environmental Balances

Externalities of energy sources: The operation of a municipal solid waste-to-energy incineration facility in the greater Thessaloniki area, Greece

There is much debate around promoting waste to energy incineration facilities in many communities globally, mainly because of social opposition against potential negative health effects of the operation of these installations close to urban areas. In this paper, a novel decision support approach is developed and its applicability is demonstrated for the greater Thessaloniki area, Greece. In this area, the incineration facilities are hotly debated, mainly due to the "Not In My Back Yard" syndrome related with health considerations. The exclusive method of treatment is landfilling. Health impacts and corresponding externalities attributed to the operation of an incineration facility are reliably estimated. Three potential alternative sites and three scenarios of emission rates are considered, depending on the abatement technology used. The estimated externalities are compared to the corresponding ones attributed to other pressures in the area. The "Years of Life Lost (YOLL)" indicator attributed to the operation of the facility is 2.8 YOLL in the worst-case scenario. This corresponds to a minimal added implication in comparison with the 11,044 YOLL estimated for the area due to the other environmental pressures (road traffic, space heating, industrial activity). The externalities ratio (externalities due to incineration facility/total externalities) for the region is approximately 0.03%. Thus, the impact of this operation on human health is negligible -and preferable to landfilling- even in the case that maximum emission rates are considered. Efforts should be targeted towards enhancing public awareness and militating the widely acknowledged "Not In My Back Yard" syndrome by local communities.

The valorisation of residual waste bales by urban mining

In the last decade, the approach to waste management has undergone severe changes. The urgent need to face the sustainable demand for energy and materials while limiting the burdens associated to traditional waste handling practices have figured out the concept of waste as a resource. New strategies boosting the extensive recovery and diverting waste from disposal activities have been promoted and framed in the wider context of the urban mining, promoting the full exploitation of waste as resource for either new materials or energy production. Such approach has been recently proposed to handle over 5 million tons of pretreated municipal solid waste produced and stored in the form of bales in Campania Region, in southern Italy, between 2000 and 2009. However, since the feasibility of this approach is related to the waste composition as well as to the selection process, an experimental study was performed at an industrial mechanical treatment plant to assess the potential for valorisation of this waste. Results showed that the overall sustainability of the urban mining strategies for the management of Campania waste bales is tightly linked to the flexibility of the selection process scheme to be adopted, which should make the waste recovery fit the market demand of either material or energy.

The Changing Role of CO2 in the Transition to a Circular Economy: Review of Carbon Sequestration Projects

Despite the diversity of studies on global warming and climate change mitigation technologies, research on the changing role of CO2 in the industrial processes, which is connected with the introduction of circular economy principles, is still out of scope. The purpose of this review is to answer the following question: Is technogenic CO2 still an industrial waste or has it become a valuable resource? For this purpose, statistical information from the National Energy Technology Library and the Global CCS Institute databases were reviewed. All sequestration projects (199) were divided into three groups: carbon capture and storage (65); carbon capture, utilization, and storage (100); and carbon capture and utilization (34). It was found that: (1) total annual CO2 consumption of such projects was 50.1 Mtpa in 2018, with a possible increase to 326.7 Mtpa in the coming decade; (2) total amount of CO2 sequestered in such projects could be 2209 Mt in 2028; (3) the risk of such projects being cancelled or postponed is around 31.8%; (4) CO2 is a valuable and sought-after resource for various industries. It was concluded that further development of carbon capture and utilization technologies will invariably lead to a change in attitudes towards CO2, as well as the appearance of new CO2-based markets and industries.

Analyzing Municipal Solid Waste Treatment Scenarios in Rapidly Urbanizing Cities in Developing Countries: The Case of Dar es Salaam, Tanzania

Currently, large quantities of municipal solid waste (MSW) in many cities of the developing countries are being dumped in informal or formal but unregulated dumpsites that threaten the ecological environment and general public health. The situation in Dar es Salaam, Tanzania is of particular concern and is further challenged by a rapidly growing population and urbanization without adequate waste management systems. Current MSW treatment options have been selected based on the judgment and the experience of individuals with authority while underestimating the role of scientifically derived techniques. This study analyzes the most efficient waste treatment options, particularly scenarios with the lowest economic and environmental costs (EcC and EnC, respectively). It uses 12 years (2006-2017) of MSW management data and compares potential waste treatment options for the identified waste streams. A total of 108 different scenarios were designed, and a multi-criteria analysis method was applied to enable the identification of 11 scenarios with acceptable EcCs and EnCs. These formed an initial decision matrix of aggregation dominance that was then categorized into four groups, each represented by the most ideal point. Finally, the dominant scenario that formed the core for all considered options was found. It costs around $274,100 USD while saving about 1585 metric tons (MT) of CO2 emissions daily. This suggests that after all the MSW generated in the city is collected and segregated, organic waste should be composted whilst plastic, paper, glass, and ferrous metal should be recycled. After treatment, other waste will go to some form of landfill. Sustainable management of MSW in this city and others with similar conditions should consider particular local conditions and could use the methods and the findings of this study as a starting point.

Selective Collection Quality Index for Municipal Solid Waste Management

Trentino (an Italian Province located in the northern part of the country) is equipped with a management system of municipal solid waste collection at the forefront. Among the most positive aspects, there is a great ability for waste separation at the source and a consequent low production of residual municipal solid waste for disposal. Latest data show a gross efficiency of selective collection that has recently reached 80%, one of the highest values in Italy. This study analyzed the “Trentino system” to identify the main elements that have been at the base of the current efficient model. This provided an opportunity to propose a selective collection quality index (SCQI), including collection efficiency for each fraction, method of collection, quality of the collected materials, presence of the punctual tariff and tourist incidence. A period relevant for the transition of the collection system to the recent one was chosen for the demonstrative adoption of the proposed indicators in order to determine the potential of the index adoption. Results of the analysis of this case study were obtained in a quantitative form thanks to the sub-parameters that characterize the proposed index. This allowed selected collection decision makers to focus intently on a territory to find criticalities to be solved. For instance, the use of the index and its sub-indicators in the case of Trentino identified and comparatively quantified the local problems resulting from the presence of a large museum in a small town, tourism peaks in some valleys, and a delay in the punctual tariff adoption. The index has been proposed with the aim to make available an integrated tool to analyze other areas in Italy and abroad.

Characterisation of volatile organic compounds (VOCs) released by the composting of different waste matrices

The complaints arising from the problem of odorants released by composting plants may impede the construction of new composting facilities, preclude the proper activity of existing facilities or even lead to their closure, with negative implications for waste management and local economy. Improving the knowledge on VOC emissions from composting processes is of particular importance since different VOCs imply different odour impacts. To this purpose, three different organic matrices were studied in this work: dewatered sewage sludge (M1), digested organic fraction of municipal solid waste (M2) and untreated food waste (M3). The three matrices were aerobically biodegraded in a bench-scale bioreactor simulating composting conditions. A homemade device sampled the process air from each treatment at defined time intervals. The samples were analysed for VOC detection. The information on the concentrations of the detected VOCs was combined with the VOC-specific odour thresholds to estimate the relative weight of each biodegraded matrix in terms of odour impact. When the odour formation was at its maximum, the waste gas from the composting of M3 showed a total odour concentration about 60 and 15,000 times higher than those resulting from the composting of M1 and M2, respectively. Ethyl isovalerate showed the highest contribution to the total odour concentration (>99%). Terpenes (α-pinene, β-pinene, p-cymene and limonene) were abundantly present in M2 and M3, while sulphides (dimethyl sulphide and dimethyl disulphide) were the dominant components of M1.

Barriers to Effective Municipal Solid Waste Management in a Rapidly Urbanizing Area in Thailand

This study focused on determining the barriers to effective municipal solid waste management (MSWM) in a rapidly urbanizing area in Thailand. The Tha Khon Yang Subdistrict Municipality is a representative example of many local governments in Thailand that have been facing MSWM issues. In-depth interviews with individuals and focus groups were conducted with key informants including the municipality staff, residents, and external organizations. The major influences affecting waste management were categorized into six areas: social-cultural, technical, financial, organizational, and legal-political barriers and population growth. SWOT analysis shows both internal and external factors are playing a role in MSWM: There is good policy and a reasonably sufficient budget. However, there is insufficient infrastructure, weak strategic planning, registration, staff capacity, information systems, engagement with programs; and unorganized waste management and fee collection systems. The location of flood prone areas has impacted on location and operation of landfill sites. There is also poor communication between the municipality and residents and a lack of participation in waste separation programs. However, external support from government and the nearby university could provide opportunities to improve the situation. These findings will help inform municipal decision makers, leading to better municipal solid waste management in newly urbanized areas.

Economic and environmental review of Waste-to-Energy systems for municipal solid waste management in medium and small municipalities

The application of Directive 2008/98/CE on Municipal Solid Waste (MSW) implies the need to introduce technologies to generate energy from waste. Incineration, the most widely used method, is difficult to implement in low populated areas because it requires a large amount of waste to be viable (100,000 tons per year). This paper analyses the economic and environmental costs of different MSW-to-Energy technologies (WtE) in an area comprising of 13 municipalities in southern Spain. We analyse anaerobic digestion (Biomethanization), the production of solid recovered fuel (SRF) and gasification, and compare these approaches to the present Biological Mechanical Treatment (BMT) with elimination of the reject in landfill, and incineration with energy recovery. From an economic standpoint the implementation of WtE systems reduces the cost of running present BMT systems and incineration; gasification presents the lowest value. From the environmental standpoint, Life Cycle Assessment shows that any WtE alternatives, including incineration, present important advantages for the environment when compared to BMT. Finally, in order to select the best alternative, a multi-criteria method is applied, showing that anaerobic digestion is the optimal solution for the area studied.

Sampling, characterisation and processing of solid recovered fuel production from municipal solid waste: An Italian plant case study

This article presents the classification of solid recovered fuel from the Massafra municipal solid waste treatment plant in Southern Italy in compliancy with the EN 15359 standard. In order to ensure the reproducibility of this study, the characterisation methods of waste input and output flow, the mechanical biological treatment line scheme and its main parameters for each stage of the processing chain are presented in details, together with the research results in terms of mass balance and derived fuel properties. Under this study, only 31% of refused municipal solid waste input stream from mechanical biological line was recovered as solid recovered fuel with a net heating value (NC=HV) average of 15.77 MJ kg^-1; chlorine content average of 0.06% on a dry basis; median of mercury <0.0064 mg MJ^-1 and 80th percentile <0.0068 mg MJ^-1. The solid recovered fuel produced meets the European Union standard requirements and can be classified with the class code: Net heating value (3); chlorine (1); mercury (1).

The impacts of decision uncertainty on municipal solid waste management

Municipal solid waste treatment options are not necessarily pragmatic if the stakeholders in the system don't mutually agree on their shares of liabilities. Stakeholders will select an option if their benefits are maximized and costs are minimized. A decision support framework is required to assess various waste treatment options and predict the optimal decision, considering multiple criteria and conflicting preferences of multiple stakeholders. Because of the inherent complexity, uncertainty is unavoidable and should be acknowledged to enhance the reliability in the decision-making process. Uncertainties in the cost and benefit estimates, and stakeholders' ability in verbalizing their preferences and their knowledge about each other's priorities can impact the outcome of such environmental management problem. In this study, uncertainty assessment methods such as sensitivity analysis, fuzzy Analytical Hierarchy Process, and Bayesian games have been explored. A case study in Vancouver (BC, Canada) has been used as a proof of concept.

Thermal degradation of paper industry wastes from a recovered paper mill using TGA. Characterization and gasification test

In this survey, a refuse derived fuel (RDF) was produced from paper industry wastes through a mechanical treatment (MT). The two main wastes generated from a recovered paper mill were rejects and de-inking sludge, which were produced principally in the pulping and de-inking processes, respectively. This work presents raw wastes characterization, fuel preparation and gasification tests performed in a circulating fluidized bed (CFB) gasifier pilot plant. The characterization was carried out by proximate and ultimate analysis. Several blends of pre-conditioned rejects and de-inking sludge were densified by means of pelletizing, studying the energy consumption and its quality properties. Besides, thermal degradation of blends was studied under thermogravimetric analysis (TGA). The experimental runs were made from 30 to 900°C in nitrogen atmosphere at three heating ranges, β=5, 10 and 20°C/min. Two thermal stages were identified during the thermal degradation, which are linked to cellulose and plastic degradation. In addition, kinetics parameters were estimated by the application of non-isothermal methods: Kissinger-Akahira-Sunose (KAS), Flynn-Ozawa-Wall (FOW) and Coats and Redfern. The activation energy values were about 140-160 kJ/mol and 60-80 kJ/mol for plastic and cellulosic materials, respectively. Regarding waste valorisation, a blend composed of 95% of rejects and 5% of de-inking sludge was selected for gasification tests. The energy consumption during the preparation was recorded and a gasification tests were done to prove the usability of these pellets in a CFB gasifier. The main results were a net calorific value (NCV) of 5 MJ/Nm(3) and a total tar content of 11.44 g/Nm(3) at an equivalence ratio (ER) of 0.3.

Cardboard/sawdust briquettes as biomass fuel: Physical-mechanical and thermal characteristics

This paper elaborates experimental analysis of cardboard/sawdust briquettes as a viable option for biomass fuel. Physical-mechanical and thermal characteristics of cardboard/sawdust briquettes were investigated. The influence of the main parameters on heating content was also examined through an ANOVA and regression analysis, i.e. pressure influence (that was applied in a punch-and-die process), cardboard/sawdust ratio influence and finally drying temperature influence. In order to find the maximum heating value, minimum ash content and maximum compressive strength optimization were done. The optimal values obtained for the studied briquetting process parameters are a compression force of 588.6 kN, a sawdust mass of 46.66% and a drying temperature of 22°C. According to the mathematical model obtained, these optimal values give a maximum higher heating value of 17.41 MJ/kg, a minimum ash content of 6.62% and a maximum compressive strength of 149.54 N/mm. Finally, Cardboard/sawdust briquettes showed potential for application as viable biomass fuel.

Treatment and disposal of tyres: Two EU approaches. A review

The treatment and disposal of tyres from vehicles has long been of considerable environmental importance. The main problem lies in the mixed composition of the tyres. Studies have been undertaken to modify the structure of the tyres, especially with reference to the percentage of granulated rubber incorporated, in order to improve their performance, and also to reduce their environmental impact during normal functioning (noise, particulates, etc.) and facilitate recycling and final disposal. The aim of the present study is to review and compare how used tyres are treated and disposed of in two different EU countries. The first is Italy, which has been part of the European Union since its inception, and has important industrial traditions. The second is Romania, an emerging country which recently became part of the EU, and whose economic and industrial development has had a major boost in recent years, with a strong growth in waste production, together with consumption in urban areas. The occasion was useful to consider the situation concerning the evolution of the different aspects related to the management of the end-of-life tyres. In particular, the paper considers the properties of tyre waste and their potential reuse, the enhancement of end-of-life tires and the various types of recovery, such as the reconstruction of tyres and the material recovery. The aspects related to the energy recovery and the use of the life cycle analysis, as a tool to support the choices of the best management system, were also taken into consideration, not forgetting that an adequate end-of-life planning is important when developing a sustainable product, since it can affect considerably its overall life cycle.