Mixed Municipal Solid Waste Research Articles

Influence of different factors in the life cycle assessment of mixed municipal solid waste management systems – A comparison of case studies in Finland and China

The life cycle assessment (LCA) of municipal solid waste (MSW) management systems is typically rather arduous due to extensive data acquisition needed to calculate the direct and avoided emissions of the systems. A possibility to diminish the workload of the LCA studies is to utilise default or generic data instead of direct and case-specific data. However, it is crucial to know when this is justified. Direct and case-specific data should be applied at least to the key processes and parameters which have the strongest influence on the total results, whereas default data can be applied to the processes and parameters which have only a minor influence on the total results.Mixed MSW management systems in the South Karelia region, Finland, and the city of Hangzhou, China, were compared in this study in terms of the influence of different factors on the LCA results of the systems. The comparison focused particularly on the influence of individual parameters on the global warming, acidification and eutrophication potentials of the LCA studies. According to the study, parameters directly related to the generation and collection of landfill gas, the energy and fossil carbon content of mixed MSW, energy production efficiencies, as well as the nitrogen oxide and sulfur dioxide emissions of incineration had the highest influence on the total results in both case studies, and therefore direct, case-specific data should be applied particularly to them. The use of machinery in landfilling, the electricity and chemical consumption in leachate treatment, the transportation of auxiliary materials (e.g. chemicals and incineration residues) as well as the electricity consumption and the use of machinery in bottom and boiler ash treatment had instead only a minor influence on the total results. Default or generic data could be applied to them to diminish the workload of the LCA studies. It is worth mentioning that the findings of the study apply merely to these particular case studies. Further research and corresponding comparisons are required to draw more profound and general conclusions.

Recycling organic wastes to agricultural land as a way to improve its quality: A field study to evaluate benefits and risks

A field study was established to assess the effects of a sewage sludge (SS), a mixed municipal solid waste compost (MMSWC) and a compost produced from agricultural wastes (AWC), in a Vertisol, using Lolium multiflorum L. The amendments were applied for two consecutive years: 6, 12 and 24t dry matter ha−1 for SS, and the amendment doses for MMSWC and AWC were calculated to deliver the same amount of organic matter (OM) per unit area. The amendments had significant beneficial effects on some soil properties (e.g. soil OM, NKjeldahl, extractable P and K), and on plant productivity parameters (e.g. biomass yield, chlorophyll, foliar area). For instance, soil OM increased from 0.78% to 1.71, 2.48 and 2.51%, after two consecutive years of application of 24t dry matter ha−1 of SS, MMSWC and AWC, respectively, while the plant biomass obtained increased from 7.75tha−1 to 152.41, 78.14 and 29.26tha−1, for the same amendments. On the plant, effects were more pronounced for SS than for both compost applications, a consequence of its higher capacity to provide N to the plant in a readily available form. However, after two years of application, the effects on soil properties were more noticeable for both composts, as their OM is more resistant to mineralization, which endures their beneficial effects on soil. Cadmium, Cr, Ni and Pb pseudo-total concentrations, were not affected significantly by the application of the organic wastes to soil, in all tested doses, neither their extractability by 0.01M CaCl2. On the contrary, Cu and Zn pseudo-total concentrations increased significantly in the second year of the experiment, following the application of the higher rate of MMSWC and AWC, although their extractability remained very low (<0.5% of their pseudo-total fraction). Trace elements concentrations in the aboveground plant material were lower than their maximum tolerable levels for cattle, used as an indicator of risk of their entry into the human food chain. Despite these results, it is interesting to note that the SS promoted a significant increase in the foliar concentrations of Cu, Ni and Zn that did not happen in composts application, which can be explained by the reduction of the soil pH, as a consequence of SS degradation in soil. Concluding, if this type of organic wastes were to be used in a single application, the rate could be as high as 12 or even 24tha−1, however, if they are to be applied in an annual basis, the application rates should be lowered to assure their safe application (e.g. to 6tha−1). Moreover, it is advisable to use more stable and mature organic wastes, which have longer lasting positive effects on soil characteristics.

Development of the Laboratory Anaerobic Bioreactor for Wet and Dry Digestion Processes

Abstract This article presents partial results of the laboratory development of an anaerobic bioreactor designed for the physical modelling of (semi)continuous dry or wet anaerobic digestion processes. A horizontal cylindrical tank reactor of 0.4 m3 total capacity has been developed. The reactor allows the continuous stirring of a liquid batch or the intermittent stirring of a solid batch. The bioreactor has been used as a lab-scale digestor in the research project dealing with high-solids (dry) anaerobic co-digestion organic fraction of mixed municipal solid waste. The first experiment was performed on the mixture of MSW with corn silage (1:1) with the weight of 300 kg.

Health risk impacts analysis of fugitive aromatic compounds emissions from the working face of a municipal solid waste landfill in China

Aromatic compounds (ACs) emitted from landfills have attracted a lot of attention of the public due to their adverse impacts on the environment and human health. This study assessed the health risk impacts of the fugitive ACs emitted from the working face of a municipal solid waste (MSW) landfill in China. The emission data was acquired by long-term in-situ samplings using a modified wind tunnel system. The uncertainty of aromatic emissions is determined by means of statistics and the emission factors were thus developed. Two scenarios, i.e. ‘normal-case’ and ‘worst-case’, were presented to evaluate the potential health risk in different weather conditions. For this typical large anaerobic landfill, toluene was the dominant species owing to its highest releasing rate (3.40±3.79g·m−2·d−1). Despite being of negligible non-carcinogenic risk, the ACs might bring carcinogenic risks to human in the nearby area. Ethylbenzene was the major health threat substance. The cumulative carcinogenic risk impact area is as far as ~1.5km at downwind direction for the normal-case scenario, and even nearly 4km for the worst-case scenario. Health risks of fugitive ACs emissions from active landfills should be concerned, especially for landfills which still receiving mixed MSW.

Critical review of the methane generation potential of municipal solid waste

ABSTRACTThe ultimate methane generation potential (L0) of municipal solid waste (MSW) has been used in first-order decay models for the estimation of landfill gas (LFG) production for the previous 30 years. L0 is an inherent property of the waste component, often a function of the lignocellulosic concentrations within. Methane yields of individual waste components can be measured in a controlled laboratory setting; however, the extent to which each portion degrades in a landfill is uncertain. Methane generation in a landfill is difficult to estimate due to the spatial and temporal variations among sites and the heterogeneous composition of MSW streams. Predicting LFG production is further complicated by prior aerobic degradation, fugitive gas emissions that escape into the atmosphere, and unforeseen chemical inhibition within the landfill environment. Published L0 values are reviewed and compared to the methane yields of mixed-waste and waste components measured in the laboratory. Experimentally determined values of mixed MSW ranged from 35 to 167 m3 CH4/Mg MSW. Modeled values and those based on biodegradability of individual components and waste composition data ranged from 20 to 223 m3 CH4/Mg MSW. These data constitute a wide range of experimental methodologies and waste composition characteristics with respect to geography and time. The usefulness, comparability, and applicability of such data are discussed. The use of L0 as a parameter in LFG generation models and life-cycle assessments is reviewed and discussed.

Experimental investigation on the drying of loosely-packed and heterogeneous municipal solid waste

In this paper, experimental investigation on convective drying of mixed municipal solid wastes was conducted. The aim of this study was to determine the effect of temperature, change in composition and particle size on the overall drying rate coefficient and mass transfer coefficient. Particle size of the samples was determined and mass losses recorded with time when the samples were dried using convective dryer. Mass losses were used to determine moisture content, drying rate coefficient and mass transfer coefficient. Experimental results showing the effect of temperature, changes in the composition of organic waste and particle size were presented.

Emerging Waste-to-Energy Technologies: Solid Waste Solution or Dead End?

Incineration is a dirty word in the United States, at least where trash is involved. We’ve been burning municipal solid waste (MSW) since the 1880s. But the dawning of the environmental movement eight decades later cast new light on the nitrous oxides, dioxins, and other chemicals emitted from as many as 600 mass-burn incinerators nationwide, which meanwhile had also grown in size. 1 , 2 The ecological merits of resource conservation and recycling became another area of growing interest. Three emerging thermal waste-to-energy technologies seek to turn municipal solid waste from a burden to an asset. Adherents of these technologies say they produce fewer toxic emissions and virtually eliminate landfilling. But none of the technologies ... Now three new approaches to converting trash into energy—so-called waste-to-energy (WTE) technologies—look to leave mass-burn incineration behind by transforming how we think about MSW in the United States. Adherents of these emerging approaches—gasification, plasma gasification, and pyrolysis—promise cleaner emissions and more flexibility in terms of energy output, plus in some cases the virtual elimination of landfilling through a complex two-stage treatment process. 3 , 4 , 5 , 6 , 7 But none of the technologies have yet been proven on a commercial scale on U.S. soil using a typical mixed MSW feedstock, says Monica Wilson, program director for the advocacy group Global Alliance for Incinerator Alternatives (GAIA). After years of delays and high-profile failures, the technologies remain stymied by challenges such as operational inexperience, high costs, lack of financing, and concerns about toxic emissions. Furthermore, the heterogeneous nature of MSW can make it a problematic feedstock for power plants, and some critics believe it is more important to assess what materials are actually in MSW and the best uses associated with each of those materials—for instance, recycling, composting, reducing, or redesigning the materials before they enter the waste stream. Negative public perception of incineration also could prevent acceptance of newer WTE technologies in the United States. Modern mass-burn facilities are a huge improvement over the dirty plants that first drew public outrage. Beginning with the Clean Air Act in 1970, tightened regulations and sophisticated air pollution controls significantly reduced the levels of harmful chemicals emitted by incinerators. Today, 70 mass-burn plants in 21 states 8 consume about 13% of the nation’s trash, down from a peak of 14.5% in 1990. 9 , 10 Cumulatively they offer roughly 2.5 gigawatts of power in return, 11 , 12 less than a tenth of what the U.S. solar industry produces. 13 The most recent inventory available from the U.S. Environmental Protection Agency shows that MSW incinerators released about 1% of the quantity of carcinogenic and highly toxic dioxin-like compounds in 2000 that they did just 13 years earlier. 14 Yet by the 1980s the damage to incineration’s reputation was done, as far as many environmental groups and the public at large were concerned. And the battle lines drawn all those years ago remain largely intact today. So claims that these new technologies offer a panacea to waste management and a source of clean, renewable energy have met with skepticism and organized opposition in dozens of communities nationwide faced with proposals in recent years. 15 Ultimately, if the new technologies are to take hold in this country, developers must find a way to not only support their performance claims, but also demonstrate compatibility with established recycling and composting efforts and achieve financial feasibility in areas experiencing no shortage of landfill space. 16 Even some proponents of the new technologies wonder if that will ever happen.

Updating and testing of a Finnish method for mixed municipal solid waste composition studies

More efficient recycling of municipal solid waste (MSW) is an essential precondition for turning Europe into a circular economy. Thus, the recycling of MSW must increase significantly in several member states, including Finland. This has increased the interest in the composition of mixed MSW. Due to increased information needs, a method for mixed MSW composition studies was introduced in Finland in order to improve the national comparability of composition study results. The aim of this study was to further develop the method so that it corresponds to the information needed about the composition of mixed MSW and still works in practice.A survey and two mixed MSW composition studies were carried out in the study. According to the responses of the survey, the intensification of recycling, the landfill ban on organic waste and the producer responsibility for packaging waste have particularly influenced the need for information about the composition of mixed MSW. The share of biowaste in mixed MSW interested the respondents most. Additionally, biowaste proved to be the largest waste fraction in mixed MSW in the composition studies. It constituted over 40% of mixed MSW in both composition studies. For these reasons, the classification system of the method was updated by further defining the classifications of biowaste. The classifications of paper as well as paperboard and cardboard were also updated. The updated classification system provides more information on the share of avoidable food waste and waste materials suitable for recycling in mixed MSW. The updated method and the information gained from the composition studies are important in ensuring that the method will be adopted by municipal waste management companies and thus used widely in Finland.

Mineral matter in municipal solid waste

Municipal solid waste (MSW) contains mineral materials which are seldom considered as a potential resource. Currently, the waste management sector pays attention to recyclable parts, biodegradable material, waste-to-energy fraction, and residues after waste reuse and recycle. In contrast, this study focus as on the mineral matter in MSW. The aim was to analyze and discuss the sources of mineral matter in MSW, the impact which the minerals have on waste management technologies, and finally, the possibility to recycle the mineral matter. The contribution of inorganic matter in the MSW stream is significant (about 20 wt.%). In the years 2012-2015, the average content of mineral matter in mixed MSW in Poland ranged from 16 wt.% to 36 wt.%, and the content of organic in MSW ranged from 20 wt.% to 42 wt.%. Minerals in MSW have rather negative impact on waste management technologies and their final products, and can be sorted out from the MSW stream, either in the households or in a central sorting line. However, in central collection and separation systems it is difficult to obtain a mineral matter fraction in subsequent processing steps due to technological limitations (inefficiency of devices), high degree of waste fragmentation and pollution of mineral matter with other waste. This indicates a hampered ability to separate minerals in a form available for reuse, so an effective system should be based on improved segregation at the source.

Pyrolysis of municipal solid waste in a fluidized bed for producing valuable pyrolytic oils

In order to recover valuable pyrolytic oils, mixed municipal solid waste was pyrolyzed in a fluidized bed reactor. Results showed that liquid products yielded among 38.4–56.5 wt% and separated into water-soluble phases and organic phases. Moisture was concentrated in the water-soluble phases (39.4–57.3 wt%), making them low in carbon content and heating value. On the other hand, the higher carbon content and lower oxygen content of organic phases make their heating value (27.5–32.1 MJ/kg) and quality higher than bio-oils. Water-soluble phases mainly included acids, carboxylics, phenols, and sugars, which could be used as chemical feedstocks and substantial fuel. Organic phases mostly contained aromatics and phenols and could be used as fossil fuels directly or as chemical materials. Heavy metals of Cd and Pb were proved to be poor in both water-soluble phases and organic phases. As for Zn, it was found to be higher in the water-soluble phases at 450 and 550 °C with quartz sand as bed material than that in crude oils. However, Zn content in organic phases was comparable to crude oils. High-aluminum bauxite and attapulgite as bed materials increased heating value of water-soluble phases and organic phases respectively, and both performed well in reducing the Zn content of water-soluble phases. This work proved that it was an operative way to produce valuable pyrolytic oils by pyrolysis of mixed municipal solid waste.

Biodrying process: A sustainable technology for treatment of municipal solid waste with high moisture content

Municipal solid waste with high moisture content is the major hindrance in the field of waste to energy conversion technologies and here comes the importance of biodrying process. Biodrying is a convective evaporation process, which utilizes the biological heat developed from the aerobic reactions of organic components. The numerous end use possibilities of the output are making the biodrying process versatile, which is possible by achieving the required moisture reduction, volume reduction and bulk density enhancement through the effective utilization of biological heat. In the present case study the detailed research and development of an innovative biodrying reactor has been carried out for the treatment of mixed municipal solid waste with high moisture content. A pilot scale biodrying reactor of capacity 565cm3 was designed and set up in the laboratory. The reactor dimensions consisted of an acrylic chamber of 60cm diameter and 200cm height, and it was enveloped by an insulation chamber. The insulation chamber was provided to minimise the heat losses through the side walls of the reactor. It simulates the actual condition in scaling up of the reactor, since in bigger scale reactors the heat losses through side walls will be negligible while comparing the volume to surface area ratio. The mixed municipal solid waste with initial moisture content of 61.25% was synthetically prepared in the laboratory and the reactor was fed with 109kg of this substrate. Aerobic conditions were ensured inside the reactor chamber by providing the air at a constant rate of 40 litre per minute, and the direction of air flow was from the specially designed bottom air chamber to the reactor matrix top. The self heating inside reactor matrix was assumed in the range of 50–60°C during the design stage. Innovative biodrying reactor was found to be efficiently working with the temperature inside the reactor matrix rising to a peak value of 59°C by the fourth day of experiment (the peak observed at a height of 60cm from the air supply). The process analyses results were promising with a reduction of 56.5% of volume, and an increase of 52% of bulk density of the substrate at the end of 33days of biodrying. Also the weight of mixed MSW substrate has been reduced by 33.94% in 20days of reaction and the average moisture reduction of the matrix was 20.81% (reduced from the initial value of 61.25% to final value of 48.5%). The moisture reduction would have been higher, if the condensation of evaporated water at the reactor matrix has been avoided. The non-homogeneous moisture reduction along the height of the reactor is evident and this needs further innovation. The leachate production has been completely eliminated in the innovative biodrying reactor and that is a major achievement in the field of municipal solid waste management technology.

Kinetics of Pyrolysis of Mixed Municipal Solid Waste-A Review

Municipal solid waste management is one of the major challenges faced by most of the developing countries like India. The scarcity of land due to large population and increasing waste production due to urbanization impose a challenge to find innovative methods for waste disposal. Thermal treatment is seen as an emerging technology which can help in reducing the volume of the waste and also extract energy and value added products during processing of the waste. However, the raw material mostly has low calorific value which causes problem for its thermal treatment. Pyrolysis, combustion and gasification are the major thermal treatment processes. Pyrolysis, found more promising than other processes, is discussed in this paperin regards to its kinetics and reaction conditions and products formed to understand and further develop the technology. Any improvement in the treatment processes requires an understanding of the fundamentals of the reactions specific to the waste being treated. It is concluded that suitable combination of reaction conditions along with reactor design needs to be formulated once the process kinetics for the treatment of mixed municipal solid waste during pyrolysis is estimated.

Biodrying Process Efficiency: -Significance of Reactor Matrix Height

Waste to energy concept should become a reality to meet the critical issues faced by the solid waste management system of developing nations. Energy oriented municipal solid waste conversion technologies have the potential to reduce the bulk volume of the waste in addition to the refuse derived fuel production applications. In this scenario biodrying process is found to be the best option, where biological heat energy is effectively channelized for drying purpose so that the heavy moisture laden municipal solid waste is dried and its energy value is increased. This technology seemed to be promising specially in the case of developing nations where the heavy moisture content of the typical municipal solid waste is the major issue faced by the waste to energy conversion systems. In the present case study the effect of increasing the reactor matrix height and the resulting changes in the biodrying process output has been studied in a pilot scale biodrying reactor of 0.565 m3 capacity for a period of 10 days. Two case studies were conducted on mixed municipal solid waste substrates with moisture content of 62.45% and 66.4% respectively. The reactor matrix height of first case study was kept at1.65 m, while that is increased to 2.0 m in the second case study. The constant air flow rate of 40 litre per minute was provided throughout the experiment for both case studies. During the second case study an air evacuation test has also been conducted on the 4th and 5th day of experiment to understand the temperature profile variations. Overall weight reduction of 26.32% and 19.01% along with average moisture reduction of 24.26% and 15.98% has been achieved in the first and second case studies respectively in 10 days of reaction. The volume reduction and bulk density increase was the maximum in the second case study with 43.5% volume reduction and 53.01% bulk density increase in achieved in 10 days of biodrying reaction. Comparing to that a lesser result has been obtained in 10 days of experiment in the first case study with a volume reduction of 35.1% and bulk density increase of 27.58%. Therefore increasing the reactor matrix height at a constant air flow rate has affected the biodrying process efficiency in terms of weight reduction and moisture reduction, but the volume reduction and bulk density increase were significant achievements.

Municipal Solid Waste to Energy Generation in Bangladesh: Possible Scenarios to Generate Renewable Electricity in Dhaka and Chittagong City

Increased generation of methane (CH4) from municipal solid wastes (MSW) alarms the world to take proper initiative for the sustainable management of MSW, because it is 34 times stronger than carbon dioxide (CO2). Mounting land scarcity issue around the world brands the waste to energy (WtE) strategy for MSW management in urban areas as a promising option, because WtE not only reduces the land pressure problem, but also generates electricity, heat, and green jobs. The goal of this study is to evaluate the renewable electricity generation potential and associated carbon reduction of MSW management in Bangladesh using WtE strategies. The study is conducted in two major cities of Bangladesh: Dhaka and Chittagong. Six different WtE scenarios are evaluated consisting of mixed MSW incineration and landfill gas (LFG) recovery system. Energy potential of different WtE strategy is assessed using standard energy conversion model and subsequent GHGs emissions models. Scenario A1results in highest economic and energy potential and net negative GHGs emission. Sensitivity analysis by varying MSW moisture content reveals higher energy potential and less GHGs emissions from MSW possessing low moisture content. The study proposes mixed MSW incineration that could be a potential WtE strategy for renewable electricity generation in Bangladesh.

Municipal Solid Waste Characteristics and Green and Clean Energy Recovery in Asian Megacities

Today population growth, economic prosperity, and urbanization have led to an increase in municipal solid waste (MSW). The higher-populated and higher-income countries generate higher amounts of MSW. Not only the MSW amount, but the MSW composition can also be diverse in different countries. This study investigates the composition of MSW generated in Bangkok compared to other Asian megacities, for example, Beijing, Tokyo, Seoul, Singapore and Hong Kong. In addition, the MSW management model integrated with the Waste-to-Energy (WtE) concept will be analyzed and compared. With Bangkok as the case study, because of a lack of regulations and public participation, there is no MSW separation at the households; hence, the MSW generated contains higher organic waste which results in less calorific value of MSW compared to other developed countries. Mixed wet MSW is the main shortcoming of WtE development. As Bangkok is the main MSW producer in Thailand, which generates more than one-fourth of the domestic MSW, the WtE project was developed in Bangkok as a demonstration plant of WtE. The 500 ton per day incineration plant coupled with a power generation unit has been constructed for sustainable MSW disposal and for energy security in the megacity.

Recovery of glass from the inert fraction refused by MBT plants in a pilot plant

Selective collection is a common practice in many countries. However, even in some of those countries there are recyclable materials, like packaging glass, erroneously deposited in the Mixed Municipal Solid Waste (MMSW). In the present paper, a solution is proposed to recover glass from the inert reject of Mechanical and Biological Treatment (MBT) plants treating MMSW aiming at its recycling. The inert reject of MBT (MBTr) plants is characterized by its small particle size and high heterogeneity. The study was made with three real samples of diverse characteristics superimposed mainly by the different upstream MBT. One of the samples (VN) had a high content in organics (approximately 50%) and a particle size smaller than 16mm. The other two were coarser and exhibited similar particle size distribution but one (RE) was rich in glass (almost 70%) while the other (SD) contained about 40% in glass. A flowsheet was developed integrating drying, to eliminate moisture related with organic matter contamination; magnetic separation, to separate remaining small ferrous particles; vacuum suction, to eliminate light materials; screening, to eliminate the finer fraction that has a insignificant content in glass, and to classify the >6mm fraction in 6–16mm and >16mm fractions to be processed separately; separation by particle shape, in the RecGlass equipment specifically designed to eliminate stones; and optical sorting, to eliminate opaque materials. A pilot plant was built and the tests were conducted with the three samples separately. With all samples, it was possible to attain approximately 99% content in glass in the glass products, but the recovery of glass was related with the feed particle size. The finer the feed was, the lower the percentage of glass recovered in the glass product. The results show that each one of the separation processes was needed for product enrichment. The organic matter recovered in the glass product was high, ranging from 0.76% to 1.13%, showing that drying was not sufficient in the tests but that it is a key process for the success of the operation.

Fine grain separation for the production of biomass fuel from mixed municipal solid waste

The main goal of the project MARSS (Material Advanced Sustainable Systems) is to build a demonstration plant in order to recover a renewable biomass fuel suitable for the use in biomass power plants out of mixed municipal solid waste (MMSW). The demonstration plant was constructed in Mertesdorf (Germany), working alongside an existing mechanical–biological treatment plant, where the MMSW is biological dried under aerobe conditions in rotting boxes. The focus of the presented sorting campaign was set on the processing of fine grain particles minor than 11.5mm which have the highest mass content and biogenic energy potential of the utilized grain size fractions. The objective was to produce a biomass fuel with a high calorific value and a low content of fossil (plastic, synthetic) materials while maximizing the mass recovery. Therefore, the biogenic components of the dried MMSW are separated from inert and fossil components through various classification and sifting processes. In three experimental process setups of different processing depths, the grain size fraction 4–11.5mm was sifted by the use of air sifters and air tables.

Life Cycle Assessment of Mixed Municipal Solid Waste: Multi-input versus multi-output perspective

This paper analyses four strategies for managing the Mixed Municipal Solid Waste (MMSW) in terms of their environmental impacts and potential advantages by means of Life Cycle Assessment (LCA) methodology. To this aim, both a multi-input and a multi-output approach are applied to evaluate the effect of these perspectives on selected impact categories. The analyzed management options include direct landfilling with energy recovery (S-1), Mechanical-Biological Treatment (MBT) followed by Waste-to-Energy (WtE) conversion (S-2), a combination of an innovative MBT/MARSS (Material Advanced Recovery Sustainable Systems) process and landfill disposal (S-3), and finally a combination of the MBT/MARSS process with WtE conversion (S-4). The MARSS technology, developed within an European LIFE PLUS framework and currently implemented at pilot plant scale, is an innovative MBT plant having the main goal to yield a Renewable Refined Biomass Fuel (RRBF) to be used for combined heat and power production (CHP) under the regulations enforced for biomass-based plants instead of Waste-to-Energy systems, for increased environmental performance. The four scenarios are characterized by different resource investment for plant and infrastructure construction and different quantities of matter, heat and electricity recovery and recycling. Results, calculated per unit mass of waste treated and per unit exergy delivered, under both multi-input and multi-output LCA perspectives, point out improved performance for scenarios characterized by increased matter and energy recovery. Although none of the investigated scenarios is capable to provide the best performance in all the analyzed impact categories, the scenario S-4 shows the best LCA results in the human toxicity and freshwater eutrophication categories, i.e. the ones with highest impacts in all waste management processes.

How should greenhouse gas emissions be taken into account in the decision making of municipal solid waste management procurements? A case study of the South Karelia region, Finland

The ongoing trend in the public sector is to make more sustainable procurements by taking into account the impacts throughout the entire life cycle of the procurement. Despite the trend, the only deciding factor can still be the total costs. This article answers the question of how greenhouse gas (GHG) emissions should be taken into account in municipal solid waste (MSW) management when selecting an incineration plant for source separated mixed MSW. The aim is to guide the decision making of MSW management towards more environmentally friendly procurements.The study was carried out by calculating the global warming potentials (GWPs) and costs of mixed MSW management by using the waste composition from a case area in Finland. Scenarios of landfilling and combustion in three actual waste incineration plants were used to recognise the main processes that affect the results. GWP results show that the combustion of mixed MSW is a better alternative than landfilling the waste. The GHG results from combustion are greatly affected by emissions from the combustion and substituted energy production. The significance of collection and transportation is higher from the costs’ perspective than from the point of view of GHG emissions. The main costs, in addition to collection and transportation costs, result from the energy utilization or landfilling of mixed MSW.When tenders are invited for the incineration location of mixed MSW, the main focus should be: What are the annual electricity and heat recovery efficiencies and which are the substituted fuels in the area? In addition, in the case of a fluidized bed combustor it is crucial to know the combusted share of mixed MSW after preparing solid recovered fuel (SRF) and the treatment of rejects. The environmental criteria for the waste incineration plant procurements should be made in order to obtain clear instructions for the procurement units. The results can also be utilized more widely. The substituted fuels in the area and the effect of the plant location on the utilization of the produced energy can already be identified when planning an appropriate site for the waste incineration plant.

Separation by particle shape — The RecGlass device

Solid waste are today new ores needing innovative separation techniques or adaptations of the current ones used, for instance in mineral processing, for the recovery of materials. “RecGlass” is a device developed to separate materials with similar density but exhibiting different particle shape. It is inspired in the “vanner” and in the “Bartles cross belt” processes but it is applied in dry conditions to separate materials with specific weight slightly above 2g/cm3 and particles in the range size 4 to 12mm. In the work presented, it was applied to the processing of the heavy reject of Mechanical Biological Treatment of mixed Municipal Solid Waste aiming at the recovery of glass, the main constituent of this product, which is landfilled today, and to eliminate the stones, generally the second main inert constituent. The glass particles are predominantly flat while stones are sub-spherical. The core of the equipment is an inclined belt moving upwards. The particles are continuous and steadily fed by a vibrating feeder placed above the belt. Depending on the operational variables such as belt speed and slope and feed position, and also on the belt surface material, the flat particles move upwards and the round ones roll down.In the present paper the equipment is described and the physical principles of the concentration process are explained. Using samples of two different plants it was shown that it is possible to achieve a significant upgrading in glass. With a sample from one plant the glass content was increased from 88% to 92% while with a completely different sample, from another plant, the glass content in the process feed was 59%, attaining 71% in the glass concentrate. The recovery of the glass in the glass concentrate reached more than 80% by removing about 80% of the stones.