PCDD/Fs in the soils in the province of Trento: 10 years of monitoring.

This paper presents a 10-year overview of the dioxins and furans (PCDD/Fs) content in soils in the province of Trento (Italy). The aim was to compare the results found in the Valsugana valley where there is a steel-making plant with other locations within the province. During 2002 and from 2005 to 2010, campaigns were carried out in order to obtain a background reference in terms of micropollutants, in view of the possible construction of a municipal solid waste (MSW) incinerator in Trento. In 2009, a campaign was performed for the environmental characterization of the Valsugana valley, the town of Trento and its surroundings, in order to help assess the impact of the steel-making plant. In 2012, another campaign was carried out by the Department of Civil and Environmental Engineering of Trento, in order to monitor the soils in the area around the steel mill. All the campaigns showed relatively low concentrations of PCDD/Fs, both in protected areas and in the areas close to the industrial plants. No critical situations were identified, as also confirmed by an estimation of the potential daily PCDD/F intake by children subject to accidental ingestion of soil.

Assessment of the local role of a steel making plant by POPs deposition measurements.

Atmospheric depositions of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs) were monitored at three sites in the vicinity of a steel making plant, located in an Italian alpine valley. A high variability in the deposition of PCDD/Fs was observed. The influence of the plant was noticeable at two of the sampling sites. However, as the congener profiles demonstrated, wood burning for domestic heating is an additional source of PCDD/Fs for the area under investigation, and this interferes with the characterization of the emissions from the steel plant. The influence of the plant, in terms of PCDD/F deposition, was not noticeable at the most distant site (2km), where an extremely high peak of PCDD/F deposition was measured during the period from 12 January-22 February 2012. The comparison between the congener distribution of PCDD/Fs observed in this sample and the fingerprints of different sources could justify the attribution of this anomalous peak to a possible episode of domestic waste combustion. In order to find a better correlation between the deposition to soil and emissions from the plant, the congener distribution of PCBs was studied. The PCB profiles observed at the three sites well reproduced the average profile found in samples of ash retained by the bag filter of the plant. Thus the monitoring of PCB deposition is an interesting starting point to calibrate dispersion models to assess the impact of steel making activities.

A proposal for a diet-based local PCDD/F deposition limit.

This study proposes a method to estimate the maximal tolerable value for the atmospheric deposition of dioxins (PCDD/Fs) to soil. The case study for the application of this methodology is an Alpine valley where a steel production plant is present. In order to estimate the limit value for the PCDD/F deposition, consolidated food chain models were applied, but were adapted to be run backwards with respect to their original formulation, by starting from the diet of people living in the region and from the PCDD/F Tolerable Daily Intake value proposed by the World Health Organization. For this case study, the estimated limit value was 2.30 pg WHO-TEQ m(-2) d(-1) when only local diary products were taken into account and 1.91 pg WHO-TEQ m(-2) d(-1) when also the role of local cereals and vegetables was considered. The average PCDD/F deposition measured in the same region during a monitoring campaign was lower than the above limit values (1.40 pg WHO-TEQ m(-2) d(-1)). Indications on how to consider the contribution of meat and fish are provided too. The approach proposed in this paper represents a useful tool to assess the acceptable overall deposition for a specific region.

Web-GIS oriented systems viability for municipal solid waste selective collection optimization in developed and transient economies.

Municipal solid waste management is a multidisciplinary activity that includes generation, source separation, storage, collection, transfer and transport, processing and recovery, and, last but not least, disposal. The optimization of waste collection, through source separation, is compulsory where a landfill based management must be overcome. In this paper, a few aspects related to the implementation of a Web-GIS based system are analyzed. This approach is critically analyzed referring to the experience of two Italian case studies and two additional extra-European case studies. The first case is one of the best examples of selective collection optimization in Italy. The obtained efficiency is very high: 80% of waste is source separated for recycling purposes. In the second reference case, the local administration is going to be faced with the optimization of waste collection through Web-GIS oriented technologies for the first time. The starting scenario is far from an optimized management of municipal solid waste. The last two case studies concern pilot experiences in China and Malaysia. Each step of the Web-GIS oriented strategy is comparatively discussed referring to typical scenarios of developed and transient economies. The main result is that transient economies are ready to move toward Web oriented tools for MSW management, but this opportunity is not yet well exploited in the sector.

Multi-step approach for comparing the local air pollution contributions of conventional and innovative MSW thermo-chemical treatments.

In the sector of municipal solid waste management the debate on the performances of conventional and novel thermo-chemical technologies is still relevant. When a plant must be constructed, decision makers often select a technology prior to analyzing the local environmental impact of the available options, as this type of study is generally developed when the design of the plant has been carried out. Additionally, in the literature there is a lack of comparative analyses of the contributions to local air pollution from different technologies. The present study offers a multi-step approach, based on pollutant emission factors and atmospheric dilution coefficients, for a local comparative analysis. With this approach it is possible to check if some assumptions related to the advantages of the novel thermochemical technologies, in terms of local direct impact on air quality, can be applied to municipal solid waste treatment. The selected processes concern combustion, gasification and pyrolysis, alone or in combination. The pollutants considered are both carcinogenic and non-carcinogenic. A case study is presented concerning the location of a plant in an alpine region and its contribution to the local air pollution. Results show that differences among technologies are less than expected. Performances of each technology are discussed in details.

PCDD/F enviromental impact from municipal solid waste bio-drying plant.

The present work indentifies some environmental and health impacts of a municipal solid waste bio-drying plant taking into account the PCDD/F release into the atmosphere, its concentration at ground level and its deposition. Four scenarios are presented for the process air treatment and management: biofilter or regenerative thermal oxidation treatment, at two different heights. A Gaussian dispersion model, AERMOD, was used in order to model the dispersion and deposition of the PCDD/F emissions into the atmosphere. Considerations on health risk, from different exposure pathways are presented using an original approach. The case of biofilter at ground level resulted the most critical, depending on the low dispersion of the pollutants. Suggestions on technical solutions for the optimization of the impact are presented.

Material and energy recovery in integrated waste management systems: an innovative approach for the characterization of the gaseous emissions from residual MSW bio-drying.

In the sector of residual municipal solid waste management an increasing attention is put towards the role of biological treatments like bio-drying and bio-stabilization in order to decrease the need of landfilling volumes. The literature shows a lack of information concerning the emission factor of pollutants released from these processes. The available data are generally spot characterizations of concentration and air flow-rate that are used together in order to assess the emission factors. This approach caused significant differences among the available data as the release of pollutants is not steady. This paper belongs to a group of six papers concerning a research on material and energy recovery in integrated waste management systems, developed by a network of five universities. The contribution of the University of Trento, focuses on the bio-drying process with the following targets: (a) developing an innovative low cost method of sampling/measurement able to take into account the dynamics of release of pollutants; (b) checking the efficiency of a bio-filter; (c) verifying the variability of generation of some pollutants; (d) generating emission factors. The research was developed using a bio-drying pilot plant. As a treatment of the process air, the bio-reactor was coupled with a bio-filter. The emissions were characterized using an original approach based on the adoption of two measurement chambers suitable for hosting passive samplers. The passive samplers allowed the characterization of VOCs, N(2)O, NH(3) and H(2)S. A bio-chemical model, useful for energy and mass balances, supported the interpretation of the presented bio-drying run.

A contribution for a correct vision of health impact from municipal solid waste treatments.

In agreement with the European Union Directives concerning health risks targets, in the present paper data regarding the health risk from different strategies of waste treatment, in particular concerning dioxin emissions, are presented. Three options are considered for municipal solid waste treatment: incineration (with best available technologies (BATs)), an anaerobic/aerobic treatment and an aerobic treatment before landfilling. The process of biostabilization varies case by case but differences between simplified approaches and BAT solutions have been pointed out. In the paper it is also pointed out how important the local context for the health risk from PCDD/F release is: the height of gas release into the atmosphere, the emitted gas velocity and the temperature of release become the most important parameters (apart from the overall amount released) in areas where the population may be close to the plant or where there is agricultural activity in the proximity. However, all the three solutions give an acceptable risk.

Trends in the management of residual municipal solid waste.

In agreement with European Union directives, the integrated management of municipal solid waste must be developed ensuring a balanced relationship between the streams of selective collection and the one regarding the residual waste. A theoretical scenario is made where the residual municipal solid waste is composed only of non-recyclable fractions. An important aspect concerns the role of the organic fraction as selective collection can significantly decrease its content in the residual waste. This paper focuses on the planning, design and management consequences of this unsteady scenario. The treatments that are considered are: combustion, gasification, pyrolysis, integrated thermal plants, aerobic mechanical-biological treatments, anaerobic mechanical-biological treatments and other types of treatment. The considerations are based on the experience of the authors not only in terms of development of research but also in terms of transfer of the research results to the real scale, and knowledge of the state-of-the-art of the sector.

Bio-drying of grape marc and other biomass: a comparison.

The winery industry produces every year in the world about 270 millions of hectolitres of wine. A consequent amount of grape marc is then generated that has to be somehow treated and processed. For this reason a technique to treat grape marc (bio-drying) was studied and applied at the University of Trento. Grape marc, as is, is not suitable for direct combustion because of its high water content. By bio-drying the lower heating value has been increased up to the limit for a good combustion. This result allows a decentralized management of a grape marc drying differently from the conventional solutions.

Critical analysis of PCDD/F emissions from anaerobic digestion.

This paper concerns a particular aspect of anaerobic digestion, that is the emission of PCDD/F in different scenarios where this biological process is present. The considered scenarios are: anaerobic digestion of automatically sorted Municipal Solid Waste, source separated organic fraction of Municipal Solid Waste treated in an anaerobic digester, anaerobic process developed in a Municipal Solid Waste sanitary landfill. Not always the emissions taken into account are related to combustion of biogas from anaerobic digestion: the loss of biogas from a landfill causes an uncontrolled emission of PCDD/F. The paper is completed with an analysis of the role of anaerobic digestion in PCDD/F inventories and health risk considerations. Indeed the most detailed inventories offer emission factors useful for a deep understanding of the phenomenon of PCDD/F release into the atmosphere. Concerning health risk, some suggestions in order to decrease it are proposed.

Lower heating value dynamics during municipal solid waste bio-drying.

In agreement with the new European Union directives concerning the valorization of materials and energy recovery, Municipal Solid Waste (MSW) management is, in general based on an integrated approach characterized by a combination of different treatment processes. The bio-mechanical treatment (BMT) of MSW is an increasing option in Europe either as a pre-treatment before landfilling or as a pre-treatment before combustion. In this context the research on the bio-drying process is not fully developed. In the present paper the Lower Heating Value (LHV) dynamics during MSW bio-drying has been assessed. Measurements were made using a pilot scale bio-dryer that allows the recording of data as air flow, temperature (at the entrance, at the exit and inside the waste), and weight loss. An initial characterization of the MSW completes the input data. Results give information on the dynamics of the main process parameters (humidity, volatile solids, ammonia, Lower Heating Value) and also of additional parameters.

Modelling of PCDD/F release from MSW bio-drying.

In the present work, an experimentation was carried out to study the behaviour of PCDD/F during the process of municipal solid waste (MSW) bio-drying. This process belongs to the biological mechanical treatment (BMT) options and is aimed to the dewatering of MSW thanks to the biological exothermal reactions (thermal drying, on the contrary, needs an external heat source as methane). The result is a decrease of waste weight and an increase of lower heating value (as the energy content refers to a lower amount of waste). Of course, the overall energy availability does not increase, but the characteristics of bio-drying are interesting as a way for refuse derived fuel generation: glass, metals and inert removals are easier after bio-drying. The literature of the sector shows only few data on PCDD/F emission to air from BMT. Anyway, in the present work an original theory has been put forward in order to explain the enrichment of PCDD/F in the air exiting the biological processes. The role of the initial PCDD/F concentration in the ambient air entering the plant is obviously taken into account. The results of the developed experimentation and the following elaborations point out that PCDD/F could be freed from the volatile solids consumed during the process. The different amount of PCDD/F in the waste and the different consumption of volatile solids depending on the biological process can explain the different PCDD/F emission factors available in the literature.

The role of bio-mechanical treatments of waste in the dioxin emission inventories.

PCDD/Fs are one of the most studied molecules in the world because of their toxicity. In the last years the toxicity of these compounds has been analyzed in details. For years PCDD/F inventories have pointed out the significant role of municipal solid waste (MSW) incinerators in the overall balance. Recently, thanks to new regulations on PCDD/F emissions, in a few countries this scenario is changing: it can be demonstrated that modern MSW incinerators can play a secondary role even if the percentage of MSW sent to combustion has increased. In the latest inventories an unconventional source of PCDD/F has appeared: in nineties some biogas characterizations have demonstrated that there is a release of PCDD/F from MSW sanitary landfills. In addition, the combustion of collected biogas can generate not negligible amounts of PCDD/F. A new question can be put: does the MSW contribute with other management options to the overall balance of PCDD/F? The present work points out that a detailed inventory should take into account also the PCDD/F release from bio-mechanical treatment plants (both composting and bio-drying/bio-stabilization plants). However the contribution from this option is secondary when it is compared with the one from old MSW incinerators.

Some research perspectives on emissions from bio-mechanical treatments of municipal solid waste in Europe.

The bio-mechanical treatment of Municipal Solid Waste is an increasing option in Europe either as a pre-treatment before landfilling or as a pre-treatment before combustion. The present work deals with the problem of assessment of significant data related to emissions to air from bio-mechanical treatments. Reliable data are necessary for the development of: a) Life Cycle Assessment studies; b) verification of compliance with existing regulations; c) environmental impact studies assessment. In order to point out some lack of knowledge about bio-mechanical treatments, some results of a Life Cycle Assessment study on Municipal Solid Waste bio-stabilization treatment have been reported and analysed. Indeed, during the development of that Life Cycle Assessment, some problems were found regarding the availability and the quality of emission data from Municipal Solid Waste mechanical biological treatment. Concerning existing regulations, in Europe we can find both countries with enhanced approaches, and countries with a soft approach. In the second case, for instance, a few Italian regions adopted local regulations in order to improve the quality of the environmental regulation as the national one has been considered inadequate. The environmental impact assessment of bio-mechanical treatments is not still as developed as options such as incineration. The reason is that the impact of a bio-mechanical treatment plant is considered low. On the contrary it can be demonstrated that a greater attention must be paid in the case of non optimised technologies and large plants.