Materials selection for superheater tubes in municipal solid waste incineration plants

Corrosion reduces the lifetime of municipal solid waste incineration (MSWI) superheater tubes more than any other cause. It can be minimized by the careful selection of those materials that are most resistant to corrosion under operating conditions. Since thousands of different materials are already known and many more are developed every year, here the selection methodology developed by Prof. Ashby of the University of Cambridge was used to evaluate the performance of different materials to be used as MSWI superheater tubes. The proposed materials can operate at steam pressures and temperatures over 40 bars and 400ºC, respectively. Two case studies are presented: one makes a balanced selection between mechanical properties and cost per thermal unit; and the other focuses on increasing tube lifetime. The balanced selection showed that AISI 410 martensitic stainless steel (wrought, hard tempered) is the best candidate with a good combination of corrosion resistance, a relatively low price (0.83-0.92 e/kg) and a good thermal conductivity (23-27 W/m K). Meanwhile, Nitronic 50/XM-19 stainless steel is the most promising candidate for longterm selection, as it presents high corrosion resistance with a relatively low price (4.86-5.14 e/kg) compared to Ni-alloys.

Privatization, cooperation and costs of solid waste services in small towns

This paper analyzes the cost implications of privatization and cooperation in the provision of solid waste services for a sample of small municipalities. In conducting this empirical analysis, a survey is first designed and administered to municipalities in the Spanish region of Aragon, and then an estimation of the determinants of service costs is undertaken, considering the possible endogeneity of delivery choices. Our findings indicate that cooperation is more effective than privatization in saving costs. Both production forms can enable small municipalities to cut costs by exploiting scale economies. However, the fact that inter-municipal cooperation involves lower transaction costs and is less likely to be affected by competition problems would seem to account for the fact that it is a more effective way of reducing costs.

Intermunicipal cooperation and privatization of solid waste services among small municipalities in Spain

The aim of this paper is to analyze the effects of intermunicipal cooperation and privatization on the delivery costs of urban solid waste services. The results of our empirical analysis, which we conducted among a sample of very small municipalities, indicate that small towns that cooperate incur lower costs for their waste collection service. Cooperation also raises collection frequency and improves the quality of the service in small towns. By contrast, the form of production, whether it is public or private, does not result in systematic differences in costs. Interestingly, the degree of population dispersion has a significant positive relation with service costs. No evidence of scale economies is found because, it would seem, small municipalities exploit them by means of intermunicipal cooperation.

Measuring the efficiency in Spanish municipal refuse collection services

The objective of this study is to analyse the technical or productive efficiency ofthe refuse collection services in 75 municipalities located in the Spanish regionof Catalonia. The analysis has been carried out using various techniques. Firstly we have calculated a deterministic parametric frontier, then a stochastic parametric frontier, and finally, various non-parametric approaches (DEA and FDH). Concerning the results, these naturally differ according to the technique used to approach the frontier. Nevertheless, they have an appearance of solidity, at least with regard to the ordinal concordance among the indices of efficiency obtained by the different approaches, as is demonstrated by the statistical tests used. Finally, we have attempted to search for any relation existing between efficiency and the method (public or private) of managing the services. No significant relation was found between the type of management and efficiencyindices

Factors influencing privatization of urban solid waste collection: some evidence from Spain

In this paper we analyse some of the organisational aspects of the urban solid waste collection and, in particular, the privatization modality of contracting out. We start by discussing some of the theoretical aspects of contracting out. We then specify and estimate an explanatory model on a sample of municipalities that we surveyed. Our purpose is twofold: on the one hand, we identify the economic factors at work when deciding to contract out the service and, on the other hand, we analyse the role of ideological factors in choosing between the public production of the service or contracting it out. The results show a significant effect of the demand for waste collection on contracting out. There also appears to be a neighbouring effect as the municipalities close to other cities that contract out are also more prone to do so. Finally, the decisions to contract seem to have been motivated by pragmatic rather than ideological reasons.

Measuring the efficiency in Spanish municipal refuse collection services

The objective of this study is to analyse the technical or productive efficiency ofthe refuse collection services in 75 municipalities located in the Spanish regionof Catalonia. The analysis has been carried out using various techniques. Firstly we have calculated a deterministic parametric frontier, then a stochastic parametric frontier, and finally, various non-parametric approaches (DEA and FDH). Concerning the results, these naturally differ according to the technique used to approach the frontier. Nevertheless, they have an appearance of solidity, at least with regard to the ordinal concordance among the indices of efficiency obtained by the different approaches, as is demonstrated by the statistical tests used. Finally, we have attempted to search for any relation existing between efficiency and the method (public or private) of managing the services. No significant relation was found between the type of management and efficiencyindices

Factors influencing privatization of urban solid waste collection: some evidence from Spain

In this paper we analyse some of the organisational aspects of the urban solid waste collection and, in particular, the privatization modality of contracting out. We start by discussing some of the theoretical aspects of contracting out. We then specify and estimate an explanatory model on a sample of municipalities that we surveyed. Our purpose is twofold: on the one hand, we identify the economic factors at work when deciding to contract out the service and, on the other hand, we analyse the role of ideological factors in choosing between the public production of the service or contracting it out. The results show a significant effect of the demand for waste collection on contracting out. There also appears to be a neighbouring effect as the municipalities close to other cities that contract out are also more prone to do so. Finally, the decisions to contract seem to have been motivated by pragmatic rather than ideological reasons.

Avaluació ambiental de la recollida de residus municipals de Sant Boi de Llobregat

La gestió dels residus municipals ha d’avançar cap a la sostenibilitat per tal de poder fer front al gran volum de residus que es generen actualment i no malmetre el medi ambient. Aquest fet motiva a l’elaboració d’aquest projecte que es centra en l’anàlisi del procés de recollida dels residus municipals. L’estudi realitza en primer lloc una avaluació ambiental de la recollida global i una avaluació ambiental específica de la recollida de la fracció Resta mitjançant el programari SIMUR (desenvolupada per l’Agència d’Ecologia Urbana de Barcelona). Amb aquesta eina de simulació de models de gestió de residus municipal es calcula el balanç de massa, el balanç energètic, el balanç d’emissions i el balanç econòmic del procés de recollida. La metodologia per al desenvolupament de la segona fase del projecte es basa en la realització de treball de camp per al disseny de taules descriptives dels circuits de recollida de la fracció Resta, que permeten comparar-los entre sí i aconseguir l’objectiu d’avaluar l’eficiència dels sistemes de recollida de càrrega lateral i posterior de la fracció. L’assoliment dels objectius permet fer-se una idea de l’estat actual de la recollida dels residus de Sant Boi, identificant-ne els punts forts i febles i plantejant propostes de millora encarades a aconseguir una futura generació i recollida de residus més respectuosa amb l’entorn.

Avaluació de l'aptitud de bioestabilitzats com a esmena orgànica per a la rehabilitació de sòls

L’objectiu d’aquest estudi ha estat avaluar l’efecte que té sobre algunes propietats fisicoquímiques del sòl i el creixement de plantes, l’adició del producte compostat obtingut a partir de la fracció orgànica dels residus sòlids urbans de recollida no selectiva, material anomenat bioestabilitzat. S’ha dut a terme un bioassaig amb blat (Triticum aestivum), utilitzant bioestabilitzat procedent de dues plantes de tractament mecànic i biològic, Vacarisses i Mataró, que s’ha aplicat a diferents dosis en un sòl de baixa qualitat. S’ha observat una relació positiva entre el creixement del blat i la dosis de bioestabilitzat aplicada. Pel que fa a la germinació, ha estat lleugerament estimulada per les dosis intermèdies de bioestabilitzat assajades. En quant a les propietats fisicoquímiques del sòl, s’ha observat un increment de la salinitat en funció de la dosis de bioestabilitzat aplicada, que en les més elevades podria ser problemàtica. També, el contingut de matèria orgànica ha augmentat de manera proporcional a la dosis, cosa que ha millorat les propietats físiques del sòl. Per altra banda, s’han trobat continguts d’impropis (vidre, plàstic ...) i concentracions d’alguns metalls pesants bastant elevades, així com una considerable variabilitat entre les partides de bioestabilitzat. Finalment, es conclou que abans de permetre l’aplicació de bioestabilitzat per a la rehabilitació de sòls degradats, cal aprofundir més en l’estudi d’aquest material.

Aggregate material formulated with MSWI bottom ash and APC fly ash for use as secondary building material

The main goal of this paper is to obtain a granular material formulated with Municipal Solid Waste Incinerarion (MSWI) bottom ash (BA) and air pollution control (APC) ash to be used as secondary building material. Previously, an optimum concrete mixture using both MSWI residues as aggregates was formulated. A compromise between the environmental behaviour and the economy of the process was considered. Unconfined compressive strength and abrasion resistance values were measured in order to evaluate the mechanical properties. From these results, the granular mixture was not suited for certain applications owing to the high BA/APC content and low cement percentages used to reduce the costs of the final product. Nevertheless, the leaching test performed showed that the concentrations of all heavy metals were below the limits established by the current Catalan legislation for their reutilization. Therefore, the material studied might be mainly used in embankments, where high mechanical properties are not needed and environmental safety is assured.

Renda familiar disponible bruta, factor socioeconòmic associat amb la generació de residus sòlids urbans per habitant en els municipis de l'Àrea Metropolitana de Barcelona : anàlisis de la intensitat i forma de correlació i evolució dels nivells de generació 2000-2009

En aquest treball s’utilitzen les Quantitats de Residus Generats per Habitant (KRGH) en els diferents municipis de l’entitat administrativa de l’Àrea Metropolitana de Barcelona (AMB) durant la primera dècada del segle XXI (2000 - 2011) com a indicador de sostenibilitat en matèria de Residus Sòlids Urbans (RSU). S’estudia la relació d’aquesta variable amb la Renda Familiar Disponible (RFD) i s’analitza l’evolució dels nivells de generació al llarg de la sèrie històrica per a grups de municipis amb nivells de generació ben diferenciats amb objecte d’avaluar l’efecte produït pels successos amb més impacte en matèria de gestió tal és la introducció del cànon de residus i discutir si es donen situacions d’iniquitat derivades del sistema de finançament dels serveis de gestió de residus.

Aggregate material formulated with MSWI bottom ash and APC fly ash for use as secondary building material

The main goal of this paper is to obtain a granular material formulated with Municipal Solid Waste Incinerarion (MSWI) bottom ash (BA) and air pollution control (APC) ash to be used as secondary building material. Previously, an optimum concrete mixture using both MSWI residues as aggregates was formulated. A compromise between the environmental behaviour and the economy of the process was considered. Unconfined compressive strength and abrasion resistance values were measured in order to evaluate the mechanical properties. From these results, the granular mixture was not suited for certain applications owing to the high BA/APC content and low cement percentages used to reduce the costs of the final product. Nevertheless, the leaching test performed showed that the concentrations of all heavy metals were below the limits established by the current Catalan legislation for their reutilization. Therefore, the material studied might be mainly used in embankments, where high mechanical properties are not needed and environmental safety is assured.

Empirical analysis of solid management waste costs: Some evidence from Galicia, Spain

This paper analyses the factors that determine solid waste service costs. The empirical analysis is based on information derived from a survey conducted in a sample of Galician municipalities. The results reveal economies of scale in municipalities of fewer than 50,000 inhabitants, such that cooperation between these municipalities could lead to cost savings. It also appears that private delivery is not cheaper than public delivery. Finally, designating a larger proportion of the total waste volume to recycling does not imply greater costs.

Italy's urban waste metabolism

The problem of waste management is causing growing concern due to increasing generation rates, the emissions into soil, water and air, the social conflicts derived from the election of disposal sites and the loss of resources and energy among others. In this work, an innovative methodology is used to enable a better understanding of the waste generation and management system in Italy. Two new waste indicators are built to complement the conventional indicators used by official statistics. Then a multi-scale analysis of the Density of Waste Disposed (DWD) is carried out to highlight the territorial diversity of waste performances and test its contribution to detect plausible risky areas. Starting from Italian regions, the scale down goes on to the provincial level and, only for the region of Campania, the municipal one. First, the analysis shows that the DWD is able to complement the information provided by the conventional waste indicators. Second, the analysis shows the limitations of using a unique institutional solution to waste management problems. In this sense the multi-scale analysis provides with a more realistic picture of Italian waste system than using a single scale.

Una exploración completa de los costes de servicio de residuos sólidos

La literatura económica sobre los servicios municipales de residuos sólidos en España es muy escasa, aun cuando estos servicios han sido objeto d'intensas reformas organizativas y regulatorias. En esta investigación se estudia su estructura de costes con el objetivo de explicar la variabilidad entre los municipios de los costes soportados por el servicio. Se determina una función de costes y se estima de forma paramétrica. Los resultados del análisis empírico permiten estudiar la existencia de economías de escala con el output, y el efecto de algunos factores directamente asociados con el servicio como el grado de residuos selectivos, la frecuencia de recogida o la existencia de instalaciones de depósito en el municipio. Además, se analiza el impacto sobre los costes de otros factores como la densidad de población, los niveles salariales, la estacionalidad y la forma de producción, pública o privada.