E. Brizio

Perspectives and limits for cement kilns as a destination for RDF

RDF, the high calorific value fraction of MSW obtained by conventional separation systems, can be employed in technological plants (mainly cement kilns) in order to obtain a useful energy recovery. It is interesting and important to evaluate this possibility within the general framework of waste-to-energy solutions. The solution must be assessed on the basis of different aspects, namely: technological features and clinker characteristics; local atmospheric pollution; the effects of RDF used in cement kilns on the generation of greenhouse gases; the economics of conventional solid fuels substitution and planning perspectives, from the point of view of the destination of RDF and optimal cement kiln policy. The different experiences of this issue throughout Europe are reviewed, and some applications within Italy are also been considered. The main findings of the study are that the use of RDF in cement kilns instead of coal or coke offers environmental benefits in terms of greenhouse gases, while the formation of conventional gaseous pollutants is not a critical aspect. Indeed, the generation of nitrogen oxides can probably be lower because of lower flame temperatures or lower air excess. The presence of chlorinated micro-pollutants is not influenced by the presence of RDF in fuel, whereas depending on the quality of the RDF, some problems could arise compared to the substituted fuel as far as heavy metals are concerned, chiefly the more volatile ones.

Atmospheric pollutants and air quality effects: limitation costs and environmental advantages (a cost–benefit approach)

In order to improve the air quality in some very critical areas in Europe, it is required to limit the contaminant flux coming from different sources (thermal and industrial plants, transport systems, cars, and other technological apparatus). This limitation in many cases corresponds to important investment costs, and normally to a substantial increase in the operative costs; but, from the other side, by the intervention on the emitted pollutant loads it can be obtained a condition of better air quality, with consequent lower externality costs, chiefly with reference to the exposed population. By comparing the two aspects of increasing costs, and in particular the slope of the increasing trend, and from the other side the improvement in air quality, it is possible to identify as a compromise a convenient definition of the optimal intervention that must be realized, and it is possible to establish the performances that must be obtained, by arriving to an acceptable air quality with a sustainable cost. This strategy of identification of the optimal point between these two opposite trends has been illustrated in the present work, and some practical examples of implementation of different limitation strategies and consequent environmental results are presented; these results concern different scale solutions, and different geographic situations.

The influence of different mixing heights on the ECOSENSE model results at a local scale

Abstract The ECOSENSE software has been created and applied as part of the European long term project called ExternE, a research program devoted to the assessment of external costs due to electricity production. The ECOSENSE model starts from the emission rates of a facility, calculates the yearly mean concentrations of the pollutants at the ground level on the basis of atmospheric dispersion models and characterises the subjects exposed to the pollutants in the considered area. After this, proper epidemiological exposure-response and toxicological dose-response functions are applied to determine the impact on the receptors. Finally, the methodology can monetise the calculated physical impact on the basis of selected economic evaluations. The aim of this study is to apply the software to real cases at a local scale and to compare the results based on different mixing height inputs, since the determination of this meteorological parameter is quite complex. Such a study is useful to have an idea of the sensitivity of the ECOSENSE model and make it a user-friendly instrument for administrations; this can help to create a harmonic approach to the problem of atmospheric pollution and impact evaluation. For specified facilities and meteorological conditions and, in particular, for a 100,000 t/y MSW incinerator, the mixing height can be approximated by a constant value of 1000 m throughout the year and the final results will have deviations that are lower than 10%.

Results of atmospheric dispersion model for the localization of a MSW incinerator

The present study reports the attempt to localize a MSW incinerator, starting from three proposed sites, on the basis of the atmospheric transport and dispersion modelling. The considered area, around Turin, in North-Western Italy, is characterized by a high percentage of hours of calm wind, so the choice of the atmospheric model is very important in order to have reliable and convincing results. In the present study we used the AERMOD model by the U.S. EPA, that is a hybrid atmospheric dispersion model which can treat the calm hours within a more restrained computational time with respect to Eulerian or Lagrangian models. The investigated issue is generally a very delicate and thorny argument because of the natural opposition of the people against this kind of plant. The first thing to do to treat the localization of a MSW incinerator is to calculate the concentrations at the ground level due to the emitted pollutants and to compare them to the air quality regulations; secondly, one can think about the possibility of building a district heating system or distributing technological vapour service to industrial users, avoiding the respective emission of pollutants. In practice, the concentrations at the ground level when the incinerator is placed in the three proposed sites are very comparable and, for each site, much smaller than the air quality regulations and the measured levels of the area. The best localization is then determined by the possibility of realising a large district heating system

Modelling the effects of traffic emissions on the air quality

European directives 1999/30/CE and 2000/69/CE set severe limits for ambient concentrations of sulphur dioxide, nitrogen dioxide, fine particles, lead, benzene and carbon monoxide; in particular, the concentrations of PM10 and nitrogen dioxide, measured in urban areas (even in towns of 20,000 inhabitants) of Northern Italy, often don’t respect the air quality limits. The forementioned pollution levels are heavily determined by traffic emissions. In order to match the imposed limits, public administrations have to plan strong actions such as the restriction of car circulation; therefore, it is very important to have at their disposal a reliable instrument to model the effects of different traffic restriction policies on the air quality. In the present paper we modelled the effects of the traffic emissions on the air quality for two streets of a 50,000-inhabitant town in Piedmont, NW Italy, by means of different atmospheric dispersion models, the Industrial Source Complex 3 model (U.S. EPA), AERMOD (U.S. EPA) and the Operational Street Pollution Model (N.E.R.I., Denmark). We also had at our disposal measured concentrations for the pollutants CO and NOx in the analysed streets, so we could validate the results. We obtained the best results by applying the OSPM model: the mean deviation from the measured concentrations of CO came out between 50 % and 80 %, according to the analysed period, while ISC3 and AERMOD results were 10–15 % worse. Consequently, the OSPM model has been applied to foresee air quality scenarios corresponding to different traffic restriction policies.

Comparison of locations for a MSW incineration plant

The ExternE project is a research program of the European Commission devoted to the assessment of the external costs associated to airborne pollution. The ExternE methodology individuates the emission rates, calculates the year mean concentrations of the pollutants at the ground level on the basis of atmospheric dispersion models (e.g. AERMOD) and individuates the subjects exposed to the pollutants in the considered area (the number, the distribution and the age classes of the hit populations, types and distribution of crops). After that, proper exposure-response functions are applied in order to determine the impacts on the various receptors. In particular, impacts on human health, crops, building materials, forests and ecosystems can be calculated. Finally, the methodology can monetize the calculated physical impacts on the basis of particular econometric methods. The described methodology has been applied in order to find the best locality starting from three proposed sites for a municipal solid waste incinerator for the city of Turin, in North-Western Italy, by minimizing the total damage due to the emitted pollutants, taking into account the avoided emissions due to the realisation of a district heating system, to the increment of the electric energy production and to the reduction of the MSW landfilling in this way, the best localities correspond to the sites where a substantial increment of the district heating is possible. However, even if the district heating system wasn’t increased by the incineration, the environmental balance would be largely positive.

Definition of PM10 emission factors from traffic: use of tracers and definition of background concentration

Within air quality management, one of the most important emission factors that should be known is PM10 (exhaust and non-exhaust flows) coming from traffic. The existing data and models produce very variable emission factors, also according to climate, sanding conditions, road material; thereby, a more general approach, based on the use of traffic tracer such as CO and NOx, can be put into practice in order to have a reliable assessment of PM emissions. Within the tracer approach, the definition of the background concentration of pollutants is of prime importance but representative measurements could be not at disposal. The present work is an attempt to define background concentration by considering the average concentration measured in an urban area during the night (0-5 am), when traffic and industrial instantaneous contribution are negligible and the heating plants are switched off. The so called “night method” has been tested and validated by means of the OSPM model, an atmospheric dispersion model studied for street canyons, for CO and NOx. In the case of CO, the results were surprisingly satisfactory and the method could be considered consistent, whereas NOx turned out to be not reliable as a tracer because of the chemical reactions that occur in the troposphere.

Methodological approach for the assessment of technological structure impact and risk

The environmental sustainability of technological plants, which is a fundamental requirement for territorial planning, needs the development of different widening moments. First, of all it is necessary to consider the plant as a potential source of pollutant emissions and to verify that the best technologies have been used to limit these fluxes, taking into account economic restraints. Second, the effect of the release on air quality modification should be established, with reference to air quality in particular, in order to be able to make suitable comparisons with recognized standards. Finally, it is necessary to evaluate the pollutant dose that has an impact on the exposed subjects, and the risk that arises from this impact, taking into account both toxicological and epidemiological considerations. The description of this path, with reference to some real cases of substantial impact and public concern, can be considered a methodological outline for the required compatibility assessment.

Integrated pollution prevention and control: choosing the best available technique by using a cost benefit approach

European directive 96/61/CE concerning integrated pollution prevention and control was completely received in Italy at the beginning of 2005 by D.Lgs. 59/2005. The contents of the directive are now widely applied within the authorization procedure of many industrial activities in Italy, such as pulp and paper production, cement factories, foundries, chemical installations and so on. The hardest decision that competent authorities have to take within the procedure relates to the definition of the emission limit values; these limit values and the equivalent parameters and technical measures shall be based on the so-called “best available techniques (B.A.T.)”. The directive 96/61/CE, art. 9, says that the emission limit values should be decided “taking into account the technical characteristics of the installation concerned, its geographical location and the local environmental conditions. In all circumstances, the conditions of the permit shall contain provisions on the minimization of long-distance or transboundary pollution and ensure a high level of protection for the environment as a whole.” In the present paper we try to define the proper emission limit values for nitrogen oxides emitted by a cement factory in Italy by comparing the costs of the techniques applied to control emissions with the environmental benefit arising from the reduction of the emissions. The assessment of the external costs associated to the impact of pollutants deriving from cement production has been carried out by using the ExternE approach, a research program of the European Commission based on atmospheric dispersion modelling, exposure-response functions and monetary valuations. On the other hand, the costs of the abatement technologies are assessed on the basis of the investment and operating costs reported for the cement industry.