In conjunction with the Catholic University of the Sacred Heart - Brescia and the CRASL - the Lombardy Research Centre for the Environment and Sustainable Growth, in the period between September and November 2010, A2A conducted a socio-environmental survey on the introduction of the district heating service in the Lomellina-Canavese quarter of the city of Milan.

As far as the environmental part was concerned, the avoided emissions of NOX, SO2, PM10 and CO2 were calculated in various scenarios for the extension of the district heating service and the related exposure of the population of Milan to the pollutants. On social acceptability and stakeholder involvement, on the other hand, the research made it possible to collect data/elements on inhabitant acceptability levels with respect to the district heating service.

Amsa has developed a system for managing and controlling process parameters called CCC (Combustion Charge Control) which is capable of automating combustion in grate waste to energy
plants, optimising the working of the plant.

This system, which Amsa has begun to market, has already been implemented on both combustion lines of the ACSM-AGAM waste to energy plant in Como. Amsa has initiated the procedures required to obtain an industrial invention patent (covering Italy) for Combustion Charge Control.

The objective of this project is to identify measures to soundproof the rear part of the double chamber compressors used in the city of Milan to collect glass and paper and assess these by testing.

Between 2011 and 2012 36 vehicles will be equipped with a rear cap soundproofing system developed by Amsa which consists in the installation of sound absorption panels inside and outside the equipment and a hydraulic system aimed at slowing down the speed at which the glass falls into the collecting bin.

The sound absorption material has a composite and stratified nature, while the intervention on the equipment envisages the presence of a flap positioned on the mouth from which the glass falls, activated by a hydraulic cylinder which remains in a closed position when the bin is emptied and subsequently assumes an open position. This interruption to the fall and the panel soundproofing have enabled a reduction of up to 12 decibels to be achieved at the rear part of the vehicle and at a distance of six metres when the glass is being collected, which in terms of noise peaks, measured in pascals, means a decrease from 40 to 10 Pa.

The results obtained from the experiments to lower nitrous oxide (NOx) emissions performed at the A2A waste to energy plant in Brescia are highly interesting and extremely promising.

The plant is equipped with three independent combustion lines, two of which have been in service since 1998 and are fired by urban solid waste, while the third, which has been in service since 2004, is fired by waste consisting of biomasses. All of these are equipped with systems for recycling combustion gases and non-catalytic systems for reducing nitrogen oxides (SNCR) that enable the concentration of NOx to be restricted to emissions that are well below the European ceiling of 200mg/Nm³. To reduce the emissions of NOx and the leaks of the ammonia used in the process even further a catalyst must be installed that can facilitate the reaction between ammonia, oxygen and the nitrogen oxides, although this will require the gas to be heated again with the consequent reduction in the energy efficiency of the plant and an increase in the complexity of the installations. For this reason a new experimental system (High- Dust SCR) has been installed on one of the three combustion lines of the waste to energy plant, with the catalyst being installed inside the boiler in the fume path, meaning at a position where the temperature of the gas is still quite high (270°C).

This is the first case in the world where a system of this kind has been installed on this scale. This initiative forms part of a European research project called NextGenBioWaste (Innovative Demonstration for the Next Generation of Biomass and Waste combustion plants for energy recovery and renewable electricity production).

The first catalyst entered service on line 2 in March 2006, while a new catalyst, with a new blend of materials having greater resistance to usage, was then installed at the end of 2008.

Another catalyst was installed on line 3 in September 2009 and work began in March 2010 for installation on line 1.

The emissions comply with the project values NOx<70mg/Nm³ and NH3<5mg/Nm³, with a reduction of approximately 20% in the consumption of ammoniac solution compared to the previous SNCR system.

The reduction in emissions can be achieved without the loss of electric yield and the consumption of methane (or steam) and equipment for the post-heating of the fumes are avoided.

AMSA S.p.A. has been working since 2008 with the Joint Research Centre of the European Commission (JRC) which has its head office in Ispra (Varese).

The activities to which the agreement between the two relates regard the experimental testing of the emissions of AMSA S.p.A. vehicles and in particular a comparison between the emissions of a vehicle running on 25% biodiesel and a vehicle running on methane.

 Testing is carried out by using two 23m³compressors on which the JRC portable equipment is installed.

The equipment records the atmospheric emissions of the two vehicles during normal waste collection activities in the city of Milan. AMSA is the first company to have performed tests of this nature.

The results show that the use of methane enables a considerable reduction in particles (-75%) and NOx (- 86%) in the atmosphere to be achieved.

Research study into the emission of fine and ultrafine dust by combustion plants

A2A contributed to the study commissioned by the Federambiente association at the LEAP laboratory (LEAP is a consortium organised and supported by the Milan Polytechnic) on the subject of the emission of fine and ultrafine dust by combustion plants.

This study, which began in 2007, required almost two years of work and was organised in two separate stages: the first stage consisted of a critical analysis of the literature and the background knowledge concerning the phenomenology of the formation of fine and ultrafine dust (PU), the features of the sources and the potential effects on human health; the second stage consisted of experimental testing to identify and quantify emissions of fine and ultrafine dust by combustion processes in fixed plants, with specific emphasis being given to waste to energy plants. The results obtained were highly interesting and are summarised in the following graphs.

The figures show that the concentration of ultrafine dust in emissions from waste to energy plants constructed with the best available technology (such as for example those of A2A in Milan and Brescia) is lower than that found in the surrounding air and considerably lower than that found in emissions deriving from the combustion of pellets and diesel in traditional heating boilers.

In 2009 AMSA completed a feasibility study on the use of an innovative process for the recovery of the heavy ash (slag) produced at the Silla 2 waste to energy plant on the outskirts of Milan.

By cold-working and wet-working the inert portion of the slag (which amounts to around 80% by weight of the total) a product is obtained that can be used to replace cement in the production of concrete (up to 20% to 30%). The mechanical resistance characteristics of the concrete obtained in this way are no different from those that may be obtained with cement alone, and they improve the chemical resistance and life of the items over time as the product has features that resemble natural pozzolanic ash.

 
Constructing the plant will make it possible to avoid disposing of around 80,000 tonnes/year of slag, thereby eliminating disposal costs. All of the product (approximately 65,000 tonnes/year) will be sold for use in the building sector, thus enabling savings of approximately 72,000 MWh/year to be made, excluding the energy required for production, and emissions of CO2 of approximately 50,000 tonnes/year to be avoided.

 The activities planned as part of the Basic Research and Industrial Research projects continued in 2009 in Ecodeco; both of these had already been approved and admitted for subsidy by the Ministry of Education, Universities and Research.

The Basic Research Project regards the definition of the base components and the maximum objectives that may theoretically be achieved by the system model for enhancing the value of the Secondary Basins, while the Industrial Research Project, described below, is separated into two main sections - Waste & Power and Natural Energy from Waste - with work that has generated encouraging results.

In the Waste & Power section:

• in order to neutralise the acidity of the fumes in the combustion chamber, various types of reagents were tested to reduce the acidic compounds and it was seen that some of these enable the exchange surfaces of the boiler to remain efficient and the chemical composition of the deposits to be changed so that they may be more easily removed; this too was tested using cleaning systems (water, ultrasonic and beating) and has given good results (even though these are being taken to a maximum);
• tests have been performed that have enabled the formation of nitrogen oxides to be reduced by controlling the firing better, while tests for optimising the NOx heat treatment systems have also been carried out;
• as a means of reducing thin dust, materials have been identified that enable reduction effectiveness to be improved even further when compared to traditional sleeve filtration systems.

In the Natural Energy from Waste (NEW) section work has continued on improving processes for the activation and exploitation of biogas. For the former a pilot bioreactor has been constructed on which testing has been carried out to identify the best process conditions; for the latter, work has been concentrated on obtaining an optimal usage of biogas in engines, in terms of efficiency and emission reduction.

The aim of the system is to check in real time that the geomembrane is still in one piece, both during the filling and management stage and the post-closure stage.

The plastic geomembranes commonly used to make landfills hydraulically impermeable are also excellent electrical insulators. If an electric current is able to pass between the underlying ground and the material on
top of the geomembrane then the membrane must be torn.

The permanent geoelectric monitoring system patented by Ecodeco consists of energising the ground underneath the land fill by means of a low ampage continuous current generator and measuring any current flows by using a series of surface electrodes placed above the plastic membrane. Through the use of specific software it is possible to visualise immediately, both in table form and by means of a three dimensional graph, the distribution of the measured current and locate the existence of any tears in the geomembrane precisely.

The permanent geoelectric monitoring system is currently installed and used in the majority of the landfills of companies of the Ecodeco Group (such as for example at the Fertilvita di Corteolona (Pavia) and Sicura di
Comacchio (Ferrara) landfills) and is currently being recommended or intalled by Ecodeco for plants outside the Group (such as for example the special urban waste landfill at Cava dei Modicani - Ragusa).

This plant built in Brescia can deal with approximately 30,000 tonnes of waste on entry a year and is the second largest plant built in Italy with such characteristics.

The innovative and highly qualifying features of the plant, which was designed following a whole series of experimental tests, are as follows:

• a counter-current waste washing unit;
• a cyclonatural unit with spiral separators;
• a chemical, physical and biological treatment plant for the recovery of water in the washing process.

The washing process enables substances present in a dissolved form, in emulsion or in suspension to be transferred from the waste particles into the water. Following this the solid contaminating substance particles are separated by means of further selection processes.
 

Finally the water used in the process is purified in a specific chemical, physical and biological treatment plant.

This innovative plant enables street cleaning waste to be treated and materials of certified quality to be obtained which previously were sent to landfills for disposal. As a consequence, on the one hand the plant limits the use of landfills while on the other it restricts the need to obtain sand and gravel from new quarries.

The products leaving the plant conform to the UNI EN standards for the specific sector: UNI EN 12620 - Aggregates for concrete; UNI EN 13043 - Aggregates for bituminous mixtures; UNI EN 13139 - Aggregates for mortar; UNI EN 13242 - Aggregates for civil engineering work.

The materials recoverable from the treatment of arriving waste are therefore materials which may be sold throughout the European Union as they bear the EC marking. The aim of the EC marking is to provide a guarantee to the consumer, namely the purchaser, that the marked products meet basic safety requirements and have passed the tests envisaged by the regulations.

As part of the “NextGenBioWaste” European project a feasibility study has been performed in collaboration with specialised companies and Trieste University whose objective is to draft the outlines of a heavy ash recovery plant. This study also took into consideration the experience in recovery gained at the Brescia waste to energy plant.

This recovery plant, for which authorisation was applied for at the end of 2007, will consist of the following sections:

Ash storage and ageing - During the ageing process, which from the tests carried out has an optimal duration of 30 days, the heavy ash is transferred from one storage bath to another and wetted by means of carbon dioxide saturated rainwater to encourage chemical and physical carbonisation processes which promote the precipitation of certain heavy metals. At the end of the 30 days the aged ash is transferred to the treatment sections.

First washing stage - The first stage envisages comminution, washing, granulometric selection and theseparation of metals, by means of chopping, crushing and wet classification processes; in addition, the firstwashing stage also includes a section involving the clarification and treatment of the water, which is fully ,recycled back to the top of the plant. The first washing stage enables washed ferrous and non-ferrous
materials to be recovered together with inert materials (around 20% compared to the ash on arrival) and dehydrated sludge.

Second washing stage - The second washing stage consists of the clarification and treatment of the recycling water and a chemical and physical treatment section for the final filtration of the excess water to make it suitable for discharging into the public sewage system. This stage enables high quality inert materials (around 20% compared to the ash on arrival) to be recovered, in accordance with the release test as per the Ministerial Decree of 5 February 1998, together with dehydrated sludge.

The plant will be divided into two equal parallel lines, each being independent and having a maximum treatment power of 35 t/h, and will have a total power of 215,000 t/y.

The plant will enable over 95% of the waste arriving (which currently ends up being disposed of in landfills) to be recovered; in particular merceological analyses and experimental tests show that it will be possible to recover the following secondary raw materials:

• metawashed ferrous metals (approximately 18%, equal to around 46,000 t/y);
• washed non-ferrous metals - aluminium, copper, etc. (approximately 2%, equal to around 5,000 t/y);
• first stage inert materials [ > 4 mm] (approximately 21%, equal to around 52,375 t/y) conforming to standards UNI EN 12620 (aggregates for concrete) and UNI EN 13043 (aggregates for bituminous mixtures);
• second stage inert materials [ ≤ 4 mm] (approximately 40%, equal to around 100,700 t/y) conforming to the release test as per the Ministerial Decree of 5 February 1998 and to the standards UNI EN 12620 (aggregates for concrete), UNI EN 13043 (aggregates for bituminous mixtures), UNI EN 13139 (aggregates for mortar) and UNI EN 13242 (aggregates for civil engineering work);
• first stage (approximately 11%, equal to around 26,750 t/y) and second stage (approximately 7%, equal to around 18,500 t/y) dehydrated sludge, inert materials consisting of oxides, hydroxides, silicates, and carbonates, which represent the more “cement-like” part of the heavy ash by reason of their physical features and chemical composition: these can be re-used as a secondary raw material in the conglomerate, brick and cement industries.

The membranes (ZeeWeed 500c) installed in the new line “B” of the Verziano purifier are of the fluctuating hollow fibre type and represent a completely innovative technology in the sphere of civil waste water treatment: the hollow fibre is well known to be the most favourable geometrical form for limiting the investment and management costs of a membrane process given its contained production expenses, high filter area density per unit of volume and low energy consumption.

It has never been possible, though, to use hollow fibre membranes for liquids having a high content of suspended solids due to the fact that the fibres get clogged up in a very short time. This problem has been resolved for applications with the new hollow fibre modules because the solids remain outside the membrane and only the permeate runs inside the fibre, thereby reducing the risk of clogging. The membrane cosists of a macroporous support polymer, externally lined with another polymer which acts as a filtering element.

Porosity is in the ultrafiltration range (0.035μm nominal - 0.10μm absolute). To control fouling, the filtration modules are equipped with an air insufflation system which ensures, by means of increased turbulence closeto the fibres, that the deposits of biomass on the fibres are kept to a minimum. An ultrfiltration module consists of thousands of fibres; should these break, the internal diameter is so small that it ensures that the broken fibre is clogged in a matter of seconds. In the event of breakages this feature ensures that the quality of the effluent is not compromised by the presence of suspended solids.

The water filtered in this way contains a negligible quantity of suspended solids (less than 1 mg/l) and is even practically sterile.

Over the past few years European Union policy regarding the protection of the environment and natural resources has concentrated on the problem of waste and in particular on the increasing quantities of waste being produced. The reduction of waste has been identified as the priority, followed by the re-use and recovery of materials and energy. The landfill is identified as a last resort, to be used in the case that it is not possible to find any other solution.

As part of this overall framework an Aprica working group completed a study in July 2007 which had been developed in the following three stages:

• An overview and analysis of good practice in relation to intervention taken in Europe and North America. The work performed identified the paper and food sectors as being necessary and deserving of particular attention (performed by IEFE Bocconi).
• A study of the best prevention initiatives which relate to the city of Brescia and an assessment of the sociological and cultural impact of the measures and interventions identified within the paper and food sectors; special attention was given to the IPPC regulations, with the identification of BATs, and to the Green Public Procurement (performed by IEFE Bocconi).
• An analysis of the current situation in the production of waste and of a future situation which envisages the reduction of this waste; for both these scenarios the study concentrated on the decisions and the behaviour of the various players (service producers, economic operators, users, etc.) and on the measures required for change, with the aim of identifying a series of practical steps that should be taken to stabilise the production of waste, thereby counter-balancing the present increasing trend (performed by INDACO, the Department of Industrial Design, the Arts, Communication and Fashion – Milan Polytechnic).
• A qualitative and merceological analysis of the flows of waste produced in the urban environment in Brescia, for the two sectors previously highlighted (performed by the CRASL - the Catholoic University of the Sacred Heart of Brescia).
• An analysis of the best practice to adopt at various institutional levels (performed by Ambiente Italia).

The above-mentioned studies enabled practical proposals to be drawn up aimed at obtaining a reversal of the trend in the production of waste, namely at stabilising the production of waste throughout the territory of the city of Brescia by means of carrying out 11 steps which, using a wide variety of tools (communication, incentives, voluntary agreements, etc.), will firstly slow down the increase and then stabilise the production of waste. To this end, in addition to steps being taken in the two sectors under consideration (paper and food) additional measures are also planned which regard composting, dealing with bulky waste and re-usable nappies for babies. Various areas of interventions and flows are envisaged.

The Region of Lombardy has recognised the validity of this project and with a resolution of the regional council, DGR VIII 5645 of 23 October 2007, took the decision to co-finance the continuation of the study with the aim of putting forward the above-mentioned steps as good practice recommended by the Lombardy Municipalities for combating and stabilising the increasing trend in the production of urban waste. In agreement with the region’s technicians in 2008 the working group reworked the scope of application of the measures, extending them to outside Brescia’s municipal borders.