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Atmospheric emissions generated by waste-to-energy plants

Every Hera Group waste-to-energy plant is equipped with fume purification and process and emission control systems, designed and produced in order to attain:

  • elevated fume purification performances in all process conditions;
  • elevated management versatility;
  • elevated reliability of emission control systems.

In order to meet these goals, new plants and plants undergoing renovation are equipped with the following systems:

  • double reaction and filtration system to lower the concentrations of particulates, hydrochloric acid, hydrofluoric acid, sulphurous dioxide, heavy metals, dioxins and furans and aromatic polycyclic hydrocarbons (the Modena plant has a bag filter and an electrostatic precipitator);
  • double reaction system (catalytic and non-catalytic) to reduce concentrations of nitric oxides;
  • double fume monitoring system for process control (SMP): the two systems measure the concentrations of the main pollutants emanating from the oven and downstream of the first reaction and filtration phase, on the basis of which a calculation is made of the volume of reactants required to ensure purification levels that guarantee respect for legal emission limits and which are, on average, 80-90% inferior to these;
  • continuous double monitoring system for chimney emissions: one as a reserve for the other in order to guarantee the continuity of the analysis of concentrations in atmospheric emissions.

The possibility of using double purification and monitoring systems in series (in parallel as regards chimney monitoring) allows the above objectives to be successfully pursued.
In addition to the aforementioned activities, as regards the monitoring of emissions and environmental impact, the following operations are carried out on an annual basis:

  • timely controls of the chimneys, at a frequency fixed by the Integrated Environmental Authorisation, for those parameters which cannot be continuously monitored, resorting to certified workshops;
  • controls on soil fallout of the pollutants: through external monitoring programmes in collaboration with the University and research agencies, deposition analyses are performed on soil, ground and vegetation etc., in order to ascertain that the emissions, in addition to being within the legally established limits, does not have any significant impact on the surrounding environment.

Verification of Ferrara waste-to-energy plant emissions

As established by the Integrated Environmental Authorisation for the Ferrara waste-to-energy plant, Hera is enacting, with the scientific coordination of the CNR of Rome, the environmental and health monitoring protocol defined by Arpa, Ausl and the Province of Ferrara.
The studies on soils, mutagenesis and air quality were transmitted to the relevant bodies and examined at a technical table promoted by Hera in January 2012: the meeting was attended by the Province, Arpa, Ausl, CNR and Università La Sapienza.
The studies on mutagenesis did not highlight significant differences between the mutagenicity induced in the location close to the plant and that of the town property. In the soil a slight correlation between the concentration of micropollutants and the distance from the emitting source was discovered, albeit with minimal concentrations, far below the limits indicated in the laws in force. The correlation between the concentration of metals and the distance from the plant chimney has not been verified: the presence of metals in the earth therefore seems to be related to the structure of the soil, which is typical of the natural make-up of the river sediments of the Po.
From the reports on the monitoring of air quality it emerges that the concentrations of pollutants are consistent with those expected for a sub-urban type area in a climatically unfavourable zone such as the Po Valley where there is typically poor atmospheric mixing, a phenomenon that tends to make the pollutants emitted uniform in terms of space.

Atmospheric emissions generated by waste-to-energy plants
Hydrochloric acid3.62.93.5
Nitric oxides413.8310.7283.7
Sulphur oxides5.03.04.1
Carbon monoxide57.053.252.1
Hydrofluoric acid0.20.10.2
Total Organic Carbon7.06.14.1
Waste treated in plants (t)734,492800,576819,341
Net electricity produced (MWh)405,714436,863466,294
Thermal energy produced (MWh)70,44688,755118,345

The data are calculated using continuous measurement systems which are subject to the approval of the supervisory bodies at the moment of authorisation for operation of the plant. The procedures used by the single plant systems for collecting and calculating the volume of substances emitted are not completely standardised.

The analysis of mass flows shows the substantial stability of the quantities of pollutants emitted by Hera Group waste-to-energy plants. One apparent exception is the Modena plant where there was an increase in the quantities of pollutants emitted into the atmosphere which, in reality, is not determined by a downturn in the performance of the fume purification system but rather the increase in the hours of functioning as a result of the greater regularity acquired by the new line 4 and therefore the amount of waste treated. For almost all of the plants there was an increase in the amount of electricity produced and sold to the national grid. For Bologna, Ferrara and Forlì, in 2011 the plants connected to the district heating network recorded an increase in the amount of thermal energy produced.
In the three years under consideration, there has been a continuing downward trend in total emissions of hydrochloric acid (-4%), sulphur oxides (-19%), nitric oxides (-31%) and Total Organic Carbon (-42%), and this despite the 12% increase in treated waste. For hydrofluoric acid the increase (+9%) is exclusively linked with the increase in treated waste. For the particulates, the worsening was partly due to the particle abatement system in the new line of the Modena plant (very high yields and a system foreseen by the BAT, the Best Available Techniques at European level) and partly down to the increase in waste treated there: average concentrations recorded in 2011 were 72% below the legal limits. In addition, in 2011 there were problems with a particulate measuring instrument at the Ravenna plant, resolved with major maintenance work.
With regard to pollutants not monitored continuously, total emissions can be estimated on the basis of the results of analysis performed during the year. Compared to 2009, in 2011 there was a 69% reduction in dioxins, a 59% reduction in aromatic polycyclic hydrocarbons and a 21% reduction in metals. In 2011, 121 kilograms of metals (155 in 2009) were emitted, along with 0.1 kilograms of aromatic polycyclic hydrocarbons (0.3 in 2009) and 16.3 milligrams of dioxins and furans (52.1 in 2009).

Atmospheric emissions generated by waste-to-energy plants in relation to disposed waste
Particulates 4.5 5.97.1
Hydrochloric acid 4.9 3.64.2
Nitric oxides 563 388346
Sulphur oxides 6.8 3.75.0
Carbon monoxide 77.6 66.563.6
Hydrofluoric acid 0.3 0.10.2
Total Organic Carbon 9.5 7.74.9

The data are calculated using continuous measurement systems which are subject to the approval of the supervisory bodies at the moment of authorisation for operation of the plant. The procedures used by the single plant systems for collecting and calculating the volume of substances emitted are not completely standardised.

Comparing quantities of substances emitted into the atmosphere with quantities of disposed waste results in specific emissions for various pollutants. This indicator measures the efficiency of the exhaust abatement systems used in the plants, and highlights the technical improvements obtained with the new plants. For some pollutants (sulphur oxides and total organic carbon), there has been a definite improvement.
On average, for the pollutants indicated in the table, the reduction compared with 2009 is 13%: The figures go from a -3% for hydrofluoric acid to a -39% for sulphur oxides. The particulate emission trend is influenced by the phenomena previously illustrated for the Modena and Ravenna plants.

Concentrations of atmospheric emissions from waste-to-energy plants (2011)
mg/Nm3Legal limits
Leg. Decree 133/2005
(lines 1 and 2)
(lines 2 and 3)
(line 3)
(line 4)
(special waste integrated platform)
(line 4)
Hydrochloric acid100.
Nitric oxides20089.444.635.954.6132.768.022.8
Sulphur oxides501.
Carbon monoxide5013.
Hydrofluoric acid10.
Total Organic Carbon
Total metals 0.50,0670,0060.0030,0070.0030.0020.005
Aromatic polycyclic hydrocarbons0.010.000020.000030.000010.000050.000010.000010.00002
Dioxins and furans (ngFTE/Nm3)0.10.002210.001540.002010.006960.016300.002470.00222
Cadmium and Thallium0.050.001700.000350.000530.000390.000380.000270.00039

The legal limits refer to Legislative Decree no. 133/2005. For particulates, hydrochloric acid, nitric oxides, sulphur oxides, carbon monoxide, hydrofluoric acid, and total organic carbon, the values correspond to the average values measured in continuation and the limits correspond to daily averages. For all other components, the values correspond to the average of periodic measurements and limits refer to each individual measurement. In the new lines at Ferrara, Forlì, Rimini and Modena mercury levels are continuously measured.

The results of the emission measurements at the Hera Group waste-to-energy plants confirm that, being equipped with the best technologies available and run in the most efficient manner, these plant emit far lower levels of particulates, dioxins and furans, IPA and metals than permitted by emission limits. For dioxins and furans, the values recorded show that the concentrations emitted are a few hundredths of the regulatory limit. For the IPA the concentrations are just a few thousandths of the permitted limit. The measurements made to identify the metals shows concentrations well below the limits. Compared with the other parameters, subject to continuous monitoring, at plants equipped with the sulphur oxide catalytic abatement system (Bologna, Ferrara, Forlì, Modena and Rimini) the concentrations were not only well below the legal limits, but also the limits established by local authorities, which are much more stringent than national regulations. There was a general improvement in the performance of the Modena and Rimini plants, opened more recently, where in 2011 there was a clear improvement in the combustion and fume purification processes.

Compliance of atmospheric waste-to-energy emissions with legally established limits in Leg. Decree 133/2005 – continuously monitored parameters (optimal values  100%), average of the seven plants

The plant renovation process has resulted in a significant improvement in the abatement percentages of pollutant emissions: in January 2008 the two new waste-to-energy plant lines in Ferrara became fully operational, since early 2009 the new Forlì plant has been operational, in April 2010 the new line 4 of the Modena waste-to-energy plant became operational, and since October 2010 the new line 4 of the Rimini waste-to-energy plant has been operational. The chart above shows the trend in the parameters continuously monitored for the period 2004-2011. In 2011, the concentrations of the atmospheric emissions of waste-to-energy plants were, on average, 12% of the limit set by the law, compared to 26% in 2004. This means that in 2011, emissions were 88% lower than the allowed level while in 2004 this percentage was 74%.

Operation transparency for the Hera Group waste-to-energy plants

There has been no stop to Hera's initiatives to guarantee citizens maximum transparency and accessibility to their waste-to-energy plants.
As already described in the chapter on the local community, since January 2011 the web channel dedicated to the waste-to-energy plants has included a calendar showing when guided tours of the plants are available and offering the chance to make bookings online. Special visitor routes are being completed which, through explanatory signs at the heart of the plants, illustrate how the various sections operate and enable even those without technical knowledge to understand how the plant works and how our operators manage their equipment. By the end of 2011 there were active visitor routes at the Bologna, Ferrara, Forlì and Modena plants: in 2012 a visitor route in Rimini will be constructed.
In 2011, 150 visits to the Group's waste-to-energy plants were made available online: the requests received were managed into 120 visits, 31 of which for school pupils and university students, for a total of almost 2,000 people.
In association with the local council and Circoscrizione 2, since the end of 2009 an information desk has been available at the Modena plant, upon appointment, every Tuesday afternoon from 4 pm to 7 pm. By heading to this desk, citizens can request and obtain information on the functioning of the waste-to-energy plant directly from technicians that work there every day. To book an appointment at the info desk all you need do is phone or send an email to the URP of Circoscrizione 2.
Furthermore, since 2006 a 'Comitato Consultivo della Comunità Locale' (Residential Advisory Board - RAB), comprising of citizens that live near the plant, has been active, meeting periodically with Hera representatives to gather information on the environmental impact of the waste-to-energy plant.

Compliance of atmospheric waste-to-energy emissions with legally established limits in Legislative Decree no. 133/2005 – continuously monitored parameters (optimal values  100%), details per plant

Significant improvements in the results were obtained with the completion of new plants: in fact, the Ferrara and Forlì plants, started up in 2008, and the Rimini plant in October 2011 following the definitive shutdown of the old lines, recorded the best results. In the case of Modena the improvement is less evident mainly because of the different system for monitoring particulates. With the improvement of combustion, at this plant in 2011 there were improvements in nitric oxide and carbon monoxide emissions while other pollutants were contained with the improvement of the doses of reagents achieved following various analyses and experimentation with new types of activated carbon in order to find the best mixture for this type of plant.

Atmospheric emissions from waste-to-energy treatment plants compared to authorisation limits - continuously monitored parameters (optimal values < 100%)
Bologna (FEA) waste-to-energy plant18.7%22.0%19.5%
Ferrara waste-to-energy plant9.6%8.2%8.4%
Forlì waste-to-energy plant16.2%19.9%16.4%
Modena waste-to-energy plant24.3%17.8%17.7%
Ravenna waste-to-energy plant (special waste)10.9%10.9%10.0%
Arithmetical average16.0%15.8%14.4%

The Integrated Environmental Authorisations relating to the plants in Ferrara, Forlì, Rimini and Modena also provide for the continuous monitoring of mercury.

The same indicator was calculated for the five plants with authorisation limits that are more stringent than Italian regulations for 2011 (for the eight parameters monitored in continuation on average the limits established by the authorisations correspond to 77% of the limits laid down in Legislative Decree no. 133/2005); the data is displayed in the table above. The results are also excellent in this case: the concentrations are, on average, around 85% lower than the most restrictive limits. It is notable that the limits established by the individual authorisations are different depending on the plant, meaning that it is not possible to compare the performances of the single plants.
As such, the Hera Group plants continued to perform to an excellent level also in 2011. The Integrated Environmental Authorisations issued by the provinces authorise the functioning of the plants, imposing significant restrictions compared with the limits established by national legislation. From the reported figures it is clear that, overall, the status of emissions of all group plants is highly positive.

Relative to the parameters for which Legislative Decree 133/2005 does not require continual monitoring (total metals, aromatic polycyclic hydrocarbons, dioxins and furans, cadmium and thallium, and mercury), on all incinerators managed the Hera Group has carried out a total of 547 samples, in full compliance with the individual plant authorisations, a considerably higher number than the 105 provided for in national regulations, the 335 established by the IEA and the 432 carried out in 2010.
In 2011, as in previous years, Hera plants complied with the authorisation limits relative to amounts of waste treated, their type and, where present, their derivation. As regards the Modena plant, in 2011 the quantitative limit of special waste rose from 45,000 metric tons to 50,400 metric tons (until the new line 3 became operational).

Plant thermal power saturation percentage
Bologna (FEA) waste-to-energy plant100%
Ferrara waste-to-energy plant83%
Forlì waste-to-energy plant78%
Modena waste-to-energy plant94%
Ravenna waste-to-energy plant100%
Rimini waste-to-energy plant100%
Average 93%

Given that in 2011 the Hera Group waste-to-energy plants treated quantities of waste substantially in line with the authorised quantities, and given the calorific value of this waste, the saturation percentage of the thermal power was equal to 93%. This means that in 2011 the plants were used to 93% of their potential.

At the waste-to-energy plants methane is used in the start-up and shutdown phases and to support combustion if the calorific value of the treated waste is low: overall consumption in 2011 came to around 9 million m3. Containing methane consumption is one of the improvement goals of the Group's plants, a goal to pursue by reducing the number of unscheduled shutdowns and improving combustion processes through the standardisation of waste sent for treatment and the improvement of processes to regulate combustion air.

From the remote control of waste-to-energy plants to the plant supervision system

Since 2007, a station to supervise Hera's waste-to-energy treatment plants has been operating in Coriano (Ravenna); this is an eminent national innovation that transmits all operating information deriving from the various plants.
Since 2009 an innovative system for organising and using technical and managerial data has been developed. The system, created as a support tool for the operational management of the waste-to-energy plants, is now also operational at the plants of the "Landfill Supply Chain", making the main operational and management data available to Group technical and administrative staff. Through this system it is possible to guarantee the uniform and standardised management of the various treatment plants, enable the spread of managerial best practices in terms of energy production, optimising the treatment process and reducing environmental impact.
For the waste-to-energy plants the system acquires the main operating data in the field, puts them in historical order and makes them available to Herambiente technical staff using special tools, enabling the detailed technical analysis of the functioning of the plants, the real time monitoring of the various parts of the plant and the prevention of malfunctions and breakages.