Cement plants have higher emission limits than incinerators

Cement plants have higher emission limits than incinerators

The processes that take place inside the cement plant and a waste-to-energy plant are different, even when a cement plant operates in cofiring mode, using alternative fuels instead of fossil fuels.

For these reasons, the regulations set different emissions limits for certain parameters linked to the high combustion temperatures (e.g. NOx) reached in cement kilns, which are decidedly higher than those found in waste-to-energy plants, and to the nature of the raw materials used (e.g. COT and SO2). Other sectors, like glass, have higher limits than cement plants because of the even higher processing temperatures.

It is therefore the process and the technology available to reduce emissions that have an influence on the determination of the limit. Where there are known and established techniques for reducing emissions, the limits are progressively adjusted. To minimize impacts, it is essential that the emission limits established by law for each production sector comply with the Best Available Techniques for their containment.

As far as organic micropollutants and metals are concerned, the concentrated emission limits are identical for both a cement plant and a waste-to-energy plant.

More specifically, with regard to organic micropollutants, cement plants that co-incinerate apply by law the values referred to in paragraph 2 of point A of Annex 2 to Title III-bis of Part Four of Italian Legislative Decree no. 152/2006, which are exactly the same as those imposed on incineration plants pursuant to point A of Annex 1 to Title III-bis of Part Four of Italian Legislative Decree no. 152/2006. It is precisely paragraph 1 of point A of Annex 2 to Title III-bis of Part Four of Italian Legislative Decree no. 152/2006 that specifies for co-incinerating plants that "the total emission limit values (C) for the pollutants referred to in Annex 1, paragraph A, points 3 and 4 [for incineration plants, editor's note] shall be those set out in those points [metals, PCDD/F, IPA and PCB-DL, editor's note]".

In addition to all this, it should be remembered that any amount of waste removed from the waste-to-energy plant and used in cement kilns generates a net savings of emissions for the environment, emissions that would be generated by the cement plant all the same if production was carried out using fossil fuels.

Cement production using natural gas is cleaner than production using other types of fuel

False. Fuel as such is sometimes confused with the effects of its use in the production process.

Since fuels have a different chemical composition, and in particular have a different carbon/hydrogen ratio (C/H), the kinetics that is triggered in the kiln and the different flame temperatures – depending on the different fuels – generate process oscillations that can be compensated through proper management of the production process (including the use of acid gas abatement systems like SNCR or SCR), with the result that the emissions of the main pollutants generated using different fuels are comparable.

It is therefore the correct management of the production process – and not so much the nature of the fuel – that determines the emissions profile of the cement kiln.

The use of natural gas, where available, brings only benefits in terms of lower CO2 emissions, remembering however that more than 60% of CO2 emissions comes from the decarbonation of the raw material and not from the combustion, and that it is not a polluting gas, but at most a climate-altering gas.

The monitoring units detect the fumes emitted by the cement plant

Partly true.

It depends on where they are located and what other man-made sources are present in the area.

It is important to remember that most of the emissions of NOx, PM10 and PM2.5 are not caused by a single plant, but mainly from third-party sources like vehicle traffic, civil heating and agriculture.

Like all emissions, a plant's emissions are dispersed due to orography, winds and atmospheric conditions that can result in concentrations on the ground – even at the points of maximum fallout – that are as much as 200,000 times lower than the values measured at the stack.

Mathematical modelling is now able to represent the immission load of pollutants from a specific source in an extremely precise manner and to compare it with what was found by environmental monitoring networks installed and managed by bodies like ARPA or by municipalities.

The monitoring devices, even if positioned at the points of maximum fallout, will also detect all other fallout at human height from other sources of emissions in the area.

In the worst cases the weight of the pollutants produced by the cement plant and detected by the monitoring devices will account for just a few percentage points of the total.

The emissions measured won't be made public

False. The data recorded by our Italian plants are communicated to the control bodies (ARPA) using different methods agreed to with the bodies themselves, including an electronic real-time connection, the sending of data with established frequencies or the publication of dedicated web pages. The control bodies can also intervene at the plant at any time to carry out checks and investigations without prior notice, taking autonomous measurements and viewing and analyzing the data collected by the EMS (Emissions Monitoring System).

Moreover, in accordance with the provisions of the individual permits and/or agreements with relevant authorities, the daily average data of our emissions are published on the Internet and on the web pages of the municipalities.

Emissions in the cement plant's stack are a consequence of the fuel used

The fuel used in the cement production process is exclusively a calorie carrier that allows the activation of chemical reactions that transform the oxides which are present in the raw material into silicates. All this takes place in the rotary cement kiln, a chemical reactor where an intimate chemical mixing and exchange takes place between the incoming raw material and the fuel.

To achieve this, the quantity of fuel introduced into the production process is about 15-17 times less (by weight) than the raw material introduced into the same production cycle.

Consequently, the mass balances carried out regularly on the burning lines specify that the gases emitted to the chimney are mostly attributable to the composition of the raw materials, and only to a much lesser extent to the fuel.

Only a few pollutants are measured in the cement plant's stack

False. The technologies currently available allow continuous measurements to be taken for the following pollutants, which are typical of the cement plant production cycle: NOx (nitrogen oxides), SO2 (sulphur dioxides), HCl (hydrochloric acid), HF (hydrofluoric acid), CO (carbon monoxide), NH3 (ammonia), COT (total organic compounds) and dust. These readings can be made available electronically in real time for regional ARPAs.

For any other components that are not continuously measured, discontinuous checks and analyses are carried out through the prolonged sampling of dust and gases in the stack, making it possible to verify many other parameters typically associated with cement production (including organic and inorganic micropollutants, dioxins, furans, polychlorinated biphenyls and polycyclic aromatic hydrocarbons and metals).

The Emission Monitoring System (EMS) is periodically calibrated and checked by accredited third party laboratories, which certify its proper operation.

Exceedances of the limits are not known and are not reported

False. Given that exceedances of emission limit values occur very rarely, as a result of specific plant or production anomalies, thanks to automated mechanisms equipped with forecasting and control systems and to the continuous monitoring of the production process by operators, any exceedance is communicated to the competent authorities in accordance with the law and as prescribed in the IEA (Integrated Environmental Authorization) adopted by each plant in order to be able to operate.

Failure to notify would constitute an infringement that can be detected by the control bodies using data recorded by the Emissions Monitoring System (EMS) or analytical certificates prepared by accredited bodies.

The pollutants detected by the air quality monitoring units are generated by the fumes emitted by the cement plant

False. It is worth knowing that once emitted (so-called emissions), and depending on the hourly wind rates, the orography of the territory and other local factors, the gases and dust in the stack are subject to dispersion that can lead to concentrations up to 200,000 times lower than those emitted (so-called immissions), even at the points of greatest fallout. Subsequently, some of these gases and dusts, together with those from many other sources of man-made origin, may partially deposit on the ground (depositions).

Reliable mathematical models make it possible to quantify the contribution of specific sources, including the cement plant and all other activities in the area (traffic, heating, agriculture and industry). Models with precise mathematical simulations based on data from provincial or municipal emission registers allow comparing, overlapping and relating the effects of individual sources with respect to all human activities, in conclusion providing accurate information on the effects of a single source on the air quality in a given point.

The monitoring units in the area are the true sentinels, specifying whether the air in a given place complies with the provisions of the AQL (air quality levels) according to Italian Legislative Decree 155/2010. But even when the units are positioned at the plant's points of maximum fallout, studies based on the most recent models show that the cement plant's contribution accounts for only a few percentage points of the total.

Indeed, it is important to remember that most of the emissions of NOx, PM10 and PM2.5 are not caused by the cement plant, but come mainly from third-party sources like vehicle traffic, civil heating and agriculture. This has been demonstrated and quantified by in-depth studies carried out by research centres and control bodies like ARPA and ENEA.