Volatile Organic Compounds: meaning and definition

An organic compound is any compound containing at least the element carbon (C) and one or more among the elements hydrogen (H), oxygen (O), fluorine (F), chlorine (Cl), bromine (Br), iodine (I), sulfur (S), phosphorus (P), silicon (Si), or nitrogen (N), with the exception of both carbon oxides (e.g., CO2) and inorganic carbonates and bicarbonates.

A VOC – acronym for Volatile Organic Compound – is any organic compound that, at a 293,15 K temperature (i.e. 20°C), either has a 0,01 kPa pressure or higher or a corresponding volatility in particular conditions of use.

Both definitions have been retrieved from the legislative decree no. 152 of 2006 – “Environmental regulations”.

The volatile organic compounds category includes different chemical compounds which are able to interact in the troposphere to form polluting compounds. They include:

  • aliphatic hydrocarbons (e.g. butane, n-hexane) and aromatic hydrocarbons (e.g. benzene, toluene)
  • halogen derivatives (e.g. dichloromethane)
  • aldehydes (e.g. formaldehyde)
  • ketones (e.g. acetone)
  • alcohols (e.g. ethanol, butanol)
  • esters (e.g., ethyl acetate)
  • and other compounds (e.g., acetic acid, acrylamide, nicotine, ethanenitrile).

Volatile organic compounds of anthropogenic and biological origin

VOCs can be emitted into the external and internal environment.

Volatile Organic Compounds 1 - Brofind S.p.a.The major external sources of VOCs are both of anthropogenic and biogenic origin. Biogenic sources include some compounds released by plants, compounds from biological decomposition of organic matter, or methane from fermentation that may take place in manure heaps or landfills. External sources of anthropogenic origin are due to the exhaust emissions of vehicles, to solvent fumes for industrial use and, in a lesser form, to combustion fumes from thermal power plants.
The main indoor sources of VOCs are anthropogenic and come from cleaning products, building materials, furniture, cosmetics, deodorants, insecticides, heating devices, cigarette smoke, printers and copiers, glues, paints, adhesives, and various solvents.

Danger of Volatile Organic Compounds

It is good to remember that not all volatile organic compounds are dangerous for man: for example, methane or propane. Others, however, have even been classified by IARC (International Agency for Research on Cancer) as carcinogenic: these include formaldehyde and benzene.

Atmospheric concentrations

The table shows basic statistics regarding 24-hour average concentrations of a series of substances belonging to the VOC family, measured from January 2003 to June 2004 as part of an air quality monitoring project of the National Health Institute. The station was located in the municipality of Rome, in a semi-central area, at the edge of a wide road, with free circulation. It can be considered a “traffic-oriented” detection zone but without the direct presence of emission sources of industrial origin.

Among the monitored VOCs , particular attention was given to benzene, given the particular health interest of this pollutant due to its known carcinogenic characteristics.

VOC

average

*CV%

Min

Max

toluene

25,4

46,7

11,0

82,9

m-xylene

6,8

46,4

1,7

15,3

2-methylpentane

3,8

44,8

1,4

11,2

trimethylbenzenes

3,7

42,4

1,4

8,2

benzene

3,4

42,7

1,5

7,6

ethylbenzene

3,2

110,7

1,0

34,1

o-xylene

3,2

44,0

1,3

7,1

p-xylene

2,9

44,0

1,2

6,5

n-hexane

2,9

75,7

1,0

12,8

cyclohexane

1,5

90,8

0,4

8,2

tetrachloroethylene

1,4

47,4

0,4

3,2

n-heptane

1,4

38,1

0,5

2,9

methylcyclopentane

1,3

42,2

0,5

3,2

trichloroethylene

1,3

46,8

0,5

3,6

2-methylhexane

1,0

54,0

0,4

4,0

methylcyclohexane

0,9

53,4

0,4

3,0

VOCs: average values and basic statistics collected during the observation period (January 2003 – June 2004). Concentration measured in µg/m3 (milionth of a gram)
*CV% – coefficient of variation

VOC: what are the most important Italian and European regulations?

European Regulation Voc - Brofind S.p.a.In the last few decades attention towards air pollution has increased significantly and a lot has been done about emission control, reduction or elimination of pollutants and to define the maximum allowed concentrations for different categories of compounds.

Several regulations, both European and Italian, have been issued regarding the emission of VOCs. The most important are:

 

  • European Directive no. 42 of 2004 on the “limitation of emissions of volatile organic compounds due to the use of organic solvents in certain paints and varnishes and in certain vehicle refinishing products”, which was implemented in Italy by Legislative Decree no. 161 of 2006 and subsequent amendments.
  • Legislative Decree No. 152/2006 about “Environmental Regulations”, also known as the “Consolidated Environmental Act” or “Environmental Code”, establishes rules on soil and water protection, waste management, air pollution reduction, environmental impact assessment and compensation for environmental damage. The decree has undergone numerous amendments over the years, with the latest being introduced by Legislative Decree No. 21 of 2018. Part Five of the text deals with “regulations on air protection and reduction of emissions into the atmosphere”. Going into more detail, Title I legislates on “prevention and limitation of atmospheric emissions from plants and activities” by setting “emission values, prescriptions, sampling and emissions analysis methods, and criteria for the assessment of the compliance of measured values.” Article 275 deals specifically with VOC emissions.
  • Directive 2010/75/EU on “industrial emissions (integrated pollution prevention and control),” implemented by Italy through Legislative Decree No. 46/2014, establishes rules aimed at avoiding, or at least reducing, emissions from industrial activities into the air, water and land and the production of waste, in order to protect the environment;
  • The recent European Directive No. 2284 of 2016 introduced the definition of non-methane volatile organic compounds (NMVOCs), meaning “all organic compounds, other than methane, that can produce photochemical oxidants by reaction with nitrogen oxides in the presence of solar radiation.”

How to measure emitted VOCs

Stack limits are verified by specific analytical methods.

There are automatic methods which apply the flame ionization principle and express the result in mg Carbon/Nm3, (indicated as TOC = Total Organic Carbon). These methods aren’t qualitatively selective and do not distinguish the single volatile organic compounds.

For the most dangerous compounds, on the other hand, the most suitable method is by adsorption on activated carbon vials, with subsequent desorption and gaschromatographic determination, able to distinguish the individual compounds both qualitatively and quantitatively. The methods are:

  • UNI EN 13649 for single compounds
  • UNI EN 12619 for VOC < 20 mg/Nm3
  • UNI EN 13526 for VOC ≥ 20 mg/Nm3

VOCs: how to comply with the emission limits?

A number of different approaches can be adopted in order to comply with the new emission limits, including both actions on the used products (e.g. water-based, high-solids paints and inks, etc.) and implementation of appropriate emission abatement systems. In some cases, it is necessary to adopt both solutions to ensure compliance with the enforced limits.

Having among its range of products basically all the possibilities of treatment of emissions containing VOC (from recovery, to thermal destruction, to wet abatement, etc. …), BROFIND can recommend to each customer the best abatement system by finding the best compromise between investment costs and management of the plant.