VOC treatment: our analysis of the situation for the industry

Protocols, directives and municipal by-laws: several texts regulate emissions of volatile organic compounds and aim to reduce them. Let's take a look at the applicable texts:

International regulation

At the international level, two protocols are particularly relevant to VOCs:

• The Geneva Protocol - Long-range Transboundary Air Pollution in 1991.
  It aims to control emissions of several air pollutants - including VOCs - and their transboundary flows.

• The Gothenburg Protocol - Reducing acidification, eutrophication and ground-level ozone in 1999.
  It concerns several pollutants (sulphur dioxide, nitrogen oxides, ammonia), which are responsible for acidification and eutrophication, and emissions of volatile organic compounds (VOCs) which, together with NOx, are responsible for the accumulation of ozone in the lower atmosphere.

The European regulation

A succession of complementary directives, transposed into French law in the form of decrees or orders, make up the European regulations in this area:

Directive 1996/61/EC, known as IPPC (Integrated Pollution Prevention and Control), harmonises the rules for the authorisation and control of industrial installations with a high pollution potential on a European scale. In particular, it requires operators to implement the best available techniques (BATs), which are referenced in sectoral or cross-sectoral documents called BREFs.

Directive 1999/13/EC, on VOC emissions from solvent use, imposed limit values for channelled and diffuse VOC emissions and specific obligations concerning the most toxic solvents (reduction, substitution). This directive introduces :

• emission limit values (ELVs), which distinguish between channelled, diffuse and total ELVs;
  

• the implementation of a solvent management plan (SMAP), a real identification tool for all incoming and outgoing solvent flows from an installation;

• the implementation of the Emissions Management Scheme (EMS), which focuses on the annual flow of VOC emissions, and enables work on reduction actions implemented on all emission sources present on the same industrial site.

These last two directives were repealed and integrated on 24 November 2010 into the Industrial Emission Directive (IED) 2010/75/EU, which reinforces the reference to BAT and the reference documents to these BATs, the BREFs.

Finally, Directive 2001/81/EC of 23 October 2001, known as the NEC (National Emission Ceilings), sets national emission ceilings for certain atmospheric pollutants, including VOCs (transposition at the European level of the Gothenburg Protocol).

National regulations

The national regulation concerns Installations Classified for the Protection of the Environment (ICPE).

The ministerial decree of 2 February 1998, on which the installations subject to authorisation depend, is fundamental on three levels:

• reference to emission limit values (channelled ELVs, diffuse ELVs) and the particular case of specific VOCs;
• Solvent Management Plan (SMP): identification of the main discharge points and prioritisation of treatments according to the importance of the different flows identified;
• the Emission Control Scheme (EMS), which offers an alternative to regulation and is in no way mandatory.
  

On the other hand, for certain production sites, specific limits applicable only to them are determined by their prefectural operating permit order, exempted by the DREAL.

Reviews and next steps

In the coming years, several regulations will be revised. This is particularly the case for BREFs, which are being revised sector by sector, and BAT-AELs (Best Available Techniques, Associated Emissions Limits), which set stricter emission limit levels.
It is also envisaged that the Order of 2 February 1998 will be revised, although no date has yet been set.
The general trend is therefore to increase pressure on industry to reduce pollutant concentrations in air emissions, particularly specific VOCs, which are targeted by even lower limits in many sectors .

There are several technologies for treating air emissions, each with its advantages and limitations.

Treatment processes fall into two broad categories:

• recovery processes, including absorption by washing, adsorption on activated carbon, condensation, or separation on membranes.

• destructive processes, which include biological treatment, thermal oxidation (RTO) and catalytic oxidation
  

When selecting air emission treatment technology, the choice is often between a regenerative thermal oxidiser (RTO) and activated carbon filtration:

Thermal oxidation burns all organic compounds in the air at high temperatures. For high concentrations of VOCs on a continuous basis, it is generally an efficient and cost-effective method. However, thermal oxidation is not ideal for dealing with fluctuating concentrations or batch operations. In this case, natural gas must be added to the stream to keep the temperature stable. The cost of operation can then become very high and uneconomic.

Activated carbon filters do not burn, break down or modify molecules, but simply adsorb them onto the pores of the carbon filter bed. There are different types of carbon depending on the compound to be adsorbed, and the filters are sized according to the flow rate and input concentrations. This flexibility makes activated carbon suitable for many applications, but if VOC concentrations are very high, carbon consumption may be excessive and filter replacement too frequent to be cost effective. Thermal systems or a combination of treatments should then be considered instead.