Capturing formaldehyde and acetaldehyde: stricter emission standards from end 2026
Emission standards for formaldehyde and acetaldehyde are becoming stricter. The challenge is real, but certainly solvable: for virtually every emission profile, Trevi offers a technique that removes these aldehydes from the waste gases and makes the new limit achievable.
Stricter emission standards: from 20 to 5 mg/Nm³ by end 2026
Today, a general emission limit value of 20 mg/Nm³ applies to formaldehyde and acetaldehyde, taking effect from a mass flow of 100 g/h (VLAREM II, Annex 4.4.2). The new European BAT conclusions for waste gas treatment, with which existing installations must comply by 12 December 2026 at the latest, tighten that limit considerably. For formaldehyde, a carcinogenic substance (CMR category 1B), the limit drops to 5 mg/Nm³ and the threshold shifts from 100 g/h to just 1 g/h. Acetaldehyde is a suspected carcinogen (CMR category 2) and falls less sharply: it comes under the CMR category 2 limit of 10 mg/Nm³ from 50 g/h, and it also counts towards the overarching TOC limit of 20 mg C/Nm³.
Parameter: Formaldehyde (CMR-categorie 1B)
From: 1 g/h
New limit value: 5 mg/Nm³
Parameter: Acetaldehyde (CMR-categorie 2)
From: 50 g/h
New limit value: 10 mg/Nm³
Parameter: Totaal organische koolstof (TOC)
From: /
New limit value: 20 mg C/Nm³
Trevi provides the right technique for every emission profile
Trevi never starts from a fixed technique, but from the needs and possibilities on site. In practice, the choice comes down to two techniques: biofiltration and scrubbing.
Biofiltration: for large, continuous waste gas streams
For large, continuous gas flows with low concentrations, biofiltration is usually the technique of choice. Through biofiltration, micro-organisms break the aldehydes down biologically into water and CO2. For an international chemical company with an acetaldehyde-rich stream, Trevi was able to carry out successful lab tests in its own laboratory.
The initial investment in a biofilter is somewhat higher than for other techniques, but this is offset by a particularly low operating cost. Apart from periodically replacing the biofilter material, a biofilter requires hardly any maintenance. The micro-organisms do the work virtually for free.
When there is little available space on site, or the aldehyde emission comes from a batch process with occasional peaks, gas scrubbing tends to be the more appropriate route.
Scrubbing and gas washing: from water scrubber to reductive scrubber
Trevi always examines the simplest and cheapest option first. Because formaldehyde dissolves well in water, a water scrubber is often sufficient. Preferably, the scrubber is integrated into the production process in order to get the most out of the investment.
- Process-integrated water scrubber: By integrating the scrubber into the process, the wash water is not discharged as a separate waste water stream but returned to the process. In this way the water is usefully reused, for example to dilute raw materials. Trevi designed a water scrubber for a partner to treat the vapours from storage tanks, with the collected wash water reused to dilute raw materials.
- Water scrubber coupled to an existing biological wastewater treatment plant: attractive when that plant still has spare capacity and the purge water can be treated in this way.
- Reductive scrubber: When the purge water volume has to be kept to a minimum, a reductive scrubber is the most appropriate choice. Whereas a conventional water scrubber must continuously supply fresh water to keep dissolving the compound, a reductive scrubber adds a reducing agent such as sodium bisulphite. This reacts with the formaldehyde or acetaldehyde and converts it into a non-volatile component, so that the installation runs much longer on the same wash water and requires only a limited purge.
And this is not just theory. Trevi validated the process in practice by demonstrating, through pilot trials at a partner, that formaldehyde could be removed from a waste gas stream in this way. The process was then scaled up to a fully operational model.
Dry filtration with Chemisorb: for small, concentrated streams
For gas streams with a low flow rate and low or high concentrations, Trevi deploys alternative carrier materials such as Chemisorb P. These adsorbents are more expensive than activated carbon but tackle substances that activated carbon fails to handle. At Trevi, Chemisorb P is used to capture aldehydes such as formaldehyde and acetaldehyde, achieving a higher adsorption capacity than activated carbon. In that specific segment, a dry filter with Chemisorb is a fully-fledged solution.
Activated carbon is not the solution for formaldehyde and acetaldehyde
Activated carbon is an excellent solution for many volatile organic compounds, but precisely for formaldehyde and acetaldehyde the adsorption capacity is, based on Trevi's experience, limited, so it is rarely the most cost-effective option. In our own lab tests, the loading on activated carbon proved to be only 1 to 3%, and that at relatively high concentrations. This is consistent with reference data for activated carbon, which describe formaldehyde and acetaldehyde as barely adsorbable.
Thermal post-combustion works technically, but is too expensive for most of these applications.
From study to follow-up
Whatever the technique, Trevi's approach remains consistent:
- Study of the actual situation on site: flow rate, concentration, continuous stream or batch, available space and the limit to be met.
- Lab and pilot trials where necessary, to thoroughly investigate the chosen solution.
- Realisation of the system at full scale.
- Follow-up of the installation.
Existing installations can, moreover, often be upgraded: depending on the configuration, an existing scrubber can be converted to the reductive concept.
Do you have formaldehyde or acetaldehyde emissions that stay just within the limit today, but may no longer do so from end 2026?
Trevi Environmental Solutions assesses, based on your waste gas stream, which technique is most suitable for you.