In short
- Wet chemical scrubbers handle high and fast-changing loads best.
- Biofilters often have the lowest whole-life cost on moderate, steady loads.
- Activated carbon is best as a polishing stage or for small, light duties.
There is no single best odour technology. There is a best match between a technology and your load: how strong it is, how much it varies, and what compounds it contains. Getting that match wrong is the usual reason an odour system works on paper and fails in practice.
This comparison draws on a published planning assessment of odour abatement options, alongside our own experience of chemical scrubbing.
The options side by side
| Technology | How it works | Strengths | Limits |
|---|---|---|---|
| Wet chemical scrubber | Gas absorbed into acid, caustic or oxidising liquor | Adapts quickly to changing loads; removes ammonia with an acid stage; proven | Chemical handling, running and calibration costs |
| Biofilter (organic media) | Bacteria on wood chip or similar media break down odours | Low whole-life cost; treats many compounds | Heavy loads shorten media life; media replacement is labour-intensive |
| Bio-scrubber (inert media) | Bacteria on long-life inert media | High H2S removal; smaller footprint; media can last 10 to 20 years | Needs steady loading; weak on mercaptans and similar compounds |
| Activated carbon or impregnated media | Odour adsorbed onto solid media | Simple; low maintenance; no start-up period | Exhausts quickly at high load; sensitive to moisture |
Start with the load profile
Measure or estimate the peak and the average concentration, not just one of them. A wastewater inlet works, a tanker unloading bay or a batch process can swing from almost nothing to very high in minutes.
Biological systems need a steady diet. They acclimatise to a load and struggle when it changes suddenly. Chemical scrubbers respond within seconds because the dosing system follows the gas. Carbon has a fixed capacity, so high loads simply use it up faster.
Not sure what your load looks like?
Tell us the source and any readings you have. We will tell you what to measure and which technology fits.
Combining technologies
Many of the most reliable systems use two technologies in series. A chemical scrubber takes the bulk load and the peaks; a carbon polishing stage catches what remains. Equally, a biological stage can handle the steady base load with a chemical stage in reserve for peaks.
Ammonia-rich streams nearly always need an acid stage, because biofilters and carbon are poorly suited to high ammonia.
Engineer's note
Sites often come to us with a carbon unit that exhausts far quicker than expected. That usually means the load is higher or more variable than the carbon was sized for, and a chemical stage ahead of it is the cheaper long-term fix.
Running costs to compare
- Chemical scrubber: reagents, water, bleed disposal, power and instrument calibration.
- Biofilter: media replacement every few years, irrigation water and power.
- Carbon: media replacement frequency, which rises directly with load.
Leaning towards chemical scrubbing? Our odour control scrubbers page shows the single and two-stage designs we build.
See odour control scrubbersWhere odour is one part of a wider chemical extract, multi-stage scrubbers let you treat acid gases, ammonia and sulphur compounds in one package.
Common questions
Which is cheapest to run?
On moderate, steady loads a biofilter is often cheapest over its life. On high or variable loads a chemical scrubber is usually more economical, because carbon or biological media would need frequent replacement.
Can activated carbon remove H2S on its own?
At low concentrations, yes, particularly with impregnated media. At higher loads the media exhausts quickly, so it is better used as a polishing stage.
How quickly does a chemical scrubber respond to a peak?
The absorption itself is immediate. Dosing control then restores the liquor strength, so performance holds through short peaks if the design allows for them.