RTOs vs. Carbon Adsorbers vs. Wet Scrubbers: Which Air Pollution Control Technology Is Right for You?

Choosing the right air pollution control system can be the difference between an efficient, compliant manufacturing operation and one that haemorrhages energy costs while struggling to meet permit limits.

If your facility produces volatile organic compounds (VOCs), hazardous air pollutants (HAPs), acid gases, or odorous emissions, you’re likely weighing up three of the most widely deployed abatement technologies: Regenerative Thermal Oxidisers (RTOs), carbon adsorbers, and wet scrubbers.

Each technology has its place, but none is universally superior. The right choice depends on your waste gas composition, flow rates, concentration levels, regulatory requirements, and long-term operational economics.

In this guide, we break down how each system works, where it excels, and the critical factors that should guide your decision.

How Each Technology Works

Regenerative Thermal Oxidisers (RTOs)

An RTO destroys VOCs and HAPs through high-temperature combustion, typically between 850°C and 950°C. The pollutant-laden exhaust enters a ceramic media bed that preheats the incoming air using energy stored from the previous cycle. The gas then passes into a combustion chamber where VOCs are oxidised into carbon dioxide and water vapour, relatively harmless byproducts compared to untreated emissions.

RTOs are cyclic systems. In a three-canister RTO, for example, one canister acts as the inlet (preheating the incoming gas), another as the outlet (storing heat from the treated exhaust), and a third is purged to prevent untreated emissions escaping during the cycle change. This purge cycle is what gives three-canister and five-canister RTOs their lower emission spike profile compared to simpler two-canister designs.

The ceramic heat recovery media typically achieve thermal efficiencies of 85% to 97%, which means the system recaptures most of the energy needed to sustain combustion. When the incoming waste gas carries sufficient solvent concentration, generally above 1.5 to 2.0 g/m³ of VOCs, the RTO can operate in auto-thermal mode, requiring no auxiliary fuel at all. This is a major cost advantage in high-throughput manufacturing.

Destruction efficiency: Over 99% with proper design.

Carbon Adsorbers

Carbon adsorption uses activated carbon to capture VOCs and other organic compounds from an exhaust stream. As polluted air passes through a bed of granular or pelletised activated carbon, organic molecules adhere to the carbon surface. Once the carbon reaches saturation, it must be either regenerated (using steam or hot gas to desorb the captured compounds) or replaced entirely.

Carbon adsorbers work best at low to moderate VOC concentrations and ambient or near-ambient temperatures. They are particularly effective for capturing specific solvents from well-characterised waste streams, and in some applications, the recovered solvent can be reclaimed and reused, adding an economic benefit beyond compliance.

However, carbon systems have limitations. High-humidity environments reduce adsorption capacity. Particulate loading can foul the carbon bed. And for high-concentration or high-volume waste streams, the frequency of regeneration or carbon replacement can make operating costs prohibitive.

Destruction/capture efficiency: Typically 90% to 98%, depending on the compound and bed condition.

Wet Scrubbers

Wet scrubbers remove pollutants by bringing the contaminated gas stream into contact with a scrubbing liquid, usually water, sometimes with chemical reagents such as sodium hydroxide (NaOH) or sulphuric acid. As the gas passes through the scrubber (whether a packed bed tower, venturi, or spray chamber), pollutants are absorbed or chemically neutralised in the liquid phase.

Wet scrubbers are the go-to technology for acid gases (HCl, SO₂, ammonia), water-soluble compounds, and particulate matter. They’re also widely used for odour control in food processing, wastewater treatment, and composting operations.

Unlike RTOs, wet scrubbers don’t rely on combustion, so they carry no explosion risk and can handle corrosive compounds that would damage thermal oxidation systems. However, they produce a liquid waste stream that requires treatment or disposal, and they are generally less effective at removing non-water-soluble organic compounds.

Removal efficiency: Typically 95% to 99% for target compounds, depending on scrubber type and chemical dosing.

Head-to-Head Comparison

Pollutant Suitability

The takeaway: if your primary challenge is VOC destruction from solvent-based processes, printing, coating, or lamination, an RTO is almost certainly the right choice. If you’re dealing with acid gases or odour from food, pharmaceutical, or waste processes, a wet scrubber is the natural fit. Carbon adsorbers occupy the middle ground for lower-concentration VOC streams or where solvent recovery is desirable.

When to Consider a Combined Approach

In many manufacturing environments, a single technology doesn’t cover the full spectrum of emissions. A printing facility, for example, might use an RTO as the primary abatement system for high-volume solvent-laden exhaust from press dryers, while deploying a wet scrubber on a separate process line that generates acid fumes.

Integrating your abatement technologies with the upstream process is equally important. In the print and packaging sector, dryer optimisation, reducing exhaust air volumes while safely increasing VOC concentration levels in compliance with EN1539:2015 can shrink the required RTO capacity, reduce auxiliary fuel consumption, and unlock heat recovery potential that offsets energy costs across the facility.

This integrated approach, examining the dryer, the central ductwork, and the abatement system as a connected system rather than isolated components, is where the greatest efficiency and cost gains are typically found.

Making the Right Choice

The decision between RTOs, carbon adsorbers, and wet scrubbers should be driven by a thorough understanding of your specific waste gas characteristics, regulatory obligations, and operational priorities. A detailed process survey, measuring exhaust air volumes, temperatures, VOC concentrations, and pollutant composition across your actual production conditions, provides the data needed to size and select the right system with confidence.

At Operational, we’ve spent over 30 years engineering bespoke air pollution control solutions across print and packaging, food and beverage, textiles, automotive, ceramics, and utility sectors. As an independent engineering company, we’re not tied to a single technology; we design, install, and maintain RTOs, wet scrubbers, carbon adsorbers, and integrated systems, recommending the solution that’s genuinely right for your process.

If you’re evaluating your air pollution control options, contact our engineering team for an initial site survey and consultation.

Operational (UK) Limited provides turnkey air pollution control, dryer optimisation, heat recovery, and planned preventative maintenance services from our UK headquarters in Runcorn, Cheshire. We support manufacturers across the UK, Ireland, and Europe.