Fugitive Emissions in Roto, Flexo & Lamination
Key Factors
In the flexible packaging industry, solvent-based converting activities like Rotogravure (Roto) printing, Flexographic (Flexo) printing, and Coating/Lamination/Lacquering are cornerstone processes for delivering durable, high-quality packaging materials. These operations rely on solvent-based inks, lacquers, varnishes and adhesives to achieve rapid drying and strong adhesion, but they also generate fugitive emissions, uncontrolled releases of volatile organic compounds (VOCs) in the production floor, that differ markedly across the three methods. These variations are driven by the distinct printing/converting processes, machine layouts, and the often-overlooked factor of machine age. For engineers tasked with optimizing emission controls (through a SRU™, Solvent Recovery Units or RTO™, Regenerative Thermal Oxidizers) while ensuring compliance with environmental regulations, dissecting these influences is critical.
Fugitive Emissions: Scope and Significance
Fugitive emissions are VOCs that evade capture systems during solvent-based converting processes, escaping from ink, lacquer, varnish or adhesive application, drying stages, and ancillary tasks like machine cleaning or solvent handling. These emissions contribute to air pollution, operators exposure risks, and regulatory scrutiny, making their management a priority in modern packaging facilities.
The differences in emission profiles among Roto, Flexo, and Lamination reflect both operational mechanics and equipment design, amplified by the age of the machinery in use.
Even in single-line converting systems, peripheral operations and ancillary solvent handling, such as ink dispensing, adhesive mixing, and cleaning with solvent-soaked rags or automated CIP systems, require rigorous scrutiny, as they can elevate fugitive VOC concentrations beyond primary process emissions. A good operator training can help reduce the fugitive emissions: ink or adhesive tanks left open encourage solvent evaporation. Air conditioning the production room, maintaining a temperature that is not excessively hot, helps to drastically reduce fugitive emissions, also improving working conditions.
Rotogravure (Roto) Printing: Process, Layout, and Age effects
Rotogravure printing utilizes engraved metal cylinders with recessed cells to transfer solvent-based ink/lacquer/varnish onto substrates. A doctor blade ensures precision by removing excess ink, followed by high-speed drying, via hot air, typically heated through hot oil heat exchangers, or through steam coils, or through an indirect burner or through electric batteries.
Fugitive emissions in Roto are shaped by:
Process Characteristics: the deep cells in gravure cylinders hold more ink, and thus more solvent, than other methods, increasing VOC release during application and drying. An enclosed inking system limits initial evaporation compared to open designs, but the thicker ink films demand robust drying, amplifying emissions.
Machine Layout: roto presses feature in-line configurations with sequential print stations (elements) and extended drying tunnels. This spread-out layout allows integration of advanced capture systems and LEL control (e.g. FRS™, advanced Flow Recirculation Systems), but uncaptured VOCs can escape from solvent-heavy zones.
Machine Age: older roto presses, common in facilities with legacy equipment or those using regional manufacturing lines, may lack modern dryer designs equipped with efficient drying hoods or Lower Explosive Limit (LEL) recirculation systems. Inefficient floor sweeps, intended to remove solvent vapors from the press area, coupled with outdated drying tunnels exacerbate fugitive losses. These older tunnels often achieve capture efficiencies as low as 70-80%, compared to 90% or higher in newer models featuring advanced airflow management and recirculation. At high production speeds, these deficiencies become more pronounced, as inadequate hood design and poor LEL control fail to contain the increased VOC load, allowing more emissions to escape into the atmosphere. Low-cost presses, in particular, may reflect cost-driven designs from past decades, prioritizing output over emission control, further compounding losses in aging fleets.
Roto typically generates higher fugitive emissions than Flexo or Coating/Laminating due to its solvent-intensive process, with machine age and regional manufacturing variations, significantly widening the gap in older setups lacking modern containment technology.
Flexographic (Flexo) Printing: Process, Layout, and Age effects
Flexo printing employs flexible plates mounted on a rotating cylinder, often in a central impression (CI) configuration, to apply low-viscosity, solvent-based inks. Drying occurs via hot air, typically heated through hot oil heat exchangers or an indirect burner.
Fugitive emissions in Flexo arise from:
Process Characteristics: the ink and anilox roller system expose solvent-rich ink to the atmosphere, leading to evaporation before substrate contact. Thinner ink films require less solvent than Roto, moderating VOC output, but the continuous exposure during printing drives fugitive losses. An advantage of flexo is the possibility of almost total closure of the CI area (available on all modern machines) which makes it much easier to reduce fugitive emissions.
Machine Layout: flexo’s compact CI design clusters print stations around a central drum, reducing the distance between ink application and drying. This CI tight layout, including the adoption of enclosed doctor blade chambers (vs. ink fountains and ink pans) aids ventilation focus leading only a minor quantity of solvent vapours to uncaptured, allowing only a minor quantity of VOCs to escape from unenclosed areas. In case of Flexo stack configuration, more similar to Roto, featuring in-line configurations with sequential print stations (elements), fugitive emissions are higher than the most common CI design, due to the spread-out of the printing units which makes it more difficult to contain emissions.
Machine Age: older flexo presses often feature rudimentary drying hoods or ink pans layouts, with capture efficiencies lagging behind modern units (e.g., 80% versus 90-95%). Back doctoring or trail doctoring in aging machines further increase fugitives, wasted ink, and substrate. These legacy designs, lacking advanced enclosed chambers or integrated LEL control (e.g. FRS™, advanced Flow Recirculation Systems), struggle to manage VOCs effectively, resulting in nuisance but also representing a costly problem.
Flexo’s fugitive emissions are generally lower than Roto’s, with older machines amplifying losses due to outdated dryers and ink pans layout.
Lamination (Lam), solvent based: Process, Layout, and Age effects
Lamination bonds multiple substrate layers (e.g., films, alu-foils, paper) using solvent-based adhesives to enhance barrier properties or durability. Unlike printing, it focuses on adhesive application rather than ink.
Fugitive emissions in Lamination arise from:
Adhesive Application: Solvent-based adhesives are applied via rollers or nozzles in wet or dry lamination processes. In wet lamination, the adhesive remains liquid during bonding, leading to significant VOC evaporation. Dry lamination involves drying the adhesive before bonding, concentrating emissions in the drying phase. Another source of fugitive emissions is the coating station: in modern machines it is enclosed in order to convey and minimize the emissions.
Drying Stage: Lamination requires extensive drying to cure adhesives, often using heated rollers or ovens/tunnels. The large surface area of adhesive-coated webs increases VOC release, and incomplete capture in drying tunnels contributes to fugitive emissions.
Machine Layout: Laminators feature flat configurations to handle broad webs, with adhesive application and drying zones in sequence. This layout allows for efficient exhaust systems, resulting in perfromant capture efficiencies (typically around 90%).
Recent lamination lines typically generates the lowest value of fugitive emissions among the three processes, thanks to its efficient layout and capture systems.
Why Fugitive Emissions Vary: Key Influencing Factors
Fugitive emission levels differ across Rotogravure (Roto), Flexographic (Flexo), and solvent-based Coating/Lamination (SB_Lam) converting lines due to a combination of technical and operational variables. As a rough estimate, the percentage of solvent input lost as fugitive VOCs can be approximated as follows:
| ROTO |
FLEXO |
SB_LAM |
| 12-25% |
8-15% |
8-12% |
The variations of the estimated values of fugitives, are influenced by the below main factors:
converting line layout;
legacy and configuration of the line;
environmental conditions and seasonal changes: a temperature shift from 25°C to 40°C increases solvent vapor pressures, boosting fugitive emissions. Elevation above sea level further amplifies this effect, as lower atmospheric pressure reduces boiling points, enhancing solvent volatility. Higher humidity values can suppress evaporation slightly due to water vapor competition, though temperature remains the dominant driver.
Behavioral Approach of Operators;
Press Room Design: maintaining a too high positive pressure in the printing room to prevent dust ingress can inadvertently increase fugitive losses. This overpressure drives VOC-laden air outward through unsealed gaps or vents (e.g. doors, windows, cracks), counteracting capture systems.
These factors collectively shape the observed emission profiles, with Roto exhibiting the highest variability due to its solvent-intensive process and its spread-out layout, Flexo balancing moderate losses with layout advantages, and SB_Lam maintaining lower fugitives via efficient design, having only one (duplex) or two (triplex) coating stations.
Engineering Solutions and Considerations
Precision-engineered solutions can mitigate fugitive emissions:
DEC.FRS™: adopting the LEL automatic Flow Recirculation Systems will allow the unit to monitor the effective performance of the drying hoods, while generating important operational savings;
DEC.RBC™: adopting the Rotary Bed Concentrator will allow to concentrate the fugitives properly prior to abate them in a VOC emission control system (e.g. SRU™, Solvent Recovery Units or RTO™, Regenerative Thermal Oxidizers);
DEC.PTE™: installing a Permanent Total Enclosure achieves near-100% containment of fugitive VOCs by maintaining negative pressure around the converting line. This curbs operator exposure to hazardous solvents (e.g. toluene) while restricting access to high-risk zones, enhancing safety and compliance with stringent regulations;
Ink cooling: keeping the ink at the desired temperature will drastically reduce the evaporation of the solvents, while stabilizing viscosity for consistent print quality;
Upgrading & retrofitting: retrofit legacy presses with upgraded high-efficiency hoods, applying enclosures around the inking systems, while re-engineering the floor-sweep network, will allow to efficiently capture more fugitives;
Training: structured training programs on solvent handling, inks management, equipment maintenance (e.g., LEL), and cleaning protocols can lower fugitive emissions by reducing human-induced losses.
Conclusions
Fugitive VOC emissions in solvent-based Roto, Flexo, and Lamination processes diverge due to intricate process mechanics, machine configurations, and age-related performance gaps. Roto’s solvent load, Flexo’s exposure dynamics, and Lamination’s adhesive efficiency are modulated by design and amplified by legacy equipment inefficiencies. Advanced fugitives control through DEC.RBC™ units enables engineers to slash emissions (e.g., from 20% and above, down to 10% or lower), balancing technical precision with environmental compliance.
