A new approach to recycling paper-based packaging aims to counteract the gradual deterioration of recycled fibres. By separating and selectively refining the fines in the pulp, the process improves the mechanical properties of paper while reducing energy consumption, additive use and the impact on drainage capacity
As part of European circular economy policies, the recycling of paper-based packaging plays a prominent role and is one of their key pillars. As is well known, paper and board have the highest recycling rates among packaging materials and, according to data cited by the Centre Technique du Papier (CTP), the recycling rate for paper-based packaging in Europe reached 83.1% in 2025. However, the very success of recycling is creating new technical challenges for paper mills.
At the Aticelca 2026 Congress, Alain Cochaux, an expert in the collection, sorting and recycling of packaging at CTP, addressed these issues.
Preserving fibre properties
In particular, the CTP expert presented an innovative project developed to tackle one of the typical and most significant problems in recycling: the gradual deterioration of the mechanical properties of recycled fibres.
“The idea is to improve the mechanical properties of these fibres,” explains Cochaux. Unlike materials such as glass and metals, cellulose cannot be recycled indefinitely. After each recovery cycle, fibres undergo physical changes that reduce their ability to bond with one another. “We know that the properties of recycled fibres and the paper produced from them deteriorate,” the expert says. On average, a fibre can be reused between five and seven times, but each cycle entails a gradual loss of its original characteristics.
A second factor compounds this phenomenon. “When paper is recycled, the mineral filler content also increases, further contributing to the loss of mechanical properties.” The presence of mineral fillers, originating mainly from graphic papers, has a significant impact on performance. According to data reported by CTP, a filler content of 10% can reduce mechanical properties by approximately 10%, while concentrations of around 20% can result in losses of up to 40%.
This problem is compounded by the continuous reduction in grammage. On the one hand, market demand is driving the development of lighter packaging; on the other, the new European Packaging and Packaging Waste Regulation (PPWR) and the EN 13428 standard reinforce the principle of prevention through source reduction. As a result, paper mills must produce increasingly lightweight papers without compromising their mechanical performance.
To compensate for the loss of mechanical properties, many paper mills resort to increasing amounts of starch applied at the size press. However, this solution entails significant operating costs and does not always make it possible to fully recover the required performance.
These considerations led to the development of the ClipIndus project.
A new concept for packaging recycling
The idea behind the process developed by CTP is to rethink stock preparation by acting not on the entire fibrous suspension, but only on one specific component: the fines. “The new concept we have developed for recycling is relatively simple,” explains Cochaux. “The basic principle of ClipIndus is to use micro-holed fractionation technology to separate the fibrous suspension into two distinct streams: one fraction consisting mainly of fibres and another composed of fines.” The latter generally accounts for 20% to 30% of the total pulp by weight. Once the two fractions have been obtained, “only the fines fraction is refined. The two streams are then mixed again to obtain the final stock.”
This approach differs significantly from conventional processes. In traditional lines, material from the pulper passes through a series of cleaning and screening stages designed to remove contaminants. When refining is used, it is generally applied to the entire fibrous suspension. However, the expert explains, this solution has several operational limitations and can lead to fibre deterioration, as well as significant energy consumption.
“Over the years, fractionation systems based on the separation of short and long fibres have also been developed. However, they have not always delivered the expected results, both because of the limited actual differences between the two fractions and because of the distribution of contaminants within the separated streams.”
ClipIndus follows a different approach. The aim is not to separate fibres according to their length, but to isolate the fines and treat only these.
How the idea emerged and how it works
The project was developed around a number of specific objectives. On the one hand, the treatment had to be adapted to the specific characteristics of the different components of the stock; on the other, energy consumption had to be limited while keeping the fibres intact. “We want to preserve the structure of the fibres,” says Cochaux. “We do not want to increase the damage caused by recycling cycles.”
By separating the suspension into a fibrous fraction and a fines fraction, and refining only the latter, energy is concentrated on the part of the stock that can benefit most from the treatment. At the same time, the fibres are spared further mechanical stress (Figure 1).
The results obtained during the project’s development showed very significant improvements in mechanical properties. “The tests showed improvements of between 15% and 20% in the CMT index — crush resistance —, the SCT index — short-span compression strength — and burst strength, with only a limited penalty in drainage.” Under certain experimental conditions, the improvements were even greater. Furthermore, “another advantage is the possibility of integrating the system into existing recycling lines without fundamentally changing the overall plant configuration,” thereby reducing implementation costs.
Micro-holed fractionation
One of the project’s most innovative aspects concerns the choice of separation technology. To identify the most effective solution, CTP tested several micro-holed baskets. “Apertures of 250, 500 and 800 microns were evaluated,” Cochaux continues, explaining that the tests showed that the 250-micron basket provided highly effective separation of fines and fibres, but required operating conditions that were difficult to manage. The low inlet consistency required, the high pressure drop and the risk of clogging limited its industrial applicability. At the opposite end of the range, the 800-micron basket offered simpler operating conditions but insufficient selectivity. “The best compromise was achieved with the 500-micron basket. We obtained good separation between fines and fibres, together with stable operating conditions.”
This configuration was validated both at CTP’s pilot plant and during a 72-hour industrial trial at a paper mill in northern France. “During the test, operating conditions remained stable, with a constant composition of the separated fractions and regular consistency and fractionation-ratio values.”
The results confirmed the industrial feasibility of the concept and the possibility of integrating micro-holed fractionation into an existing recycling line.
Refining only the fines
Once the fines fraction had been separated, however, a new problem emerged: thickening the material before refining.
Conventional systems generally rely on the formation of a “fibre mat”, a layer of fibres that retains solid particles while allowing water to be separated. In the case of ClipIndus, however, the fines fraction contains few fibrous elements, and artificially recreating this layer would have proved inefficient. “We had separated the fines from the fibres, so recreating the fibre mat would not have been a good idea,” says Cochaux.
To solve the problem, several systems were tested until the most effective solution was identified: a decanter centrifuge. “The equipment made it possible to achieve solids retention rates of 98% and consistencies well above those required for refining. The initial target was a consistency of 5%, but the tests demonstrated that values of 20% could be reached and, under ideal conditions, even higher ones.”
The use of a decanter centrifuge therefore overcame the main technical obstacle in the process, making it possible to proceed with refining the fines fraction.
“Once thickened, the fines fraction was refined using discs designed with a cutting length of 95 km/s, and we tested different energy levels. Energy was applied exclusively to this part of the stock, while the fibrous fraction remained completely unaffected.”
The technical principle behind the ClipIndus process is therefore particularly interesting. By concentrating treatment on the fines, it promotes the development of active surfaces and bonding capacity without exposing the fibres to further shortening or damage.
“Once refining was completed, the treated fraction was recombined with the previously separated fibrous fraction.”
According to CTP’s conclusions, this strategy makes it possible to achieve improvements in mechanical properties of between 15% and 30% compared with untreated pulp, while keeping energy consumption under control. “The useful energy consumption for refining is around 50 kWh/t, calculated on the basis of the entire stock.”
Costs and results
An important part of the project was devoted to economic analysis. To assess the industrial viability of ClipIndus, CTP used the PS2000 simulation platform, developed to support paper mills in their investment decisions.
The simulations considered different scenarios in terms of plant size, energy costs and payback periods. Different investment levels were also assessed for large and small paper mills.
One of the most interesting aspects concerns the relationship between improved performance and stock drainability. “In conventional refining, improvements in mechanical properties are often accompanied by a significant reduction in drainage capacity. With ClipIndus, by contrast, the deterioration in drainage is much more limited for the same amount of energy applied. Mechanical properties also improve to a greater extent than with a conventional process,” Cochaux states.
This result is particularly relevant for mills producing containerboard, where maintaining paper machine productivity is essential.
Benefits for paper mills
The industrial implications of the process could be significant, as improved mechanical properties open up several operational opportunities. The first concerns “reducing the use of starch and other chemical additives employed to compensate for the deterioration of recycled fibres”. According to the assessments presented by CTP, improved performance may make it possible to reduce or even eliminate certain treatments, offsetting a significant part of the additional costs introduced by the process.
Another opportunity concerns the commercial positioning of products. “By improving mechanical properties, the paper mill will have the opportunity to move from Testliner 3 to Testliner 2,” observes Cochaux. In other words, improved performance could enable mills to access higher-value market segments, thereby increasing the overall profitability of production.
The process also addresses the need to reduce grammage, “making it possible to maintain high performance levels even with lighter papers”.
Towards industrial implementation
CTP currently considers the ClipIndus concept essentially ready for full-scale industrial implementation. Pilot trials, testing at a paper mill and economic simulations have made it possible to validate both its technical and economic aspects. “ClipIndus is ready for full industrial deployment,” says Cochaux. “However, we need the support of equipment suppliers to build large-capacity plants.” The next phase will therefore require collaboration between research centres, equipment manufacturers and paper mills interested in testing the system on a production scale.
Ultimately, CTP’s project addresses the core needs of paper mills. Faced with the gradual decline in recycled fibre quality and growing pressure to produce ever-lighter papers, the new solution changes the approach by focusing on the selective enhancement of the fines in the stock. Based on the results obtained so far, this solution could help improve paper performance while reducing energy consumption and the use of chemical additives.