Evaluation of paper recyclability

Hat differences between laboratory methods

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Daniele Bussini

Graduated in Environmental Sciences at the University of Milano- Bicocca, since 2004 at Innovhub-Area Carta (SSCCP). An expert in paper process sustainability and recycling, he is involved in research projects, analytical services and technical consultancy for companies in the paper chain.

With the aim that a single test method for measuring the recyclability parameters of paper and board products on a European level could be developed in the future, Innovhub compared the two methods and evaluation systems currently used by the paper industry:  at European and Italian level,  respectively Version 2 of the Cepi method Version 2 andand the UNI 11743Aticelca 501 method. Here is what emerged

In 2022, Cepi published Version 2 of the European test method for measuring recyclability parameters of paper and board products, developed in cooperation with stakeholders from the entire paper value chain, including research centrescenters and specialised testing laboratories.

At the Italian level, the UNI 11743 technical standard combined with the Aticelca 501 Evaluation System, a scheme widely used by companies and recognised nationwide, has already been available for years.

The two methods and their evaluation systems – currently both used by companies in Italy – present some differences in the analysis procedure and significant differences in the evaluation of results. The future objective is to have a single test method that is recognised at European level. In the meantime, a possible correlation between the results obtained with the two methods is being studied so that the Aticelca evaluation can also be applied to the results obtained according to the Cepi procedure.

The Cepi method Version 2

Cepi, the European Confederation of the Paper Industry, published in October 2022 the updated European test method for assessing the recyclability of paper and board products intended for recycling in standard plantsmills. The test method has been developed over the past few years thanks to the synergetic work of the various players in the entire paper industry, with contributions from leading European research centrescenters and laboratories in the field.

The test method makes it possible to emulate under laboratory conditions the processes that commonly occur on an industrial scale in paper recycling plantsmills.

The updated Cepi method provides a solid basis for companies aiming to achieve ever-higher circularity and sustainability performance for their products and allows the recyclability of paper products to be tested across Europe under identical conditions. The ultimate goal is to make all paper packaging recyclable by 2025 and achieve a 90% recycling rate by 2030.

The work was also supported by the members of 4evergreen https://4evergreenforum.eu/, an alliance of companies that brings together the entire fibre-based packaging chain, including many blue chip companies globally. The three new technical annexes include a detailed description of the test procedure, a test report template for laboratories and a decision scheme for the assessment of visual impurities.

4evergreen published the first Beta Version of the ‘recyclability assessment protocol’ in December 2022, which allows for an assessment score based at the moment on some of the parameters measured in the laboratory test. The 4evergreen assessment does not currently allow for the issuing of an identification mark to be placed on the packaging similar to the Aticelca recyclability mark.

The CEPI European Laboratory Test Method Version 2 and its annexes are available on the Cepi website: https://www.cepi.org/cepi-recyclability-test-method-version-2/.

While the 4evergreen Beta release evaluation protocol is available at 4evergreen:

https://4evergreenforum.eu/about/guidelinesandprotocol/.

Comparison between the Italian method and the Cepi method

The Cepi method and the 4evergreen evaluation protocol respond to the growing interest of consumers and packaging users in the issues of recyclability of paper and cardboard packaging, which formerly led, in 2019, to the definition of the UNI 11743 italian standard and Aticelca 501 Evaluation System, a reference point widely used by companies in Italy, and its subsequent harmonisation at European level, promoted by Cepi.

The UNI 11743 standard, together with the Aticelca 501 Assessment System, is well known and used in the supply chain in Italy. In particular, a growing interest has been noted over the last few years, due to the drive towards improving the environmental performance of products, the evolution of regulations concerning these issues, and the attention of product end users and consumers.

The two methods have a similar execution procedure with regard to the first stages of the test, from sample preparation to pulping and coarse reject determination.

The Cepi method specifies some additional details for the first two steps: sample preparation and pulping.

– Sample preparation: materials and products containing WSA must have been produced at least 30 days prior to testing. If this is not the case, artificial ageing of the sample in an oven at a temperature of 60 °C for 72 hours is required.

– Pulping: The water used must have a certain pH range; as with the UNI method, there is the possibility of increasing the pulping time to 20 minutes, instead of 10 minutes, if the coarse reject consists predominantly of cellulose fibres and exceeds the maximum limit defined in the evaluation protocol.

The subsequent determination of the coarse reject is performed in exactly the same way in the two methods and it is assumed that the results obtained are similar.

An important innovation of the Cepi method is the analysis of the filtrate obtained from the stock pilepulp by gravimetric determination of the dry residue after evaporation. There is also the optional measurement of the COD of the filtrate by means of the cuvette method.

The subsequent fine screening phase is performed with the same instrumentation, but in the case of the Cepi method, some parameters are different: the quantity of sample used and the test time are greater. Based on the experience of the first months of use of the Cepi method, it was found that normally the value of Fine Screening/Flake measured with the new Cepi method is lower than the value measured with the UNI procedure. This aspect, however, needs to be studied for a larger number of samples to see if a clear correlation between the two types of results can be found.

The procedure for obtaining the final sheets used for the evaluation of optical inhomogeneity and adhesiveness – by means of the adhesion test – is similar, however in the case of the Cepi method the mixture accepted after the fine screen with 0.15 mm slits is used, while in the case of UNI the mixture accepted after the screen with 0.1 mm slits is used. for the determination of Macrostickies.

Lastly, the procedure precisely for the determination of Macrostickies, which is optional in the Cepi method, involves the use of similar instrumentation, but in the Cepi method a screen with 0.15 mm wide slits is used, whereas in the UNI standard the slits have a width of 0.1 mm.

A discussion coordinated by Cepi is currently underway at European level to verify the possibility of making the measurement of Macrostickies and possibly COD compulsory in the Cepi test method. In Italy, a research project is also underway, financed by various companies in the sector, to study an improvement in the procedure for determining and measuring Macrostickies, particularly for certain types of materials for which the current method is not sufficiently precise and suitable.

While the analysis procedure of the new Cepi method is similar to the UNI to a large extent, the 4evergreen assessment protocol, current Beta version, provides a very different evaluation and limits for some parameters.

The 4evergreen evaluation protocol allows a recyclability score to be calculated on the basis of the results of the parameters Coarse Rejection, Fine Rejecttion, Optical Inhomogeneity and Sheet Adhesion (adhesion test on final sheets).

The first two parameters, coarse and fine rejects, determine the yield and the corresponding score calculated according to the following formulae:

Y (performance score) = 100% – TR

where TR is the Total Rejection (%) calculated as follows:

TR = CR + FR * α

CR: Coarse rejectwaste (%);

FR: Fine rejectwaste (%);

α: correction factor of  0,9.

The third parameter of Optical Inhomogeneity is evaluated with a level between 1 and 4 according to the decision scheme attached to the method and this level is then converted into a negative score that is subtracted from the yield score.

The last parameter, sheet adhesion, is assessed in the Cepi method with a level between 1 and 3. Levels 1 and 2 do not lead to any penalty in the score, while level 3 leads to a judgement of non-recyclability, regardless of the result of the other parameters.

A new project in progress

At the moment, the two test methods and their evaluations coexist on a national level, and the possibility of applying the Aticelca Evaluation System also to results obtained according to the Cepi method is being studied, in order to facilitate companies that operate in different countries or have already tested with the new method.

In addition, a work financed by Aticelca and Comieco is being started, with the aim of establishing a possible correspondence or correlation between the results of the parameters obtained with the two different methods. The project involves four specialised Italian laboratories and envisages carrying out a significant number of recyclability tests on products representative of the different categories, using both test methods.

With a view to the future, it is considered useful and desirable to have a standard for testing the recyclability of paper products throughout Europe under identical conditions. Cepi recently presented the method to CEN, the European Committee for Standardisation, to start a discussion that could lead, in the next few years, to an EN standard recognised throughout Europe, after UNI had already made available in the past the national standard UNI 11743, the first and only case of a method for assessing recyclability on a laboratory scale available in European national standards.