Study on Recovered Paper Quality in Germany and Method for ...In this study, about 40 quality parameters were determined for the most important recovered paper grades in terms of quantity

Study on Recovered Paper Quality in Germany and Method for Determining the

Composition of Recovered Paper Samples

Tobias Krebs, Hans-Joachim Putz, Samuel Schabel

Technical University Darmstadt - Paper Technology and Mechanical Process Engineering (PMV)

ABSTRACT

Paper products, and thus recovered paper, are subject to changes and innovations like many other products. The effects

of these innovations are evident in the recycling cycle and continuously change the quality of recovered paper. As part

of a comprehensive study, the current status of recovered paper quality in Germany was determined and the data

obtained was compared with previous studies. The investigations were limited to the most important grades of

recovered paper. Samples of recovered paper were taken representatively from all over Germany. On these samples,

the composition, the moisture content, mechanical, optical and suspension properties as well as chemical constituents

were examined. An important quality parameter in the analysis of recovered paper is the composition of the recovered

paper grades. Today, the analysis of the composition of recovered paper samples is often still carried out manually,

which leads to very high personnel costs. As part of the project, a fully automated system for analyzing the composition

of recovered paper samples was developed. The system isolates objects from the paper samples and places them

individually in a measuring cell where they are analyzed by sensors and assigned to one of 10 object classes with the

aid of artificial intelligence.

INTRODUCTION

In the German paper industry, about 17 million tons of recovered paper are used every year as raw material for the

production of 22.9 million tons of paper and cardboard [1]. This corresponds to a utilization rate of almost 75%.

Recovered paper is thus the most important raw material in the German paper industry. In an international comparison,

Germany is also among the leaders with its use of recovered paper. The European average recovered paper utilization

rate is around 52 % [2]. In Europe, recovered paper is divided into a large number of different classes according to the

European List of Standard Grades of Paper and Board for Recycling EN 643 [3]. Since the revision in 2013, this

standard contains some fundamental improvements, especially with regard to the tolerance limits for non-paper

components and a detailed description of the individual grades. Nevertheless, this information is not sufficient to

deduce the quality of the individual recovered paper grades in terms of their potential for producing new paper and

board products.

Paper products, and thus also the quality of recovered paper, are subject to numerous changes and innovations. The

effects of these innovations are noticeable in the recycling cycle. This effect often only becomes visible after a period

of enrichment. For example, the trend towards high print gloss means that graphic papers are now often coated, which

significantly increases the proportion of mineral additives in recovered papers of the graphic grade groups. In

packaging papers, however, there is a trend towards higher-quality products with white outer layers facing the

consumer. This tends to lead to high-quality cellulose fibers in the grades of recovered packaging paper. These and

other developments in paper end products are constantly changing the quality of recovered paper. In order to monitor

this dynamic process, a continuous measurement of quality properties is necessary. For this reason, the Institute for

Paper Technology and Mechanical Process Engineering conducts a study on the status quo of recovered paper quality

in Germany approximately every 10 years [4, 5, 6, 7]. Due to the limitations in time and financial resources as well as

the great effort due to the large number of tests carried out and the measured parameters on the individual samples,

not all grades in the standard grade list can be tested. Therefore, the investigations are limited to the three most

important grades 1.02.00 (mixed paper and board), 1.04.00 (corrugated paper and board packaging) and 1.11 (sorted

graphic paper for deinking), which together already make up a large part of the recovered paper traded in Germany.

These grades therefore give a good impression of the current recovered paper quality in Germany. In addition to the

composition, the study also examines the suspension properties, mechanical properties and chemical constituents of

the previously mentioned recovered paper grades. In order to obtain a comprehensive overview of the current

recovered paper quality in the whole of Germany and to avoid giving too much weight to possible regional

peculiarities, samples from a total of 10 sites distributed throughout the whole of Germany were examined. The sites

included paper mills as well as paper sorting plants and recovered paper traders. The sample quantity of the individual

samples was chosen such that the composition is representative for a recovered paper delivery. How this can be

achieved is described in literature [8, 9]. Depending on the grade, the size of a sample was between 40 kg and 100 kg.

In this project, particular attention was paid to determining the composition of the recovered paper samples. To the

best of our knowledge, there is currently no automatic measuring device that allows the composition of recovered

paper samples to be analysed in accordance with EN 643. For this reason, recovered paper samples that required an

exact determination of the composition were always counted manually in the past. This process is particularly time-

consuming. Depending on the sample composition, the counting of 10 kg of sample material can take up to 3 hours

[10]. Within the scope of this project, the development of an automatic measuring system should be advanced in order

to significantly reduce the time and personnel effort of sample analysis.

MEASURING SYSTEM FOR THE COMPOSITION ANALYSIS OF RECOVERED PAPER SAMPLES

The aim of the measuring system is to analyze recovered paper samples of up to 100 kg automatically with regard to

their composition. For this purpose, an approach similar to manual sample analysis was chosen: In manual analysis,

each object is picked from the sample, examined and then categorized. The measuring system should function in the

same way. Figure 1 illustrates the structure of the measurement system, which is described below. Basically, the

system is divided into two parts: The first part of the system is intended to separate the paper objects, while the second

part is intended to classify the paper objects.

Figure 1: Schematic structure of the measuring system for automatic determination of the composition of recovered

paper samples.

During operation of the system, it is filled with a (partial) sample. The first step is to isolate the paper objects and

remove unwanted impurities. To do this, the sample first passes through a screen drum feeder. In this drum, small

particles such as sand, glass or paper shavings can be removed from the measuring system through holes in the wall

that function like a screen. This material is collected in a container, weighed manually and then disposed of. In

addition, the sample material is rectified by the drum. At the outlet of the drum, the paper falls onto a conveyor belt,

at the end of which a robot with a specially developed paper gripper and object recognition transports paper objects

into the measuring cell separately. In order to be able to grip as many paper objects as possible, the gripper developed

uses two working principles. Paper objects can be sucked in with vacuum as well as mechanically gripped with a

gripper. Sensors are integrated in the gripper to monitor the gripping process and ensure that no object is lost unnoticed

during transport.

In [10] a sorting catalogue was proposed according to which paper objects can be divided into a total of 18 different

classes according to the specifications of EN 643. However, some of these classes are very rare in recovered paper

collected from households. As the training of algorithms requires a lot of training data for each class and is accordingly

associated with a lot of effort, the class catalogue was reduced to the substance classes relevant for municipal recovered

paper. The reduced catalogue can be seen in Table 1.

Table 1: Reduced sorting catalogue for recovered paper according to [10].

substance classes description

newspaper contain journalistic articles; single pages up to complete

newspapers; no page cutouts

magazines complete magazines

advertising print brochures and flyers, containing descriptions of goods and services

paper (white) writing and office papers made of white or very light fiber material

paper (gray) writing and office papers made of grey or yellowish fiber material

corrugated board (brown) with two brown cover layers

corrugated board (white) with one or two white cover layers

cardboard (gray) at least one grey, brown or solid-colored layer

cardboard (white) fibers completely white, yellowish or bright

other packaging papers packaging papers not covered by other classes

In the measuring system, each object is analyzed with the help of sensors and features are extracted. Most of the

features are obtained by image analysis. For this purpose, a photo is taken with a standard industrial camera and

processed with a number of algorithms. Furthermore, a photo with UV illumination is taken to determine a measure

for the optical brighteners in the paper object. The mass of the object is determined using a continuous weighing

machine. The features extracted in this way are then used to classify the paper objects. A specially trained classifier

is used for this purpose. This classifier, a support vector machine, has been trained with data of almost 10,000 paper

objects. It has learned to distinguish the 10 paper classes described above. Figure 2 shows the success rate with which

the measuring system classifies the various paper objects into the correct class.

It becomes clear that some classes are already very well recognized (brown corrugated board, newspapers, white

paper), while other classes still need improvement (cartons, white corrugated board). For this reason, further sensors

for the measurement system are currently being tested to extract additional features of the paper objects and thus

further improve the classification.

RESULTS OF THE STUDY ON RECOVERED PAPER QUALITY IN GERMANY

In this study, about 40 quality parameters were determined for the most important recovered paper grades in terms of

quantity in Germany. These grades are defined in EN 643: Grade 1.02.00 (sorted, mixed recovered paper) is a mixture

of different paper and cardboard grades, consisting of a maximum of 40 % newspapers and magazines. Grade 1.04.00

(department store recovered paper) contains used paper and board packaging, containing a minimum of 70 % of

corrugated board, the rest being other packaging papers and boards. Grade 1.11.00 (deinked goods) is sorted graphic

paper, consisting of a minimum of 80 % newspapers and magazines. It has to contain at least 30 % newspapers and

40 % magazines. Print products which are not suitable for deinking are limited to 1.5 %. From the determined

characteristics, recovered paper processing companies can derive the utility value of the respective grade of recovered

paper. Basic properties (e.g. moisture content, composition, ash content), pulp and paper technology properties (e.g.

micro and macro sticky content, fiber fractions, tear strength, tear propagation work, flat crush resistance, brightness)

as well as chemical constituents (e.g. chemical oxygen demand, pentachlorophenol) of the recovered paper grades

were therefore analyzed. An overview of all the parameters investigated can be found in Table 2.

Figure 2: Success rates of the classification of paper objects from the reduced sorting catalogue.

The investigations for grade 1.11.00 differ slightly from the investigations for grades 1.02.00 and 1.04.00. Since grade

1.11.00 is mainly used for the production of new graphic papers, optical properties play a very important role here. In

this grade, the recovered paper is deinked and all optical parameters are measured on both the deinked and the

undeinked pulp. Optical properties play a rather minor role in grades 1.02.00 and 1.04.00. Because they are mainly

used in packaging papers, their mechanical properties are much more important. For this reason, some additional

mechanical parameters are included for these grades. A detailed description of all results of the study would go beyond

the scope of this publication. For this reason, only a few exemplary results are shown in Figure 3.

The composition of the recovered paper grades investigated is shown in section (a) of Figure 3. A rough distinction is

made between packaging papers, graphic papers, unsuitable/other papers and non-paper materials. In addition, a more

detailed analysis was carried out. In this analysis, all objects of the samples were assigned to one of 18 substance

classes. An extract from this sorting catalogue is shown in Table 1. It is noticeable that grade 1.04.00, which should

only consist of packaging papers, contains a not inconsiderable proportion of other papers and therefore, strictly

speaking, does not comply with standard EN 643. The same applies to grade 1.11.00 with regard to graphic papers.

Also remarkable is the high proportion of graphic papers in grade 1.02.00 of more than 60 %.

Since the 1980s, the ash content of the three grades of recovered paper investigated has risen continuously. This

increase is due to the increased use of fillers in the paper products and to the increasing or further increasing closure

of the recycling cycles. This trend has been broken with the latest study. For the first time, no increase in the ash

content of recovered paper could be observed (Figure 3 (b)). The ash content is thus at the same level as in 2010.

Today (2019) the average ash content of recovered paper grades 1.02.00 is 21%, 1.04.00 17% and 1.11.00 24%.

In recent studies, a slight decrease in brightness has been observed continuously for grade 1.02.00. This time there

was a slight increase so that the 1999 level was reached (Figure 3 (c)). The downward trend of the 1.04.00 brightness

continues. It should be mentioned, however, that the optical properties of these two varieties play little or no role at

all. For grade 1.11.00, the brightness has remained constant since the 1990s. For the undeinked pulp (UP) it is 45 %,

for the deinked pulp (DP) 57 %.

In 1999, extensive investigations were carried out for the first time to determine the macro sticky content as part of

the series of investigations, as can be seen from Figure 3 (d). The values of the grades 1.02.00 and 1.11.00 have

remained approximately at the level of 2010. For grade 1.04.00, however, there was an increase. This increase is most

60%

57%

49%

55%

92%

73%

85%

70%

77%

86%

0% 20% 40% 60% 80% 100%

Other Packaging Papers

Cardboard (white)

Cardboard (gray)

Corrugated Board (white)

Corrugated Board (brown)

Paper (gray)

Paper (white)

Advertising Print

Magazines

Newspaper

likely due to the increased number of adhesive applications in the packaging domain.

For more detailed results and information, please refer to the published final report of the study [11]. On the whole,

most parameters were measured with values similar to those of the 2010 study. A significant deterioration in the

quality of recovered paper, which is often deplored, could not be confirmed based on the data of this study.

Table 2: Overview of all investigated parameters in the current study on recovered paper quality in Germany.

parameters grade

1.11.00

grade 1.02.00

& 1.04.00

basic properties

moisture content X X

composition: X X

packaging paper and cardboard X X

graphic Papers X X

unsuitable/other papers and cardboards X X

non-paper components X X

chemical pulp to mechanical pulp ratio X X

suspension properties

ash conent (575° C, 900° C) X X

dewatering (Schopper-Riegler-value) X X

water retention X X

fiber fractionating (Haindl-McNett) X X

macro sticky area X X

macro sticky content X X

micro sticky content X X

optical properties

dirty specks X X

brightness X X

luminosity X X

CIE-LAB color space X X

ERIC X

yield X

mechanical properties

breaking length (80 g/m2) X X

burst strength (80 g/m2) X X

tearing strength (80 g/m2) X X

ring crush test (130g/m2) X

flat crush resistance (130g/m2) X

short-span compression strength (130g/m2) X

chemical constituents

chemical oxygen demand X X

organic halogen compounds X X

pentachlorophenol X X

phthalates X X

cationic demand X X

heavy metals X X

(a)

(b)

(c)

(d)

Figure 3: Selected results of the study on recovered paper quality in Germany.

62,7

12,6

93,0

29,7

84,3

5,4

5,8 2,6 1,01,8 0,5 0,6

0

20

40

60

80

100

1.02.00 1.04.00 1.11.00

mas

s fr

acti

on [

%]

graphic papers packaging papers other papers non-paper components

0

5

10

15

20

25

30

1.02.00 1.04.00 1.11.00

ash c

onte

nt

at 5

75

°C

[%

]

1984 1994 1999 2010 2018

20

30

40

50

60

1.02.00 1.04.00 1.11.00 (UP) 1.11.00 (DP)

bri

ghtn

ess

R4

57

[%

]

1984 1994 1999 2010 2018

0

10.000

20.000

30.000

40.000

50.000

1.02 1.04 1.11

stic

ky a

rea

[mm

²/kg]

1999 2010 2018

CONCLUSION

Within the framework of the study carried out on recovered paper quality in Germany, the existing data from previous

decades could be extended by current values. Essentially, the measured values were in line with expectations. With

the help of these values, paper manufacturers can determine the value of the investigated grades for the production of

new paper products. In addition, the measured values allow a look into the future through the analysis of trends, so

that one can be prepared for changing recovered paper quality.

It has also been possible to develop a measurement system that analyses automatic recovered paper samples with

regard to their composition. The analysis is inspired by manual analysis. Individual objects are isolated from the

sample taken, analyzed and classified into one of 10 object classes. The classes were derived from the European List

of Standard Grades of Paper and Board for Recycling EN 643. On average, 3 out of 4 paper objects were assigned to

the correct class.

OUTLOOK

The developed measuring system will be further improved. Additional sensors are currently being tested to extract

more features from the paper objects. This will further improve the classification of the objects. One of these sensors

is a hyperspectral camera. For each pixel, this camera records an intensity value for 224 different wavelengths between

900 nm and 1700 nm. This results in a spectrum in the near infrared range for each pixel. This can be used to determine

characteristics such as ash content, lignin content or the proportion of pulp and mechanical pulp in the paper objects.

Non-paper objects can also be distinguished from paper objects.

The analysis of recovered paper samples is not only interesting for quality studies. It can also provide valuable data

for other research topics. For example, the analysis of samples from the incoming and outgoing streams of sorting

processes can be used to derive models for these processes. The composition of individual models enables complex

sorting plants to be simulated and optimized. Probably because of the time-consuming sample analysis, there are

hardly any models available for recovered paper sorting plants [10]. The use of the automatic measuring system will

simplify the creation of such models in the future.

ACKNOWLEDGMENTS

This research project was funded by “Arbeitsgemeinschaft industrieller Forschungsvereinigungen "Otto von

Guericke" e.V. (AiF)” in the framework of a program for promotion of common industrial research and development

(IGF) by the Federal Ministry of Economics and Technology (BMWi) on the basis of a decision by the German Federal

Parliament (project number 19118 N).

REFERENCES

1. N.N.: Papier 2018 - ein Leistungsbericht. - Verband Deutscher Papierfabriken e.V., Bonn, 2018. -

2. N.N.: Key Statistics 2017. - Confederation of European Paper Industries, 2017. -

3. EN 643:2014, Paper and board. European list of standard grades of paper and board for recycling.

4. Neukum, P.: Zusammensetzung und Qualität von Altpapier in Abhängigkeit der reginalen und saisonalen

Erfassung. - IfP Darmstadt, 2000. -

5. Phan-Tri, D.: Physikalische, chemische und mikrobiologische Charakterisierung verschiedener industrieller

Altpapiersorten. - IfP Darmstadt, 1982. -

6. Putz, H.-J.: Steigende Altpapiererfassung und ihre Konsequenz für die Qualitätseigenschaften verschiedener

Altpapiersorten. - WfP 124, 1996. - 74-79 S.

7. Weinert, S.: Qualitätseigenschaften der wichtigsten Altpapiersorten in Abhängigkeit von den

Sortierbedingungen. - IfP Darmstadt, 2010. -

8. Flamme, S.: "Altpapier - Bewertung der Qualitätskontrolle und Aufbau eines Qualitätsmanagement-

Systems". - IWARU Münster, 2016. -

9. prEN 17085:2018, Papier und Pappe - Probenahmeverfahren für Altpapier.

10. Gottschling, A.: Modellierung und Simulation von Altpapiersortieranlagen. - Technische Universität

Darmstadt, Doctoral dissertation, 2016.

11. Krebs, T.: Neue Methoden zur Erfassung der Altpapierqualität hinsichtlich der Kriterien der Neufassung der

DIN EN 643 zur Charakterisierung der Altpapiersorten. - PMV - TU Darmstadt, 2019. -

Gateway to the Future

Study on

Recovered Paper Quality in Germany

and Method for

Determining the Composition of Recovered Paper Samples

Agenda

Project overview

Recovered paper quality in Germany

Measuring system for the composition of recovered paper

01

02

03

212th Research Forum on Recycling | Tobias Krebs 10/29/2019

01

02

03

1.04.00

corrugated paperand

board packaging

1.02.00

mixed paperand

board

Three paper grades (EN 643) investigated

01

02

03

1.11.00

sorted graphicpaper fordeinking

02

03


01

02

03

Representative sampling all over Germany

01

02

03


10 10 10

40 kg 100 kg 40 kg

01

02

03

Large number of parameters measured

01

02

03 8mechanicalproperties

12suspensionproperties 6

chemicalconstituens

10optical

properties

composition& humidity


01

02

03 020406080

100

1.02.00 1.04.00 1.11.00

mas

sfra

ctio

n[%

]

graphical papers packaging papersother papers non-paper components01

02

EN 643 often not fulfilled

01

02

03


01

02

03

Trend of rising ash content has stopped

01

02

03 0

10

20

30

1.02.00 1.04.00 1.11.00

ash

cont

ent

at 5

75 °C

[%]

1984 1994 1999 2010 2018


01

02

03

Higher strength despite more recycling

01

02

03 100

150

200

1.02.00 1.04.00 1.11.00

burs

ting

stre

ngth

[kPa

]1984 1994 1999 2010 2018


01

02

03

COD rises due to increased use of starch

01

02

03 0

30

60

1.02.00 1.04.00

CO

D [k

g O

2/t]

1984 1994 1999 2010 2018


01

02

03 20

40

60

1.11 UP 1.11 DPbrig

htne

ss R

457

[%]

1994 1999 2010 2018

Deinkability results unchanged

01

02

03


01

02

03

02

03

Setup of measuring system

01

02

03

cameralighting

light barrier

weighing belt


conveyor belt

light barrier camera robotscreen drum

01

02

03

Classification of paper objects

01

02

03

length

width

weight

color

contrast

pattern

…

machinelearning


01

02

03

Machine learning basics

01

02

03

trainingdata

machinelearning

x y

predictionunknowndata

pre-processing

model

xy


01

02

03

Classification success

01

02

03

89%82%66%89%80%93%56%57%70%48%

10 c

lass

es


01

02

03

Measuring system in action

01

02

03


Outlook

incominginspection

statisticalstudies

models ofseparation processes

evaluation ofsorting plants


01

02

03

01

02

Thank you for your attention !

Tobias Krebs +49 (0) 6151 16-22720 [email protected]

Prof. Dr.-Ing. Samuel Schabel

Dr.-Ing. Hans-Joachim Putz

Funded by:


01

02

03

Questions?


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02

01

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Documents

Study on Recovered Paper Quality in Germany and Method for ...In this study, about 40 quality parameters were determined for the most important recovered paper grades in terms of quantity