Waste Management 31 (2011) 370377

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Waste Management
journal homepage: www.elsevier.com/locate/wasman

Construction materials as a waste management solution for cellulose sludge

R. Modolo a,, V.M. Ferreira a, L.M. Machado b, M. Rodrigues c, I. Coelho c
a

University of Aveiro, Civil Engineering Department/CICECO, 3810-193 Aveiro, Portugal

RAIZ Forest and Paper Research Institute, Portucel-Soporcel, Eixo, Portugal
c
CIMIANTO Sociedade Tcnica Hidrulica, S.A., Alhandra, Portugal
b

a r t i c l e

i n f o

Article history:
Received 12 April 2010
Accepted 15 September 2010
Available online 12 October 2010

a b s t r a c t
Sustainable waste management system for efuents treatment sludge has been a pressing issue for pulp
and paper sector. Recycling is always recommended in terms of environmental sustainability. Following
an approach of waste valorisation, this work aims to demonstrate the technical viability of producing
ber-cement roof sheets incorporating cellulose primary sludge generated on paper and pulp mills.
From the results obtained with preliminary studies it was possible to verify the possibility of producing
ber-cement sheets by replacing 25% of the conventional used virgin long ber by primary efuent treatment cellulose sludge. This amount of incorporation was tested on an industrial scale. Environmental
parameters related to water and waste, as well as tests for checking the quality of the nal product
was performed. These control parameters involved total solids in suspension, dissolved salts, chlorides,
sulphates, COD, metals content. In the product, parameters like moisture, density and strength were controlled.
The results showed that it is possible to replace the virgin long bers pulp by primary sludge without
impacts in nal product characteristics and on the environment.
This work ensures the elimination of signicant waste amounts, which are nowadays sent to landll, as
well as reduces costs associated with the standard raw materials use in the ber-cement industrial
sector.
2010 Elsevier Ltd. All rights reserved.

1. Introduction
Sustainability concept is becoming increasingly important for
several industrial sectors, including the paper and pulp sector as
well as the building sector, because they present a strong impact
as important economical activities (Lopes et al., 2003). The waste
management is becoming a priority and the building sector is
one of the most useful sectors for diverse applications, in order
to close with value the life cycle of certain products.
The use of industrial waste and by-product materials is widely
recognized as one of the major preferred options towards the
achievement of sustainable development. The prevailing environment policies require the waste to be treated before going to landll. Treating waste and valuing them as raw materials for
construction or other ends is more sustainable, particularly, when
wastes are already on site. (Snelson et al., 2009).
A pulp and paper mill generates, in all stages of process production, large amounts of solid wastes differing greatly in composition
and moisture content. In its ber production line, the screening
equipment discharges uncooked material from the digester and

Corresponding author. Tel.: +351 234 370 049; mobile: +351 964 471 677.
E-mail address: regina.modolo@ua.pt (R. Modolo).
0956-053X/$ - see front matter 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.wasman.2010.09.017

smaller screening rejects. The chemical recovery cycle produces

mainly inorganic material (called dregs and grits), energy production in the biomass boiler giving, as solid waste, y ash and purged
sand in the case of bubbling uidized bed (BFB) boilers and, nally,
also sludges coming from efuent treatment plant, classied as
primary and biological sludges according to their treatment
procedure.
Indeed, wastewater treatment plant is the biggest solid waste
producer, generating two types of sludges, primary and biological.
Primary sludge is mainly composed of ber, lost in different equipments along the ber line and settled in primary efuents treatment area. It also contains inorganic suspended solids, mainly
calcium carbonate from the caustic area. These solids are also decanted and become a primary sludge constituent. On integrated
pulp and paper mills this type of sludge has a much higher content
of inorganic fractions, as a consequence of the precipitated calcium
carbonate used as ller in paper production and in paper machine
white water excess.
Biological sludge comes from the biological treatment unit and
it contains microorganisms. This unit generally involves activated
sludge reactors and sludges are obtained through secondary
decanters, sludges thickeners and nal belt press dewatering.
Wastes from pulp and paper industry are usually managed, in
terms of waste disposal, using several approaches including

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R. Modolo et al. / Waste Management 31 (2011) 370377

landlls, incineration, recycling in cement or ceramics plants,

lightweight aggregates, asphalt, agriculture, anaerobic treatment,
and others (United Nations Economic and Social Council; Hassani
et al., 2005; Demir et al., 2005; Huet, 1982; Shao et al., 2001; IJF,
1994; Podobnik and Zule, 2006; Krigstin and Sain, 2006; Monte
et al., 2009; Lynde-Mass, 1997). Wastewater sludges were already
used in different sectors and the main applications are associated
to agricultural purposes, biomass, incorporation in clay bricks,
lightweight aggregates and in moulded gypsum cardboards production (United Nations Economic and Social Council; Modolo
et al., 1979).
Considering the large amount generation of primary sludge production and its brous nature, this work attempts to develop a
solution to add value to this material incorporating in a construction material where their brous nature could be advantageous.
For that, preliminary studies were developed at a laboratory level
in a base composition used in ber-cement sheets. The results
showed that primary sludge could be incorporated in ber-cement
sheets in low contents, without damaging the nal product characteristics (Modolo et al., 2007).
Fiber-cement is usually used as a building material in covering roofs, although it can be used for other constructive purposes. Its composition incorporates up to 2.6% of cellulose
bers coming from kraft softwood pulp (virgin long bers pulp
VLFP) in order to make advantageous use of its ber content.
These bers are longer and coarser than most bers and have
been found to provide many benets in ber-cement applications
due to their high modulus and high ber strength (Morton et al.,
2006).
The focus of this work is to evaluate the use of primary sludge
from kraft hardwood pulping process in ber-cement sheets production at an industrial scale. At this level, there is a need to control parameters such as the sludge incorporation level and its
quality as a raw material, the water quality in the process and
the nal product characteristics.
2. Experimental
Virgin long ber pulp (VLFP) represents 2.6% of total ber-cement composition in proportion of dry raw materials. Conventionally the used ber in ber-cement process production is from
softwood. In this experimental work, these softwood long bers
were replaced by hardwood bers from primary sludge generated
in pulp and paper mill efuent treatment at a xed replacement level of 25%.
2.1. Materials
2.1.1. Standard materials
The ber-cement sheet samples were prepared with standard
ber-cement raw materials: Portland cement (to provide strength):
Commercial available ASTM Type I 42.5R, PVAber (the long
term durability PVA bers is used as reinforcement in cementbase (Akers et al., 1989), and other commercial characteristics,
such as, high modulus polyvinyl alcohol, elongation (6.5%);
Amorphous-silica: Dry silica fume (Elken Microsilica Grade 940),
with high SiO2 content (>90%), low moisture (<1.0%), loss on ignition less than 3,0%, particle retention at 45 micron sieve below
1.5%, Bulk density (undensied: 200350 kg/m3); Virgin long ber
pulp: kraft pulp softwood bers, bleached, moisture (10%), Ash
content (<1.0%); Additives: (i) Flocculant (Magnaoc 1011): White
granular powder, solid grade polymer, particle size (98% <
1400 lm), Bulk density (0.65 g/cm3); (ii) Antifoam (STRUKTOL
J650): Polyalcohol based on polyoxyethylene-polyoxypropylene
blockcopolymers.

2.1.2. Primary sludge

The primary sludge is generated in the clarication of process
water by kidney treatments, e.g. dissolved air otation (Monte
et al., 2009). The sludge consists of hardwood bers (70%, where
a small content of this total may be associated with insoluble lignin) and llers (5% of sand and 25% of precipitated calcium carbonate (PCC)). The PCC content in the sludge is generated in the
integrated kraft pulp and paper process by the chemical reaction
CaO + CO2 M CaCO3, being limited by the calcium content measured as 10.37% (table 1) and its atomic mass (40 g/mol). The primary sludge specic characterization is presented on Table 1. Fig. 1
shows ber nature of this sludge and part of the inorganic content
material present in them.
2.2. Methods
In order to replace VLFP with primary sludge in ber-cement
production at an industrial scale, the following aspects were
veried:
 Process and environmental control: characterization tests in
process water (suspended solids and dissolved salts, chlorides,
sulphates, COD and metals) and cellulose VLFP beating degree
Shopper Riegler test SR (ISO, 1999);
 Final product: chemical and mechanical characterization tests
in nal product (according to Standard procedure); and
 Solution sustainability: evaluation of the sustainability of this
waste management solution.
Regarding the transportation process and incorporation, the
sludge was divided in big bags and previously weighed (Fig. 2).
The primary sludge was characterized and tested on the day that
it was received at the factory.
The ber-cement production process (Fig. 3) begins with VLFP
disintegration and a beating process. The beating process can be
dened as a mechanical treatment of pulp carried out in the presence of water and, in this case, by passing the pulp bers suspension through a disk rener consisting of a rotating bladed element
that moves in conjunction with a stationary bladed element. The
term beating is usually applied to the batch treatment of pulp
suspensions (Coutts, 2005). Coutts and Kightly (Coutts and Kightly,
1984) state that rening plays an important role in producing surface area for ber-to-ber or ber-to-matrix (in case of composites) bonding and, more important, can assist in controlling the
drainage rates of processing liquids during the fabrication of products. Rening affects the hydraulic properties of the ber effec-

Table 1
Specic characterization results for primary sludge.
Parameters

Value

Parameters

Value

Metals
Ca (% dried waste)
Mg (% dried waste)
Na (% dried waste)
Fe (% dried waste)
Al (% dried waste)
Mn (% dried waste)

10.7
0.19
0.22
0.09
0.05
0.03

Potentially toxic metals

Ni (mg/kg dried waste)
Cu (mg/kg dried waste)
Pb (mg/kg dried waste)
Zn (mg/kg dried waste)
Cd (mg/kg dried waste)
Cr total (mg/kg dried
waste)

12.1
10.7
16.3
36.5
1.7
13.4

Others
pH (Sorenson scale)
Condutivity (mS/m)

8
37

Au (mg/kg dried waste)

Co (mg/kg dried waste)
Ar (mg/kg dried waste)

0.2
10.0
5.8

Density (g/cm3)
Moisture (%)
Volatile total solids 550 + 25 C
(%)

0.5
67
70

Sulphates (% dried waste)

Chlorides (% dried waste)

0.3
0.6

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R. Modolo et al. / Waste Management 31 (2011) 370377

Fig. 1. Primary sludge microscope image (40 DIALUX 20 EB).

Fig. 2. Primary sludge ready to be processed and to be incorporated to the disintegrator in big bags.

tively reducing its average diameter. This process also promotes an

internal brillation or delamination on bers, external brillation
of its surface and nes formation.
In the pulp beating, the VLFP and sludge were mixed with
water. The disintegration process lasts around 30 min. In this
point a suspension sample is collected to measure the Shopper
Riegler degree (SR). If an acceptable SR value (between 55
and 70 SR) is obtained, the suspension is sent to the pulper.
Meanwhile, the silica was already mixed with water before processing. The pulp is mixed with cement, amorphous-silica and
PVA in the mixer. The nal suspension is carried to the ber-cement sheet forming machine which includes a felt belt and four
vats that lter the ber-cement sheets water excess. The bercement sheets are taken to the drying oven at 85 C to remove
the moisture.
The global ber-cement sheets production involves the following steps:
1.
2.
3.
4.
5.
6.

VLFP and/or Primary sludge disintegration

VLFP and sludge mixes beating
Pulper preparation
Silica suspension preparation
Sheets production
Sheets cutting

7. Sheets corrugations molds

8. Drying (naturally on air and in oven)
9. Removing moulds and pallet processing.
About 25% of the virgin long bers pulp (VLFP) used in ber-cement production were substituted by primary sludge in the industrial test. The ber-cement sheets are produced in batches. Each
production batch involves, in this particular factory, a consumption
of 195 kg of virgin long bers cellulose pulp. Hence, each batch received 4875 kg (dry base) of primary sludge and 14,625 kg of virgin
long bers pulp during industrial test days. Twelve ber-cement
series with primary sludge were produced in two days. The samples with sludge incorporation were collected for tests in this period and the reference samples were collected a week before, on
normal production days.
The cellulose sludge chemical parameters were previously
determined (table 1) and involved moisture, pH, organic contents
(550 C), ber content, conductivity, chlorides, sulphates, metals
and density.
Water samples from the process were also collected before and
during the industrial test. The samples named as CW represent the
Control Water and the PSW samples represent the Primary
Sludge Water. The measured water parameters were total suspended solids, dissolved salts, chlorides, sulphates and COD

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R. Modolo et al. / Waste Management 31 (2011) 370377

Virgin long fiber pulp

Primary sludge
PVA

MIXER
"PULPER"
DISINTEGRATOR

CEMENT AND AMORFOUS-SILICA

BEATING

FIBER-CEMENT MACHINE

VATS
FIBER-CEMENT SHEETS

- COLLECTING POINT

VACUUM PUMP

Fig. 3. Fiber-cement process and water collecting places.

Table 2
Samples control, parameters and respective Standard.
Samples

Parameters and methodology

Sludge

pH (EN 12176:1998); Conductivity (NP EN 27888:1996); Moisture in 105 C (EN 12880:2000); Silic and metals (ICP JY Inductively Coupled Plasma
Instrumental analysis technique based on atomic emission spectrometry), Fixed and Volatile Total Solids in 525 C (EN 12879:2000); Schopper Riegler
Degree and Beating time
Suspended total solids; Dissolved salts; Sulphates (4500D-SO4-2, STANDARD METHODS, Gravimetric with drying of residue, 4-177); Chlorides (4500DCl-, STANDARD METHODS, Potenciometric method, 4-69); COD; Metals
Load at rupture; Beding Moment ; density ; moisture (NP EN 494:2004 + A3:2008)

Water
Final
product

(Chemical Oxygen Demand) and metals content. The water samples collection places in the process are also presented on Fig. 3.
The parameters measurement methods are presented on Table 2.
During the ber-cement production process, the pulp and the
sludge were beat and the Shopper Riegler (SR) parameter was
measured. This parameter allows evaluating the pulp beating degree. This method is designed to provide a measure of the rate at
which a dilute suspension of pulp may be dewatered. The determination of the drainability of a pulp suspension in water is described
in terms of a Shopper Riegler (SR) number. The drainability is
related to the surface conditions and swelling of the bers, and
constitutes a useful index of the amount of mechanical treatment
to which the pulp has been subjected (Morton et al., 2006). In this
ber-cement production study case, the acceptable results are
obtained within the range of 55 to 70 SR, following the standard
proceedings. The highest this value less drainable is the bers cake.
The industrial test took 12 h in constant production. In the rst
6 h of manufacturing, 1500 sheets were produced with primary
sludge and 15 of them were randomly chosen as samples during
the test time and submitted to quality control parameters checking. In the last 6 h, 1500 standard sheets (without sludge) were
produced and 15 standard ber-cement sheets were selected for
tests with the same procedure as above. The controlled parameters
in the chosen sheets were moisture and wet density (in fresh

Fig. 4. Sheet prole and geometric symbols.

Table 3
Fibrocement sheet geometric characteristics.
Sheet geometric characteristics

Nominal Value
(mm)

Tolerance

Lenght of sheet (l)

Widht of sheet (w)
Pitch of the corrugations (a)
Height of the corrugations (h)
Thickness of the sheet (e)
Height of edge of the descending
corrugations (hi)
Height of edge of the ascending
corrugations (h2)
Category (according to the h)
Class

1250
1095
177
51
6.5
11

10
10
2
3
0.6
815

45

4249

C (4080)
1

conditions), dry density, bending moment and load at rupture (at

the seventh day of curing). The methodology used to carry on the
tests is described in NP-EN494:2004 + A3:2008 and the standard geometric sheets characteristics are presented on Fig. 4 and
Table 3.
3. Results and discussion
3.1. Process and environmental control
In terms of chemical characteristics, the primary sludge does
not present undesirable agents for ber-cement production. It consists primarily of bers, nes and inorganic material in mills that
employ llers in their products (Monte et al., 2009).
Fig. 5 presents the bers microscopic aspect. It is possible to
verify the difference between the Eucalyptus and Pinus bers thick-

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R. Modolo et al. / Waste Management 31 (2011) 370377

Fig. 5. Microscope images: (a) Primary sludge Eucalyptus globulus ber (Sample collected from primary sludge generated in kraft hardwood mill), (b) Eucalyptus globulus ber
and (c) Pinus pinaster ber (Sample was collected from virgin pulp produced in kraft hardwood and softwood mill). (100 DIALUX 20 EB).

Refinement Index ( SR)

75
70
65
63
60

60
58

57

60 60

59

58

61
59

58 58

56

55

60

61

60

59

60

61

58

57

58

50
N S

S N N N N S

High Limit SR

Low Limit SR

S N N N N

S N N

Samples (S=With sludge; N=without sludge)

Fig. 6. SchopperRiegler and renement time results (S - with sludge; N No sludge).

Refinement time (min)

35
30 30 30 30

30

30 30

30

30

25 25

25
25

25

25
20 20 20
20

20
20

20 20
20

20

15
N

S N N N N

N N N N

S N N

Samples (S=With sludge; N=without sludge)

Fig. 7. Renement time results (S - with sludge; N No sludge).

ness, around 1020 lm and 4060 lm, respectively. Eucalyptus

Globulus ber achieves 1 mm as maximum length. The Pinus
bers are longer than E. globulus ber. This characteristic could
condition the sludge incorporation content and nal product
characteristics.
The SchopperRiegler and renement time results are presented on Figs. 6 and 7, respectively. It was possible to decrease
the renement time in the process with the primary sludge incorporation. The Eucalyptus bers achieve the same SR degree using
lower energy time comparing to Pinus bers. Lower renement
time represents low energy consumption compared to the standard process containing only virgin long bers pulp. A 30% saving
time was estimated during the industrial test procedure.

No alterations were observed in terms of the suspension dispersion or occulation with the sludge incorporation. No corrections
during the tests were needed in terms of occulants.
Table 4 presents the measured water quality parameters
(control and sludge samples). The values do not indicate signicant
alterations comparing them in terms of COD, chlorides, sulphates,
dissolved salts and metals during the test period.
Due to the solids presence and shorter bers, there is a
possibility for nes passing to the process water. Total suspended
solids in PSW are only slightly higher than the control value
sample (Table 4).
The VLFP represent 2.6% of dry material in ber-cement production. 25% of this amount was substituted by primary sludge. Know-

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R. Modolo et al. / Waste Management 31 (2011) 370377

Table 4
Well and Vat 2 water samples results.
Parameters

Total suspended solids (g/l)

Chlorides (g/l)
Sulphates (g/l)
Dissolved salts (g/l)
Chemical oxygen demand
(g O2/l)
Na (g/l)
K (mg/l)
Ca (g/l)
Al (mg/l)
Fe (mg/l)
Pb (mg/l)
Cr (mg/l)
Cu (mg/l)
Zn (mg/l)

Results averages
WellCWa

WellPSWb

Vat2CWa

Vat2PSWb

26.9
2.5
8.4
20.8
1.3

36.1
2.4
8.2
26.3
1.7

26.5
2.5
7.8
23.8
1.0

31.5
2.3
7.2
26.0
1.1

0.6
8.2
0.8
0.2
0.2
27.0
2.2
18.7
35.6

0.7
7.4
0.8
0.2
0.3
27.0
2.1
24.4
36.4

0.7
8.1
0.8
0.2
0.2
31.7
2.4
24.4
46.5

0.7
7.6
0.8
0.2
0.3
28.6
2.3
26.8
35.2

Italic values indicate result under quantication limit.

a
CW Control Water.
b
PSW Primary Sludge Water.

ing that 40% of primary sludge composition is composed by inorganic material, the sludge suspended solids contribution in bercement production is estimated in 26 kg per ton of dried ber-cement produced. This maximum solids content increasing might be
retained on ber-cement sheets or drained to the process water together conventional solids.
The increasing of sulphates and chlorides present in sludge
composition parameters didnt have signicant alterations in
terms of process.

3.2. Final product control

In terms of moisture content, every value for sheets produced
with primary sludge achieved the specication limits. Fiber-cement sheets produced with primary sludge tend to present higher
wet density values than the standard sheets. This happens because
of shorter bers presence in their composition. These bers could
more easily retain water and solids between the sheet mesh spaces
(Table 5).

Table 5
Fiber-cement sheets control parameters results.
Parameters

Moisture (%)
Wet density (kg/dm)
Dry density (kg/dm)
Load at rupture (N)
Bending moment (Nm/m)
*

Continue production time/average sheets value

Quality control

Standard ber-cement (06 h)

S (deviation)

Primary sludge ber-cement (612 h)

S (deviation)

Min

Max

36
1801
1476
4693
56

1.28
0.02
0.03
2.12
15.12

36
1813
1485
5267
63

0.88
0.01
0.03
3.08
16.8

32
NA*
1400
4655
55

42
1850
NA*
NA*
NA*

NA = Non applied.

Fig. 8. Scanning electron microscopy of ber-cement sheet containing primary sludge.

Fig. 9. Scanning electron microscopy of control ber-cement sheet.

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R. Modolo et al. / Waste Management 31 (2011) 370377

Table 6
Primary sludge valorisation in ber-cement (costs/benets analysis).
Fiber-cement production

Standard

With primary sludge

Pulp (/t)
Pulp dry base (t/year)
Primary sludge dry base (t/year)
Moisture (%)
Pulp cost (/year)
Energy (/kWh)
Renement time (t/h)
Energy ()

585
600
0
NA
351.000,00

NA
450
150
30
263.250,00
0085
1,7
1.153,85
256,41
280
11.200,00
275.860,26

Distance (km)
Transport (/year)
Total costs (/year)
Benets (/year)

2,6
1.538,46
NA
NA
352.538,46
76.678,21

NA = Non applied.

Primary sludge includes in its composition almost 40% of inorganic solids, namely, sand. These inorganic charges increase the ber-cement sheet density in wet and dry state.
The bending moment values of quality product control are
between 55 and 71 Nm/m and load at rupture minimum acceptable value is 4655 N. According to the obtained results every
ber-cement sheet produced with primary sludge incorporation
presented acceptable values for both parameters on the nal product quality control (limits presented in Table 5).
To get additional information regarding the brous aspect of
these materials, surface samples of the produced ber-cement,
with and without sludge, were scratched, prepared and observed
by SEM (scanning electron microscope analysis).
Figs. 8 and 9 show the surface of both types of samples. They
present similarities in aspect and the viewed surfaces present large
amounts of bers as expected. Small particles of hydrated cement
matrix were clearly distinguished from the bers. The analysis
shows ber-cement surfaces containing bers arrangement. It
was not possible to distinguish Eucalyptus from Pinus bers by
SEM in the ber-cement matrix.
3.3. Evaluation of solution sustainability
In 2008, the average ber-cement production in this case-study
factory was estimated at 20,000 ton/year, consuming around
600 ton/year of VLFP. The costs associated to this cellulose-based
product amount were estimated in 350,000 /year (VLFP = 585 /
ton). By adopting this recycling solution, this ber-cement company saves around 87,500 /year on costs related to the virgin long
bers pulp purchase. The impact of the partial substitution of virgin
pulp by primary sludge in the matrix of ber-cement production
was estimated based on the pulp costs, sludge transportation and
energy costs related to renement process. Table 6 presents the values used in this assessment and the estimated results.
At the same time, this application allows to put in practice a
sustainable waste valorisation solution, avoiding disposal of
500 ton/year (150 ton/year in dry base) to waste landll, with an
estimated cost around 11,200 /year (based on a landll cost of
22.40 /ton).
The costs for the paper and pulp mill, related to this particular
waste disposal, must be replaced by waste transport to the bercement factory, which were estimated at 11200 /year. This value
was calculated using a base price of 0.08 /ton/km for waste transportation and admitting a total distance of 280 km in a two way
travel between the particular factories involved in this case study.
This waste valorisation represents an environmental solution
avoiding the waste landll. Even if the transportation costs were
supported by the ber-cement factory this waste valorisation
would present an economic benet solution.

4. Conclusions
It was possible to verify the incorporation of cellulose sludge in
this construction material, without affecting its general product
characteristics or its processing.
Replacing 25% of the long cellulose ber traditionally used by
primary sludge from efuent treatment allowed the production
of ber-cement sheets, with properties within the recommended
specications for the nal product.
The obtained values in water control does not indicate signicant alterations comparing them in terms of COD, chlorides, sulphates, dissolved salts and metals during the test period.
The 40% of inorganic charges present in primary cellulose
sludge promotes an increase on the ber-cement sheets wet density but, the results are within the acceptable limit value. The
bending moment and load at rupture for sheets with primary
sludge were also acceptable according to the nal product quality
control.
In summary, the substitution of conventional cellulose ber for
primary sludge from pulp and paper is a sustainable recycling and
valorisation solution without signicant impact on the ber-cement production, the nal product and in the environment. Furthermore, this waste valorisation not only presents an economic
benet around 87500 /year to the ber-cement factory but also
avoids the waste landll disposal for the paper and pulp company.
If the transportation cost is supported by the ber-cement company then its saving with this recycling solution will be around
76300 /year.
Acknowledgements
The authors would like to thank Cimianto - Sociedade Tcnica
de Hidrulica, SA, Forest and Research Institute RAIZ, Portucel/
Soporcel group for their help and contribution to this study.
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