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Research into using recycled waste paperresidues in construction products

WRAP Project code: PAP009-011

Written by:Dr. George Goroyias and Dr. Rob EliasThe BioComposites Centre, University of Wales Bangor

Dr. Mizi FanCentre for Timber Technology and Construction, Building Research

Establishment (BRE)

Published by:

The Waste & Resources Action Programme

The Old Academy, 21 Horse Fair, Banbury, Oxon OX16 0AHTel: 01295 819900 Fax: 01295 819911 www.wrap.org.ukWRAP Business Helpline: Freephone: 0808 100 2040

Date (published) June 2004

ISBN: 1-84405-106-4

Creating markets for recycled resources

R&D

Report:P

aper


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Research into using recycled waste paper residues in construction products 1

CONTENTS

CONTENTS........................................................................................................................................1

ABSTRACT........................................................................................................................................3EXECUTIVE SUMMARY................................................................................................................4

1. Introduction................................................................................................................................9

1.1 Scope and Objectives of the project ..........................................................................................9

1.2 Summary description of the project........................................................................................10

1.3 Project partners.........................................................................................................................11

1.4 Background ...............................................................................................................................11

2 Summary of work.....................................................................................................................12

2.1 Market review ...........................................................................................................................12

2.2 Sludge characterisation ............................................................................................................12

2.2.1 Chemical composition of sludge............................................................................................12

2.2.2 Fibre Length...........................................................................................................................13

2.3 Product development ................................................................................................................14

2.4 Non-load bearing softboard .....................................................................................................14

2.4.1 Product specifications ................................................................................................14

2.4.2 Product performance..................................................................................................15

2.4.3 Advantages.................................................................................................................16

2.4.4 Disadvantages ............................................................................................................16

2.4.5 Applications ...............................................................................................................16

2.4.6 Market opportunities..................................................................................................16

2.4.7 Manufacturing costs ...................................................................................................17

2.4.8 Further work...............................................................................................................182.5 Hybrid MDF..............................................................................................................................18



2.5.3 Advantages.................................................................................................................20

2.5.4 Disadvantages ............................................................................................................21

2.5.5 Applications ...............................................................................................................21



2.5.8 Further Work..............................................................................................................23

2.6 Cement bonded sludge board...................................................................................................24

2.6.1 Product specifications ................................................................................................242.6.2 Product performance..................................................................................................25

2.6.3 Advantages.................................................................................................................25

2.6.4 Disadvantages ............................................................................................................25

2.6.5 Applications ...............................................................................................................25



2.6.8 Further Work..............................................................................................................26

2.7 Tile ..............................................................................................................................................27



2.7.3 Advantages.................................................................................................................282.7.4 Disadvantages ............................................................................................................28


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2.7.5 Applications ...............................................................................................................28


2.7.7 Manufacturing Costs ..................................................................................................29

2.7.8 Future Work ...............................................................................................................29

2.8 Low density cement block ........................................................................................................29

2.8.1 Product specifications ................................................................................................292.8.2 Product performance..................................................................................................30

2.8.3 Advantages.................................................................................................................32

2.8.4 Disadvantages ............................................................................................................32

2.8.5 Applications ...............................................................................................................32



2.8.8 Future Work ...............................................................................................................33

2.9 Hardboard .................................................................................................................................33



2.9.3 Advantages.................................................................................................................352.9.4 Disadvantages ............................................................................................................35

2.9.5 Applications ...............................................................................................................35

2.9.6 Manufacturing cost ....................................................................................................35


2.9.8 Future Work ...............................................................................................................36

3 Consultation exercise ...............................................................................................................37

3.1 Summary of feedback ...............................................................................................................37

4 Conclusions...............................................................................................................................40

5 Recommendations for further work.......................................................................................41

6 References.................................................................................................................................42

APPENDIX I: Research & Patent Review ....................................................................................44

APPENDIX 2: Market review ........................................................................................................50

APPENDIX 3: Chemical Analysis .................................................................................................75

APPENDIX 4: Softboard ................................................................................................................82

APPENDIX 5: Hybrid MDF ...........................................................................................................94

APPENDIX 6: Cement bonded sludge board .............................................................................112

APPENDIX 7: Tile .........................................................................................................................125

APPENDIX 8: Low Density Concrete Blocks, ............................................................................129

APPENDIX 9: Hardboard ............................................................................................................158

APPENDIX 10: Consultation exercise .........................................................................................162

APPENDIX 11 Posters and Press releases...................................................................................180


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ABSTRACT

The Waste Resources Action Programme (WRAP) commissioned an integrated programme toexplore the feasibility of recycling paper mill waste residues as a raw material for the manufactureof novel construction products. This programme was to demonstrate the opportunities of recyclingwaste material to manufacture products that conform to European standard requirements andprovide prospective manufacturers with robust evidence of the technical capability of this wasteresource.The project partnership funded by the Waste Resources Action Programme (WRAP) was betweenthe Biocomposites Centre, University of Wales (BC, Project Managers) and the Building ResearchEstablishment (BRE).

This work has demonstrated that the recycling of paper mill residues into useful constructionproducts is feasible. Six new products were developed namely softboard, hybrid MDF, cementbonded sludge board, tile, low density cement blocks and hardboard. The waste papermill sludgefibre content varied from 2.5% to 85%.

The main advantage for potential technology/manufacturing partners is that in most cases acontinuous production process is proposed and has many economic advantages over batchprocesses. Reasonable production times have been achieved for each product and their basicstructural properties have been evaluated and compared against established products inaccordance to European standards.


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EXECUTIVE SUMMARY

The Waste Resources Action Programme (WRAP) commissioned an integrated programme toexplore the feasibility of recycling paper mill waste residues as a raw material for the manufactureof novel construction products.

In developing new products based on alternative materials there are a number of significantbarriers to be overcome. This project attempted to address the main issues in seeking tocommercialise and transfer a new technology. The principle issues addressed were performance,manufacturing and markets.

The aim of the programme was to demonstrate the technical and commercial feasibility ofrecycling a waste material to manufacture products that conformed to appropriate European

standards. The key steps in the development programme were designed to provide prospectivemanufacturers with robust evidence of the technical capability of this waste resource and provideinformation on the likely markets. In terms of a potential raw material the sludge has a number ofattractive attributes, it is easily available (a total of 1 million tonnes of papermill sludge aregenerated on an annual basis in the UK) and is of a relatively consistent composition.

The product development work focused on the chemical and physical characterisation of paper millwaste residues, process design, pilot scale manufacture of product prototypes and product testingand optimisation. Finally the success of the products was measured via a consultation exercise,which involved the organisation of a series of dissemination events inviting a wide audience from avariety of industry sectors to comment on the prototype products.

Six new products were developed namely softboard, hybrid MDF, cement bonded sludgeboard, tile, low-density cement blocks and hardboard. The waste paper mill sludge contentvaried from 2.5% to 85% showing that paper mill waste residues can be used in a wide range ofdifferent product applications. The technical characteristics, process of manufacture and marketopportunities of the products are presented in summary below: -

1. Softboard. Overview of production process

Raw materials: 80% sludge -10% MDF fibreAdhesive: 10 % Phenolic formaldehyde resinSurface lamination: Conventional wall paper or insulation waived aluminium foilBoard thickness: 10-45mmType of process of manufacture: Continuous

Manufacturing:-Significant capital investment is required for the production facilities. This isoffset by the fact that the main raw material for softboard is the paper mill sludge (80% plus

10% virgin fibre plus resin). If the sludge is supplied free of cost or at transportation cost therethen is a significant contribution to the overall material cost. Estimates of material cost for

Mixing Wet laying Drying Hot pressing LaminatingMixing Wet laying Drying Hot pressing Laminating


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virgin wood fibre (refined and dried) are 50-70/tone and resin cost 200-300 per tonne.Virigin wood fibre could be further substituted by reclaimed MDF fibres. This would result infurther savings and avoid the need for using any virgin material.

Performance: - conforms to the requirements of grade 3 (EN 316, EN 622) which is a softboardfor use in exterior conditions.

Market Opportunities-Three main markets exist, fibreboards to replace traditional low-densityvirgin fibreboards, prefabricated constructions and door/frame applications as an in-fill product.These markets in the UK have a combined value of 1756M.

2. Hybrid MDF. Overview of production process

Raw materials: 45% sludge and 40-45 % MDF fibre (40+35+15 =100%)Adhesive: 10-15 % (based on the dry weight of the mix) Phenolic formaldehyderesin or Melamine Urea formaldehyde resinSurface lamination/modification: as MDFBoard thickness: 10-25mmType of process of manufacture: Continuous

Manufacturing:- The process of manufacture is very similar to that of MDF and the productioncost is expected to be lower as a significant amount of virgin wood fibre is replaced. As over60% of the production cost of wood based panels is derived from the raw materials, this is

seen as a strong driver. Access to cheaper raw materials is therefore a key to supplying theneeds of the construction and furniture industries.

Performance: - The hybrid MDF product presented promising results in terms of bendingstrength and can be used in several applications in dry conditions where high internal bond isnot required. Improving the internal bond strength would create opportunities for the productfor other applications (i.e. furniture, doors etc.). The internal bond result 0.5 N/mm2was veryclose to the standard requirement standard MDF requirement (IB= 0.55 N/mm2).

Market Opportunities: - Main markets to consider are wood based panel products,prefabricated buildings, door/frames, frames for paintings and packaging with a total UKmarket value of 3372M. There are strong possibilities to utilise the product as a substrate inlaminated applications such as floor coverings and interior claddings. Further opportunities may

arise if a high-pressure door skin type product can be developed.

3. Cement bonded Particleboard. Overview of Production process

Refining-

blow line Drying Forming Pre-Press

Hot

Pressing Finishing

Refining-


Hot

Pressing Finishing

Refining-

blow lineDrying

Forming Pre-PressHot

Pressing FinishingMixing

Refining-

blow lineDrying




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Raw materials: 30% sludge- 70 % CementAdhesive: Not requiredSurface lamination/modification: As a normal cement bonded particleboardBoard thickness: 10-25mm

Type of process of manufacture: Continuous Manufacturing- The manufacturing cost for this product is expected to be lower than that of

its direct competitor, the conventional cement bonded particleboard. These savings are a resultof the substitution of cement by sludge.

Performance:- The cement bonded sludge board presented excellent test results withcomparable or even better properties than the standard requirement and therefore has realpotential for further development.

Market Opportunities: - Prefabricated structural components made with concrete or cement forwalls, floors and ceiling sections and artificial tiles have a total UK market value of 1564M.Development work has also indicated that a low-density product is achievable and this wouldsignificantly increase the market share.

4. Tile. Overview of Production process

Raw materials: 80-85% sludge based on dry weightAdhesive: 15-20% Isocyanates (MDI)Surface lamination/modification: Polyurethane, powder coating etc.Board thickness: 10-12mmType of process of manufacture: Continuous

Manufacturing: -The cost of the main raw material, which in this case is the sludge, isnegligible. Therefore the biggest raw material cost will be for the adhesive. Significant initial

investment is required for the commissioning of a new production line. Large pieces ofequipment such as continuous dryers, conti-roll or multi day light presses are required. Withthis investment the process will be continuous and large volumes can be produced efficiently.

Performance: - The tile has very good mechanical properties, high stiffness and gooddimensional stability. Further improvements could be achieved by developing improvedfinishing systems that will enhance the surface quality. A new test standard is also needed forthis hybrid product, as it is neither a wood nor a ceramic type product.

Market: The UK market value for the ceramic tiles and flags is 367M. This market is smallcompared to the construction applications but is niche. The product is easy to cut, looksnatural and is warm to the touch compared to ceramic products.

Refining Drying Forming Pre-Press

Hot

Pressing Finishing

Mechanical

BlendingRefining Drying Forming Pre-Press

Hot

Pressing Finishing

Mechanical

Blending


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5. Cement block. Overview of Production process

Raw materials: 95-97.5% cement aggregate mix and 2.5-5% sludge (dryweights)Adhesive: Not requiredSurface lamination/modification: Not required

Board thickness: Standard cement blockType of process of manufacture: Continuous

Manufacturing: - The introduction of 2.5-5% sludge can be achieved on existing productionlines without any significant modifications to plant and equipment. The biggest challenge atthis stage is to develop a compatiliser to improve the cement/sludge interaction increasingaddition levels at normal cure times.

Performance: - No significant decreases in material properties are observed when 5% sludge isadded to the mix. Therefore through the addition of sludge, low-density blocks can beproduced with the same mechanical performance.

Market Applications include building blocks, clay bricks and other plaster/concrete articles(ornamental goods) that is worth. 1417M in the UK. The ornamental goods market was

estimated at 114M alone and could be a commercial opportunity.

6. Hardboard. Overview of Production Process

Raw materials: 0-100% sludge plus 0-100% MDF fibre (dry weights)Adhesive: 1.5-2% Phenolic formaldehyde resinSurface lamination/modification: Resin impregnated paper can beapplied to enhance the stiffness of the board at high sludge contentsBoard thickness: 3-5mmType of process of manufacture: Continuous with prolonged pressing

Manufacturing -The addition of paper mill sludge fibre into an existing hardboard productionline is expected to result in considerable savings. Saving will be attributed to raw materials andrefiner energy. The degree of production savings is dependent upon the level of addition. Athigh levels of addition the incorporation of phenol formaldehyde resin will be necessary.

Performance: -Up to 20% addition levels can be achieved without any significant reduction in

bending and toughness. Higher addition levels can be obtained but there is a slight reductionin bending. However an improvement in the internal bond strength was observed

Press &

ConsolidateFilling Ejecting Steam curingMixingRefining Press &

ConsolidateFilling Ejecting Steam curingMixingRefining

Mixing Wet laying Hot pressingRefining Pre-PressMixing Wet laying Hot pressingRefining Pre-Press


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Market Applications: -High density fibreboards, wood based ornaments (letter, pen and inkstands with trays and wooden frames for pictures have a combined UK market value of 284M.Picture frame and draw backs are also good target end-uses.

Opportunities

This work has successfully demonstrated that it is technically possible to recycle paper millresidues into useful construction products. It has also indicated that there are significant marketopportunities and commercial benefits in using a lower cost material.

Ranking opportunities by market size suggests that the product with the biggest potential is thehybrid MDF followed by softboard and cement bonded particleboard. There are also opportunitiesfor building block materials but further technical developments are necessary. Good nicheapplications exist for the tile product and the hardboard substitute. However the lack of UKmanufacturing capability will hamper development. The product acceptance measured via a seriesof consultation exercises backs the view that there are good market opportunities and applications.

To move forward the development of manufacturing capacity and aim to bring products to marketa number of possible scenarios are envisaged, including: A commercial company uses the outcomes of the study to bring the products to market. The present project partners continue to develop the technology to further the

commercialisation of these products A company is set up comprising an industrial partner together with present project partners

with the aim of developing some or all of these products and taking them to market.


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1. Introduction

The use of recycled paper in the pulp and paper industry generates waste residues as a by-product from the process of recycling. These waste residues are currently disposed by methodssuch as landfill or land spread. The UK government has placed on top of the agenda as a priorityof highest importance, the minimisation of waste that is disposed of to landfill.

There are 78 operational papermills in the UK, which generate over 6 million tonnes of paper ofvarying grades and which utilise just over 5.5 million tonnes of recovered fibre each year. Thesludge produced as a by-product, totals just over 1 million tonnes per annum (typically screw-pressed at the mill and having a moisture content of 40-60%). The disposal of this sludgerepresents a significant disposal problem for mills.

To address these concerns the Waste Resources Action Programme (WRAP) commissioned anintegrated programme to explore the feasibility of recycling paper mill waste residues as a rawmaterial for the manufacture of novel construction products. This programme was to demonstratethe opportunities of recycling waste material to manufacture products that conform to Europeanstandard requirements and provide prospective manufacturers with robust evidence of thetechnical capability of this waste resource.

To find viable alternative options to the disposal of papermill sludge other than landfill or landspreading the project consisted of a combination of marketing and technical tasks. A market studyand discussion with industry aimed to identify six products that may be specified and taken

forward by industry into production. A series of technical development tasks were then undertakenincluding process design, process optimisation and product testing. Finally the success of theproject was measured via a consultation exercise, which involved the organisation of seriesdissemination events inviting a wide audience from a variety of industry sectors to comment onthe prototype products and to inform recommendations for further follow up action.

This project report outlines all the main project deliverables and findings. Detailed description ofthe research methodology, process and product development and performance assessments isgiven in the technical reports, which are presented as appendices.

1.1 Scope and Objectives of the project

The detailed objectives of the project are summarised below:

To provide the paper industry with a viable alternative to the disposal of papermill sludge vialandfill/landspread and identify technically and economically feasible alternatives with addedvalue end-uses.

To fast track market penetration and identify gaps in the product sectors which are worthy ofdevelopment.

Conduct market research to identify the requirements for new board products and potentialapplications in construction including floor tiles, mouldings, decorative trims, ceiling tiles andpartition panels.

Establish the requirements for product approval and map out alternative routes to market.Consultations with potential users, distributors and specifiers will be used to establish theirneeds.


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Develop raw material blends, designs and processes for the fast track development of 3product prototypes, review the requirements for product approval, and carry out relevantperformance assessments.

Develop raw material blends, designs and processes for remaining 3 products and carry outstructural tests and such other tests deemed necessary to demonstrate fitness for purpose.

All relevant testing to be applied according to BS EN or ISO standards where appropriate.

1.2 Summary description of the project

A number of development activities were undertaken in the project. An initial market review study(see 3.1) elucidated the market opportunities for the new products. Then a series of differenttechnical tasks were undertaken to determine:

Chemical and physical characterisation of paper mill waste residues Selection of six development products

Process design Pilot scale product manufacture Product testing Identification of tests performed to BS EN or ISO standards Consultation with potential stakeholders through the whole chain of custody to establish

the suitability of products developed.

A simple decision framework tool was used as a guide in the development process. The frameworkidentified key critical pathways and strategic deliverables. Key steps in the development processwere the successful completion of three critical paths, namely market review, process design (foreach of the six products) and product testing. Upon successful completion of each critical path,

three main deliverables were achieved, selection of product type, pilot scale manufacture, andproduct testing/process optimisation. The schematic below summarises the pathway used toachieve the critical paths and strategic deliverables:

Market review (Critical Path 1)

Product selection (Strategic Deliverable)

Process design (Critical Path 2)

Product manufacture (Strategic Deliverable)

Product testing (Critical Path 3)

Process optimisation and further product testing (Strategic Deliverable)

Figure 1: Project critical path analysis


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A final consultation exercise was undertaken with potential stakeholders through focus groupmeetings and dissemination exercises at exhibitions and conferences. The aim of these activitieswas to gather feedback on the products developed during the work programme and to identifyfuture commercial opportunities in addition to informing recommendations for further follow upactions.

1.3 Project partners

The project partnership funded by the Waste Resources Action Programme(WRAP) was between the Biocomposites Centre, University of Wales (BC, Project Managers) andthe Building Research Establishment (BRE). Raw materials were supplied from Bridgewater andShotton, which are two of the three mills in the UK producing newsprint, and Georgia Pacific(Devon) specialising in tissue production.

1.4 Background

A series of 6 products that utilise paper mill residues (sludge) as a base material for constructionmarket applications were identified and specified. The main focus of the work was on threeproducts (products 1 to 3) with some indicative work carried out on another three potentialproducts (products 4 to 6). These products were:

1. Non-load softboard2. Hybrid MDF3. Cement bonded sludge board4. Tile5. Low density cement blocks6. Hardboard

The next technical challenge was to design or establish a suitable manufacturing process for eachof the above product types. An extended literature review and patent search was conducted toassess the suitability of existing production technologies and to avoid any potential patentinfringements (see Appendix 1).

After a series of pilot plant trials the potential product methods were refined and the firstprototypes products made. For each product a review of the performance in accordance withrelevant EN standards was carried out and indicative testing conducted. The product assessmentexercise provided practical information that helped to modify the process variables in order toachieve a quality product in each case.


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2Summary of work

This section presents a summary of the findings of the market review study, the chemical and

physical characterisation of paper sludge, product development and product performance.

2.1 Market review

The market survey focussed on a review of the potential uses of papermill sludge in themanufacture of products of similar type to wood based panel products and in applications forflooring, ceiling, partitioning boards and as a lightweight aggregate in concrete blocks.The market review (see Appendix 2) presents data on the paper and board industry; the source ofthe papermill sludge, as well as recent trends in the production and consumption of wood-basedpanel products in the UK and Europe.

The conclusion of the market review study was that a number of products could potentially bemade using papermill sludge where the sludge forms the bulk of the new material or is simply anadditive to an existing product. The market study focused on the development of products for non-load bearing applications as these are more likely to be closer to market than full structuralproducts. The evaluation of surface quality, moisture resistance, ease of machining and working,fire resistance and screw holding ability are considered important properties

More demanding applications were explored during the project as the production technologiesused to manufacture the prototype materials improved and enhanced the mechanical properties ofthe materials.

Substitute products to replace wood based panels in general use as floor coverings have the most

promising market potential. Lightweight aggregate blocks, ceiling tiles and partitions are alsopromising markets.

2.2 Sludge characterisation

2.2.1 Chemical composition of sludge

A detailed analysis of the inorganic (filler) and fibre chemical composition (holocellulose; lignin)was carried out (See Appendix 3). Water and solvent extractives were obtained and theirchemistry investigated using FTIR (see table 1).


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Table 1: Chemical Analysis of papermill sludge

Inorganic material from each source of waste was analysed at two ashing temperatures and foundto vary widely in metal contents. The reason for the temperature dependent variation ofAluminium & Silicon is likely to be due to the breakdown behaviour of clay with certain metalsreleased at higher temperatures, see table 2.

Table 2: Analysis of inorganic constituents from Pulp Slurries.(All figures in parts per million = ppm)

2.2.2 Fibre Length

The fibre length was analysed using a Kajaani Fibrelength analyser.Typical average fibre lengths of 0.42 mm were found (See Appendix 3).

Analysis Pulp A Pulp B Pulp C

% Oven DryPulp Slurry

% Oven Dry PulpSlurry

% Oven Dry PulpSlurry

Moisture Content 65.84 78.60 83.02DichloromethaneExtractives

4.87 1.71 4.39

Toluene/IMS/Acetone Extractives

6.19 2.20 4.95

Hot water Solubles 3.75 3.51 4.80pH of above 8.30 8.60 8.40Ash 525C 52.61 66.35 53.90

Ash 900C 42.42 42.47 43.52Holocellulose 32.88 29.03 36.33Klason Lignin 14.61 9.91 19.30

Metal PulpSlurry

A

PulpSlurry

A

PulpSlurry

B

PulpSlurry

B

PulpSlurry

C

PulpSlurry

C

525C 900C 525C 900C 525C 900CAl 3451 23205 5436 19140 3574 20471Ca 6160 6172 3984 4296 6010 5678Cr 3 7 2 6 7 11Cu 8 78 10 58 9 92Fe 278 803 373 844 301 832K 211 693 94 162 248 762

Mg 867 1892 1378 2569 1200 2224Mn 32 39 54 60 40 47Na 392 1156 340 316 871 1360Ni 2 11 3 9 2 10P 8 81 9 54 8 95Pb 5 7 9 7 5 7Si 4133 38123 4949 26438 3501 35027Zn 8 20 14 21 108 23


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2.3 Product development

For each product a process flow diagram and the summary of testing results are presented. For

more detailed technical information such as process variables, additives, production parametersand so on, please refer to appendices 4, 5, 6, 7, 8 and 9.

The sludge was collected from Bridgewater Paper Company after having been processed using ascrew press to remove excessive water. The delivered sludge moisture content was typically 40-60%. The material was then processed according the flow diagrams presented separately for eachproduct in the following sections.

2.4 Non-load bearing softboard

The detailed technical development data for softboard are presented in appendix 4.

Picture 1: Softboard prototype panels

2.4.1 Product specifications

The product specifications are presented below in table 3:

Table 3: Softboard specifications

Softboard

Raw materials: 80% sludge -10% MDF fibreAdhesive: 10 % Phenolic formaldehyde resinSurface lamination: Conventional wall paper or insulation waived aluminium foilBoard thickness: 10-45mmType of process of manufacture: Continuous


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Process flow diagramThe flow diagram of the process of manufacture for softboard showing the main stages ofmanufacture is presented in figure 2.

Figure 2: Process flow diagram for softboard

2.4.2 Product performance

Softboard was compared against requirements of wood softboard according to the EN standardrequirements (EN 316, EN 622)for wood fibre softboard. The test results are presented in table 4.

Table 4: Test results of softboard and comparison against EU standard requirements

Properties of soft board Density (kg/m3) TS (%) MOR (N/mm2) MOE (N/mm2)

No. test pieces 48 48 36 36

Sludge soft board Property 358 5.4 1.3 31

cov (%) 19 7 5 6

Grade 1: SB >230 0.8 NR

Grade 2: SB.H >230 1 NR

Grade 3: SB.E >230 1.1 NR

Grade 4: SB.LS >230 1.1 >130

Grade 5: SB.HLS >230 1.2 >140

* TS = Thickness swell (after 2 hours cold water soaking)

% Cov= Coefficient of variation

MOR = Modulus of rupture

MOE = Modulus of elasticity

SB = Use in dry conditions

SB.H = Use in humid conditions

SB.E = Use in exterior conditions

SB.LS = Use for load-bearing in dry conditions

SB.HLS = Use for load-bearing in humid conditions.

NR = Not required

Mixing Wet laying Drying Hot pressing LaminatingMixing Wet laying Drying Hot pressing Laminating


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As it can be seen in table 4, the softboard conforms with the requirements of grade 3 which is asoftboard for use in exterior conditions. It is also important to mention that the softboard alsoconforms with grade 4 and 5 requirements excluding the MOE requirements, which could not bemet.

2.4.3 Advantages

One of the main advantages of the softboard is that it is made with 80% waste material. Thedisposal of paper waste residues (sludge) is a significant waste disposal operation for the paperindustry which is associated with high costs. If a if route for re-use can be established thatcould demonstrate that regular amounts of sludge could be utilised from a mill, the material maybe supplied at negligible cost. The cost of the raw material on that basis should be negligible andprobably will only reflect to transport costs.

The softboard in general has a good feel is very lightweight and has good resistance againstwetting. The high inorganic content (35-40 %) of the sludge should enhance the fire retardancyand the decay resistance against basidiomycetes and mould fungi. 1

A conventional type softboard is made utilising refined wood fibre and adhesives. The softboardthat was manufactured in this project contains 80% paper mill waste of which 40-60% (see table1) are inorganic compounds. It is hypothised that the high inorganic content of sludge softboardwill enhance its fire retardancy properties and in a fire test in a straight comparison with aconventional softboard should show superior performance. However, further work is needed toevaluate the later assumption.

2.4.4 Disadvantages

The biggest disadvantage of the softboard is its low bending strength. As a result the product isbrittle and not flexible. Consequently the softboard would require careful handling duringinstallation. The surface characteristics may cause difficulties during the surface lamination stage.However, the surface characteristics are improved through lamination, which also helps improvesome of the mechanical properties. The non-laminated product has a strong smell that of drysludge. This smell is reduced when a laminate is applied on the surface.

2.4.5 Applications

The main area of application is non-load bearing uses such as thermal/acoustic insulation, aceiling tile and in-fill product for timber frame construction.

2.4.6 Market opportunities1

The greater need for flexible use of space in buildings is driving the need for improved materialsin the movable partition-walling sector. New systems using a variety of different products arebeing developed that provide flexible accommodation and can be easily modified to adapt to the

1The EN standards that describe the methods for testing wood based products against fungal attack can be categorised into two

different types such as accelerated tests and field tests. Both methods assess the decay resistance of the product by measuring theweight loss after exposure to Basidiomycetesor mould fungi. The main difference between the accelerated and the field tests is thatfor the accelerated methods four months only are required to collect the results while in contrast many years of exposure in the soilare required for the field tests. However, the decay resistance of a product is normally evaluated by both tests. The accelerated lab

test is normally used to provide a quick indication of the decay resistance of a product while the field test method is an actualmeasurement of the natural durability of the product in decay conditions.1The UK net supply can be calculated as follows: UK net supply= UK Man. Sales + imports - exports


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changes in use in the building. The use of suspended ceiling light-weight systems will grow in thepublic sector through refurbishment in the education and health sectors. Softboard can play a rolein insulation and suspended ceiling applications and can also be used as an overlay for floors.

The existing market in these sectors is significant. Three main markets exist, fibreboards to

replace traditional low-density virgin fibreboards, prefabricated constructions and door/frameapplications as an in-fill product. These markets in the UK have a combined value of 1756M.

The markets on which insulation board could make a significant impact are presented below:

(Source: PRA 20200)Wooden or predominantly woodenprefabricated buildings, such as sheds,garages, greenhouses, conservatories,

holiday homes INCLUDING: -complete buildings fully assembled ready

for use - complete buildingsunassembled -incomplete buildings

having the essential character ofprefabricated building

UK Man. Sales Imports Exports

(M) (M) (M)508 11 17

(Source: PRA 20300)Doors and their frames and thresholds of

wood


(M) (M) (M)

672 172 24

(Source: PRA 20300)Table 5:UK market statistics for market opportunities for the softboard.

2.4.7 Manufacturing costs

Significant capital investment is required for the setting up of a softboard line with an in houserefining capability. The most energy demanding production stages are the refining and the drying.Board pressing can be done efficiently on a continuous basis. Energy savings can be achievedwith the utilisation of bio-fuels such as wood waste. The installation of bioenergy generators maybe proved a significant cost saving investment.

2UK Man. Sales = UK manufacturers sales

Fiberboard

UK Man. Sales2 Imports Exports

(M) (M) (M)

136 257 24


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The main raw material for softboard is the paper mill sludge (80%). If sludge were supplied freeof cost or at transportation cost, the remaining raw materials cost will be equal to that of thephenolic resin and the refined wood fibre. Refined wood fibre can be supplied to potentialsoftboard manufacturers by MDF industry or can be produced at the mill. The cost of refinedwood fibre per tone is equal with the cost of virgin wood plus the required energy and a profit

margin. On that basis the cost of refined MDF fibre per tone could be estimated at approximately50-70/tonne (as 40/tonne is the cost of the virgin wood).

As an alternative to refined MDF fibre, materials will soon be available that may be incorporatedinto the manufacturing process of softboard. Research scientists have been working ondeveloping a suitable process for the recovery of MDF fibre by recycling MDF furniture waste(such as DTI Research and Development projects, Fibersolve and Microrelease). These methodsare capable of recycling MDF back to MDF fibre which consequently could be utilised in themanufacturing process of softboard. These new developments open the potential for significantcost savings in the manufacturing of softboard. The refining stage could be avoided and therequired 10% of refined MDF fibre could be replaced with recovered MDF fibre. The recovered

MDF fibre could either be delivered on site or produced on site by recycling MDF furniture wasteusing the Fibresolve or Microrelease processes.3

2.4.8 Further work

This product has attracted much interest. The biggest issue is a scale up of the process as it is awet forming method. The areas for improvement include developing a fast drying process usingfor example, microwaves, high frequency drying (RF) etc. The bending strength of the productcould be improved by adding long fibres using renewable natural resources such as agriculturalplants (hemp, etc.) Longer fibres add reinforcement to the composite structure resulting in asignificant improvement of the bending properties of the product. Further work is need also to

look at optimisation of resin type and production of thicker products.

2.5 Hybrid MDF

The detailed technical development data for hybrid MDF are presented in appendix 5.

a.

3Fibersolveprocess is capable to recycle MDF furniture waste back to MDF fibre. This process has been fully scaled up and a 2-tone reactor has been

successfully commissioned. The process is economical as only one hour and low pressure as 2 bar is required for a complete batch cycle. The quality ofthe fibre and panels produced in pilot scale using recycled MDF fibre was of equal quality to that of commercial MDF.Microreleaseprocess is still under development and involves the use of microwaves to breakdown MDF into single fibres. Microrelease is in principlea faster method compared to Fibersolvebut further development work is in required to evaluate the efficiency of the process in bigger scale.


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b.

Picture 2: Hybrid MDF prototype panelsa.) router profiled hybrid MDF and b.) laminated hybrid MDF



Hybrid MDF

Raw materials: 45% sludge and 40-45 % MDF fibre (40+35+15 =100%)Adhesive: 10-15 % (based on the dry weight of the mix) Phenolic formaldehyderesin or Melamine Urea formaldehyde resinSurface lamination/modification: as MDFBoard thickness: 10-25mmType of process of manufacture: Continuous

Table 6: Hybrid MDF specifications

Process flow diagramThe flow diagram of the process of manufacture for hybrid MDF showing the main stages ofmanufacture is presented in figure 3.

Figure 3: Process flow diagram for hybrid MDF


Hybrid MDF was compared against the European requirements of MDF grades according to EN

316. The test results are presented in table 6.

Refining-


Hot

Pressing Finishing

Refining-


Hot

Pressing Finishing


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Properties of hybrid MDF

Density (kg/m3) TS (%)IB

(N/mm2)MOR

(N/mm2)MOE

(N/mm2)

No. test pieces 48 48 48 36 36

Property 995 11.8 0.5 26.1 2892Hybrid MDF

cov (%) 1.5 7.1 18.1 10.6 10.5

Property 884 9.2 1.2 43.4 2364Control MDF

cov (%) 8 2.6 9.7 2.4 2.7

MDF >600 12 0.55 20 2200

MDF.H >600 8 0.75 24 2400

MDF.LS >600 12 0.6 25 2500

MDF.HLS

**

>600 8 0.75 30 2700

*TS = Thickness swell (after 24 hours cold water soaking)** for humid uses MDF needs to be tested against a cyclic swelling test.% Cov = coefficient of variationMOR = Modulus of rupture


IB = Internal bond strength

MDF = Use in dry conditions

MDF.H = Use in humid conditions

MDF.LS = Use for load-bearing in dry conditions

MDF.HLS = Use for load-bearing in humid conditions.

Table 7. Test results of hybrid MDF and comparisons against European standard requirements

The hybrid MDF product presented promising results in terms of bending strength and can beused in several applications in dry conditions where high internal bond strength is not required.Improving the internal bond strength would create opportunities for the product for otherapplications (i.e. furniture, doors etc.). The internal bond result 0.5 N/mm2was very close to thestandard MDF requirement (IB= 0.55 N/mm2).

2.5.3 Advantages

This product has good mechanical properties such as stiffness and combined with promisingdecay and fire resistance properties could be targeted towards high-added product value markets.


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In general the product has normal density and it is not heavy in comparison to standard MDF.The surface quality is acceptable. The product has good machinability i.e. router produced a goodquality profile (Picture 2a).

The high inorganic content in the sludge could hide some special characteristics, which are

required from the product for new finishing technologies.

Finally it could substitute virgin wood in conventional MDF production with significant costsavings. However, further work is needed to exploit this potential.

2.5.4 Disadvantages

This product needs some further optimisation. The high fines content produces a mat with veryhigh compaction capacity, which is difficult to hot press. High resin contents were used in orderto achieve good internal bond strengths, but add to the production cost. The fines also contributeto the pre-curing process on the surface increasing any sanding tolerances, and making sanding

more difficult.

2.5.5 Applications

General purpose (Upholstery furniture, wall sheathing, floor covering, packaging, etc.) orlaminated furniture components.


The process of manufacture is very similar to that of MDF. However, the cost of manufacture isexpected to be lower to that of MDF because significant amount of wood fibre is replaced with

paper mill sludge. The most energy demanding manufacturing stage is the refining of the wood.If conventional adhesives systems were incorporated then the cost of the adhesive would be atthe current market rates for phenolic formaldehyde resin, melamine formaldehyde resin orisocyanates. However, it is more likely that a specially designed adhesive system needs to bedeveloped which is capable of binding organic and inorganic materials and in this case the cost isunknown.

Existing manufacturers of wood based panel products are competing in a tough market whereoversupply and cost are the major market forces. Over 60% of the production cost of woodbased panels is dedicated to the raw materials used to manufacture the product (wood andresin). Access to cheaper suitable raw materials is therefore key to supplying the construction and

furniture industries.

2.5.7 Market opportunities

The main markets to consider are wood based panel products, prefabricated buildings,door/frames, frames for paintings and packaging with a total UK market value of 3372M (table8).

Figures from Panelboard Industry Trade Association: (2003) the turnover of the industry isapproximately 550million, with 8 manufacturing facilities based in the UK.There are strong possibilities of utilising the product as a substrate in laminated applications such

as floor coverings and interior claddings. Further opportunities may arise if a high-pressure doorskin type product could be developed.


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Cases, boxes, crates, drums and similarwood packaging EXCLUDING: - cable

drums


(M) (M) (M)

95 7 3(source: PRA 20400)

Box pallets and load boards of woodEXCLUDING: - flat pallets


(M) (M) (M)

16 4 4

(source: PRA 20400)Flat pallets and pallet collars of wood


(M) (M) (M)

266 82 64(source: PRA 20400)

Wooden frames for paintings,photographs, mirrors or similar objects


(M) (M) (M)

160 5 21

(source: PRA 20510)

(source: PRA 20200)

Plywood


(M) (M) (M)

78 297 17(source: PRA 20200)

Chipboard


(M) (M) (M)

435 171 31

(source: PRA 20200)

Fiberboard


(M) (M) (M)

136 257 24


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Wooden or predominantly woodenprefabricated buildings, such as sheds,garages, greenhouses, conservatories,

holiday homes INCLUDING: -complete buildings fully assembled ready

for use - complete buildingsunassembled - incomplete

buildings having the essential characterof prefabricated building


(M) (M) (M)

508 11 17

(source: PRA 20300)Doors and their frames and thresholds of

wood

UK Man. Sales Imports Exports(M) (M) (M)

672 172 24

Table 8: UK market statistics for hybrid MDF

2.5.8 Further Work

Further work is necessary to optimise blow line blending as the geometry of the sludge fibre isvery different to that of virgin wood fibre. A double refining system could potentially producemuch more compatible fibres. Other blending methods such as mechanical blending need to be

investigated.

Producing a three-layered MDF type product with a wood fibre core layer and a sludge surfacecould enhance the structural properties. Fines could also be removed and separated from thesludge before use to yield an improved furnish (furnish is the fibre plus any other additives in theform of a mat before pressing). The fines could be then utilised for the development of a surfacemodifier that would improve the aesthetics of the product and add value. Different resin typesshould be investigated i.e. MDI (Methylene, diphenyl, diisocyanate) and screened to see if thereare any effects on reactivity.

Another alternative raw material that could be utilised in the manufacture of MDF and in

combination with paper mill waste is recovered wood. Recovered wood waste can be separated intwo major categories such as: untreated (e.g. packaging) which is relatively clean ofcontaminants and treated (e.g. demolition wood waste) which can be heavily contaminated withmetals, paint, wood preservatives. Further development work is needed to allow the use ofrecovered wood in MDF production. Recycled wood can be heavily contaminated with metals andeven after extensive cleaning using the PAL systems (brand name of a sophisticated cleaningprocess), the metal content remains an issue for the refining stage. However, it is important tonote that the MDF industry is looking forward to accessing cheaper raw materials in order toreduce manufacturing costs and the utilisation of waste materials such as paper mill sludge andrecycled wood would enable the industry to achieve significant savings and improve theenvironmental profile of their products.


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2.6 Cement bonded sludge board

The detailed technical development data for cement bonded sludge board are presented inappendix 6.

Picture 3: Cement bonded sludge board



Table 9: Cement bonded particleboard specifications

Process flow diagramThe flow diagram of the process of manufacture for cement bonded sludge board showing themain stages of manufacture is presented in figure 4.

Refining-

blow line Drying



Refining-

blow line Drying



Figure 4: Process flow diagram for cement bonded sludge board

Cement bonded sludge board

Raw materials: 30% sludge- 70 % CementAdhesive: Not requiredSurface lamination/modification: As a normal cement bonded particleboardBoard thickness: 10-25mmType of process of manufacture: Continuous


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Cement bonded sludge board was compared against the European requirements of theconventional cement bonded particleboard according to EN 634. The test results are presented intable 10.

Table 10: Test results of cement bonded sludge board and comparisons against European standardrequirements

The cement bonded sludge board presented excellent test results with comparable or even better

properties than the standard requirement and therefore presents real potential for furtherdevelopment.

2.6.3 Advantages

Key advantages of this product are strength, fire resistance and dimensional stability. Thesecharacteristics combined with decay resistance performance make this product a candidate forexterior applications in addition to interior applications

2.6.4 Disadvantages

High density products and the slow production times may raise concerns for manufacturers.There is not a big established market for cement bonded particleboard in UK and Europe andalthough it has competitive properties it is difficult to compete against lower density productssuch as Orientated Strand Board (OSB) which have dominated the construction market.

2.6.5 Applications

Much interest has been expressed for this product with applications suggested for exteriorcladding, outdoor paving systems and suggestion for niche applications as fire surrounds.

Properties of cement bonded sludge boards

Density(kg/m3)

TS (%) IB (N/mm2)MOR

(N/mm2)MOE

(N/mm2)TS (%)AF321

IB(N/mm2)AF321

No. test pieces 48 48 48 36 36 48 48

Property 1618 0.8 1 11.9 10882 0.58 0.37Cement sludgeboard cov (%) 5.8 12.5 7.3 15.8 19.3 21 7.2

CBPB requirements >1000 0.5 >9 4000- 4500 0.3

* TS = Thickness swell (after 24 hours cold water soaking)MOR = Modulus of rupture


AF321 = After cyclic test

CBPB = Conventional cement bonded particleboard


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Cement bonded sludge board as cement bonded particleboard may find itself a specialised nichein the market that reflects its outstanding merits of high stiffness, high durability, good protectionagainst fire and high sound insulation. There is widespread use for cement bonded particleboard

as a wall lining in public buildings, as well as a cladding material. More specialised uses embraceflooring (where there is a risk from water spillage), sound insulation and construction ofprotective elements for fireproofing.

Prefabricated structural components made with concrete or cement for walls, floors and ceilingsections and artificial tiles have a total UK market value of 1564M (table 11). Development workhas also indicated that a low-density product is achievable and this would significantly increasethe market share.

Prefabricated structural components(concrete, cement, or artificial stones,walls, floors or ceiling sections etc.)


(M) (M) (M)

426 5 12(Source: PRA 26100)

Plaster Products for Constructionpurposes1

UK man. sales Imports Exports

(M) (M) (M)

351 14 131333M for boards, sheets, panels, tiles and similar articles of plaster or of compositions based on plaster, faced or reinforced with

paper or paperboard only EXCLUDING: - articles agglomerated with plaster ornamented.

(Source: PRA 26620)Tiles

(Cement, concrete, artificial stone)


(M) (M) (M)

740 42 10(Source: PRA 26100)

Table 11: Market statistics for cement bonded sludgeboard


The manufacturing cost for this product is expected to be lower than that of its direct competitor,the conventional cement bonded particleboard because there will be significant productionsavings by the substitution of wood particles with sludge and faster production. The most energydemanding production stage is the pressing. The cost of raw materials isequivalent to the cost ofcement plus the cost of water.

2.6.8 Further Work

Improvement to develop lighter weight designs is needed along with faster production processes.

This could be achieved with the use of accelerators. A range of tests are needed to evaluate theeffect of sludge chemical compounds on the reactivity of a range of resin systems.


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2.7 Tile

The detailed technical development data for the tile is presented in appendix 7.

Picture 4: Prototype tile products (Tile is top product sitting on a laminated hybrid MDF)



Table 12: Tile specifications

Process flow diagramThe flow diagram of the process of manufacture for the tile showing the main stages ofmanufacture is presented in figure 5.

Figure 5: Process flow diagram for cement bonded sludge board

Tile

Raw materials: 80-85% sludge based on dry weightAdhesive: 15-20% Isocyanates (MDI)Surface lamination/modification: Polyurethane, powder coating etc.

Board thickness: 10-12mmType of process of manufacture: Continuous

Refining Drying Forming Pre-Press

Hot

Pressing Finishing

Mechanical

BlendingRefining Drying Forming Pre-Press

Hot

Pressing Finishing

Mechanical

Blending


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The performance of the board material developed as the substrate for tiles was assessed againstEuropean standards for fibreboards (EN 316). However based on this scenario and because thetile is made using 20% MDI resin it becomes an expensive alternative to conventional fibreboards

where lower amounts and more cost effective resins are normally applied. Further developmentwork is required to shift the tile properties from its current grade to the more demanding gradesof ceramic tiles.

Tile

Density: 1200-1300 kg/m3

Thickness swelling: 3-5%

MOR: 20-30 N/mm2

MOE: 2000-4000 N/mm2

Table 13: Results of tile testing

In general the properties of the board panel produced as the substrate material for tiles wereacceptable in terms of strength.

2.7.3 Advantages

This alternative non ceramic tile type product is warm to the touch and has good mechanicalproperties whilst consisting of 80-85% waste material. It can be cut easily using conventionalelectric saws without the need for special tile cutters and has good resistance to wetting prior tosurface and edge covering.

2.7.4 Disadvantages

To achieve the strength and hard wearing characteristics the product has a high MDI resincontent. The surface of the product is absorbent and affects how the product is finished(laminated, painted, coated) especially if a wet system is applied on the surface.

2.7.5 Applications

Floor covering and wall tiling system for interior use in dry environments


The UK market value for the ceramic tiles and flags is 367M. This is a small niche market. Theproduct is easy to cut, looks natural and is warm to the touch compared to ceramic products.

Ceramic Tiles & Flags


(M) (M) (M)

85 282 18

(PRA 26300)Table 14: Market statistics for ceramic tiles


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2.7.7 Manufacturing Costs

Further process development is required to develop a more efficient method of fibre separation(fluffing up the sludge). In this project, the refiner was used as a method to model a system for

fibre separation. As the refining stage is the most energy demanding production stage analternative and more energy efficient method is required to separate the fibres at lower cost. Thiscould be achieved by modification of existing refining technology or by the design of a newprocessing capability e.g. separation of the fibre using a sophisticated drying system incorporatingaerodynamics and physics in the design or through the development of separation techniques tosplit the sludge fibre from the filler elements.

The cost of the main raw material, which in this case is the sludge, is negligible. Therefore thebiggest raw material cost will be for the adhesive. However, significant initial investment isrequired for the commissioning of a new production line. Large pieces of equipment such ascontinuous dryers, conti-roll presses or multi day light presses are required to ensure maximum

use of the production time. The process is continuous and large volumes could be producedefficiently, with the appropriate infrastructure.

2.7.8 Future Work

Work needs to identify cheaper alternative resin systems and overcome the surface finishingproblems. A better study of the surface wear characteristics is also needed to ensure that the tilewill have a life span of 5 plus years in exterior conditions. This could be achieved by improvingthe resin distribution and using specially designed resins that have adhesive properties withorganics and inorganics.

2.8 Low density cement block

Picture 5: Low density sludge-cement blocks

The detailed technical development data for low density cement blocks are presented in adetailed technical report in appendix 7.




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Light density cement block

Raw materials: 95-97.5% cement aggregate mix2.5-5% sludge (dryweights)Adhesive: Not requiredSurface lamination/modification: Not required

Board thickness: Standard cement blockType of process of manufacture: Continuous

Table 15: Tile specifications

Process flow diagramThe flow diagram of the process of manufacture for the light density cement blocks showing themain stages of manufacture is presented in figure 6.

Press &

ConsolidateFilling Ejecting Steam curingMixingRefining Press &

ConsolidateFilling Ejecting Steam curingMixingRefining

Figure 6: Process flow diagram for l ight density cement blocks


A series of mechanical and physical tests were carried out with the aim to evaluate the suitabilityof paper sludge as a density reduction agent in conventional cement block manufacture.Examples of test results are presented in figures 7, 8 and 9. More technical information on testsand testing results is presented in appendix 7.

Figure 7: Compressive cube crushing strength versus curing period.A significant reduction of compressive cube crushing strength was found at 2.5% and 5% sludge mixes.


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Figure 8: Relative block (cube) crushing strength versus curing period.No significant effect was found on the relative crushing strength.

Figure 9: Block density versus sludge content. The effect of 2.5% and 5% of sludge on block density isremarkable. The density was reduced dramatically by adding 5% sludge in the mix.

It is difficult to say whether the observed effects would result in a problem on a block productionline without an actual trial. However the retardation effect is minimal if present at all. Furtherwork is required to evaluate the practicality of this combination. The market potential forlightweight aggregate blocks could be improved if further work is done on pre-treatment of thesludge. If a cost effective method of separation of fibre from fillers is used, and a higherproportion of clays, inorganic material (filler residue) is utilised, the resulting block would havebetter strength qualities. However, if a refined sludge containing a higher proportion ofseparated fines in relation to paper fibres were used then both the density and the strength of

modified concrete block products would be increased relative to products made with the straightdried sludge.


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2.8.3 Advantages

The addition of sludge to building blocks helps reduce product density and can save 2.5% cost inraw materials. The production of lighter weight products and a reduction in concrete consumption

are key drivers for the construction industry

2.8.4 Disadvantages

The major disadvantage of the addition of sludge is a corresponding increase of production timeto cure the products. This is seen as a major disadvantage by the industry. Low weight concreteblocks are usually deliberately semi-compacted and made with gap-graded aggregates tointroduce porosity so the additional porosity resulting from the sludge addition is not a problem initself.

2.8.5 Applications

General purpose building blocks for construction


The addition of 2.5 to 5% of sludge can be done without any significant alteration in an existingproduction line. The biggest challenge at this stage is to develop a compatiliser to improve thecompatibility of cement and sludge.


Market Applications include building blocks, clay bricks and other plaster/concrete articles(ornamental goods) that are worth 1417M in the UK (table 16). The ornamental good marketwas estimated at 114M alone and could be a good niche application for sludge based products.

Building blocks(Cement, concrete, artificial stone)


(M) (M) (M)

594 17 4

(Source: PRA 26100)

Tiles(Cement, concrete, artificial stone)


(M) (M) (M)

740 42 10(Source: PRA 26100)

Other Articles of Concrete, Plaster &Cement1


(M) (M) (M)

105 9 20


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140M for Articles of plaster or compositions based on plaster for non-constructional purposes INCLUDING: - casts, statues, bowls, vases andornamental goods EXCLUDING: - plaster-coated fracture bandages put up for retail sale and plaster fracture splints - models designed solely fordemonstrational purposes - tailors dummies, 60M for Articles of cement, concrete or artificial stone for non-constructional purposes INCLUDING: -vases, flower pots architectural or garden ornaments, statues and ornamental goods

(Source: PRA 26660)Table 16: UK market statistics for building blocks

2.8.8 Future Work

Development of a compatiliser(an additive that would improve the compatibility of sludge andcement) to allow faster curing and allow a higher sludge content is key for commercialapplications of sludge materials in this product sector.

2.9 Hardboard

The detailed technical development data for hardboard are presented in an analytical technicalreport in appendix 8.

Picture 6: Example of hardboard made using various amounts of sludge.



Hardboard

Raw materials: 0-100% sludge plus 0-100% MDF fibre (dry weights)Adhesive: 1.5-2% Phenolic formaldehyde resinSurface lamination/modification: Resin impregnated paper can beapplied to enhance the stiffness of the board at high sludge contentsBoard thickness: 3-5mmType of process of manufacture: Continuous with prolonged pressing

Table 17: Hardboard specifications

Process flow diagram

The flow diagram of the hardboard production process indicating the main stages ofmanufacturing is presented in figure 10.


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Figure 10: Process flow diagram for hardboard


A series of hardboard samples were made incorporating various amounts of de-inking sludge.The bending properties and internal bond strength were measured.

0

0.1

0.2

0.3

0.4

0.5

0.6

modulusofrupturekPa

0

0.05

0.1

0.15

0.2

0.25

0.3

worktopeakload

0 20 40 60 80 100% sludge

bending strength toughness

Bending strength and toughness

Figure 11: Bending strength and toughness versus sludge percentage.

It is evident that there is an effect on bending strength and toughness with increased additions ofsludge. The most likely reason for this observation is due to the shorter fibres present in thesludge materials.

0

0.05

0.1

0.15

internalbondMPa

0 20 40 60 80 100% sludge

Internal bond strength

Figure 12: Internal bond strength versus sludge content.

Mixing Wet laying Hot pressingRefining Pre-PressMixing Wet laying Hot pressingRefining Pre-Press


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The internal bond (IB) shows almost the opposite behaviour to the bending strength, perhapsexplaining why small amounts of sludge have little effect on bending strength. The increase in IBcould be explained by the greater compaction level of the sludge material that enables more fibreto fibre interactions.

It was concluded that the sludge can be incorporated into the hardboard in high proportions,having little effect on the mechanical properties of the product. Key to maintaining themechanical properties of the hardboard is ensuring that sufficient water is removed from themattress in the pre-press stage of the production process. Further work is required to evaluate ifa 100% sludge based hardboard cab be made with the addition of several types of adhesives.

2.9.3 Advantages

Up to 40% reduction and saving in virgin raw materials can be achieved by substituting sludge forwood in hardboard products. The substitution of wood fibre with paper mill waste will result insignificant energy savings at the refining stage as lower volumes of solid wood will have to be

refined.

2.9.4 Disadvantages

The environmental issues of using a water intensive process are a concern. The product is used inlow cost applications and is commodity driven. There is a limited production capability in UK.

2.9.5 Applications

The sludge hardboard is a direct replacement for hardboard and has potential for use in hobbyapplications (picture backs), as a backing material in the furniture industry (drawer bottoms andunder-lays for floors)

2.9.6 Manufacturing cost

The addition of paper mill sludge fibre in an existing production line is expected to result inconsiderable savings in raw materials cost and refiner energy. The degree of production savingsis depended upon the level of addition. At high levels of addition the incorporation of phenolformaldehyde resin will be necessary. However, even in this case it is expected that the savingsthat can be achieved by the replacement of wood fibre with sludge will overcome the cost ofresin.


High density fibreboards, wood based ornaments (letter, pen and ink stands with trays andwooden frames for pictures have a combined UK market value of 284M. Picture frame and drawbacks are also good target end-uses.

(Source: PRA 20200)

Wood marquetry and inlaid wood; casketsand cases for jewellery or cutlery, and

Hardboard


(M) (M) (M)

45 23 25


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similar articles, statuettes andother ornaments, coat or hat racks, officeletter trays, ash trays, pen-trays and ink

stands of wood


(M) (M) (M)

6 41 5(Source: PRA 20510)

Wooden frames for paintings, photographs,mirrors or similar objects


(M) (M) (M)

160 5 21

(Source: PRA 20510)Table 18: UK market for hardboard type products

2.9.8 Future Work

Further work could look at combining recovered MDF waste with an aim to increase the amountof sludge added to the product. A good target for future development would be to optimise theprocess for thicker board for a construction grade product. A series of resin trials would also helpto achieve a higher quality product.


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3Consultation exercise

A series of dissemination events were undertaken. The aims of the events were to gather

feedback on the products and gauge commercial industrial interest.

The dissemination events consisted of two principle activities: attendance at tradeshows/conferences and focus group meetings.

The project team attended two trade shows and organised three focus group meetings. A fourthfocus group meeting will be organised after the final completion of the project with the aim toattract industrial interest and support for the next phase.

The first trade show attended was the 7thEuropean Panel Products Symposium (October 2003).At this even, a poster summarising the project and some product prototypes were exhibited to UK

and other European wood based panels stakeholders. The second show was at the PaperIndustries Technical Association (PITA) annual conference (March 2004). This was stronglyattended by the paper industry with over 140 delegates from mill and equipment suppliers.Samples of all 6 products were made available for inspection along with information on theirtechnical performance and feedback was gathered from both.

The three focus group meetings took place in conjunction with other events. The first focus groupmeeting was organised during the technical committee meeting of the Wood Panel IndustriesFederation which was held at BRE in December 2003. The second focus group meeting was partof the activities of the European Cost Action E29 Timber products innovation (February 2004).Twenty-five participants from various countries around Europe were invited to answer questions

and identify the key opportunities and barriers for adopting these technologies. The third focusgroup meeting took place at the PITA conference (March 2004). Key stakeholders from paperindustry were identified and interviewed in person.

Board manufacturers, resin suppliers, product specifies, researchers, architects, civil engineers,technologists, technical managers, production managers were amongst those asked to answerquestions and give their informed opinion on the six new products. The feedback was collected inthe form of questionnaires. The assessment of the questionnaires was completed using simplestatistical analysis. A detailed report of the dissemination events is presented in appendix 10.A final facilitated focus group meeting was held on the 5thof May at BRE Garston, Watford.

3.1 Summary of feedback

The consultation exercise provided very useful information on key areas for each of the products,such as product applications and the best candidates for further development.

Stakeholders were asked to give their opinion on product appearance, environmental profile,strength, extra properties required and suggested applications. In brief the product winners werethe softboard, the tile and the cement bonded sludge board (figure 13).

The hybrid MDF however attracted a lot of interest. However, the general opinion was that as thewood based panels sector is very competitive there would be a number of barriers to exploiting

this technology. New technologies that can be used to recycle MDF fibre are now very close tomarket. These technologies could potentially provide an alternative source of wood fibre by


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recycling furniture waste which could be incorporated as an alternative type to wood fibre intothe hybrid MDF product. This potential combination is worth exploring in future projects.

Several applications were suggested for the new products (figure 14). The top four were flooring,tiles, insulation and furniture. A more detailed description of the consultation exercise feedback is

presented in appendix 10.

What do you like?

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Insulation

Board

MDF type Cement

Bonded Board

Tiles Cement

Blocks

Hardboard

Percen

tage Other

AppearanceEnvironmental Profile

Strength

Figure 13: Ranking of product characteristics

0

5

10

15

20

25

floor

covering

tiles

insulatio

nthermal

furnitu

re

generalp

anels

inne

rlinings

forstu

dwallin

g

blocks

ceilin

gs

wallc

overings

cladding

pavin

gsystem

s

acou

sticinsulatio

ndoors

roofs

pe

rcentage

responses

Figure 14: Suggested applications for the six products


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Discussions were very positive with inputs from all the attendees. General technical issues raised revolved aroundproduct performance such as fire and thermal properties.

The consensus was that if the products achieved the standards, there were no envisaged barriers to adoption withthe exception of cost.

The lack of practical experience of using the products and lack of incentives to change (e.g. legislation) were seenas critical commercial barriers.

To overcome these barriers partnerships with prominent retail companies were thought to be necessary.

The ability to be able to purchase the products was also seen as a critical step in commercialisation.

The trend toward offsite construction is seen as a significant market driver for future materials. Here, the use ofthe products in a system that combines 1 or 2 materials will be important.

In summary supply chains, routes to market and the ability to demonstrate t

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