wood waste derived fuel: state of the art ...471435/...wood wastes derived fuel 4 acknowledgements...

WOOD WASTE DERIVED FUEL: STATE OF THE ART AND DEVELOPMENT

PROSPECTS IN FRANCEFOCUS ON CONSTRUCTION

AND DEMOLITION WOOD WASTES

C h a r l o t t e R i z z o

Master of Science ThesisStockholm 2010

Charlotte Rizzo

Master of Science ThesisSTOCKHOLM 2010

WOOD WASTE DERIVED FUEL: STATE OF THE ART AND DEVELOPMENT PROSPECTS IN FRANCE

FOCUS ON CONSTRUCTION AND DEMOLITION WOOD WASTES

PRESENTED AT

INDUSTRIAL ECOLOGY ROYAL INSTITUTE OF TECHNOLOGY

Supervisor & Examiner:

Monika Olsson

TRITA-IM 2010:34 ISSN 1402-7615 Industrial Ecology, Royal Institute of Technology www.ima.kth.se

Wood wastes derived fuel

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Abstract

Wood wastes are mainly originated from forestry, wood industry and construction and demolition sites activities. Among them, three types of wood waste can be identified: untreated wood waste (raw wood considered as biomass), slightly treated wood wastes (issued from coating or gluing treatments) and highly treated wood wastes (issued from impregnation treatments with CCA and creosote, and considered as hazardous wastes).

According to the regulation, management of wastes in Europe is oriented towards more recycling and less elimination. However, among the French requirements, three main trends can be observed in regards of wood waste recovery: only treated wood wastes can be recovered in combustion units, no extensive technologies are allowed to recover highly treated wood wastes, which must then be eliminated by incineration, and slightly treated wood wastes can be either recovered as particle boards or eliminated.

However, in this context, the amount of wood wastes from construction and demolition sites reach 7 million of tons in France. Among them, 5% correspond to raw wood, and 25% are slightly treated. The high combustion potential of wood wastes is moreover an opportunity to replace conventional fuel used in combustion units.

The four main methods used to treat wood wastes are recycling as particleboards, combustion, incineration and land filling. Due to the various typologies of wood wastes, a conditioning step is needed before recovery. Then, if combustion seems to present advantages because of its neutral carbon impact, life cycle analysis demonstrates that emissions of other pollutants are observed. In addition, it is proved that controlled elimination methods are less impacting than unequipped recovery ones. Recycling is then not always the best practice in regards of the impacts considered in the study.

Competition among the different methods treatment and low prices of wood wastes are specific economical aspects that could influence the development of the field. Moreover, the increasing acceptance of people for recovery and local waste treatment methods, as well as the need for energetically independency are factors that can likely promote wood waste derived fuel.

These driving forces are evolving in a very rapid way. Regulation is moving towards implementation of standards to promote the development of slightly treated wood waste derived fuel. Technological and social improvement such as sorting at source, and the development of end of pipe treatment methods are also likely to have positive effects.

An integrated solution to develop wood waste derived fuel would be to implement strong financial incentives in favour of clean technologies for wood wastes recovery methods. This enhancement could then be the mean to answer the double challenge of wood waste treatment and fossil fuel replacement.

Key words: Waste management – Construction and demolition wastes – wood wastes – biomass – combustion –life cycle assessment


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Sammanfattning

Träavfall kommer från skogsbruk, trä‐ och byggbranschen och rivningsplatser. Bland dem kan tre typer av träavfall identifieras: obehandlat träavfall (obehandlat trä betraktas som biomassa), lätt behandlat träavfall (från beläggning eller limning) och högbehandlat träavfall (från impregnering med CCA och kreosot, betraktas som farligt avfall).

Enligt avfallsförordningen, är hantering av avfall i Europa inriktad mer mot återvinning och mindre mot eliminering. Bland de franska kraven, kan tre huvudsakliga tendenser iakttas för återvinning av träavfall: endast behandlat avfall kan behandlas i förbränningsanläggningar för energiutvinning, högbehandlat träavfall måste elimineras genom förbränning och lätt behandlat avfall kan antingen återvinnas som spånskivor eller elimineras.

I detta sammanhang uppgår mängden träavfall från bygg‐ och rivningsplatser till 7 miljoner ton i Frankrike. Bland dem, motsvarar 5% obehandlat trä, och 25% är lätt behandlat. Den höga förbränningspotentialen för träavfall ger dessutom en möjlighet att ersätta konventionellt bränsle som används i förbränningsanläggningar.

De fyra huvudsakliga metoder som används för att behandla träavfall är återvinning i spånskivor, förbränning med energiutvinning, förbränning och deponering. På grund av olika typer av träavfall, krävs ett konditioneringsteg innan återvinning. Även om förbränningen är fördelaktigt på grund av sitt neutrala kol, visar livscykelanalyser utsläpp av andra föroreningar. Dessutom visas att kontrollerade elimineringsmetoder har mindre miljöpåverkar än återvinningsmetoder som ej har rätt utrustning. Återvinning är alltså inte alltid att föredra om man beaktar de effekter som gjorts vid denna undersökningen.

Konkurrensen mellan olika behandlingsmetoder och låga priser på träavfall är specifika ekonomiska aspekter som skulle kunna påverka utvecklingen inom området. Dessutom, den ökande acceptansen av människor för återvinning och lokala avfallshanteringsmetoder, liksom behovet av inhemska energikällor är faktorer som sannolikt kan främja bränsle från träavfall.

Dessa drivkrafter utvecklas på ett mycket snabbt sätt. Avfallsförordningen är på väg mot införandet av standarder för att främja utvecklingen av lätt behandlat träavfalls bränsle. Tekniska och sociala förbättringar, exempelvis källsortering och utveckling av återvinningsmetoder ger också sannolikt positiva effekter.

En integrerad lösning för att utveckla bränsle från träavfall skulle vara att genomföra starka ekonomiska incitament till förmån för ren teknik för återvinning av träavfall. Den här förbättringen kan sedan vara ett medel att anta den dubbla utmaningen av hantering av träavfall och ersättning av fossila bränslen.

Nyckelord: Avfallshantering ‐ Bygg‐och rivningsavfall ‐ träavfall ‐ biomassa ‐ förbränningsmotor och livscykelanalys


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Acknowledgements

First of all, I am very grateful to Ms Monika Olsson for the guidance, advice and support she provided me during the various stages of this project, despite the distance that separated us.

Special thanks to Mr Gaëtan Rémond, Miss Marie Michelet, and Miss Carole Miller, who warmly welcomed me in their company during these six months. The knowledge, tools and experience they shared with trust gave me the opportunity to make a step in the great world of waste management. This study wouldn’t have been so documented without their help.

Great benefits were also taken through discussions with the other colleagues of the team, as well as from the interviews with the various actors of wood waste management, in France and Belgium. All of them are greatly acknowledged.

Anna Björklund from division of Environmental Strategies Research, KTH, and Karin Orve from Industrial Ecology department, KTH, are thanked for solving the technical and administrative issues.

Thank you all my friends and family from France and elsewhere for your opinions, innovative ideas and encouragements.


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Contents

Abstract..........................................................................................................................2

Sammanfattning.............................................................................................................3

Acknowledgements........................................................................................................4

List of figures .................................................................................................................7

List of tables...................................................................................................................8

Nomenclature: definitions and symbols ........................................................................9

1. Introduction .......................................................................................................... 10 1.1 Aim and objectives .................................................................................................... 11 1.2 Methodology ............................................................................................................ 12 1.3 Borders ..................................................................................................................... 12

2. Generalities on wood waste derived fuel.............................................................. 13 2.1. Definitions and classification of wood wastes............................................................ 13 2.1.1. Wood wastes and wastes derived fuel..................................................................... 13 2.1.2. Classification of wood wastes .................................................................................. 13

2.2. Current regulation and evolutions ............................................................................. 17 2.2.1. General regulation on waste management.............................................................. 17 2.2.2. Regulation on wood wastes treatment methods..................................................... 20 2.2.3. Focus on biomass ..................................................................................................... 22 2.2.4. Financial and fiscal regulation .................................................................................. 24

3. Wood wastes from C&D treatment methods ........................................................ 26 3.1. Wood waste potential ............................................................................................... 26 3.1.1. Production in France and Europe............................................................................. 26 3.1.2. Technical properties ................................................................................................. 27 3.1.3. The need for treatment and recovery...................................................................... 29

3.2. Conditioning wood waste.......................................................................................... 29 3.3. Wood waste reuse and recycling methods................................................................. 31 3.4. Wood wastes combustion ......................................................................................... 31 3.4.2. Advantages ............................................................................................................... 32 3.4.3. Limitations ................................................................................................................ 32

3.5. Elimination methods : incineration and land filling¨ ................................................. 33

4. Case study: Environmental impact and comparative building sites’ wood wastes treatments LCAs........................................................................................................... 34

4.1 Introduction to the case study ...................................................................................... 34 4.2 Goal and scope.......................................................................................................... 34 4.2.1 Functional unit.......................................................................................................... 35 4.2.2 System boundaries ................................................................................................... 35


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4.2.3 Assumptions, limitation and uncertainties .............................................................. 36 4.3 Methodology ............................................................................................................ 37 4.3.1 Impact assessment methods and impacts categories.............................................. 37 4.3.2 Normalization and weighting methods .................................................................... 38

4.4 Life cycle inventory analysis ...................................................................................... 38 4.4.1 Recycling................................................................................................................... 39 4.4.2 Combustion .............................................................................................................. 40 4.4.3 Incineration .............................................................................................................. 42 4.4.4 Land filling ................................................................................................................ 43

4.5 Life cycle interpretation ............................................................................................ 44 4.5.1 Single score............................................................................................................... 44 4.5.2 Characterization ....................................................................................................... 46 4.5.3 Normalization ........................................................................................................... 47

4.6 Conclusion on the case study..................................................................................... 49

5. Economical and societal aspects ........................................................................... 50 5.1 Economical aspects .................................................................................................. 50 5.2 Social and societal aspects......................................................................................... 51

6. Discussion: influencing factors and future development...................................... 53 6.1. Regulatory evolutions ............................................................................................... 53 6.2. Technical evolutions and environmental impacts ...................................................... 53 6.3. Economical and social evolutions .............................................................................. 54 6.4. Summary of the driving forces and their evolutions................................................... 54 6.5. Focus on labelling, financial incentives and communication ...................................... 55

Conclusion ................................................................................................................... 57

Recommendation for further work.............................................................................. 59

References .......................................................................................................................... 60

Appendices .................................................................................................................. 63


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List of figures

Figure 1: Wood wastes origins (CTBA, 2008) ................................................................................. 14 Figure 2: Distribution of different types of wood in construction and demolition wastes in France (IFEN, 2004) ...................................................................................................................................... 27 Figure 3: Wood wastes properties for different families of wood ( (BiomasseNormandie, 2010) (Boyle, 2004) .................................................................................................................................... 28 Figure 4: Flowchart of a typical production process for wood chips (Kurata, Watanabe, Ono, & Kawamura, 2005) ............................................................................................................................. 30 Figure 5 : Impact and damage categories assessed by eco‐indicator 99 LCA method (Goedkoop & Spriensma, 2000)................................................................................................................................ 1 Figure 6: Process flowchart for wood waste form C&D recycling.................................................... 39 Figure 7: Process flowchart of wood wastes from C&D combustion............................................... 41 Figure 8: Process Flowchart of incineration of Wood waste from C&D .......................................... 42 Figure 9: Process flowchart of land filing of wood waste from C&D ............................................... 43 Figure 10: Comparison of four methods of treatment of wood wastes .......................................... 45 Figure 11: Comparison of the methods according to each impact categories ................................ 46 Figure 12: Comparison of the methods by normalization ............................................................... 48 Figure 13 : Distribution of prices for natural gas and wood combustion (CIBE, Element constituting wood fuel prices, 2009). ................................................................................................................... 51 Figure 14: Global influences of regulations as a frame for wood waste fuel development ............ 56


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List of tables

Table 1: Waste derived fuel categories (FNADE, 2008) ................................................................... 13 Table 2: Wood treatment and danger of preservatives (CSTB, 2005) (INERIS, Les réglementations relatives aux déchets industriels dangereux. Programme DCE‐05 "propriéte des produits", 2006)15 Table 3: Examples of slightly treated wood waste (CSTB, 2005) ..................................................... 16 Table 4: BREFs on preparation of different type of waste derived fuels (Commission, 2005) ........ 20 Table 5: Combustion unit categories in France................................................................................ 21 Table 6: Average lower heating value of more common fuels (Boyle, 2004) .................................. 28 Table 9: Sale prices for wood combustion units in France in 2006 (CIBE, Wood heat networks. Enquiry report carried out by the French center of wood energy, 2008)........................................ 51 Table 10: Factors influencing wood waste combustion and their potential evolutions.................. 55


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Nomenclature: definitions and symbols

Abbreviations:

BAT: Best Available Techniques BREF: Best available techniques Reference C&D: Construction and demolition CCA: Chromium Copper Arsenic CEN: European Standard Organization (Centre Européen de Normalisation) ELV: Emissions Limit Valuesß HIW: Hazardous Industrial Waste IPBC: Iodo Pronynyl Butyl Carbamate IPPC: Integrated Pollution Prevention and Control ISO: International Standard Organisation LCA: Life Cycle Analysis LHV: Lower Heating Value MDF: Medium Density Fiber MSW: Municipal Solid Waste NIMBY: Not In My BackYard NHIW: Non Hazardous Industrial Waste NOx: Nitrogen Oxides PCDD: Polychlorodibenzo‐para‐dioxins PCDF: Polychlorodibenzo‐furans PVC: Polyvinyl Chloride RDF: Refuse Derived Fuel SOx: Sulphur Oxides TOE: Ton Oil Equivalent

Units:

1MJ.kg‐1 = 2300 1kcal.kg‐1

1000 kcal = 4,187 MJ.kg‐1

1kWh= 3,6MJ

1toe= 11,666kWh =41,76 GJ.kg‐1


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1. Introduction

Waste management is in France a controversial question. Despite lots of efforts, partly guided by European regulations, and innovative practices from neighbour countries, French decision‐makers (either politics or industrial), as well as household opinions, remain disorganised, thus making the implementation of a real integrative and sustainable waste management system complicated.

In this context, wood wastes, and more particularly wood wastes from construction and demolition sites are still hardly recovered, in the teeth of their specific qualities for combustion.

In fact, on the one hand, the amount of wood wastes produced from industrial sectors is increasing with the construction, furniture and packaging activities growth. On the other hand, European and French regulatory framework is evolving towards a more sustainable waste and energy management. Therefore, industrial ecology approaches are more and more promoted through the implementation of innovative and regulated actions such as waste recovery targets, the perspective of an End of waste status, biomass rate in the energy mix, normative framework on bio fuel, and new fiscal frameworks on activities.

In addition, technical developments make the recovery methods more and more sustainable and lead the recent emergence of new waste sorting and preparation methods to optimize and reduce the risks of recycled products.

Such evolutions, among others, constitute interesting circumstances for the development of wood wastes valorisation as fuel: Such possibility appears as a real opportunity to cope with the double challenge of conventional fuel replacement, and waste management. However, because wood wastes recovery through the waste‐fuel concept is still not the common way of dealing with wastes, the question to be answered is what is really influencing the development of such a practice? Finding some keys to the answer to this question is likely to bring interesting basis to promote incentive towards innovative waste management system.

The various driven forces leading the development of wood wastes fuel are interrelated and interact with many other factors. Consequently, this results in a complex situation addressing links between a wide variety of actors.

This study, relying on academic and professional opinions, provides an analysis of the current situation of wood wastes recovery aiming at assessing the influence of different factors on the development of fuel prepared from wood wastes from construction and demolition site. This assessment provides the necessary material to evaluate the likely and more preferable trend to be developed in the next years.


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1.1 Aim and objectives

According to the societal and environmental problems and opportunities resulting from wood wastes recovery as a fuel, particular focus on the situation should be done Moreover, the identification and evaluation of the driving forces influencing provides an interesting overview of what could be the trend to observe in the future year.

To tackle this question, the general aim of this study is to identify and evaluate the driving forces influencing the market of refuse derived fuel such as wood wastes, as well as the opportunity that it could imply for the double challenge of wastes reduction and fuel replacement.

This goal can be detailed through the overall goals aiming at finding effective and non‐harmful means to protect the environment and health by managing the wastes produced by human activities.

In order to achieve this goal, the objectives of this report are to investigate the following aspects:

‐ Classify and define wood waste derived fuels ‐ Clearly describe the current and future regulatory situation on wood waste derived fuels

in France and Europe ‐ Identify and describe the main current practices linked to the treatment of wood waste in France and Europe, including

o Preparation of the wastes for recovery o Recycling as particle board o Combustion practices

‐ Evaluate the environmental impacts linked to construction and demolition wood waste derived fuel combustion in a life cycle approach

‐ Compare the impact of wood waste recovery as a fuel and three other treatment methods (namely recycling, incineration and land filling), with the help of an LCA approach

‐ Describe and analyze the economical evolution linked to wood waste derived fuel development

‐ Describe and analyze the societal impacts linked to wood waste derived fuel development


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1.2 Methodology

The methodology used to carry out this study consists in the following steps.

First of all, a thorough literature survey serves as a basis to this study to collect and gather the existing knowledge and background on the subject. This survey includes major scientific papers from the eighties until today as well as policies reports. The work on legislation is based on the reading of the so cited texts.

Secondly, in order to show a realistic view of the practical context in professional situation, the thesis has been written during an internship in the French counselling company INDDIGO, specialized in waste management strategies. This experience has been a real chance to enrich the arguments of this research thesis by adding the professional opinion and practical examples to the scientific rigors. Therefore this period was the opportunity to participate in national working groups on wastes recovery as fuels including presentations, interviews and discussions with national experts as well as sharing of documentation and opinions. Four visits on construction and demolition sites and five visits on waste treatment facilities were organized, enabling to collect specific information on the current practices and difficulties met by the stakeholders.

The life cycle assessment (LCA) carried out on the third part of this study is based on the ISO 14040 advised methodology. The choice of the software SimaPro to carry out this LCA has been made based on discussions with specialized professors on the subject. Indeed, it appeared to be the most convenient tool according to the needs of the study. The data has been collected through study visits and reports from different processes. Part 3.2 presents the detailed methodology for this LCA.

Finally, because of a lack of specific data, the analysis of economical and social aspects is here based on simplified and qualitative analysis. The methodology used followed these steps:

‐ Collection of data concerning general prices of wood waste treatments and recovery methods, thanks to study visits and reports;

‐ Identification and analysis of the different current and likely negative impacts linked with the development of wood wastes treatment;

‐ Qualitative evaluation of these impacts costs;

1.3 Borders

In this thesis, the study is limited to:

‐ Practices in Europe and France ‐ Wastes derived fuel of wood type ‐ Wood waste from construction and demolition sites ‐ The evaluation of technical and environmental aspects

The borders of the LCA are described in the concerned part (4,3).


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2. Generalities on wood waste derived fuel

The first part of the study poses the basis of the current situation wood waste derived fuels: what they are and what are the rules associated with their management and use.

2.1. Definitions and classification of wood wastes

The understanding of the origins and features of wood waste recovery is an essential step for the approach. The following part describes where they come from, how they are produced and what they are made of.

2.1.1. Wood wastes and wastes derived fuel

Wastes derived fuel can be defined as wastes whose properties enable an efficient energy recovery when they are burnt by combustion processes. Instead of a mere elimination by incineration, waste can at least supplement and at best take over conventional fossil fuel to produce the needed energy.

Wastes derived fuels include different categories depending on the type of wastes they are issued of. The following table sum up the most common waste derived fuel (FNADE, 2008):

Waste derived fuel category

Refuse derived fuel

Solid bio fuel Hazardous waste derived fuels

Specific fuels

Concerned waste MSW and NHIW (Non hazardous industrial waste)

Biomass –Untreated wood waste

Used oil, solvents, treated wood waste

Bone meal, tyres

Table 1: Waste derived fuel categories (FNADE, 2008)

Wood wastes used as fuel can be split into two categories depending on their level of hazardous characteristics.

According to the European Waste Catalogue (EWC) (Communities, 1994), waste derived fuels are classified under the following numbers:

‐ 19 02 09* solid combustible wastes containing dangerous substances; ‐ 19 02 10 combustible wastes other than those mentioned in 19 02 08 (liquid combustible

wastes containing dangerous substances) and 19 02 09; ‐ 19 12 10 combustible wastes (refuse derived fuel)

2.1.2. Classification of wood wastes

Wood wastes are mainly issued from forestry activities, wood industry, construction and demolition sites and old furniture from households. Pieces of wood waste are also found on waste processing facilities, where all type of household or industrial wastes are collected. These different categories are described in figure 1.


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Figure 1: Wood wastes origins (CTBA, 2008)

In this study, a focus is made on wood wastes from construction and demolition activities.

Because of their organic nature, wood wastes are not inert. However, they can be considered either as non‐hazardous or hazardous wastes depending on the substances they contain. Even if raw wood contains natural traces of harmful substances such as heavy metals (CSTB, 2005), the main hazards come from the substances added during the preservative treatment of the wood. Indeed, depending on the usage of wood products, different chemical or physical treatment can be implemented. We can quote two main practices:

‐ Surfacing treatment where the substances only lain on the wood surface (coating and gluing)

‐ Preservation treatments where the substances penetrate the wood fibres for a better protection against outer attacks (fire proofing, preservation by soak or impregnation).

The different features of treatments of wood can be summed up in the following table:

Type of treatment

Aim Preservatives Potential danger of preservative

Thermal treatment

Protection None None

Non metallic paintings or varnishes

None Coating Protection and decoration

Metallic paintings or varnish (heavy metals, organic compounds)

Toxic in high concentration

Mineral glue, animal glue None Gluing Assembling

Synthetic resins (chloroacetate vinyl, urea formol)

Toxic, noxious

Forestry wood

e.g.: forestry plaquettes

Wood industry sub-products

e.g.: off cuts sawdust, shaving

End of life Wood

Wood wastes from C&D activities

Public works wood waste

e.g.: pruning wood,

electricity pole

Building wood waste

e.g.: parquet floor,

framework

Other activities wood waste

e.g.: tray

Household wastes

e.g.: furniture

Wood waste from waste processing facilities

Wood waste recovery and treatment platforms

Workshops wood waste

e.g.: wood


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Fire Proofing Resistance to fire attack

Metallic salts, isopropanol Toxic in high concentration

Boron and other heavy metals

Toxic in high concentration

Preservation by soak

Resistance to medium biological attacks

Diazole, pyrethroide, IPBC Irritating, mutating, hazardous for reproduction

Preservation by impregnation

Resistance to high biological attacks

CCA, arsenic, organic copper, creosote

Carcinogenic, irritating, toxic

Table 2: Wood treatment and danger of preservatives (CSTB, 2005) (INERIS, Les réglementations relatives aux déchets industriels dangereux. Programme DCE‐05 "propriéte des produits", 2006)

Wood wastes can then be divided into three main categories described below:

‐ Untreated wood waste ‐ Slightly treated wood waste ‐ Highly treated wood waste

Untreated wood waste

Untreated wood wastes are issued from raw wood that only received mechanical or thermal treatment, but which did not receive any chemical preservative treatment. They are considered as non‐hazardous wastes and can be assimilated as biomass as defined in the European regulation (c.f. part 2.2.3).

In the case of C&D wastes, untreated wood wastes mainly come from construction sites or workshops where raw wood is processed to make furniture. They include the following types of wood wastes:

‐ Packaging in wood (pallets, boxes) ‐ Sawn raw wood

Given their non‐toxic nature, these wastes are easily recovered through reuse, recycling or in combustion (energy recovery). The potential of this recovery is detailed in the following parts of the report.

Slightly treated wood waste

Slightly treated wood wastes are so called because of the small concentration or low danger of the preservative substances they contain. Wood that received coating, gluing, fireproofing and preservation treatments by soak is considered as slightly treated. As seen previously in table 2, these treatments can involve different kind of substances, and different harmful effect for human and environment. Even if most of these substances are found in low concentration in wood waste, thresholds are defined in the regulation (annexes of directive 67/548/EC) from which wood waste


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must be considered as hazardous wastes. These thresholds are described for the most common substances potentially contained in wood wastes, in appendix A.

Examples of slightly treated wood wastes are classified below according to the treatment they received:

Type of treatment

Waste origin Type of wood waste Examples

Construction and demolition sites, household dumps, millwork

Recently coated wood used indoor

Furniture, framework, parquet floor, windows, doors

Coating

Demolition sites of old building

Wood coated before 2003 and used indoor

Furniture, parquet floor

Gluing Construction and demolition sites, household dumps, millwork

Particle board, plywood, laminated wood (MDF, OSB)

Furniture, framework, parquet floor, windows and doors in plywood

Fire Proofing Interior wood Indoor wood making a barrier against fire

Door, window, framework

Construction site and millwork

Raw wood subjected to temporary treatment with bore

Packaging, off cut from sawing

Preservation by soak

Construction and demolition sites, household dumps, millwork

Outdoor wood with low exposition to soil, sun or humidity

Scaffold, outdoor framework

Table 3: Examples of slightly treated wood waste (CSTB, 2005)

Because of the multiplicity of these wood wastes, it is very difficult to sort them out. Moreover, even if the major part of these wastes does not imply any hazards, the share whose concentration of hazardous substance exceeds the threshold of non hazardous wastes is mainly never identified. Indeed, chemical analyses are too expensive and the amount of waste is not sufficient to carry out on C&D sites. As described in the next chapter, according to the precautionary principle, this type of wood waste is rather hard to recover. Regulation and standardization is however evolving towards more flexibility in order to promote the recovery of slightly treated wood in dedicated or adapted combustion units.

Highly treated wood waste

Eventually, heavy treatment can be applied for wood requiring important penetration and retention, usually linked to frequent outdoor usages and high exposition to bacteria attacks, sun or humidity conditions. The treatments are carried out at high pressure by autoclave so that arsenic, creosote or CCA (chromium, copper, arsenic), can be ingrained in the deep layer of the wood.


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Wood wastes containing these substances are called highly treated and are mainly produced on renovation or demolition sites because of the high restriction concerning the preservative substances used (Kurata, Watanabe, Ono, & Kawamura, 2005). The pieces concerned are mainly:

‐ Utility poles ‐ Railway line sleepers ‐ Fences ‐ Outdoor furniture (garden furniture)

Given their hazardous properties, treatment methods for these wastes categories are very limited. Only incineration and land filling in adapted facilities (allowed to treat hazardous wastes) can be used. A new process developed in France by the company Thermya aims at pyrolysing these wastes in order to produce raw carbon. With high efficiency performances and a likely development through Europe, this method could be a good opportunity to get rid of these problematic wastes (Hery, 2003).

A classification of these wood wastes is summed up in appendix B.

2.2. Current regulation and evolutions

Given the constant regulatory evolutions in the European Union regarding environmental protection, activities linked to waste derived fuel as a mean to recover wood waste are promoted and settled through various measures whose origins can be found in the sustainable management of waste, natural resources and energy generation.

The current development of these fuels, pushed by new biomass energy production projects, called for an adaptation in the regulatory framework for these substances. This could answer in order to the following emergent risks:

‐ The control of waste management methods hierarchy and waste recycling practices; ‐ The knowledge and traceability of waste derived fuel composition; ‐ The control of polluting effluents coming from installations treating wood wastes.

2.2.1. General regulation on waste management

Principle and objectives

Objectives and management principles of wastes are defined at the European level by the directive 2008/98/CE of 19 November 2008 on waste. According to this text:

‐ Hierarchy of management principles gives priority to prevention and recycling methods, limiting waste land filling possibilities. The principle of “preparing for re‐use” is now applied for wastes that are likely to be recycled.

‐ Wastes used as fuel are considered as a recycling method (R1) ‐ An objective of 50% (weight) of re‐used or recycled material from households is fixed for

2020.


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‐ Substances which received specific recovery treatment, and responding to certain criteria defined by the directive can cease to be considered as waste (end‐of‐waste status, article 6)

At the French level, these principles are implemented through the environmental code (articles R.541 and following), and the specific law named “Grenelle de l’Environnement”.

These texts add the following objectives: ‐ Obligation for the furniture waste producer to ensure the clean end‐of‐life of their

products. ‐ An objective of 75% of packaging wastes recovery from 2012. ‐ An incentive to the energy recovery of wastes.

These regulatory texts are then in favour of an increasing energy recovery of household waste, non‐hazardous industrial wastes and wood waste. European and French regulation are then in favour of wood waste derived fuel.

Focus on the End‐of‐waste status

The 2008/98/EC directive introduces in its sixth article the possibility for a recovered waste to get a product status. The aim of this principle is to suggest regulatory and economic incentive and promote recycling activities. Wastes derived fuels are appear then at the fore front of these categories of new products.

According to the directive, the criteria required in order for a waste to acquire a product status are the following:

‐ “the substance or object is commonly used for specific purposes ‐ a market or demand exists for such a substance or object; ‐ the substance or object fulfils the technical requirements for the specific purposes and meets the existing

legislation and standards applicable to products; ‐ the use of the substance or object will not lead to overall adverse environmental or human health

impacts.”

Because the European Commission did not give any guideline in regards with more precise criteria, state member must implement this principle with their own criteria, which should be proposed to the community and accepted. Therefore, several risks can arise when dealing with the end of waste status (FEAD, 2009). As examples, one can quote the hard control of the condition uses and quality for these new products, the long term guaranty of an existing market for the products issued of wastes, or the difficulty to trace the products in case of transboundary transfers.

The implementation of this new principle could then lead to important changes, especially in terms of markets management and substances traceability. The following regulation might need some evolution in order to adapt to the new European requirements:

‐ REACH directive and associated texts ‐ Trans‐boundary rules ‐ Emerging specific rules concerning waste derived fuel


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‐ European and national standards ‐ Evolutions in flows, markets and treatment practice are also likely to be predicted.

Transboundary transfers

Transboundary wastes transfers and movements are controlled according to the following regulations:

‐ Basel convention of 7th February 1994; ‐ EC rule n°1013/2006 concerning supervision and control of shipments of waste; ‐ Decision C(2001)107 of the Council on the control of transboundary movements of wastes

destined for recovery operation; ‐ Rule EC n°1418/2007 of 29 November 2007 concerning the export for recovery of certain

waste These rules turn out to especially control and then influence the movement of recovered material through the European countries. Indeed, sending wood wastes to elimination in another country implies a very narrow and expensive follow up. When sent to recycling, the transfer is however less expensive. Moreover, treated wood wastes belong to the orange list of the OECD, and their transboundary transfer must then be notified and controlled. BREF on waste management

The Best Available Techniques (BAT) References (BREFs) form a set of summaries gathering selected techniques used for pollution prevention and required by article 16(2) of the IPPC directive (Council directive 96/61/EC concerning integrated pollution prevention and control).

BREF on waste treatment method is intended to cover the activities described in Section 5 of Annex I of the IPPC Directive, namely ‘waste management’. It should be noticed that waste incineration activities, as well as thermal waste treatments such as pyrolysis and gasification are covered by other BREFs (point 5.2 of Annex I of the Directive).

The following BATs are applied to waste derived fuel:

Preparation of waste to be used as fuel

117. transferring the knowledge of the waste fuel composition prepared

118. quality assurance systems 119. manufacturing different type of waste fuels 120. waste water treatments 121. safety aspects

Preparation of solid waste fuels from non‐hazardous waste

122. visually inspecting the incoming wastes 123. using magnetic ferrous and non ferrous metal separators 124. using near‐infrared techniques 125. the preparation of the waste fuel at the correct size

Preparation of solid waste fuels from

126. drying or heating operations 127. mixing and blending operations


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hazardous waste 128. the abatement of particulates Table 4: BREFs on preparation of different type of waste derived fuels (Commission, 2005)

2.2.2. Regulation on wood wastes treatment methods

No specific regulation is edited in Europe or in France concerning the specific management of wood waste. Nonetheless with the increasing environmental concerns towards better waste management, wood wastes treatments are submitted to the rules of the facilities they are oriented to, namely recycling as particle boards, combustion, incineration and landfill. Yet these facilities are in France submitted to specific rules, adapted to the danger of each activity. This part presents the main right when dealing with wood wastes treatment in these facilities.

Recycling methods

Recycling methods for wood waste include composting and material recycling as particle boards. In order to avoid any risks of contamination with hazardous substances, these methods ask for high levels of requirement for the type of waste they incorporate.

For composting, only untreated fraction of wood can be accepted.

For the manufacture of particle boards, a certain amount of slightly treated wood wastes can be accepted, added to untreated wood waste, according to the requirement of European Panel Federation (EPF) and of each producer.

Highly treated wood wastes are definitely forbidden for recycling.

Incineration and combustion

For a decade, incineration appeared in Europe to be one solution for efficient elimination of the majority of the wastes. Even if some incineration plants are today equipped to recover the energy (heat or electricity) produced during the burning process, this activity remains, at first, a method to eliminate waste. This means that, usually, the energy recovery process is not effectively designed to recover the most of the wastes. Yet, an efficiency of 65% is needed for an incinerator to be considered as a recovery process. This level is almost never reached in France. On the contrary, using wood waste in a combustion unit is considered as a recovery method. In that latter case, the wastes are considered as raw material and can supplement or replace conventional fuels such as oil, coal or natural gas.

At the European level, the 2000/76/EC directive of 4 December 2000 on waste incineration regulates these activities. In order to promote wood waste recovery, this directive excludes these later of its scope, except for the wood waste likely to contain halogenated organic compounds or heavy metals (article 2).


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This directive was implemented in the French law in 2002. Waste incineration units must follow the specific regulation of classified installations. As a consequence, units incinerating hazardous wastes have to follow strict requirements on atmospheric and liquid emissions, as well as storage and waste elimination conditions on the site. Moreover, implementation of high prices for waste incineration promotes other methods of treatment such as recycling.

Combustion activities are in Europe regulated by the 2001/80/EC directive of 23rd October 2001 on the limitation of emissions of certain pollutants into the air from large combustion plants. This text fixes the Emissions Limit Values (ELV) for the main air pollutant (SOx, NOx and particulates) for combustion units whose power is superior to 50 MW. According to this directive, wood wastes fuels are defined as biomass: “products consisting of any whole or part of a vegetable matter from agriculture or forestry which can be used as a fuel for the purpose of recovering its energy content and the following waste used as a fuel”

In the French regulation, combustion units must follow some requirements according to the fuel they use and the power they produce. According to these criteria, the plants activities must be either allowed, or declared to the authority in charge of the classified installations for the environment.

The following table summarizes the requirement for both types of combustion units:

Activity reference

Type of wood fuel accepted Requirements Power Status needed

> 20MW

Authorization 2910 A Biomass: ‐ Commercial fuels with known features (sub‐products from wood transformation industry presenting any trace of treatment cannot be assimilated to biomass but to a waste) (Note of 11th August 1997)

‐ Annual measurements, for VOC, heavy metals (Note of 11th August 1997)

2 MW


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Land filling

Land filling activities are regulated by the 99/31/EC directive of 26th April 1999. This text defines the procedures to run the landfill in the less harmful way possible. In France, three types of landfill are regulated:

‐ Hazardous waste landfills ‐ Non hazardous waste landfills ‐ Inert waste landfills

From the 1st of July 2002, because of the danger these elimination methods can generate for soil and air pollution those facilities can only be used for elimination of ultimate wastes. In other words, recyclable or incinerable waste can’t be treated in these plants. Financial incentives (very high and increasing prices for waste treatment in landfills) were implemented to promote the reduction of this practice.

A summary of the recovery methods for wood wastes is stated in appendix B.

2.2.3. Focus on biomass

As firstly defined in directive 2001/77/EC (Council, 2001): “biodegradable fraction of products, waste and residues from agriculture, forestry and related to industries, as well as the biodegradable fraction of industrial and municipal waste”, wood wastes can be considered as biomass. As a result, a specific regulation must be applied.

Biomass and energy mix

In order to solve several problems resulting from the use of fossil fuel for energy production (resource depletion, energy dependence, consequences on climate change); the European Council has been implementing different energy policies. One of the major actions consists in developing renewable energy sources so that they could reach a large percentage of the average European energy consumption. Directive 2009/28/ EC fixes the rules related to the promotion of renewable energy sources. This text especially points an objective of 20% of renewable energy in the European energy consumption by 2020. In the current state of energy consumption, biomass is expected to highly contribute to reach this goal. European legislation thus forces countries members to develop this energy source.

In France, the promotion of energy production by biomass is implemented by an action plan for the 2006/2012 period. This program includes the following aspects:

‐ Helps for district heating networks and wood heating systems projects ‐ Fare revision for electricity from biomass and cogeneration systems ‐ 90% increase of biofuel use by 2020 ‐ 50% increase of wood heated accommodation by 2020


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Biomass promotion is then a central aspect linked to wood waste management. However, an ambiguity remains concerning the type of wood waste included in biomass definition. Indeed, the evolution of the definition through the years and regulations (Appendix C) led to exclude some types of construction and demolition wood wastes from the field of biomass. Therefore, 2008/98/EC directive on waste defines biomass as:

“ Products consisting of any whole or part of a vegetable matter from agriculture or forestry which can be used as a fuel for the purpose of recovering its energy content and the following waste used as a fuel:

(a) vegetable waste from agriculture and forestry; (b) vegetable waste from the food processing industry, if the heat generated is recovered; (c) fibrous vegetable waste from virgin pulp production and from production of paper from

pulp, if it is co‐incinerated at the place of production and the heat generated is recovered; (d) cork waste; (e) wood waste with the exception of wood waste which may contain halogenated organic

compounds or heavy metals as a result of treatment with wood preservatives or coating, and which includes in particular such wood waste originating from construction and demolition waste; “

According to this definition, wood wastes from C&D activities must be studied in more details before any classification as biomass. Nevertheless, no threshold concerning the concentration of halogenated organic compounds or heavy metals are defined in the European legislation. Because of this lack of information, the precautionary principle is then applied in France on this subject and prevents any slightly treated wood waste from being considered as biomass (recommendation of 11th August 1997 on combustion units).

The result of this strict regulation and practice leads to a very low recovery rate for slightly treated wood wastes that could contain, as seen in the previous parts, very low concentration of organic halogen compounds or heavy metals.

In order to make these practices more flexible and enable to enhance the recovery of wood waste as biomass, European and French standards have been studied to suggest acceptance threshold and guidelines for use of this waste as biomass.

Standards

In order to make the regulation and practices more relevant among the different European countries, the general direction of environment of the European Commission mandated in 2002 the European Standardization Committee (CEN) to elaborate experimental and technical specification framing activities linked to biomass. These standards are currently adapted to the French standardization system (AFNOR). However, the works of International Standard Organization (ISO/TC 238 on solid bio fuel) has not succeeded yet to publish any international requirements or guidelines concerning this subject.


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The main European group linked with biomass is CEN/TC 335 on solid bio fuels. In relation with the European regulation, this working group excludes wood wastes containing halogenated organics or heavy metals of the definition of solid bio fuel (standards CEN/TS 14051).

Eventually, in addition to these general standards in development, several studies in France led to the publication of three referential documents on wood fuel (CTBA, 2008). One of them especially concerns wood wastes issued from industrial activities such as construction and demolition. According to these documents, slightly treated wood waste could be burnt in combustion units if they fulfil the following requirements:

‐ Halogenated organic compounds concentration


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In the aim of influencing prevention against sanitary risks, polluting activities and wastes are regulated by several financial mechanisms. If the oldest one in France is the tax on polluting activities, the national plan for carbon credit allocation, issued from the Kyoto protocol, is another tool oriented towards environmental car: Additionally, the many funding mechanisms for biomass development project are also interesting tools to promote the safe development of fuel issued from wood wastes.

Tax on polluting activities

In France, each activity generating pollution is subjected to a tax. The rates are re‐evaluated each year depending on the hazardous effect of the considered field activity. The money obtained is allocated to the French environmental protection agency (ADEME) for implementation of prevention programs. This tax appears to be a real tool of influence for the development of wood waste recovery considering that it penalizes land filling and incineration activities against the one built to recycle wastes (biomass combustion or material recycling).

National plan for carbon credit allocation

In application of the Kyoto protocol and the directive 2003/87/EC, the second edition of the plan (2008‐2012) fixes emissions allowances for the facilities contributing the most to greenhouse gases emissions. In practice, a plant which rejects a relatively huge amount of GHG is subjected to a fixed amount of pollution permits for a year (the quotas). These quotas can then be bought or sold according to the plant emission. At the beginning of 2010, the price of carbon on the market was 13€/t.

The targeted field are mainly the industrial and energy sectors among which the credits are allocated according to the proportion of their historical emissions. Because biomass is considered to have a neutral carbon balance, its emission factor is null, which enhances the burning of the potential of burning of this kind of material for energy production and industrial systems operation.

Other financial mechanisms

Several other tools are currently under research and in development all over the European countries to promote the use of biomass as a major energy production sources. Renewable energies’ feed‐ in tariffs (REFIT) are for instance a mechanism guarantying the purchase of electricity from renewable and more particularly biomass, at relatively high prices. Renewable energy certificate system, pointing out the environmental benefit of renewable energy production by implementing high rate of sales, is also in development in the Union (Boyle, 2004).

In France, national financing programs are implemented to help projects based on biomass promotion. As an example, the French government, respectively funded 22 and 32 energy production facilities using biomass as a fuel, in 2006 and 2008 (MEEDDM, 2010).


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3. Wood wastes from C&D treatment methods

As seen in the first chapter, construction and demolition activities produce very specific types of wood wastes. Because some of them can be harmful for both human health and ecosystems, the European regulation forces their producers to take responsibility and the necessary measures to dispose them. The third chapter of this report states the potential of wood wastes (and especially C&D wood wastes) in terms of quantity and quality. A description of the existing methods used to recover or treat these wastes is provided. The aim being to shows that recovery of as fuel is a real opportunity.

3.1. Wood waste potential

Compared to other types of wastes, wood wastes from C&D sites represent a relatively huge amount of disposals. In addition, their properties make them a renewable product whose quality can be significantly valorised.

3.1.1. Production in France and Europe

As mentioned earlier, wood wastes take their origins in three main activities: forestry residues, wood transformation sub‐products and construction and demolition sites wastes. Since these activities are growing, the amount of wastes generated also, grows rapidly over the years. Therefore, the Joint Research Centre estimated an amount of 70 455 000t of waste wood flow in Europe. Among those, almost 10million t would be originated from C&D activities (JRC, 2009).

In France an amount of 16 million tons of wood wastes have been evaluated to be produced by these activities in 2004 (ADEME, 2005). Among this amount, 4 million tons are issued from construction and demolition activities.

A national enquiry carried out by the French Environmental Institute (IFEN, 2004), on C&D sites evaluated the amount of wood waste in France at up to 3,568,000t in 2004. This amount represents less than the 1% of the total quantity of C&D waste produced in France. Among these wood wastes, 2,470,000t are proved to be highly treated wood wastes (that is to say hazardous wood wastes, mainly from public works activities). Even if the quantity of slightly treated wood waste has not been evaluated yet, the inquiry shows that the amount of agglomerated and coated wood on construction and demolition sites could represent the 25% of the total wood waste found on these sites (figure 2).

According to the growth of C&D activity in France, (an increase of 60% between 2004 and 2008 in France, according to the sales turn over given by the French Statistic Agency (INSEE, 2008)), the non hazardous wood wastes issued from construction and demolition site in France can be estimated at 7,000,000t in 20081.

1 This evaluation follows the conventional way of estimation for waste production. Indeed, it is considered that production of waste is linearly linked to the activity. However, such assumption must be considered


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Figure 2: Distribution of different types of wood in construction and demolition wastes in France (IFEN, 2004)

As seen previously, in France, the untreated wood wastes are, when sorted out, often recovered and recycled. The highly treated wood waste, concerning the major fraction of this wood waste production cannot be recovered and must be handled in specific incineration facilities for hazardous wastes. Nevertheless, the important amount of slightly treated wood waste (estimated then at 1,750,000 t in 2008) remains hardly collected, neither recovered. Indeed the wastes come from different small sites and are often mixed with the other types of wastes. The recovery of this important amount turns out to be an interesting opportunity for the double challenge of waste management and natural resources protection.

3.1.2. Technical properties

Fuel derived from wood can be presented into different forms depending on the function they will need to fulfil. Four main families of wood waste derived fuel issued from C&D sites can then be discerned: sawdust, logs, shaving and crushed mixed fuel. Because the main problematic and for now difficult to recover family is the crushed mixed fuel, the study will be focused on this type of fuel (SPANO, UNILIN, KronoFrance, & Isoroy, 2010).

Properties of fuel are evaluated according to two main criteria: (1) the combustion efficiency and (2) the harmful emission that the combustion can generate.

The combustion efficiency is primary ruled by the energy contained in the material. The natural process of a tree growth combines solar energy and other sources such as soil nutrients, water and carbon from the air to accumulate energy. During its life, a wood product loses little of this energy by decomposition. Therefore, an interesting quantity of energy is still stored in wood wastes. This energy can either be released to produce another form of energy (that is what happens during combustion) or can be reused for the physical properties of wood to make resistant materials (matter recycling). Because the energy stored in the wood can be replenished at the same rate as it is used, biomass can be considered as a renewable energy (Twidell, 1986).

with precaution, indeed, prevention methods and practices can quickly change from on year to another, uncertainty which is not considered in this study.


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In order to measure the energy potential contained in fuel, the notion of lower heating value (LHV) is used. LHV is defined as the amount of heat released by combusting a specified quantity and returning the temperature of combustion products to 150°C. Because wood is mainly made of carbon and organic compounds, its capacity to produce energy by burning is interesting to study. Indeed, its lower heating value (LHV) varies between 6 and 18 GJ/t. In comparison, and according to table 6, coal LHV is 28GJ/t in average (Boyle, 2004).

Fuel Lower Heating Value (GJ/t) Wood (green, 60% moisture) 6 Wood (air‐dried, 20% moisture) 15 Commercial wastes 16 Sugar cane residues 17 Wood (oven‐dried, 0% moisture) 18 Coal 28 Oil 42 Natural gas 55 Table 7: Average lower heating value of more common fuels (Boyle, 2004)

However, LHV is mainly linked with moisture content, that is to say the rate of water contained in the wood (figure 3).

Moreover, pieces size influences the technological choices for the combustion (feeding systems and hearth). Wood waste derived fuel size is directly linked to the fuel preparation. This property varies between 10 to 80 mm for wood waste (figure 3).

Figure 3: Wood wastes properties for different families of wood ( (BiomasseNormandie, 2010) (Boyle, 2004)

Finally, the emissions and ashes are negative production linked to wood waste fuel combustion. These by‐products are generated from mineral matters contained in wood waste after combustion and can create problem of clogging, air emission pollution or residual wastes (calcium, potassium, magnesium and heavy metals). Wood has a general ashes rate of 1% in average. However, because they contain more various contaminants, treated wood wastes have a greater ashes rate than raw wood (CSTB, 2005).


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3.1.3. The need for treatment and recovery

Wood wastes from C&D sites represent an important quantity of matter produced each year. In addition, as mentioned above, these wastes have interesting qualities, especially in terms of combustion potential or mechanical resistance. For this reason, wood wastes from construction and demolition sites appear to be an opportunity to reduce the use of other resources such as fossil fuel or raw wood.

Nevertheless, 70% of hazardous C&D wood wastes cannot be reused in their actual state. This fraction must then be addressed in specific processes. If most of the time, they are for now eliminated through incineration, new processes are appearing in Europe to use the energy captured in these waste in most cautious methods. This is the case of pyrolysis process suggest by the company Thermya that treat already 35 000t of treated wood waste each year (Hery, 2003).

If recovery is highly recommended in the case of untreated or slightly treated wood, a step of conditioning is needed before recycling.

3.2. Conditioning wood waste

When wood wastes are produced on construction or demolition sites, they can either be sorted out in specific containers or be collected mixed with other wastes. In the second case, if they are not directly eliminated, wood wastes are sent to specific wastes facilities to be sorted out. However, wood wastes can be of different size and can contain various types of contaminants. In order to be reused, they must first of all be non hazardous wastes, and secondly be conditioned in specific forms of specific features. The following part describes the families of products made from C&D wood wastes, and the methods to manufacture them.

Because of the variation in wood waste sources, they must be prepared and presented under the forms and compositions described in the previous paragraph. Preparation operations are most of the time carried out on the wood waste sorting and conditioning facilities. This process includes four mains steps (Picheta, 2010):

‐ Waste sorting ‐ Crushing ‐ Metal removal ‐ Screening

During sorting operation, slightly and untreated wood wastes are separated from highly treated wood and wastes made of other material. A visual or mechanical sorting step can also remove the slightly treated fraction if necessary. Chemical analysis can eventually improve the quality of the sorting when financial resources enable it.

Crushing steps are essential when wood wastes are issued from demolition sites (i.e. when the majority of the wastes are slightly treated wood). Three types of crushing can be described (:

‐ A tearing with help of knives is used for the wastes exempt from any metals


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‐ Slow crushers are sturdier and are used to roughly reduce the size and volume of wood wastes.

‐ Rapid crushers enable to refine the wood waste mixture issued from the slower crushing. These devices are made of hammers turning at very high velocity (1000 rpm) which enables to obtain a very small and homogeneous crushed wood fuel.

After these two latter mechanical operations, a magnetic metal removing is needed. This step can reach 95% efficiency.

Finally, the screening is the stage that enables to get a regular size product. The methods used for this process are:

‐ Rotative screens ‐ Sieves with disc in form of star ‐ Vibrating sieves constituted of one or two screens animated by an alternative movement,

adapted to crushed wood.

The chip wood resulting from this preparation can either be used as a fuel either as a material for particleboard manufactures. The production process of chip wood, and its use is described in the following flowchart:

Figure 4: Flowchart of a typical production process for wood chips (Kurata, Watanabe, Ono, & Kawamura, 2005)

It can then be noticed that the processes needed to prepare wood fuel are energy, time and space demanding. These activity presents however them some job opportunities and enable to enhance fuel quality.


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3.3. Wood waste reuse and recycling methods

As seen previously in this report, the European regulation recommends reuse and recycling as priority methods for waste management.

Regarding wood waste from demolition sites, products have most of the time been used until they can’t provide the function they would be supposed to anymore. Reusing wood wastes from these activities is then never done according to precautionary principle.

However, on construction sites, pallets are products that are often reused. For economical reasons, and because this product does not imply any contamination risk, some companies get the pallets back, and repair them if needed. This practice is unfortunately only observed for this type of wood waste.

Crushed untreated or demolition wastes can nevertheless be recycled to produce particle boards. According to the French and Belgium professionals interviewed (KronoFrance, Unilin, Spano), an average of 30% of wood waste can be introduced in the manufacturing process of particle board. This fraction can however reach 75% in some factories. The main barrier against the substitution of raw wood is indeed the pollution content of the material that can either damage the machines or reduce the quality of the final product.

In order to avoid any kind of problem in the industrial process or for the product quality, requirements are recommended by the European Panel Federation (EPF, 2010). These requirements are implemented in accordance with the various European standards on particle board. They include:

‐ Mainly untreated wood wastes (essentially from pallets) must be introduced in the process. However, a small amount of mixed slightly treated wood waste can be accepted.

‐ The fraction of wood waste must be crushed and exempt of any metal, plastic or cardboard, material that could damage the machines or lower the quality of the board produced. (The size of the crushed pieces depends on the manufacturing process)

‐ The moisture content must be the lower possible

Particle board manufacturers can then provide with these products by purchasing the mixed and crushed material to wastes sorting and treatment facilities or directly from wood wastes producers.

Recycling of wood wastes as particle boards seems nowadays to be unstable because of the fluctuation of wood price. In addition, the current development of biomass threatens the recycling of wood waste by particle board production.

3.4. Wood wastes combustion

One other interesting treatment method for wood waste is to recover the energy contained in this material by producing heat and thus energy. Combustion of wood waste for district or


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industrial heating is then more and more spread. This part presents the principles of wood combustion and its interest.

3.4.1. Combustion principles

Thanks to its important carbon content, wood turns out to be a qualified fuel. When mixed with the oxygen of the air, and activated by a flame, the carbon and hydrogen of wood decomposes to produce carbon dioxide and heat. This is an exothermic reaction:

During the combustion, the following steps succeed:

‐ At 100°C, moisture contained in the wood evaporates ‐ From 200°C to 600°C, organic matter decomposes. This step is called pyrolysis ‐ From 300°C to 500°C, combustion gases are pyrolised

In order to obtain a perfect combustion, that is to say, an optimal degradation of all the matter, the following conditions must be respected:

‐ A large oven area to enable a long flame ‐ An average temperature of 800°C ‐ A configuration enabling the optimal mixing of air and gases ‐ An excess of air compared with the fuel introduced

3.4.2. Advantages

One advantage of waste treatment by combustion is the high potential for volume reduction that avoids to spread sanitary risks linked with wastes management.

Then, one very important advantage of wood combustion is that it does not contribute to carbon dioxide emissions. Indeed, if the wood is grown in a sustainable way, and if combustion is complete, the amount of CO2 released during the combustion is actually almost the same that have been captured during the wood growth. Wood wastes combustion (that is to say biomass) can therefore be considered as a sustainable energy source: it is not depleted by continued use and does not generate significant environmental problems (Boyle, 2004). Wood can be considered as a regenerative fuel (Bowyer, 1995).

3.4.3. Limitations

Nevertheless, combustion of wood wastes implies the emissions of gaseous pollutants, which must be treated after the combustion process. According to Tatano et al. (2009), the most important flue gases emitted from wood combustion are CO, HCl, SOx and NOx and particulate matters. The quantity of these pollutants varies depending on the type of burn wood waste. This


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experiment proves as well that combustions of medium

wood waste derived fuel: state of the art ...471435/...wood wastes derived fuel 4 acknowledgements...

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