The Classification of Coal Combustion Products under - Eurelectric

Letter sent to European Commission : ENV-LIST-OF-WASTE-TECHNICAL-PAPER@ec.europa.eu 

Subject : Commission Consultation on the review of the Hazardous Properties 

Brussels, 29 May 2012 

Dear Sir/Madam, 

Members of EURELECTRIC’s Waste & Residues Working Group, together with our colleagues at 

ECOBA, have been following closely developments concerning proposed revisions to the List of 

Wastes (LOW, as set out in Decision 2000/532/EC) that are being considered and that are intended 

to more closely align entries for hazardous wastes with definitions of hazardous appearing in other 

legislation. In this respect we have noted with interest the Consultation on the Review of the 

Hazardous Properties (“the consultation document”) that was recently issued by the Commission. 

Having reviewed the consultation document, EURELECTRIC, ECOBA and their Members would like to 

comment on the impact of what is being proposed on wastes from power stations and other 

combustion plants (LOW chapter 10 01), and especially coal fly ash (LOW entry 10 01 02) which is 

one of the key materials of interest to us. Whilst detailed comments are included in Annex I to this 

letter, we are, in summary: 

� in favour, in principle, with proposals that will simplify and harmonise the definition of 

hazardous wherever it appears in products and wastes legislation; 

� concerned that the very detailed nature of the Technical Proposal means that industries such 

as ours have had very little time to evaluate the changes in full; 

� extremely concerned by the prospect that coal fly ash could be classified as hazardous on the 

basis of its calcium content alone, which is inappropriate; and 

� extremely concerned about the classification of coal fly ash as hazardous in the LOW, or even 

the introduction of a hazardous mirror entry, as such a move will: 

o have a negative impact on the acceptability of coal fly ash for utilisation; 

o consequently, increase in the volumes of coal fly ash requiring disposal, at an 

increased cost and at a time when void space for waste disposal, and particularly 

hazardous waste disposal, is becoming increasingly scarce; 

o go against many years of experience, which has shown that coal fly ash does not 

pose a hazard to human health and/or the environment when used beneficially or 

when managed as a waste; and 

o be counter to the non-hazardous classification of coal ash according to both the 

European Union Regulation concerning the Registration, Evaluation, Authorisation & 

restriction of Chemicals ( the REACH Regulations, 1907/2006) and the European 

Regulation on the Classification, Labelling and Packaging of Substances and Mixtures 

(the CLP Regulations, 1272/2008). 

As a result of these conclusions we are strongly of the opinion that coal fly ash should not be 

classified as hazardous in any regulations and certainly should remain as an absolute non-hazardous 

entry on the LOW. 

…/… 

Union of the Electricity Industry - EURELECTRIC AISBL . Boulevard de l’Impératrice, 66 - bte 2 . B - 1000 Brussels . Belgium 

Tel: + 32 2 515 10 00 . Fax: + 32 2 515 10 10 . VAT: BE 0462 679 112 . www.eurelectric.org

The conclusions set out above are amplified in the more detailed comments which follow in Annex I 

to this letter. Although currently being produced in lower quantities, and not addressed specifically 

in this submission, we would be similarly concerned by any proposals that would classify ashes from 

other combustion processes, including fly ash from peat and untreated wood (LOW entry 10 01 03), 

as hazardous. As well as leading to similar consequences as those for coal fly ash, a change to the 

classification of biomass ashes would almost certainly curtail the development of the biomass-fired 

power stations that are already running or are being developed in a number of Member States to 

deliver the EU and EC targets to reduce the carbon intensity of electricity generation. 

EURELECTRIC and ECOBA are aware that a number of our Members have taken up the issues set out 

in this letter with their Member State authorities. Should it be appropriate, Members of 

EURELECTRIC’s Waste & Residues WG and ECOBA would be very happy to come and discuss with you 

in more detail the concerns set out in this letter. 

Yours faithfully, 

Steve WAYGOOD 

Chairman of EURELECTRIC WG Waste & Residues 

Info EURELECTRIC 

The Union of the Electricity Industry–EURELECTRIC is the sector association representing the common interests of the 

electricity industry at pan-European level, plus its affiliates and associates on several other continents. 

In line with its mission, EURELECTRIC seeks to contribute to the competitiveness of the electricity industry, to provide 

effective representation for the industry in public affairs, and to promote the role of electricity both in the advancement of 

society and in helping provide solutions to the challenges of sustainable development. 

EURELECTRIC’s formal opinions, policy positions and reports are formulated in Working Groups, composed of experts from 

the electricity industry, supervised by five Committees. This “structure of expertise” ensures that EURELECTRIC’s published 

documents are based on high-quality input with up-to-date information. 

For further information on EURELECTRIC activities, visit our website, which provides general information on the association 

and on policy issues relevant to the electricity industry; latest news of our activities; EURELECTRIC positions and statements; 

a publications catalogue listing EURELECTRIC reports; and information on our events and conferences. 

Info ECOBA 

ECOBA, the European coal combustion products association was founded in 1990 by European energy producers to deal with 

matters related to the usage of construction raw materials from coal. The members are all generators of electricity and heat 

as well as marketers. ECOBA members represent over 86 % of the CCP production in the EU 27 countries.

Annex I – Detailed Comments 

Principle and Scope of the Consultation Document 

EURELECTRIC, ECOBA and their Members are generally in favour of the principle to simplify and 

harmonise the ways in which hazardous properties are defined in various pieces of European 

legislation affecting products, by-products and wastes. However, we remain very concerned about 

the possibility that a number of types of coal combustion products, and particularly coal fly ash 

(entry 10 01 02 in the LOW), could be classified as hazardous wastes by either an absolute entry in 

the LOW or through the introduction of a hazardous mirror entry because they contain high enough 

levels of calcium (CaO and/or Ca(OH)2) for them to display Hazardous Property H8 Corrosive (as set 

out in Annex III to Directive 2008/98/EC). Our strong belief is that such a classification on the basis of 

concentration or calcium content alone would be inappropriate, but should rather consider their 

overall exposure and environmental risks. 

In reviewing the consultation document, we do recognise that the potential for the reclassification of 

CaO- and Ca(OH)2-containing wastes being unjustified in all cases in view of the potential 

environmental effects is acknowledged in the consultation paper’s Technical Proposal Background. 

Indeed, footnote 2 of this part of the document discusses examples of potential exemptions. Whilst 

the footnote confirms that the wastes of concern to us, which are particularly in chapter 10 01 of the 

LOW, are “under discussion”, we are disappointed that the potential impacts of a reclassification to 

the industry and to electricity consumers is not considered. As well as believing that these impacts 

are significant, our disappointment is partly because the quantities of coal fly ash (38 million tonnes 

of coal ash produced from coal/lignite power plants in 2008) currently produced across the European 

Member States (15) are similar to the amounts of iron and steel slag that are produced (and which 

are considered in the consultation document supporting report from ÖKOPOL Gmbh) and are 

significantly greater than the amounts of untreated biomass ash (which are also considered in the 

supporting report). In our opinion, the volumes of these ashes produced across Europe mean that 

the impact of their potential reclassification should be considered in some detail before any decision 

is made. 

The Properties of Coal Fly Ash 

Coal ashes are an inevitable consequence of the combustion of coal and lignite in large boilers used 

across Europe and the world as part of the electricity generation process. Although the particle size 

of coal fly ash, bottom ash, slag and boiler dust vary, each of them is essentially very similar in 

chemical structure and composition; hence the reason they are typically considered together as ‘coal 

ash’. The physical and chemical properties of coal ash are considered, together with information on 

the beneficial uses to which they have been put over many years, in the joint EURELECTRIC/ECOBA 

Briefing on the classification of coal combustion products under the revised Waste Framework 

Directive (2008/98/EC) that is provided in Annex II. 

The Classification of Coal fly ash under Existing Regulations 

The producers of coal ashes across Europe have put in a considerable amount of effort over recent 

years to evaluate the properties of their products or wastes. Under existing waste and landfill 

regulations, coal ashes are classified as a non-hazardous waste and no risk or hazard to human health 

and/or the environment has ever been shown. 

Under REACH, the European Union Regulation concerning the Registration, Evaluation, Authorisation 

& restriction of Chemicals ( EC Regulation 1907/2006) registration dossiers have recently been 

submitted for a number of coal combustion products (CCPs). By the 1st December 2010, separate 

REACH dossiers had been submitted for a number of CCPs: ashes from wet and dry bottom boilers 

(coal ash); ashes from fluidized bed combustion boilers; cenospheres; calcium sulphate; SDA- 

Product; and biomass ash. Each of these dossiers includes an up-to-date evaluation of the intrinsic 

properties of each CCP.

Under REACH, coal ash has been registered an “Unknown or Variable composition Complex Reaction 

Products or Biological Materials Substance” - a UVCB substance. The registration dossier provided 

the prerequisite test data and analysis which resulted in coal ash being classified as non-hazardous in 

accordance with the REACH Regulation. Based on the assessments undertaken in that report, it was 

also concluded that coal ash classified as non-hazardous according to the CLP Regulations (the 

Regulation on the Classification, Labelling and Packaging of Substances and Mixtures (EC Regulation 

1272/2008). 

So, in the opinion of EURELECTRIC, ECOBA and their Members, we contend that under existing 

product and waste law coal ash is a non-hazardous product or waste when utilised or disposed of 

and this evaluation should not be changed within the revision of the LOW. 

Impacts of Classifying Coal Fly ash as Hazardous in the LOW 

As is set out in detail in the Briefing provided in Annex II, coal fly ash has a wide range of established 

uses; siliceous ashes find a wide range of uses within the construction industry, whilst calcareous 

ashes are mostly used for backfilling opencast lignite mines from which the coal was taken in the first 

place. EURELECTRIC, ECOBA and their Members believe strongly that the classification of coal fly ash 

as hazardous in the LOW, through either an absolute or mirror entry, or in any other legislation will 

have a negative impact on the acceptability of ash utilisation as perceived by both the construction 

industry and the general public. The result would then be that utilisation rates for coal fly ash would 

decrease significantly and, consequently, the volumes requiring disposal would increase. A decrease 

in utilisation will mean that more primary aggregate will be required to replace the coal fly ash. Such 

an outcome is contrary to the positive steps being taken by the Commission and many Member 

States to encourage the use of by-products and recovered wastes over primary aggregate, and as set 

out in the Roadmap to a Resource Efficient Europe launched by the Commission in September 2011. 

In addition, the significant benefits of reducing CO2 emissions by replacing cement with coal fly ash in 

construction and construction products will be lost. An increase in the volume of coal fly ash 

requiring disposal will also have significant ramifications across Europe, where void space for waste 

disposal, and particularly hazardous waste disposal, is becoming increasingly scarce. Hazardous 

waste landfill sites have to be engineered to a higher standard than is necessary for the disposal of 

coal fly ash. In addition, in many Member States landfilling of hazardous wastes attracts a 

significantly higher rate of Landfill Tax, which would further increase disposal costs. 

The introduction of a mirror hazardous entry for coal fly ash in the LOW will also have other 

significant implications. Primarily it will lead to uncertainty as to whether any particular batch of coal 

fly ash is a hazardous waste or not - coal fly ash varies in composition in the same way that the 

composition of the parent coal from which it is derived, and which is a natural product, varies. As a 

result, significantly more testing will have to be done to determine whether a particular batch of coal 

fly ash is hazardous or not, and therefore which LOW entry is applicable, than is currently accepted 

by both the industry and the regulatory authorities as necessary. 

We have not been aware of any specific proposals before this one to change the classification of coal 

fly ash on the LOW since the list was published in 2000 as Decision 2000/532/EC. Were the 

Commission’s proposal to classify coal fly ash as a hazardous waste, either definitively or via a 

hazardous mirror entry in the LOW, to be subject to a full financial impact assessment, then we 

strongly believe that the results would show a significant negative impact over the current position 

and one which is not justified on the grounds of environmental or exposure impact. 

Comments on the Technical Proposal 

In reviewing the consultation document, we are very aware that the content of the Technical 

Proposal is very detailed. In this respect, we feel that industries such as ours have had very little time 

to evaluate the proposed changes in full. In our opinion, the impacts of the proposed changes cannot 

be evaluated in such a short timeframe and therefore we would appreciate it if more time would be 

granted for us to work with yourselves to understand the full implications of the proposals and to

determine the correct approach for coal fly ashes. In the meantime, to avoid a presumptive change 

which would make all coal fly ashes hazardous, and so no longer be so attractive for beneficial use, 

we strongly recommend that the existing classification system is used until further work is 

completed. In our opinion such an approach would be consistent with the comments in the 

Background to the Technical Proposal of the consultation document which states both that “Given 

that reliable and detailed information about wastes (e.g. statistics about the type s and amounts of 

wastes classified as hazardous by a given hazardous property) is not available at EU level, the impacts 

of the changes cannot be established in all cases with certainty” and that “There may be some cases 

where changes in chemicals classification could lead to changes in waste classification that would not 

be justified in all cases in view of the potential environmental effects.” 

Conclusion 

In conclusion, EURELECTRIC, ECOBA and their Members strongly believe that the reclassification of 

coal fly ash as a hazardous in any regulations on the basis of its calcium content alone is entirely 

inappropriate. The impact of doing so would be to significantly reduce utilisation of the material, 

consequently increasing the amounts requiring disposal at landfill sites engineered to an 

unnecessarily high standard and attracting a higher taxation rate. The costs of such disposal would 

increase significantly over those currently experienced and would therefore add significantly to the 

cost of coal-fired electricity generation across Europe, potentially making it uneconomic and/or 

increasing process to the consumer. In our view, such a move could therefore run the risk of security 

of supply issues. 

The introduction of an absolute hazardous entry for coal fly ash in the LOW, or even a hazardous 

mirror entry, would be inconsistent with its classification under the REACH and CLP Regulations and 

would have significant implications; above all, it would produce a negative perception of coal fly ash, 

which would have the same impact as an absolute hazardous classification. Coal fly ash has been 

shown over many years not to pose a hazard to human health and/or the environment when 

managed as a waste and so should remain as an absolute non-hazardous entry on the LOW.

Annex II - EURELECTRIC/ECOBA position paper on the Classification of Coal 

Combustion Products under the revised Waste Framework Directive 

(2008/98/EC) (Final 08/11/10)

June 2006/revised June2011 

European Coal Combustion Products Association 

Joint EURELECTRIC/ECOBA Briefing: 

The Classification of Coal Combustion Products under the 

revised Waste Framework Directive (2008/98/EC) 

Each year, more than 100 million tonnes of coal and lignite ashes and desulphurisation 

products are produced by power stations throughout the European Union in addition to the 

main product electricity. These solid materials, which can be described collectively as coal 

combustion products 1 (CCPs [1]), are inevitable as they are produced as a result of 

requirements to meet air emission standards set in other EC Directives [2]. Each of the CCPs 

has specific physical and chemical properties that make them suitable for utilisation in 

established markets which have, typically, existed for many years. These applications include, 

amongst others, use in cement, as both raw kiln feed material and as a direct cement 

replacement [3], in concrete [4], in the production of lightweight aggregates and lightweight 

blocks [5], as aggregates in building and road industries [6], in mining and other operations as 

a construction or fill material [7], as mineral fillers [8] and, in the case of FGD gypsum, as a 

raw material in the gypsum industry for the production of plasterboard and as a set retarder in 

the cement industry [9]. Further details of the production, properties and use of various CCPs 

are described in an accompanying document [Annex 1]. 

In many applications CCPs are used as a replacement for naturally occurring materials and 

therefore offer environmental benefits by avoiding the need to quarry or mine primary 

resources. The use of CCPs is thus an excellent example of sustainability, results in the 

saving of natural resources and material and, in many cases, helps to reduce energy demand 

and emissions to the atmosphere which result from the extraction or manufacture of the 

substituted product [10]. A significant example of the positive environmental benefits that come 

from the use of CCPs is the use of coal fly ash in concrete and blended cement, where, as 

well as savings in natural resources and energy, the use of every tonne of ash saves about 

one tonne of CO2 when compared to the use of cement itself [11]. Numerous studies (toxicity, 

lab and on-site evaluations etc.) have shown that CCPs have no negative impact on the 

environment or on human health when put to beneficial use. Also, to be effectively used in a 

number of applications, they have to satisfy relevant national and European building materials 

standards and regulations or user-imposed technical requirements. Not only do these 

standards set quality criteria for utilisation, but their existence in itself is a recognition that the 

materials are of value. 

Where CCPs are used directly from the power station or after short periods of storage in 

dedicated silos, stores and stockpiles designed to maintain them in a form suitable for use, 

they are, in the producer’s opinion, not discarded and are not ‘wastes’ as defined in the Waste 

1 The term “coal combustion products” (CCPs) is commonly used for ashes and desulphurisation 

products produced following the combustion of coal for power and steam generation. It is synonymous 

with terms such as “coal combustion residue”, “secondary mineral”, “secondary raw material” and 

“secondary product“ used in other publications and regulations. 

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Framework Directive (2008/98/EC) [12]. The use of CCPs in these ways is consistent with the 

aims of the Directive and, in particular, with the waste hierarchy set out in Article 4, which puts 

waste prevention above options such as re-use, recycling and recovery [13]. In each case 

where they are utilised, their further use is certain, they are suitable for use in their existing 

form and without undergoing any further processing other than normal industrial practice and 

their use meets all of the relevant product, environmental and health standards applicable to 

that use. Therefore, CCPs going directly from the power station that produced them or from an 

associated production process to an end-user in a form which is suitable for immediate use 

are excellent examples of by-products as defined in Article 5 of the Directive [14]. As byproducts 

will be substances that will be placed directly on the market, they will be subject to 

the REACH regulation [15]. As such CCPs should be included within any guidance to 

accompany the revised Directive as examples of industrial by-products which should never be 

considered as wastes. As the REACH registration contains a full description of the chemical, 

mineralogical, physical, toxicological and ecotoxicological characterisation of CCPs, as well as 

a chemical safety report and an assessment report with exposure scenarios reflecting the use 

of the materials, there is no need for additional parameters to verify the by-product status. 

In circumstances where CCP production levels exceed demand or where demand varies 

temporally, some of them, and fly ash in particular, are discarded as wastes and are typically 

landfilled at mono-disposal sites. However, should demand subsequently increase it is very 

easy for the materials to be recovered and, with only minimal treatment, they can then be used 

in the same markets as ‘fresh’ materials. In these cases, the materials have ceased to be 

wastes at the place of recovery in line with the end-of-waste criteria set out in Article 6 of the 

Directive [16]. As such, recovered CCPs are an excellent example that could be used in any 

guidance to accompany the Directive as a waste stream which, when recovered, ceases to be 

waste. 

In summary, the production of CCPs is an inevitable consequence of the combustion of coal in 

large power plant boilers. Although not the main commercial product of the process, CCPs are 

of value in a number of other ways and, as shown in Figure 1, are used either immediately or, 

in the longer-term, after recovery from stockpile or mono-landfill sites. In the former case, 

CCPs should be regarded as by-products and never as wastes; in the latter case, once 

recovered, CCPs should cease to be wastes and become products at the place of recovery 

(Figure 1). 

EURELECTRIC and ECOBA believe that, in both cases, CCPs are very good examples for 

use in any guidance produced to accompany the revised Waste Framework Directive 

(2008/98/EC). 

2

Fig. 1: Flow chart describing definitions 

Primary operation 

MAIN PRODUCT 

(electricity, steam and 

heat) 


BY-PRODUCT 

(utilisation as a PRODUCT 

covered by product 

regulations and REACH) 

Directly useable 

PROCESS 


Resulting from the 

primary operation 

COAL COMBUSTION 

PRODUCTS 

(coal and lignite ashes and 

desulphurisation products) 

Not directly useable 

WASTE 

(covered by the revised Waste 

Framework and other 

Directives) 

Recovery 

END-OF-WASTE 

(utilisation as a PRODUCT, 

covered by product regulations 

and REACH)



[1] For the purposes of this Note, coal combustion products (CCPs) are: bottom ash, boiler 

slag and fluidised bed combustion (FBC) ash (i.e. bottom ash, slag and boiler dust 

according to EWC Codes 10 01 01 and 10 04 15); coal fly ash (10 01 02 and 10 01 17); 

and calcium-based reaction wastes from flue-gas desulphurisation in solid form (10 01 

05). 

[2] As the descriptor suggests, bottom ash, slag and boiler dust are retained within the 

boiler following combustion and are removed in a number of ways depending on the 

furnace design. Fly ash, on the other hand, leaves the boiler entrained in the flue gases 

and, in order to meet air quality requirements set out in EC Directives, like the Large 

Combustion Plant Directive (2001/80/EC), is typically removed prior to the power station 

stack by electrostatic precipitation. 

Flue gas desulphurisation products result from the treatment of the flue gases prior to 

emission to reduce the sulphur content of the exhaust gases. A number of techniques 

are commercially available to do this and the exact nature of the product depends on the 

technique employed. 

An accompanying document [Annex 1] describes, in more detail, production routes and 

properties of various CCPs. 

[3] Fly ash and bottom ash can be used in the manufacture of cement in two ways; as a raw 

material for cement clinker production or as a major constituent in the production of 

blended cement. In the former case ash serves as a source of silica and alumina, which 

traditionally come from natural sand and clay. 

For the production of blended cement, i.e. Portland pozzolana and Portland fly-ash 

cement typically containing around 30% fly ash, ash has to meet the requirements of 

European standard EN197-1 which includes a requirement for conformity evaluation. 

[4] Fly ash is added to concrete to enhance its technical performance for a number of 

reasons. The physical and chemicals properties of the ash that can be used in this 

application, together with details of the conformity evaluation, are detailed in European 

Standard EN 450, Fly ash for concrete – definitions, specifications and conformity 

criteria. 

[5] Fly ash is used as a siliceous source in the manufacture of aerated concrete blocks. 

These have excellent insulating properties for a cementitious material and consist of 

~85% fly ash. Ash used in these applications has, again, to meet the requirements of 

European Standards. 

Fly ash has also been used as the raw material in the manufacture of lightweight 

aggregates according to European Standard EN 13055. Bottom ash is also used as a 

coarse and fine aggregate in the manufacture of ‘Lightweight Concrete Blocks’. For this 

application, it has to meet the requirements of the European Standard for lightweight 

aggregates, EN 13055. Bottom ash is the preferred material by all manufacturers due to 

the lightweight nature and stability of the aggregate. 

[6] Fly ash, bottom ash and boiler slag are used in a number of applications as aggregates 

in building and road construction. Specific examples include the use of bottom ash as a 

drainage layer and road sub-base material and as a wearing surface in equestrian 

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centres and car parks. In these applications, the requirements of European and national 

standards typically have to be met. 

[7] Fly ash has been widely used as a fill material for a number of years. In this application, 

and in road construction in particular, its use has been based on its availability, its ease 

of compaction and its ability to form stable, durable landforms. Examples include its use 

in embankments and bridge abutments. In addition, for use in underground mining, 

reactivity requirements have to be met. 

[8] Fly ash, as well as cenospheres, i.e. hollow sphere fly ash particles with ultra-low 

densities, are used as a fill material in a number of applications, including paints, 

plastics, car body panels, glass fibre resin systems and refractory panels. 

[9] Most of the FGD gypsum produced in Europe is utilized in the gypsum and cement 

industries in products like plasterboard, gypsum blocks and plasters. The quality criteria 

for the use of FGD gypsum as a raw material for the gypsum and cement industry are 

defined in a number of standards. 

[10] In many of the applications developed for CCPs, their utilisation results in economic 

benefit. Most applications, however, also provide environmental benefits, including: 

– saving of natural resources; 

– saving of energy; 

– saving of emissions of pollutants to the air; 

– saving of CO2 emissions; 

– saving of landfill space. 

At least one, and in most cases several, of the environmental benefits apply to all 

applications of fly ash. 

[11] Following on from [10], the most impressive example is the replacement of a part of 

cement by fly ash in concrete or the use of fly ash as a main constituent of blended 

cement. For the production of one tonne of cement about 1.6 tonnes of raw material 

have to be mined, crushed, calcined and heated to a temperature of 1200 to 1400°C. In 

addition, 0.95 tonnes of material have to be finely ground to produce Portland cement. 

2900 MJ of thermal energy and 100 kWh of electrical energy are needed to produce one 

tonne of Portland cement. 

The production of Portland cement is not possible without emissions of pollutants to air 

even though the emissions from cement production have been drastically reduced in the 

last few decades. The production of Portland cement is also inevitably associated with 

CO2 emissions due to the calcination process and the energy demand. The replacement 

of Portland cement by fly ash therefore makes a corresponding reduction in the various 

environmental impacts associated with cement production. In the EU15 member states it 

is conservatively estimated that the use of 2.9 million tonnes of fly ash in cement 

manufacture results in a reduction in CO2 emissions of the same amount per annum. 

Many of the other uses of CCPs do at the very least avoid the environmental impact of 

the mining of natural resources and the processing of the minerals and save the space 

needed for the disposal of CCPs. 

[12] According to Article 3 of Directive 2008/98/EC on waste, ‘waste’ means ‘any substance 

or object which the holder discards or intends or is required to discard’. 

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[13] Article 4 of Directive 2008/98/EC describes the waste hierarchy and is reproduced below 

for reference. 

Article 4 

Waste hierarchy 

1. The following waste hierarchy shall apply as a priority order in waste prevention and 

management legislation and policy: 

(a) prevention; 

(b) preparing for re-use; 

(c) recycling; 

(d) other recovery, e.g. energy recovery; and 

(e) disposal. 

2. When applying the waste hierarchy referred to in paragraph 1, Member States shall 

take measures to encourage the options that deliver the best overall environmental 

outcome. This may require specific waste streams departing from the hierarchy where 

this is justified by life-cycle thinking on the overall impacts of the generation and 

management of such waste. 

Member States shall ensure that the development of waste legislation and policy is a 

fully transparent process, observing existing national rules about the consultation and 

involvement of citizens and stakeholders. 

Member States shall take into account the general environmental protection principles of 

precaution and sustainability, technical feasibility and economic viability, protection of 

resources as well as the overall environmental, human health, economic and social 

impacts, in accordance with Articles 1 and 13. 

[14] Article 5 of Directive 2008/98/EC deals with by-products and is reproduced below for 

reference. 

Article 5 

By-products 

1. A substance or object, resulting from a production process, the primary aim of which 

is not the production of that item, may be regarded as not being waste referred to in 

point (1) of Article 3 but as being a by-product only if the following conditions are met: 

(a) further use of the substance or object is certain; 

(b) the substance or object can be used directly without any further processing 

other than normal industrial practice; 

(c) the substance or object is produced as an integral part of a production 

process; and 

(d) further use is lawful, i.e. the substance or object fulfils all relevant product, 

environmental and health protection requirements for the specific use and will not 

lead to overall adverse environmental or human health impacts. 

2. On the basis of the conditions laid down in paragraph 1, measures may be adopted to 

determine the criteria to be met for specific substances or objects to be regarded as a 

by-product and not as waste referred to in point (1) of Article 3. Those measures, 

designed to amend non-essential elements of this Directive by supplementing it, shall be 

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adopted in accordance with the regulatory procedure with scrutiny referred to in article 

39(2). 

[15] REACH is the European Community Regulation on chemicals and their safe use (EC 

1907/2006) which entered force on 1 st June 2007. It deals with the Registration, 

Evaluation, Authorisation and Restriction of Chemical substances. The aim of REACH is 

to improve the protection of human health and the environment through the better and 

earlier identification of the intrinsic properties of chemical substances. 

Under the REACH Regulation, producers, manufacturers and importers are required to 

gather information on the properties of their chemical substances and to register the 

information in a central database run by the European Chemicals Agency (ECHA) in 

Helsinki. 

The producers of CCPs have registered their products for use in the construction 

industry under REACH. All information about the chemical, physical, toxicological and 

ecotoxicological properties were compiled in a registration document which will be 

published at the ECHA. 

[16] Article 6 of Directive 2008/98/EC deals with end-of-waste and is reproduced below for 

reference. 

Article 6 

End-of-waste status 

1. Certain specified waste shall cease to be waste within the meaning of point (1) of 

Article 3 when it has undergone a recovery, including recycling, operation and complies 

with specific criteria to be developed in accordance with the following conditions: 

(a) the substance or object is commonly used for specific purposes; 

(b) a market or demand exists for such a substance or object; 

(c) the substance or object fulfils the technical requirements for the specific 

purposes and meets the existing legislation and standards applicable to 

products; and 

(d) the use of the substance or object will not lead to overall adverse 

environmental or human health impacts. 

The criteria shall include limit values for pollutants where necessary and shall take into 

account any possible adverse environmental effects of the substance or object. 

2. The measures designed to amend non-essential elements of this Directive by 

supplementing it relating to the adoption of the criteria set out in paragraph 1 and 

specifying the type of waste to which such criteria shall apply shall be adopted in 

accordance with the regulatory procedure with scrutiny referred to in Article 39(2). Endof-waste 

specific criteria should be considered, among others, at least for aggregates, 

paper, glass, metal, tyres and textiles. 

3. Waste which ceases to be waste in accordance with paragraphs 1 and 2, shall also 

cease to be waste for the purpose of the recovery and recycling targets set out in 

Directives 94/62/EC, 2000/53/EC, 2002/96/EC and 2006/66/EC and other relevant 

Community legislation when the recycling or recovery requirements of that legislation are 

satisfied. 

7 

7



4. Where criteria have not been set at Community level under the procedure set out in 

paragraphs 1 and 2, Member States may decide case by case whether certain waste 

has ceased to be waste taking into account the applicable case law. They shall notify the 

Commission of such decisions in accordance with Directive 98/34/EC of the European 

Parliament and of the Council of 22 June 1998 laying down a procedure for the provision 

of information in the field of technical standards and regulations and of rules on 

Information Society services (1) where so required by that Directive. 

8 

8


Annex 1 


Coal Combustion Products (CCPs) 

- Generation and use - 

Content page 

1. Introduction 2 

2. CCPs: Production, use and requirements for the use 3 

2.1 Bottom Ash 3 

2.1.1 Generation 3 

2.1.2 Properties 3 

2.1.3 Use and requirements for use 4 

2.2 Fly Ash 4 




2.3 Boiler Slag 7 




2.4 FBC Ash 9 




2.5 SDA Product 10 




2.6 FGD gypsum 11 




3 Summary/Conclusion 13 

Annex 14

Coal Combustion Products (CCPs) - Generation and Use 

1 Introduction 


10 

Annex 1 

In coal-fired electricity generating power plants solid minerals are produced during and after the 

combustion of fine ground coal with and without co-combustion in a fully controlled process. The 

materials under consideration are the ashes i.e. the unburnable mineral matter in the fuel 

(bottom ash, fly ash, boiler slag, FBC-ash), and, where abatement equipment is fitted, the 

desulphurisation products obtained from a chemical reaction between the sulphur dioxide, 

which is derived from the sulphur in the coal during the combustion process, and a calcium 

based absorbent, in flue gas desulphurisation installations (SDA product and FGD gypsum). 

Most of the by-products are produced in so called dry-bottom furnaces, i.e. a combustion 

processes with temperatures of 1100 - 1400°C. The combustion process of in a dry-bottom 

furnace and the generation of coal combustion products (CCPs) is shown in figure 1. 

Coal 

Boiler 

Bottom Ash 

NH 3 

DENOX 

ESP 

Fly Ash 

Lime 

FGD 

Chimney 

FGD Gypsum 

Fig 1 Production of coal combustion products (CCPs) in coal-fired power plants 

A similar process (wet-bottom furnace) is used for production of boiler slag. Within this 

combustion process the burning temperature is higher (1500 - 1700°C) and the fly ash normally 

is fed back to the boiler where it melts again and forms boiler slag. 

Fluidised bed combustion (FBC) ash is produced in fluidised circulating bed boilers at lower 

temperatures (800 to 900°C). 

Spray dry adsorption (SDA) product results from dry and semi dry flue gas desulphurisation, 

FGD gypsum from wet flue gas desulphurisation. 

10


2 CCPs: Production, use and requirements for the use 


11 

Annex 1 

In 2008, the amount of CCPs produced in European (EU 15) power plants totalled 56 million 

tonnes and in the larger EU of 27 member states the total production is estimated to be about 

100 million tonnes. Exact figures from the new member states are not available, yet. 

Most of the CCPs produced are used in the construction industry, in civil engineering and as 

construction materials in underground mining (54 %) or for restoration of open cast mines, 

quarries and pits (36.5 %). In 2008, about 2.4 % was temporarily stockpiled for future utilisation 

and 7 % was disposed of 2 . 

The utilisation of the coal combustion products (CCPs) depends on their chemical, 

mineralogical and physical properties. These properties are influenced by the design and type 

of power plant, the source and feed of fuels as well as the type of coal and secondary fuels. A 

constant product quality is the major prerequisite for utilisation. Regarding this, ashes from coal 

combustion have more favourable prerequisites than most ashes from lignite, whose 

composition is subject to comparatively larger fluctuations. Therefore, lignite ashes are 

predominantly used for reclamation of opencast mines. All other fields of application follow the 

same rules as will be described for ashes from coal. 

2.1 Bottom Ash 

2.1.1 Generation 

During the combustion of the fuel in the boiler (see figure 1), some mineralized, partly melted 

particles agglomerate within the boiler and become sintered together. Owing to their weight 

these particles do not pass out of the combustion chamber with the flue gas, but fall to the 

bottom of the boiler, where they are either removed directly or quenched in a water bath 

influencing the particle structure. This bottom ash may be processed, if necessary, by 

dewatering, screening, breaking and/or grading before an interim storage (silo, pit) or loading 

onto truck, train or barge at the power plant’s temporary store and dispatched to its intended 

use. 

Samples for quality monitoring are usually taken direct from the loading equipment at the 

temporary storage facility. The nature and extent of quality monitoring depend on the area of 

application. Where the bottom ash is used as a lightweight aggregate for mortar and concrete, it 

typically has to comply with the requirements of European and national rules (application 

standards). In earthworks and civil engineering it often has to satisfy national regulations of the 

road authorities. In addition, specific requirements may be agreed between the bottom ash 

producer and the user. 

2.1.2 Properties 

Bottom ash consists of irregularly shaped particles with a rough surface. The main chemical 

components are silica, aluminium and iron oxide. The chemical composition of bottom ash is 

largely comparable to that of fly ash (see 2.2). Due to its porous particle structure, bottom ash 

combines low weight with good soil mechanics properties; however, its particle size distribution 

may vary considerably, as it depends on the fineness of the pulverized coal and the combustion 

conditions. 

2 ECOBA- Statistics on Production and Utilisation of CCPs in Europe (EU 15) in 2008 

11


2.1.3 Use and requirements for use 


12 

Annex 1 

In Europe, about 5 million tonnes per annum of bottom ash is produced following the 

combustion of coal and lignite. Whereas bottom ash from lignite power plants is almost entirely 

used for filling worked-out open-cast lignite mines, bottom ash from coal-fired power plants is 

used in other areas. The chemical, physical and mechanical properties of bottom ash and its 

compliance with the relevant standards, guidelines and regulations are crucial to its use as a 

building material. Some uses require further processing of the material by breaking or screening 

to make it more uniform. In other cases the requirements for high-grade use are satisfied even 

without additional processing steps. 

In 2008, about 2.4 million tonnes of bottom ash were used in the construction industry. Out of 

this 37 % was used as a fine aggregate in concrete blocks, 41 % in road construction and about 

16 % in cement (see figure A1 in Annex I). 

Typical uses for bottom ash, together with details of the quality requirements it must meet for 

these uses, include: 

• for concrete blocks: EN 13055-1 3 and national regulations 

• in earthworks and road construction: according to national regulations. 

In particular, the properties of bottom ash are useful: 

- in open placement for the construction of roads and pathways and the creation of 

industrial and storage areas, 

- in landscaping and recultivation measures, 

- in the construction of bound and non-bound load-bearing layers and bound base 

surface layers , 

- in road sub bases and 

- in the construction of noise barriers. 

• as lightweight aggregate for concrete products according to DIN EN 13055-1 2 where the 

conformity evaluation has to follow a similar procedure as described in EN 450-2 for fly ash 

for concrete (see Section 2.2) 

• as a raw material for cement clinker production: site specific requirements 

• as filler for cement: EN 197-1 4 

• for brick production: national regulations 

• for gardening and landscaping: national regulations 

2.2 Fly Ash 


Production of suitable quality fly ash in a coal or lignite-fired power plant is based on the 

principle of pulverized fuel firing (see figure 1, page 2). 

The pulverized coal with or without secondary fuels is blown with air into the combustion 

chamber of the power plant boiler. Combustion (oxidation) of the fuel at a temperature of up to 

1400°C produces mineralized particles which, after a residence time of up to several seconds, 

leave the firing chamber with the flue gas. 

1. The flue gas containing the fly ash flows through the boiler passes and also, if present, the 

denitrification unit and economizer, and is then fed to the dust removal unit. 

3 

EN 13055-1: Lightweight aggregates for concrete, mortar and grout, 2004 

4 

EN 197-1: Cement - Part1: Composition, specifications and conformity criteria for common cements, 

2009 

12


13 

Annex 1 

2. In the dust removal system, which usually works on the principle of electrostatic precipitation 

and comprises a number of stages (cells), the fly ash is separated from the flue gas and 

removed. 

3. Monitoring of fly ash quality – assuming it is intended for high-grade use – takes place 

between the dust removal unit and the interim storage silos. The combustion process is 

controlled and material sorted depending on the monitoring findings. 

4. On the basis of the results, the fly ash is stored in different silos depending on its quality 

(compliance or non-compliance with standards). From there it is transported to the place of 

use by road, rail or water. - If the power plant is equipped with only one silo the decision 

whether the fly ash in the silo is a fly ash according to EN 450 is taken on the results of the 

internal quality control. 

The combustion process is fully controlled to meet stringent emission control parameters as well 

as to meet the requirements resulting from European standards for conformity evaluation of the 

products. Figures 2 shows the responsibilities of the producer for e.g. fly ash for concrete 

according to the European standard EN 450-2 5 (formerly national standards). 

production 

control 

= 

internal 

quality 

control 

+ 

autocontrol 

testing 

Fig 2 Production control for the production of fly ash for concrete according to EN 450-2 4 

The complete combustion process has to be described in a works quality manual and the 

process is monitored by an officially recognized monitoring body (third party control). A similar 

system for conformity evaluation is required by the European standard for lightweight aggregate 

(see page 4). 

5 EN 450-2: Fly ash for concrete - Part 2: Conformity evaluation, 2005 


scope of the production control according to EN 450-2 

= responsibility of the producer / owner of certificate 

boiler 

responsibility 

power plant operator 

DENOX 

KAT 

internal 

quality 

control 

- fineness 

-LOI 

ESP 

fly ash 

silo 1 

Q I 

EN 

450 

FGD 

non 

EN 

450 

stack 

silo 2 

Q II 

auto-control 

final product 

testing 

fly ash 

responsibility producer 

13




14 

Annex 1 

Fly ash is a fine grained dust consisting mainly of melted vitreous particles of spherical shape 

with a smooth surface. Depending on the fuel used, a distinction is made between siliceous and 

calcereous fly ash. The principal components are silica, aluminium and iron compounds, and 

also – in calcereous fly ash – calcium oxide or calcium compounds. The composition of 

siliceous fly ashes corresponds to that of naturally occurring pozzolans (volcanic ashes), while 

calcereous ashes also contain hydraulically active mineral phases in addition to pozzolanic 

components. A special property of siliceous fly ash is its pozzolanic reactivity, i.e. its capacity to 

react with lime and water at ambient temperature to form strength-giving mineral phases similar 

to those in Portland cement. In view of its fineness and particle size distribution, and also its 

pozzolanic reactivity, coal fly ash is mostly used in cement-bound building materials to improve 

their technical properties and replace cement. 


In 2008, about 38 million tonnes of fly ash from lignite and coal combustion were produced. 

Most of the fly ash from lignite combustion (about 17 million tonnes) is used for reclamation of 

open cast mines, pits and quarries. 

About 18 million tonnes of fly ash was used in the construction industry and in underground 

mining, i.e. as concrete addition, in road construction and as a raw material for cement clinker 

production. Fly ash was also utilised in blended cements, in concrete blocks and for infill (that 

means filling of voids, mine shafts and subsurface mine workings) (see figure A2 in Annex I). 

Typical uses for fly ash, together with details of the quality requirements it must meet for these 

uses, include: 

• as addition to concrete according to EN 206-1 6 

Fly ash is used as a concrete addition in various proportions depending on the individual 

mix design, and improves the properties of concrete, e.g. by reducing the heat of 

hydration, improving durability, increasing resistance to chemical attack. To some extent 

it replaces cement, enabling the content of the latter to be reduced in concrete 

accordingly. For this application fly ash has to be produced according to EN 450-1 7 and 

EN 450-2 8 . 

• in road construction: according to national regulations. 

In addition to its use in concrete layers, fly ash is used in bituminous surface layers and 

in hydraulically bound road bases. The relevant quality requirements are set out in 

instruction sheets and technical requirements issued by national authorities or by 

European or national standards (i.e. EN 13282 9 ) 

• for cement production 

Fly ash is used as a raw material component (clay substitute) in cement clinker 

production or as a main constituent in the production of Portland fly ash cement or 

Portland composite cement. In the first case site specific requirements of the cement 

producer has to be met, for the production of blended cement the requirements in EN 

197-1 10 . 

• for concrete blocks: national regulations 

6 

EN 206-1: Concrete – Part 1: Specification, performance, production and conformity, 2000 

7 

EN 450-1: Fly ash for concrete - Part 1: Definition, specifications and conformity criteria, 2005 

8 

EN 450-2: Fly ash for concrete - Part 2: Conformity evaluation, 2005 

9 

EN 13282: Hydraulic Road Binders, Composition, specifications and conformity criteria, 2009 

10 

EN 197-1: Cement - Part 1: Composition, specifications and conformity criteria for common cements, 

2009 

14


15 

Annex 1 

• for infill, that means filling of voids, mine shafts and subsurface mine workings according to 

national regulations of the mining authorities 

• for production of bricks (leaning of fatty clay): national regulations 

• in earthworks and landscaping 

In earthworks and landscaping the mechanical properties of fly ash are used in setting up 

and improvement of road foundations (embankments), the construction of noise barriers, 

and for recultivation and soil improvement. 

• for production of mortar, floor screed and plasters and mining mortars/civil engineering 

products: national standards and requirements 

In line with the energy demand curve and the seasonal working load of coal-fired power 

stations, fly ash is largely produced during the colder months of the year when business in the 

building industry is slack. Silos with a capacity of up to 60,000 tonnes have therefore been built 

at some power plants to provide dry temporary storage facilities for fly ash prior to its use as a 

concrete addition. In some cases, certified fly ash in particular is stored in a moistened state 

during the winter months, before being re-dried in separate facilities in the summer months for 

subsequent use in the building materials industry. 

2.3 Boiler Slag 


Boiler slag is produced when coal is burned in slag-tap furnaces. In such furnaces the ash 

components are drawn off in a molten state at very high temperatures (1500 - 1700°C) and 

subjected to sudden quenching in a water bath (see figure 3). The individual process steps are: 

1. Pulverized coal is blown by a transporting air stream into the combustion chamber of the 

power plant boiler. 

2. In the combustion chamber, temperatures of over 1500ºC lead to liquid slag which is 

discharged at the bottom of the boiler. 

3. The flue gas containing the fly ash flows through the boiler passes and also, if present, the 

denitrification unit and economizer, and is then fed to the dust removal unit. In the dust 

removal system, which usually works on the principle of electrostatic precipitation and 

comprises a number of stages (cells), the fly ash is separated from the flue gas and either 

conveyed to fly ash storage silos or fed back to the boiler. 

4. The sudden quenching of the molten material flowing from the melting chamber into the 

water bath results in the formation of typical glassy (amorphous) grit-like granules. 

5. The boiler slag granules are transported from the water bath to the dewatering unit, via a 

special filter bed if necessary. 

6. After any necessary processing in the form of grading and breaking, the dewatered material 

is conveyed to the in-plant storage area. From here it is transported in batches to the 

intended uses. 

Samples for quality monitoring are usually taken direct from the loading equipment at the 

temporary storage facility. The nature and extent of the quality monitoring depend on the 

intended use of the vitrified slag. 


Boiler slag is a glassy material, has a broken particle shape due to the production process, and 

has a particle size of 0.2 to 11 mm. Special features of the granules are their low apparent 

density and installation weight, high angle of friction, excellent frost resistance, lack of sensitivity 

to environmental influences, high permeability and good filtering effect when used in beds. 


15


16 

Annex 1 

The properties of processed boiler slag meet the requirements of normal size fractions, such as 

0/5 high quality broken sand (natural sand classified for grain diameter of 0 to 5 mm). 

Boiler slag does not contain any organic impurities. All trace elements are firmly and 

permanently embedded in the glass matrix. Systematic tests have shown that leaching of 

vitrified slag does not release any substances harmful to the environment. 



The chemical, physical and mechanical properties of boiler slag and its compliance with the 

relevant standards, guidelines and regulations are crucial to its use. For some uses, further 

processing of the material by breaking or screening makes it more uniform. 

In 2008, about 1.4 million tonnes of boiler slag were produced in Europe (EU 15). The utilisation 

rate was 100 %. About 45 % was used as blasting grit, about 30 % in road construction, 10 % 

was used as aggregate in concrete and about 5 % for grouting and drainage (see figure A3 in 

Annex I). 

Typical uses for boiler slag, together with details of the quality requirements it must meet for 


• for road construction: national regulations 

Boiler slag is used in road pavement, as bed material and joint pinning, infill of rural tracks, 

car parks and pathways. 

• as blasting grid for surface treatment of metal and concrete 11 

• for concrete production : EN 12620 12 and national regulations 

• for bricks: national regulations 

• in earthworks: national regulations 

Boiler slag is used for soil improvement, as filter material for drainage, as backfill material 

and as a bed material 

• in road construction: national regulations 

Boiler Slag is used for road pavement, as bed material, for joint pinning, infill of rural tracks, 

car parks and pathways. 

• for drainage material and filter course on landfill sites: national regulations 

11 ISO 11126-4: Preparation of steel substrates before application of paints and related products - 

Specifications for non-metallic blast-cleaning abrasives - Part 4: Coal furnace slag, 1998 

12 EN 12620: Aggregates for concrete, 2008 


Boiler 

NH 3 

DENOX 

ESP 

Boiler Slag 

feed of Fly Ash 

Fig. 3 Production of Boiler Slag 

Lime 

FGD 

Chimney 

FGD Gypsum 

16


2.4 Fluidized bed combustion (FBC) ash 



17 

Annex 1 

Fluidized Bed Combustion (FBC) ash is produced in fluidized bed combustion boilers. The 

technique combines coal combustion and flue gas desulphurisation in the boiler at combustion 

temperatures of 850 to 900°C (see figure 4). The individual process steps are: 

1. Pulverized coal and milled limestone for desulphurisation is fed to a fluidized bed 

combustion boiler. The fluidized bed consists of sand like material which is fluidized by 

addition of air from the bottom of the boiler. 

2. In the fluidized bed coal and limestone are intimately mixed and heated up to a temperature 

of 850 to 900°C. By this, the coal is burned, the limestone is decomposed and reacts with 

the sulphur from coal combustion. 

3. The minerals formed by coal combustion differ in size and density. The bigger particles are 

removed from the fluidized bed as bed ash, the finer particles leave the firing chamber with 

the flue gas, also the flue gas desulphurization products and unreacted adsorbens. In the 

dust removal system, either cyclones, baghouse filters or electrostatic precipitators, fly ash is 

collected and conveyed to storage silos or mixed with the bed ash and stored in silos or 

interim storage sites. 

FBC ash is stored temporarily before undergoing final controls and being transported to the 

place of use, usually by road. 

Fig. 4 Production of FBC ash 


Lime 


Bed material 

Furnace 

850 – 

900°C 

Bed Ash / 

Bottom Ash 

Bed cooling 

Fly Ash 

Depending on the desulphurisation process in the furnace FBC ash, as a mix of bed ash and fly 

ash, consists of coal ash, residual coal, desulphurization products and non reacted adsorbent. 

The comparatively low combustion temperature lead to formation of fine grained crystalline 

minerals. The maximum grain size is up to 10 mm stemming from bed ash particles. The ash is 

rich in lime and sulphur due to the combined desulphurisation process. Other main chemical 

constituents are silicon, aluminium and iron oxide. 

Cyclone 

ESP 

17




18 

Annex 1 

The amount of FBC ashes produced in Europe (EU 15) was about 1.0 million tonnes in 2008. 

The production has to be considered small compared to the production in Poland and the Czech 

Republic. In 2008, about 0.2 million tonnes of the FBC-ash produced in EU 15 member states 

was used for engineering filling applications (52 %), for structural fill (11 %) and infill (9 %) (see 

figure A4 in Annex I). 

The typical uses for FBC ash, together with details of the quality requirements it must meet for 

these uses, are based on national regulations. 

2.5 SDA product 


With the desulphurisation of flue gases in European power plants using spray dry absorption 

techniques spray dry absorption product (SDA product) is generated. The desulphurisation 

process involves the following process steps within the plant: 

1. The lime suspension introduced into the spray absorber reacts with the sulphur dioxide 

(SO2) present in the flue gas. 

2. The process temperatures are adjusted so that the water present in the system evaporates 

completely and the reaction product (normally SDA product) is output in a dry state at the 

dust removal units. 

3. The finished SDA product is temporarily stored on site and transported from there to the 

user. 

Depending on the location of the SDA installation in the flue gas stream (upstream or 

downstream the electrostatic precipitator) SDA product may contain fly ash up to 60 % by mass 

(see figure 5, case I or II). This has a major influence on its further use. 

SDA product is stored temporarily in silos before undergoing final controls and being 

transported to the place of use, usually by road. 

Desulphurization (DeSO x) 


Boiler 

Bottom Ash 

Fig. 5 Production of SDA Product 

Lime 

SDA 

ESP 

Fly ash 

ESP 

Fly ash 

+ SDA product 

Lime 

SDA 

I) 

II) 

SDA product 

18


2.5.2 Composition and properties 


19 

Annex 1 

SDA product is a fine-grained powder with a particle size mostly less than 60 µm and a residual 

moisture content of less than 10% by weight. Depending on the fly ash content, its colour varies 

from white to grey. 

Owing to differences in process technology (with (II)/without (I) prior dust removal) and in the 

properties of the fuels and auxiliary agents used, the composition of the SDA product may 

fluctuate within a wide range. The SDA product is a mixture of the following minerals: calcium 

sulphite hemi-hydrate, calcium sulphate di-hydrate (gypsum), calcium carbonate, calcium 

hydroxide, calcium chloride and calcium fluoride. 


In 2007, about 0.4 million tonnes of spray dry absorption product (SDA product) were produced 

in European power plants (EU 15). No systems with spray dry absorption are in use in lignite 

power stations. The production has to be considered small compared to the production in 

Poland and Czech Republic. 

About 0.2 million tonnes of the SDA product produced in EU 15 member states was mainly 

used in filling applications (structural fill and infill). About 3 % was used for plant nutrition and 

about 20 % as a sorbent in wet FGD (see figure A5 in Annex I). 

The excellent fertilizer effect of the calcium and sulphur in SDA product is used in agriculture 

and forestry. In Germany, SDA product is listed in the Fertilizers Ordinance as a fertilizer type in 

its own right. The resulting requirements are satisfied by SDA products from systems equipped 

with prior dust removal. 

The typical uses for SDA product, together with details of the quality requirements it must meet 

for these uses, are based on national regulations. 

2.6 FGD gypsum 


FGD gypsum is produced in the flue gas desulphurisation process of coal-fired power plants 

incorporating the desulphurisation of the flue gas in the power plant (see figure 1) and a refining 

process in the FGD plant including an oxidation process followed by gypsum separation, 

washing and dewatering. 

The process involves the following sequence of process steps within the plant: 

1. The suspension containing limestone/chalk (CaCO3) or quicklime (CaO) which is sprayed 

into the flue gas scrubber reacts with the sulphur dioxide (SO2) present in the flue gas to 

form mainly calcium sulphite (CaSO3). This results in a liquid mixture, the solid 

components of which are calcium sulphite and the calcium sulphate circulated in the 

scrubber cycle. 

2. Calcium sulphite is oxidized by adding defined quantities of air, and in the subsequent 

crystallization process it binds two molecules of water; this results in a suspension of 

gypsum (calcium sulphate dihydrate: CaSO4 ⋅ 2H2O) in the scrubber sump. 

3. In the further course of the process the gypsum suspension, which is monitored internally 

to track its chemical and physical properties, now passes through hydrocyclones where 

partial dewatering takes place and the gypsum particles are graded. The fine material is 

returned to the flue gas scrubber. 

19


20 

Annex 1 

4. Further dewatering and purification of the gypsum with leaching of water-soluble 

components (e.g. chloride) takes place either in a centrifuge or on a belt-type vacuum 

filter. The washing water undergoes further reprocessing in a separate unit. The residual 

moisture content of FGD gypsum (excluding bound crystal water) is between 5 and 12%. 

5. The finished FGD gypsum, which may be dried first, goes to an on-site interim storage 

facility (silo, hall). From there it is transported to the user by water, road or rail. (A certain 

amount of the FGD gypsum produced in Germany goes to raw material depots to ensure 

continuous long-term supplies to the gypsum industry.) 

The quality of the gypsum is monitored daily. The samples are taken immediately before the onsite 

interim store. The laboratory tests are performed in accordance with the instruction sheet 

“FGD gypsum – Quality Criteria and Analytical Methods” 13 and any additional parameters 

agreed between producer and customer. 


FGD gypsum is a moist, fine-grained material with a residual moisture content of 5 to 12 % and 

at least a 95 % concentration of CaSO4 ⋅ 2H2O. Depending on the production conditions, the 

gypsum crystals are needle-shaped to compact and plate-like. 

The composition and properties of FGD gypsum are identical to those of natural gypsum, as 

has been proven by extensive basic scientific research 14 . 


The amount of FGD gypsum produced in Europe (EU 15) was approximately 11 million tonnes 

in 2008. More than 80 % of the total FGD gypsum produced in Europe is utilised in the gypsum 

and cement industry. In total, about 3 % of the FGD gypsum produced was temporarily 

stockpiled as a raw material base for future utilisation, mostly for plasterboard production, and 

about 7 % was disposed of. 

FGD gypsum is used as a raw material for a number of gypsum products by the gypsum 

industry because of its purity and homogeneity compared to natural gypsum. 5.6 million tonnes 

of FGD gypsum was used in 2008 for the production of plaster boards. Other applications 

include the production of gypsum blocks, projection plasters and self levelling floor screeds (see 

figure A6 in Annex I). 

Like natural gypsum, FGD gypsum has to be dewatered by thermal means before being used 

for building materials, and in this process the crystal water is completely or partially removed. 

Before the gypsum product is used on the construction site or at the gypsum works, water is 

added to it again, starting a controlled setting process. 

FGD gypsum is also used as a retarder in cement production and as a filler in the production of 

paints, adhesives and plastics. Further application exist in agriculture, where FGD gypsum is 

used as a source of lime and sulphur in fertilisers, composts and soil improvers. 

13 EUROGYPSUM: FGD Gypsum - Quality Criteria and Analysis Methods (status: April 2005). 

14 Becker, J., Einbrodt, H.-J., Fischer, M.: Vergleich von Naturgips und REA-Gips, Bericht und gutachterliche 

Stellungnahme, VGB Forschungsstiftung und Bundesverband der Gips- und Gipsbauplattenindustrie 

e.V., 1989. 

(see also: Becker, J., Einbrodt, H.-J., Fischer, M.: Comparison of Natural Gypsum and FGD Gypsum, 

Abridged version of VGB Research Project 88, VGB Kraftwerkstechnik 1/1991, p. 46-49 


20


21 

Annex 1 

Typical uses for FGD gypsum, together with details of the quality requirements it must meet for 


• for use as a raw material for the gypsum and cement industry: FGD Gypsum Quality 

Criteria 15 

• for the use as fertiliser: national regulations. 

3. Conclusion 

In Europe (EU 25), more than 100 million tonnes of by-products were produced in coal-fired 

power stations in 2008; of this total, about 56 million tonnes was produced in the EU 15 

countries. The by-products include boiler slag, bottom ash and fly ash from different types of 

boilers as well as desulphurisation products like spray dry absorption product and FGD gypsum. 

Out of the total production of 56 million tonnes of by-products in EU 15, the amount of ash 

produced was around 44 million tonnes, while around 12 million tonnes are products obtained 

from flue gas desulphurisation processes. 

The by-products are mainly utilised in the building material industry, in civil engineering, in road 

constructions, for construction work in underground coal mining as well as for recultivation and 

restoration purposes in open cast mining. Most of the hard coal fly ashes are used in cement 

and concrete. 

In the majority of cases by-products are used as a replacement for natural materials and 

therefore offer environmental benefits by avoiding the need to quarry or mine these resources. 

By-products also help to reduce energy demand as well as emissions to atmosphere, for 

example CO2, which are needed for - or result from - the manufacturing process of the products 

which are replaced. 

All by-products are produced in a fully controlled combustion and/or desulphurisation process. 

The majority of the by-products is produced to meet certain requirements of standards or other 

specifications with respect to utilisation in certain areas. To meet the demand of the customers 

by-products may have to be stored for a certain interim period or processed. Interim storage is 

necessary because by-products are produced in wintertime when construction work is rare. 

Storage facilities guarantee stable product qualities until final use. For special products also 

processing of by-products may be required to allow the benefit of specific by-product use also in 

products with special properties. 

15 EUROGYPSUM: FGD Gypsum - Quality Criteria and Analysis Methods (status: April 2005) 


21


Concrete 

Blocks 

Figure A1: 

Utilisation of Bottom Ash in the Construction 

Industry and Underground Mining in Europe 

(EU 15) in 2008. 

Total utilisation 2.4 million tonnes. 

Blasting 

Grit 

Figure A3: 

Utilisation of Boiler Slag in the Construction 

Industry and as Blasting Grid in Europe (EU 

15) in 2008. 


Structural 

Fill 

44.5% 

37.0% 

56.6% 

Figure A5: 

Utilisation of SDA-Product in the Construction 

Industry and Underground Mining in 

Europe (EU 15) in 2008. 



41.2% 

10.6% 

30.4% 

19.6% 

15.5% 

Road Construction, 

Filling Application 

Cement/ 

Mortar 

Concrete, 2.7% 

Others 

9.6% 

20.4% 

4.9% 

3.4% 

Others, 1.8% 

Concrete 

Grouting, 

Drainage 

Road 

Construction 

Infill 

Plant 

Nutrition 

Other uses 

(wet FGD, ...) 

Blended 

Cement 

Concrete 

Addition 

13.9% 

Cement 

Raw Material 

32.6% 

21.8% 

5.5% 

22.7% 

22 

Annex 1 

Annex I 

Concrete Blocks 

Infill, 2.5% 

Others, 1.0% 

Road 

Construction, 

Filling 

Application 

Figure A2: 

Utilisation of Fly Ash in the Construction 


(EU 15) in 2008. 


General 

Engineering 

Fill 

Infill 

52.6% 

9.2% 

18.5% 

11.0% 

5.8% 

Structural 

Fill 

Subgrade 

Stabilisation 

Cement, 2.9 % 

Other Uses (sludge treat- 

ment, waste stabilisation,..) 

Figure A4: 

Utilisation of FBC Ash in the Construction 


(EU 15) in 2008. 


Plaster 

Boards 

62.8% 

9.2% 

17.4% 

7.2% 

Gypsum Blocks, 3.4% 

Self Levelling 

Floor Screeds 

Set Retarder 

Projection Plaster 

Figure A6: 

Utilisation of FGD gypsum in the Construction 

Industry in Europe (EU 15) in 2008. 


22

The Classification of Coal Combustion Products under - Eurelectric

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