Environment

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Disposal and Recycling Routesfor Sewage Sludge

Synthesis report22 February 2002

European CommissionDG Environment � B/2

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Foreword

This report has been produced by Philippe Aubain, Alexis Gazzo, Jan Le Moux and Eric Mugnier fromANDERSEN (Environment Risk Consulting Department), by Hubert Brunet and Benoît Landrea fromSEDE, on behalf of the European Commission.

We would like to thank the members of the Steering Committee for their guidance:

Sonia Fumagalli (DG ENV/B2), Luca Marmo (DG ENV/A2), Pierre Strosser (DG ENV/B2).

We would also like to thank the persons contacted during the course of this study, for their availabilitydespite their extensive professional commitments. The full list of contributors is provided in theappendices of each sub-component report.

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Contents

1. INTRODUCTION ...................................................................................................... 4

2. SCIENTIFIC AND TECHNICAL ANALYSIS ............................................................ 6

3. REGULATORY ANALYSIS.................................................................................... 14

4. SLUDGE USE ACCEPTANCE ANALYSIS............................................................ 16

5. ECONOMIC ANALYSIS ......................................................................................... 21

6. CONCLUSION........................................................................................................ 25

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1. Introduction

1.1 BackgroundThe Commission is thinking of revising the existing Sewage Sludge Directive (Directive86/278/EEC). The revision will take account of the latest technical developments in waste watertreatment, of the recent research results on the effects of heavy metals on soil and soil micro-organisms, of the risk of animal and human contamination by pathogens contained in sludge, andof the concerns expressed by the agro-food industry and large retailers about the safety of usingsludge in agriculture and envisages an extension of the scope to non-agricultural uses.

1.2 Objectives of the studyThe aim of the study is to review current scientific knowledge on the biophysical processes andflows of substances and elements that take place within the "sludge system", and assess theenvironmental and economic impact of the main disposal and recycling routes for sewage sludge.This study aims to:

• review the scientific evidence on the migration and accumulation of substances and elementsin the "sludge system" (scientific and technical report);

• assess the adequacy of existing legislation dealing with such risks (regulatory report);

• perform an economic analysis of the main disposal and recycling routes for sludge (economicreport);

• investigate the main factors that limit the use of sludge in the different disposal and recyclingroutes (sludge use acceptance report);

The study covers the fifteen Member States of the European Union and, to a large extent, theAccession Countries.

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1.3 Intervention methodologyAs described below, work consisted in two phases:

We delivered four separate reports covering the four aspects of sludge recycling and disposal,which executive summaries are presented in the following pages:

• Scientific and technical report ;

• Regulatory report;

• Sludge use acceptance report;

• Economic report.

� Data collection (studies, articles, statistics)� Contact with key informants (Ministries, research bodies, water

operators, industries, etc.)

� Information review� Steering Committee review

Data collection

� Technical analysis� Steering Committee review

� Legal analysis of existing legislation� Steering Committee review

� Identification of the main factors restricting the use of sludge in thedifferent disposal and recycling routes

� Steering Committee review

� Economic analysis of the main disposal and recycling routes� Steering Committee review

� Final synthesis report and sub-component reports

Analysis

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2. Scientific and technical analysis

Sludge composition and treatmentSludge is composed of by-products collected at different stages of the wastewater treatment process. Itcontains both compounds of agricultural value (including organic matter, nitrogen, phosphorus andpotassium, and to a lesser extent, calcium, sulphur and magnesium), and pollutants which usuallyconsist of heavy metals, organic pollutants and pathogens. The characteristics of sludge depend on theoriginal pollution load of the treated water and also on the technical characteristics of the wastewaterand sludge treatments carried out.

Sludge is usually treated before disposal or recycling in order to reduce its water content, itsfermentation propensity or the presence of pathogens. Several treatment processes exist, such asthickening, dewatering, stabilisation and disinfection, and thermal drying. The sludge may undergo oneor several treatments.

Sludge recycling or disposal routesOnce treated, sludge can be recycled or disposed of using three main routes: recycling to agriculture(landspreading), incineration or landfilling. Other, less developed outlets exist, such as silviculture, landreclamation, and other developing combustion technologies including wet oxidation, pyrolysis andgasification. Each recycling or disposal route has specific inputs, outputs and impacts.

LandspreadingLandspreading of sludge or sludge-derived material partially replaces the use of conventional fertilisers,since it contains compounds of agricultural value. It also contains organic matter, although under a formand at a level below that which would have a significant positive impact on soil physical properties.Composted sludge however presents a more stable organic matter due to the addition of a vegetal co-product during the process.

However, landspreading also involves the application of the pollutants contained in sludge to the soil.These pollutants undergo different transformations or transfer processes. These processes includeleaching to groundwater, runoff, microbial transformation, plant uptake and volatilisation and enabletransfer of the compounds into the air and water, and their subsequent introduction into the food chain.

Therefore outputs of sludge recycling consist of yield improvement, but also of emissions of pollutioninto the soil, and indirect emissions into air and water. Other emissions into the air include exhaustgases from transportation and application vehicles.

IncinerationIncineration is a combustion reaction. Different techniques are currently performed, classified betweenmono-incineration when sludge is incinerated in dedicated incineration plants, incineration with otherwastes, or co-incineration when sludge is used as fuel in energy or material production. Othertechnologies are also being developed such as wet oxidation or pyrolysis.

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Outputs are flue gases, ashes, and wastewater, as well as the production of energy. Thereforeincineration generates emissions into the air (particles, acid gases, greenhouse gases, heavy metals,volatile organic compounds, etc.), soil (disposal of ashes and flue gas treatment residues to landfill,atmospheric deposition of air emissions) and water (flue gas treatment wet processes). Emissions intothe air may be reduced thanks to flue gas treatment. Emissions depend on the process, but are alsoinfluenced by the sludge type. Energy production generally counterbalances the energy needs for sludgedrying.

Operation of an incineration plant may also produce noise, dust, odour and visual pollution.

LandfillingThere are two possibilities in terms of sludge landfilling: mono-deposits, where only sludge is disposedof, and mixed-deposits (most commonly observed), when the landfill is also used for municipal wastes.

The inputs of landfilling are the waste and additional resources required for the operation of the landfillsite, such as fuel for vehicles, electricity, and additional materials when leachate is treated on-site.Outputs consist of leachate, landfill gas and energy production when the gas is recovered.

Landfill operation therefore generates emissions into the air (mainly greenhouse gases like methane andcarbon dioxide, reduced when biogases are collected and burnt), and into the soil and water at dumpsites(various compounds such as ions, heavy metals, organic compounds and micro-organisms in leachate).The operation of a landfill also generates other impacts in terms of noise and dust from the deliveryvehicles, as well as odours, land use, disturbance of vegetation and the landscape.

Other routesOther sewage sludge recycling routes presently used in Europe include the use of sludge in forestry andsilviculture or in land reclamation.

Forestry and silviculture refer to different kinds of tree plantation and use. The term forestry is mainlyused when considering amenity forests, or mature forest exploitation. On the contrary, silviculture ismore specifically used when referring to intensive production. From the agricultural and environmentalpoint of view, differences exist in terms of the impact of landspreading as compared to the use of sludgein forestry, relating to such factors as the plant species grown, the fauna and flora involved, and the soiltypes.

Agronomic benefits are increased tree growth and the provision of nutrients to the soil. However,competition with weeds, especially in young plantations may be observed. Excessive rates of sludgeapplication may also lead to degradation of the upper layer of the soil and the humus, as well as nitrogenleaching to groundwater. The use of sludge in a forest environment may cause an alteration in thecharacteristics of the ecosystem and, in the case of a mature forest where there is no need to have anadditional input of nutrients, may disturb the natural biotopes. More research is however needed on thisissue.

When considering the risks to humans associated with the presence of heavy metals in sludge, it isassumed that these are lower than those associated with spreading on agricultural land, as forestproducts represent only a very small part of the human diet. However, some risks may still exist due tothe transfer of heavy metals to game or edible mushroom species and in a general manner to wild faunaand flora.

After identifying gaps in knowledge, some recommendations are given in this report concerning sludgeapplication in forest or tree plantations.

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Use of sewage sludge in land reclamation and revegetation aims to restore derelict land or protect soilfrom erosion through soil provision and increased vegetal covering. In the case of industrial sites,topsoil may often be absent or if present, damaged by storage or handling. Soil or soil forming materialson site may be deficient in nutrients and organic matter. Other problems may exist, such as toxicity, oradverse pH levels. All these problems create a hostile environment for the development of vegetation.

Possible solutions include the use of inorganic fertilisers or imported topsoil, which can be veryexpensive depending on location and availability. An alternative solution is the use of organic wastessuch as sewage sludge, which is already performed in Sweden, Finland, Germany and the UnitedKingdom.

Sludge application takes place using the same machinery as in recycling to agriculture. Some specificmachinery for sludge projection may be needed when applying sludge in areas where access is difficult.

It was assumed that risks are lower than in the case of spreading on agricultural land, when its use is notrelated to food production. However, no data is available concerning the potential impacts on wild faunaand flora. Moreover, the amount of sludge applied as well as the application of sludge to sloping land toreduce erosion go against current regulatory prescriptions for the use of sludge in agriculture, inducingrisks in terms of pollutants application.

Developing technologiesSeveral technologies presenting an alternative to conventional combustion processes are currently beingdeveloped or introduced onto the market. These technologies mainly include by the wet oxidationprocess, pyrolysis, and the gasification process. Other technologies may be found, which are most oftencombinations of these three main processes.

These technologies present advantages in terms of flue gas and ash treatment. Moreover, they also seemto have reduced impacts on the environment compared to conventional combustion processes.

Pollutants transferA review of current scientific knowledge concerning pollutants transfer mechanisms in the differentenvironment media and the food chain has been carried out in order to assess the possible impacts on theenvironment and human health.

Each route has specific transfer processes, but transfers relating to landspreading covers most of thesignificant transfers relating to the other routes, with the exception of air emissions.

Heavy metalsThe presence of numerous metals in soil and sludge has been reported in the literature. Once applied tothe soil they are distributed between the different soil media. Scientific evidence shows that theyaccumulate in the upper layers of the soil, due to binding to the different existing organic or mineralparticles. Their mobility and biovailability to plants and micro-organisms may be influenced by severalfactors of which the pH level of the soil is the most important. Heavy metals are naturally present in soilat varying levels, and may originate from several anthropogenic sources such as fertilisers, animalmanure, sludge, or atmospheric deposition. However, variety in the metal levels in European soils mayalso be due to the diversity of the extracting methods used rather than differences in the field. In order toensure the quality of the comparisons, a harmonisation of the sampling and measurement methodswould be required.

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Micro-organisms species present in the soil are numerous. Some of them are important for soil fertilityand therefore for agricultural production. Concern has been expressed about the consequences of metalprovision to the soil on the micro-organisms population and biodiversity. Available scientific literatureshows contradictory results, depending on the species taken into consideration, the local conditions ofthe experiments, and the confusion of short-term laboratory experiments with long-term field trials.Some authors mentioned the ability of microbial populations to adapt to changing conditions, whichmay be considered a result of negative pressure on the population. On the basis of long-term field trials,some studies concluded that soil micro-organisms� diversity and population could be negatively affectedby sludge-borne metals in the long-term, and by metal levels in soil which were in some cases belowcurrent regulatory prescriptions. It must also be stressed that microbial activity indicators must not beused as the only indicators of microbial reaction to metal application, as they do not reflect changes inpopulation structure.

Leaching to groundwater appears to be a negligible phenomenon. On the contrary, runoff, when itoccurs, may play a significant role in metal transfer. Its importance depends greatly on the localsituation, and the fate of metals needs to be further documented.

Plant uptake occurs for all heavy metals and is described by transfer factors. Some metals (e.g. copperand zinc) are of biological importance for the plant. It has been observed that heavy metals areconcentrated in the roots and vegetative parts of plants and are less present in the generative parts suchas wheat grain. Uptake will increase with increasing metal levels in soil, but only applies to thebioavailable part of the metals present in soil. However there may be no direct relation between totalmetal concentration and bioavailable metals in soil. pH is the most important factor influencing metaluptake. In particular, a decrease in the pH value in soil in the range of pH 7 to pH 4 causes an increasein the uptake of Cd, Ni and Zn. The same effect is observed for Cu, but is less marked. Lastly, whenconsidering usual acidity levels in agricultural soils, a pH decrease had no observed effect on Pb and Cruptake. This information supports the setting of different limit values for Cd, Ni and Zn, and possiblyfor Cu, for soil with pH values of between 5 and 7 as well as for soil with pH values of higher than 7.Sludge spreading should also be avoided on soil with a pH value below 5 and limit values should referto the bioavailable part of metals in soil rather than to the total concentration, although it is not possibleat the moment to define for all heavy metals what is the bioavailable fraction.

Uptake of metals by animals occurs through contaminated plant consumption or soil ingestion.However little information is available concerning metal quantities ingested and absorbed and theirsubsequent toxicity levels to animals. Metals do not seem to accumulate in meat. More focus is neededconcerning possible Pb and Cd transfer to offal, as in some cases this could lead to levels nearingacceptable limits in foodstuffs. Transfer of Pb and Cd across the placenta and into the milk wasobserved during indoor feeding trials, but there are likely to be few practical consequences for finishedanimals. Concentration of Cu in the milk was not influenced by the ingestion of sludge-amended soil. Aquantitative assessment of this contamination pathway is not available at the present time.

In a general manner, human exposure to heavy metals may be attributed to several sources anddepends on many factors such as diet, actual absorption, and food processing. Consumption ofcontaminated crops appears to be the main means of exposure to sludge-borne metals. It is assumed thatthe specific contribution of sludge-borne metals to the human diet is very low, when taking into accountthe observed level of metals present in soil, and considering the surface area over which sludgespreading takes place.

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Organic pollutants

Numerous organic compounds are present in sludge. Once applied to the land, they are distributedthroughout all soil media and undergo several retention and transport processes. They are physically,chemically and biologically transformed in other intermediary compounds during their mineralisation,for which no data is presently available. The degradation pathway of the organic compounds and thusthe duration before reaching negligible concentration in soils may greatly depend on the aerobic oranaerobic degradation conditions.

Leaching of organic pollutants to ground water appears to be insignificant but, unlike metals, cannotbe neglected in some cases. The importance of this mechanism depends on the properties of thecompounds and the soil. It appears on the one hand that many compounds present short half-life values,reducing the risk of leaching to groundwater. On the other hand, persistent compounds such asPCDD/Fs or PCBs show an affinity with soil particles and will therefore bind to soil rather than leach toground water. Runoff, when it occurs, may play an important role in the transfer of organic compounds.

Even if definitive evidence is lacking, it appears that soil micro-organisms are not affected by sludge-borne organic pollutants in most cases and that they are able to adapt to changing conditions.

Most organic pollutants are not taken up by plants. However, a risk of contamination of the food chainexists when spreading sludge directly onto crops, especially on plants which are to be consumed raw orsemi-cooked.

Soil and sludge ingestion on land used for grazing is the main route for animal contamination.Accumulation of bioaccumulative compounds such as PCDD/Fs, PCBs or PAHs may occur in meat andmilk. However, it is presently not possible to assess the quantities and fates of organic compoundsingested by animals.

It appears that the consumption of animal products is the major source of human exposure to sludge-borne organic pollutants, due to the ingestion of soil by livestock. As in the case of heavy metals, it isassumed that the specific contribution of sludge-borne organic pollutants to the human diet is very low,when considering the reduced proportion of the utilised agricultural area onto which sludge spreadingtakes place.

Lastly, it should be noted that at the present time no universally accepted and validated analyticalmethod exists for analysing most organic compounds. There is also a lack of data concerning levels oforganic pollutants in European sewage sludge as no regular survey has been performed in the past.

Therefore, considering presently available knowledge on organic compounds, it appears at the presenttime, that:

• transfer to water is low, micro-organisms adapt to changing conditions in soil, and numerous organiccompounds are rapidly degraded in soil. Attention should therefore mainly be given to compoundswith higher half-life time values,

• from the point of view of crop protection, no limit value seems to be necessary as transfers to plantdo not occur for most organic compounds,

• restrictions should focus on bio-accumulative compounds spread on grazing land such as PCBs andPCDD/Fs. In this case deep injection of sludge could reduce the risk of livestock contamination byorganic pollutants,

• a survey of organic pollutant levels in sludge should be performed by sludge producers, focusing onthe specific organic pollutants identified within the waste water catchment area of the WWTP.

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PathogensThere are five main types of pathogens observed in sludge: bacteria, viruses, fungi and yeast, parasiticworms, and protozoa. Humans and animals are sensitive to some of these organisms, which may causenumerous pathologies ranging from simple digestion troubles to lethal infections.

Sludge-borne pathogens are mainly present on the soil surface or at shallow depths where sludge hasbeen ploughed into the soil. Pathogen penetration depends on the effective depth of the soil, its texture(particularly its clay content), its organic matter content and also on possible cracks, prolonged drought,faults or absence of vegetation.

Survival of pathogens in soil depends on numerous direct or indirect factors. Indirect factors are climaticfactors such as sunlight, temperature, desiccation or pH, characteristics of the soil (texture, moistureetc.), quantity of sludge spread, the pathogen content of the sludge, its organic content and the eventualpresence of competing organisms. Direct factors are related to the biological characteristics of thepathogen, and especially to the form under which it may survive. Parasites� eggs or cysts are the longestsurvivors � one to two years in certain favourable circumstances. Depending on the conditions and theorganisms themselves, survival periods may vary from a few days to several years. The pathogenicagent population decreases faster when the sludge is spread on the soil surface rather than when it isploughed into it.

Transfer to groundwater is only assumed to occur in some particular cases, while surface watercontamination is more likely to occur when runoff water transports pathogens which are bound to soilparticles.

Survival on plants is shorter than in soil, due to the effects of desiccation and sunlight.

Transmission to grazing domestic and farm animals takes place via ingestion of contaminated feedand soil.

Humans can mainly be affected by consuming raw or semi-cooked contaminated vegetables or meat.

Therefore the risks of sewage sludge application onto the land � that may be addressed by goodpractices � have to be taken into account as pathogens are present in sludge and may have significantimpacts on humans and animals. In general, deep injection or ploughing down may be recommendedduring or after sludge application. Although those practices reduce the deleterious effect of weather onmicro-organisms, contact with animals, wildlife and humans as well as dissemination into theenvironment will be reduced.

Sewage sludge may also contain plant pathogens, as well as weed seeds. They mainly originate fromwashing of vegetable and fruit, or from road or roof runoff after aerial deposition. Plant pathogens havein general low optimum growth temperature, so that disinfection will be achieved at a lower temperaturethan for mammalian pathogens.

Pollutants transfer modellingBased on the description of the transfer mechanisms of different sludge-borne pollutants in theenvironment, a model was developed in order to assess:

• the transfer of pollutants in soil (in particular due to runoff and leaching),

• the transfer of pollutants to plants in order to make a comparison with limit values in foodstuffs,

• the accumulation of pollutants in the soil,

• the time before reaching a given limit value of pollutants in soil.

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Only heavy metals are taken into consideration. Knowledge concerning organic pollutants does notenable accurate calculations to be made as very little is known about their behaviour and degradationpathways in soils (moreover, it appears that organic pollutant transfer to plants is negligible and that thisparticular route should not involve a significant human health risk). It is not relevant to apply suchcalculations to pathogens.

Two scenarios are examined, which represent two extreme situations of low and highaccumulation. Several assumptions were necessary in order to perform the calculation. Therefore theresults are indicative values, and are not supposed to be used neither individually, or withoutindicating the hypotheses used.

The main results can be summarised as follows:

• on a one-year basis, it must be observed that pollutants brought to soil by sludge applicationrepresent a very low proportion of the amount of metals present in soil before sludge application;

• plant uptake of sludge-borne metals may vary, but always represents a minor part of the amount ofsludge-borne metals contained in soil; in the long-term, plant uptake will increase with increasingsoil concentration ;

• runoff is the main parameter in the model influencing the heavy metal accumulation in soil ;

• global plant uptake of metals present in soil always remains below the limit values for foodstuffs.However, in the worst case, it may reach a significant proportion of these limit values;

• on the contrary, uptake of metals originating only from sewage sludge application is very low, andreaches, in the worse case of our modelling, 1 % of the limit value for foodstuffs ;

• an equilibrium may be reached after several years between plant uptake and sludge application,indicating that, in some cases, a limit value for metal levels in soil would never be reached ;

• the number of years required before a limit value is reached for metal accumulation in soil wouldvary greatly between the two extreme cases considered herein: figures range from around 4,500years to over 34,000 years in the case of low accumulation, and from 20 years to around 140 years inthe high accumulation scenario.

Gaps in knowledgeToday, many uncertainties remain concerning the transfer of pollutants (especially organic pollutants) tothe environmental media and the food chain. Several issues would need to be more accuratelydocumented. Amongst these issues, the following may be mentioned:

• The importance of the runoff process in the pollutants� transfer should be assessed. Mechanismsneed to be understood, as well as quantities of pollutants concerned, and their fate.

• An issue of concern is the degradation pathway of the organic compounds in soil. Compounds maybe degraded into intermediary chemicals before total mineralisation. The toxicity and leachingpotential of these metabolites is not well known. Lysimeter and field studies should be carried out.

• Long-term impacts of heavy metals and organic pollutants, in particular on soil micro-organisms andfertility, are not well documented.

• More data is needed concerning the ingestion and absorption levels of organic compounds and, tosome extent, heavy metals by animals.

• There is also a lack of knowledge concerning the specific contribution of sewage sludge topollutants� transfers.

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• A survey of the organic pollutants� levels in sewage sludge should be performed in the MemberStates in order to gain an accurate appreciation of their occurrence. This may only be possible ifstandard analytical methods are set and broadly accepted.

• Available literature does not always enable a comparison between the different countries, as nocommon research protocol and no trans-national study has been carried out.

• More information is also needed concerning other routes for sludge recycling, such as landreclamation or use in forestry and silviculture. Research should be carried out to precisely identifythe agricultural benefits of sewage sludge spreading and its environmental and sanitary impacts(especially concerning organic pollutants for which no data is currently available). Moreover,currently available information does not enable an assessment and comparison of the benefits andrisk as regard the diversity of European forests.

• Lastly, some interesting new technologies such as wet oxidation, pyrolysis or gasification have beendeveloped. More information concerning their environmental impact and their application is needed.Tests have not always been carried out on sludge, and this issue requires further documentation.

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3. Regulatory analysis

The analysis of the existing legislation related to sludge treatment, disposal and recycling carried out inthis study shows that specific legal requirements focus principally on the use of sludge in agriculture,both at national and European level. For the moment, other uses or disposal routes for sludge generallyfall under more general laws on waste and water management.

Similarly, although several Directives have an influence on sludge management (such as Directive1999/31/EEC on the landfill of waste), the ones which have the strongest impact on sludge production,disposal and recycling, are Directives 91/271/EEC concerning urban waste water treatment and86/278/EEC on the use of sludge in agriculture. In particular, requirements set by Directive 86/278/EECare a crucial element in the management of sludge currently produced in the Member States. One of theaims of this study is therefore to compare these requirements with provisions adopted at national leveland to identify the main differences.

The most significant result of this survey is the fact that national regulations, which have beenestablished on the basis of Directive 86/278/EEC, have often introduced provisions which go beyondthe requirements of the Directive.

In particular, the limit values for concentrations of heavy metals in sludge are lower than the limitvalues specified in the Directive in a majority of countries. In five countries (Belgium -Flanders-,Denmark, Finland, the Netherlands and Sweden), the limit values for heavy metals in sludge are evenmuch lower. However, six Member States (Greece, Ireland, Italy, Luxembourg, Portugal and Spain)have implemented limit values, which are identical to those specified in Annex IB of Directive86/278/EEC.

The perspective of the revision of Directive 86/278/EEC, which could lead to the implementation ofmore stringent limit values for heavy metals in sludge, could therefore have an impact in the lattercountries, at least on the provisions to be set by national regulations (average heavy metals content insludge is in most cases well below regulatory requirements).

In addition, the regulations on sludge use include limit values for pathogens in France, Italy andLuxembourg and in a larger number of cases for organic compounds (Austria, Belgium �Flanders-,Denmark, France, Germany and Sweden), both of which are not included in the Directive.

Concerning Accession countries, regulations in Estonia, Latvia, and Poland are comparable or evenmore stringent than the Directive's current requirements on limit values for heavy metals. In the otherAccession countries, sludge use and disposal usually falls under more general laws on waste or onenvironmental protection.

For the moment, national legislations have not introduced major changes as regards the otherrequirements included in Directive 86/278/EEC on sludge use:

• concerning the type of sludge covered, the sludge regulations in Belgium, Denmark, Italy, and theNetherlands explicitly apply both to urban sewage sludge and to industrial sludge, while in France, aspecific Order applies to industrial sludge spread on land;

• in terms of obligations for treatment, France, Ireland, Luxembourg, and Sweden permit the use ofuntreated sludge under certain conditions, while Denmark, Finland, Germany, Italy, the Netherlandsand Spain have prohibited the use of untreated sludge. In other countries, there is no specific legalrequirement on this aspect;

• concerning information requirements, no major changes have been implemented in nationalregulations, although Danish regulation requires analysis of organic compounds content at least oncea year. For the moment, no certification of products or services is mentioned in existing nationalregulations.

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It should however be noted that the two voluntary agreements which have been signed on the use ofsludge in agriculture (Sweden in 1994 and the UK in 1998) include requirements for use of sludge inagriculture which are more stringent than those contained in national regulations, either in terms of limitvalues for pollutants in sludge or in terms of treatment requirements.

The analysis of the requirements contained in national regulations enables us to roughly classify groupsof countries by the severity of existing legislation, taking Directive 86/278/EEC as a reference. Thesegroups of countries are as follows:

National requirements compared to EU requirements

Much more stringent Denmark, Finland, Sweden, Netherlands

More stringent Austria, Belgium, France, Germany

(Poland)

Similar Greece, Ireland, Italy, Luxembourg, Portugal, Spain, UnitedKingdom.

(Estonia, Latvia)

The review of relevant legislation reveals that very few elements in the regulations specifically addressthe use of sludge in routes other than the recycling in agriculture (use in silviculture, on natural forest,green areas, and in land reclamation). However, use of sludge on forest soil is mentioned by theregulation on sludge use in Belgium-Flanders, Denmark, France, and Luxembourg. In addition, somenational regulations have prohibited the use of sludge on silviculture (Germany, the Netherlands) onnatural forest (Walloon region, Germany), and in green areas (Germany, the Netherlands). Significantly,the regulation in Poland includes limit values for heavy metals concentrations in sludge for use in landreclamation and on "non-agricultural soil".

Similarly, incineration or disposal to landfill of sludge is usually covered by general waste regulationson incineration or on landfill and not by specific provisions in national "sludge" regulations.

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4. Sludge use acceptance analysis

The debate on sludge recycling and disposal has recently been the target of growing interest. This is dueto the fact that some concern was expressed about the potential risks of the agricultural use of sludge forhealth and the environment as early as the beginning of the 1990s. Therefore, most of the debate onsludge has focused on this route (past and present debate on disposal routes is not focused on sludge butrelates to waste in general).

The debate on the use of sludge in agriculture originated mainly in Northern Europe at the beginning ofthe 1990s, before gaining in intensity from 1995 onwards. Analysing the context of this period is crucialto understanding the various stakeholders' attitudes, motivations and constraints concerning the use ofsludge. In particular, the recent health "scares" related to GMOs (Genetically Modified Organisms),dioxins, and BSE (Bovine Spongiform Encephalopathy, that is, "mad cow disease") have cast doubtson the safety of the food products on the markets and on the ability of existing regulations andcontrols to minimise human exposure to potential risks.

The concern expressed about food safety is also related to growing pressure on the agricultural sector,which in certain countries is considered by consumer associations or nature protection associations asbeing too focused on intensive production and not sufficiently concerned about the impact of itsactivities on health and on the environment.

The above holds true for most European countries, however, certain countries are under considerablepressure from both sewage sludge, i.e. a high rate of production per inhabitant, and from otherfertilising materials, in terms of nitrogen and phosphate content. This is one reason why the debate hasnot been the same in all countries and has been most heated in the Netherlands, Flanders andScandinavian countries.

Analysis by countryPast and current events show that it is possible to divide countries up into the following groups:

In the Netherlands and Flanders, the debate on the use of sludge in agriculture is over, as the regulatoryrequirements have prevented almost all use of sewage sludge in agriculture since 1991 in theNetherlands and 1999 in Flanders.

In countries such as Denmark and the United Kingdom, the debate is now mostly over. In Denmark,new regulations on the use of sludge in agriculture (Statutory Order no. 49 of January 20, 2000 on theApplication of Waste Products for Agricultural Purposes) have played a large part in ending the debate,as they are considered sufficiently strict to reduce risks to an acceptable level. In the United Kingdom,the debate on sludge recycling was heated until an agreement was reached in September 1998 betweenWater UK, representing the 14 UK water and sewage operators, and the British Retail Consortium(BRC), representing the major retailers. In addition, farmers' associations support the agricultural use ofsludge, both for economic and for agronomic reasons.

The cases of Germany and Sweden are special. In Sweden, a voluntary agreement was signed in 1994between the Swedish Environmental Protection Agency (SEPA), the Swedish Federation of Farmers(LRF) and the Swedish Water and Waste Water Association (VAV) concerning quality assurancesrelating to the use of sludge in agriculture. However, in October 1999 the LRF recommended that theirmembers stop using sludge because of concerns about the quality of sludge. In Germany, opinion hasrecently swung in favour of agricultural land spreading, mainly because this practice is consideredeconomically viable and it is considered that the potential risks are sufficiently reduced by the existinglegislation. However, political developments in 2001 have considerably heated the debate, which isquite high at present as some Länder support an increase of regulatory constraints on sludgelandspreading.

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In Austria, France and Walloon, a national (or regional) agreement is currently under negotiationbetween the different parties, and hence the debate is heated. The situation is particularly tense in Francewhere the farmers' unions supported, until recently, the development of the agricultural recycling ofsewage sludge, on the condition that additional quality controls and an insurance fund system were setup. The situation has now changed, as farmers' unions (the FNSEA and CDJA) have asked for a ban onthe use of sewage sludge, officially because the current methods used are not considered to be sufficientto address the risks related to the agricultural recycling of sludge.

In Finland and Luxembourg, the farming community is generally hostile towards the use of sludge forland spreading, mainly because of the pressure to use animal manure for land spreading. For example,the Finnish Union of Agricultural Producers asked for a ban on the use of sewage sludge for landspreading in 1990, and have renewed their stand against the use of sludge in agriculture in 2001.

In Ireland and Portugal, farmers support, in some cases, the agricultural use of sludge, both foreconomic and for agronomic reasons (mainly in terms of organic matter and phosphorus content),although it is difficult to obtain information on this matter. In both countries, the use of sludge seems tobe too recent an issue to generate much public debate.

In Spain, Italy and Greece, the debate remains limited, as far as can be judged from the availableinformation.

This summary of the debate mostly shows that the debate is more "advanced" in Northern Europe,but remains limited in Southern Europe. In addition, it is important to mention that the debate iscurrently heated in certain countries (Austria, Walloon, France, Germany and Sweden).

A comparison with the national legal requirements also demonstrates that "tight" legal constraints(such as very low limit values for pollutants in sludge) do not necessarily imply a greater acceptanceof the use of sludge in agriculture. The Swedish example demonstrates this best.

Finally, a major trend in the current debate on the use of sludge is clearly the increasing number ofagreements regulating the use of sludge. However, whereas voluntary agreements have proven to besuccessful in the UK, they did not prevent the current crisis in Sweden. In the City of Toulouse(France), our enquiry shows that the national agreement will possibly not allay opponents' fears relatedto sanitary risks or appease all of the local opposition: the debate largely rests on political andsociological grounds.

Analysis by stakeholderIdentifying the main positions, attitudes and constraints on the use of sludge by type of stakeholder isdifficult mainly because of the various possible attitudes within one category (see case studies inchapter 5.9), and because of the possible differences from one country to another. However, on the basisof the information collected in the course of this study, it is possible to give the following summary ofthe main stakeholders' positions (more details on the various possible attitudes within one category ofstakeholder are set out in the body of the report):

For farmers, the main motivation for the use of sludge in agriculture is the supply of organic fertiliserat a low cost. Their main constraints come from their customers, either food industries or retailers, whohave specific quality requirements. In a growing number of cases, these quality requirements includerestrictions on, and sometimes the prohibition of, the use of sludge in agriculture. In this context, themain consequences for farmers associated with the use of sludge in agriculture could be a reduction intheir market share and a drop in profits, as well as additional liability costs in the event of an accident.In this context, farmers require (in countries where the debate is heated) that a guarantee system be setup, which would cover them against both possible risks, in order to continue using sludge.

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Landowners are generally hostile to the agricultural use of sludge. Their attitude is based on two majorconcerns: liability and land value. Landowners do not want to be held liable in the event of an accident(harm to humans, animals and ecosystems) caused by the use of sludge and wish to prevent any loss inthe value of their land. The European Landowners' Organisation (ELO) adopted an official positionconcerning sludge recycling in agriculture in January 1999, which provides safeguards for the use ofsludge. In particular, the findings of the ELO focus especially on the need to strengthen legislation, theneed to "ensure that suppliers accept liability for any economic loss or damage associated withspreading sludge on their land", for instance by drawing up a pan-European model contract similar tothe model contract developed by the Country Landowner�s Association (CLA) in the UK.

The main influences on the agrifood industry are marketing and public health concerns. Theindustry's brand image is one of its most valuable assets and its primary concern is therefore to protectits image from being tarnished. In this sense, the industry's attitude is mainly influenced by the way inwhich the general public perceives the potential risks of using sludge in agriculture. As most of themembers of this industry are sludge producers as well, professional associations of food industries are,in most cases, officially in favour of maintaining the use of sludge in agriculture if the quality of sludgecan be guaranteed. As sludge producers, these companies are obviously seeking low-cost sludgedisposal routes.

The main motivation for food retailers is to be able to purchase agricultural products at a low cost andto secure their market share by maintaining or improving the image of the quality and safety of theirproducts. In this context, as there is still a great deal of scientific debate on the potential risks of the useof sludge in agriculture, land spreading could be perceived as a potential threat to their image. The mainconcern for food retailers involves the marketing stakes regarding product quality and, therefore, theextent to which the use of sludge may have an impact, whether real or perceived, on the quality ofagricultural products.

The main motivation for waste-water treatment companies is to maintain long-term disposal andrecycling routes for the sludge produced at the lowest possible cost. These companies are thereforeaware of the need to maintain agricultural land spreading as a major recycling route for sewagesludge, mainly for economic reasons. In this context, these companies are willing to improve theirperformance beyond that required by the regulations in order to protect the existing routes for sewagesludge. They are also aware of the need to improve practices, and also insist on the need to introducenational policies aimed at improving and controlling the quality of waste water entering the sewers.

The main waste management companies do not exclusively focus their business on sludge recycling.However, the main economic driver behind their subsidiaries specialised in organic waste managementhas led them to increase awareness of the importance of sludge quality control and of improving landspreading processes. In this respect, service quality assurance could become standard practice inEurope. In addition, waste management companies are increasingly developing the use of compostedsludge, as compost has the advantage of reducing odours and of being a commercially viable product.

Communities are in most cases seeking to maintain the existing disposal and recycling routes forsewage sludge that are both economically viable and safe in terms of health. In addition, communitiesare subject to strong pressure from their voters and are therefore concerned about limiting the "waterbill". The "NIMBY" factor is also an important element which makes a difference between acceptancein rural and in urban communities.

In most cases, national authorities have implemented policies supporting the use of sludge inagriculture, as it is considered to be the best economic and environmental option to deal with theincreasing quantities of sludge produced. In this context, national authorities are seeking to increaseconfidence in the quality and safety of products cultivated on sludge fertilised soils.

Consumer associations and nature protection associations have both played only a minor role innational debates on sludge recycling. Most consumer organisations involved in the debate on the use ofsludge in agriculture have been largely preoccupied with food safety. In this respect, some consumerassociations are concerned that the use of sludge in agriculture does not offer sufficient guarantees. Thelimited participation of consumer associations and the general public in the debate on sludge recyclingcan be explained by the lack of information made available to the public on these issues.

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The analysis of the stakeholders' positions shows that the main areas of consensus on sludge disposaland recycling routes are that the growing quantities of sludge must be treated in the aims of keepingboth environmental and economic costs as low as possible. Similarly, improving practices, bothwith regard to the treatment and the use of sludge, is now considered as essential. In the context ofuncertainties concerning the potential impacts on human health and the environment of the variousdisposal and recycling routes, all stakeholders are calling for additional research, in order to increaseconfidence in the use of sludge in agriculture.

Reducing constraints and encouraging the recycling of sludgeIn order to encourage the recycling of sludge, the following should be taken into account:

The development of agricultural recycling depends largely on the possibilities to improve the qualityof the sludge itself and increase confidence in sludge quality. This implies the prevention of pollutionof the waste water at source by reducing the possibilities for heavy metals and organic compounds toenter the waste water sewage system and improving sludge treatment as well as ensuring themonitoring of sludge quality. These technical solutions however require major investment from thewater companies or local authorities in charge of treating the waste water. The possibility to certify thetreatment processes involved and the quality of sludge, either through independent "sewage sludgeaudits" or by the certification of sludge production and treatment processes, could help to increaseconfidence in sludge quality. Similarly, the quality standards of sludge recycling practices also need tobe guaranteed, especially for agricultural recycling.

One of the main issues with regard to sludge recycling in agriculture is the setting up of guaranteefunds or insurance systems in order to cover any loss of profits, damages or other costs related to theuse of sludge in agriculture. This would partially address the issue of liability, which is a vital concernfor farmers and landowners in the debate over the use of sludge. In addition to economic instruments,legal provisions could be introduced to regulate producer liability. However, according to the City ofDüsseldorf officials, the guarantee fund was not considered as a decisive argument leading the City toprivilege the use of sludge in agriculture, and has even had negative consequences on the economicconditions of this route.

National regulatory requirements vary greatly from one country to another. In this area, nationalregulations, based on the same scientific grounds, should be considerably improved by the nextDirective on sludge use, in order to provide long-term perspectives for the use of sludge. With regard toincreasing confidence in the use of sludge, standardisation initiatives (continuation and completion ofCEN TC 308 work on the production and disposal of sewage sludge) have a major role to play.

The evolution of the debate on sludge disposal and recycling in Europe shows that the relationshipbetween farmers and their customers (food industry and retailers) is crucial for the acceptance of theuse of sludge in agriculture. Examples at national level show that an agreement at European levelbetween representatives of food industries, retailers, farmers and sludge producers could enhancemutual confidence and information transfer. In this respect, efforts could be made to improvecommunication between the major stakeholders, for example by creating "contact points" similar to thenational committees on sludge set up in several Member States.

The current state of the debate on sludge recycling and disposal routes clearly shows that the currentuncertainties over possible risks for human health and for the environment play a major part in theresistance against expanding various sludge recycling routes. The areas where scientific results are themost expected by the stakeholders contacted in the course of this study are possible effects of organicpollutants and pathogens in sludge. Progress in the social and political acceptance of sludge recyclingcould therefore be made by promoting research on these specific aspects, publishing the researchresults and making them widely available. In particular, there should be better dissemination of theresults of current national research programmes on the effects of the agricultural recycling of sludge onhealth.

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In addition to the dissemination of research results, an important effort of communication on sludgeuse should be carried out. In particular, tools such as codes of practice for the recycling of sludgeimplemented on a voluntary basis should be considered. Communication should especially aim topromote high-quality sludge (with low levels of contaminants), which could be recognised asfertilisers (or as a component of fertiliser products) at European level. The development of labels atEuropean level would enable users to identify high-quality sludge and to distinguish it from other typesof sludge or waste, thus improving the image of sewage sludge itself. Therefore, labels on productscould be a useful additional tool to labels on quality assurance, for encouraging the use of sludge inagriculture. The possibilities for providing more training opportunities to specific categories ofstakeholders (farmers, for example) should also be examined.

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5. Economic analysis

Evaluating and comparing different disposal and recycling options for sewage sludge

Landspreading routes rank best overall, landfilling and incineration routes worst

Landspreading of solid and landspreading of semi-solid sludge entail on average the lowest cost (110-160 �/ton of dry matter) from an overall economic point of view, i.e. accounting for both internal andexternal costs and benefits.

Landfilling, mono-incineration and co-incineration of sludge with other wastes entail the highest costs(260-350 � /on of dry matter) from an overall economic point of view.

Landspreading of composted sludge, use of sludge in land reclamation, and use of sludge in silviculturerecord intermediate total costs (210-250 � /ton of dry matter).

Total costs are mainly composed of investments and operating costs of sludge treatment. However,the quantifiable environmental impacts (external costs) can make a difference as regards routeswhose internal costs are similar.

Whatever the sludge route investigated, total costs are mainly composed of investment and operatingcosts (internal costs and benefits) of infrastructure and of operations required for sludge treatment. Theinternal costs of landspreading of composted sludge, use of sludge in land reclamation and use of sludgefor silviculture are among the highest.

Quantifiable environmental impacts, however, can be a factor in differentiating routes with similarinternal costs. For example, the environmental benefits associated with landspreading of compostedsludge make this route more attractive than the co-incineration of sludge with other waste, whereas theirnet internal costs are similar.

Quantifiable environmental impacts (external costs and benefits) represent less than 15% of total costs.However, many environmental impacts such as impacts on soil biology, ecosystems and some long-termeffects on human health could not be quantified. Thus, the importance of environmental costs andbenefits is in fact larger than estimated in this study.

The agronomic or farm value of sludge, assessed in terms of savings resulting from reduction infertiliser use, can represent between 10% and 30% of the cost of landspreading.

Farmers' interest in sludge can be increased due to treatments which enhance the fertiliser and enrichingagent content of the treated sludge, e.g. tertiary treatment of nitrogen or phosphorus, liming, or mixingwith a carbonated substance. However, such treatments lead to additional costs for sludge producers,which therefore means they may be of less general economic interest.

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Evaluating and comparing scenariosCosts of compliance with new requirements in terms of:

- more stringent limit values on heavy metals in sludge

- new limit values on heavy metals in soils

- new limit values on organic compounds in sludge

- more stringent obligation of treatment

- new requirements on sludge quality assurance system

range from 0.8 billion �/year in the short term to 1.0 billion �/year in the long term for the 15Member States of the European Union.

The best estimates of costs necessary to meet new regulatory requirements of more stringent limitvalues on heavy metals in sludge, new limit values on heavy metals in soils and new limit values onorganic compounds in sludge, more stringent obligation of treatment and new requirements on sludgequality insurance systems amount to 0.8 billion �/year in the short term, 0.9 billion �/year in themedium term (after 2015) and 1,0 billion �/year in the long term (after 2025) for the 15 Member Statesof the European Union.

The analysis shows that the �worst-case scenario�, where no sludge is able to meet new regulatoryrequirements without an efficient pollution prevention policy, leads to costs as high as 1.2 billion �/yearfor the 15 Member States of the European Union.

The share of the costs between Member States is approximately proportional to the relative quantities ofsludge produced in each Member State.

Estimated percentages of sludge failing to comply with new requirements on heavy metals andorganic compounds are high if no pollution prevention policy is implemented.

According to our estimates, 67% of sludge in the short term, and 83% in the long term, fails to complywith limit values on heavy metals or organic compounds in sludge or in soil, if no pollution preventionpolicy is implemented.

If an efficient pollution prevention policy is implemented, then this percentage could drop down to 25%(minimum due to proposed limit values on heavy metals in soil).

The integration of a Pollution Prevention Policy into the policy package leads to similar overall costs.

The integration of the necessary pollution prevention measures to minimise the diverting of sludge fromrecycling, the so-called called the Pollution Prevention Policy scenario, leads to a very limited increase(less than 15%) in the overall costs of the policy.

However, the evaluation of the costs of the measures required for the Pollution Prevention Policyscenario is difficult. As the costs used in the present study have been obtained from a single study(carried out in a United Kingdom context), cost estimates of such measures remain to be confirmed andfurther analysed.

However, the Pollution Prevention Policy changes the allocation of the costs among stakeholders: thePollution Prevention Policy scenario shifts majority of the cost-burden from the local authorities,farmers and citizens to the industry.

While the cost of an efficient pollution prevention policy is mostly borne by industries (around 60% forthe medium term estimates), the local authorities (20%) and water companies (8%), the cost withoutsuch a policy is borne mainly by local authorities (up to 60%, for the cost of switching fromlandspreading to incineration), farmers (up to 20%, for the loss of compounds of agricultural value) andcitizens (up to 16%, for environmental and health impacts).

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This change in the cost-burden, however, should not mask the fact that costs allocated to localauthorities and water operators (costs of switching from landspreading to incineration and up to 70% ofthe costs of a quality insurance scheme) are ultimately borne by water consumers.

Sludge management costs remain low compared to the overall water management costs but must bekept to a minimum

Sludge management costs remain relatively marginal when compared to the overall costs of managingwater and urban wastewater: internal costs of managing sewage sludge represent, on average for the 15Member States, less than 6% of the total costs of water service (production, delivering and treatment).

However, consumer sensitivity to increases in water prices resulting from the significant increase inprices during the past decade may impose constraints on ensuring sludge treatment costs are kept to aminimum.

Compliance costs for industrial sludge should be lower than those for urban sludge.

Whatever the scenario, costs of compliance with regulatory requirements that would also apply toindustrial sludge should be lower than those for urban sludge. This is mainly due to the lower estimatedproduction and better sludge quality.

Costs are estimated to range from 0,1 billion �/year in the short term to 0.2 billion �/year in the longterm.

Compliance costs in Accession Countries should be much lower than those borne by Member States.

Costs of compliance with new regulatory requirements in ten European Union Accession Countries, i.e.Bulgaria, Czech Republic, Estonia, Hungary, Latvia, Lithuania, Poland, Romania, Slovakia, Slovenia,should be significantly lower than those borne by the Member States. This is mainly due to the lowerquantities of sewage sludge currently produced and recycled in these countries, forecast to be muchlower than the quantities recycled in the Member States.

Sensitivity, uncertainties and limitations of the study resultsThe estimation of costs associated with the various scenarios are very sensitive to forecasts ofquantities of sludge recycled, quantities of sludge not meeting new regulatory requirements andpollution prevention costs.

The most sensitive factors for the analysis of scenarios are the forecasts of the quantities of sludgerecycled, the quantities of sludge not meeting new regulatory requirements and, for the PollutionPrevention Policy scenario, the costs of pollution prevention measures. Any variation in one of thesefactors leads to an almost proportional variation in the total costs of any scenario.

Sensitivity is relatively lower for other factors such as unit costs of switching from landspreading toincineration, quality assurance costs, sludge treatment obligations, nutrient concentration in sludge, andexternal cost coefficients.

Impacts of uncertainties on cost estimates for the scenarios are very high.

Uncertainties regarding basic factors are very high overall. Thus, overall uncertainties for estimates ofcosts associated with scenarios are high. Clearly, the results obtained in the present study are to be usedvery cautiously and remain indicative only.

Uncertainties that have the strongest impacts on the study results are the quantities of sludge notmeeting new regulatory requirements and pollution prevention management and costs. Otheruncertainties that were identified should have a more limited impact on the total costs estimated for thedifferent scenarios.

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Evaluation of environmental and social costs is limited to airborne emissions and may underestimatethe external costs and benefits.

Quantifiable environmental and social costs were limited to airborne emissions. Thus, the impacts onother natural environments (water and soil) have not been quantified.

As described in the scientific and technical report and in the social acceptance report, otherenvironmental effects or social issues may have significant impacts on the comparison of routes andscenarios. In particular, the lack of knowledge on how to economically quantify the impacts on soilbiology or the ecosystems, exposure to pollutants and their long-term effects on public health leads to alimitation of the evaluation of external costs.

Moreover, the social costs and benefits such as unpleasant odours, the fears associated with theperception of environmental or health risks, the acceptance of sludge by the farming world or by thefood industry etc, are key factors to be considered in assessing the overall impact and costs of disposaland recycling options and scenario. These factors have however, not been quantified.

Improving the economic analysis of sludge disposal and recycling: ideas for the wayforward

Improving the information base is necessary to increase the certainty of cost estimates

To reduce uncertainties and improve the reliability of results, information is required on:

• Sludge composition : a more precise evaluation of the percentage breakdown of sludge not meetingrequirements would require a precise and updated percentage breakdown of pollutants (heavy metalsand organic compounds) in the quantities of sludge produced for all 15 Member States.

• From general categories of sludge disposal and recycling routes to detailed databases withsludge quality, routes and treatments : more reliable results can be obtained if the databasecontaining the details of sludge quality (percentage breakdown) were to include the type of treatment(conventional, advanced etc) and a detailed allocation of sludge to different disposal and recyclingroutes. The description of detailed categories of disposal and recycling routes should be standardisedamong Member States.

• Defining Pollution Prevention Policy measures and cost : to obtain more reliable results on theimpact of Pollution Prevention Policy measures on the costs for scenarios, more analysis is requiredto better define the types of measures required for such Policy Prevention Policy in the variousMember States. Also, better estimates of the costs associated with these measures are required.

• Quantifying unknown external costs: human health, ecosystem degradation etc. : to make abetter evaluation of external costs, it would be necessary to improve knowledge on the economicalquantification of impacts on soil biology, ecosystems, the exposure to pollutants and long-termeffects on health (see chapter on "gaps in knowledge" in the scientific and technical report).

Information databases should also be developed for industrial sludge and for AccessionCountries to the European Union

At the present time, even less information is available on industrial sludge and the situation inAccession Countries than on urban sludge in Member States: for instance, basic information such assludge quantities and routes are not known. Therefore, more precise and reliable information should begathered on industrial sludge in Accession Countries in order to allow a comprehensive cost andbenefits analysis.

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6. Conclusion

Agricultural recycling makes both economic and environmental sense, provided the migration andaccumulation of substances and elements contained in sludge into the environment and the food chain,and the associated risks are reduced and addressed by adequate regulatory measures and good practices.

The development of agricultural recycling depends largely on the possibilities to improve the qualityof the sludge itself and increase confidence in sludge quality.

This implies the prevention of pollution of the waste water at source by reducing the possibilities forheavy metals and organic compounds to enter the waste water sewage system and improving sludgetreatment as well as ensuring the monitoring of sludge quality. These technical solutions will requiremajor investment both from the water companies and local authorities in charge of treating the wastewater, although these costs will remain low when compared to the overall costs of managing water andurban wastewater

The current uncertainties over possible risks for human health and for the environment plays a majorpart in the resistance against expanding various sludge recycling routes: many uncertainties remainconcerning the transfer of pollutants (especially organic pollutants) to the environmental media and thefood chain, and the possible effects of organic pollutants and pathogens in sludge. These issues wouldneed to be more accurately documented.

Progress in the social and political acceptance of sludge recycling could therefore be made bypromoting research on these specific aspects, publishing the research results and making them widelyavailable. In particular, there should be better dissemination of the results of current national researchprogrammes on the effects of the agricultural recycling of sludge on health.

In parallel, information is required on sludge composition, sludge production, treatments and routes,pollution prevention policy measures and cost, external costs (such as human health, ecosystemdegradation etc.) to reduce uncertainties and improve the reliability of cost estimates.