st

a,, Res

a r t i c l e i n f o

Article history:Received 24 July 2014Accepted 13 October 2014Available online 6 November 2014

Keywords:Waste incinerationZn recovery

bottom ash and air pollution control (APC) residues, namely yashes (including boiler ash and lter ash) and lter cake. While inmany countries bottom ash is already processed in order to recoversome of the metals contained (mainly iron scrap, but also alumin-ium and copper), APC residues (which amount in total to about2 million tons in the European Union) have been hardly consideredfor resource recovery so far. In all European countries they are clas-

s are either land-lso the bact or other

cals in order to complywith regulatory limit values for wastetance at non-hazardous landlls. Both practices are associatesignicant costs, ranging between 200 and 250/t y ash (2008) and the loss of valuable materials (e.g. metals). Contrary tothat, only a small portion of APC residues, mainly from uidized bedincineration, can be landlled in non-hazardous landlls withoutprior treatment.

Only in fewEuropean countries attempts aremade to recycleAPCresidues (Astrup, 2008) or at least parts of them. In the Netherlands,for instance, y ashes partly substitute ller material in asphalt Corresponding author.

Waste Management 37 (2015) 95103

Contents lists availab

an

els(Eurostat, 2014), which amounts, together with commercial waste,to about 78 million tons of total waste fed toWaste to Energy (WtE)plants (CEWEP, 2011). Besides the production of electricity andheat, MSW incineration (MSWI) goes along with the generation of

other hand.Due to these characteristics most APC residue

lled at hazardous waste landlls (this includes aof former salt mines) or are stabilized with cemenhttp://dx.doi.org/10.1016/j.wasman.2014.10.0100956-053X/ 2014 Elsevier Ltd. All rights reserved.kllingchemi-accep-d withAstrup,1. Introduction

In 2011 about 23% of Municipal Solid Waste (MSW) generatedwithin the European Union has been thermally valorised

sied as hazardous waste, which results from environmental con-cerns regarding the leachability of easily soluble salts (such as Cl,Na or K) and heavy metals (such as Cd, Pb, Cu or Zn) on the onehand, as well as the total content of As, Cd, Hg, and dioxins on theResource evaluationResource classicationa b s t r a c t

Solid residues generated at European Waste to Energy plants contain altogether about 69,000 t/a of Zn, ofwhich more than 50% accumulates in air pollution control residues, mainly boiler and lter ashes. Inten-sive research activities aiming at Zn recovery from such residues recently resulted in a technical scale Znrecovery plant at a Swiss waste incinerator. By acidic leaching and subsequent electrolysis this technol-ogy (FLUREC) allows generating metallic Zn of purity > 99.9%. In the present paper the economic viabilityof the FLUREC technology with respect to Zn recovery from different solid residues of waste incinerationhas been investigated and subsequently been categorised according to the mineral resource classicationscheme of McKelvey. The results of the analysis demonstrate that recovery costs for Zn are highly depen-dent on the costs for current y ash disposal (e.g. cost for subsurface landlling). Assuming current dis-posal practice costs of 220 /ton y ash, resulting recovery costs for Zn are generally higher than itscurrent market price of 1.6 /kg Zn. With respect to the resource classication this outcome indicates thatnone of the identied Zn resources present in incineration residues can be economically extracted andthus cannot be classied as a reserve. Only for about 4800 t/a of Zn an extraction would be marginallyeconomic, meaning that recovery costs are only slightly (less than 20%) higher than the current marketprice for Zn. For the remaining Zn resources production costs are between 1.5 and 4 times (7900 t/a Zn)and 1080 times (55,300 t/a Zn) higher than the current market value. The economic potential for Znrecovery from waste incineration residues is highest for lter ashes generated at grate incineratorsequipped with wet air pollution control.

2014 Elsevier Ltd. All rights reserved.b Institute for Water Quality, Resource and Waste Management, Vienna University of Technology, Karlsplatz 13/226, 1040 Vienna, Austriac Institute for Chemical Engineering, Vienna University of Technology, Getreidemarkt 9/166, 1060 Vienna, AustriaEvaluation of resource recovery from waresidues The case of zinc

J. Fellner a,, J. Lederer a, A. Purgar a, A. WinterstetteraChristian Doppler Laboratory for Anthropogenic Resources, Institute for Water Quality1040 Vienna, Austria

Waste M

journal homepage: www.e incineration

H. Rechberger b, F. Winter c, D. Laner a

ource and Waste Management, Vienna University of Technology, Karlsplatz 13/226,

le at ScienceDirect

agement

evier .com/locate /wasman

nagpaved roads. Even though the encapsulation in asphalt may lastlonger than in cement the dilution and dispersion of pollutants,resulting from this practice has to be criticized froman environmen-tal perspective. In Switzerland several waste incinerators treat theiry ashes by applying acidic washing. Salts/brine (e.g. for the regen-erationof ion exchangers or for de-icing roadsduringwinter time) aswell as heavymetals are thereby separated from the y ash, and theprocessed almost heavy metal free y ash cake is landlledtogether with bottom ash at non-hazardous waste landlls. Theheavy metals enriched ltrate is neutralized and the hydroxidesludge rich in Zinc (Zn) generated thereby can be sent to specicZn-oxide recycling facilities (Bhler and Schlumberger, 2010). Overthe last few years this so called FLUWA process has been furtherdeveloped and extended such that zinc can be recovered directlyat the incineration plant (Schlumberger, 2010). This new technol-ogy, called FLUREC, has recently been introduced on large scale ata Waste-to-Energy (WtE) plant in Switzerland (KEBAG, 2013).

Moreover, the recovery of Zn or other metals out of MSWI yashes has gained increasing interest in recent times, also outsideof Switzerland. Numerous research activities in different Europeancountries have been dedicated to a recovery of heavy metals con-tained in MSWI APC residues (e.g. Karlfeldt Fedje et al., 2010a,2012, 2012; Meylan and Spoerri, 2014). However, most studiesconducted so far focused mainly on the technical and environmen-tal evaluation of metal recovery (e.g. Boesch et al., 2014). Economicconsiderations with respect to metal recovery are rare and limitedto residues of certain WtE plants (Karlfeldt Fedje et al., 2014). Acomprehensive economic evaluation considering different MSWIy ashes from plants of various combustion and APC technologyhas not been carried out so far.

Hence, the aim of the present study is to evaluate the potentialfor recovery of Zn from incineration residues generated at Euro-pean WtE plants, focusing on y ashes but also considering bottomashes generated. Filter cake resulting from water purication ofincinerators using a wet ue gas cleaning system is not consideredin this study due to its small mass and low Zn content (Astrup,2008). The evaluation procedure is based on the framework forevaluating anthropogenic resources recently developed byLederer et al. (2014) is applied. Their approach foresees a combina-tion of analysing material ows of the resource of interest and asubsequent economic assessment for the recovery of those mate-rial ows. The nal outcome of the evaluation conducted repre-sents the classication of Zn ows in incineration residues intodifferent categories, which have been chosen in analogy to theclassication of natural resource stocks (discriminating betweenreserves, marginally economic resources, subeconomic resources,and other occurrences of low grade).

2. Material and methods

In general, the applied framework for evaluating anthropogenicresources follows the procedure given in Fig. 1. After an initialphase of prospection (1), which aims at the identication of rele-vant stocks and ows, a phase of detailed investigation comparableto the exploration (2) of natural deposits follows. Therefore, datafor resource ows and stocks of interest are collected and furtherprocessed. Thereto the method of material ow analysis MFA asdescribed by Brunner and Rechberger (2004) is applied. MFAallows tracing ows and stocks of materials or chemical substancesof interest with a system dened in space and time. Whereas dur-ing the prospection macro-level material ow analyses are con-ducted, the exploration phase is characterized by detailed MFA,which also accounts for uncertainties and if relevant also for asso-

96 J. Fellner et al. /Waste Maciated ows of wanted or unwanted substances. In order to extractthe desired material and produce a marketable good, a technologyfor Zn recovery is required. By choosing the technology, a roughestimate on the associated costs can be given (3). The latter formsthe base for the subsequent classication of the different types ofows and stocks of interest (4).

Due to the fact that investigations have a priori been dedicatedto the MSWI residues annually generated, the initial step ofresource prospection (step 1) has been left out in the frame ofthe present investigations. Furthermore, contrary to the evaluationof Lederer et al. (2014), only ow resources have been considered.Flow resources are characterized by a continuous availability atdifferent intervals and are in case of natural resources also classi-ed as renewable resources, which are in contrast to non-renew-able stock resources. According to Lederer et al. (2014) wastesgenerated can be considered as anthropogenic ow resources.

As for the present case study these ow resources are partlyclassied as hazardous waste, costs associated with the conven-tional disposal of these waste have to be accounted for as revenueswhen accomplishing the economic analysis of the recovery tech-nology chosen.

2.1. Exploration of Zn ows in MSWI residues

In order to explore residues from waste incineration aspotential secondary resource for Zn, a detailed literature analysisfocusing on the following issues has been conducted:

The amounts of waste incinerated in European WtE plants(CEWEP, 2011),

the technology of incineration applied distinguishing betweengrate incineration & rotary kilns on the one hand and uidizedbed incinerators on the other hand (ISWA, 2006a, 2013), as theydetermine the specic amount of different MSWI residues andtheir respective content of valuable metals,

the technology of air pollution control (APC) systems (wet, dry& semi-dry residue systems) used at EuropeanWaste-to-Energyplants and the respective amount of APC residues (ISWA, 2013,2006a), both again inuencing the content of valuable metals(e.g. Zn) in APC residues,

the Zn content in different MSWI residues (e.g., Auer et al.,1995; Hjelmar, 1996; Jakob et al., 1996; Abe et al., 2000;Nagib and Inoue, 2000; Mangialardi, 2003; Aubert et al., 2004;Hallgren and Strmberg, 2004; Ferreira et al., 2005; Aubertet al., 2007; Van Gerven et al., 2007; Chiang et al., 2008;Quina et al., 2008; Bontempi et al., 2010; Karlfeldt Fedje et al.,2010b; Karlsson et al., 2010; Lam et al., 2010; Schlumberger,2010; De Boom et al., 2011; Nowak et al., 2013; Boesch et al.,2014), and

transfer coefcients describing the portioning of Zn to the differ-ent outputs of incineration plants (e.g., Schachermayer et al.,1996; Brunner and Mnch, 1986; Morf and Brunner, 1998).

In all parameters of interest numerous data sources (as indi-cated above) have been utilized, which resulted in particular forthe Zn content in MSWI residues as well as for the transfer coef-cients of Zn rather in ranges of values than in exact gures. Thedeviations observed between the different sources have beenaccounted for by using uncertainty ranges for the respectiveparameters in the frame of the subsequent material ow and eco-nomic analyses.

Based on the results of the literature survey a material owmodel describing the ows of Zn through European WtE plantshas been established.

2.2. Economic Evaluation of Zn ows

ement 37 (2015) 95103The MFA model together with detailed information about therecovery technology, its consumables and costs for alternative

disposal of MSWI residues, form the basis for the economic evalua-tion of Zn recovery. To the knowledge of the authors the only tech-nology for recovering Zn from MSWI residues operating at largescale is the FLUREC process, although other technologies (e.g.Karlfeldt Fedje et al., 2014) for zinc extraction (producing a metalconcentrate of lower purity) have been developed in the recentyears. Therefore, the FLUREC technology has been assumed forthe economic evaluation of Zn resources present in MSWI residues.

Fig. 2 gives an overview of the FLUREC technology and summa-rizes the required operating supplies. Detailed information aboutthe specic quantities of the latter together with data about prod-ucts and by-products are of major importance for the economicevaluation. Boesch et al. (2014) who performed a LCA on wasteincineration enhanced with new technologies for metal recovery,

provide detailed information about materials and energy owsassociated with the recovery of Zn out of MSWI y ash. These dataabout energy and material ows were subsequently linked withmarket prices for the different operating supplies pOPi (includingelectricity) and for the nal product, which is Zn metal of pur-ity > 99.9%, pZn, as well as with the amount of the by-product, aconcentrate containing Pb, Cu, Zn and Cd. In addition specic costsCDPi for landlling the residues generated by the FLUREC technol-ogy, necessary investment costs of the technology CINV as well asavoided costs for the prevailing disposal of residues in Europe CCPare accounted for (see Eq. (1)). The latter include cement stabiliza-tion with subsequent disposal at non-hazardous waste landlls ordirect landlling at hazardous waste sites. Due to the fact that leg-islation for landlling of hazardous waste (e.g. landll tax) may

Fig. 1. Procedure for the evaluation of anthropogenic resources (after Lederer et al., 2014).

J. Fellner et al. /Waste Management 37 (2015) 95103 97Fig. 2. Schematic process diagram of the FLUREC technology (acidic y ash leaching wseparation of Pb, Cu, Cd during solidication) based on Boesch et al. (2014).ith integrated Zn recovery, whereby Zn powder is to be added for the reductive

nagmOPi is the specic mass of operating supply i (kg/t y ash) and spe-cic energy demand (kW h/t y ash),mDPi is specic mass of residuej (resulting from the FLUREC process) to be disposed of (kg/t y ash),mZn is specic mass of metallic Zn recovered (kg Zn/t y ash), mConis specic mass of concentrate containing Pb, Cu and Cd (kg Zn/t yash), pOPi is market price for operating supply i and energy demand i(/kg operating supply) or (/kW h), pZn is market price for metallicZn (/kg Zn), pCon is market price for concentrate containing Pb, Cuand Cd (/kg concentrate), cZn is specic production costs for metal-lic Zn (/kg Zn), CDPj is specic costs for the disposal of residue j (/kg residue), CINV is specic investment costs for the FLUREC technol-ogy (/t y ash), CFLUREC is specic overall costs for the FLUREC tech-nology (/t y ash) and CCP is specic costs for the current practiceof y ash disposal (/t y ash).

2.3. Classication of Zn ows

The classication of Zn present in MSWI residues has beenaccomplished in accordance with Lederer et al. (2014) who basedtheir evaluation framework for anthropogenic resources onMcKelvey (1972). The approach considers both, the economic via-bility of extracting a secondary raw material from a resource andproducing a tradable good, and the knowledge of the existence ofthe resource. For the economic classication, McKelvey suggeststhe following terms. Resources are economic or recoverable if theycan be extracted with a prot. Therefore, the production costs mustbe below the market price of the product achievable, which meansin our case cZn < pZn. Resources for which the production costs arehigher than the price, but not by more than a factor of 1.5, aremar-vary considerable between different European countries, ratherlarge uncertainty ranges for CCP had to be considered. The balance(Eq. (1)) of all expenses and revenues represent the overall speciccosts or benets of the FLUREC technology CFLUREC. In case CFLURECbecomes negative, Zn recovery can be considered as economic,whereas in case CFLUREC results in a positive value, the applicationof the FLUREC technology is non-economic at current marketprices.

Assuming that the overall specic costs of the FLUREC technol-ogy should be zero, specic production costs for secondary Zn cZn(/kg Zn) can be determined (see Eq. (2)). In case that specic pro-duction costs czn are lower than the market price pZn for metallicZn, Zn recycling (using the FLUREC technology) is economicallyviable and vice versa.

In order to account for the fact that all data required for the eco-nomic evaluation (physical mass ows, prices, costs for disposal ofresidues or investment costs) are uncertain, plausible data rangeswere dened and subsequently used to perform Monte Carlo sim-ulations. Thereto the software @risk was used. For the denition ofthe uncertainties temporal (i.e. over the last 5 years) and spatialvariations in market prices and costs for disposal have been evalu-ated. The uncertainty of specic materials ows and energy con-sumption of the FLUREC technology has been estimated based oninformation provided by Boesch et al. (2014).

Xn

i1mOPi pOPi

Xl

j1mDPj CDPj CINV mZn pZn mCon pCon

CCP CFLUREC 1

cZn Pn

i1mOPi pOPi Pl

j1mDPj CDPj mCon pCon CINV CCPmZn

2

98 J. Fellner et al. /Waste Maginally economic. Resources above this value are termed as submar-ginal or subeconomic, whereby according to Lederer et al. (2014) athreshold factor of 10 times the market price is assumed(pZn < cZn < 10 pZn). Resource ows whose production costs areabove the threshold (of 10 times the market price) are countedas other occurrences.

The classication according to the certainty of the existence of aresource ow is structured as identied demonstrated, identied inferred, and potentially undiscovered. To perform this classication,the uncertainties determined for each Zn ow in the residues ofMSWI are used. Identied demonstrated resources are of provenexistence and knowledge is highly certain (condence that theactual ow of Zn is at least this size is 90%). Identied inferredresources are dened here as the amount of Zn ows between thelower uncertainty bound (condence 90%) and the mean value ofthe ow. The same amount of the material (due to symmetricuncertainty ranges) is designated as potentially undiscoveredresources, which may exist but are highly uncertain. Finally, across-classication is accomplished considering both, economicviability and knowledge. Therein, reserves are resources that areboth identied demonstrated and economically extractable.The reserve base further includes the part that is identied dem-onstrated and not protably extractable with current technologyand market conditions (classied as marginally economic).

3. Results

3.1. Exploration of Zn ows in MSWI residues

According to CEWEP (2011) about 78 million tons of waste havebeen utilized in European (EU-28 + Norway and Switzerland) WtEplants in 2011. This equals to about 90% of the total waste inciner-ation capacity (about 86 million tons) installed. Out of the 78 mil-lion tons, the vast majority (68 million tons) is thermally valorisedin grate incinerators (GI), the remaining part of 4.2 million tons iscombusted in uidized bed combustion (FBC) plants. According toinformation (data of 350 plants out of 470 plants in total have beenavailable) provided by ISWA (2006a, 2013), about 45% of the incin-eration plants are equipped with wet ue gas cleaning systems,29% with semidry and 26% with dry systems. The discriminationof the incineration technology (grate vs. uidized bed) and APCsystem (wet-semidry-dry) is of signicant importance for theexploration of Zn ows, since the technologies do not only stronglyinuence the size and grade (with respect to Zn content) of yashes (see Table 1), but also the need of operating supplies (e.g.consumption of additional acids like HCl for acidic washing) aswell as costs for the current disposal practice. Fly ashes fromFBC, for instance, are likely to be disposed of at non-hazardouswaste landlls (due to their comparatively low contents of heavymetals and salts), whereas y ashes from grate incinerators areas a rule classied as hazardous and therefore have to be landlledat hazardous waste sites or stabilized prior landlling at non-haz-ardous sites. In Table 1 main outcomes of exploring MSWI residuesas potential resource for Zn recovery are summarized. Based on thedetailed analysis of data from more than 50 European WtE plants,it becomes obvious that the APC control but also the type of y ash(lter ash vs. boiler ash) strongly inuences the Zn content of they ash generated. Whereas for dry or semidry APC systems averageZn contents of y ashes amount to about 11,000 mg Zn/kg, wet sys-tems may generate residues with Zn contents of about 22,000 mgZn/kg y ash (in case boiler and lter ash are collected together)or even above 40,000 mg Zn/kg y ash (in case that lter ash iswithdrawn separately). In comparison to the contents given inTable 1, Zn contents of bottom ashes from waste incineration arealmost one order of magnitude smaller (11006000 mg Zn/kg bot-tom ash Hjelmar, 1996; Mller and Rbner, 2006; Dabo et al.,

ement 37 (2015) 951032009; Sorlini et al., 2011).Based on transfer coefcients describing the partitioning of Zn

duringwaste incineration (between50% and 60%of Zn is transferred

to the y ash and the remaining part to the bottom ash) and the datagiven in Table 1, the average content of Zn in thewaste feed of Euro-pean WtE plants have been determined to about 880 110 mg Zn/kg wet waste. Considering this content and the overall mass ofwaste combusted, the following material ow analysis diagramhas been derived (see Fig. 3). In total about 69 9 kt of Zn are annu-ally fed into European waste incineration plants. Almost half of it(32.5 2.7 kt) accumulates in MSWI residues (bottom ashes andy ashes from uidized bed combustion) at average concentrationsbelow 6000 mg Zn/kg ash (see supplementary material). About17 2.4 kt of Zn are present in boiler and lter ash of grate inciner-ators equipped with wet APC systems (average Zn content of about23,000 mg Zn/kg ash) and almost the same amount (18.5 1.8 kt)

et al., 2014) the different MSWI residues have been evaluatedregarding their specic costs for Zn recovery. In Table 2 all assump-tions made for the economic evaluation of Zn recovery from lterashes of wet APC systems are summarized. Data for evaluatingZn recovery from other MSWI residues (e.g. y ash from dry orsemidry APC systems) are given in supplementary material. Theresults for lter ashes from wet APC residues indicate that despitethe comparatively high Zn contents (around 41,000 mg Zn/kg ash)of these ashes, the specic production costs for Zn (taking allexpenses and revenues into account) are about 1.8 0.8 /kg Znand thus in average slightly above the current market price of1.6 /kg Zn (average price over the last 5 year). Nevertheless, thelarge uncertainty (standard deviation) in production costs of Zn

Table 1Statistical analysis of y ash (sum of boiler and lter ash, and APC residues in case of dry or semidry APC) amounts (kg/t waste) generated at Waste-to-Energy (WtE) plants withdifferent ue gas cleaning systems and their respective Zn contents (mg Zn/kg y ash).

Amount of y ash (kg/t waste input) Zn-content inue gas cleaning residues (mg Zn/kg y ash)

Flue gas cleaning system Boiler and lter ash of Filter ash of wet systemsa

Wet Semidryb Dryb Wet systems Semidry systemsb Dry systemsb

Mean 22 42 40 22,100 11,000 11,700 41,000Median 22 40 39 19,100 9700 10,800 42,70010% quantile 14 30 30 14,000 6700 7600 20,90090% quantile 30 53 54 35,700 15,600 18,500 59,600No. of WtE plants 53 33 11 16 14 9 15No. of different countries 11 10 6 11 10 6 5

a Plants with separate collection of lter ash and boiler ash.b In case of semidry and dry APC system boiler and lter ashes include air pollution control residues.

J. Fellner et al. /Waste Management 37 (2015) 95103 99can be found in y ashes from dry and semidry APC systems (aver-age Zn content of about 11,000 mg Zn/kg ash).

3.2. Economic evaluation and classication of Zn ows

Based on the material and energy demand of the FLUREC tech-nology and the potential recovery rates for Zn (provided by BoeschFig. 3. Annual Zn ows (in 1000 t) through European WtE plants utilizing Municipal Socondence interval, respectively) red ows indicate ows of MSWI residues with meauidized bed combustion, APC air pollution control). (For interpretation of the referencarticle.)(0.8 /kg, which equals 45% of the mean value) indicates thatdepending on the parameter set chosen (mainly depending onthe avoided costs for the prevailing disposal of incineration resi-dues), it may be likely that Zn can be recovered at costs lower thanthe current market price.

When comparing individual costs, revenues and savings associ-atedwith the different inputs and outputs of the FLUREC technologylid Waste MSW and Industrial Waste IW (uncertainties represent the 10% and 90%n Zn contents above 8000 mg Zn/kg (abbreviations used: GI grate incinerator, FBCes to colour in this gure legend, the reader is referred to the web version of this

Table 2Economic analysis of Zn recovery from MSWI residues (using the example of lter ash from wet APC systems) applying the FLUREC technology.

Means of production and outputs Materials and energy(per 1000 kg of yash)

Specic costs (positive) andbenets or savings (negative)

Total costs/savings (per1000 kg of yash)

Remarks

Unit Mean sd Unit Mean sd Datasource

Mean

inputsFly ash kg 1000 /kg -0.22 0.02 (1) 220 Savings for current disposal practiceZinc content of y ash kg 41 1HCl (30%) of wet scrubbera kg 550 100 /kg 0 0 HCl provided by acidic scrubber waterHCl (30%) additional kg 40 20 /kg 0.11 0.015 (2) 4.4 Required for enhanced extraction of

metalsSulfuric acid kg 15 1.5 /kg 0.16 0.02 (2) 2.4Hydrogen peroxide H2O2 (50%) kg 65 15 /kg 0.30 0.030 19.1NaOH (50%) kg 125 12.5 /kg 0.11 0.015 (3) 13.9 Costs for neutralization of extracted

residuesSolvents and complexing agents kg 0.4 0.08 /kg 0.4 0.1 (3) 0.2 Required for selective extraction of ZnPrimary Zinc (powder) kg 5 0.8 /kg 1.6 0.1 (4) 8.5 Zn necessary for reductive cementation

of Cd, Pb and CuQuicklime kg 200 20 /kg 0.08 0.01 (2) 16.0 Savings of quicklime for subsequent

neutralization of scrubber water incomparison to current practice

Electricity kW h 347 18 /kWh 0.094 0.005 (5) 32.6 Electrolysis of Zn and plant operation

Total investment costs for FLUREC (per1000 kg y ash)

180 20 (6) 180 Specic investment costs for FLUREC

outputsLeached y ash (non-hazardous waste

landll)kg 800 30 /kg 0.045 0.005 (7) 36.0 Disposal costs for leached y ash

Depleted resin material (Hg adsorption) kg 1 0.1 /kg 18 2.8 (8) 18.4 Costs for depleted resin material for Hgremoval from acidic scrubber water

Residual sludge (re-feeded to incinerator) kg 24 5 /kg 0 0 Concentrate Pb, Cu and Cd kg 9.2 1.5 /kg -1.6 0.2 (9) 14.8 Market value for concentrate of Pb, Cu

and CdRecovery rate of Zn 0.75 0.025

Necessary revenues from Znproduction

64.7

Secondary Zinc production kg 36.1 1.3 Specic Zn production costs (/kg) 1.8 0.8

All uncertainties given in table represent standard deviations sd of normal distribution.Data sources: (1) Astrup (2008) (2) www.alibaba.com; (3) www.orbichem.com; (4) www.nanzen.net; (5) Eurostat (2013); (6) based on investment costs provided by KEBAG(2013); (7) based on data provided by ISWA (2006b); (8) personal communication of BSH Umweltservice AG (2014); (9) personal communication of BMG Metall undRecycling GmbH (2014) based on the assumption that the ratio of Pb and Cu in the concentrate is about 85:15.

a provided by wet APC system.

Fig. 4. Specic costs (+) and revenues/saving () of the FLUREC technology when treating lter ash fromwet APC systems with an average Zn content of 41,000 mg/kg y ash.

100 J. Fellner et al. /Waste Management 37 (2015) 95103

it becomes obvious that avoided costs for the current disposal prac-tice of y ash aswell as investment costs for the technology aremostsignicant for the economic viability (see Fig. 4). The contribution ofrevenues realized by metallic Zn recovery is below 17% of the totalgross revenues, which amount to approximately 300/kg y ash.

For the other y and bottom ashes of European WtE plants, spe-cic production or recovery costs of Zn are much higher (see Fig. 5).This can be attributed on the one hand to the lower Zn content inthese ashes and on the other hand signicant amount of HCl isrequired for plants with dry or semi-dry APC systems. Moreoverrecovery costs for Zn contained in non-hazardous waste, such asy ash fromFBCor bottomash fromgrate incineration, are distinctlyhigher, as the potential savings for avoideddisposal costs after treat-ment are minor. Detailed information about the underlying data forthe economic evaluation of Zn recovery from different types of yashes and bottom ashes is provided in supplementary material.

Combining information about the size of Zn ows, incl. theiruncertainties (see Fig. 3) and the specic recovery costs (seeFig. 5) allows classifying Zn ows in accordance to the classica-tion scheme for mineral resources (McKelvey, 1972). The resultof this classication (Table 3) demonstrate that the total size ofthe identied Zn ows in European MSWI residues is 69,000 t/a.Based on the average market price for Zn over the last 5 years

(1.6 /kg Zn), none of the Zn in the investigated MSWI residuescan be economically extracted and thus cannot be classied as areserve, although Zn extraction from separately collected lterash from wet APC systems may already be economically viable incase that avoided costs for the disposal of untreated y ash areabove 230/ton ash.

The reserve base containing marginally economic and identied demonstrated resources amounts to 4100 t/a (separately col-lected lter ash from wet APC systems and assuming a technicalextraction rate for Zn of 75%). An additional 700 t/a are marginallyeconomic and inferred resources, leading to a total of 4800 t/a ofmarginally economic resources. These gures are based on theassumption that at 50% of European WtE plants with wet APC lterand the boiler ash can be separately collected. A total of 6800 t/a ofZn is classied as subeconomic and demonstrated, with productioncosts approximately 2.5 times above the current market price of Zn(boiler ash and jointly collected boiler and lter ash from wet APCsystems and assuming a technical extraction rate for Zn of 75%).Together with the inferred portion of 1100 t/a, the total of subeco-nomic resources is 7900 t/a. The residual bulk of Zn (47,400 t/ademonstrated and 7900 t/a inferred) is either low-grade y ashfrom dry or semidry APC systems (10,400 t/a of Zn), from bottomash (21,200 t/a), from y ash generated during FBC (1300 t/a) and

en i

rtain

price

J. Fellner et al. /Waste Management 37 (2015) 95103 101Fig. 5. Specic recovery costs for zinc (giv

Table 3McKelvey diagram for annual Zn ows (in t/a) in European MSWI residues (the unceinferred, and potentially undiscovered resources).

Identied resources

Demonstrated

Economic 0a

Marginally economic 4100b

Subeconomic 6800b

Other occurrences (low grade) 47,400Low-grade materials

Total 69,000

a An economically viable recovery of Zn from y ashes would (at current market

disposal of untreated ashes of more than 230 /ton ash.

b Assuming that at 50% of all WtE plants with wet APC systems lter ashes and boiler75%.n /kg Zn) from different MSWI residues.

ty ranges of the estimates form the basis for the distinction between demonstrated,

Potentially undiscovered resources

Inferred

0a 0a

700b 700b

1100b 1100b

7900 7900

9000

s) only be possible at Zn contents above 53,000 mg/kg ash or avoided costs for theashes can be separately collected and that technical recovery rates of Zn amount to

Current research initiatives with respect to metal recovery from

The presented work is part of a large-scale research initiative on

Association Working Group Thermal Treatment, Copenhagen, p. 86.

hazardous metals from MSW y ashan evaluation of ash leaching methods. J.

naganthropogenic resources (Christian Doppler Laboratory for Anthro-pogenic Resources). The nancial support of this research initiativeby the Austrian Federal Ministry of Science, Research and Economywaste incineration y ashes led us to investigate the potential andeconomic viability of Zn recovery from incineration residues.Thereto a survey about WtE in Europe with respect to combustiontechnology applied, air pollution control installed, as well as quan-tities and qualities (contents of Zn) of solid residues generated hasbeen conducted. Based on this survey, a MFA for Zn ows throughEuropean WtE plants has been established. Moreover the applica-tion of the only technology for Zn recovery applied so far at fullscale (FLUREC) has been evaluated regarding its economic viability,when being applied to different incineration residues.

The evaluation, based on the analysis of Zn ows through Euro-pean Waste-to-Energy plants and an economic assessment, indi-cates that approximately 75% of the Zn present in Europeanincineration residues, which amounts to 69,000 t of Zn, is hardlyextractable, as production costs would be at 1080 times higherthan current market price.

The reasons are, rst, comparatively low contents of Zn in theseresidues (150015,000 mg Zn/kg); and second, the fact that signif-icant amounts of Zn can only be extracted at low pH values(pH < 4), requiring in the absence of acidic scrubber water hugeamounts of HCl; and third, extractions rate for Zn applying FLURECare at best 75%, which implies that 25% of the Zn remain in the lea-ched residues.

The 25% Zn ow that is, in theory, recoverable, accumulates iny ash of grate incinerators equipped with wet APC. Average Zncontents of these y ashes are about 22,000 mg Zn/kg ash whenboiler and lter ash are collected together. In case that lter ashis separately extracted, the Zn content almost doubles. Accordingto the survey of European WtE plants such separate collection oflter ash seems to be established or possible at around 50% of grateincinerators with wet APC. The lter ash of grate incinerators withwet APC also contains the only Zn (4100 t/a) that could be recov-ered at production costs in the range or only slightly above the cur-rent market price for Zn. In case boiler and lter ash are jointlyextracted, Zn recovery (potential of 6800 t/a) becomes less eco-nomic; the specic production costs double and thus rise signi-cantly above current market price.

The results of the analysis demonstrate that with respect to uti-lizing Zn in incineration residues, grate combustion in combinationwith wet APC and separate collection of boiler and lter ash ispreferable.

Nonetheless in comparison to total European Zn import, whichamounts to about 1.3 million t/a (Spatari et al., 2003), Zn recoveryfrom marginally economic and subeconomic MSWI residues (y ashfrom grate incinerators with wet APC) could substitute 0.8% ofEuropean imports. This share of substitution could theoreticallybe increased to a maximum of 2.2% in case that all waste inciner-ated would be combusted in grate incinerators with wet APC.

Acknowledgmentspotential residues (leached ashes) of the FLUREC technology(10,900 t/a). Regarding certainty, 87% of the identied resourcesare demonstrated, and 13% are inferred stocks.

4. Discussion and conclusions

102 J. Fellner et al. /Waste Maand the National Foundation for Research, Technology and Devel-opment is gratefully acknowledged. The authors also gratefullyacknowledge the support of Karin Karlfeldt Fedje and Aurore DeHazard. Mater. 173, 310317.Karlfeldt Fedje, K., Rauch, S., Cho, P., Steenari, B.-M., 2010b. Element associations in

ash from waste combustion in uidized bed. Waste Manage. 30, 12731279.Karlfeldt Fedje, K., Ekberg, C., Skarnemark, G., Pires, E., Steenari, B.-M., 2012. Initial

studies of the recovery of Cu from MSWI y ash leachates using solventISWA, 2013. Waste-to-Energy State-of-the-Art-Report, Statistics, sixth ed.International Solid Waste Association, Vienna, p. 210.

Jakob, A., Stucki, S., Struis, R.P.W.J., 1996. Complete heavy metal removal from yash by heat treatment: inuence of chlorides on evaporation rates. Environ. Sci.Technol. 30, 32753283.

Karlfeldt Fedje, K., Ekberg, C., Skarnemark, G., Steenari, B.-M., 2010a. Removal ofBoom, who provided information with respect to quantities andcomposition of y ashes generated at WtE plants in Sweden andBelgium.

Appendix A. Supplementary material

Supplementarydata associatedwith this article canbe found, in theonline version, at http://dx.doi.org/10.1016/j.wasman.2014.10.010.

References

Abe, S., Kagami, T., Sugawara, K., Sugawara, T., 2000. Zinc and lead recovery frommodel ash compounds. In: Second International Conference on ProcessingMaterials for Properties, pp. 733736.

Astrup, T., 2008. Management of APC residues from W-t-E Plants An overview ofmanagement options and treatment methods. International Solid WasteAssociation (ISWA), Copenhagen, p. 116.

Aubert, J.E., Husson, B., Vaquier, A., 2004. Use of municipal solid waste incinerationy ash in concrete. Cem. Concr. Res. 34, 957963.

Aubert, J.E., Husson, B., Sarramone, N., 2007. Utilization of municipal solid wasteincineration (MSWI) y ash in blended cement: Part 2. Mechanical strength ofmortars and environmental impact. J. Hazard. Mater. 146, 1219.

Auer, S., Kuzel, H.J., Pollmann, H., Sorrentino, F., 1995. Investigation on Msw y-ashtreatment by reactive calcium aluminates and phases formed. Cem. Concr. Res.25, 13471359.

Boesch, M.E., Vadenbo, C., Saner, D., Huter, C., Hellweg, S., 2014. An LCA model forwaste incineration enhanced with new technologies for metal recovery andapplication to the case of Switzerland. Waste Manage. 34, 378389.

Bontempi, E., Zacco, A., Borgese, L., Gianoncelli, A., Ardesi, R., Depero, L.E., 2010. Anew method for municipal solid waste incinerator (MSWI) y ash inertization,based on colloidal silica. J. Environ. Monit. 12, 20932099.

Brunner, P.H., Mnch, H., 1986. The ux of metals through municipal solid wasteincinerators. Waste Manage. Res. 4, 105119.

Brunner, P.H., Rechberger, H., 2004. Practical Handbook of Material Flow Analysis.CRC Press LLC, Boca Raton, Florida.

Bhler, A., Schlumberger, S., 2010. Schwermetalle aus der Flugaschezurckgewinnen: Saure Flugaschenwsche FLUWA Verfahren, einzukunftsweisendes Verfahren in der Abfallverbrennung (Recovering HeavyMetals from Fly Ash: Acidic Fly Ash Scrubbing FLUWA, a TrendsettingProcedure in Waste Incineration). KVARckstnde in der Schweiz DerRohstoff mit Mehrwert (MSWI Residues in Switzerland A Resource withAdded Value). Swiss Federal Ofce for the Environment (FOEN), Bern.

CEWEP, 2011. Map of European Waste-to-Energy plants in 2011. Confederation ofEuropean Waste-to-Energy Plants, Brussels. (accessed 28.09.14).

Chiang, K.Y., Jih, J.C., Chien, M.D., 2008. The acid extraction of metals frommunicipalsolid waste incinerator products. Hydrometallurgy 93, 1622.

Dabo, D., Badreddine, R., De Windt, L., Drouadaine, I., 2009. Ten-year chemicalevolution of leachate and municipal solid waste incineration bottom ash used ina test road site. J. Hazard. Mater. 172, 904913.

De Boom, A., Degrez, M., Hubaux, P., Lucion, C., 2011. MSWI boiler y ashes:magnetic separation for material recovery. Waste Manage. 31, 15051513.

Eurostat, 2013. Electricity Prices By Type of User. (accessed 15.06.14).

Eurostat, 2014. Municipal Waste Statistics. (accessed 28.09.14).

Ferreira, C., Jensen, P., Ottosen, L., Ribeiro, A., 2005. Removal of selected heavymetals from MSW y ash by the electrodialytic process. Eng. Geol. 77, 339347.

Hallgren, C., Strmberg, B., 2004. Current methods to detoxify y ash from wasteincineration. Svensk Fjrnvrme AB, TPS.

Hjelmar, O., 1996. Disposal strategies for municipal solid waste incinerationresidues. J. Hazard. Mater. 47, 345368.

ISWA, 2006a. Waste-to-Energy State-of-the-Art-Report, Statistics, fth ed.International Solid Waste Association, Copenhagen, p. 232.

ISWA, 2006b. Management of Bottom Ash from WTE Plants An Overview ofManagement Options and Treatment Methods. International Solid Waste

ement 37 (2015) 95103extraction. Waste Manage. Res. 30, 10721080.Karlfeldt Fedje, K., Andersson, O. Modin, P., Frndegard, P., Pettersson, A., 2014.

Opportunities for Zn recovery from Sweidsh MSWI y ashes. 2nd Symposium

on Urban Mining, Bergamo, Italy; 19.05.201421.05.2014; in: SUM2014, 2ndSymposium on Urban Mining, IWWG, p. 18.

Karlsson, S., Carlsson, P., berg, D., Karlfeldt Fedje, K., Krook, J., Steenari, B.-M., 2010.What is required for the viability of metal recovery from municipal solid-wasteincineration y ash?-Design and assessment of a process plant for copperextraction. In: Proceedings of LINNAEUS ECOTECH10 Nov 2224, 2010, Kalmar,Sweden, pp. 463474.

KEBAG, 2013. Jahresbericht 2012 [Annual Report 2012]. Kehrichtbeseitigungs-AG(KEBAG), Zuchwil, Switzerland.

Keppert, M., Pavlk, Z., Tydlitt, V., Volfov, P., varcov, S., yc, M., Cerny, R., 2012.Properties of municipal solid waste incineration ashes with respect to theirseparation temperature. Waste Manage. Res. 30, 10411048.

Lam, C.H.K., Ip, A.W.M., Barford, J.P., McKay, G., 2010. Use of Incineration MSW ash:a review. Sustainability 2, 19431968.

Lederer, J., Laner, D., Fellner, J., 2014. A framework for the evaluation ofanthropogenic resources: the case study of phosphorus stocks in Austria. J.Clean. Product. doi: 10.1016/j.jclepro.2014.05.078 (in press).

Mangialardi, T., 2003. Disposal of MSWI y ash through a combined washing-immobilisation process. J. Hazard. Mater. 98, 225240.

McKelvey, V.E., 1972. Mineral resource estimates and public policy. Am. Sci. 60, 3240.

Meylan, G., Spoerri, A., 2014. Eco-efciency assessment of options for metalrecovery from incineration residues: a conceptual framework. Waste Manage.34, 93100.

Morf, L.S., Brunner, P.H., 1998. The MSW incinerator as a monitoring tool for wastemanagement. Environ. Sci. Technol. 32, 18251831.

Mller, U., Rbner, K., 2006. The microstructure of concrete made with municipalwaste incinerator bottom ash as an aggregate component. Cem. Concr. Res. 36,14341443.

Nagib, S., Inoue, K., 2000. Recovery of lead and zinc from y ash generated frommunicipal incineration plants by means of acid and/or alkaline leaching.Hydrometallurgy 56, 269292.

Nowak, B., Aschenbrenner, P., Winter, F., 2013. Heavy metal removal from sewagesludge ash and municipal solid waste y ash a comparison. Fuel Process.Technol. 105, 195201.

Quina, M.J., Bordado, J.C., Quinta-Ferreira, R.M., 2008. Treatment and use of airpollution control residues fromMSW incineration: an overview. Waste Manage.28, 20972121.

Schachermayer, E., Bauer, G., Ritter, E., Brunner, P.H., 1996. Entwicklung einer neuenMethode, um aus den Produkten der Mllverbrennungsanlage Spittelaukostengnstig die Vernderung der Zusammensetzung des Wiener Mlls zubestimmen (A new cost effective method for determining the composition ofMunicipal Solid Waste in the city of Vienna using information about theresidues of the waste incinerator Spittelau). Institute for Water Quality andWaste Management, Vienna University of Technology, Vienna.

Schlumberger, S., 2010. Neue Technologien und Mglichkeiten der Behandlung vonRauchgasreinigungsrckstnden im Sinne eines nachhaltigenRessourcenmanagements (New Technologies and Possibilities for theTreatment of Flue Gas Cleaning Residues to Achieve Sustainable ResourceManagement). KVA Rckstnde in der Schweiz Der Rohstoff mit Mehrwert(MSWI Residues in Switzerland A Resource with Added Value). Swiss FederalOfce for the Environment (FOEN), Bern.

Sorlini, S., Abb, A., Collivignarelli, C., 2011. Recovery of MSWI and soil washingresidues as concrete aggregates. Waste Manage. 31, 289297.

Spatari, S., Bertram, M., Fuse, K., Graedel, T.E., Shelov, E., 2003. The contemporaryEuropean zinc cycle: 1-year stocks and ows. Resour. Conserv. Recycl. 39, 137160.

Van Gerven, T., Cooreman, H., Imbrechts, K., Hindrix, K., Vandecasteele, C., 2007.Extraction of heavy metals from municipal solid waste incinerator (MSWI)bottom ash with organic solutions. J. Hazard. Mater. 140, 376381.

J. Fellner et al. /Waste Management 37 (2015) 95103 103

Evaluation of resource recovery from waste incineration residues The case of zinc1 Introduction2 Material and methods2.1 Exploration of Zn flows in MSWI residues2.2 Economic Evaluation of Zn flows2.3 Classification of Zn flows

3 Results3.1 Exploration of Zn flows in MSWI residues3.2 Economic evaluation and classification of Zn flows

4 Discussion and conclusionsAcknowledgmentsAppendix A Supplementary materialReferences