New Nitrogen-Containing Recycled Fertilizers: Bioavailability of Nutrients and Harmful Elements

ecycling A icle New Ni ogen-Con aining Recycled Fe ilize s: Bioa ailabili y o Nu ien s and Ha m ul Elemen s Janne Pesonen 1,* and Pasi Rau io 2 1Resea ch Uni o Sus ainable Chemis y, Uni e si y o Oulu, P.O. Box 4300, FI-90014 Oulu, Finland 2Na u al Resou ce Ins i u e Finland, Ounasjoen ie 6, FI-96200 Ro aniemi, Finland; pasi. au i[email p o ec ed] *Co espondence: [email p o ec ed]; Tel.: +358-055726233 Recei ed: 26 Ma ch 2019; Accep ed: 10 Ap il 2019; Published: 12 Ap il 2019   Abs ac : En i onmen al policies o he Eu opean Union aim o inc ease ecycling and e-use o was e-s eams. One o he economically mos p o i able ways o e-using was e is o use i as a e ilize . In his s udy, ecycled ni ogen e ilize s we e manu ac u ed om indus ial side-s eams (sawdus , ly-ash, ammonium sul a e and lignosul ona e). A sequen ial ex ac ion p ocedu e was applied o all he p oduc s es ed in his pape o make su e ha he en i onmen al equi emen s o a ecycled e ilize would be ul illed. A mass ac ion o up o 7.0% o ni ogen was achie ed wi h sawdus g anule and 7.2% wi h ly-ash-sawdus g anule, indica ing ha he g anules would be well sui ed o be used as ni ogen-con aining e ilize s. Ni ogen elease om sawdus g anule was mo e con olled han om comme cial salpe e. Sawdus combined wi h ly-ash can hence gi e a balanced nu ien mix when used oge he . Bioa ailabili ies and pseudo- o al con en s o ha m ul elemen s (As, Cd, C , Cu, Ni, Pb, and Zn) we e small in all g anules and cause no ha m in ield o o es e ilize use. Keywo ds: ammonium; bioa ailabili y; ly-ash; ecycled e ilize s; sawdus ; was e u iliza ion 1. In oduc ion The Eu opean Commission in i s ci cula economy s a egy is aiming o inc ease ecycling and e-use o p oduc s and was e ma e ials [ 1 ]. This s a egy is linked o he Was e F amewo k Di ec i e o he Eu opean Union [ 2 ] ha includes 5-s ep was e hie a chy in which di e en op ions o dealing he was e a e desc ibed. In his hie a chy, he i s goal is o p e en was e-s eams. I his is no possible, he nex s ep down in he was e hie a chy is he p epa a ion o was e o e-use, ollowed by ecycling, o he eco e y (e.g., ene gy eco e y) and, inally, i none o he ini ial ou s eps a e easible, was e should be disposed wi hou ha ming he en i onmen . One o he economically mos p o i able ways o e-using was e is o use i as a e ilize . This way one can eplace a i icial e ilize s, which ha e a ela i ely high ca bon oo p in due o hei high-ene gy consump ion in p oduc ion phase, and s ill s ay high on he 5-s ep was e hie a chy desc ibed abo e [ 3 ]. As an example, i has been es ima ed ha in Finland alone he economic alue o ecycling nu ien s is a ound 0.5 billion eu os annually [ 4 ]. Besides he manu e coming om animal husband y, he mos aluable sou ces o nu ien s in was es a e combus ion ashes and side-s eams o acili ies p ocessing o ganic was e and sewage sludge [5,6]. A he momen , a la ge pa o he wood and pea ashes p oduced in he o es indus y and powe plan s ends up a was e disposal si es, e en hough hey could be e-used as e ilize s [ 5 , 7 ]. Wood ly-ash (FA), in pa icula , is ich in nu ien s needed in plan nu i ion. O he majo nu ien s needed in plan g ow h and unc ion, only ni ogen (N) and sulphu (S) a e no p esen in FA, as hey a e eleased in o he a mosphe e du ing combus ion [ 8 ]. In places ha al eady ha e abundan ly N in he soil, like la ge a eas in Cen al-Eu ope, due o high N-deposi ion o many pea lands, plain ash can Recycling 2019,4, 17; doi:10.3390/ ecycling4020017 www.mdpi.com/jou nal/ ecycling Recycling 2019,4, 17 2 o 11 wo k as a balanced e ilize . Fo example, in pea lands, ni ogen le els a e usually na u ally high, whe eas phospho ous (P) and po assium (K) a e he g ow h limi ing nu ien s. I has in ac been shown ha in pea land o es s FA can ou pe o m comme cial PK e ilize s (phospho ous–po assium e ilize s) in inc easing ee g ow h, as well as in inancial pe o mance [ 9 – 11 ]. In mine al soil o es s and in mos in ensi ely cul i a ed ag icul u al ields, ni ogen is he g ow h limi ing nu ien and should hence be applied wi h ash o make a balanced e ilize . To a oid p oblems caused by dus , FA needs o be g anula ed be o e sp eading. G anula ion is also a signi ican ly mo e cos -e ec i e al e na i e o ash ecycling compa ed wi h unp ocessed FA [ 12 ]. Co-g anula ion o FA wi h some ni ogen con aining ma e ial, such as sewage sludge, could p oduce new e ilize p oduc s o ni ogen poo soils [ 13 ]. Because sludges migh also con ain ha m ul elemen s, such as many syn he ic o ganic subs ances [ 14 ], he e has been a emp s o ex ac N om sludges so ha only he pu e ecycled ni ogen could be used as e ilize . One me hod o sepa a e N om sludge is o ex ac N om biogas plan diges a e by s ipping ammonia by sul u ic acid o o m ammonium sulpha e ((NH 4 ) 2 SO 4 ). Howe e , ammonium e apo a es easily as ammonia gas a alkaline condi ions and he e o e i is no easy o me ge ammonium wi h alkaline ma ix such as FA [ 15 ]. He e, we aim o es i we can modi y FA so ha amalgama ion o ammonium sulpha e is possible, o amalgama e ammonium sulpha e wi h some o he ecycled media ha can be g anula ed. This is he i s s udy whe e such an a emp has been made. Be o e was e can be eused as a e ilize , i needs o ul il quali y le els as well as sa e y le els se by legisla ion. Eu opean en i onmen al legisla ion equi es ha pseudo- o al concen a ions (i.e., acid-leachable me als ha a e no pa o silica e ma ix), and/o wa e -soluble concen a ions o he ha m ul elemen s a e s udied om was e ma e ials [ 7 , 16 – 19 ]. This, howe e , does no gi e eliable in o ma ion o he en i onmen al isks associa ed wi h he u iliza ion o disposal o was es. F om he poin o iew o en i onmen , i is no so impo an wha he o al concen a ion o e.g., hea y me als in was es and o he esidues is, bu a he how easily he me als can be mobilized om he inspec ed ma e ial in o he en i onmen . Wa e -soluble concen a ion is no a su icien measu e o he en i onmen al isks because he dis illed o deionized wa e used in he es s does no ep esen no mal sal concen a ion o ionic s eng h o he soil solu ion [ 20 ]. Nei he a e hese p ocedu es su icien o assess he bioa ailabili y o nu ien s om e ilize s. The e o e, o be able o be e e alua e e ec s o di e en en i onmen al condi ions on bioa ailabili y and mobili y o di e en con aminan s, sequen ial ex ac ion me hods ha e been widely used wi h di e en en i onmen al samples du ing he las ew decades [ 21 – 24 ]. In he sequen ial ex ac ion p ocedu e, di e en chemical eagen s a e applied o he sample in a se ies and each successi e ea men is mo e d as ic han he p e ious one. A sequen ial ex ac ion p ocedu e di ides he o al ex ac able me al concen a ion in o ac ions in o de o assess he bioa ailabili y and he o m in which he me als occu in he s udied ma e ial [25]. In his s udy, we aimed o ind ou i , by manipula ing FA pH, we can add ammonium sulpha e in o FA o make a new ype o ni ogen ich ecycled e ilize o i we can combine ammonium sulpha e o some o he ecycled ma e ial o make a balanced e ilize o all pu poses. To make su e ha ou p oduc s would ul ill he en i onmen al equi emen s o a ecycled e ilize , we applied a sequen ial ex ac ion p ocedu e o all he p oduc s es ed he e. 2. Ma e ials and Me hods 2.1. Raw Ma e ials and G anula ion The FA used in his s udy was om a 96-MW (Megawa ) he mal powe plan si ua ed in Ro aniemi, No he n Finland. The powe plan uses a ci cula ing luidized bed combus ion echnique. The uels used a he plan a e wood and pea . The uel a ios (d y mass) a he powe plan we e app oxima ely 50% wood (logging esidue) and 50% pea . The sample was collec ed 14 May 2014 di ec ly om ash silo. Comme cial 350 g L −1 ammonium sul a e solu ion s ipped om a biogasi ica ion p ocess (En o , Finland), 850 g L −1 phospho ic acid (Sigma-Ald ich, S . louis, MO, Uni ed S a es) and Recycling 2019,4, 17 3 o 11 lignosul ona e om a pulp and pape mill (Bo egaa d, No way) was used in he g anula ion p ocess. Sawdus (SD) came om a sawmill si ua ed in No he n Finland. The composi ions o he g anules manu ac u ed in his s udy a e p esen ed in Table 1. G anule FA was a con ol sample ha con ained only FA and wa e . P e ious s udy [ 15 ] indica ed ha i ammonium sulpha e is mixed wi h FA, he ammonium e apo a es as ammonia gas due o he high pH o FA, and he e o e ammonium canno be added di ec ly o he FA g anules. In his s udy, phospho ic acid was used o: (i) con ol he pH o FA; (ii) o b ing ex a phospho us o he g anules; and (iii) o ac as a binding agen . Phospho us acid dissol es silicon and aluminum om FA o o m a geopolyme amewo k [ 26 ], which keeps he g anule in one piece. SD was used ei he alone o wi h FA as a ma ix o abso b ammonium. Lignosul ona e was used as a binding agen o SD-based g anules. Table 1. Composi ion and sample names o he g anules. FA = ly ash; SD =sawdus ; PA =phospho ic acid. Sample Composi ion (Mass F ac ion (%)) FA 60% ly ash; 40% wa e FAPA 61.3% ly ash; 12.3% phospho ic acid; 26.4% ammonium sulpha e solu ion FASD 19.2% ly ash; 19.2% sawdus ; 9.6% lignosul ona e; 3.8% phospho ic acid; 48.1% ammonium sulpha e solu ion SD 28.6% sawdus ; 14.3% lignosul ona e; 57.1% ammonium sulpha e solu ion All g anules we e manu ac u ed he same way: all d y ma e was ca e ully agi a ed using a ibbon blade agi a o un il a homogenous mix u e was achie ed. Solu ion was hen slowly added, while s ill agi a ing he mix u e, un il small agg ega es s a ed o o m in he pas e. G anules we e o med simply by olling he pas e in he hand un il i m, sphe ical g anules we e achie ed (diame e app ox. 20 mm). The g anules we e cu ed a oom empe a u e (21 ± 2 ◦ C) o a leas 28 days. pH- alues o all manu ac u ed g anules was be ween 5–6 (liquid o solid a io L S −1 =10 L kg −1 ); he e o e, he e we e no ammonia losses. 2.2. Analysis Me hods G anules we e c ushed and sie ed o a pa icle size smalle han 0.5 mm be o e analyses. Ni ogen con en s we e analyzed using a Pe kin Elme 2400 se ies II CHNS-analyze a he Uni e si y o Oulu (Wal ham, MA, Uni ed S a es). The pseudo- o al elemen concen a ions we e cha ac e ized by aqua egia diges ion acco ding o s anda d ISO 11466 [ 27 ] and analyzed wi h he induc i ely coupled plasma op ical emission spec ome y (ICP-OES) echnique a an acc edi ed labo a o y. The 4-s ep sequen ial ex ac ion p ocedu e (Table 2) used in his s udy is based on he Communi y Bu eau o Re e ence (BCR) p ocedu e [ 28 ]. S ages 2 o 4 ollow he BCR p ocedu e, bu he i s s age in ol es ex ac ion wi h deionized wa e acidi ied o pH 4 wi h HNO 3 [ 29 ]. The pu pose o he i s s age is o simula e he e ec o acidic ainwa e —p esen day ain—on he solubili y o he me als. This 4-s ep sequen ial leaching p ocedu e has been used success ully wi h samples including bo om ash and FA [ 29 – 32 ]. The elua es om each s ep we e sepa a ed om he esidue by cen i uging o 20 min (RCF =3000) and analyzed using he ICP-OES echnique a an acc edi ed labo a o y. Duplica e samples om each ba ch we e analyzed, and he a e ages we e calcula ed. Howe e , he F4 esul o FA g anule is based on a single measu emen due o e o s made in he leaching s age. The mois u e con en s o he FA and he FA g anules we e measu ed acco ding o s anda d SFS-EN 12880 [ 33 ] by d ying he samples in a ho ai o en o 24 h a 105 ± 2 ◦ C. The d ied samples we e placed in cooling desicca o s and weighed. Howe e , he samples we e no d ied p io he sequen ial leaching p ocedu e, since hea can a ec he leaching o elemen s [ 34 ]. Ins ead, he mois u e con en s we e aken in o accoun as he leaching esul s we e calcula ed. The mois u e mass ac ions o he samples we e: 1.6% o FA; 5.2% o FAPA; 5.7% o FASD; and 4.2% o SD. Recycling 2019,4, 17 4 o 11 Table 2. 4-s ep sequen ial leaching p ocedu e [ 28 , 29 ]. Mass o he sample was 1 g am a he i s s age. S ep F ac ion Ex ac an Expe imen al Condi ions F1 Wa e -soluble 40 cm3H2O a pH 4 (wi h HNO3)16 h a 22 ±5◦C, cons an shaking F2 Exchangeable and acid soluble 40 cm3HOAc 0.11 mol L−116 h a 22 ±5◦C, cons an shaking F3 Reducible 40 cm3NH2OH·HCl 0.5 mol L−1 a pH 1.5 (wi h HNO3)16 h a 22 ±5◦C, cons an shaking F4 Oxidizable 10 cm3H2O2300 g L−1 1 h a 22 ±5◦C, occasional manual shaking, hen 1 h 85 ±2◦C. Reduce he olume o less han 3 cm3 10 cm3H2O2300 g L−11 h a 85 ±2◦C 50 cm3NH4OAc 1 mol L−1 a pH 2 (wi h HNO3)16 h a 22 ±5◦C The ac ions o he 4-s ep sequen ial ex ac ion a e he wa e -soluble ac ion; exchangeable and acid-soluble ac ion; educible ac ion; and oxidizable ac ion [ 21 ]. In heo y, he i s ac ion should con ain wa e -soluble ions. This ac ion is he mos mobile, and i con ains po en ially he mos eadily a ailable me al and me alloid species. The second ac ion should con ain me als bonded elec os a ically, me als bonded wi h weak co alen bonds, o me als bonded o ca bona es. The hi d ac ion should con ain me als bonded o Mn and Fe oxides, and he ou h ac ion me als bonded o o ganic ma e o o di e en sul ides and oxides. In he p esen s udy, he i s wo ac ions (F1 and F2) a e e e ed o as easily bioa ailable ac ions. The o al bioa ailabili y e e s o he sum o he ac ions (F1–F4) [21,28,35]. 2.3. Leaching T ial Leaching a e o ammonium sulpha e abso bed o he SD was s udied in an ad hoc labo a o y expe imen . In he expe imen , nine plas ic unnels (diame e 20 cm) we e posi ioned in a s u dy suppo o keep he unnels in place. Each unnel was illed wi h ine qua z sand in nylon back so ha a ew cen ime e s o he op o he unnel emained ee (Figu e A1 in Appendix A). Each o he unnels was andomized o ecei e one o he ollowing h ee ea men s: (i) sample SD (i.e., ammonium sulpha e abso bed o SD and lignosulphona e), (ii) comme cial ni ogen e ilize (salpe e, i.e., ammonium ni a e) and (iii) con ol (plain qua z sand). Each o he h ee ea men s was eplica ed h ee imes. Bo h ea men s (i) and (ii) had he same amoun o ni ogen ( he le el co esponds o 120 kg o N pe hec a e in p ac ical o es e iliza ion). Each unnel was wa e ed wi h 1.58 li es o milliQ wa e (pH 5.6, i.e., equal o clean ain wa e ) i e imes. Be ween each wa e ing, he e was a leas one day, so ha he e ilize s had ime o d y be ween he wa e ings. The wa e leaching h ough he unnels was collec ed in glass sample bo les posi ioned below he unnels (Figu e A1 in Appendix A). Each wa e ing was collec ed sepa a ely so ha om each unnel he e was in o al i e wa e samples. Wa e samples we e hen il e ed and analysed o o al ni ogen (ammonium + ni a e +ni i e mg L −1 ). The da a we e s a is ically analysed by linea mixed model analysis. In he model (comple ely andomized design), he ea men ( e ilize s) and he wa e ing ime we e ixed ac o s and he unnel was a andom ac o . The i e wa e samples collec ed om each unnel a e no independen samples bu epea ed measu es om he same subjec hence i s -o de au o eg essi e (AR1) co a iance s uc u e was used o he wa e ing ime ac o . The da a was log- ans o med be o e he analysis. The da a analysis was pe o med using IBM SPSS S a is ics e . 25 (A monk, NY, Uni ed S a es). Recycling 2019,4, 17 5 o 11 3. Resul s and Discussion 3.1. Con en s and Leaching o Nu ien s The pseudo- o al con en s o nu ien s Calcium (Ca), po assium (K), magnesium (Mg), phospho us (P), sulphu (S), and ni ogen (N) a e p esen ed in Table 3. The SD g anule con ained only e y small amoun s o Ca, K, P o Mg, bu he ammonium sul a e addi ion was clea ly isible as high N and S concen a ions. A mass ac ion o 7.0% and 7.2% o N was achie ed wi h he SD and FASD g anules. The phospho ic acid unc ioned also well, since a mass ac ion o 2.5% o N was measu ed in he FAPA g anule and he P con en was inc eased 573% compa ed o he FA g anule. The downside is ha , as mo e phospho us is added, he po assium concen a ion is dec eased (due o he dilu ion). Since he con en o K and P was qui e low in he o iginal FA, he g anule does no comple ely ul ill he Finnish limi alues o K +P. The Ca con en exceeded he minimum equi emen s o Finnish Fe ilize P oduc Dec ee 24/2011 [ 30 ] o o es e ilize s. Finnish legisla ion does no ecognize SD-based e ilize s, bu he closes classi ica ion is o ganic mine al e ilize s (a mix u e o o ganic and mine al nu ien s). They mus con ain a mass ac ion o a leas 7% N +P+K, which is ul illed he e. C:N a ios o he g anules we e 0.06 o FAPA; 4.29 o SD; and 3.37 o FASD. Table 3. Pseudo- o al con en s o nu ien s Ca, K, Mg, P, S, and o al con en s o N in he e ilize g anules and he limi alues o Finnish Fe ilize P oduc Dec ee 24/2011 o ash e ilize s used in sil icul u e [19]. G anule Ca (g kg−1) K (g kg−1) P (g kg−1) Mg (g kg−1) S (g kg−1)N (mass ac ion (%)) FA 83.9 8.05 9.97 14.7 7.89 0.0 FAPA 76.7 5.67 67.1 13.8 38.8 2.5 FASD 37.6 2.72 24.6 5.45 75.8 7.2 SD 0.82 0.58 0.07 0.70 113 7.0 Limi alue ≥60 K +P≥20 The o al bioa ailabili y ( P F i ) and he amoun s o easily bioa ailable (F1 +F2) he nu ien s Ca, K, Mg, P, and S a e p esen ed in Table 4. Sulphu was almos comple ely in easily bioa ailable o m in all g anules. The amoun o easily soluble phospho us was also high in g anules FAPA (28.9 g · kg −1 ) and FASD (11.1 g · kg −1 ) due o he PA addi ion. PA inc eased also he amoun o easily bioa ailable Ca, K and Mg e en hough hei pseudo- o al concen a ion was smalle han in FA. The e o e, he quick-ac ing e ilize e ec inc eases conside ably a e PA addi ion. The leaching es shows ha , om bo h he comme cial e ilize (salpe e) and he SD sample ((NH4)2SO4 in SD), ni ogen leached apidly, bu , in SD, ni ogen emained a bi longe be o e eaching he ze o concen a ion (Figu e 1). This is seen also in he s a is ical analysis ha shows ha no only ea men ( e ilize ) and wa e ing bu also hei in e ac ion is s a is ically signi ican (sig. <0.05, Table A1 in Appendix B). This esul sugges s ha ni ogen abso bed o SD is mo e slowly eleased han N in comme cial salpe e. This was also obse ed when doing he wa e ing: salpe e g anules dissol ed mo e o less comple ely al eady du ing he i s wa e ing. The amoun o wa e used in he ial (5 × 1.58 li es =7.9 li es) equals o he amoun o summe ime p ecipi a ion in Ro aniemi whe e he leaching ial was ca ied ou . Thus, he ac ha comme cial e ilize dissol ed his easily sugges s ha , in o es s, i can ac ually o ally dissol e al eady du ing he i s ain, whe eas N in SD is leached mo e e enly du ing he g owing season. Recycling 2019,4, 17 6 o 11 Table 4. Amoun s o easily bioa ailable ac ions and o al bioa ailabili y o nu ien s Ca, K, Mg, P, and S; s anda d de ia ions a e in pa en heses. G anule Ca (g kg−1) K (g kg−1) P (g kg−1) Mg (g kg−1) S (g kg−1) FA Easily bioa ailable (F1 +F2) 36.0 ±0.9 0.87 ±0.03 2.69 ±0.07 0.110 ±0.001 6.49 ±0.22 To al bioa ailabili y (F1 +F2 +F3 +F4) 60.5 ±0.2 3.12 ±0.01 3.94 ±0.01 5.24 ±0.08 6.89 ±0.22 FAPA Easily bioa ailable (F1 +F2) 44.5 ±0.1 1.58 ±0.05 5.81 ±0.1 28.9 ±0.5 36.3 ±0.7 To al bioa ailabili y (F1 +F2 +F3 +F4) 59.8 ±0.2 3.40 ±0.04 6.36 ±0.01 44.3 ±0.3 36.4 ±0.7 FASD Easily bioa ailable (F1 +F2) 29.5 ±0.1 1.19 ±0.01 2.82 ±0.09 11.1 ±0.1 79.7 ±1.4 To al bioa ailabili y (F1 +F2 +F3 +F4) 34.8 ±0.4 2.12 ±0.07 3.46 ±0.2 20.5 ±0.1 80.1 ±1.4 SD Easily bioa ailable (F1 +F2) 0.71 ±0.01 0.55 ±0.01 0.59 ±0.01 0.04 ±0.01 136.6 ±2.9 To al bioa ailabili y (F1 +F2 +F3 +F4) 0.72 ±0.01 0.55 ±0.01 0.59 ±0.01 0.04 ±0.01 136.8 ±2.9 Recycling2019,4,xFORPEERREVIEW6o 11 Theleaching es shows ha , ombo h hecomme cial e ilize (salpe e)and heSDsample ((NH4)2SO4inSD),ni ogenleached apidly,bu ,inSD,ni ogen emainedabi longe be o e eaching heze oconcen a ion(Figu e1).Thisisseenalsoin hes a is icalanalysis ha shows ha  no only ea men ( e ilize )andwa e ingbu also hei in e ac ioniss a is icallysigni ican (sig. <0.05,TableA1inAppendixB).This esul sugges s ha ni ogenabso bed oSDismo eslowly eleased hanNincomme cialsalpe e.Thiswasalsoobse edwhendoing hewa e ing:salpe e g anulesdissol edmo eo lesscomple elyal eadydu ing he i s wa e ing.Theamoun o wa e  usedin he ial(5×1.58li es=7.9li es)equals o heamoun o summe imep ecipi a ionin Ro aniemiwhe e heleaching ialwasca iedou .Thus, he ac  ha comme cial e ilize dissol ed hiseasilysugges s ha ,in o es s,i canac ually o allydissol eal eadydu ing he i s  ain, whe easNinSDisleachedmo ee enlydu ing heg owingseason.  Figu e1.Concen a iono  o alni ogen(NH4‐N+NO2‐N+NO3‐N,mgL−1)inwa e collec edon i e occasionsbelow unnelson opo whichsalpe eo ammoniumsulpha eabso bed osawdus we e posi ioned.Funnelswi hno e ilize s unc ionedascon ol ea men .The aluesa emean(±1SE) o  h ee eplica es(SE=S anda de o ). 3.2.Con en sandLeachingo Ha m ulElemen s Thepseudo‐ o alcon en so nu ien sha m ulelemen sa senic(As),cadmium(Cd),ch ome (C ),coppe (Cu),nickel(Ni),lead(Pb),andzinc(Zn)a ep esen edinTable5.Allha m ulelemen  concen a ionswe ewellbelow helimi  alueso Finnish e ilize dec ee o bo h o es and ield e ilize sand,especiallyin heSDg anule, heconcen a ionswe e e ylow.Oneconce nwas ha  hephospho icacidwouldinc ease hesolubili yo ha m ulelemen s,bu ins ead hesolubili ies we esmalle .Thisismos likelydue o he o ma iono  hegeopolyme s uc u eand hedilu ion e ec causedbyphospho icacidaddi ion.Howe e ,indus ial‐g adephospho icacidis ypically usedin he e ilize indus y,whichcancon ainmo eimpu i ies han heanaly ical‐g adeacidused he e.The e o e, heleachingo ha m ulelemen scanbesomewha la ge  hanin hiss udy,s ill, he phospho icacidi sel doesno inc ease heleachingo elemen s. Table5.Pseudo‐ o alcon en so ha m ulelemen sAs,Cd,C ,Cu,Ni,Pb,andZnand helimi  alues o FinnishFe ilize P oduc Dec ee24/2011[19]. Figu e 1. Concen a ion o o al ni ogen (NH 4 -N +NO 2 -N +NO 3 -N, mg L −1 ) in wa e collec ed on i e occasions below unnels on op o which salpe e o ammonium sulpha e abso bed o sawdus we e posi ioned. Funnels wi h no e ilize s unc ioned as con ol ea men . The alues a e mean (±1 SE) o h ee eplica es (SE =S anda d e o ). 3.2. Con en s and Leaching o Ha m ul Elemen s The pseudo- o al con en s o nu ien s ha m ul elemen s a senic (As), cadmium (Cd), ch ome (C ), coppe (Cu), nickel (Ni), lead (Pb), and zinc (Zn) a e p esen ed in Table 5. All ha m ul elemen concen a ions we e well below he limi alues o Finnish e ilize dec ee o bo h o es and ield e ilize s and, especially in he SD g anule, he concen a ions we e e y low. One conce n was ha he phospho ic acid would inc ease he solubili y o ha m ul elemen s, bu ins ead he solubili ies we e smalle . This is mos likely due o he o ma ion o he geopolyme s uc u e and he dilu ion e ec caused by phospho ic acid addi ion. Howe e , indus ial-g ade phospho ic acid is ypically used in he e ilize indus y, which can con ain mo e impu i ies han he analy ical-g ade acid used Recycling 2019,4, 17 7 o 11 he e. The e o e, he leaching o ha m ul elemen s can be somewha la ge han in his s udy, s ill, he phospho ic acid i sel does no inc ease he leaching o elemen s. Table 5. Pseudo- o al con en s o ha m ul elemen s As, Cd, C , Cu, Ni, Pb, and Zn and he limi alues o Finnish Fe ilize P oduc Dec ee 24/2011 [19]. As (mg kg−1) Cd (mg kg−1) C (mg kg−1) Cu (mg kg−1) Ni (mg kg−1) Pb (mg kg−1) Zn (mg kg−1) FA 18 1.4 66 76 47 33 270 FAPA 17 1.8 52.2 64.6 44.2 22.3 217 FASD 7.2 0.67 21.2 34.9 16.5 8.7 95.4 SD <1.05 <0.07 1.2 0.71 46 <1.03 8.42 Limi alue Field/ o es e ilize s 25/40 2.5/25 300/300 600/700 100/150 100/150 1500/4500 Sequen ial ex ac ion esul s o he ha m ul elemen s As, Cd, C , Cu, Ni, Pb, and Zn a e p esen ed in Table 6. Due o p oblems in he sequen ial leaching p ocedu e, he F4 ac ion o FA g anule is based on a single measu emen . Fo SD g anule, he sequen ial ex ac ion esul s we e mainly below he de ec ion limi s. Howe e , Ni seemed o be in a highly soluble o m. The sou ce o Ni in SD g anules was mos likely he lignosul ona e powde since a di e en ba ch o lignosul ona e was used o he SD and FASD g anules. In bo h FAPA and FASD, he amoun o easily soluble ha m ul elemen s was e y small compa ed o he pseudo- o al con en s. In addi ion, he o al bioa ailabili ies o C , Cu, Ni, Pb and Zn we e small. The e o e, he leaching o ha m ul elemen s would no cause en i onmen al isks in e ilize s use. Table 6. Sequen ial ex ac ion esul s o ha m ul elemen s As, Cd, C , Cu, Ni, Pb, and Zn. S anda d de ia ions a e in pa en heses. As (mg kg−1) Cd (mg kg−1) C (mg kg−1) Cu (mg kg−1) Ni (mg kg−1) Pb (mg kg−1) Zn (mg kg−1) FA F1 <1.2 <0.04 0.4 ±0.1 <0.1 <0.1 <0.4 <0.1 F2 <1.2 0.41 ±0.01 0.9 ±0.1 2.9 ±0.1 2.7 ±0.1 0.9 ±0.1 19 ±1 F3 5.2 ±0.1 0.33 ±0.01 1.8 ±0.1 7.3 ±0.5 0.9 ±0.1 9.0 ±1 18 ±1 F4 <1.5 <0.05 1.0 2.5 0.3 3.5 3.1 FAPA F1 2.0 ±0.1 0.04 ±0.01 0.08 ±0.01 7.1 ±0.4 1.9 ±0.1 <0.40 0.10 ±0.01 F2 1.2 ±0.1 0.21 ±0.01 0.08 ±0.01 1.3 ±0.1 1.3 ±0.1 <0.40 29 ±0.9 F3 3.4 ±0.1 0.15 ±0.01 7.5 ±0.1 5.3 ±0.1 0.85 ±0.01 5.5 ±0.1 17 ±1 F4 2.0 ±0.1 0.06 ±0.01 5.2 ±0.9 5.8 ±0.8 1.6 ±0.5 3.3 ±0.2 9.0 ±2.6 FASD F1 3.1 ±0.1 0.04 ±0.01 0.08 ±0.01 0.08 ±0.01 1.3 ±0.1 <0.39 <0.1 F2 1.2 ±0.1 0.27 ±0.01 0.08 ±0.01 1.2 ±0.1 3.2 ±0.1 <0.39 11 ±1 F3 7.5 ±0.1 0.74 ±0.01 5.4 ±0.1 12 ±1 0.98 ±0.01 2.6 ±0.01 57 ±1 F4 1.5 ±0.1 0.05 ±0.01 1.8 ±0.1 0.77 ±0.06 0.36 ±0.06 1.8 ±0.1 1.7 ±0.1 SD F1 <1.2 <0.04 0.83 ±0.03 0.37 ±0.08 40 ±1<0.39 7.9 ±0.1 F2 <1.2 <0.04 <0.08 0.08 ±0.01 2.4 ±0.3 <0.39 0.56 ±0.07 F3 <1.2 <0.04 <0.08 0.13 ±0.02 0.71 ±0.15 <0.39 0.16 ±0.06 F4 <1.5 <0.05 <0.10 0.17 ±0.01 <0.15 <0.49 0.16 ±0.06 4. Conclusions Recycled ni ogen e ilize s we e manu ac u ed om indus ial side-s eams (sawdus (SD), ly-ash (FA), ammonium sul a e and lignosul ona e). Phospho ic acid (PA) was used o con ol he pH and o add ex a phospho us o he g anules. Bioa ailabili y o nu ien s and hea y me als om ecycled e ilize s was s udied using leaching es s. A mass ac ion o up o 7.0% o N was achie ed Recycling 2019,4, 17 8 o 11 wi h he SD g anule and 7.2% wi h he FA-SD g anule, indica ing ha he g anules would be well sui ed o be used as ni ogen-con aining e ilize s. Ni ogen elease om SD g anule was mo e con olled han om comme cial salpe e, indica ing ha N is eleased om he SD g anule mo e e enly du ing he g owing season han om comme cial salpe e. P and K concen a ions o FAPA g anule (72.8 g kg −1 K+P) and FASD g anule (27.3 g kg −1 K+P) clea ly exceeded he Finnish limi alues o o es e ilize s (limi alue K +P ≥ 20 g kg −1 ). Sulphu was almos comple ely in easily bioa ailable o m in all g anules. The amoun o easily soluble phospho us was also high in g anules FAPA (28.9 g · kg −1 ) and FASD (11.1 g kg −1 ) due o he PA addi ion. SD combined wi h FA can hence gi e a balanced nu ien mix when used oge he . Bioa ailabili ies and pseudo- o al con en s o ha m ul elemen s (As, Cd, C , Cu, Ni, Pb, and Zn) we e small in all g anules and caused no ha m in ield o o es e ilize use. PA dec eased he bioa ailabili ies o ha m ul elemen s due o he o ma ion o he geopolyme s uc u e and he dilu ion e ec caused by PA addi ion. Au ho Con ibu ions: Concep ualiza ion, J.P. and P.R.; me hodology, J.P. and P.R.; in es iga ion, J.P. and P.R.; w i ing—o iginal d a p epa a ion, J.P.; w i ing— e iew and edi ing, P.R.; unding acquisi ion, P.R. Funding: This wo k was done unde he auspices o he Bio uhka (Bioash) ERDF P ojec (p ojec no: A70101, unded by No h Os obo hnia Cen e o Economic De elopmen , T anspo and he En i onmen ; Napapii in Vesi ja Ene gia L d.; Napapii in Residuum L d. and Ro aniemen Kehi ys L d.). Acknowledgmen s: The s a a he Na u al Resou ces Ins i u e Finland labo a o y in Ro aniemi and in Van aa a e acknowledged o he labo a o y analyses. Con lic s o In e es : The au ho s decla e no con lic o in e es . The unde s had no ole in he design o he s udy; in he collec ion, analyses, o in e p e a ion o da a; in he w i ing o he manusc ip , o in he decision o publish he esul s. Appendix A Recycling2019,4,xFORPEERREVIEW8o 11 e enlydu ing heg owingseason han omcomme cialsalpe e.PandKconcen a ionso FAPA g anule(72.8gkg −1 K+P)andFASDg anule(27.3gkg −1 K+P)clea lyexceeded heFinnishlimi  alues o  o es  e ilize s(limi  alueK+P≥20gkg −1 ).Sulphu wasalmos comple elyineasily bioa ailable o minallg anules.Theamoun o easilysolublephospho uswasalsohighing anules FAPA(28.9g∙kg −1 )andFASD(11.1gkg −1 )due o hePAaddi ion.SDcombinedwi hFAcanhence gi eabalancednu ien mixwhenused oge he .Bioa ailabili iesandpseudo‐ o alcon en so  ha m ulelemen s(As,Cd,C ,Cu,Ni,Pb,andZn)we esmallinallg anulesandcausednoha min ieldo  o es  e ilize use.PAdec eased hebioa ailabili ieso ha m ulelemen sdue o he o ma iono  hegeopolyme s uc u eand hedilu ione ec causedbyPAaddi ion. Au ho Con ibu ions:Concep ualiza ion,J.P.andP.S.;me hodology,J.PandP.S.;in es iga ion,J.PandP.S.; w i ing—o iginald a p epa a ion,J.P.;w i ing— e iewandedi ing,P.S.; undingacquisi ion,P.S. Funding:Thiswo kwasdoneunde  heauspiceso  heBio uhka(Bioash)ERDFP ojec (p ojec no:A70101, undedbyNo hOs obo hniaCen e o EconomicDe elopmen ,T anspo and heEn i onmen ;Napapii in VesijaEne giaL d.;Napapii inResiduumL d.andRo aniemenKehi ysL d.). Acknowledgmen s:Thes a a  heNa u alResou cesIns i u eFinlandlabo a o yinRo aniemiandinVan aa a eacknowledged o  helabo a o yanalyses. Con lic so In e es :Theau ho sdecla enocon lic o in e es .The unde shadno olein hedesigno  he s udy;in hecollec ion,analyses,o in e p e a iono da a;in hew i ingo  hemanusc ip ,o in hedecision o publish he esul s. AppendixA  Figu e A1. Con . Recycling 2019,4, 17 9 o 11 Recycling2019,4,xFORPEERREVIEW9o 11  Figu eA1.Expe imen alse ‐upin heleachingexpe imen showing henine unnels( oppic u e) ha we e illedwi hine qua zsandonwhich he e ilize swe eposi ionedo le emp y(con ol). Wa e leaching h ough he unnelswascollec ed oglassbo lesplacedbelow he unnelsbe o e eachwa e ing(bo ompic u e). AppendixB TableA1.Resul so analysiso  a iance o  he o alni ogenconcen a ions(log‐ ans o medmgl‐ 1)in hewa e samplescollec edin helabo a o yexpe imen .Fo  ea men ( e ilize ),wa e ing imeand hei in e ac iond (nume a o /denume a o ),F‐ alueand hesigni icanceisgi en. Sou ced FSig. In e cep 1/4.619.880.008 T ea men 2/4.6104.310.000 Wa e ing4/17.922.620.000 T ea men ×Wa e ing8/17.93.980.007 Re e ences 1. Eu opeanCommissionCi cula EconomyS a egy.A ailableonline: h p://ec.eu opa.eu/en i onmen /ci cula ‐economy/index_en.h m(accessedon19Feb ua y2018). 2. Eu opeanCommission.Di ec i e2008/98/ECo  heEu opeanPa liamen ando  heCouncilo 19No embe 2008 onWas eandRepealingCe ainDi ec i es;Eu opeanCommission:B ussels,Belgium,2008. 3. Wood,S.;Cowie,A.ARe iewo G eenhouseGasEmissionFac o s o Fe ilise P oduc ion;IEABioene gyTask 38:Sydney,Aus alia,2004. 4. Aho,M.;Pu sula,T.;Saa io,M.;Mille ,T.;Kumpulainen,A.;Päällysaho,M.;Au io,M.;Hillg en,A.; Descombes,L.Ra in eidenKie onTaloudellinenA ojaMahdollisuude SUOMELLE(EconimicValueand Possibili eso Nu ien Recycling o Finland);Si ansel i yksiä;Si a:Helsinki,Finland,2015;p.50. 5. Ojala,E.Sel i yspuu‐jaTu e uhkanLannoi e‐SekäMuus aHyö ykäy ös ä(Repo on heU iliza iono Wood andPea BasedAshasAFe ilize andinO he Applica ions);Mo i a:Helsinki,Finland,2010. 6. Sanna,M.;Venelampi,O.;Iho,A.;Koikkalainen,K.;Leh onen,E.;Luos a inen,S.;Rasia,K.;Sa i,M.; Tampio,E.;Tu ola,E.;e al.Koh iRa in eidenKie ä yksenLäpimu oa(Towa ds heB eak h ougho Nu en  Recycling);Luonnon a a‐jabio alouden u kimus:Helsinki,Finland,2017. 7. Hannam,K.D.;Deschamps,C.;Kwia on,M.;Venie ,L.A.;Hazle ,P.W.Regula ionsandGuidelines o  he Useo WoodAshasASoilAmendmen inCanadianFo es s;In o ma ionRepo GLC‐X‐17;Na u alResou ces Canada,CanadianFo es Se ice,G ea LakesFo es yCen e:O awa,ON,Canada,2016.  Figu e A1. Expe imen al se -up in he leaching expe imen showing he nine unnels ( op pic u e) ha we e illed wi h ine qua z sand on which he e ilize s we e posi ioned o le emp y (con ol). Wa e leaching h ough he unnels was collec ed o glass bo les placed below he unnels be o e each wa e ing (bo om pic u e). Appendix B Table A1. Resul s o analysis o a iance o he o al ni ogen concen a ions (log- ans o med mg l-1) in he wa e samples collec ed in he labo a o y expe imen . Fo ea men ( e ilize ), wa e ing ime and hei in e ac ion d (nume a o /denume a o ), F- alue and he signi icance is gi en. Sou ce d F Sig. In e cep 1/4.6 19.88 0.008 T ea men 2/4.6 104.31 0.000 Wa e ing 4/17.9 22.62 0.000 T ea men ×Wa e ing 8/17.9 3.98 0.007 Re e ences 1. Eu opean Commission Ci cula Economy S a egy. A ailable online: h p://ec.eu opa.eu/en i onmen / ci cula -economy/index_en.h m (accessed on 19 Feb ua y 2018). 2. Eu opean Commission. Di ec i e 2008/98/EC o he Eu opean Pa liamen and o he Council o 19 No embe 2008 on Was e and Repealing Ce ain Di ec i es; Eu opean Commission: B ussels, Belgium, 2008. 3. Wood, S.; Cowie, A. A Re iew o G eenhouse Gas Emission Fac o s o Fe ilise P oduc ion; IEA Bioene gy Task 38: Sydney, Aus alia, 2004. 4. Aho, M.; Pu sula, T.; Saa io, M.; Mille , T.; Kumpulainen, A.; Päällysaho, M.; Au io, M.; Hillg en, A.; Descombes, L. Ra in eiden Kie on Taloudellinen A o ja Mahdollisuude SUOMELLE (Econimic Value and Possibili es o Nu ien Recycling o Finland); Si an sel i yksiä; Si a: Helsinki, Finland, 2015; p. 50. 5. Ojala, E. Sel i ys puu- ja Tu e uhkan Lannoi e- Sekä Muus a Hyö ykäy ös ä (Repo on he U iliza ion o Wood and Pea Based Ash as A Fe ilize and in O he Applica ions); Mo i a: Helsinki, Finland, 2010. 6. Sanna, M.; Venelampi, O.; Iho, A.; Koikkalainen, K.; Leh onen, E.; Luos a inen, S.; Rasia, K.; Sa i, M.; Tampio, E.; Tu ola, E.; e al. Koh i Ra in eiden Kie ä yksen Läpimu oa (Towa ds he B eak h ough o Nu en Recycling); Luonnon a a- ja bio alouden u kimus: Helsinki, Finland, 2017. 7. Hannam, K.D.; Deschamps, C.; Kwia on, M.; Venie , L.A.; Hazle , P.W. Regula ions and Guidelines o he Use o Wood Ash as A Soil Amendmen in Canadian Fo es s; In o ma ion Repo GLC-X-17; Na u al Resou ces Canada, Canadian Fo es Se ice, G ea Lakes Fo es y Cen e: O awa, ON, Canada, 2016. 8. Ka l un, E.; Saa salmi, A.; Inge sle , M.; Mand e, M.; Ande sson, S.; Gai nieks, T.; Ozolinˇcius, R.; Va nagi y e-Kabasinskiene, I. Wood Ash Recycling—Possibili ies and Risks. In Sus ainable Use o Fo es Biomass o Ene gy: A Syn hesis wi h Focus on he Bal ic and No dic Region; Röse , D., Asikainen, A., Eds.; Sp inge Ne he lands: Do d ech , The Nede land, 2008; pp. 79–108. ISBN 978-1-4020-5054-1.