Contents lists available at ScienceDirect Renewable and Sustainable Energy Reviews journal homepage: www.elsevier.com/locate/rser Role of stage-separation in the ubiquitous development of Anaerobic Digestion of Organic Fraction of Municipal Solid Waste: A critical review Biswabandhu Chatterjee ⁎ , Debabrata Mazumder 1 Department of Civil Engineering, Environmental Engineering Cell, IIEST, Shibpur, Howrah, 711103 West Bengal, India ARTICLEINFO Keywords: Biohythane Digestate OFMSW Stage-separation Three-stage AD Two-stage AD ABSTRACT Managing the ever increasing load of municipal solid waste (MSW) has been one of the biggest challenges for municipalities all over the world. According to World Bank reports, the global generation of MSW per year is expectedtoriseto2.2billiontonsby2025.Organicfractionofthemunicipalsolidwaste(OFMSW)accountsfor more than 40% of the generated MSW. Anaerobic digestion (AD) has been a popular technique for OFMSW management due to its potential to generate methane and a semi-stabilized digestate, which can be further processedasasubstituteforinorganicfertilizers.Mostoftheexistingfull-scaleADtreatmentplantsstabilizing OFMSW are single-stage based. However, with the increase in OFMSW generation-rate phase separation in AD has become more pertinent. Compared to single-stage AD systems, multi-stage AD systems are capable of not onlytreatinganincreasedloadofOFMSWbutalsoproducinggreatermethaneandbio-hydrogen.Mostrecently onlyahandfuloffull-scaleADplantsinEuropehaveshiftedtotwo-stagesystems.Efciencyintermsofenergy recoveryhasbeenreportedtobeupto94.5%and86%formulti-andsingle-stageADsystems,treatingorganic solidwaste,respectively.Thiscanbeonlyenhancedfurtheriftheoperatingconditionsoptimumforeachphase is properly maintained. In three-stage AD systems, pH suitable for hydrolysis (4–5), acidogenesis (5–6.5) and methanogenesis (6.8–7.5) can be easily maintained. Not only that, three-stage AD systems also ofer provision for variation in loading-rates and retention-times suitable for individual phases. Furthermore, multi-stage AD systems provide a scope for improved trace-element supplementation, which results in 10–50% performance increase per unit reactor volumes. The present review clearly illustrates the need to switch over to two- and three-stage AD systems for stabilizing OFMSW. 1. Introduction EarlyADofOFMSWwasmostlycarriedoutinsingle-stagedigesters. As such, till the end of the 20th century majority of the researchers worked on the development of AD of OFMSW, based on single-stage systems.Themainproblemwiththesingle-stagebasedADsystemswas low biogas production. With the increase in the demand for biogas basedenergytwo-stageADofOFMSWcameintothefore.Assuch,since thestartofthe21stcenturymostofthemajordevelopmentsinthe feld of AD of OFMSW have been based on two-stage AD systems. The se- paration of the methanogenic phase, from the hydrolytic and the acidogenicphasenotonlyledtofasterdegradationofthefeedstockbut https://doi.org/10.1016/j.rser.2019.01.026 Received 4 April 2018; Received in revised form 18 November 2018; Accepted 10 January 2019 Abbreviations: AD, Anaerobic Digestion; AcoD, Anaerobic co-digestion; AOA, Ammonia Oxidizing Archaea; AOB, Ammonia Oxidizing Bacteria; ATP, Adenosine Triphosphate; BCS, Biofertiliser Certifcation Scheme; BMP, Biomethane Potential; BOD, Biochemical Oxygen Demand; CNG, Compressed Natural Gas; COD, Chemical Oxygen Demand; CST, Continuous Stirred Type; DOC, Dissolved Organic Carbon; EBA, European Biogas Association; FA, Free Ammonia; FAN, Free Ammonia Nitrogen; FVW, Fruit and Vegetable Waste; FW, Food Waste; HRT, Hydraulic Retention Time; KW, Kitchen Waste; LCFA, Long Chain Fatty Acid; NP, NitrogenPhosphorus;OFMSW,OrganicFractionofMunicipalSolidWaste;OLR,OrganicLoadingRate;ORP,OxidationReductionPotential;PAS,PubliclyAvailable Specifcation;QP,QualityProtocol;RDF,RefuseDerivedFuel;SCFA,ShortChainFattyAcid;sCOD,solubleChemicalOxygenDemand;SHARON,SinglereactorHigh activity Ammonia Removal Over Nitrite; S-L, Solid-Liquid; SMP, Specifc Methane Production; SRT, Solids Retention Time; SS, Suspended Solids; TAN, Total AmmoniaNitrogen;tCOD,totalChemicalOxygenDemand;TE,TraceElement;TKN,TotalKjeldahlNitrogen;TN,TotalPhosphorus;TOC,TotalOrganicCarbon;TP, TotalNitrogen;TPAD,TemperaturePhasedAnaerobicDigestion;TS,TotalSolids;TSAD,Three-StageAnaerobicDigestion;UASB,Up-fowAnaerobicSludgeBlanket; VFA,VolatileFattyAcid;VS,VolatileSolids;VSS,VolatileSuspendedSolids;VW,VegetableWaste;WAS,WasteActivatedSludge;WRAP,Waste&ResourcesAction Programme ⁎ Correspondence to: Indian Institute of Engineering Science and Technology (IIEST), Shibpur, Howrah, 711103 West Bengal, India. E-mail address: debabrata@civil.iiests.ac.in (D. Mazumder). 1 Postal address: Indian Institute of Engineering Science and Technology (IIEST), Shibpur, Howrah, 711103 West Bengal, India. Renewable and Sustainable Energy Reviews 104 (2019) 439–469 1364-0321/ © 2019 Elsevier Ltd. All rights reserved. T