Algae as promising feedstocks for fermentative biohydrogen production according to a biorefinery approach: A comprehensive review Cecilia Sambusiti a,n , Micol Bellucci a , Anastasia Zabaniotou a,b , Luciano Beneduce a , Florian Monlau a a STAR Agroenergy Research Group, University of Foggia, Via Gramsci, 89-91, 71121 Foggia, Italy b Department of Chemical Engineering, Aristotle University of Thessaloniki, Greece article info Article history: Received 14 August 2014 Received in revised form 18 November 2014 Accepted 12 December 2014 Keywords: Biohydrogen Biorefinery Dark fermentation Macroalgae Microalgae Pretreatment abstract Interest is growing in the production of biohydrogen from algae through dark fermentation, as alternative to fossil fuels. However, one of the limiting steps of biohydrogen production is the conversion of polymeric carbohydrates into monomeric sugars. Thus, physical, chemical and biological pretreat- ments are usually employed in order to facilitate carbohydrates de-polymerization and enhancing biohydrogen production from algae. Considering the overall process, biohydrogen production through dark fermentation leads generally to negative net energy balances of the difference between the energy produced as biohydrogen and the direct ones (heat and electricity) consumed to produce it. Thus, to make the overall process economically feasible, dark fermentation of algae must be integrated in a biorefinery approach, where the outlets are valorized into bioenergy or value added biomolecules.The present study reviews recent findings on pretreatments and biohydrogen production through dark fermentation of algae looking at the perspectives of integrating side streams of dark fermentation from algal biomass, according to a biorefinery approach. & 2014 Elsevier Ltd. All rights reserved. Contents 1. Introduction ......................................................................................................... 21 2. Algae biomass ....................................................................................................... 21 2.1. Macroalgae .................................................................................................... 22 2.2. Microalgae .................................................................................................... 22 3. Dark fermentation process ............................................................................................. 23 3.1. Principles of dark fermentation ................................................................................... 23 3.2. Operational parameters of dark fermentation ........................................................................ 23 3.3. Algae intrinsic factors influencing dark fermentation .................................................................. 25 4. Biohydrogen potentials of algae ......................................................................................... 26 4.1. Pretreatments of macro and microalgae strains....................................................................... 27 4.2. Effect of pretreatment on chemical composition of algae biomass ........................................................ 27 4.3. Impact of by-products (i.e. furans, phenols) on biohydrogen performances ................................................. 27 4.4. Effect of pretreatment on biohydrogen potential ...................................................................... 28 5. Dark fermentation effluents integrated in a bio-refinery concept............................................................... 28 Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/rser Renewable and Sustainable Energy Reviews http://dx.doi.org/10.1016/j.rser.2014.12.013 1364-0321/& 2014 Elsevier Ltd. All rights reserved. Abbreviations: AD, anaerobic digestion; BHP, biological hydrogen potential; BBD, Box–Behnken design; BESA, 2-bromoethanesulfonic acid; COD, chemical oxygen demand; DF, dark fermentation; ECE, energy conversion efficiency; FHP, fermentative hydrogen potential; HMF, hydroxylmethylfurfural; HPB, hydrogen producing bacteria; HRT, hydraulic retention time; LHW, liquid hot water; MEC, microbial electrolysis cells; MFC, microbial fuel cell; MOW, mariculture organic waste; OLR, organic loading rate; PHA, polyhydroxyalkanoates; PF, photofermentation; RSM, response surface methodology; S/L, solid to liquid ratio; TS, total solids; VFA, volatile fatty acids; VS, volatile solids n Corresponding author. Present address: INRA, UMR 1208, IATE Ingenierie des Agropolymères et Technologies Emergentes, 2, Place Pierre Viala – Bât 31, 34060 Montpellier cedex 1, F-34060, France. Tel.: þ33 4 99 61 25 81; fax: þ33 4 99 61 30 76. E-mail addresses: cecilia.sambusiti@supagro.inra.fr, cecilia.sambusiti@gmail.com (C. Sambusiti), micol.bellucci@gmail.com (M. Bellucci), azampani@auth.gr (A. Zabaniotou), luciano.beneduce@unifg.it (L. Beneduce), flomonlau@hotmail.fr (F. Monlau). Renewable and Sustainable Energy Reviews 44 (2015) 20–36