Thermophilic biohydrogen production using pre-treated algal biomass as substrate Shantonu Roy, Kanhaiya Kumar, Supratim Ghosh, Debabrata Das* Department of Biotechnology, Indian Institute of Technology, Kharagpur 721302, India article info Article history: Received 19 August 2013 Received in revised form 5 December 2013 Accepted 8 December 2013 Available online 2 January 2014 Keywords: Algal biomass Pretreatment methods Biohydrogen production Thermophilic mixed culture Gompertz equation abstract Algal biomass is rich in carbohydrates which can be utilized as a promising source of substrate for dark fermentation. It becomes more significant when biomass is produced by capturing atmospheric greenhouse gas, CO 2 . In the present study, clean energy was generated in the form of biohydrogen utilizing algal biomass. Biohydrogen production was carried out by thermophilic dark fermentation using mixed culture. The culture of Chlorella sorokiniana was cultivated in helical airlift photobioreactor at 30  C under continuous light intensity of 120 mmol m 2 s 1 provided by white fluorescent lamps. Biomass reached to stationary phase on 9th day giving maximum dry cell weight of 2.9 kg m 3 . Maximum carbohydrate and protein content observed was 145 g kg 1 and 140 g kg 1 , respectively. Maximum volumetric productivity of 334 g dm 3 d 1 was observed. Algal biomass was subjected to various physical and chemical pre-treatments processes for the improvement of hydrogen production. It was observed that the pretreatment with 200 dm 3 m 3 HCl-heat was most suitable pretreatment method producing cumulative hydrogen of 1.93 m 3 m 3 and hydrogen yield of 958 dm 3 kg 1 volatile suspended solid or 2.68 mol mol 1 of hexose. Growth kinetics parameters such as m max and K s were estimated to be 0.44 h 1 and 120 g m 3 , respectively. The relationship between biomass and hydrogen production was simulated by the LuedekingePiret model showing that H 2 production is growth associated. The study thus showed the potential of algal biomass as substrate for biological hydrogen production. ª 2013 Elsevier Ltd. All rights reserved. 1. Introduction The recent exponential increase in worldwide energy demand caused depletion of energy reserves at greater pace. The combustion of fossil fuels has serious negative effects on environment because of CO 2 emission. Algal biomass culti- vation is gaining importance in recent times as they can capture atmospheric CO 2 and can produce carbohydrates rich biomass which can be used for production of biofuels [1]. Unlike other crops such as corn or soybeans, algae can use various water sources ranging from wastewater to brackish water and can be grown in small, intensive plots on denuded land. Hydrogen from algae is possible by two biological pro- cesses. The first is the biophotolysis involving light-driven splitting of the water [1,2]. Hydrogen production by bio- photolysis had been extensively studied on Chlamydomonas reinhardtii or Anabaena variabilis [3]. Secondly, dark fermenta- tion of biomass utilizing carbohydrates present in algal cells using thermophilic and mesophilic hydrogen producing bac- teria. Thermophilic dark fermentation shows favorable ther- modynamics of reaction and with reduced risk of * Corresponding author. Tel.: þ91 3222 83758; fax: þ91 3222 255303. E-mail addresses: ddas.iitkgp@gmail.com, ddas@hijli.iitkgp.ernet.in (D. Das). Available online at www.sciencedirect.com ScienceDirect http://www.elsevier.com/locate/biombioe biomass and bioenergy 61 (2014) 157 e166 0961-9534/$ e see front matter ª 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.biombioe.2013.12.006