Hydrogen production via supercritical water gasification of almond shell over algal and agricultural hydrochars as catalysts Farid Safari a,* , Nader Javani b , Zehra Yumurtaci b a Department of Energy Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran b Faculty of Mechanical Engineering, Yildiz Technical University, Besiktas, Istanbul, Turkey article info Article history: Received 10 February 2017 Received in revised form 29 April 2017 Accepted 14 May 2017 Available online xxx Keywords: Supercritical water Gasification Almond shell Hydrochar Catalyse abstract Almond shell is one of the most abundant agricultural wastes in Kurdistan province of Iran. Conversion of almond shell into hydrogen-rich gas via supercritical water gasification (SCWG) was investigated in this study using a tubular batch micro-reactor system. Non- catalytic tests were carried out in different conditions to determine the optimum condi- tion for H 2 production. Maximum hydrogen yield of 7.85 mmol/g, was observed in the temperature of 460  C, residence time (RT) of 10 min and feed/water ratio (F/W) of 0.01. Catalytic experiments were performed using hydrochars as solid residues remained after SCWG of Cladophora glomerata (C. glomerata) macroalgae and wheat straw. Hydrochars were characterized by ICP-OES, FESEM and BET methods. For catalytic experiments, hydrochars were added to the almond shell by the weight ratio of 0.4. Conversion of almond shell and hydrogen production, were more influenced by the presence of inorganic compounds in the hydrochars rather than the surface area and pore volume. The maximum hydrogen yields of 10.77 and 11.63 mmol/g, were observed for catalytic exper- iments in the presence of wheat straw and C. glomerata hydrochars, respectively. © 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. Introduction Development in all aspects of the energy, including produc- tion, conservation and utilization, is one of the most crucial concerns in the recent era [1,2]. Hydrogen is known for its versatility to be a suitable alternative for conventional fossil fuel [3,4]. Hydrogen is one of the most environmentally benign, efficient and promising energy carriers [5]. Nowadays, more than 90% of the hydrogen worldwide is made via steam reforming of methane which comes from fossil fuels [6]. Developing the advanced processes for production of hydrogen from renewables can be a great leap forward toward the sustainable energy development [7]. Biomass is regarded by many scientists as a green source of energy with almost zero carbon emission in its carbon life cycle [8]. Unlike solar energy, biomass has no time limitation. This source of energy contains significant amount of carbon and hydrogen, makes it favorable for production of fuels and chemicals [9]. Almond shell as an agricultural waste of the Kurdistan province of Iran with a production of about 200,000 tons annually, is a valuable source of chemicals and energy carriers [10]. Therefore, due to the growing demand for energy especially renewable energy, effi- cient conversion of these bio-renewable resources can be a * Corresponding author. Fax: þ98 21 44861681. E-mail address: farid.safari89@gmail.com (F. Safari). Available online at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy xxx (2017) 1 e10 http://dx.doi.org/10.1016/j.ijhydene.2017.05.102 0360-3199/© 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. Please cite this article in press as: Safari F, et al., Hydrogen production via supercritical water gasification of almond shell over algal and agricultural hydrochars as catalysts, International Journal of Hydrogen Energy (2017), http://dx.doi.org/10.1016/j.ijhydene.2017.05.102