Hydrothermal gasification of different agricultural wastes in supercritical water media for hydrogen production: a comparative study

Abstract

Conversion of different agricultural residues including almond shell, walnut shell, barley straw, canola stalk, rice straw and wheat straw to hydrogen-rich gas was performed via gasification in supercritical water media in a determined condition. Elemental characterization was performed using CHNSO analyzer. Besides, cellulose and lignin contents in biomass structure were determined according to TAPPI test methods T264cm-97 and T222om-02, respectively. The correlations between the yields of the product gas components with C/H/O ratio in the initial forms of used feedstocks were investigated. In addition, the relation between the components of biomass structure with the yields of main gaseous products was also studied for each feedstock. The maximum hydrogen yield of 8.38 mmol/g was observed for barley straw which has the highest H percentage of 6.5 wt%. Canola stalk with the highest C/H ratio showed the highest total gas yield of 25.3 mmol/g. Canola stalk with highest amount of cellulose and hemicellulose of 67.42 % had the highest CGE of 45 % and barley straw had the highest HGE of 20 %. Higher C/H value and lower oxygen percentage in the initial form of feedstocks resulted in higher total gas and CO 2 yields and lower hydrogen yields. Lignin content in the initial form of the feedstocks was inversely proportional with total gas yields whereas cellulose content showed a straight relation with the total gas yield.

An evaluation of subcritical hydrothermal treatment of end-of-pipe palm oil mill effluent

“…Firstly, POME contains higher lignin-to-cellulose ratio compared to the other agricultural fibrous residues (Wong et al., 2008). Biomass with higher composition of cellulose and hemicellulose would produce more H 2 , while H 2 yield will be inhibited by the existence of lignin in the structure of biomass (Salimi et al., 2016). Another reason for the low volume of H 2 generated was due to the absence of catalyst in this range of temperature.…”

Review of supercritical water gasification with lignocellulosic real biomass as the feedstocks: Process parameters, biomass composition, catalyst development, reactor design and its challenges

“…Lignin is a three-dimensional phenyl propane polymer with ester bond links. It holds cellulose and hemicellulose together in a matrix which forms primary cell walls to prevent plant from damages [37]. Cellulose, however, is made of glucose subunits which are linked together with β-1,4-glycosidic bonds that can hydrolyse much more easily into fermentable sugars [37].…”

“…It holds cellulose and hemicellulose together in a matrix which forms primary cell walls to prevent plant from damages [37]. Cellulose, however, is made of glucose subunits which are linked together with β-1,4-glycosidic bonds that can hydrolyse much more easily into fermentable sugars [37]. It has been reported that hydrolysis of cellulose and hemicellulose proceeds within seconds whereas lignin requires minutes [33].…”

Supercritical Water Gasification as Treatment for High Lipid Content Biomass in the Presence of Nickel Catalyst

“…From the elemental analysis, canola oil was composed of C (77.51%), H (11.62%) and O (10.87%) which led to a chemical formula of CH 1.79 O 0.11 . In addition, the canola oil exhibits high H/C ratio, which according to Salimi et al (2016), results in high total gas yields due to better gasi cation e ciency. e composition of the canola oil, tabulated in Table 1, was analyzed in detail by GC/MS and HPLC analysis, respectively.…”