• Energy Research

Abstract Hydrogen (H2) is considered as a zero-emission fuel when produced through biomass pyrolysis. The objective of this review article is to analyze the potential of the pyrolysis process in terms of H2 yield, the maturity of technology, current challenges, future perspective, and its commercialization potential. This review article has three folds. Firstly, a comprehensive overview of the technical state-of-the-art analysis of biohydrogen production from biomass pyrolysis process is presented. Secondly, the technical and critical review of both the conventional fast and slow pyrolysis for H2 production from the viewpoint of mechanisms, catalysts, reactors, and process parameters is provided. Thirdly, the technical readiness level for bio-oil, char, and H2 production is presented. Finaly, challenges and future prospectives are highlighted for further research for researchers and the networking of stakeholders for commercialization to guide policymakers, investors, and commercial enterprises.

The thermal degradation behaviour and kinetic parameter of non-catalytic and catalytic pyrolysis of rice husk (RH) using rice hull ash (RHA) as catalyst were investigated using thermogravimetric analysis at four different heating rates of 10, 20, 50 and 100 K/min. Four different iso conversional kinetic models such as Kissinger, Friedman, Kissinger-Akahira-Sunose (KAS) and Ozawa-Flynn-Wall (OFW) were applied in this study to calculate the activation energy (EA) and pre-exponential value (A) of the system. The EA of non-catalytic and catalytic pyrolysis was found to be in the range of 152-190 kJ/mol and 146-153 kJ/mol, respectively. The results showed that the catalytic pyrolysis of RH had resulted in a lower EA as compared to non-catalytic pyrolysis of RH and other biomass in literature. Furthermore, the high Gibb's free energy obtained in RH implied that it has the potential to serve as a source of bioenergy production.

ABSTRACT (200 words) Synergistic effects and kinetic parameters for binary mixtures of corn cob and high-density polyethylene (HDPE) in co-pyrolysis with the presence of renewable chicken and duck eggshell catalyst are evaluated using thermogravimetric analysis (TGA) approach at various heating rates (10–200 K/min) in temperature range of 323–1173 K. Weight average global process model based on two-stage kinetic scheme are employed in this study. The reaction mechanisms involved in the co-pyrolysis process are 1-D diffusion for second stage of thermal degradation and 3-D diffusion for third stage of the thermal degradation. The difference in the experimental and estimated values of the catalytic corn cob and HDPE mixtures in terms of weight loss indicates the existence of the synergistic effects during the pyrolysis process. The values of the activation energy for pure corn cob, pure HDPE, binary mixtures of corn cob and HDPE are reported in the range of 43.61–83.03, 412.32–510.72, and 28.98–93.18 kJ/mol, respectively. Meanwhile, the activation energy for catalytic pyrolysis process are in the range of 28.98–113.17 and 23.65–119.50 kJ/mol respectively in the presence of chicken and duck eggshells as catalyst. Additionally, artificial neural network (ANN) and joint optimization modelling are also utilized to validate and optimize the results from the TGA.

AbstractPrior information on the pyrolysis product behaviour of biomass components-cellulose, hemicellulose and lignin is critical in the selection of feedstock as components have a significant influence on the pyrolysis products yield. In this study, the effect of biomass components on the yield of slow pyrolysis products (char, bio-oil and syngas) is investigated using a validated ASPEN Plus® model. The model is simulated at a temperature of 450 °C, a heating rate of 10 °C/min and a solid residence time of 30 min. The results indicated that at the given conditions, lignin contributed 2.4 and 2.5 times more char yield than cellulose and hemicellulose. The hemicellulose contributed 1.33 times more syngas yield than lignin while the cellulose and hemicellulose contributed 8.67 times more bio-oil yield than lignin. Moreover, the cost involved in the production of char using lignin (110 $/ton) is significantly economical than using cellulose (285 $/ton) and hemicellulose (296 $/ton). The net CO2emission of lignin pyrolysis is 4.14 times lower than cellulose pyrolysis and 3.94 times lower than hemicellulose pyrolysis. It can be concluded that lignin pyrolysis is more advantageous than cellulose and hemicellulose pyrolysis. In the selection of feedstock for the slow pyrolysis, the feedstock with more lignin content is preferred.Graphical abstract

Abstract Biomass gasification is a promising approach for bioenergy conversion. Usually, biomass gasification is facing interruption in feedstock supply due to seasonal availability of biomass. In biomass gasification, formation of tar also affects the gasification efficiency. Therefore, in this study, catalytic air co-gasification of two palm wastes (coconut shells; CS, oil palm fronds; OPF) was investigated for syngas (H2+CO) and methane production in downdraft gasifier using three mineral catalysts such as Portland cement, dolomite, and limestone to address the issues. The three main process variables were investigated within the specific range, the temperature of 700–900 °C, catalyst loading of 0–30 wt%, and the biomass blending ratio of 20–80 wt%. Response Surface Methodology, Box-Behnken Design was used for process optimization. The results showed that temperature was the most influencing parameter for syngas production, followed by catalyst loading and blending ratio. The maximum methane produced from Portland cement catalyst followed by limestone and dolomite. The syngas and methane yield was obtained 38.81 vol% and 19.96 vol% respectively at optimized conditions of catalyst loading of 20 wt%, temperature of 900 °C, and blending ratio of CS20:OPF80 using Portland cement as a catalyst. The higher syngas and methane yields from catalytic co-gasification as compared to non-catalyst co-gasification was due to the catalytic effect of Ca, Fe, Mg, K, P, and Al oxides present in catalysts and biomass materials.

Abstract Biomass gasification appears as a potential source of renewable and sustainable energy for green environment. Biomass steam gasification has gained significant importance in this era due to high product yield and economical viability. For commercialization of biomass steam gasification process, suitable catalyst for tar reduction, higher product yield and active life of catalyst are still hot questions. Different types of catalyst like dolomite, alkaline metal, nickel and olivine are used in biomass steam gasification. Some of them have good potential for tar elimination and others are good in higher product yield. Most of the catalysts have short active life, expensive and with regeneration problem. The purpose of current study is to review the effect of different catalysts in the biomass steam gasification process used for tar elimination and higher product yield. In addition, the potential of coal bottom ash as a substitute of catalyst in biomass steam gasification is discussed.