Steam To Biomass Ratio Research Articles

Simulation of Olive Pomace Gasification for Hydrogen Production Using Aspen Plus: Case Study Lebanon

Biomass is a renewable energy source gaining attention for its potential to replace fossil fuels. Biomass gasification can produce hydrogen-rich gas, offering an environmentally friendly fuel for power generation, transportation, and industry. Hydrogen is a promising energy carrier due to its high energy density, low greenhouse gas emissions, and versatility. This study aims to develop a hydrogen generation plant using a dual fluidized bed gasifier, which employs steam as a gasifying agent, to convert olive pomace waste from the Lebanese olive oil industry into hydrogen. The process is simulated using Aspen Plus and Fortran coding, and it includes a drying unit, gasification unit, gas cleaning unit, steam methane reformer unit, water–gas shift reactor unit, and a pressure swing adsorption unit. The generated gas composition is verified against previous research. Sensitivity analyses are conducted to investigate the impacts of the steam-to-biomass ratio (STBR) and gasification temperature on gas composition, demonstrating a valid STBR range of 0.5 to 1 and a reasonable gasification temperature range of 700 °C to 800 °C. Further sensitivity analyses assess the impact of reformer temperature and the steam-to-carbon ratio (S/C) on the gas composition leaving the steam methane reformer.

Hydrogen-Rich Syngas Production from Gasification of Sewage Sludge: Catalonia Case

The continuous tightening of legislation regulating the agricultural usage of sewage sludge in the province of Catalonia (Spain) leads us to propose its gasification to produce hydrogen-rich syngas. A thermodynamic equilibrium model was developed using Aspen Plus® to simulate the air and steam gasification of sewage sludge from a wastewater treatment plant in Catalonia. The syngas generated is analyzed in terms of composition and lower heating value (LHV), as a function of equivalence ratio (ER), gasification temperature (Tgas), steam-to-biomass ratio (SBR), and moisture content (MC). Results show that air-blown gasification finds the highest LHV of 7.48 MJ/m3 at 1200 °C, ER of 0.2, and MC of 5%. Using steam as the gasifying agent, an LHV of 10.30 MJ/m3 is obtained at SBR of 0.2, MC of 5%, and 1200 °C. A maximum of 69.7% hydrogen molar fraction is obtained at 600 °C, MC of 25%, and SBR of 1.2. This study suggests using steam as a gasifying agent instead of air since it provides a higher LHV of the syngas as well as a hydrogen-richer syngas for the implementation of gasification as an alternative method to sewage sludge treatment in the region of Catalonia. Since the economic aspect should also be considered, in this regard, our sensitivity analysis provided important data demonstrating that it is possible to reduce the gasification temperature without significantly decreasing the LHV.

A combined approach-based techno-economic-environmental multi-optimization of a hydrogen generation system through waste biomass air-steam gasification

In this study, a biomass air-steam gasification system for hydrogen production was simulated in Aspen Plus and validated using experimental studies. Sewage sludge was considered as the biomass feed. A combined approach including the combination of the NSGA-II algorithm, the response surface methodology (RSM) and TOPSIS decision-making method, was used to multi-optimize this hydrogen production system. To optimize the performance of the system, first, mathematical equations between equivalence ratio (ER), steam to biomass ratio (SBR), and gasifier temperature as the decision variables and the mole flow of H2 and CO2 and the levelized cost of hydrogen (LCOH) as the objective functions were obtained by the RSM technique. To maximize the mole flow of H2 and minimize CO2 emission and LCOH, a multi-objective optimization using NSGA-II was conducted. The ER, SBR and gasifier temperature were analyzed in the range of 0.1–0.4, 0.2 to 2 and 600 °C–1000 °C, respectively. By employing the TOPSIS decision-making method, several optimum points were obtained by giving each of the decision variables a specific weight. The lowest LCOH was found to be 1.5 €/kg H2 at the ER of 0.103, SBR of 0.83, and gasification temperature of 956 °C.

Syngas production in a downdraft gasifier using food waste: a case study

ABSTRACT The energy production potential of some common food waste, including cooked rice, “eba,” orange, yam, and potato peels, has been studied through thermodynamic modeling and simulation. The key gasification processes were modeled individually in ASPEN PLUS. The component properties were calculated with Peng-Robinson’s equation of state. The effect of the equivalence ratio (ER), steam-to-biomass ratio (STBR), and gasifier operating temperature on the composition, cold gas efficiency (CGE), and higher heating value (HHV) of the syngas was studied. Results revealed that the production of H2 and CO2 reduces with the increase in ER and increases with STBR. The molar fraction of CO is inversely proportional to that of CO2. Increasing ER causes an increase in oxidizer within the gasifier and a corresponding increase in the molar fraction of N2. Reduction in STBR reduces both the N2 content and heating value of syngas. Syngas from both feedstocks has heating values ranging from 18.48 to 11.04 MJ/kg, with food waste yielding higher HHV than hardwood. The CGE for hardwood ranges from 55.6% to 74.95%, while for food waste, it ranges from 49.3% to 57%. This study demonstrates the production of high-quality syngas from locally sourced food waste.

Numerical Analysis of Tar and Syngas Formation during the Steam Gasification of Biomass in a Fluidized Bed

A sequential modular hydrodynamic model integrated with detailed reaction kinetics (SMHM-RK) was developed and validated to predict tar and syngas components produced by the steam gasification of biomass in a fluidized bed gasifier. The simulations showed that the prediction accuracy is sensitive to both models for hydrodynamics and reaction kinetics. The simulations showed that the tar composition predicted by the SMHM-RK was more close to the measured values than those predicted by the well-mixed hydrodynamic model integrated with the same reaction kinetics (WMHM-RK). The predictions showed that the total tar decreased, but the polycyclic aromatic tar compounds increased with the increase in gasification temperature. There was an optimum steam-to-biomass ratio (SBR) for minimizing tar formation. The simulations found that the contents of total tar and heavy tar compounds decreased by increasing the SBR from 0.3 to 0.9, and then increased by further increasing the SBR. The injection of a small amount of oxygen in steam gasification cannot reduce tar formation. The injection of oxygen in steam gasification changed the reaction pathways of naphthalene to produce more naphthalene in the syngas. The de-volatilization rate affects pyrolytic volatile compositions and subsequent tar formation. Therefore, biomass devolatilization and homogeneous gas reactions should be solved simultaneously to accurately predict the syngas and tar composition.

Process modelling integrated with interpretable machine learning for predicting hydrogen and char yield during chemical looping gasification

Chemical looping gasification (CLG) is a promising thermochemical process for the production of H2. CLG process is mainly based on oxygen transfer from an air reactor to a gasification reactor using solid metal oxides (also called oxygen carriers, (OC)) as oxidants. The unique oxygen separation system of CLG makes it an advanced process with a smaller carbon footprint compared to the conventional gasification process. The other advantages of CLG includes increased efficiency, reduced greenhouse gas emissions, and improved process stability compared to conventional biomass gasification. Although CLG is a promising technology, it still faces several challenges such as high capital cost, OC durability, complex reaction mechanism and scalability issues. Some of these challenges can be addressed by understanding the impact of various process conditions on H2 yield and char formation during CLG. The present study proposes a novel integrated process simulation and experimental studies to generate large dataset used for interpretable machine learning (ML) analysis. Three different ML models including support vector machine (SVM), random forest (RF), and gradient boost regression (GBR) were used to develop models for predicting the H2 and char yield during CLG. The GBR outperformed other models for the prediction of H2 and char yield during CLG with R2 value > 0.9. Among the experimental conditions, the temperature (T) and steam to biomass ratio (SBR) were the most relevant parameters affecting H2 and char production. Biomass ash, C, volatile matter (VM) and H content also influenced H2 and char formation. Overall, a combination of SHAP and partial dependence plot helped address the black box challenges of ML models.

Numerical simulation of biomass gasification in fluidized bed gasifiers

Numerical simulation of biomass gasification in fluidized bed reactors faces several challenges including proper modeling of the physical and chemical processes involved in the gasification and numerical stiffness of the two-phase dense particle flow problem. In this paper, the multi-phase particle-in-cell (MP-PIC) model coupled with a recently developed distribution kernel method (DKM) and a new one-step pyrolysis model are employed to investigate biomass gasification in two lab-scale fluidized bed gasifiers (FBGs). The results are evaluated by comparing with the results from the Particle Centroid Method (PCM) and experimental measurements. The performance of DKM is shown to improve the robustness of the model and the new pyrolysis model is shown to improve the sensitivity of the yields of gasification products to operating temperature. The simulation results using the new pyrolysis model agree well with the experimental data under different gasification conditions. The model is shown to be able to capture the trend of gas products with respect to variations of steam/biomass ratio (SR) and operating temperature (Tr). The mechanisms of the formation of gas products are analyzed based on the numerical results. By increasing the SR and Tr, the production of H2 and CO2 is shown to increase while the production of CO and CH4 to decrease. It is shown that varying the steam/biomass ratio in the range of 0.8∼2.0 has a minor effect on the pyrolysis process and heterogeneous reactions, while homogeneous reactions are significantly affected, leading to changes in the final composition of the gas products. Varying the gasifier temperature Tr has on the other hand a crucial effect on the pyrolysis process and as such a significant impact on the gasification products and carbon conversion.

Thermodynamic and exergetic assessment of a biomass derived syngas fueled gas turbine powered trigeneration system

Processing of waste materials for the generation of renewable fuels, and the development of trigeneration systems are known as the sustainable procedure for satisfying the diverse energy demands. In this regard, this study aims at developing and analyzing a trigeneration system which consists of a gasifier, combined power cycle, and a vapor absorption refrigeration (VAR) system. A model based on equilibrium thermodynamics was developed which has considered the tar formation and char conversion, and accordingly, composition of biomass derived syngas was predicted by employing the MATLAB software. The gasifier operating performance is assessed for the effect of change in gasification equivalence ratio (GER), steam-to-biomass ratio (SBR), and type of biomass feed. Increase in GER from 0.3 to 0.6 for saw dust gasification reduces the energy and exergy efficiencies of gasifier from 44% to 27.5%, and from 51% to 34%, respectively. Finally, a computational method for the energetic and exergetic assessment of the trigeneration was developed using the EES software and a parametric analysis was conducted. CCHP system efficiencies are found considerably influenced by change in SBR and type of biomass feed. Having 40% second law efficiency gasifier has been determined as the most exergy destructive component in the system proposed.

Performance Investigation of Biomass Gasification for Syngas and Hydrogen Production Using Aspen Plus

This study presents a reliable model using Aspen Plus process simulator capable of performing a sensitivity analysis of the downdraft gasification linked to hydrogen production unit. Effects of key factors, including gasification temperature and steam to biomass ratio (SBR) on the syngas composition, calorific value of syngas and hydrogen production are discussed and then the optimal conditions for maximum hydrogen production are extracted. The model is validated by experimental and other modeling data and found to be in great agreement. The sensitivity analysis results obtained by only using air as gasification agent indicate that higher temperatures are favorable for a product gas with higher hydrogen content and calorific value. Moreover, steam consumption as gasifying agent leads to increasing the hydrogen content and heating value of the syngas compared to the use of air as gasification agent. Finally, the results show that the optimal conditions to have the highest value of hydrogen output from sawdust downdraft gasification are 800&#730C as gasifier temperature and 0.6 for SBR.

Simulation of Sudanese Sugar Cane Bagasse Gasification Process Using ASPEN PLUS

Bagasse has traditionally inefficiently burned in boilers for steam and electricity generation which still suffers from significant inefficiencies creating; therefore there is a need for alternative processes to be analyzed. Among the biomass utilization technologies, biomass gasification is an attractive solution for utilizing biomass effectively. In this study Aspen Plus simulation package V8 was used to develop a model for the gasification of Sudanese sugar cane bagasse in a fluidized bed reactor for syngas production. The developed model is based on Gibbs free energy minimization applying the non-stoichiometric equilibrium method for optimization of the gasifier performance. The objective is to study the effect of important operating parameters including gasification temperature, steam to biomass ratio (SBR) and air to biomass ratio (ABR), on syngas composition, low heating value (LHV) of syngas and cold gas efficiency (CGE). The optimal values of syngas composition, LHV and CGE were located at gasification temperature range from 750C to 950C, steam to biomass ratio around 0.5 to 0.8 and air to biomass ratio values equal to or below 0.4.

Hydrogen Production by Fluidized Bed Reactors: A Quantitative Perspective Using the Supervised Machine Learning Approach

The current hydrogen generation technologies, especially biomass gasification using fluidized bed reactors (FBRs), were rigorously reviewed. There are involute operational parameters in a fluidized bed gasifier that determine the anticipated outcomes for hydrogen production purposes. However, limited reviews are present that link these parametric conditions with the corresponding performances based on experimental data collection. Using the constructed artificial neural networks (ANNs) as the supervised machine learning algorithm for data training, the operational parameters from 52 literature reports were utilized to perform both the qualitative and quantitative assessments of the performance, such as the hydrogen yield (HY), hydrogen content (HC) and carbon conversion efficiency (CCE). Seven types of operational parameters, including the steam-to-biomass ratio (SBR), equivalent ratio (ER), temperature, particle size of the feedstock, residence time, lower heating value (LHV) and carbon content (CC), were closely investigated. Six binary parameters have been identified to be statistically significant to the performance parameters (hydrogen yield (HY)), hydrogen content (HC) and carbon conversion efficiency (CCE) by analysis of variance (ANOVA). The optimal operational conditions derived from the machine leaning were recommended according to the needs of the outcomes. This review may provide helpful insights for researchers to comprehensively consider the operational conditions in order to achieve high hydrogen production using fluidized bed reactors during biomass gasification.

Analysis of sorbent enhanced steam assisted air gasification using biomass specific pyrolysis correlations

ABSTRACT The article presents simulation and analysis of sorbent-enhanced biomass gasification with biomass-specific pyrolysis correlations. An ASPEN plus model constituted of drying, pyrolysis, char transformation, and tar cracking is generated to analyze the effect of temperature, steam-to-biomass ratio (SBR), and equivalence ratio (ER) on syngas composition and process efficiency of sorbent enhanced steam-assisted air gasification of biomass. Yield of pyrolysis products is modeled by incorporating correlations as function of biomass composition and gasification temperature. The generated model is applied to analyze syngas composition, gas generation, and process efficiency associated with sorbent enhanced steam-assisted air gasification of three biomasses. At a temperature of 950 K, hydrogen concentration is found to be increased by 29.07%, 31.79%, and 28.31%, and carbon dioxide concentration is found to be decreased by 54.39%, 56.37%, and 54%, respectively, for sawdust, groundnut shell, and sugarcane bagasse with sorbent addition. Among the biomass considered, sugarcane bagasse is found to have the highest efficiency of 55.33%, followed by ground nut shell and sawdust with 52.01% and 48.78%, respectively.

Hybridizing power and water cogeneration plants with biomass steam gasification systems: An Energy-Water-Waste (EW2) nexus case study

Due to their fast start-up, diesel-fired gas turbine (GT) backup units are commonly used in Kuwait to satisfy increasing local power demand in utility-scale cogeneration power and water desalination plants (CPDP). This study investigates the use of syngas generated from biomass high-temperature steam gasification (HTSG) systems as fuel for the GT backup units instead of the diesel-fired units. The objective of hybridizing CPDPs with HTSG systems is to minimize fossil fuel dependence and simultaneously reduce waste discarded in landfills. The coupling of the carbon–neutral system retrofits existing power and water cogeneration plants to sustainable Energy-Water-Waste (EW2) systems. Synergies of hybridizing biomass HTSG systems with conventional CPDPs are presented and discussed in this study.A thermodynamic analysis is performed on the hybrid plant for the simultaneous generation of power and water by cofiring municipal solid waste (MSW), plastic, and used rubber tires with conventional fossil fuels. Depending on the gasifier’s feedstock and at the optimal steam-to-biomass ratio (STBR) and steam temperature, peak power capacity enhancement is calculated to be in the range of 3.40% to 4.52% when integrating a 100 MW syngas-fired GT unit with the CPDP. The results of the energy analysis show that the hybrid plant’s utilization factor ranges from 70.0% to 74.4%. The largest increase (2.52%) in the plant’s power and water gain ratio (PWGR) is achieved when rubber is gasified with 800 °C steam and an STBR of 3.82. Even though the cogeneration plant’s in-house water consumption rate increases in the range of 10.8 to 55.0% because of the HTSG coupling, the maximum plant’s net desalinated water export rate decreases by a maximum of 0.233% only at the optimum operating parameters. Approximately 1.69 million kgs of waste landfilling can potentially be avoided daily from such coupling representing 25.5% of Kuwait’s total MSW production per day.

Simulation of a Downdraft Gasifier for Production of Syngas from Different Biomass Feedstocks

In the evaluation of gasification processes, estimating the composition of the fuel gas for different conditions is fundamental to identify the best operating conditions. In this way, modeling and simulation of gasification provide an analysis of the process performance, allowing for resource and time savings in pilot-scale process operation, as it predicts the behavior and analyzes the effects of different variables on the process. Thus, the focus of this work was the modeling and simulation of biomass gasification processes using the UniSim Design chemical process software, in order to satisfactorily reproduce the operation behavior of a downdraft gasifier. The study was performed for two residual biomasses (forest and agricultural) in order to predict the produced syngas composition. The reactors simulated gasification by minimizing the free energy of Gibbs. The main operating parameters considered were the equivalence ratio (ER), steam to biomass ratio (SBR), and gasification temperature (independent variables). In the simulations, a sensitivity analysis was carried out, where the effects of these parameters on the composition of syngas, flow of syngas, and heating value (dependent variables) were studied, in order to maximize these three variables in the process with the choice of the best parameters of operation. The model is able to predict the performance of the gasifier and it is qualified to analyze the behavior of the independent parameters in the gasification results. With a temperature between 850 and 950 °C, SBR up to 0.2, and ER between 0.3 and 0.5, the best operating conditions are obtained for maximizing the composition of the syngas in CO and H2.

Numerical analysis of hydrodynamics and thermochemical property of biomass gasification in a pilot-scale circulating fluidized bed

This study presents a three-dimensional reactive multiphase particle-in-cell (MP-PIC) model to simulate the hydrodynamics and thermochemical property of the biomass gasification process in a pilot-scale circulating fluidized bed gasifier. The bed hydrodynamics and thermochemical characteristics are investigated, together with discussing the effects of operating conditions on the species distribution, lower heating value (LHV), and combustible gas concentration (CGC). The results show that solid particles present oscillation behaviors for the time elapsed at the turbulent fluidization regime. Solid flux and rising velocity have peaks of about 249 kg/(m2·s) and 6.2 m/s in the core region of the bed, respectively. Increasing the gasification temperature reduces the CGC from 15.85% to 15.16%. However, only the concentration of H2 increases with the enlargement of the steam biomass ratio. Comparatively, the equivalence ratio (ER) has the most direct impact on gasification efficiency, and the increase of the ER adversely affects the LHV and CGC. The effect of particle diameter on the LHV, the magnitude of which can cover a range from 3.87% to 3.98%, is negligible compared with the other operational parameters, at least for the specific cases in the present investigation.

Steam gasification of hydrochar derived from hydrothermal carbonization of fruit wastes

This study presents a numerical investigation of steam gasification of hydrochar derived from fruit wastes. Four fruit wastes, apple chip pomace, grape pomace, rotten apple, and apple juice pomace, were used as feedstocks. Aspen Plus was used to simulate the gasification process. The syngas composition, hydrogen to CO ratio (H2/CO), CO to CO2 ratio (CO/CO2), and heating value (HHV) of the resulting syngas were analyzed. Results show that hydrothermal carbonization (HTC) increases the CO and reduces the CO2 content of the syngas after gasification. Accordingly, H2/CO reduces, and CO/CO2 increases after HTC treatment. Hydrothermal treatment also improves the HHV of the syngas. The obtained HHV of syngas from hydrochar gasification ranged from 10.1 to 15.3 MJ/Nm3 depending on the process parameters. Additionally, effects of process parameters were studied. Increasing the steam to biomass ratio (SBR) leads to a higher H2/CO, enriching the syngas with hydrogen (up to 64.7 vol%). Higher SBR also lowers the CO/CO2 ratio due to the consumption of CO and a rise in CO2. HHV increases with increasing pressure, and hydrochars exhibit more changes in HHV than raw feedstocks. The reaction temperature contributes to an increase in the fraction of CO in the syngas (up to 39.6 vol%). Although hydrogen increased initially with temperature, a slight reduction was observed for the gas at elevated temperatures, reducing the H2/CO ratio and increasing the CO/CO2 ratio.

Hydrogen production via biomass gasification: simulation and performance analysis under different gasifying agents

This study develops a new simulation model by ASPEN Plus for gasification integrated with water-gas shift reactors and product recovery unit for hydrogen production. Timber and wood waste (T&WW) as a lignocellulosic biomass was also considered as the input feedstock to the system. Then, the model is applied to investigate the effect of two agents of air and a mixture of air-steam under different operating conditions of temperature and steam to biomass ratio (SBR). The results reveal that the produced hydrogen through the air-steam gasification is at the highest points for all studied temperatures and it would be maximum (44.37 kmol/hr per 1 ton T&WWs) at 700 °C. The hydrogen production efficiency (HPE) can be also raised, stemming from the growth of H2. It values 39.2% at SBR = 0.1 that grows to 70% at SBR = 0.9. The optimum SBR lies between 0.7–0.8 that specific mass flow rate of hydrogen would be higher than 0.1 kghydrogen/kgT&WW.

Thermodynamic Analysis of Biomass Gasification Using Aspen Plus: Comparison of Stoichiometric and Non-Stoichiometric Models

The gasification process involves several reactions that occur simultaneously and are interrelated by several independent variables. Simulation tools can help us to understand the process behaviour and predict the efficiency and final composition of the products. In this work, two thermodynamic equilibrium models developed in Aspen Plus® software were assessed: a non-stoichiometric model based on the feedstock composition and on the most probable compounds expected from the results of the gasification process using minimisation of Gibbs free energy and a stoichiometric model based on a set of chemical reactions considered as the most relevant to describe the gasification process. Both models were validated with experimental data from a bubbling fluidised bed semi-pilot scale gasifier using pine kernel shells (PKS) as feedstock. The influence of temperature, stoichiometric ratio (SR) and steam to biomass ratio (SBR) were analysed. Overall, predictions of the gas composition and gasification efficiency parameters by the stoichiometric model showed better agreement to the experimental results. Our results point out the significance of an accurate description of the equilibrium composition of producer gas with the stoichiometric model for the gasification of biomass.

Experimental study on steam gasification of torrefied woodchips in a bubbling fluidized bed reactor

Biomass-based fuel is a potential renewable energy source despite its low energy density, high moisture content, and complex ash components due to its carbon-neutral nature. Torrefaction process, a promising biomass pretreatment method for upgrading biomass properties, is effective to generate fuel with higher calorific value and energy density. Torrefied biomass performs higher energy density and improved grindability characteristics as well as lower ratios of O/C and H/C compared to its raw source. This study presents an evaluation of the hydrogen production from steam gasification using torrefied woodchips as a feedstock in a pilot-scale bubbling fluidized bed reactor. The feedstock used is torrefied woodchips, which were treated at 250 °C in the N2 atmosphere. The experiments were conducted under isothermal and negative gauge pressure conditions in a pilot-scale bubbling fluidized bed reactor at different operating conditions such as gasification temperatures, steam-to-biomass ratio (SBR), and equivalence ratio (ER). Experimental results show that the high temperature and SBR are more favorable for hydrogen production and improve carbon conversion efficiency, while higher ER lowered content and yield of hydrogen. The optimal value of the steam-to-biomass ratio at 850 °C is 1.2 with the hydrogen content of 48.41% and the hydrogen yield of 0.039 Nm3/h.

Waste biomass to methanol–optimisation of gasification agent to feed ratio

Residues from agriculture and forest maintenance (lignocellulosic waste biomass) create a huge source of renewable energy and valuable materials. Gasification of this waste provides combustible gases consisting mainly of H2, CO and CO2, which can be used as syngas feed for methanol synthesis after treatment. Oxygen, steam or their mixtures can be used as gasifying agents in the biomass to methanol process. One of the most important parameters with crucial effect on gas composition and reactor temperature is the gasifying agent to feed mass flow ratio. In this work, gasification process of two samples of mixed agricultural waste, gas treatment and synthesis of methanol from the syngas produced was designed and simulated in the Aspen Plus environment. Three different cases were investigated: (1) only oxygen as gasifying agent, (2) oxygen and steam as gasifying agents without steam recycling and (3) oxygen and steam as gasifying agents with steam recycling. Samples of mixed agricultural waste consisted of corn leaves and stalks, wheat straw, barley straw, sunflowers and wood chips were characterised by proximate, ultimate and calorimetric analysis. Oxygen and steam flows were optimised to achieve maximum theoretical yield of methanol while maintaining the gasifier temperature, equal to, at least 900 °C. The best methanol to biomass ratio (MBR) of 0.43 was reached for a sample with lower moisture and ash content when both oxygen and steam were used as gasifying agents. The optimal oxygen to biomass ratio (OBR) was 0.57, and the steam to biomass ratio (SBR) was 0.89.