Integrated catalytic adsorption (ICA) steam gasification system for enhanced hydrogen production using palm kernel shell

This paper investigates the integrated catalytic adsorption (ICA) steam gasification of palm kernel shell for hydrogen rich gas production using pilot scale fluidized bed gasifier under atmospheric condition. The effect of temperature (600–750 °C) and steam to biomass ratio (1.5–2.5 wt/wt) on hydrogen (H₂) yield, product gas composition, gas yield, char yield, gasification and carbon conversion efficiency, and lower heating values are studied. The results show that H₂ hydrogen composition of 82.11 vol% is achieved at temperature of 675 °C, and negligible carbon dioxide (CO₂) composition is observed at 600 °C and 675 °C at a constant steam to biomass ratio of 2.0 wt/wt. In addition, maximum H₂ yield of 150 g/kg biomass is observed at 750 °C and at steam to biomass ratio of 2.0 wt/wt. A good heating value of product gas which is 14.37 MJ/Nm³ is obtained at 600 °C and steam to biomass ratio of 2.0 wt/wt. Temperature and steam to biomass ratio both enhanced H₂ yield but temperature is the most influential factor. Utilization of adsorbent and catalyst produced higher H₂ composition, yield and gas heating values as demonstrated by biomass catalytic steam gasification and steam gasification with in situ CO₂ adsorbent.     

Potential of hydrogen from oil palm biomass as a source of renewable energy worldwide

Various catastrophes related to extreme weather events such as floods, hurricanes, droughts and heat waves occurring on the Earth in the recent times are definitely a clear warning sign from nature questioning our ability to protect the environment and ultimately the Earth itself. Progressive release of greenhouse gases (GHG) such as CO₂ and CH₄ from development of various energy-intensive industries has ultimately caused human civilization to pay its debt. Realizing the urgency of reducing emissions and yet simultaneously catering to needs of industries, researches and scientists conclude that renewable energy is the perfect candidate to fulfill both parties requirement. Renewable energy provides an effective option for the provision of energy services from the technical point of view. In this context, biomass appears as one important renewable source of energy. Biomass has been a major source of energy in the world until before industrialization when fossil fuels become dominant and researches have proven from time to time its viability for large-scale production. Although there has been some successful industrial-scale production of renewable energy from biomass, generally this industry still faces a lot of challenges including the availability of economically viable technology, sophisticated and sustainable natural resources management, and proper market strategies under competitive energy markets. Amidst these challenges, the development and implementation of suitable policies by the local policy-makers is still the single and most important factor that can determine a successful utilization of renewable energy in a particular country. Ultimately, the race to the end line must begin with the proof of biomass ability to sustain in a long run as a sustainable and reliable source of renewable energy. Thus, the aim of this paper is to present the potential availability of oil palm biomass that can be converted to hydrogen (leading candidate positioned as the energy of the millennium) through gasification reaction in supercritical water, as a source of renewable energy to policy-makers. Oil palm topped the ranking as number 1 fruit crops in terms of production for the year 2007 with 36.90 million tonnes produced or 35.90% of the total edible oil in the world. Its potentiality is further enhanced by the fact that oil constitutes only about 10% of the palm production, while the rest 90% is biomass. With a world oil palm biomass production annually of about 184.6 million tons, the maximum theoretical yield of hydrogen potentially produced by oil palm biomass via this method is 2.16×10¹⁰ kg H₂ year⁻¹ with an energy content of 2.59 EJ year⁻¹, meeting almost 50% of the current worldwide hydrogen demand.     

Characterization of paper mill sludge as a renewable feedstock for sustainable hydrogen and biofuels production

Paper and pulp mills generate substantial quantities of cellulose-rich sludge materials that are disposed in landfills at a large scale. For sustainability purposes, sludge materials can be bioprocessed to produce renewable fuels and useful chemicals. The enzymatic hydrolysis of cellulose is the process bottleneck that affects the conversion economics directly by using zero-cost raw materials. In order to study and optimize the process, the characteristics of the sludge raw materials should be first evaluated. In this work, sludge samples were obtained from paper mills located at different locations in Wisconsin and Minnesota. Part of the sludge samples was washed (de-ashed) with hydrochloric acid while the other part remained unwashed. The samples were subjected to multiple spectroscopic analyses techniques to evaluate the morphological properties of cellulose fibers and to estimate the total structural carbohydrate content. The results showed that the de-ashing process changed some fiber characteristics and cellulose crystallinity structure in all sludge samples. Sludge sample A (obtained from Kraft pulp and recycled paper mill region) showed a high percentage of fiber, with crystalline cellulose, compared to the other two sludge samples suggesting that sludge A is a valuable source to make value-added products. Aspen Plus mass and energy calculations performed in view of the ‘zero’ cost and the reliable supply of sludge raw materials producing 2 mol H₂/mol glucose. Moreover, the results showed that extracting crystalline cellulose from these sludge samples is more profitable than crystalline cellulose made from the other lignocellulosic feedstocks. The results reported here showed that the utilization of these sludge materials would be an economically attractive and promising alternative for the production of hydrogen.     

Kinetics of cotton cellulose hydrolysis using concentrated acid and fermentative hydrogen production from hydrolysate

The kinetics of cotton cellulose hydrolysis using concentrated sulfuric acid and the performance of fermentative hydrogen production from the hydrolysate in the batch system was carried out in this study. Effects of sulfuric acid concentrations, cotton cellulose concentrations and operating temperatures on the cotton cellulose hydrolysis were investigated. It was found that cotton cellulose can dissolve completely in sulfuric acid concentration above 55% (by volume) at room temperature. The reduced sugar yields were varied from 64.3 to 73.9% (g R-sugar/g cotton cellulose) with the initial cotton cellulose concentrations of 30-70 g/L at a temperature of 40 °C.The reduced sugar concentrations and the initial pH of biohydrogen production were investigated at 37 °C. It was found that the optimal values of the hydrogen yield and substrate utilization were 0.95 mol H₂/mol R-sugar and 98% with an initial pH of 8.2, when substrate concentration was fixed at 20 g R-sugar/L. The maximum hydrogen yield was 0.99 mol H₂/mol R-sugar at a substrate concentration of 15 g R-sugar/L. Using the Gompertz Equation Model simulation, the maximum hydrogen production rate was 253 mL H₂/h/L at a substrate of 30 g/L and initial pH of 8.4.     

Cladophora sp. as a sustainable feedstock for dark fermentative biohydrogen production

Macroalgae are rich in carbohydrates which can be used as a promising substrate for fermentative biohydrogen production. In this study, Cladophora sp. biomass was fermented for biohydrogen production at various inoculum/substrate (I/S) ratios against a control of inoculum without substrate in laboratory-scale batch reactors. The biohydrogen production yield ranged from 40.8 to 54.7 ml H₂/g-VS, with the I/S ratio ranging from 0.0625 to 4. The results indicated that low I/S ratios caused the overloaded accumulation of metabolic products and a significant pH decrease, which negatively affected hydrogen production bacteria's metabolic activity, thus leading to the decrease of hydrogen fermentation efficiency. The overall results demonstrated that Cladophora sp. biomass is an efficient fermentation feedstock for biohydrogen production.     

Effects of N/C,P/C and Fe/C ratios on dark fermentative hydrogen gas production from waste paper towel hydrolysate

The effects of N/C, P/C and Fe/C ratios on dark fermentative hydrogen gas production from activated carbon treated WPT hydrolysate were investigated using Box–Behnken statistical experiment design. N/C, P/C and Fe/C ratios were chosen as independent variables while the H₂ yield and SHPR were set as the objective functions. H₂ yield and SHPR functions were described by two quadratic model functions. The addition of a proper amount of N, P and Fe to the fermentation media was found to be essential to enhance the H₂ production performance. Linear and interaction terms of N/C and Fe/C did have a significant effect on the H₂ yield in the model function. However, the SHPR was significantly affected by the linear and interaction terms of N/C and P/C. The most convenient N/C, P/C and Fe/C ratios resulting maximum H₂ yield (0.656 mol H₂/mol glucose) and SHPR (241.64 mL H₂/g biomass.h) were determined as 0.05, 0.09 and 0.003 (w/w), respectively.     

Pretreatment enhanced structural disruption,enzymatic hydrolysis,fermentative hydrogen production from rice straw

Rice straw (RS) is one of the major lignocellulosic wastes in the world and an abundant feedstock for producing biofuels and chemicals. However, RS is difficult to decompose. In this study, NaOH/urea and electrohydrolysis pretreated RS were used to enhance the structural disruption, enzymatic hydrolysis, and fermentative hydrogen production. Scanning electron microscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy analyses demonstrated that both NaOH/urea and electrohydrolysis pretreatments could effectively disrupt the lignin structure and increase the cellulose crystallinity of RS. Following pretreatment, RS was hydrolyzed by cellulase. After 96 h of enzymatic hydrolysis, NaOH/urea- and electrohydrolysis-pretreated RS produced 3.2- and 1.7-fold higher total reducing sugars than the unpretreated RS (232.95 ± 3.60 mg/g), respectively. Finally, the obtained RS hydrolysates were used for fermentative hydrogen production. NaOH/urea- and electrohydrolysis-pretreatment hydrolysates produced 125.0 and 163.0 mL H₂/g RS, respectively, which is much higher than the hydrogen yield of unpretreated hydrolysates.     

Challenges for renewable hydrogen production from biomass

The increasing demand for H₂ for heavy oil upgrading, desulfurization and upgrading of conventional petroleum, and for production of ammonium, in addition to the projected demand for H₂ as a transportation fuel and portable power, will require H₂ production on a massive scale. Increased production of H₂ by current technologies will consume greater amounts of conventional hydrocarbons (primarily natural gas), which in turn will generate greater greenhouse gas emissions. Production of H₂ from renewable sources derived from agricultural or other waste streams offers the possibility to contribute to the production capacity with lower or no net greenhouse gas emissions (without carbon sequestration technologies), increasing the flexibility and improving the economics of distributed and semi-centralized reforming. Electrolysis, thermocatalytic, and biological production can be easily adapted to on-site decentralized production of H₂, circumventing the need to establish a large and costly distribution infrastructure. Each of these H₂ production technologies, however, faces technical challenges, including conversion efficiencies, feedstock type, and the need to safely integrate H₂ production systems with H₂ purification and storage technologies.     

Fermentative hydrogen production from indigenous mesophilic strain Bacillus anthracis PUNAJAN 1 newly isolated from palm oil mill effluent

In the present study, a new mesophilic bacterial strain, identified as Bacillus anthracis strain PUNAJAN 1 was isolated from palm oil mill effluent (POME) sludge, and tested for its hydrogen production ability. Effect of physico-chemical factors such as temperature, initial pH, nitrogen source and carbon sources were investigated in order to determine the optimal conditions for hydrogen production. The maximum hydrogen yield of 2.42 mol H₂/mol mannose was obtained at 35 °C and initial pH of 6.5. Yeast and mannose were used as the main carbon and nitrogen sources respectively in the course of the hydrogen production. Apart from synthetic substrate, specific hydrogen production potentials of the strain using POME was calculated and found to be 236 ml H₂/g chemical oxygen demand (COD). The findings of this study demonstrate that the indigenous strain PUNAJAN 1 could be a potential candidate for hydrogen using POME as substrate.     

Deoiled algal cake as feedstock for dark fermentative biohydrogen production: An integrated biorefinery approach

An integrated biorefinery approach utilizing deoiled algal cake (after lipid extraction) as potential feed-stock for biohydrogen (H₂) production using selectively enriched acidogenic consortia as biocatalyst was evaluated. Algae pretreated extract (AP-E) documented maximum H₂ production rate (HPR), cumulative H₂ production (CHP) and specific H₂ yield (SHY) with higher substrate degradation (65%) in terms of COD removal efficiency than other conditions, which is a good sign for waste remediation. Along with the biohydrogen production and substrate removal the consortia also produced good amount of volatile fatty acids (VFA). VFA production in fermentation media resulted in reactor pH drop. The study depicted the feasible use of deoiled algal biomass as feed-stock for H₂ production in the framework of biorefinery.     

Potential of renewable hydrogen production for energy supply in Hong Kong

Hong Kong is highly vulnerable to energy and economic security due to the heavy dependence on imported fossil fuels. The combustion of fossil fuels also causes serious environmental pollution. Therefore, it is important to explore the opportunities for clean renewable energy for long-term energy supply. Hong Kong has the potential to develop clean renewable hydrogen energy to improve the environmental performance. This paper reviews the recent development of hydrogen production technologies, followed by an overview of the renewable energy sources and a discussion about potential applications for renewable hydrogen production in Hong Kong. The results show that although renewable energy resources cannot entirely satisfy the energy demand in Hong Kong, solar energy, wind power, and biomass are available renewable sources for significant hydrogen production. A system consisting of wind turbines and photovoltaic (PV) panels coupled with electrolyzers is a promising design to produce hydrogen. Biomass, especially organic waste, offers an economical, environmental-friendly way for renewable hydrogen production. The achievable hydrogen energy output would be as much as 40% of the total energy consumption in transportation.     

Constructing a new business model for fermentative hydrogen production from wastewater treatment

The development of hydrogen energy as a sustainable energy resource is essential for mitigating climate change. The primary challenge to the commercialization of hydrogen energy, relative to that of petrochemical fuels, is cost. Therefore, an innovative business model that converts the costs of procuring biomass into revenue via the production of hydrogen was developed. Profitable hydrogen production can typically be realized by lowering costs through continuous technological development and increasing scale. Feedstock procurement costs, however, limit the cost/benefit reduction flexibility. This study employs biowaste material as feedstock for biological fermentative hydrogen production. This model extends the hydrogen production value chain to include the income from biomass hydrogen production as well as the revenue from processing biowaste and reduced fuel source costs. This study investigates the costs involved in the commercialization of the hydrogen fermentation process, develops an innovative business model, and presents a case study to describe this model.     

Optimal experimental conditions for hydrogen production using low voltage electrooxidation of organic wastewater feedstock

The dependence of electrooxidation on experimental conditions of organic molecules was investigated to optimize the production of hydrogen from potential wastewater sources using low voltage sources (∼1 V dc). Electrooxidation on platinum, gold, and stainless steel anodes with hydrogen production on the cathode was investigated using several different organic reductants, including: methanol, ethanol, glycerol, isopropanol, propanal, glycerol, glucose, sucrose, citric acid, and propionic acid. The electrolyte pH was varied from 2 to 12 in a 1 M Na₂SO₄ supporting solution. At 1 V, glycerol, citric acid, ethanol and methanol were found to yield the highest currents at low pH values (pH 2 and 7) on platinum electrode, glucose on gold electrode at pH 12 in 1 M Na₂SO₄ solution produced the highest total current density at 1 V with measured Faradaic efficiency for 1 M glucose of 70%. The hydrogen energy production efficiency was 86%. Practical limitations of glucose oxidation at optimum experimental conditions are discussed.     

Optimization of fermentative hydrogen production process by response surface methodology

The effect of temperature, initial pH and glucose concentration on fermentative hydrogen production by mixed cultures was investigated in batch tests, and the optimization of fermentative hydrogen production process was conducted by response surface methodology with a central composite design. Experimental results showed that temperatures, initial pH and glucose concentrations had impact on fermentative hydrogen production individually and interactively. The maximum hydrogen yield of 289.8 mL/g glucose was estimated at the temperature of 38.6 °C, the initial pH of 7.2 and the glucose concentration of 23.9 g/L. The maximum hydrogen production rate of 28.2 mL/h was estimated at the temperature of 37.8 °C, the initial pH of 7.2 and the glucose concentration of 27.6 g/L. The maximum substrate degradation efficiency of 96.9% was estimated at the temperature of 39.3 °C, the initial pH of 7.0 and the glucose concentration of 26.8 g/L. Response surface methodology was a better method to optimize the fermentative hydrogen production process. Modified logistic model could describe the progress of cumulative hydrogen production in the batch tests of this study successfully.     

Silage as source of bacteria and electrons for dark fermentative hydrogen production

In this study, grass silage was used both as a source of bacteria and as a substrate for dark fermentative hydrogen production. Silage is produced by lactic acid fermentation controlled by end point pH (<4.0). In this study, the fermentation of silage was successfully continued and directed to hydrogen production by neutralizing the pH. Highest hydrogen yield of 37.8 ± 5.8 mL H₂/g silage was obtained at 25 g/L of silage. The main soluble metabolites were acetate and butyrate with the final concentrations of 1.5 ± 0.2 and 0.5 ± 0.0 g/L, respectively. Bacteria present (at 25 g silage/L) included Ruminobacillus xylanolyticum, Acetanaerobacterium elongatum and Clostridium populeti and were involved in silage fermentation to hydrogen. In summary, this work demonstrates that grass silage becomes amenable to hydrogen fermentation by indigenous silage bacteria through pH neutralization.     

Utilization of excess corn kernels for hydrogen gas biofuel production

Corn kernels are good candidates for production of various value-added products such as gas biofuel, hydrogen due to the carbohydrate-rich composition. In this study, widely grown corn, field corn kernels were dissolved in subcritical water at different temperatures to determine optimal thermal hydrolysis condition. Organic-rich hydrolysate obtained from hydrolysis process was gasified by aqueous-phase reforming (APR) for hydrogen gas production.Since hydrolysis at 200 °C resulted in significantly more total organic carbon release than other temperatures and the lowest amount of insolubilized solid residue. Different concentrations of this hydrolysate (diluted with water at different ratios) were evaluated for high yielding hydrogen gas production. Gasification performance of corn kernels was also compared with lignocellulosic biomass using corn stover as a representative biomass material.The hydrolysate with 2486 mg/L TOC concentration showed the best performance for hydrogen gas production (130 mL H₂/g corn) and left less amount of ungasified solid residue. Corn kernels produced 2.3 times more hydrogen gas compared to corn stover biomass. Thus, corn kernels are promising feed materials for APR process, and excess production of corn can be utilized for hydrogen gas production in higher yield and richer composition.     

An analysis of hydrogen production from renewable electricity sources

Three aspects of producing hydrogen via renewable electricity sources are analyzed to determine the potential for solar and wind hydrogen production pathways: a renewable hydrogen resource assessment, a cost analysis of hydrogen production via electrolysis, and the annual energy requirements of producing hydrogen for refueling. The results indicate that ample resources exist to produce transportation fuel from wind and solar power. However, hydrogen prices are highly dependent on electricity prices. For renewables to produce hydrogen at $2 kg⁻¹, using electrolyzers available in 2004, electricity prices would have to be less than $0.01 kWh⁻¹. Additionally, energy requirements for hydrogen refueling stations are in excess of 20 GWh/year. It may be challenging for dedicated renewable systems at the filling station to meet such requirements. Therefore, while plentiful resources exist to provide clean electricity for the production of hydrogen for transportation fuel, challenges remain to identify optimum economic and technical configurations to provide renewable energy to distributed hydrogen refueling stations.     

添加垃圾渗滤液对厨余垃圾厌氧发酵产氢的影响

以厨余垃圾和垃圾渗滤液为原料,考察了垃圾渗滤液的不同添加量对厌氧消化稳定性及产氢气性能的影响。结果表明,在厨余垃圾中添加少量的垃圾渗滤液能缩短厌氧消化的延滞期而不影响其消化及产气性能,垃圾渗滤液浓度越高则越容易形成氨抑制,严重影响厌氧消化作用的进行。在40 g厨余原料中添加100 g垃圾渗滤液,其厌氧消化延滞期为6 h,氢气含量稳定在50%,最大产氢气速率为4.8 mL/(h.g),最终氢气产量为48.37 mL/g;添加200~500 g垃圾渗滤液均形成氨抑制,严重影响产气性能,产气速率均低于2.5 mL/(h.g),最终产气量为16~30 mL/g。     

Optimization of dilute acid and enzymatic hydrolysis for dark fermentative hydrogen production from the empty fruit bunch of oil palm

Pretreatment of the empty fruit brunch (EFB) from oil palm was investigated for H₂ fermentation. The EFB was hydrolyzed at various temperatures, H₂SO₄ concentrations, and reaction times. Subsequently, the acid-hydrolysate underwent enzymatic saccharification under various temperature, pH, and enzymatic loading conditions. Response surface methodology derived the optimum sugar concentration (SC), hydrogen production rate (HPR), and hydrogen yield (HY) as 28.30 g L⁻¹, 2601.24 mL H₂ L⁻¹d⁻¹, and 275.75 mL H₂ g⁻¹ total sugar (TS), respectively, at 120 °C, 60 min of reaction, and 6 vol% H₂SO₄, with the combined severity factor of 1.75. Enzymatic hydrolysis enhanced the SC, HY, and HPR to 34.52 g L⁻¹, 283.91 mL H₂ g⁻¹ TS, and 3266.86 mL H₂ L⁻¹d⁻¹, respectively, at 45 °C, pH 5.0, and 1.17 mg enzyme mL⁻¹. Dilute acid hydrolysis would be a viable pretreatment for biohydrogen production from EFB. Subsequent enzymatic hydrolysis can be performed if enhanced HPR is required.