Evaluation of ultrasonication as a treatment strategy for enhancement of biohydrogen production from complex distillery wastewater and process optimization

Dark fermentation of distillery wastewater (DWW) gives a lower hydrogen yield (HY) and hydrogen production rate (R), owing to the complexity and a recalcitrant nature of effluent. Therefore, an effective pretreatment of DWW becomes imperative for the improvement of biohydrogen production. In the present study, the efficacy of ultrasonic pretreatment for enhancement of biohydrogen production from DWW was evaluated in batch test. Several variables, such as COD input, ultrasonic density (UD), and ultrasonication time (UT) were studied for optimization using response surface methodology integrated with desirability function. The highest HY, 10.95 mmol/g COD, and R, 6.67 mmol/L h, were obtained for batch test of ultrasonically pretreated DWW under optimal conditions for COD, UD and UT at 56 g/L, 0.12 W/mL, and 17 min, respectively. The significant relative enhancement of HY, 101%, and R, 103%, implies that ultrasonically treated DWW is about 1.2–1.4 times more effective for enhanced biohydrogen production from complex DWW compared to unsonicated DWW.     

生物质稻壳压缩成型过程建模及优化

在生物质压缩成型燃料的品质指标中,除燃烧特性外,松弛密度是成型燃料的一个重要性能指标,它直接决定了成型燃料的使用、运输要求和贮藏条件。文章以生物质稻壳为研究对象,考虑稻壳成型过程中含水率和成型温度对松弛密度的影响,依据最小二乘支持向量机建立了稻壳压缩成型过程模型,并进行了验证。在此基础上,建立了压缩成型过程的优化目标函数,旨在寻找成型燃料松弛密度最大时,含水率和成型温度两个控制量应满足的优化目标值。结果表明,该模型具有较好的拟合效果,可有效模拟稻壳压缩成型过程特性,且当稻壳含水率为6.631 4%,成型温度为140.991 5℃时,成型燃料松弛密度可达到最大值1.281 6 g/cm3。     

Nitrogen explosion pretreatment of lignocellulosic material for bioethanol production

A novel method for the pretreatment of lignocellulosic material is investigated in this work, using floodplain meadow hay as a feedstock for bioethanol production. Pressurized nitrogen (N₂) pretreatment is combined with explosive decompression to achieve high glucose yields with simple technology and low energy input. Results show that N₂ explosion yields hydrolysis efficiencies up to 71.8%. The highest hydrolysis efficiency was achieved at a temperature of 210°C with a cellulose to glucose conversion rate of 195.1 g kg^?1 of biomass.     

Selection of the best pretreatment for hydrogen and bioethanol production from olive oil waste products

Bioethanol is one of the most promising renewable energy sources, and it can be used as an alternative to petroleum-derived products. Agro-food residues are the substrates most frequently used for bioethanol production through anaerobic fermentation. The cultivation of olive trees and olive oil production are important economic activities throughout all Mediterranean countries. The wastes derived from olive oil production include a liquid waste, known as Olive Mill Wastewater (OMW), and a semi-solid waste, called Olive Pomace (OP), which is rich is lignin and cellulose materials. The aim of this work is to evaluate the quantity of hydrogen and bioethanol that could be extracted from an OMW-OP mixture after Saccharomyces cerevisiae anaerobic fermentation. In addition, different pretreatments (ultrasonic pretreatment, basic pretreatment, and calcium carbonate addition) have been tested to increase the glucose concentration and, consequently, the bioethanol and hydrogen production in the reaction medium and to decrease the content of inhibiting polyphenols which are mainly present in the OMW. All of the pretreatments were shown to have improved the hydrogen and bioethanol concentration at the end of the fermentation. The basic and ultrasonic pretreatments resulted in the best bioethanol and hydrogen production. These two pretreatments contributed to the hydrolysis of the lignin and cellulose and to increasing the soluble sugars (in particular glucose) content in the reaction mixture. Calcium carbonate addition decreased the polyphenol concentration; the polyphenols inhibit the fermentation mediated by S. cerevisiae.     

The used automobile catalytic converter as an efficient catalyst for removal of malathion through wet air oxidation process

The automobile catalytic converter (ACC) contains a huge number of precious metals as catalysts. When an ACC fails to meet standards, it is removed from the exhaust of an automobile but retains some catalytic activity. However, the recovery and/or activation of this waste is a high-cost process and includes several chemical treatments. Catalytic wet air oxidation (CWAO) has been reported as an effective wastewater treatment method. The most important disadvantage of CWAO is cost-nonefficiency. Herein, to overcome these problems, the simple recovery of catalysts from waste ACC for reuse in CWAO was investigated. The optimum conditions of reaction were investigated through response surface methodology (RSM). The optimum removal efficiency was 88% when the reaction conditions were set on the 20 bar of pressure at 111.5 °C over 77 min and using 0.41 g of recovered catalyst. In addition, toxicity testing was performed on a model of malathion-contaminated wastewater before and after CWAO treatment. Final product identification was performed which showed that CWAO eliminated the toxicity of wastewater and was determined to be malaoxon, present at acceptable concentrations, and tributyl phosphate. In conclusion, there may be important potential for the use of recovered ACC catalyst in the treatment of toxic wastewater.     

Process optimization for bioethanol production from cassava starch using novel eco-friendly enzymes

Although cassava (Manihot esculenta Crantz) is a potential bioethanol crop, high operational costs resulted in a negative energy balance in the earlier processes. The present study aimed at optimizing the bioethanol production from cassava starch using new enzymes like Spezyme^® Xtra and Stargen™ 001. The liquefying enzyme Spezyme was optimally active at 90 °C and pH 5.5 on a 10% (w/v) starch slurry at levels of 20.0 mg (280 Amylase Activity Units) for 30 min. Stargen levels of 100 mg (45.6 Granular Starch Hydrolyzing Units) were sufficient to almost completely hydrolyze 10% (w/v) starch at room temperature (30 ± 1 °C). Ethanol yield and fermentation efficiency were very high (533 g/kg and 94.0% respectively) in the Stargen + yeast process with 10% (w/v) starch for 48 h. Raising Spezyme and Stargen levels to 560 AAU and 91.2 GSHU respectively for a two step loading [initial 20% (w/v) followed by 20% starch after Spezyme thinning]/initial higher loading of starch (40% w/v) resulted in poor fermentation efficiency. Upscaling experiments using 1.0 kg starch showed that Stargen to starch ratio of 1:100 (w/w) could yield around 558 g ethanol/kg starch, with a high fermentation efficiency of 98.4%. The study showed that Spezyme level beyond 20.0 mg for a 10% (w/v) starch slurry was not critical for optimizing bioethanol yield from cassava starch, although an initial thinning of starch for 30 min by Spezyme facilitated rapid saccharification-fermentation by Stargen + yeast system. The specific advantage of the new process was that the reaction could be completed within 48.5 h at 30 ± 1 °C.     

Acidified glycerol pretreatment for enhanced ethanol production from rice straw

Rice straw was pretreated using an industrial grade glycerol for ethanol production. The pretreatment was conducted at 130–210 °C for 1–24 h with 5% solid loading. The glucan content in the regenerated rice straw increased with increasing pretreatment temperature and time. The production of fermentable sugars initially increased as the pretreatment temperature and reaction time increased, but then decreased somewhat at the higher temperatures and with longer reaction duration. The highest amount of reducing sugar produced by the enzymatic hydrolysis was achieved at 190 °C for 10 h with 5% solid loading, optimal condition for the glycerol pretreatment of rice straw. Furthermore, it was observed that glycerol pretreatment with the addition of HCl improved the digestibility of fermentable sugars by 4–5 times that of untreated samples. Fermentation of hydrolysates resulted in an ethanol yield of 0.44 g/g sugar, corresponding to a theoretical yield of 84.3%. It was concluded that acidified glycerol is one of the good candidates of the organic solvent for the pretreatment of lignocellulosic biomass.     

Impact of dilute acid pretreatment on the structure of bagasse for bioethanol production

Dilute acid pretreatment is a commonly used pretreatment method in the course of producing bioethanol from lignocellulosics and the structure variation of the lignocellulosics is highly related to the pretreatment process. To understand the impact of dilute acid pretreatment on the structure of bagasse, four different pretreatment conditions by varying heating time are considered where the bagasse and the pretreated materials are examined using a variety of analysis methods. The obtained results indicate that the thermogravimetric analysis (TGA) is able to provide a useful insight into the recognition of lignocellulosic structure. Specifically, the peak of the TGA of the pretreated materials moves toward the low temperature region, revealing that the lignocellulosic structure is loosened. However, the characteristic of crystal structure of cellulose remains in the pretreated materials. Increasing heating time enhances the pretreatment procedure; as a result, the average particle size of the investigated materials increases with heating time. This swelling behavior may be attributed to the enlarged holes inside the particles in that the surface area decreases with increasing heating time. In addition, when the heating time is increased to a certain extent (e.g. 15 min), some fragments are found at the surface and they tend to peel off from the surface. It follows that the dilute acid pretreatments have a significant effect on the bagasse structure. Copyright © 2009 John Wiley & Sons, Ltd.     

Organosolv pretreatment of Liriodendron tulipifera and simultaneous saccharification and fermentation for bioethanol production

An acid-free organosolv process was proposed to overcome the problems caused by acid catalyst in organosolv process, thereby producing ethanol from Liriodendron tulipifera effectively. Although relative lignin contents were above 20%, enzymatic conversion increased significantly to 65% at all conditions, and thus correlation between lignin and enzymatic conversion could not be explained using relative lignin content. Enzymatic conversion increased significantly above 65% regardless of temperature, which suggests the organosolv pretreatment with sodium hydroxide can be performed at lower temperature. FE-SEM showed that the process made the structure loose and broke down biomass through lignin dissolution. Wrinkle formation by alkaline swelling was also observed and it might increase surface area. Although pore-volume increased slightly, it was not the sole key factor for the organosolv pretreatment with sodium hydroxide. Increase in surface area and enzyme adsorption enhanced the enzymatic hydrolysis. Ethanol of 96% could be produced theoretically and it suggested that the acid-free organosolv process was an effective pretreatment method for bioethanol production from L. tulipifera.     

Net energy analysis of bioethanol production system from high-yield rice plant in Japan

This study analyzes the energy balance of a bioethanol production system from high-yield rice plant in Japan. Two systems are considered in which rice is converted to ethanol: one in which cellulose feedstocks, straw and husk, are used for cogeneration (scenario 1), and the other in which they are converted to ethanol, and byproducts such as lignin and unreacted holocellulose are used for cogeneration (scenario 2). Energy input in the agricultural process including transportation is estimated to be 52.3 GJ/ha from an Input Output Table. The heating values of produced rice and cellulose feedstocks are 120.7 GJ/ha and 162.3 GJ/ha, respectively. The net energy balance (NEB) of scenario 1 is 129.2 GJ/ha, which produces 3.6 kL/ha of ethanol and 9420 kWh/ha of external electricity. On the other hand, NEB of scenario 1 is 11.7 GJ/ha, which produces 7.1 kL/ha of ethanol. Both NEBs are positive, but NEB of scenario 2 is much higher than that of scenario 1. An acid hydrolysis technology of cellulosic biomass applied to scenario 2 needs a large amount of heat energy for sulfuric acid recovery. If an enzyme hydrolysis of cellulosic biomass is developed, there is a possibility of improving NEB of scenario 2.     

Fractional characterization of a bio-oil derived from rice husk

Bio-oils usually contain many types of compounds with various chemical properties. A bio-oil sample derived from rice husk through rapid pyrolysis was fractioned using solvent- or solid-extraction techniques based on their various properties. Ultraviolet-visible spectroscopy, three-dimensional excitation-emission matrix (EEM) fluorescence spectroscopy and Fourier transform infrared spectroscopy were used to characterize their various spectral properties for further understanding the characteristics of the bio-oil. Bio-oil mostly contains many aromatic ring components, acidic polar fractions, few weak- and non-polar components. The results all show that the main compounds and functional groups in the various bio-oil fractions were different and depended on the fractionation methods. The compositions of the bio-oil fractions were also analyzed with a gas chromatography/mass spectrometry (GC/MS) method. The consistency of the results obtained from the spectrometric methods with the GC/MS method indicates that the spectrometric methods have a good potential for rapid and effective characterization of bio-oils.     

Effect of bacterial amylase pretreatment on bioethanol production from starch-based solid waste (SBSW)

Fuels derived from biomass are essential in order to overcome the excessive dependence on petroleum. They also minimize the emissions of greenhouse gases. Pretreatment in biofuel production is a very important step. Pretreatment is not only costly in its own right but also has a pervasive impact on the cost of virtually all other processing operations. The present study investigates the effect of bacterial amylase pretreatment on ethanol production from different kinds of starch-based solid waste (SBSW). For this purpose four amylase-producing bacterial isolates were obtained from samples collected from municipal waste dumping sites. The isolated bacteria were then used for the pretreatment of SBSW for ethanol production. After bacterial amylase pretreatment, 13% yield of ethanol was obtained.     

Characterization,pretreatment and saccharification of spent seaweed biomass for bioethanol production using baker's yeast

Seaweeds are marine macroalgae found abundantly and viewed as potential source of phycocolloids to produce biofuel. In this study, seaweed spent biomass obtained from alginate production industry and biomass obtained after pigment extraction were found to contain a considerable amount of phycocolloids. These two spent biomasses were investigated for the production of ethanol. In this study, the red seaweed spent biomass of Gracilaria corticata var corticata showed higher content of polysaccharide (190.71 ± 30.67 mg g⁻¹ dry weight) than brown seaweed spent biomass (industrial) (136.28 ± 30.09 mg g⁻¹ dry weight). Hydrolysis of spent biomasses with different concentrations of sulfuric acid (0.1%, 0.5% and 1%) was also investigated. Brown seaweed spent biomass and red seaweed spent biomass exhibited high amount of sugar in 0.5% and 1% sulfuric acid treatment, respectively. Proximate and ultimate composition of seaweed spent biomasses were analysed for energy value. The FT-Raman spectra exhibited similar stretches for both acid hydrolysed spent biomasses with their respective standards. Ethanol produced through a fermentation process using spent hydrolysates with baker's yeast at pH 5.3 was found to be significant. The ethanol yield from brown seaweed spent biomass and red seaweed spent biomass was observed to be 0.011 g g⁻¹ and 0.02 ± 0.003 g g⁻¹ respectively, when compared with YPD (0.42 ± 0.03 g g⁻¹) and d-galactose (0.37 ± 0.04 g g⁻¹) as standard on day 4. The present study revealed the possibility of effective utilization of spent biomass from seaweed industry for ethanol production.     

Comparisons of the hydrogen-rich syngas compositions from wet rice husk slurry steam reforming reactions using different catalysts

Rice husk slurry is pumped into a packed reactor and the products from the steam reforming reactions using different catalysts are studied. The steam/biomass weight ratio of such a system is between 3.47 and 5.25. The solids, liquid and gaseous products are a mass fraction of 2.8-4.1%, a mass fraction of 92.4-93.0% and a mass fraction of 3.5-4.7%, respectively. The hydrogen concentration in the gaseous product is approximate a volume fraction of 41% using the Al₂O₃ catalyst of a CuO mass fraction of 13%, a volume fraction of 38% using the Al₂O₃ catalyst of a Ni mass fraction of 13%, a volume fraction of 31% using the Al₂O₃ catalyst of a ZnO mass fraction of 13%, and a volume fraction of 20% using the Al₂O₃ catalyst at the reactor temperature of 800 °C. In the reactor temperature range studied (350-800 °C), the hydrogen concentration in the product stream increases monotonically with the increasing of the reactor temperature and the steam/carbon molar ratio. The value of dry gas LHV is between 9.4 MJ m⁻³ and 12 MJ m⁻³ at the reaction temperature of 600-800 °C. Considering the simple catalyst used in current study, the syngas of a hydrogen volume fraction of approximate 40% is obtained by pumping the biomass slurry to carry out the catalytic steam reforming reaction.     

Optimization of acidic hydrolysis conditions of rice husk for fermentable sugar production

Lignocellulosic biomass (LSB) is the most abundantly available renewable source in the world. Rice husk (RH) is also one of the LSB. In this study, the optimization of dilute acid hydrolysis conditions of RH by using one-factor-at-a-time method was performed. The optimum hydrolysis conditions of RH were determined as 131.04°C, 1:10.28 (w/v) of solid:liquid ratio, 1.47% (w/v) of acid ratio and 24.05 min, which yielded as 25.52 g/L of fermentable sugar concentration. Furthermore, the chemical composition of hydrolysate was also examined and the levels of phenolics, 5-hydroxymethylfurfural (HMF), acetate, glucose, and fructose+xylose were found as 0.89, 0, 3.27, 2.10, and 13.80 g/L, respectively. Accordingly, RH can be utilized as a favorable feedstock for the production of value-added products.     

Carob pod as a feedstock for the production of bioethanol in Mediterranean areas

There is a growing interest worldwide to find out new and cheap carbohydrate sources for production of bioethanol. In this context, carob pod (Ceratonia siliqua) is proposed as an economical source for bioethanol production, especially, in arid regions. The carob tree is an evergreen shrub native to the Mediterranean region, cultivated for its edible seed pods and it is currently being reemphasised as an alternative in dryland areas, because no carbon-enriched lands are necessary. In this work, the global process of ethanol production from carob pod was studied. In a first stage, aqueous extraction of sugars from the pod was conducted, achieving very high yields (>99%) in a short period of time. The process was followed by acid or alkaline hydrolysis of washed pod at different operating conditions, the best results (R = 38.20%) being reached with sulphuric acid (2% v/v) at 90 °C, using a L/S (liquid/solid) ratio of 7.5 and shaking at 700 rpm for 420 min. After that, fermentation of hydrolysates were tested at 30 °C, 125 rpm, 200 g/L of sugars and 15 g/L of yeast with three different kinds of yeasts. In these conditions a maximum of 95 g/L of ethanol was obtained after 24 h. Finally, the distillation and dehydration of water–bioethanol mixtures was analyzed using the chemical process simulation software CHEMCAD with the aim of estimate the energy requirements of the process.     

Application of Nagchampa biodiesel and rice husk gas as fuel

This paper elaborates the application of Nagchampa biodiesel and rice husk producer gas in dual mode using rice husk producer gas. Nagchampa biodiesel was examined under both single and dual fuel mode having a persistent gas flow rate of 21.69 kg/h at discrete loads. The test results disclosed that the engine shows improved performance and emission characteristics at optimum load of 8 kW. There is a decrease in NO_x, smoke opacity, and performance, while HC, CO, and CO₂ increase moderately with respect to gas flow rate. It can finally be concluded that biodiesel exhibits lower performance and improved emission than that of neat diesel.     

Influence of impregnation with lactic acid on sugar yields from steam pretreatment of sugarcane bagasse and spruce, for bioethanol production

Lignocellulosic biomass can be utilized to produce ethanol, a promising alternative energy source produced through fermentation of sugars. However, in order to achieve high sugar and ethanol yields, the lignocellulosic material must be pretreated before the enzymatic hydrolysis and fermentation. Dilute acid pretreatment, using SO₂, is one of the most promising methods of pretreatment for softwood and agricultural residues. However, handling the high acidity of the slurry obtained from pretreatment and difficulty in recycling/degradation of the impregnating agent are some of the drawbacks of the dilute acid processes. In the present study the influence of utilization of a weak organic acid (lactic acid), as impregnating agent, on the sugar yield from pretreatment, with and without addition of SO₂, was investigated. The efficiency of pretreatment was assessed by enzymatic hydrolysis of the slurry obtained by pretreatment, using sugarcane bagasse and spruce, stored for one and two months in the presence of lactic acid separately, as feedstocks. Pretreatment of bagasse after storage with 0.5% lactic acid resulted in an overall glucose yield, i.e. after enzymatic hydrolysis, of 79% of theoretical based on the amount available in the raw material. This was as good as pretreatment using SO₂ as impregnating agent. However, storage of spruce with lactic acid before pretreatment, with and without addition of SO₂, was not efficient and resulted in lower sugar yields than pretreatment using SO₂ only.     

The effect of biomass feeding location on rice husk gasification for hydrogen production

The objective of this study is to investigate the impact of biomass feeding location on rice husk gasification for hydrogen production. By comparing the results between top-feed and bottom-feed of the feedstock of the fluidized bed biomass gasification at the reaction temperature between 600～1000 °C and ER = 0.2, 0.27, and 0.33 without steam, the optimum low heating value was increase by 2.35 kJ/g-rice husk by the top-feed to gasifier. Although the yield of hydrogen was decreased by 42% for the rice husk gasification by the top-feed operation, the yield of CO, CO2, and CH4 were highly increased, which enhancing the heating value of the effluent gas. The study results suggested the potential route of the biomass gasification at the different feeding location.