Sodium Hydroxide Pretreatment Research Articles

Anaerobic biodigestion of sugarcane bagasse using chicken excreta as inoculum

The sugar cane and poultry industry are generators of a large amount of byproducts that can have their added value enhanced when used as an energy source. Thus, the objective of this study was to investigate the effect on anaerobic biodigestion of sugarcane bagasse in natura and pretreated with sodium hydroxide, using chicken excreta as inoculum. To do this, 600mL experimental biodigesters were used, with two treatments: 1 - sugarcane bagasse inoculated with bird excreta and 2 - sugarcane bagasse inoculated with bird excreta and added 4% sodium hydroxide solution (NaOH). The chemical composition of sugarcane bagasse and bird excreta were analyzed, as well as how the reactive sludge (substrate) were evaluated, before and after the period of 54 days. The variables of pH, DQO, total, volatile and fixed solids and also the production of methane gas (CH4) were analyzed. The results show that the treatment with 4% sodium hydroxide (NaOH) pretreatment presented better results in methane gas production and environmental evaluation parameters.

Mesophilic co-digestion of municipal solid waste and sewage sludge: Effect of mixing ratio, total solids, and alkaline pretreatment

A large number of biogas plants feeding with municipal solid waste (MSW) are installed throughout the world. However, researches are widely conducted with the aim of maximizing the process yield, in order to make it more comparable with fossil fuels. In the present paper, biomethane potential test (BMP) assays (37 °C) were conducted to maximize the biomethane production from anaerobic digestion (AD) of municipal solid waste (MSW) under different mixing ratios with sewage sludge (SS) (50:50, 60:40, 80:20, and 90:10), the total solid (TS) concentrations (5%, 10%, 15%, and 20%), and pretreatment with sodium hydroxide. Increase in SS ratio up to 40% led to a substantial increase in biomethane yield. After 18 days of retention time, 90% of the methane (280 NmL/g VS) was achieved. The results showed that the methane yield in liquid anaerobic digestion (L-AD) (5%-10% TS) was greater than high-solids anaerobic digestion (HS-AD) (15%-20% TS). Biomethane yield was increased up to 18% with sodium hydroxide pretreatment. The findings shows that such optimization framework can generally increase the biomethane yield up to 57%.

Comparison of alkaline and acid pretreatments for enzymatic hydrolysis of soybean hull and soybean straw to produce fermentable sugars

The specific characteristics of biomass structure and differences in chemical composition of soybean hull (SBH) and soybean straw (SBS) may result in different behavior of pretreatment and enzymatic hydrolysis. In this work, dilute sulfuric acid (DA) pretreatment and alkaline sodium hydroxide (AL) pretreatment in a range of pretreatment temperatures and durations were investigated to improve the enzymatic digestibility of SBH and SBS. Satisfactory enzymatic digestibility was observed in the hydrolysis of both pretreated soybean fractions, but SBH showed higher digestibility than that of SBS, no matter which pretreatment technology was applied. Furthermore, DA pretreatment was more effective than AL pretreatment in conversion of soybean fractions into fermentable sugars, if both pretreatment and enzymatic hydrolysis stages were considered. The highest total sugar yield of SBH and SBS using DA pretreatment and subsequently hydrolyzed with 30 FPU/g-DM cellulase were 86.9% and 70.3%, respectively.

Alkali Pretreatment and Acid Hydrolysis of Oil Palm Mesocarp Fiber (OPMF) to Produce Glucose

The uses of cellulose fibers in many fields have attracted significant scientific attention in the recent years. This research analyzed the amount of glucose produced from oil palm mesocarp fiber using sulphuric acid hydrolysis. Sodium hydroxide (NaOH) pretreatment with different concentrations of 5%, 10%, 15% and 20% w/v was conducted at 70 °C for a retention time of 2 h. The resulting fibers were examined using Fourier transform infrared (FTIR) analysis. The optimum conditions were 20% w/v sodium hydroxide (NaOH) at a temperature of 70 °C. The oil palm mesocarp fiber (OPMF) was then hydrolyzed using 5%, 10%, 15%, or 20% v/v sulphuric acid at varying temperatures of 30, 45, 60 and 90 °C for a treatment time of 2 h. Glucose concentration was tested using a UV spectrophotometer. The highest yield of glucose was 0.942 g/L using 20% v/v sulphuric acid and a temperature of 90 °C.

Enhanced ethanol production from Glycyrrhiza glabra residue by fungus Mucor hiemalis

Glycyrrhiza glabra residue (GGR) contains 30.5% cellulose and 23.0% hemicellulose and can be considered as a promising low-cost and non-edible feedstock for production of ethanol. For the first time, GGR was subjected to inexpensive sodium hydroxide (SH) pretreatment to enhance fermentable sugars production through enzymatic hydrolysis and subsequent utilization by fungus Mucor hiemalis. The pretreatment was carried out at 5% (w/v) solid loading and different temperatures (0, 28 and 110°C) with 2, 4, 6, 8 and 10% (w/v) SH solutions. When applying no pretreatment, the glucose and ethanol production yields through separated hydrolysis and fermentation of GGR were only 13.9% and 14.3%, respectively. However, a major improvement was achieved after alkali pretreatment of GGR and the maximum hydrolysis yield of 93.7% was observed when the substrate was pretreated with 4% SH solution at 28°C for 24h. Consequently, fermentation of the SH pretreated materials by M. hiemalis led to a maximum 5.9-fold increase in ethanol production yield (∼217kg per ton of GGR), which was slightly higher than the ethanol yield through the yeast Saccharomyces cerevisiae (∼207kg per ton of GGR). Semi-quantitative analyses of the substrate after pretreatment indicated that crystallinity reduction and expanded surface area were the main reasons for the observed improvements. In brief, the results revealed that SH pretreatment (4% w/v) at room temperature is an effective strategy to valorize GGR to ethanol through hydrolysis and fermentation by fungus M. hiemalis.

Optimization of Sodium Hydroxide Pretreatment Conditions to Improve Biogas Production from Asparagus Stover

Alkaline pretreatment was employed to enhance biogas production from asparagus stover with anaerobic digester in laboratory scale batch fermentation. Different pretreatment times (10, 18, 25 days), NaOH concentrations (2.5, 5, 7.5%), and water dose (20, 60, 100 mL) were tested to select the best pretreatment conditions. With response surface method (RSM) applied, the optimum pretreatment conditions were pretreatment time of 19d, NaOH concentration of 4.2%, water dose of 74 g.The biogas yield was predicted as 275.65 mL/g VS, while it was observed as 277.86 mL/g VS in the verification test, with the relative error of 0.80%. Further more, the verification tests show that contents of hemi-cellulose, cellulose and lignin after pretreatment were decreased by 65.20, 29.06 and 13.51%, respectively. The above results suggest that the effects of NaOH on degradations of hemi-cellulose and cellulose are higher than that on lignin.

Lactic acid production from Sophora flavescens residues pretreated with sodium hydroxide: Reutilization of the pretreated liquor during fermentation

The feasibility of lactic acid production from Sophora flavescens residues (SFRs) pretreated with sodium hydroxide with the reutilization of the pretreated liquor during fermentation was investigated. After sodium hydroxide pretreatment, 67.5% of the lignin was removed, and hydrolysis efficiency increased from 37.3% to 79.2%. The reutilization of pretreated liquor at 50% loading during open fermentation of unwashed SFR increased lactic acid production by 34.1%. The pretreated liquor acted as pH buffer and resulted in stable pH and high cellulase activity during fermentation. Inhibitors in the pretreated liquor did not affect the growth of lactic acid bacteria but severely inhibited the growth of ethanol-producing yeast. Consequently, lactic acid production increased and ethanol production was zero at 50% loading. Water consumption during pretreatment and fermentation with 50% pretreated liquor was 1.341L per 100g SFR, which was 67.6% lower than that during fermentation with washed SFR.

Economic viability of consolidated bioprocessing utilizing multiple biomass substrates for commercial-scale cellulosic bioethanol production

The depletion of fossil fuel resources requires a greater emphasis on the development of renewable energy technologies. Ethanol produced via biochemical means is a renewable liquid fuel option that shows great promise. In this paper, the large scale production of ethanol via a method of converting lignocellulosic material without the need for enzyme hydrolysis, termed consolidated bioprocessing (CBP), is analyzed and compared to traditional separate hydrolysis and fermentation (SHF) methods to determine the profitability of biochemical ethanol production. Optimal process topologies for both the CBP and SHF technologies are selected from superstructures considering multiple biomass feeds, chosen from those available across the United States, and multiple prospective pretreatment technologies. Steam cogeneration is also considered to produce the necessary hot utilities as well as electricity as a salable byproduct. Results show the optimal consolidated bioprocessing plant produces about 66 million gallons of ethanol to be sold at a breakeven price of $1.31 per gallon ($0.35 per liter) from a pure sugarcane bagasse feed and sodium hydroxide pretreatment method in addition to 67 MW of electricity per year. These results compare favorably to SHF production methods, showing a 20% decrease in the minimum ethanol selling price (MESP) and 197.5% increase in electricity generation despite a 13.3% drop in ethanol production. A long term economic evaluation is performed to determine an attractively profitable selling price for the ethanol produced. Additional analysis is done on the effect of a mixed biomass feed on process profitability and impact on biomass harvesting radius.

Vacuum-assisted alkaline pretreatment as an innovative approach for enhancing fermentable sugar yield and decreasing inhibitor production of sugarcane bagasse

Sodium hydroxide pretreatment of sugarcane bagasse under vacuum conditions was established and evaluated in this study. Compared to pretreatment under conventional moderate pressure conditions, only half of the total phenolic compounds and less than half of the formic acid were produced under vacuum conditions, while the yield of total fermentable sugar was significantly increased by 31.38%. The pretreatment parameters: NaOH concentration, pretreatment time, and pretreatment temperature, were optimized using response surface methodology based on the response values of the total fermentable sugar yield (TFSY) and the total fermentable sugar concentration (TFSC), respectively. Under the optimal conditions, the TFSY of 0.5146g/g and the TFSC of 17.37g/L were achieved, respectively. By adjusting the ratio of cellulases to xylanase, the TFSY reached a maximum of 0.5213g/g when the ratio was 1:1, while the maximum TFSC of 17.71g/L was achieved when the ratio was 1:4.

Ethanol production from hazelnut shells through enzymatic saccharification and fermentation by low-temperature alkali pretreatment

Low-temperature sodium hydroxide (NaOH) pretreatment, enzymatic saccharification and ethanol fermentation were evaluated for hazelnut shell cellulose to fermentable sugars and ethanol. Maximum glucose recovery (48.33g/100g cellulose) was achieved with 6% NaOH for 72h and at 1/10 solid/liquid ratio. At these conditions, 41.18% of lignin was removed. The theoretical ethanol yield (ethanol produced/potential glucose in biomass) was 40.71%, overall process efficiency was 37.73g/kg biomass, ethanol productivity and fermentation efficiency were 0.115g/(Lh) and 96.7%, respectively. Total energy consumed for the low-temperature–long-residence-time alkali process was 34.8MJ/kg untreated hazelnut shells. Pretreatment time has a significant effect on thermal energy consumption for the low-temperature alkali process.

Impact of Thermo-alkaline Pretreatment on the Thermophilic Anaerobic Digestion of Wheat Plant Residues

Background: Wheat plant (WP) residues could be efficiently used as substrate for biogas production via anaerobic digestion (AD). It is a mixture of starchy and lignocellulosic materials. The hydrolysis of wheat plant is the ratelimiting step of its AD. An efficient pretreatment can facilitate the wheat plant hydrolysis and accordingly enhance the AD’s efficiency. The aim of this study was to investigate the effects of thermo-alkaline pretreatment on the WP structure as well as the yield of thermophilic anaerobic digestion of WP. Methods: Anaerobic sludge was used as inoculum. Wheat plant (WP) including its straw and grains was used as substrate. The impact of sodium hydroxide pretreatment (8% w/w) on the thermophilic anaerobic digestion (55 °C) of wheat plant using anaerobic sludge in batch reactors was investigated. Pretreatments were performed at different temperatures of 0, 25, 50, 75, and 100 °C for 60 min. Results: The methane and biogas yields of the untreated WP were 182.1 and 287.3 mL/g VS, respectively. The pretreatments at 50 °C and 75 °C led to the highest methane yields of 232.9 and 358.6 mL/g VS, respectively, while the other pretreatments had no positive effects on the methane yield. The results of scanning electron microscopy showed that the surface of the WP was effectively destructed after pretreatment at 75 °C when compared with the untreated WP. Conclusion: Thermo-alkaline pretreatment (specially at 75 °C for 60 min) could efficiently enhance the yield of anaerobic digestion of wheat plant. Keywords: Anaerobic digestion, biomethane, NaOH, thermo-alkaline pretreatment, wheat plant.

Improving anaerobic digestion of sugarcane straw for methane production: Combined benefits of mechanical and sodium hydroxide pretreatment for process designing

Sodium hydroxide (NaOH) as an alkaline pretreatment method to enhance the degradation kinetics of sugarcane straw (SCS) for methane production was investigated with a special focus on the benefits for designing the anaerobic digestion process. For that, SCS was previously homogenized by milling in 2mm particle size and pretreated in NaOH solutions at various concentrations (0, 3, 6 and 12gNaOH/100gSCS) and the methane yields were determined in biochemical methane potential (BMP) tests. The obtained experimental data were used to simulate a large-scale semi-continuous process (100tonSCSday−1) according to a first-order reaction model and the main economic indicators were calculated based on cash flows of each pretreatment condition. The BMP tests showed that by increasing the NaOH concentration the conversion of the fibrous fraction of the substrate to methane was not only accelerated (higher α value), but also increased by 11.9% (from 260 to 291mLCH4gVS−1). By using the experimental data to simulate the large-scale process these benefits were translated to a reduction of up to 58% in the size of the anaerobic reactor (and consequently in electricity consumption for stirring), while the methane yield increased up to 28%, if the liquid fraction derived from the pretreatment process is also used for methane production. Although the use of NaOH for substrate pretreatment has considerably increased the operational expenditures (from 0.97 up to 1.97€×106year−1), the pretreatment method was able to increase the profitability of methane production from SCS since a sensitivity analysis by varying the prices of anaerobic reactor, methane and NaOH showed a less attractive payback, net present value and internal rate of return for the control condition (0gNaOH/100gSCS) in all analyzed scenarios.

Enhancing the Performance on Anaerobic Digestion of Vinegar Residue by Sodium Hydroxide Pretreatment

Vinegar residue (VR) is a by-product which produced by the process of vinegar production. To enhance the performance on methane production of VR and facilitate its resource utilization, sodium hydroxide (NaOH) pretreatment was carried out. Results showed that with the concentration of NaOH increased, the cumulative methane yield ascended first and then declined. At NaOH concentration of 3.0 %, the cumulative methane yield was 205.86 mL gVS−1 and improved 53.99 % comparing with the untreated VR. Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, and component analysis demonstrated the structural and compositional changes in VR after NaOH pretreatment. The results obtained in this study proved that NaOH pretreatment was really efficient for enhancing the capability of anaerobic digestion (AD) and increasing methane production. Through this technology, it not only provides a method to reduce the pollution to environment but also contributes to clean energy production. Meanwhile, the results of this research may serve as a promising and potential way for AD of VR in the future industrial applications.

Enhancement of In Situ Enzymatic Saccharification of Corn Stover by a Stepwise Sodium Hydroxide and Organic Acid Pretreatment

A stepwise pretreatment method that combines sodium hydroxide and organic acid pretreatments was proposed and investigated to maximize the recovery of main constituents of lignocellulose. The sodium hydroxide pretreatment was firstly optimized by a designed orthogonal experiment with the optimum pretreatment conditions determined as 1wt% NaOH at 70°C for 1h, and 60.42% of lignin was successfully removed during this stage. In the second stage, 0.5% acetic acid was selected to pretreat the first-stage solid residue at 80°C for 40min in order to decompose hemicelluloses to soluble oligomers or monomers. Then, the whole slurry was subjected to in situ enzymatic saccharification by cellullase with a supplementation of xylanase to further degrade the xylooligosaccharides generated during the acetic acid pretreatment. The maximum reducing sugar and glucose yields achieved were 20.74 and 12.03g/L, respectively. Furthermore, rapid ethanol fermentation and a yield of 80.3% also testified this pretreatment method, and the in situ saccharification did not bring any negative impact on ethanol fermentation and has a broad application prospect.

Intensification of sodium hydroxide pretreatment of corn stalk using magnetic field in a fluidic system

To promote NaOH pretreatment of corn stalk (CS), a continuous processing system uniting magnetic field and millimeter-scaled channel flow was established. First, four comparative pretreatments were conducted: (I) CS was pretreated with NaOH under traditional agitation; (II) CS was pretreated with NaOH in a flowing state inside the millimeter-scaled channel; (III) CS was pretreated with NaOH in a flowing state and under a static magnetic field; or (IV) CS was pretreated with NaOH in a flowing state and under a rotating magnetic field. By comparison, the highest pentose (121.22mg/g dry CS) and hexose (287.04mg/g dry CS) yields were obtained in the shortest pretreatment time with Pretreatment IV (8h). Accordingly, the key parameters of Pretreatment IV were optimized as 6.71Hz frequency, 0.50L/min flow rate, and 1.02% NaOH concentration. Under these conditions, 439.24mg sugars were released by 1g dry CS during pretreatment and enzymatic hydrolysis.

High conversion of sugarcane bagasse into monosaccharides based on sodium hydroxide pretreatment at low water consumption and wastewater generation

The generation of a great quantity of black liquor (BL) and waste wash water (WWW) has been key problems of the alkaline pretreatment. This work tried to build a sustainable way to recycle the BL for pretreating sugarcane bagasse (SCB) and the WWW for washing the residual solid (RS) of alkali-treated SCB which would be subsequently hydrolysed and fermented. The enzymatic hydrolysis efficiency of the washed RS decreased with the recycling times of BL and WWW increasing. Tween80 at the loading of 0.25% (V/V) could notably improve the enzymatic hydrolysis and had no negative impact on the downstream fermentation. Compared with the non-recycling and BL recycling ways based on alkaline pretreatment, the BL-WWW recycling way could not only maintain high conversion of carbohydrate into monosaccharides and save alkali amount of 45.5%, but also save more than 80% water and generate less than 15% waste water.

Microwave-Assisted Alkali Pretreatment for Enhancing Pineapple Waste Saccharification

The effectiveness of microwave-assisted sodium hydroxide pretreatments to enhance the saccharification performance of pineapple waste was evaluated. Microwave alkali pretreatments for short exposure times (up to 60 s) significantly improved the yield of the enzymatic hydrolysis compared with non-pretreated waste. The greatest increase of fermentable (35.7%) and total sugars (33.5%) was obtained at 6.375 W/g for 5 s. However, longer exposure times resulted in sugar degradation and released fermentation inhibitors, such as phenols or hydroxymethylfurfural (HMF), as a consequence of thermal degradation. Nevertheless, the obtained phenols values were not sufficient to inhibit subsequent fermentation. Scanning electron microscope (SEM) images confirmed that applying microwaves for short exposure times promoted structural changes that improved enzymatic hydrolysis. By contrast, an increase in the severity of the treatment led to a compacted structure, which hindered access to enzymes and consequently reduced the release of sugars into the medium.

Effect of Sodium Hydroxide Pretreatment on Rice Straw Composition

Background/Objectives : Sodium hydroxide (NaOH) pretreatmentwas used to determine the effect of pretreatment on chemical composition of pretreated rice straw. The experiment was designed to measure the effects in terms of NaOH concentration and pretreatment time mainly on the total carbohydrate content (TOC) and lignin content of pretreated rice straw. Methods/Statistical Analysis :Compositional characterization was performed based on the National Renewable Energy Laboratory (NREL) laboratory analysis protocols. Rice straw obtained from Sekinchan, Selangor Malaysia was dried to reduce the moisture content (<15%) and ground to 2 mm particle size. Rice straw was pretreated with different concentration of NaOH (2%w/v, 6%w/v and 12%w/v) and pretreatment time of 1 and 3 hours, while temperature was kept constant at 55°C. Findings: Rice straw sample pretreated with 12%w/v NaOH for 1 hour gave the highest glucan content, an increase of 85.6% from the native untreated rice straw. This condition also yielded the best delignification effect which reduced the lignin composition up to 79.6%, while sample pretreated with 2%w/v for 3 hours gave the highest composition on total carbohydrate content of 79.16% for which included glucan, xylan and arabinan.Hence, the pretreatment condition of 2%w/v NaOH concentration for 3 hours was the best condition in order to obtain high total carbohydrate content while severe pretreatment condition of 12%w/v NaOH concentration for 1 hours was best to give the delignification effect to the rice straw. Application/Improvements: The results from this work can be used for further evaluation of pretreated rice straw using NAOH particularly for enzymatic hydrolysis. Is useful in determining the carbohydrate conversion during the hydrolysis.

Thiosulfate leaching of Au, Ag and Pd from a high Sn, Pb and Sb bearing decopperized anode slime

Compared with Au+ and Ag+, Pd2+ is easier to be complexed by S2O32− in ideal situation, based on DFT (density functional theory) calculation. Thermodynamics analysis shows that palladium can also be effectively leached by ammoniacal thiosulfate solution besides gold and silver. The Sn and Sb in a high Au, Ag, Pd, Sn, Pb and Sb bearing decopperized anode slime had no obvious detrimental effect on thiosulfate leaching of the precious metals, but the Pb could cause seriously detrimental impact. Only 37.3% of Au, 69.2% of Ag and 43.8% of Pd in the decopperized anode slime could be extracted by direct thiosulfate leaching. After sodium hydroxide pretreatment where 56.9% of Pb and 13.6% of Sb in the slime were removed, thiosulfate leaching under optimal operating conditions only extracted 68.1% of Au, 81.7% of Ag and 67.6% of Pd in the pretreatment residue. The low extraction is probably because there was a PbO passivation layer on slime particle surfaces. After the carbonate transformation and subsequent acetic acid pretreatment in which 93.8% of Pb in the transforming residue was removed, thiosulfate leaching could extract as much as 88.0% of Au, 93.4% of Ag and 80.7% of Pd in the pretreatment residue. There was no such passivation layer on the surfaces of slime particles during the leaching, attributing to comparatively thorough removal of Pb by the pretreatment.

Ethanol production from alkali-pretreated oil palm empty fruit bunch by simultaneous saccharification and fermentation with mucor indicus

ABSTRACTOil palm empty fruit bunch (OPEFB) is a potential raw material for production of lignocellulosic bioethanol. The OPEFB was pretreated with 8% sodium hydroxide (NaOH) solution at 100°C for 10 to 90 min. Enzymatic digestion was carried out using cellulase and β-glucosidase at 45°C for 24 h. It was then inoculated with Mucor indicus spores suspension and fermented under anaerobic conditions at 37°C for 96 h. Sodium hydroxide pretreatment effectively removed 51–57% of lignin in the OPEFB and also its hemicellulose (40–84%). The highest glucan digestibility (0.75 g/g theoretical glucose) was achieved in 40-min NaOH pretreatment. Fermentation by M. indicus resulted in 68.4% of the theoretical ethanol yield, while glycerol (16.2–83.2 mg/g), succinic acid (0–0.4 mg/g), and acetic acid (0–0.9 mg/g) were its by-products. According to these results, 11.75 million tons of dry OPEFB in Indonesia can be converted into 1.5 billion liters of ethanol per year.