Bioethanol Recovery Research Articles

Exergy analysis of pretreatment processes of bioethanol production based on sugarcane bagasse

Bioethanol produced from LB (lignocellulosic biomass) is a renewable option to decrease fossil fuel demand. LB is considered the future feedstock for bioethanol production because of its low cost and availability. The production of bioethanol from LB involves different steps: pretreatment, hydrolysis, fermentation, and bioethanol recovery. Some pretreatments such as SE (steam explosion), LHW (liquid hot water), ammonia fiber explosion and acid hydrolysis treatment have been used frequently to remove lignin and to improve the saccharification of cell wall carbohydrates. In this work via exergy analysis biomass pretreatment methods to prepare LB for bioethanol production using two typical chemical compositions of sugarcane bagasse are evaluated. Four case studies for the following pretreatment technologies (A) SE, (B) Organosolv, (C) LHW and (D) SE + LHW are studied. Although high exergy values are obtained in all cases of this study (A) 93.2%, (B) 85.4%, (C) 94.1%, and (D) 95.1%, the values of destroyed exergy rate found for the cases analyzed using the raw material 2 are high compared to the input bagasse exergy rate, (A) 7.2%, (B) 24.8%, (C) 6.0%, and (D) 5.5%, highlighting the relevance of such processes in the overall exergy efficiency of second-generation bioethanol production routes.

Saccharification and liquefaction of cassava starch: an alternative source for the production of bioethanol using amylolytic enzymes by double fermentation process.

BackgroundCassava starch is considered as a potential source for the commercial production of bioethanol because of its availability and low market price. It can be used as a basic source to support large-scale biological production of bioethanol using microbial amylases. With the progression and advancement in enzymology, starch liquefying and saccharifying enzymes are preferred for the conversion of complex starch polymer into various valuable metabolites. These hydrolytic enzymes can selectively cleave the internal linkages of starch molecule to produce free glucose which can be utilized to produce bioethanol by microbial fermentation.ResultsIn the present study, several filamentous fungi were screened for production of amylases and among them Aspergillus fumigatus KIBGE-IB33 was selected based on maximum enzyme yield. Maximum α-amylase, amyloglucosidase and glucose formation was achieved after 03 days of fermentation using cassava starch. After salt precipitation, fold purification of α-amylase and amyloglucosidase increased up to 4.1 and 4.2 times with specific activity of 9.2 kUmg-1 and 393 kUmg-1, respectively. Concentrated amylolytic enzyme mixture was incorporated in cassava starch slurry to give maximum glucose formation (40.0 gL-1), which was further fermented using Saccharomyces cerevisiae into bioethanol with 84.0% yield. The distillate originated after recovery of bioethanol gave 53.0% yield.ConclusionAn improved and effective dual enzymatic starch degradation method is designed for the production of bioethanol using cassava starch. The technique developed is more profitable due to its fast liquefaction and saccharification approach that was employed for the formation of glucose and ultimately resulted in higher yields of alcohol production.

A biorefinery concept for simultaneous recovery of cellulosic ethanol and phenolic compounds from oil palm fronds: Process optimization

In this study, process optimization of an ultrasonic-assisted organosolv/liquid oxidative pretreatment (SOP) of oil palm fronds (OPFs) for the simultaneous recovery of cellulose, bioethanol and biochemicals (i.e. phenolic compounds) in a biorefinery concept was carried out. The effects of time (30–60min.), temperature (40–80°C), NaOH concentration (1–5%) and sample:solvent ratio (1:10–1:50g/ml) on cellulose content, bioethanol yield and total phenolics contents (TPC) after SOP were investigated. At optimum conditions of pretreatment (i.e. 60°C, 40min, 3% w/v aq. NaOH and 1:20g/ml sample to solvent ratio), the recovered cellulose (55.30%) which served as substrate for enzymatic hydrolysis and subsequent fermentation yielded about 20.1g/l glucose, 11.3g/l xylose and 9.3g/l bioethanol (yield of 0.769g/g). The pretreatment liquor (mostly regarded as wastes) obtained at the optimum pretreatment conditions contained about 4.691mg gallic acid equivalent (GAE)/g OPFs of TPC, 0.297mg vanillic acid (VA)/g OPFs, 1.591mg gallic acid (GA)/g OPFs and 0.331mg quercetin (QU)/g OPFs. The pretreatment liquor was again analyzed to possess high antiradical scavenging activity (about 97.2%) compared to the synthetic antioxidant, 3,5-di-tert-butyl-4-hydroxytoluene (BHT) (80.7%) at 100ppm. Thus one sustainable way of managing wastes in biorefinery is the recovery of multi-bioproducts (e.g. bioethanol and biochemicals) during the pretreatment process.

A review of membrane technology for bioethanol production

Abstract Bio-ethanol as a clean and renewable fuel has gained more attention; however greater energy inputs make a slow progress in industry. Membrane technology has potential in the bioethanol production process as a highly selective and energy-saving separation process. This review presented membrane technologies applied in three aspects: (i) microalgae harvesting, (ii) sugar concentration and detoxification, (iii) bioethanol recovery. The performance of different membrane processes was summarized and compared. The advantages and limitations of membrane technologies for these applications are discussed, and it was thought that the hybrid process has great potential in improving membrane efficiency.

HiGee Stripper-Membrane System for Decentralized Bioethanol Recovery and Purification

Economic production of bioethanol from lignocellulosic feedstock is one of the important solutions to the rising environmental concerns and depleting crude-oil reserves. However, feedstock available for bulk production of bioethanol is spread over a wide horizon and is of low-energy density, and bioethanol produced in the fermentor is dilute (∼5 wt %), which significantly increases the energy required for and cost of bioethanol production. To address these issues, the present article introduces a process-intensified technology, namely, HiGee (short for high gravity) stripper combined with a membrane (HSM) process for concentrating bioethanol. The performance of HSM is compared with one of the best energy-efficient process for bioethanol purification in the literature. Design, optimization, and technoeconomic evaluation of both the processes are performed, and the HSM process is found to be compact, require lower capital and operating costs, and have a high turndown ratio over the conventional process. The...

Recovering bioethanol from olive bagasse fermentation by nanofiltration

The aim of this manuscript was the study of the recovery of bioethanol produced by the fermentation of the lignocellulosic biomass (olive bagasse) by nanofiltration. In terms of downstream processing, the nanofiltration permeate stream was expected to be comprised mostly of water and ethanol, and as such, ethanol may be further recovered by conventional distillation. Different nanofiltration membranes (NF90 and NF270) were tested for their efficiency in the separation of bioethanol. Model aqueous solutions of ethanol and sugars, and real liquors were processed by nanofiltration focusing on flux and rejection performance. The results shown that the more complex medium of a real liquor interacts with the membrane and lower the rejection to target solutes. Generally, both membranes tested were suitable for separating and recovering ethanol from a fermentation medium. The diafiltration mathematical model developed in this work shown to be capable of describing experimental results, which may be considered extremely important for process design and scaling up purposes.

Separation technologies for current and future biorefineries—status and potential of membrane‐based separation

Biorefinery is one of the most important industries in the modern world, as it provides a variety of products, particularly renewable bioenergy, which is highly vital to human existence (?). Among the separation technologies applied in biorefinery, membrane‐based separation has received great attention in past decades as it is in line with the worldwide move toward higher energy efficiency and lower environmental impact. Analysis of the academic and industrial activities being undertaken reveals that porous membranes like nanofiltration, ultrafiltration, and microfiltration are generally associated with pretreatment and hydrolysis procedures where separation is relied on for recovering value‐added materials with wide range of molecular weight and facilitating follow‐up bioconversion. An emerging field that highly appreciates porous membranes is biodiesel purification. Molecular level separations including gas product separation existing in thermal and anaerobic conversions and liquid alcoholic products recovery in microbial/enzymatic process offer more opportunity to membrane‐based gas separation and pervaporation using dense membranes. Membrane distillation and supported liquid membrane, commonly classed as new generation of membrane technology, show the potential in bioethanol recovery and hydrolysis step, respectively. Nonetheless, their competitiveness is to be confirmed. The function of membrane separation is being pushed further. Bearing in mind the importance of membranes with higher quality in terms of separation efficiency and material stability, we must also be prepared for the challenges deriving from some engineering aspects such as membrane fouling, module design, and process optimization.This article is categorized under: Bioenergy > Science and Materials

Analysis of the Reflux Ratio on the Batch Distillation of Bioethanol Obtained from Lignocellulosic Residue

Aiming for sustainable and low-cost production, bioethanol production using lignocellulosic wastes, such as sugarcane bagasse and waste from banana crops, has been extensively explored. The recovery step is usually carried out during the distillation process and is challenging, particularly regarding energy issues. This study aimed to evaluate the bioethanol recovery from banana culture waste as a function of the reflux ratio in a process employing a batch distillation column. Tests were performed using a standard mixture of ethanol and water and using total reflux and ratios 0.5, 1 and 2. As expected, the best result was obtained with the highest reflux ratio, and it was under this condition that the broth obtained from the fermentation process was distilled. The maximum ethanol t in the distillate was 67% (wt%), which is less than the 93% composition that was obtained using the standard mixture; however, this is a promising result because inferior values are typically obtained in distilleries using a single column. Also, this value is close to others reported in literature for bioethanol distillation obtained with different residues and higher reflux ratio. Batch distillation is appropriate and feasible for implementation in the production of bioethanol from banana waste in small production units intended for the production of biofuels, beverages or commercial alcohol.

Measurements and thermodynamic modeling of the ethanol–water system with emphasis to the azeotropic region

Recovery of bioethanol from the fermentation broth is classically achieved by distillation. The design and optimization of the distillation requires a reliable thermodynamic model that describes sufficiently the properties of the ethanol/water mixture, and, especially, the vapor–liquid equilibrium (VLE) near the azeotropic point. The purpose of this study is twofold: first, to provide new reliable low-pressure VLE data for the ethanol/water mixture with emphasis given near the azeotropic region, and second, to develop new temperature-dependent binary interaction parameters for three excess Gibbs energy models (UNIQUAC, Wilson and NRTL), by fitting simultaneously VLE data, azeotropic points and excess enthalpies for this mixture.

Extraction Equilibrium of Ethanol for Bioethanol Production — Solvent Selection and Liquid-liquid Equilibrium Measurement —

Ethanol distributions between selected organic and aqueous phases were measured for recovery and concentration of bioethanol from fermented solution. The strategy of solvent selection was based on the background of biofuel production, and m-xylene was selected as the primary solvent and capric acid, 1-hexanol and 2-ethyl hexanol secondary solvents were utilized to enhance the ethanol solubility. The extraction performance was evaluated through the liquid-liquid equilibrium. m-Xylene showed low distribution coefficient of ethanol and high separation selectivity of ethanol relative to water. All secondary solvents increased the distribution coefficient. The separation selectivity was greatly reduced by capric acid, but was similar for 1-hexanol and 2-ethyl hexanol. The two phase region was smaller for 1-hexanol than for 2-ethyl hexanol, chosen as the best secondary solvent. Examination of the effects of 2-ethyl hexanol concentration in the solvent found that a small amount of 2-ethyl hexanol could enhance the distribution coefficient and maintain the separation selectivity constant. The measured liquid-liquid equilibria were estimated with the ordinary and modified UNIFAC methods. Both methods could predict the liquid-liquid equilibrium behaviors of the measured systems, but the modified UNIFAC method could show a better correlation. However, the water concentrations in the organic phases were estimated to be larger than the measured values if the measured concentrations were very low.

Stabilization of bioethanol recovery with silicone rubber‐coated ethanol‐permselective silicalite membranes by controlling the pH of acidic feed solution

AbstractIn order to produce highly concentrated bioethanol by pervaporation using an ethanol‐permselective silicalite membrane, techniques to suppress adsorption of succinic acid, which is a chief by‐product of ethanol fermentation and causes the deterioration in pervaporation performance, onto the silicalite crystals was investigated. The amount adsorbed increased as the pH of the aqueous succinic acid solution decreased. The pervaporation performance also decreased with decreasing pH when the ternary mixtures of ethanol/water/succinic acid were separated. Using silicalite membranes individually coated with two types of silicone rubber, pervaporation performance was significantly improved in the pH range of 5 to 7, when compared with that of non‐coated silicalite membranes in ternary mixtures of ethanol/water/succinic acid. Moreover, when using a silicalite membrane double‐coated with the two types of silicone rubber, pervaporation performance was stabilized at lower pH values. In the separation of bioethanol by pervaporation using the double‐coated silicalite membrane, removal of accumulated substances having an ultraviolet absorption maximum at approximately 260 nm from the fermentation broth proved to be vital for efficient pervaporation. Copyright © 2005 Society of Chemical Industry