Bioethanol Production Process Research Articles

Lignin Decomposition in Hydrothermal Liquefaction Process using Red-Mud Catalyst

Lignin is produced as a by-product in kraft and bioethanol production processes as well as in the pulp and paper industry. Convensionally, most of it is burned for heat energy recovery, and only about 2% of it is utilized as a useful chemical synthesis. Recently, research has been actively conducted worldwide to replace various phenolic compounds produced in the existing petrochemical industry with lignin degradation products that are environment friendly. Under the subcritical condition (35 0℃, 2 hr, H2: 1 MPa), lignin was decomposed and converted to bio-oil in the presence of red-mud (RM) and activated red-mud (ARM) catalysts. In particular, when red mud was used as a catalyst, the HHV was increased by 11.45 MJ/kg compare to the Kraft lignin, while carbon (C) and hydrogen (H) contents were increased by 17.99% and 1.87% respectively. Moreover, the yield of bio oil was increased by 8% (with RM catalyst) and 1.8% (with ARM catalyst) compare to the control experiment. GC-MS results showed that the produced bio-oil was comprised of cetechol and guaiacol type monomers as the major compounds. The overall results suggested that the red mud catalyst increased the bio oil yield, high heating value (HHV), and catechol production during the lignin decomposition technique. Key words: Lignin, Hydrothermal Liquefaction, Subcritical Water, Aromatic Compound, Redmud

Selective fluorescence labeling: time-lapse enzyme visualization during sugarcane hydrolysis

Enzymatic biomass saccharification is an important process for bioethanol production. Hitherto, numerous cellulase cocktails (crude enzyme) have been developed to improve enzymatic activity. For this purpose, the synergy of incorporating hydrolase functionality within a cellulase cocktail is a key function. However, such synergistic action, by potentially numerous different enzyme types, on biomass tissue has not been considered despite the importance toward the realistic case of biomass saccharification. This study aims to visualize the behavior of each of the key cellulase components on biomass tissue during saccharification. Time-lapse fluorescence microscopy observations were conducted during saccharification of a thin transverse sugarcane section to monitor enzymes modified with a fluorescence dye. Statistical image analysis successfully demonstrated a unique adsorption/desorption behavior of each enzyme component. Particularly, the behavior of endoxylanase10 (Xyn10), which was recently discovered from Penicillium sp. as a high-performance xylanase, displayed remarkable adsorption on tissues of sugarcane, which accounts for the superior activity of the cellulase mixture with Xyn10.

Nonlinear analysis of cybernetic model for aerobic growth of Saccharomyces cerevisiae in a continuous stirred tank bioreactor. Static bifurcations

This article presents a nonlinear steady-state analysis of a continuous stirred tank bioreactor. The process of bioethanol production under aerobic conditions was analyzed. The kinetics of the growth of Saccharomyces cerevisiae microorganisms was described by the cybernetic model. This model includes metabolic reactions taking place in the biomass cells, which are a response to changes in the extracellular process environment. The dilution rate and the glucose concentration in the feed stream were used as bifurcation parameters. In both cases the performed analysis revealed the existence of multiple steady states areas and Hopf bifurcation points. The continuation of steady states, relative to the concentration of glucose in the feed stream, showed the presence of a rarely detected steady state branch, which was an isola. The numerical investigation was summerized in the form of a map which contains areas with biochemical reactions favoured by biomass cells. The map is made in a coordinate system of bifurcation parameters and illustrates perfectly the complexity of the model. In the opinion of the authors, it can be a very useful tool in planning the implementation of the process. It enables its proper targeting in the direction of activation of a specific metabolic reaction in the cells of microorganisms.

STATE ESTIMATION AND TRAJECTORY TRACKING CONTROL FOR A NONLINEAR AND MULTIVARIABLE BIOETHANOL PRODUCTION SYSTEM

In this paper a controller is proposed based on linear algebra for a fed-batch bioethanol production process. It involves finding feed rate profiles (control actions obtained as a solution of a linear equations system) in order to make the system follow predefined concentration profiles. A neural network states estimation is designed in order to know those variables that cannot be measured. The controller is tuned using a Monte Carlo experiment for which a cost function that penalizes tracking errors is defined. Moreover, several tests (adding parametric uncertainty and perturbations in the control action) are carried out so as to evaluate the controller performance. A comparison with another controller is made. The demonstration of the error convergence, as well as the stability analysis of the neural network, are included.

Gasoline pre-blending processes for efficient ethanol recovery: effects of process parameters and process modifications for improved performance

With over 20 billion gallons of bio-ethanol produced annually, optimization of bio-ethanol production processes is a major priority for sustainability research. Recent research has made great strides toward improving the efficiency of bio-ethanol production through the development of gasoline pre-blending processes which use liquid–liquid phase separation to eliminate excess water with minimal energy input. This paper investigates the effects of process parameters on the performance and efficiency of this class of processes, offering a design basis for engineers developing new processes along with a broader understanding of their potential performance and economic value. Also explored are a range of process modifications capable of improving process performance. It has been found that blending ratio and initial alcohol concentration are the key parameters in determining ethanol recovery, with the number of liquid–liquid contact stages and the temperature also being significant. It has also been shown that temperature-swing decanting can significantly improve alcohol recovery, reducing ethanol losses by as much as 33% in a typical gasoline pre-blending setup.

Valorization of Eucalyptus nitens bark by organosolv pretreatment for the production of advanced biofuels

The biofuels production from alternative and renewable raw materials is mandatory to achieve sustainable growth based on a bioeconomy. Eucalyptus bark is a waste generated during the chemical manufacturing of Eucalyptus pulp that can be used as an alternative source of biomass, suitable for the production of biofuels. In this work, Eucalyptus nitens bark (ENB) was fractionated by organosolv treatment for ethanol production. For that, a Doehlert experimental design was carried out to evaluate the dependent variables: temperature (170–200 °C), time (30–90 min) and ethanol-water percentage (50–80 %) on delignification of Eucalyptus bark. Organosolv process was suitable for the fractionation of E. nitens bark. After treatment, 74–93 % of glucan was recovered and 25–52 % of delignification was achieved. Delignified ENB was subjected to simultaneous saccharification and fermentation process for bioethanol production. The results showed that the variables temperature and time of organosolv process had significant influence on ethanol production. The organosolv pretreatment improved the ethanol yield from 32 to 99%. This work shows a suitable process for the valorization of Eucalyptus bark into bioethanol.

Modeling growth and fermentation inhibition during bioethanol production using component profiles obtained by performing comprehensive targeted and non-targeted analyses

Corn cob and corn stover hydrolysates are forms of lignocellulosic biomass that can be used in second generation bioethanol production and biorefinery processes. Growth and fermentation inhibitors generated during physicochemical and enzymatic hydrolysis decrease ethanol and biomaterial production during the subsequent biological processes. Here, estimates of growth and fermentation inhibition during bioethanol fermentation were made using component profiles of corn cobs and corn stover at different degrees of hydrolysis. The component profiles were acquired by non-targeted gas chromatography mass spectrometry and targeted high-performance liquid chromatography. Correlations between the comprehensive analysis results and yeast growth and ethanol production were modeled very accurately by partial-least-squares regression analysis. Acetate, apocynin, butyrovanillone, furfural, furyl hydroxymethyl ketone, m-methoxyacetophenone, palmitic acid, syringaldehyde, and xylose, were compounds with very variable importance in projection values and had negative correlation coefficients in the model. In fact, methoxyacetophenone, apocynin, and syringaldehyde inhibited fermentation more than furfural in equivalent concentration.

Potential of bioethanol production waste for methane recovery

Lignocellulosic biomass is emerging as an important feedstock for biofuel production. Bioethanol is one of the most common liquid biofuels in the transportation sector. However, its production process is still inefficient due to the large quantity of production waste that is left unused after the distillation process. In this paper, the biomethane potential of bioethanol production waste is analysed. The results are compared with the biomethane potential of samples from different stages of the bioethanol production process (pretreatment, hydrolysis and fermentation), and that of untreated biomass. In this study, barley straw is used as a biomass crop and N2 explosive decompression (NED) is applied as a pretreatment method. The results show that bioethanol production waste has higher methane yields (1.17 mol CH4/100 g) than raw barley straw (1.04 mol CH4/100 g). Production waste also has a higher degradation rate (0.252) than untreated material (0.138), and achieves 95% of the maximum methane yield much faster (7.8 days) than untreated samples (22 days). This shows that production waste can be used for further anaerobic digestion (AD) to add value to the bioethanol production chain. NED pretreatment is an effective method of pretreatment.

Net Energy Analysis of Molasses Based Bioethanol Production in Indonesia

Molasses is mostly used as feedstock for the bioethanol production in Indonesia. Bioethanol industries has the potential to be more developed if the mandate of blending gasoline with 5% bioethanol is implemented. However, some previous studies abroad have shown that mostly the net energy for producing bioethanol is negative. The main purpose of this research is to analyze the net energy requirement if a bioethanol conversion plant from scenario of a bioethanol producer in East Java. Bioethanol conversion processes inside the plant are pre-fermentation, fermentation, evaporation, distillation and dehydration. Method which was used in this research are modelling and calculation made on monthly basis for plant capacity of 30,000 KL/ year ethanol of 99.5% purity. The result shows that the total energy required to produce 1 L of ethanol is 4.55 MJ. The energy content of 1 L ethanol is 23.46 MJ. The largest energy requirement is for evaporation process (62%) followed by distillation process (33%). Thus, the net energy requirement for bioethanol production process is positive.

Optimization of bioethanol production from soybean molasses using different strains of Saccharomyces cerevisiae

Bioethanol technology represents an important scientific research area because of the high market value and wide availability of its primary and by-products. Worldwide interest in utilizing bioethanol as a renewable and sustainable energy source has significantly increased in the last few years due to limited reserves of fossil fuels and concerns about climate change. Therefore, improvement of the bioethanol production process is a priority research field at the international scale, due to both economic and environmental reasons. The aim of this study was to optimize production of bioethanol from soybean molasses based media using response surface methodology. Three different strains of the yeast Saccharomices cerevisiae, commercially available in dried form, were used as production microorganisms, and the best results were obtained by using dried baker?s yeast. The results of optimization of alcoholic fermentation using dried baker?s yeast indicate that the highest value of the overall desirability function (0.945) is obtained when the initial sugar content is 18.10 % (w/v) at the fermentation time of 48.00 h. At these conditions the model predicts that bioethanol concentration is 8.40 % (v/v), yeast cell number 2.21?108 cells/mL and the residual sugar content is 0.35 % (w/v).

Process operation performance of PDMS membrane pervaporation coupled with fermentation for efficient bioethanol production

Abstract There would be strong product inhibition on ethanol fermentation process if ethanol is not removed in situ from broth. PDMS membrane pervaporation coupled with fermentation is a promising process for efficient bioethanol production since ethanol inhibition is relieved or eliminated. From the perspective of process operation, membrane separation performance, ethanol fermentation performance and the subsequent processing on membrane downstream are the three key issues. This review aims at contributing a comprehensive overview on the operation performance of the integrated process. The state-of-the-art of the three key issues related to the operation performance is focused. Finally, the tentative perspective on the possible future prospects of the integrated process is briefly presented.

Sequential catalytic-mixed-milling and thermohydrolysis of cassava starch improved ethanol fermentation

Cassava starch is an abundant feedstock for biological transformation to ethanol, however, its industrial processing needs further improvements to enhance efficiency and cost-effectiveness. In the present study, a low-cost catalyst (CC–SO3H) was synthesized by partial carbonization and sulfonation of crystalline cellulose, which was thermally stable and reactive at 160°C in 5 times repeated batch of thermohydrolysis of cassava starch. The catalyst was studied for its potential role in the hydrolysis of cassava starch as a standard feedstock. It was shown that the milling of cassava starch in the presence of the CC–SO3H catalyst improved the solid-state reaction that enhanced porosity, increased surface area and decreased crystallinity of the starch granules. These phenomena caused the rapid thermohydrolysis of starch with an exceptionally high starch conversion rate (96.43%), glucose yield (93.12%), and glucose selectivity (95.32%) within 2h of reaction at 160°C, 10bar. The highest ethanol yield (0.43g ethanol/g total reducing sugars) was achieved at 96h of fermentation corresponding to the highest ethanol concentration of 15.41g/L from the fermentation of hydrolysate of mixed-milling/thermo-hydrolysis at 160°C for 2h of cassava starch. In addition, the reaction kinetics showed the feasibility of this process for robust bioethanol production from starchy feedstocks.

Continuous production of bioethanol using microalgal sugars extracted from Nannochloropsis gaditana

We developed a continuous production process of bioethanol from sugars extracted from Nannochloropsis gaditana. To improve algal sugar production, the reaction conditions of acid-thermal hydrolysis were investigated based on five different types of acid and their concentrations (1-4%), and the loading ratio of solid/liquid (S/L). As a result, the maximum hydrolysis efficiency (92.82%) was achieved under 2% hydrochloric acid with 100 g/L biomass loading at 121 oC for 15 min. The hydrolysates obtained from N. gaditana were applied to the main medium of Bretthanomyces custersii H1-603 for bioethanol production. The maximum bioethanol production and yield by the microalgal hydrolysate were found to be 4.84 g/L and 0.37 g/g, respectively. In addition, the cell immobilization of B. custersii was carried out using sodium alginate, and the effect of the volume ratio of cell/sodium alginate on bioethanol productivity was investigated in a batch system. The optimal ratio was determined as 2 (v/v), and the immobilized cell beads were applied in the continuous stirred tank reactor (CSTR). Continuous ethanol production was performed using both free cells and immobilized cells at 1 L CSTR. In both groups, the maximum bioethanol production and yield were achieved at dilution rate of 0.04 h-1 (3.93 g/L and 0.3 g/g by free cell, and 3.68 g/L and 0.28 g/g by immobilized cell, respectively).

In-Situ Vacuum Assisted Gas Stripping Recovery System for Ethanol Removal from a Column Bioreactor

A three-step process consisting of biomass hydrolysis, fermentation and in-situ gas stripping by a vacuum assisted recovery system, was optimized to increase the ethanol production from sugar beet pulp. The process combines the advantages of stripping and vacuum separation and enhances the fermentation productivity through in-situ ethanol removal. Using the design of experiment and response surface methodology, the effect of major factors in the process, such as pressure, recycling ratio and solids concentration, was tested to efficiently remove ethanol after the combined hydrolysis and fermentation step. Statistical analysis indicates that a decreased pressure rate and an increased liquid phase recycling ratio enhance the productivity and the yield of the strip-vacuum fermentation process. The results also highlight further possibilities of this process to improve integrated bioethanol production processes. According to the statistical analysis, ethanol production is strongly influenced by recycling ratio and vacuum ratio. Mathematical models that were established for description of investigated processes can be used for the optimization of the ethanol production.

Water resources planning in bioethanol production from sugarcane

The biofuels industry has grown and has positioned itself in Colombia for national purposes, these come from biomass sources such as agricultural crops. Bioethanol is the most used in Colombia and is obtained from sugarcane. One of the main concerns of the sector and society, is the high water consumption associated with agricultural crops (9,000 m3 / ha-year), there are currently 232,000 hectares of sugarcane for the production of sugar and bioethanol. Given the aforementioned, the need arises to carry out a planning of industrial increase of the sector taking into account as a main base the demand and availability of water resources for different activities in the Cauca river basin and the demand for sugarcane crops. In this document it is presented a mathematical model and the evaluation of different scenarios of the estimation of the trend of water consumption in the bioethanol production process in Colombia and in this way to establish scenarios of high risk of water shortage both for the population, interested parties and cane cultivation.

Study of the Application of Alkaline Extrusion to the Pretreatment of Eucalyptus Biomass as First Step in a Bioethanol Production Process

Eucalyptus biomass was studied as a feedstock for sugars release using an alkaline extrusion plus a neutralization-based pretreatment. This approach would be a first step in a bioconversion process aimed at obtaining fuel bioethanol from eucalyptus biomass. The best operation conditions of extrusion (screw speed, temperature, liquid to solid ratio and NaOH amount) that lead to an effective destructuration of lignocellulose and enhanced sugar release were investigated. Two process configurations, with and without filtration inside the extruder, were tested. In the case without filtration, washed and not washed extrudates were compared. It was demonstrated that filtration step was convenient to remove inorganic salts resulting from neutralization and to promote the mechanical effect of extrusion, but limitations in the machine used in the work prevented testing of temperatures above 100 °C using this configuration. In the no filtration strategy, a temperature of 150 °C allowed attaining the highest glucan and xylan conversion rates by enzymatic hydrolysis of extruded biomass, almost 40% and 75%, respectively, of the maximum yield that could be attained if all carbohydrates contained in raw eucalyptus were converted to sugars. Some of the mechanisms and individual effects underlying alkaline extrusion of eucalyptus were figured out in this work, providing guidelines for a successful pretreatment design that needs to be further studied.

The effect of flue gas explosive decompression pretreatment on methane recovery from bioethanol production waste

Lignocellulosic biomass is an attractive feedstock for the production of liquid (eg. biofuel) or gaseous (eg. methane) fuels for the transportation sector. The bioethanol production process still produces a large quantity of production waste following the distillation process. Stillage consists mostly of lignin, hemicellulose, extractives, and yeast and therefore does not have any commercial value. The conversion of bioethanol production waste into gaseous biofuels like biogas or biomethane is a promising solution when it comes to transforming stillage into value-added products, enhancing the value of the biomass, and as a strategy for achieving zero-waste societies. This study aims to investigate the potential of bioethanol production waste for biomethane production. The results are compared with samples from different stages of the bioethanol production process. Milled barley straw (Hordeum vulgare) was used as a feedstock to produce energy in the form of methane, and the flue gas pre-treatment method (with and without bubbling) was applied. The results show that the methane production yield of bioethanol production waste, which has been pretreated with flue gas without bubbling is 5% higher than that of untreated substrate, and can achieve 94% of the methane production of fermented samples. Bioethanol production waste from substrates, which have been pretreated with flue gas with bubbling have a methane production level that is 29% higher than that of untreated materials. The results suggest that methane yields are influenced by the bubbling process. It is reasonable to use bioethanol production waste for the production of energy in the form of methane and to increase the energy output from the biomass.

Efficient pretreatment of lignocellulosic biomass with high recovery of solid lignin and fermentable sugars using Fenton reaction in a mixed solvent

BackgroundPretreatment of biomass to maximize the recovery of fermentable sugars as well as to minimize the amount of enzyme inhibitors formed during the pretreatment is a challenge in biofuel process. We develop a modified Fenton pretreatment in a mixed solvent (water/DMSO) to combine the advantages of organosolv and Fenton pretreatments. The hemicellulose and cellulose in corncob were effectively degraded into xylose, glucose, and soluble glucose oligomers in a few hours. This saccharide solution, separated from the solid lignin simply by filtration, can be directly applied to the subsequent enzymatic hydrolysis and ethanol fermentation.ResultsAfter the pretreatment, 94% carbohydrates were recovered as soluble monosaccharide (xylose and glucose) and glucose oligomers in the filtrates, and 87% of solid lignin was recovered as the filter residue. The filtrates were directly applied to enzymatic hydrolysis, and 92% of raw corncob glucose was recovered. The hydrolysates containing the glucose and xylose from the enzymatic hydrolysis were directly applied to ethanol fermentation with ethanol yield equals 79% of theoretical yield. The pretreatment conditions (130 °C, 1.5 bar; 30 min to 4 h) are mild, and the pretreatment reagents (H2O2, FeCl3, and solvent) had low impact to environment. Using ferrimagnetic Fe3O4 resulted in similar pretreatment efficiency and Fe3O4 could be removed by filtration.ConclusionsA modified Fenton pretreatment of corncob in DMSO/water was developed. Up to 94% of the carbohydrate content of corncob was recovered as a saccharide solution simply by filtration. Such filtrate was directly applied to the subsequent enzymatic hydrolysis and where 92% of the corncob glucose content was obtained. The hydrolysate so obtained was directly applied to ethanol fermentation with good fermentability. The pretreatment method is simple, and the additives and solvents used have a low impact to the environment. This method provides the opportunity to substantially maximize the carbohydrate and solid lignin recovery of biomass with a comparatively green process, such that the efficiency of biorefinery as well as the bioethanol production process can be improved. The pretreatment is still relatively energy intensive and expensive, and further optimization of the process is required in large-scale operation.

Conditions promoting effective very high gravity sugarcane juice fermentation

BackgroundApplying very high gravity (VHG) fermentation conditions to the sugarcane juice (SCJ) bioethanol industry would improve its environmental and economic sustainability without the need for major infrastructure changes or investments. It could enable a decrease in the consumption of biological and natural resources (cane/land, water and energy) while maintaining acceptable production parameters. The present study attempts to demonstrate and characterise an effective industrially relevant SCJ-VHG fermentation process.ResultsAn industry-like SCJ-VHG bioethanol production process with 30 and 35 °Bx broth was employed to investigate the effects of both the yeast strain used and nitrogen source supplementation on process yield, process productivity, biomass viability, glycerol concentration and retention-associated gene expression. Process performance was shown to be variably affected by the different process conditions investigated. Highest process efficiency, with a 17% (w/v) ethanol yield and only 0.2% (w/v) sugar remaining unfermented, was observed with the Saccharomyces cerevisiae industrial strain CAT-1 in 30 °Bx broth with urea supplementation. In addition, efficient retention of glycerol by the yeast strain was identified as a requisite for better fermentation and was consistent with a higher expression of glycerol permease STL1 and channel FPS1. Urea was shown to promote the deregulation of STL1 expression, overcoming glucose repression. The consistency between Fps1-mediated ethanol secretion and ethanol in the extracellular media reinforces previous suggestions that ethanol might exit the cell through the Fps1 channel.ConclusionsThis work brings solid evidence in favour of the utilisation of VHG conditions in SCJ fermentations, bringing it a step closer to industrial application. SCJ concentrated up to 30 °Bx maintains industrially relevant ethanol production yield and productivity, provided the broth is supplemented with a suitable nitrogen source and an appropriate industrial bioethanol-producing yeast strain is used. In addition, the work contributes to a better understanding of the VHG-SCJ process and the variable effects of process parameters on process efficiency and yeast strain response.

Systematic procedure and framework for synthesis and evaluation of bioethanol production processes from lignocellulosic biomass

Bioethanol from lignocellulosic feedstock rises as a promising alternative to replace liquid fossil fuels in the energy market for the next years. However, the variety of available biomass combined with the necessity of possible pretreatments and their particular features make it difficult to clearly identify the favorable process routes. In this study a systematic approach consisting of seven steps was proposed to obtain possible and feasible alternatives for the conversion of lignocellulosic biomass into bioethanol. The method was exemplified with the aid of a general case study, from the biomass selection to possible by-products generation. The case study resulted in a corn stover based process to produce bioethanol through ammonia fiber explosion pretreatment. Following the systematic approach different alternatives were proposed to finally obtain the optimal flowsheet with a minimum ethanol selling price of 0.43$/kg of ethanol, 35.4% lower than the initial process.