Bioethanol Production Process Research Articles

Systematic design of separation process for bioethanol production from corn stover

Separation process is very crucial in bioethanol production as it consumes the highest energy in the process. Unlike other works, this research systematically designed a suitable separation process for bioethanol production from corn stover by using thermodynamic insight. Two separation processes, i.e., extractive distillation (case 2) and pervaporation (case 3), were developed and compared with conventional molecular sieve (case 1). Process design and simulation were done by using Aspen Plus program. The process evaluation was done not only in terms of energy consumption and process economics but also in terms of environmental impacts. It was revealed that pervaporation is the best process in all aspects. Its energy consumption and carbon footprint are 60.8 and 68.34% lower than case 1, respectively. Its capital and production costs are also the lowest, 37.0 and 9.88% lower than case 1.

Co-production bioethanol and xylooligosaccharides from sugarcane bagasse via autohydrolysis pretreatment

Autohydrolysis pretreatment is an effective, commercial and environmentally friendly processes for the co-production of bioethanol and xylooligosaccharides (XOS) from sugarcane bagasse (SCB). An XOS yield of 50.53% was obtained at 200 °C for 10 min by autohydrolysis pretreatment, most of cellulose and lignin remained in the solid residues, which can be converted into bioethanol. The ethanol yield (66.67%) in sodium acetate buffer solution (SAAB, pH 5.5) system was higher than that in the deionized water (DW) system (51.88%), because the stable pH regulated by the buffer was beneficial to maintain the cellulase and yeast activity. Moreover, the addition of non-ionic surfactants can effectively promote fermentation performances, especially with Tween 80, 82.28% ethanol yield (of the theoretical) was reached. The use of the buffer system and non-ionic surfactants provides an ideal strategy for ethanol production by fermentation of substrates with high lignin content. Therefore, this study shows a suitable and sustainable process for bioethanol and XOS production from SCB using autohydrolysis pretreatment as one-step of a biorefinery. • Autohydrolysis was an economical and feasible pretreatment method. • Bioethanol and XOS were co-produced from SCB via autohydrolysis pretreatment. • Buffer system was used for bioethanol production with high-lignin substrates. • Non-ionic surfactants can greatly increase fermentation performances. • 82.28% ethanol was produced from substrates with high lignin content.

Carbon-Efficient Production Scheduling of a Bioethanol Plant Considering Diversified Feedstock Pelletization Density: A Case Study

This paper presents a dual-objective optimization model for production scheduling of bioethanol plant with carbon-efficient strategies. The model is developed throughout the bioethanol production process. Firstly, the production planning and scheduling of the bioethanol plant’s transportation, storage, pretreatment, and ethanol manufacturing are fully considered. Secondly, the carbon emissions in the ethanol manufacturing process are integrated into the model to form a dual-objective optimization model that simultaneously optimizes the production plan and carbon emissions. The effects of different biomass raw materials with optional pelletization density and pretreatment methods on production scheduling are analyzed. The influence of demand and pretreatment cost on selecting a pretreatment method and total profit is considered. A membership weighted method is developed to solve the dual-objective model. The carbon emission model and economic model are integrated into one model for analysis. An example is given to verify the effectiveness of the optimization model. At the end of the paper, the limitation of this study is discussed to provide directions for future research.

Environmental management and valorization of cultivated tobacco stalks by combined pretreatment for potential bioethanol production

Expanding concern over exhausting fossil fuel and nursery gas limits must lead the more intrigued in renewable fuel-making from biomass sources counting sugars, starches, and lignocellulosic materials. Cultivated tobacco stalk is one of the massive amounts of available biorefinery wastes. Therefore, tobacco stalk was used for bioethanol production in this study. It contains abundant chemical compounds including cellulose, hemicellulose, and lignin 35.45 ± 0.13(%), 43.90 ± 0.26 (%), and 18.16 ± 0.28 (%), respectively. The total and reducing sugar utilizing phenol-sulfuric and DNS methods were carried out before and after the bioethanol fermentation process. Also, the combined pretreatment process was used for the degradation of the biomass and better accessibility to available sugars to increase the bioethanol production. Hydrolysate with the highest sugar concentration was selected and proceeded to bioethanol fermentation for 72 h. From the experimental results obtained, the total and reducing sugar concentration of tobacco stalk was 27.97 g/L and 5.43 g/L, individually. The results revealed the highest ethanol yields 75.74 (g/L) was reached at 48 h fermentation. Consequently, this form of combined pretreatment technique is a promising method of increasing the overall yield in the dried tobacco stalks to the bioethanol production process.

Process maps with metabolic constraints for bioethanol production by continuous fermentation

This paper presents a method of preparing process maps for the bioethanol production process by continuous fermentation. The proposed method of process map construction is based on the nonlinear analysis of bioreactor steady states and the metabolic interpretation method of the steady state branches. The nonlinear analysis of bioreactor steady states was performed relative to the dilution rate and the mass recirculation coefficient. It revealed the presence of nonlinear phenomena in the system, such as Hopf bifurcation points and limit points. The use of the qualitative interpretation method of bifurcation diagrams allowed the detection of metabolic change points and multiple steady state areas in which the metabolic activity of biomass cells undergoes changes. Taking this information into account together with the determined gradient profile of bioethanol concentrations has made it possible to construct a process map with metabolic constraints.

Perennial Grasses as a Substrate for Bioethanol Production

Abstract One of the possible choices as a biomass for lignocellulosic bioethanol production are different perennial grasses. Cultivating this type of biomass has many advantages in terms of natural diversity and landscape protection. In this study, mixture of red clover and timothy grass was used as a feedstock to investigate its potential as a substrate for bioethanol production. Traditional three step bioethanol production process was used in combination with NED pretreatment. The results show at all pretreatment temperatures similar glucose concentrations and hydrolysis efficiencies, which varied from 4.3 to 5.1 g/l and 15.2 % to 17.7 %, respectively. The ethanol yield, on the other hand, decreased as the pretreatment temperature increased. However, the mass balance revealed that when using this kind of feedstock, 3.3-4.0 g ethanol could be produced from 100 g of biomass. The overall efficiency and yield of the process was lower than expected due to pretreatment, which might not have been suitable for soft biomass.

Closed-loop dynamic real-time optimization (CL-DRTO) of a bioethanol distillation process using an advanced multilayer control architecture

The ethanol production has become an important part of the worldwide economy driven by its use as renewable energy and environmentally clean fuel. To obtain a high-level quality product, a large quantity of energy is used in the distillation stage. This work proposes to optimize the bioethanol production process applying a closed-loop dynamic real-time optimization (CL-DRTO) framework associated with advanced control strategies in the ethanol distillation facilities to improve production and minimize energy losses. A high-fidelity computational platform is developed using a software-in-the-loop (SIL) technique to demonstrate the feasible application in real cases. OLE (Object Linking and Embedding) Automation integrates Matlab and Aspen Hysys software to simulate practical scenarios currently applied in the industry. The optimization and control algorithms are developed in Matlab and the ethanol distillation process is modeled in the Aspen Hysys. Different advanced control strategies, such as IHMPC (Infinite Horizon Model Predictive Control), MIMO FSP (Filtered Smith-Predictor) and DTCGPC (Dead-Time Compensator Generalized Predictive Controller), are used to overcome the process dynamic issues, for instance, strong nonlinearity, dead-times, long time constants and coupled loops, on ethanol distillation process. A CL-DRTO layer is developed in the proposed control structure to consider economic and production aspects, guiding the process to optimal operating points. Performance indices and computational effort are used to evaluate the control behavior for disturbance rejection and reference tracking scenarios. Furthermore, economic performance is analyzed to ensure the advantages of the proposal. Results show that the proposed computational platform is able to reproduce industrial scenarios with high-fidelity. In addition, preliminary results demonstrate that advanced control structure can improve the production and profitability of the bioethanol distillery and present a powerful alternative to replace classical controllers currently used in this type of industry.

Proses Optimasi Produksi Bioetanol dari Limbah Serat Buah Sawit dengan Metode SHF

The Indonesian government is trying to equalize development including the energy sector. The government launched the use of alternative energy starting in 2008 with a blueprint for searching and utilizing new renewable energy sources in Indonesia through biofuels, one of the alternative energy developed is bioethanol. The research objective is the optimization of the SHF method bioethanol production process from palm fruit fiber waste.
 The experimental design uses central composite design with variable H2SO4 concentration and fermentation time. The first stage in the study was by saccharifying the palm oil fiber waste by the hydrolysis method using H2SO4 (concentrations of 1 M, 2 M, and 3 M). Then the next stage is fermentation process (fermentation time is 1 day, 2 days, 3 days, 4 days and 5 days). Sugar content analysis was carried out in the fermen solution and analysis of bioethanol levels in each running experiment. Then the optimization is done with the response surface method (RSM).
 Based on the research, the optimum condition of the bioethanol production process is H2SO4 concentration of 2.76 M with a fermentation time of 4.64 days which will produce bioethanol levels of 28.6027 g/L.

Survey of microbes in industrial-scale second-generation bioethanol production for better process knowledge and operation.

The microbes present in bioethanol production processes have been previously studied in laboratory-scale experiments, but there is a lack of information on full-scale industrial processes. In this study, the microbial communities of three industrial bioethanol production processes were characterized using several methods. The samples originated from second-generation bioethanol plants that produce fuel ethanol from biowaste, food industry side streams, or sawdust. Amplicon sequencing targeting bacteria, archaea, and fungi was used to explore the microbes present in biofuel production and anaerobic digestion of wastewater and sludge. Biofilm-forming lactic acid bacteria and wild yeasts were identified in fermentation samples of a full-scale plant that uses biowaste as feedstock. During the 20-month monitoring period, the anaerobic digester adapted to the bioethanol process waste with a shift in methanogen profile indicating acclimatization to high concentrations of ammonia. Amplicon sequencing does not specifically target living microbes. The same is true for indirect parameters, such as low pH, metabolites, or genes of lactic acid bacteria. Since rapid identification of living microbes would be indispensable for process management, a commercial method was tested that detects them by measuring the rRNA of selected microbial groups. Small-scale testing indicated that the method gives results comparable with plate counts and microscopic counting, especially for bacterial quantification. The applicability of the method was verified in an industrial bioethanol plant, inspecting the clean-in-place process quality and detecting viability during yeast separation. The results supported it as a fast and promising tool for monitoring microbes throughout industrial bioethanol processes.

Optimization of the enzymatic hydrolysis of cellulose of triplochiton scleroxylon sawdust in view of the production of bioethanol

The objective of the work is to optimize the enzymatic hydrolysis step in the production process of bioethanol based on sawdust. For this purpose, sawdust from Ayous (Triplochiton scleroxylon) was sampled and characterized. After pre-treatment with the organosovl method, a composite experimental design centred on three factors (substrate loading, enzyme loading and hydrolysis time) was used to study their effects on the release of reducing sugars during hydrolysis. The d-glucose monomers obtained were fermented and the product was distilled. The results obtained reveal that the pretreated Ayous sawdust contains a cellulose content of 53.2 ± 0.3%. At the end of the enzymatic hydrolysis, an increase in the enzyme loading and the hydrolysis time were recorded, followed by a decrease in the substrate loading thus contributing to a better hydrolysis yield of the celluloses. A loading of 9.07% in substrate associated with a loading of 21.36 FPU/gDM of enzyme for 72 hrs constituted the optimal conditions allowing the release of the maximum of reducing sugars and an optimal yield of hydrolysis of celluloses. The optimum values of the reducing sugars and the conversion yield are 21.88 mg/ml and 69%. The yield of Gay - Lussac obtained is 38 g/g. All this shows that it is possible to produce bioethanol from white sawdust.

English

In the last decade, bioethanol has become a powerful biofuel for the improvement of environmental pollution such as reduction in greenhouse gas levels. Yet, the source and type of substrate material plays a crucial role in the bioethanol production process due to the different compositional characteristics and availability of monomeric sugars. Different substrates of first, second and third generation fuel sources exist and may be used as reliable and sustainable substrates for bioethanol generation. The current review provides an overview of Vitellaria fruit pulp; its composition and characteristics for ethanol production. This study has examined literature on the background of the Vitellaria paradoxa, the characteristics and the potential of the shea nut pulp for fermentation to bioethanol. This review will be useful in harnessing the potentials of the shea pulp as industrially relevant substrate for use independently or in combination with other substrates in microbial fermentation processes for ethanol production.   Key words: Vitellaria, shea nut pulp, fermentation, composition, characterization, bioethanol.

Pseudonocardia filamentous bulking sludge in an industrial wastewater treatment plant as revealed by Illumina amplicon sequencing

In this study, 16S rRNA gene amplicon sequencing was performed to identify bulking filamentous bacteria in an industrial wastewater treatment plant that threats effluents of bioethanol production process from cereal cooking. The presence of Pseudonocardia sp. was confirmed by comparing the 16SrRNA of the most abundantly amplified sequence (OTU; 12.35%) with corresponding nucleotides present in two genomic databases. The Pseudonocardia species identified was closely related to Pseudonocardia spinosa. Over 50 different types of filamentous microorganisms have been found to cause problems with bulking and foaming, but Pseudonocardia has, until now, not been described to be among them. In addition, the 16S rRNA dataset was analyzed to reveal bacterial community composition during sludge bulking. Candidatus Competibacter was identified as the second most abundant sequence (OTU, 10.04%). Comparative data from samples obtained before and after appearance of Pseudonocardia suggest that a decrease in nutrients could be one of the main factors affecting sludge bulking generated by this species. The outcomes of this study are expected to provide an important insight into the role of Pseudonocardia in bulking in industrial wastewater treatment plants.

Dynamic bifurcations in continuous process of bioethanol production under aerobic conditions using Saccharomyces cerevisiae

This article presents a numerical study of the oscillatory phenomena occurring in the bioethanol production process by aerobic continuous fermentation using Saccharomyces cerevisiae. The growth of biomass cells is described by a structured and nonsegregated kinetic model. In the first stage of the research, a sensitivity analysis and bifurcation analysis of the mathematical model describing the process was made. As bifurcation parameters, the concentration of glucose in the feed stream and the dilution rate were used. The analysis exposed the presence of subcritical and supercritical Hopf bifurcation points and period-doubling bifurcation points. Areas of stable and unstable limit cycles were also detected. In the second stage, the dynamics of the system in these areas was investigated. The prepared Feigenbaum diagrams have revealed opulent dynamics in the areas of oscillatory behaviours along with chaotic phenomena. A method of qualitative interpretation of limit cycles based on the analysis of the rate profiles of dominant metabolic pathways has also been proposed. With its help it is possible to precisely determine the metabolic state of biomass cells in the areas of oscillatory solutions and to specify the nature of the generated oscillations. The performed analysis provides important information about the oscillating phenomena occurring in the bioethanol production process, and its results can be used in the design, optimization and synthesis of modern control systems.

Evolution of the Lignin Chemical Structure during the Bioethanol Production Process and Its Inhibition to Enzymatic Hydrolysis

To illuminate the lignin evolution after hydrogen peroxide presoaking prior to ammonia fiber expansion pretreatment (H-AFEX) pretreatment and enzymatic hydrolysis, ball-milled wood lignins were sep...

High-solids enzymatic hydrolysis of ball-milled corn stover with reduced slurry viscosity and improved sugar yields

BackgroundHigh-solids enzymatic hydrolysis has attracted increasing attentions for the production of bioethanol from lignocellulosic biomass with its advantages of high product concentration, water saving, and low energy and capital costs. However, the increase of solids content would worsen the rheological properties, resulting in heat/mass transfer limitation and higher mixing energy. To address these issues, ball milling was applied to corn stover prior to enzymatic hydrolysis, and the rheological behaviors and digestibility of ball-milled corn stover under high-solids loading were investigated.ResultsBall milling significantly modified the physicochemical properties of corn stover. The apparent viscosity of slurries at 30% solid loading decreased by a factor of 500 after milling for 60 min, and the yield stress was less than 10 Pa. The dramatic decrease of viscosity and yield stress enabled the hydrolysis process to be conducted in shake flask, and remained good mixing. Meanwhile, the estimated energy consumption for mixing during saccharification decreased by 400-fold compared to the untreated one. The resultant hydrolysate using 10 FPU g−1 solids was determined to contain 130.5 g L−1 fermentable sugar, and no fermentation inhibitors were detected.ConclusionsThe proposed ball milling pretreatment improved rheological behavior and sugar yield of high-solids corn stover slurry. Ball milling enables high-solids slurry to maintain low viscosity and yield stress while obtaining a non-toxic high-concentration fermentable syrup, which is undoubtedly of great significance for inter-unit processing, mixing and downstream process. In addition, the energy input for ball milling could be balanced by the reduced mixing energy. Our study indicates ball milling a promising pretreatment process for industrial bioethanol production.

Acoustic-Based Screening Method for the Detection of Total Aflatoxin in Corn and Biological Detoxification in Bioethanol Production.

Aspergillus spp. are widely occurring fungi in nature; they produce toxic compounds such as aflatoxins (AFs) and mainly target plant products such as corn and nuts. The development of prevention strategies is challenging because AFs are highly toxic and have been regulated to small concentrations. This study proposes a new strategy of AF prevention through the application of rapid methods using acoustic techniques in combination with fermentation for the elimination of contaminated corn from bioethanol production processes. An acoustic device was used for the analysis of model systems consisting of corn and nuts (hazelnuts and peanuts) contaminated with different amounts of AFs. High correlations were obtained between penetrated acoustic signal amplitude (Ap) and corn sample density, and between Ap and AF content. Also, relationships were found between changes in Ap values and AF contamination in the nuts model systems. The results of biotreatment of contaminated corn during bioethanol production confirmed that AFs cannot be completely eliminated in dried distiller’s grains with solubles, a valuable by-product for animal feed. Microbially, contamination of the raw material has a negative impact on bioethanol quality by increasing the content of volatile compounds. Therefore, the application of methods such as acoustic screening is a promising alternative for rapid AF detection in corn and nuts (it can handle multi-layers of grain). With the application of acoustic techniques, the prevention of AFs in contaminated raw plant materials could be achieved.

A study of the effect of calcium chloride (CaCl2) and pH on the flocculation ability of Saccharomyces cerevisiae (NCYC 1195)

The best fermentation ability of yeast-forming flock species is highly desirable in the bioethanol production process. Saccharomyces cerevisiae NCYC 1195 is known to have the ability to form flock which is influenced by the concentration of calcium chloride (CaCl2) and pH. This is because calcium ions can form bonds with mannose on the surface of the cell wall of S. cerevisiae, while the degree of acidity will affect the charges of specific protein on the cell wall. The ability of flocculation will precipitate S. cerevisiae cells so that they will not be mixed with fermentation medium. Thus, the separation process of cell and fermentation media can be done quickly and efficiently, without expensive centrifugation step. The aim of this study was to determine the effect of CaCl2 concentration and pH that used to determine the ability and stability of the flock of S. cerevisiae. Three concentration of CaCl2 (10-5, 10-7, 10-9 M) were used as well as three variations of pH (4,5,6). Culture was incubated at 30°C with 100 rpm agitation and analysed for flocculation ability every 4 hours during 24 hours. The stability of the flock was analysed every 24 hours during 30 days. The highest flock formation ability (73.15%) was obtained with the concentration of CaCl2 concentration 10-9 M and pH 5.

Intensification of the 2g Bioethanol Production Process

The main objective of the present study is to propose a methodology to evaluate alternatives for the synthesis of the second-generation bioethanol production process from lignocellulosic feedstock, in order to reduce amount of waste, energy consumption and production costs. The methodology is based on modelling, synthesis, design and simulation, where the heat integration in the 2G bioethanol production process is a key tool to evaluate the process in technical, economic and environmental terms. As a case study, wheat straw is considered as raw material, and the simulations are performed using a modular process simulator. For the assessment and comparison of the biorefinery alternatives, the selected evaluation criteria are ethanol yield, unit production cost, energy consumption, CO2 emissions and water consumption. The results show the best process alternatives that can lead to greater sustainable ethanol production, supporting better decision making in the synthesis and design of biorefineries.

Bioethanol Production Using Microalgae

Objectives:Bioethanol is known as an important energy source that comes from plants, uses existing energy infrastructure without additional investment, and emits a low concentration of pollutants during combustion as eco-friendly renewable energy. Microalgae is reported as an effective material for producing bioethanol because of rapid biomass growth and relatively easy pretreatment steps. The objectives of this study are 1) to introduce general information of bioethanol production, 2) to show various processes for bioethanol production from microalgae, and 3) to provide an economic perspective of bioethanol. Methods:Recent published peer-reviewed papers were collected and analyzed. The contents follow the order: 1) introduction, 2) general information about microalgae for bioethanol production, 3) bioethanol producing processes, 4) economic feasibility, and 5) conclusion.Results and Discussion:The selection of the microalgae species and growing method are important to obtain high yield bioethanol. Physical, chemical, biological pretreatment was introduced. Also, comparison of the bioethanol producing processes was provided. Conclusions:Bioethanol production from microalgae is a promising energy source because microalgae have lots of advantages as effective biomass such as rapid growth, high polysaccharide contents, and easy preparing step for bioethanol production. However, it has some limitations that need to overcome. Algae growing method, pretreatment technology, and fermentation steps still require advanced technology, which can improve economic feasibility.

Analysis of Ethanol Dehydration using Membrane Separation Processes.

After the biomass pretreatment and fermentation processes, the purification step constitutes a major task in bioethanol production processes. The use of membranes provides an interesting choice to achieve high-purity bioethanol. Membrane separation processes are generally characterized by low energy requirements, but a high capital investment. Some major design aspects for membrane processes and their application to the ethanol dehydration problem are addressed in this work. The analysis includes pervaporation and vapor permeation methods, and considers using two types of membranes, A-type zeolite and amorphous silica membrane. The results identify the best combination of membrane separation method and type of membrane needed for bioethanol purification.