Production Of Fuel-grade Ethanol Research Articles

Process simulation and techno-economic assessment for direct production of advanced bioethanol using a genetically modified Synechocystis sp.

A techno-economic assessment for the direct production of ethanol using a genetically-modified microalgae has been studied. It was considered two main scenarios for process modelling: i) bioenergy-driven microalgae plant, i.e., focused on the production of fuel-grade ethanol and biogas for CHP and, ii) biorefinery-driven microalgae plant, focused on the recovery of added-value bioproducts (zeaxanthin and phycocyanin) along with ethanol and CHP production. These main scenarios and several variants were modelled and optimized for a small-scale demo plant of 1000 Lethanol/day and extrapolated for larger production capacities. Results showed that despite the innovative approach of direct production of ethanol by microalgae, the bioenergy-driven scenario is non-feasible under the studied conditions. Conversely, ethanol production becomes economically feasible as co-product in the biorefinery-driven scenario although having payback periods >10 years. Furthermore, if only bio-based products are produced the NPV and the payback are even more positive, 104.8 M€ and ca. 5 years, respectively.

Performance of Different Inert Gases in Production of Fuel Grade Ethanol by Diffusion Distillation

Performance of sulfur hexafluoride, nitrogen, argon, and helium inert gases was investigated in a view to produce fuel grade ethanol by diffusion distillation. Stefan–Maxwell equations based mathematical model was used for this study. Modeling results were also compared with the own experimental data. Shifting of azeotrope to different extents was observed by using different inert gases as selective filter. As the selected inert gas becomes lighter, narrow concentration range for positive selectivity was found. Sulfur hexafluoride was found to be the most suitable inert gas for ethanol dehydration by diffusion distillation, and quantity $${{S}_{{{\text{az}}}}}({{N{}_{2}} \mathord{\left/ {\vphantom {{N{}_{2}} {{{N}_{1}}}}} \right. \kern-0em} {{{N}_{1}}}})$$ , which represents the overall performance of any inert gas, was also found to be highest for this gas out of all the inert gases studied. Sulfur hexafluoride gas also allows to work at high vaporization temperature, which facilitates the high transfer efficiency. If light gases are to be used they should be used for high feed concentrations and at low vaporization temperatures to achieve the high degree of separation.

Recent Advances on Bioethanol Dehydration using Zeolite Membrane

Renewable energy has gained increasing attention throughout the world. Bioethanol has the potential to replace existing fossil fuel usage without much modification in existing facilities. Bioethanol which generally produced from fermentation route produces low ethanol concentration. However, fuel grade ethanol requires low water content to avoid engine stall. Dehydration process has been increasingly important in fuel grade ethanol production. Among all dehydration processes, pervaporation is considered as the most promising technology. Zeolite possesses high potential in pervaporation of bioethanol into fuel grade ethanol. Zeolite membrane can either remove organic (ethanol) from aqueous mixture or water from the mixture, depending on the framework used. Hydrophilic zeolite membrane, e.g. LTA, can easily remove water from the mixture leaving high ethanol concentration. On the other hand, hydrophobic zeolite membrane, e.g. silicate-1, can remove ethanol from aqueous solution. This review presents the concept of bioethanol dehydration using zeolite membrane. Special attention is given to the performance of selected pathway related to framework selection.

Techniques for the Evolution of Robust Pentose-fermenting Yeast for Bioconversion of Lignocellulose to Ethanol.

Lignocellulosic biomass is an abundant, renewable feedstock useful for production of fuel-grade ethanol and other bio-products. Pretreatment and enzyme saccharification processes release sugars that can be fermented by yeast. Traditional industrial yeasts do not ferment xylose (comprising up to 40% of plant sugars) and are not able to function in concentrated hydrolyzates. Concentrated hydrolyzates are needed to support economical ethanol recovery, but they are laden with toxic byproducts generated during pretreatment. While detoxification methods can render hydrolyzates fermentable, they are costly and generate waste disposal liabilities. Here, adaptive evolution and isolation techniques are described and demonstrated to yield derivatives of the native Scheffersomyces stipitis strain NRRL Y-7124 that are able to efficiently convert hydrolyzates to economically recoverable ethanol despite adverse culture conditions. Improved individuals are enriched in an evolving population using multiple selection pressures reliant on natural genetic diversity of the S. stipitis population and mutations induced by exposures to two diverse hydrolyzates, ethanol or UV radiation. Final evolution cultures are dilution plated to harvest predominant isolates, while intermediate populations, frozen in glycerol at various stages of evolution, are enriched on selective media using appropriate stress gradients to recover most promising isolates through dilution plating. Isolates are screened on various hydrolyzate types and ranked using a novel procedure involving dimensionless relative performance index (RPI) transformations of the xylose uptake rate and ethanol yield data. Using the RPI statistical parameter, an overall relative performance average is calculated to rank isolates based on multiple factors, including culture conditions (varying in nutrients and inhibitors) and kinetic characteristics. Through application of these techniques, derivatives of the parent strain had the following improved features in enzyme saccharified hydrolyzates at pH 5-6: reduced initial lag phase preceding growth, reduced diauxic lag during glucose-xylose transition, significantly enhanced fermentation rates, improved ethanol tolerance and accumulation to 40 g/L.

Evolved strains of Scheffersomyces stipitis achieving high ethanol productivity on acid- and base-pretreated biomass hydrolyzate at high solids loading.

BackgroundLignocellulosic biomass is an abundant, renewable feedstock useful for the production of fuel-grade ethanol via the processing steps of pretreatment, enzyme hydrolysis, and microbial fermentation. Traditional industrial yeasts do not ferment xylose and are not able to grow, survive, or ferment in concentrated hydrolyzates that contain enough sugar to support economical ethanol recovery since they are laden with toxic byproducts generated during pretreatment.ResultsRepetitive culturing in two types of concentrated hydrolyzates was applied along with ethanol-challenged xylose-fed continuous culture to force targeted evolution of the native pentose fermenting yeast Scheffersomyces (Pichia) stipitis strain NRRL Y-7124 maintained in the ARS Culture Collection, Peoria, IL. Isolates collected from various enriched populations were screened and ranked based on relative xylose uptake rate and ethanol yield. Ranking on hydrolyzates with and without nutritional supplementation was used to identify those isolates with best performance across diverse conditions.ConclusionsRobust S. stipitis strains adapted to perform very well in enzyme hydrolyzates of high solids loading ammonia fiber expansion-pretreated corn stover (18% weight per volume solids) and dilute sulfuric acid-pretreated switchgrass (20% w/v solids) were obtained. Improved features include reduced initial lag phase preceding growth, significantly enhanced fermentation rates, improved ethanol tolerance and yield, reduced diauxic lag during glucose-xylose transition, and ability to accumulate >40 g/L ethanol in <167 h when fermenting hydrolyzate at low initial cell density of 0.5 absorbance units and pH 5 to 6.

Simultaneous Optimal Design and Control of an Extractive Distillation System for the Production of Fuel Grade Ethanol Using a Mathematical Program with Complementarity Constraints

The simultaneous optimal design and control problem of an extractive distillation system is studied using a rigorous model and solved when the feed is subjected to composition disturbances. First, the problem is formulated as a mixed-integer dynamic optimization (MIDO) problem, and then transformed into a mathematical program with complementarity constraints (MPCC) problem using orthogonal collocation on finite elements. The model allows simultaneous determination of the number of trays, feed tray locations, structural parameters of the column, heat exchanger areas, set points of both the controlled and manipulated variables, and the optimal control policy in order to obtain an optimal design which maximizes profit and also guarantees feasible dynamic operation. The study also demonstrates how the distillation column design problem can be addressed as a MPCC problem instead of as a mixed-integer nonlinear programming (MINLP) problem, containing thousands of continuous variables and constraints, and how can it be solved in reasonable times using state-of-the-art algorithms. The problem is modeled in GAMS and solved using IPOPT. Finally, results obtained by the simultaneous strategy are compared to those obtained by addressing the design and control problem sequentially.

Optimal Control of the Extractive Distillation for the Production of Fuel-Grade Ethanol

Laboratoire de Thermique, Energetique et Proce de s (LaTEP), E cole Nationale Supe rieure en Ge nie de Technologies Industrielles(ENSGTI), Universitedes Pays de l’Adour (UPPA), Rue Jules Ferry, BP 7511, 64 075 PAU Cedex, FranceABSTRACT: The extractive distillation of ethanol using glycerol as the entrainer was studied to determine its optimal controlprofiles when the azeotropic feed was subjected to composition disturbances. The process was modeled by a differential-algebraicequation (DAE) system that represents the dynamics of the equilibrium stages in the extraction column. The model equationswere solved by discretizing the time domain using orthogonal collocation on finite elements. Initially, the effects of feeddisturbances on the product flow rate and quality were analyzed. Subsequently, a profit objective function was formulated, andthe optimal profiles of the manipulated variables (reflux ratio and reboiler duty) were determined, subject to quality constraints.The solution was obtained by solving the nonlinear programming (NLP) problem that resulted from the discretization. Theproblem was solved in GAMS using IPOPT as the nonlinear solver, testing two different linear solvers, the Harwell subroutinesMA57 and MA86. The optimal control strategy was compared to a simple PI control scheme.

Ethanol concentration by forward osmosis with solar-regenerated draw solution

Production of fuel-grade ethanol requires removing excess water following fermentation, which is typically performed by an energy intensive distillation process. This paper proposes a simple, low-cost, and scalable alternative method of removing water using forward osmosis. The draw solution is an aqueous brine that is regenerated by solar evaporation. Separation limits of this approach are calculated using the van Laar equation for the non-ideality of the ethanol/water mixture, and experimentally measured activities for aqueous solutions of NaCl, CaCl2, K2HPO4, and K4P2O7. We focus on production of 95%, 50% and 30% (w/w) ethanol solutions as fuel for cooking stoves and homogeneous charge compression ignition (HCCI) engines, both of which tolerate larger amounts of water in the product. Evaporation-limited production rates are computed using long-term meteorological data for sites in Ethiopia, Thailand, Brazil, and India. These calculations can be used to determine the size requirements necessary for a given daily production rate for any desired ethanol concentration.

Modeling the Regeneration of a Polymeric Resin Column Saturated with Ethanol by Air Purge and External Heating

In this work, the regeneration of a polymeric resin column saturated with ethanol with air purge and external heating has been studied. A theoretical model is proposed for describing the mass and heat transfers in the system, and it has been validated with experimental data. This model can be used for simulating the regeneration step in a concentration-thermal swing adsorption process for fuel-grade ethanol production. The model has been used to analyze the process dynamic behavior, and to compare the performance of the regeneration step using external heating and hot air purge.

Optimization of the Design and Operation of an Extractive Distillation System for the Production of Fuel Grade Ethanol Using Glycerol as Entrainer

The extractive distillation of ethanol using glycerol as entrainer is studied in order to find its optimal design and operating conditions. The optimization is formulated as a mixed integer nonlinear programming (MINLP) problem. The discrete variables determine the number of stages of the columns and their feed stage locations. The continuous variables include the variables of the equilibrium model and operating variables. The solution of the optimization problem is achieved through a two-level strategy that combines stochastic and deterministic algorithms. The result obtained establishes the process that maximizes an economic criterion for the industrial production of bioethanol satisfying the problem constraints.

Modelling the Desorption of Ethanol from an Externally Heated Saturated Activated Carbon Column by Purging with Air

The desorption of ethanol from an externally heated column loaded with activated carbon and purged with air has been studied. The column was initially saturated with liquid ethanol. This process simulates the regeneration step in a concentration-swing/thermal-swing adsorption process for the production of fuel-grade ethanol. A theoretical model was developed for describing the mass- and heat-transfer kinetics of the process. Validation of the model was achieved by comparing its predictions with experimental data, employing initial column temperatures between 298 K and 395 K and air flow rates between 1.6 × 10-6 m3/s and 11.3 × 10-6 m3/s. Experimentally measured adsorption isotherms of ethanol from ethanol/air gas mixtures onto activated carbon, as well as the regeneration column dynamics, are reported.

The commercial performance of cellulosic ethanol supply-chains in Europe

BackgroundThe production of fuel-grade ethanol from lignocellulosic biomass resources has the potential to increase biofuel production capacity whilst minimising the negative environmental impacts. These benefits will only be realised if lignocellulosic ethanol production can compete on price with conventional fossil fuels and if it can be produced commercially at scale. This paper focuses on lignocellulosic ethanol production in Europe. The hypothesis is that the eventual cost of production will be determined not only by the performance of the conversion process but by the performance of the entire supply-chain from feedstock production to consumption. To test this, a model for supply-chain cost comparison is developed, the components of representative ethanol supply-chains are described, the factors that are most important in determining the cost and profitability of ethanol production are identified, and a detailed sensitivity analysis is conducted.ResultsThe most important cost determinants are the cost of feedstocks, primarily determined by location and existing markets, and the value obtained for ethanol, primarily determined by the oil price and policy incentives. Both of these factors are highly uncertain. The best performing chains (ethanol produced from softwood and sold as a low percentage blend with gasoline) could ultimately be cost competitive with gasoline without requiring subsidy, but production from straw would generally be less competitive.ConclusionSupply-chain design will play a critical role in determining commercial viability. The importance of feedstock supply highlights the need for location-specific assessments of feedstock availability and price. Similarly, the role of subsidies and policy incentives in creating and sustaining the ethanol market highlights the importance of political engagement and the need to include political risks in investment appraisal. For the supply-chains described here, and with the cost and market parameters selected, selling ethanol as a low percentage blend with gasoline will maximise ethanol revenues and minimise the need for subsidies. It follows, therefore, that the market for low percentage blends should be saturated before markets for high percentage blends.

High permeability membranes for the dehydration of low water content ethanol by pervaporation

Energy efficient dehydration of low water content ethanol is a challenge for the sustainable production of fuel-grade ethanol. Pervaporative membrane dehydration using a recently developed hydrophilic polymer membrane formulation consisting of a cross-linked mixture of poly(allylamine hydrochloride) and a blend of 99 and 88% hydrolyzed poly(vinyl alcohol) is found to be an attractive method. These polymeric membranes possess high water permeabilities at low feed water concentrations (<5 wt%) in ethanol compared to similar membranes in which all of the poly(vinyl alcohol) portion was 99% hydrolyzed.

Ethanol Production from Sweet Sorghum Syrup for Utilization as Automotive Fuel in India

Ethanol demand is increasing drastically in the present time due to its blending in automotive fuels, which is desirable for getting clean exhaust and fuel sufficiency. The higher cost of cultivation of sugarcane/-beets, highly sensitive molasses rates, and ultimately instabilities in the price of ethanol have created grounds to search for an alternative source for ethanol production. Sweet sorghum has shown potential as a raw material for fuel-grade ethanol production due to its rapid growth rate and early maturity, greater water use efficiency, limited fertilizer requirement, high total value, and wide adoptability. Ethanol-producing companies, research institutions, and governments can coordinate with farmers to strategically develop value-added utilization of sweet sorghum. Fuel-grade ethanol production from sweet sorghum syrup can significantly reduce India's dependence on foreign oil and also minimize the environmental threat caused by fossil fuels.

Process Design and Optimization of Novel Wheat‐Based Continuous Bioethanol Production System

A novel design of a wheat-based biorefinery for bioethanol production, including wheat milling, gluten extraction as byproduct, fungal submerged fermentation for enzyme production, starch hydrolysis, fungal biomass autolysis for nutrient regeneration, yeast fermentation with recycling integrated with a pervaporation membrane for ethanol concentration, and fuel-grade ethanol purification by pressure swing distillation (PSD), was optimized in continuous mode using the equation-based software General Algebraic Modelling System (GAMS). The novel wheat biorefining strategy could result in a production cost within the range of dollars 0.96-0.50 gal(-1) ethanol (dollars 0.25-0.13 L(-1) ethanol) when the production capacity of the plant is within the range of 10-33.5 million gal y(-1) (37.85-126.8 million L y(-1)). The production of value-added byproducts (e.g., bran-rich pearlings, gluten, pure yeast cells) was identified as a crucial factor for improving the economics of fuel ethanol production from wheat. Integration of yeast fermentation with pervaporation membrane could result in the concentration of ethanol in the fermentation outlet stream (up to 40 mol %). The application of a PSD system that consisted of a low-pressure and a high-pressure column and employing heat integration between the high- and low-pressure columns resulted in reduced operating cost (up to 44%) for fuel-grade ethanol production.

Immobilization of yeast cells on various supports for ethanol production

An immobilization technique has been developed for a packed bed fermenter which is being considered as one stage of a process for the production of fuel-grade ethanol from sugar solutions. Relatively inexpensive beech wood chips have been successfully used as the support material and relatively high cell loadings of 188 mg DW cells/g DW support have been achieved for a test system of Saccharomyces cerevisiae cultures.