Biochemical Production Of Ethanol Research Articles

(Invited) Integrated Chemocatalytic Conversion of Cellulosic Biomass to Gasoline Blended Fuel Using a Multifunctional Nano-Catalysts

The Ministry of New and Renewable Energy (MNRE) in India has initiated several programs to promote effective ways of utilizing biomass energy to boost the country's economy. In order to improve the effective use of biomass resources, the initiative for biomass power and cogeneration has adopted the use of bagasse-based cogeneration and biomass power generation in sugar mills. Because of its remarkable characteristics, including its high-octane number, low cetane number, and significant heat of vaporization, bioethanol is considered as a desirable biofuel. In addition, the increased biofuel production, in particular bioethanol, satisfies the criteria of the energy demand. These criteria include the fuel's ability to be blended with gasoline and diesel, as well as standards for low-carbon fuels.Chemocatalytic conversion using nanowire catalysts reduce side reactions caused on by an intermediate product while facilitating cascade reactions that lead to a desired product. In this work, metal oxide nanowires (TiO2 and WO3) were synthesised using a plasma-assisted method and metal nanoparticles (Pt and Ru) were impregnated on the as-synthesised NWs. In a high-pressure slurry batch reactor, reactions were carried out to obtain the optimal conditions for the desired product. The catalysts were characterised to reveal the catalysts-activity relationship. Various analytical techniques were used to quantify the liquid and gaseous products collected after the reactions.The direct conversion of cellulose to C2-C3 alcohols using tungsten-based co-catalysts was enhanced even at low temperatures. X-ray photoelectrons spectroscopy (XPS) and Raman analysis show the oxygen vacancy (Ov) enrichment on the surface of Pt/TiO2 in presence of tungsten co-catalysts which improved their catalytic activity. The role of metallic platinum (Pto) was also investigated and found to have a linear relationship with the activity as follows: H2WO4 > (NH4)6H2W12O40.xH2O > H3PW12O40 . Maximum yields of 32.33% and 51.52% of ethanol and propane-2-ol at optimum temperatures of 220℃ and 250℃, respectively, were obtained with H2WO4. Catalytic reaction performed using tandem catalytic system gives a high ethanol yield of 25.56%, which is low as compared to an integrated catalytic system. Based on the experimental results, the reaction pathway is proposed which elaborates the activation and cleavage of specific C-C and C-O bonds.Moreover, the dual functionality of tungsten oxide (WO3) nanorods as support and co-catalyst was also studied, enhances the catalytic behaviour, and the promotional study of W was studied for delivering a high yield of ethanol to 43.98% under optimum reaction conditions. The cellulose conversion was calculated to be 98.5%. The XPS study reveals the oxidation state of WO3 employing the change in catalytic activity before and after the addition of co-catalysts. The electron-deficient state of the metallic component (Ruo) is favourable for H2 adsorption on the surface, producing more active hydrogen species and thus promoting hydrogenation. As a result of these electronic understandings of Ruo and W, the reason for the higher activity of these nano synthesised Ru/WO3 compared to WO3 was concluded. Furthermore, a series of characterizations were performed to reveal the catalysts-activity relationship. Our characterization and activity test suggested that the synergistic effect of W6+ and Ruo facilitate the formation of ethanol whereas, Bronsted acid sites from W-based catalysts and Bronsted base from hot compressed water (HCW) collectively participate in the hydrolysis of cellulose and C-C cleavage of glucose to ethanol via selective hydrogenolysis of C-OH. The bond functionality was also investigated by performing reactions with various reactants under the same reaction conditions. This presentation will provide our understanding of the mechanism and kinetic correlation of the integrated cellulose-to-ethanol synthesis important for sustainable ethanol production.Correspondence should be addressed to: sreedevi@chemical.iitd.ac.in. Acknowledgments The authors thankfully acknowledge funding support from TUD-IITD MFIRP project. References Governement of India of India, BioEnergy, Ministry of New and Renewable Energy. https://mnre.gov.in/bio-energy/current-status (accessed Dec. 27, 2023).S. Achinas and G. J. W. Euverink, Consolidated briefing of biochemical ethanol production from lignocellulosic biomass, Electron. J. Biotechnol., 2016, 23: 44–53Beena Patel and Bharat Gami, Biomass Characterization and its Use as Solid Fuel for Combustion, Iran. J. Energy Environ., Iranica Journal of Energy & Environment, 2012; 3 (2):123-128N. Wei, J. Quarterman, S. R. Kim, J. H. D. Cate, and Y. S. Jin, Enhanced biofuel production through coupled acetic acid and xylose consumption by engineered yeast, Nat. Commun., 2013; 4:1–8 Figure 1

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

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

Consolidated briefing of biochemical ethanol production from lignocellulosic biomass

Bioethanol production is one pathway for crude oil reduction and environmental compliance. Bioethanol can be used as fuel with significant characteristics like high octane number, low cetane number and high heat of vaporization. Its main drawbacks are the corrosiveness, low flame luminosity, lower vapor pressure, miscibility with water, and toxicity to ecosystems. One crucial problem with bioethanol fuel is the availability of raw materials. The supply of feedstocks for bioethanol production can vary season to season and depends on geographic locations. Lignocellulosic biomass, such as forest-based woody materials, agricultural residues and municipal waste, is prominent feedstock for bioethanol cause of its high availability and low cost, even though the commercial production has still not been established. In addition, the supply and the attentive use of microbes render the bioethanol production process highly peculiar. Many conversion technologies and techniques for biomass-based ethanol production are under development and expected to be demonstrated. In this work a technological analysis of the biochemical method that can be used to produce bioethanol is carried out and a review of current trends and issues is conducted.

Evaluating Lignin-Rich Residues from Biochemical Ethanol Production of Wheat Straw and Olive Tree Pruning by FTIR and 2D-NMR

Lignin-rich residues from the cellulose-based industry are traditionally incinerated for internal energy use. The future biorefineries that convert cellulosic biomass into biofuels will generate more lignin than necessary for internal energy use, and therefore value-added products from lignin could be produced. In this context, a good understanding of lignin is necessary prior to its valorization. The present study focused on the characterization of lignin-rich residues from biochemical ethanol production, including steam explosion, saccharification, and fermentation, of wheat straw and olive tree pruning. In addition to the composition and purity, the lignin structures (S/G ratio, interunit linkages) were investigated by spectroscopy techniques such as FTIR and 2D-NMR. Together with the high lignin content, both residues contained significant amounts of carbohydrates, mainly glucose and protein. Wheat straw lignin showed a very low S/G ratio associated withp-hydroxycinnamates (p-coumarate and ferulate), whereas a strong predominance of S over G units was observed for olive tree pruning lignin. The main interunit linkages present in both lignins wereβ-O-4′ethers followed by resinols and phenylcoumarans. These structural characteristics determine the use of these lignins in respect to their valorization.

Biofuel from Waste Agricultural product and Lignocellulosic Biomass

The conversion of biomass to ethanol is an attractive source of alternative green fuels. Current studies look at the thermochemical conversion of biomass to ethanol, but little focus is placed on the biochemical conversion pathway available for this transformation. We present two case studies depicting the potential of a biochemical production of ethanol for fuel purposes. The industrial scale plant design of corn stover conversion is addressed with the purpose of deriving a simple yet complete model for use in economic optimization of large scale supply chains. A lab scale kinetics study for the conversion of waste sweet potato to ethanol is also presented. These two case studies show the potential for research in the area of biochemical conversion of biomass to green fuels.

Dynamic Modeling and Parameter Estimation for Unit Operations in Lignocellulosic Bioethanol Production

During the past decades, intensive research has been pursued on the development of kinetic models to predict process behavior in ethanol production from lignocellulose. These models comprise a large number of parameters which have to be tuned with appropriate experimental data. Therefore, the parameter estimation problem plays an essential role. This work addresses the parameter estimation problem in models representing dilute acid hydrolysis, detoxification, and cofermentation operations in the biochemical production of ethanol from lignocellulosic biomass. The models are represented by sets of differential-algebraic equations (DAEs). Unlike previous approaches, these models account for the main process variables that affect the entire process, specially the final production of bioethanol. These detailed kinetic models, systematically tuned with experimental data, can be used in future studies within a model-based framework that allows performing realistic simulation and optimization aimed at bioethanol process design. A sensitivity analysis has been performed in order to identify the most sensitive parameters. The parameter estimation problem is solved with a simultaneous optimization approach in which the system of dynamic equations is converted into a set of algebraic ones through orthogonal collocation on finite elements. Thus, estimating the model parameters entails optimizing a weighted least squares objective function subject to the discretized algebraic constraints, resulting in a large-scale nonlinear programming problem (NLP). A good agreement with available experimental data has been obtained with estimated kinetic parameters in each model.

Biochemical production of ethanol and fatty acid ethyl esters from switchgrass: A comparative analysis of environmental and economic performance

As advances in biotechnology have continued at a rapid pace, interest in the biochemical production of so-called “drop-in” fuels has increased as a way to avoid the well-known shortcomings of ethanol as a fuel molecule and to potentially exploit the processing advantages of a water-immiscible fuel to reduce product recovery costs and energy requirements. In the current study, processes to produce either ethanol or a representative fatty acid ethyl ester (FAEE) via the fermentation of sugars liberated from lignocellulosic materials pretreated in acid or alkaline environments are analyzed in terms of economic and environmental metrics. Simplified process models are introduced and employed to estimate fuel production, greenhouse gas emissions, net energy consumption, minimum fuel selling price, and water consumption for both processes. Monte Carlo analyses were carried out to identify key sources of uncertainty and variability, and an analysis of the impact of potential improvements to the FAEE process was performed. We find that the near-term performance of processes to produce FAEE is significantly worse than that of ethanol production processes for all metrics considered, primarily due to poor fermentation yields and higher electricity demands for aerobic fermentation. Even if these issues are addressed in the longer term, the reduced cost and energy requirements of FAEE separation processes will be at least partially offset by inherent limitations in the relevant metabolic pathways that constrain the maximum yield potential of FAEE from biomass-derived sugars.

Heat integration of biochemical ethanol production from straw – A case study

Ethanol produced from lignocellulosic biomass is a desired, renewable fuel that can help to reduce our dependence on oil. In order to achieve the commercial deployment of this fuel good economic and environmental performance are mandatory. Both these targets are tackled by the efficient use of process heat. This work deals with the heat integration of the biochemical production of ethanol from straw. Process simulation and pinch analysis are applied to investigate a base case design of the production process. The energy intensive unit operations distillation and evaporation are in the focus of this pinch analysis. Pressure and heat load modifications of these sections are applied to improve the process design. For this improved process design a heat exchanger network is synthesized. Energy stream and pinch analysis revealed that process residues easily suffice to provide the investigated process with heat. The design modifications of the distillation and evaporation sections lead to increased heat integration. Consequently, a 15% reduction of the utility targets compared to the base case is obtained in the improved design. The heat exchanger network for the improved design is simple, yet the increase in utility consumption compared to the utility targets is quite modest. As a result, in the network only 51% of waste biomass suffice to provide the process with heat. The exceeding biomass can be used for the recovery of energy or material by-products, which highlights the need for efficient polygeneration concepts.

Greenhouse gas emissions from first generation ethanol derived from wheat and sugar beet in Germany – Analysis and comparison of advanced by-product utilization pathways

In state of the art ethanol production, by-products like vinasse from sugar beet or distiller’s dried grains with solubles (DDGSs) from wheat grains are usually used as animal feed. The drying process consumes a significant amount of energy that could be reduced by producing other valuable materials or energy carriers from these by-products. Besides resulting higher overall conversion rates and improved process efficiencies, by-products, which can be extracted or are automatically created during the various conversion steps, should be used to reduce environmental impacts as well. In this analysis, advanced pathways for the recovery and use of by-products from bio-chemical ethanol production like gluten separation from wheat starch, biogas production from stillage or vinasse and combustion of bran for electricity generation are analyzed with regard to their contribution to the greenhouse effect. Therefore, different methodological approaches are applied and compared. The analysis shows among others that ethanol from sugar beet generates less greenhouse gases (GHGs) compared to the ethanol production from wheat. The biogas production from residues and especially the use of bran for heat and electricity generation shows significant GHG reduction compared to the state of the art application. However, the methodological approach for the treatment of by-products highly influences the results. For the reproducibility of the results an energy equivalent allocation method involving the specific application of the respective co-product is recommended.

Alkaline sulfite/anthraquinone pretreatment followed by disk refining ofPinus radiataandPinus caribaeawood chips for biochemical ethanol production

AbstractBACKGROUND:Alkaline sulfite/anthraquinone (ASA) cooking ofPinus radiataandPinus caribaeawood chips followed by disk refining was used as a pretreatment for the production of low lignified and high fibrillated pulps. The pulps produced with different delignification degrees and refined at different energy inputs (250, 750 and 1600 Wh) were saccharified with cellulases and fermented to ethanol withSaccharomyces cerevisiaeusing separated hydrolysis and fermentation (SHF) or semi‐simultaneous saccharification and fermentation (SSSF) processes.RESULTS:Delignification of ASA pulps was between 25% and 50%, with low glucans losses. Pulp yield was from 70 to 78% for pulps ofP. radiataand 60% for the pulp ofP. caribaea. Pulps obtained after refining were evaluated in assays of enzymatic hydrolysis. Glucans‐to‐glucose conversion varied from 20 to 70%, depending on the degree of delignification and fibrillation of the pulps. The best ASA pulp ofP. radiatawas used in SHF and SSSF experiments of ethanol production. Such experiments produced maximum ethanol concentration of 20 g L−1, which represented roughly 90% of glucose conversion and an estimated amount of 260 L ethanol ton−1wood.P. caribaeapulp also presented good performance in the enzymatic hydrolysis and fermentation but, due to the low amount of cellulose present, only 140 L ethanol would be obtained from each ton of wood.CONCLUSION:ASA cooking followed by disk refining was shown to be an efficient pretreatment process, which generated a low lignified and high‐fibrillated substrate that allowed the production of ethanol from the softwoods with high conversion yields. Copyright © 2012 Society of Chemical Industry

The impacts of deacetylation prior to dilute acid pretreatment on the bioethanol process

BackgroundDilute acid pretreatment is a promising pretreatment technology for the biochemical production of ethanol from lignocellulosic biomass. During dilute acid pretreatment, xylan depolymerizes to form soluble xylose monomers and oligomers. Because the xylan found in nature is highly acetylated, the formation of xylose monomers requires two steps: 1) cleavage of the xylosidic bonds, and 2) cleavage of covalently bonded acetyl ester groups.ResultsIn this study, we show that the latter may be the rate limiting step for xylose monomer formation. Furthermore, acetyl groups are also found to be a cause of biomass recalcitrance and hydrolyzate toxicity. While the removal of acetyl groups from native corn stover by alkaline de-esterification prior to pretreatment improves overall process yields, the exact impact is highly dependent on the corn stover variety in use. Xylose monomer yields in pretreatment generally increases by greater than 10%. Compared to pretreated corn stover controls, the deacetylated corn stover feedstock is approximately 20% more digestible after pretreatment. Finally, by lowering hydrolyzate toxicity, xylose utilization and ethanol yields are further improved during fermentation by roughly 10% and 7%, respectively. In this study, several varieties of corn stover lots were investigated to test the robustness of the deacetylation-pretreatment-saccharification-fermentation process.ConclusionsDeacetylation shows significant improvement on glucose and xylose yields during pretreatment and enzymatic hydrolysis, but it also reduces hydrolyzate toxicity during fermentation, thereby improving ethanol yields and titer. The magnitude of effect is dependent on the selected corn stover variety, with several varieties achieving improvements of greater than 10% xylose yield in pretreatment, 20% glucose yield in low solids enzymatic hydrolysis and 7% overall ethanol yield.

Process integration study of a kraft pulp mill converted to an ethanol production plant – Part A: Potential for heat integration of thermal separation units

Energy efficiency is an important parameter for the profitability of biochemical ethanol production from lignocellulosic raw material. The yield of ethanol is generally low due to the limited amount of fermentable compounds in the raw material. Increasing energy efficiency leads to possibilities of exporting more by-products, which in turn might reduce the net production cost of ethanol. Energy efficiency is also an important issue when discussing the repurposing of kraft pulp mills to biorefineries, since the mills in question most likely will be old and inefficient. Investing in energy efficiency measures might therefore have a large effect on the economic performance. This paper discusses energy efficiency issues related to the repurposing of a kraft pulp mill into a lignocellulosic ethanol production plant. The studied process is a typical Scandinavian kraft pulp mill that has been converted to a biorefinery with ethanol as main product. A process integration study, using pinch analysis and process simulations, has been performed in order to assess alternative measures for improving the energy efficiency. The improvements found have also been related to the possibilities for by-product sales from the plant (electricity and/or lignin). In a forthcoming paper, which is the second part of this process integration study, an economic analysis based on the results from this paper will be presented.

Biorefinery sustainability assessment

AbstractThis article presents a comparative sustainability assessment of three biorefineries that produce liquid fuels used in current infrastructure. The three options considered are biochemical production of ethanol from grain and from cellulosic feedstocks and thermochemical production of Fischer‐Tropsch diesel from biomass‐derived syngas. These biorefineries were compared using numerous environmental, economic, and social metrics, with numerical values derived from a thorough review of recent literature. For each of the three biorefinery options, the metrics were not determined from a specific process design, but from a variety of different designs reported in literature. Where necessary, corn was selected as the feedstock for grain ethanol and switchgrass was selected for cellulosic ethanol and Fischer‐Tropsch diesel. These sustainability metrics were used in an Analytic Hierarchy Process decision analysis to compare the sustainability of the different biorefineries. Thus, a new decision‐making tool has been created in which the user can assign different weights to each category and its metrics. This tool was used to explore the influence of different weights, different market conditions, and uncertainties in the values of the metrics on the relative sustainability of the different options. Based on the results of this assessment, cellulosic ethanol biorefineries are modestly more sustainable than grain ethanol and Fischer‐Tropsch diesel. Grain ethanol was favorable economically whereas Fischer‐Tropsch diesel had the highest score on the societal metrics. © 2010 American Institute of Chemical Engineers Environ Prog, 2010

Techno-economic comparison of process technologies for biochemical ethanol production from corn stover

This techno-economic study compares several process technologies for the production of ethanol from lignocellulosic material, based on a 5- to 8-year time frame for implementation. While several previous techno-economic studies have focused on future technology benchmarks, this study examines the short-term commercial viability of biochemical ethanol production. With that goal, yields (where possible) were based on publicly available experimental data rather than projected data. Four pretreatment technologies (dilute-acid, 2-stage dilute-acid, hot water, and ammonia fiber explosion or AFEX); and three downstream process variations (pervaporation, separate 5-carbon and 6-carbon sugars fermentation, and on-site enzyme production) were included in the analysis. Each of these scenarios was modeled and economic analysis was performed for an “ nth plant” (a plant with the same technologies that have been employed in previous commercial plants) to estimate the total capital investment (TCI) and product value (PV). PV is the ethanol production cost, including a 10% return on investment. Sensitivity analysis has been performed to assess the impact of process variations and economic parameters on the PV. The dilute-acid pretreatment process has the lowest PV among all process scenarios, which is estimated to be $1.36/l of gasoline equivalent [LGE] ($5.13/gal of gasoline equivalent [GGE]). Sensitivity analysis shows that the PV is most sensitive to feedstock cost, enzyme cost, and installed equipment costs. A significant fraction of capital costs is related to producing heat and power from lignin in the biomass. Cellulosic ethanol production has yet to be commercialized. Hence, a pioneer plant is expected to be more costly to build and operate than an nth plant. To assess the impact of technological maturity on pioneer plant cost, a cost growth analysis was performed. The estimated value of PV for the pioneer plant is substantially larger than for the nth plant. The PV for the pioneer plant model with dilute-acid pretreatment is $2.30/LGE ($8.72/GGE) for the most probable scenario, and the estimated TCI was more than double the nth plant cost.

Modeling and optimization of the dilute-sulfuric-acid pretreatment of corn stover, poplar and switchgrass

Lignocellulosic biomass may be used as a potential renewable feedstock for biochemical production of ethanol as an alternative transportation fuel. However, cellulose, which is the major source of fermentable sugars in these materials, is protected by a network of lignin and hemicellulose. The dilute-sulfuric-acid pretreatment removes this protecting shield and makes the cellulose more susceptible to enzymatic digestion. In this study, three lignocellulosic feedstocks (i.e. corn stover, poplar and switchgrass) were pretreated with dilute sulfuric acid (0.6, 0.9 and 1.2% w/w) at relatively high temperatures (140, 160 and 180°C) in a Parr batch reactor. The hydrolysis of hemicellulose to its monomeric constituents and possible degradation of these monomers were modeled by a series of first-order reactions. The kinetic parameters of two mathematical models for predicting the percentage of xylan remaining in the substrate after pretreatment and the net xylose yield in the liquid stream were determined using the actual acid concentration in the reactor after accounting for the neutralization effect of the substrates.

PRODUCTION OF ETHANOL WITH SACCHAROMYCES CEREVISIAE IN A CONTINUOUS REACTOR Note II: tests and modelling for a packed tubular reactor with immobilized yeasts

The biochemical production of ethanol has been studied in a packed tubular reactor with Saccharomyces Cerevisiae immobilized on wooden cubes. The kinetics of the reaction was described in a previous paper. The experimental axial profiles for the substrate and product concentrations are compared with those calculated from a reactor model obtained by introducing the biochemical kinetic expression in the design equations. A good fit between the experimental and the calculated values could only be obtained by including a biological efficiency coefficient. The reactor was kept in operation for 28 days to assess its technological reliability. It was found to be biologically stable. Its productivity was constant and comparable to that reported in the literature for similar reactors.