Cellulosic Ethanol Production Research Articles

Influence of feedstock selection on cellulosic ethanol production based on densified biomass with calcium hydroxide and regular steam pretreatment

Feedstock selection is a key factor affecting the process of cellulosic ethanol production. Densifying lignocellulosic biomass with chemicals (calcium hydroxide) followed by regular steam autoclave (DLCA(ch)) is an emerging and efficient pretreatment technology. In this study, different crop straws were selected as feedstock in a DLCA(ch) based process for cellulosic ethanol production, and their experimental and economic performances were evaluated. Both single crop straws and mixed crop straws were used and compared as feedstock for DLCA(ch) based biorefinery. Among single crop straws of corn stover, rice straw and wheat straw, wheat straw had the highest ethanol yield and the lowest feedstock cost, with a minimum ethanol selling price of 2.03 $/gal ethanol considering a 10 % internal rate of return and a 2000 tons crop straw per day biorefinery scale. When mixed crop straws were used as the feedstock, both feedstock cost and ethanol production cost were further reduced, and the minimum ethanol selling price was reduced to 2.02 $/gal ethanol. In addition, the use of mixed crop straws has great potential for large scale DLCA(ch) based process for cellulosic ethanol production.

A cellulosomal yeast reaction system of lignin-degrading enzymes for cellulosic ethanol fermentation.

Biofuel production from lignocellulose feedstocks is sustainable and environmentally friendly. However, the lignocellulosic pretreatment could produce fermentation inhibitors causing multiple stresses and low yield. Therefore, the engineering construction of highly resistant microorganisms is greatly significant. In this study, a composite functional chimeric cellulosome equipped with laccase, versatile peroxidase, and lytic polysaccharide monooxygenase was riveted on the surface of Saccharomyces cerevisiae to construct a novel yeast strain YI/LVP for synergistic lignin degradation and cellulosic ethanol production. The assembly of cellulosome was assayed by immunofluorescence microscopy and flow cytometry. During the whole process of fermentation, the maximum ethanol concentration and cellulose conversion of engineering strain YI/LVP reached 8.68g/L and 83.41%, respectively. The results proved the availability of artificial chimeric cellulosome containing lignin-degradation enzymes for cellulosic ethanol production. The purpose of the study was to improve the inhibitor tolerance and fermentation performance of S. cerevisiae through the construction and optimization of a synergistic lignin-degrading enzyme system based on cellulosome.

Engineering Compositionally Uniform Yeast Whole-Cell Biocatalysts with Maximized Surface Enzyme Density for Cellulosic Biofuel Production.

In recent decades, whole-cell biocatalysis has played an increasingly important role in the food, pharmaceutical, and energy sector. One promising application is the use of ethanologenic yeast displaying minicellulosomes on the cell surface to combine cellulose hydrolysis and fermentation into a single step for consolidated bioprocessing. However, cellulosic ethanol production using existing yeast whole-cell biocatalysts (yWCBs) has not reached industrial feasibility due to their inefficient cellulose hydrolysis. As prior studies have demonstrated enzyme density on the yWCB surface to be one of the most important parameters for enhancing cellulose hydrolysis, we sought to maximize this parameter at both the population and single-cell levels in yWCBs displaying tetrafunctional minicellulosomes. At the population level, enzyme density is limited by the presence of a nondisplay population constituting 25-50% of all cells. In this study, we identified the cause to be plasmid loss and successfully eliminated the nondisplay population to generate compositionally uniform yWCBs. At the single-cell level, we demonstrate that enzyme density is limited by molecular crowding, which hinders minicellulosome assembly. By adjusting the integrated gene copy number, we obtained yWCBs of tunable enzyme display levels. This tunability allowed us to avoid the crowding-limited regime and achieve a maximum enzyme density per cell. As a result, the best strain showed a cellulose-to-ethanol yield of 4.92 g/g, corresponding to 96% of the theoretical maximum and near-complete conversion (∼96%) of the starting cellulose (1% PASC). Our holistic engineering strategy that combines a population and single-cell level approach is broadly applicable to enhance the WCB performance in other biocatalytic cascade schemes.

Life cycle assessment and techno-economic analysis of wood-based biorefineries for cellulosic ethanol production

Poplar is widely used in the paper industry and accompanied by abundant branches waste, which is potential feedstock for bioethanol production. Acid-chlorite pretreatment can selectively remove lignin, thereby significantly increasing enzymatic efficiency. Moreover, lignin residues valorization via gasification-syngas fermentation can achieve higher fuel yield. Herein, environmental and economic aspects were conducted to assess technological routes, which guides further process optimization. Life cycle assessment results show that wood-based biorefineries especially coupling scenarios have significant advantages in reducing global warming potential in contrast to fossil-based automotive fuels. Normalization results indicate that acidification potential surpasses other indicators as the primary impact category. In terms of economic feasibility, coupling scenarios present better investment prospects. Bioethanol yield is the most critical factor affecting market competitiveness. Minimum ethanol selling price below ethanol international market price is promising with higher-levels technology. Further work should be focused on technological breakthrough, consumable reduction or replacement.

Study of acid hydrolysis and submerged fermentation parameters in second generation ethanol production using cassava waste

Biofuels are an alternative to reduce the environmental impacts caused by the use of petroleum-based fuels. Second generation ethanol comes from lignocellulosic materials that are little used or discarded in the environment, including agro-industrial waste. These residues are rich in sugars that can be converted by ethanol-producing microorganisms. In this context, the present work uses cassava waste (Manihot esculenta Crantz) obtained during the processing of starch as a raw material for the production of cellulosic ethanol, as well as evaluating different parameters in acid hydrolysis and during submerged fermentation using the strain Saccharomyces cerevisiae ATCC 26602. Experiments of acid hydrolysis of these residues with sulfuric acid in concentrations of 0.5% to 5.0% (v/v) were carried out. The results demonstrated that 2.0% H2SO4 for 10 min. reaction at 121 ºC/1.1 atm in an autoclave reached the highest release of reducing sugars present in the residue (131.09 g.L-1). The ideal conditions for alcoholic fermentation using yeast were pH 6.5, temperature of 35 ºC, without rotation and initial reducing sugar concentration of 50 g.L-1, resulting in 21.23 g.L-1 of ethanol with productivity of 1.86 g.L-¹.h-¹ and theoretical yield of 96.5% after 12 hours of fermentation. The results indicated that the cassava waste serve as a potential substrate for the production of second generation ethanol. Thus, this study provides data on the most suitable conditions for the use of these industrial wastes aiming at the generation of a renewable fuel, an increasingly attractive feature for the world, where the economic and environmental concern is growing.

Characteristics and evolution of bioethanol from Manila Tamarind (Pithecellobium dulce) leaf through fermentation

<p>This study's two primary goals are to synthesize bioethanol from biowaste and examine its thermal characteristics. Bioethanol must first undergo a comprehensive assessment of its thermal characteristics in order to be approved for usage in spark-ignition engines. A multi-step procedure comprising extraction, pretreatment, enzymatic hydrolysis, and fermentation was used to manufacture the bioethanol. The raw material was put through a preliminary screening using thermogravimetric analysis to find the mass loss rate as a function of temperature before to starting this process. Remarkably, the Manila tamarind leaves exhibited the highest mass loss, up to 34%. Enzymatic cellulose conversion to fermentable sugars was a critical step in the production of cellulosic ethanol. Following hydrolysis, Saccharomyces cerevisiae was employed in the fermentation process, leading to the bioethanol synthesis phase. The Manila Tamarind leaves yielded the most, around 29% by weight, which is amazing. In order to assess the thermal properties of the extracted ethanol, a variety of parameters were carefully examined, including the viscosity, density, cetane number, and calorific value. In each of these areas, mixtures of tire oil, gasoline, and bioethanol consistently outperformed the others. Furthermore, Fourier Transform Infrared Spectrometry spectra were utilized to validate the concentrations of potential groups, including alcohol, aromatic, alkyne, amide, and carbonyl groups. Clear objectives guide the fermentation process, aiming for consistent quality, safety, and functionality in the end product.</p>

Transcriptomic analysis of ncRNAs and mRNAs interactions during drought stress in switchgrass

Switchgrass (Panicum virgatum L.) plays a pivotal role as a bioenergy feedstock in the production of cellulosic ethanol and contributes significantly to enhancing ecological grasslands and soil quality. The utilization of non-coding RNAs (ncRNAs) has gained momentum in deciphering the intricate genetic responses to abiotic stress in various plant species. Nevertheless, the current research landscape lacks a comprehensive exploration of the responses of diverse ncRNAs, including long non-coding RNAs (lncRNAs), circular RNAs (circRNAs), and microRNAs (miRNAs), to drought stress in switchgrass. In this study, we employed whole transcriptome sequencing to comprehensively characterize the expression profiles of both mRNA and ncRNAs during episodes of drought stress in switchgrass. Our analysis identified a total of 12,511 mRNAs, 59 miRNAs, 38 circRNAs, and 368 lncRNAs that exhibited significant differential expression between normal and drought-treated switchgrass leaves. Notably, the majority of up-regulated mRNAs displayed pronounced enrichment within the starch and sucrose metabolism pathway, as validated through KEGG analysis. Co-expression analysis illuminated that differentially expressed (DE) lncRNAs conceivably regulated 1308 protein-coding genes in trans and 7110 protein-coding genes in cis. Furthermore, both cis- and trans-target mRNAs of DE lncRNAs exhibited enrichment in four common KEGG pathways. The intricate interplay between lncRNAs and circRNAs with miRNAs via miRNA response elements was explored within the competitive endogenous RNA (ceRNA) network framework. As a result, we constructed elaborate regulatory networks, including lncRNA-novel_miRNA480-mRNA, lncRNA-novel_miRNA304-mRNA, lncRNA/circRNA-novel_miRNA122-PvSS4, and lncRNA/circRNA-novel_miRNA14-PvSS4, and subsequently validated the functionality of the target gene, starch synthase 4 (PvSS4). Furthermore, through the overexpression of PvSS4, we ascertained its capacity to enhance drought tolerance in yeast. However, it is noteworthy that PvSS4 did not exhibit any discernible impact under salt stress conditions. These findings, as presented herein, not only contribute substantively to our understanding of ceRNA networks but also offer a basis for further investigations into their potential functions in response to drought stress in switchgrass.

Application of Aromatic Ring Quaternary Ammonium and Phosphonium Salts–Carboxylic Acids-Based Deep Eutectic Solvent for Enhanced Sugarcane Bagasse Pretreatment, Enzymatic Hydrolysis, and Cellulosic Ethanol Production

Deep eutectic solvents (DESs) with a hydrophobic aromatic ring structure offer a promising pretreatment method for the selective delignification of lignocellulosic biomass, thereby enhancing enzymatic hydrolysis. Further investigation is needed to determine whether the increased presence of aromatic rings in hydrogen bond receptors leads to a more pronounced enhancement of lignin removal. In this study, six DES systems were prepared using lactic acid (LA)/acetic acid (AA)/levulinic acid (LEA) as hydrogen bond donors (HBD), along with two independent hydrogen bond acceptors (HBA) (benzyl triethyl ammonium chloride (TEBAC)/benzyl triphenyl phosphonium chloride (BPP)) to evaluate their ability to break down sugarcane bagasse (SCB). The pretreatment of the SCB (raw material) was carried out with the above DESs at 120 °C for 90 min with a solid–liquid ratio of 1:15. The results indicated that an increase in the number of aromatic rings may result in steric hindrance during DES pretreatment, potentially diminishing the efficacy of delignification. Notably, the use of the TEBAC:LA-based DES under mild operating conditions proved highly efficient in lignin removal, achieving 85.33 ± 0.52% for lignin removal and 98.67 ± 2.84% for cellulose recovery, respectively. The maximum digestibilities of glucan (56.85 ± 0.73%) and xylan (66.41 ± 3.06%) were attained after TEBAC:LA pretreatment. Furthermore, the maximum ethanol concentration and productivity attained from TEBAC:LA-based DES-pretreated SCB were 24.50 g/L and 0.68 g/(L·h), respectively. Finally, the comprehensive structural analyses of SCB, employing X-rays, FT-IR, and SEM techniques, provided valuable insights into the deconstruction process facilitated by different combinations of HBDs and HBAs within the DES pretreatment.

High titer (>100 g/L) ethanol production from pretreated corn stover hydrolysate by modified yeast strains

Developing a reliable lignocellulose pretreatment method to extract mixed sugars and engineering efficient strains capable of utilizing xylose are crucial for advancing cellulosic ethanol production. In this study, chemical and characterization analyses revealed that alkali cooking can significantly remove lignin from lignocellulose crops. The highest amount of mixed sugar was obtained from corn stover hydrolysates with a 15 % solid loading. Our genetically engineered yeast strain ΔsnR4, derived from a well-staged WXY70, demonstrated excellent performance in low 10 % solids loading corn stover hydrolysate, producing a high ethanol yield of 0.485 g/g total sugars. When a combined NaOH-ball milling pretreatment strategy was applied at high solids loading, ΔsnR4 exhibited the maximum ethanol titer of 110.9 g/L within 36 h, achieving an ethanol yield of 92.9 % theoretical maximum. Therefore, ΔsnR4 is highly compatible with high solid loading NaOH-ball milling pretreatment, making it a potential candidate for industrial cellulosic ethanol.

Cellulosic ethanol production: Assessment of the impacts of learning and plant capacity

Cellulosic ethanol has great potential to displace fossil fuels and reduce greenhouse gas emissions, but supply is low due to high cost. Learning-by-doing is a strategy to reduce cost with increases in capacity. This study attempts to understand how learning-by-doing affects the growth of cellulosic ethanol in synergy with plant capacity. We modeled a three-phase learning effect using a hybrid general equilibrium model to project the U.S cellulosic ethanol production. The reference case projects an annual production of 5.49 million gallons (MG) from 2030 to 2040. With strong policy support of a high mandate, the U.S. is projected to produce 171 MG of cellulosic ethanol in 2040. However, the learning-by-doing effect cannot be initiated because only 4 large-scale centralized plants will be built. When plant size reduces, learning-by-doing is enabled, and 2040 cellulosic ethanol production can reach 3.27 billion gallons. Similar result is predicted for the cases representing an actual biorefinery. Fast and widespread learning is estimated to greatly increase production when plants have lower capital cost. The findings show that policy incentives are critical to technology development when cost is a significant barrier. Additionally, building small-size plants is a strategy that will enable and facilitate the learning-by-doing effect.

The impact of lignocellulosic ethanol production on the environment from a life cycle perspective

In the production process of cellulosic ethanol, all sections are closely related. It is difficult to study its producing law and key factors that affect the process only by experimental means. Computer simulation has a powerful data mining ability, which can analyze, design, and evaluate the production process of cellulosic ethanol. Specifically, it can use data calculated by Aspen Plus before, and analyze the impact of cellulose ethanol production on the environment by life cycle assessment (LCA). Results show that the total environmental impact value of the whole process is 0.20∼0.37 person·a/t. And in the whole process, the growth stage and the production stage have the biggest impact.

Changes in various lignocellulose biomasses structure after microwave-assisted hydrotropic pretreatment

Effective pretreatment of lignocellulosic biomass combined with delignification is a condition for effective enzymatic hydrolysis of cellulose, which is of key significance for the efficiency of the process of production of cellulosic ethanol. Becoming aware of the full range of changes in the structure of lignocellulose as a result of biomass pretreatment is important in view of the necessity to optimise the process of technological production of bioethanol. Our research was aimed at a comprehensive analysis of changes in structure of pine chip (softwood), beech chip (hardwood) and wheat straw (non-wood) biomasses resulting from a newly developed pretreatment method combining the use of hydrotrope in the form of sodium cumene sulfonate and microwave radiation. The performed analyses of the biomass composition indicate a high effectiveness of the proposed pretreatment method in the area of biomass delignification and hemicellulose removal. An effective removal of amorphous substances, i.e. lignin and hemicellulose, led to an increase in the crystallinity of pine chip biomass to 55%, and beech chips and wheat straw biomasses to 61%.

Fed-batch SSF with pre-saccharification as a strategy to reduce enzyme dosage in cellulosic ethanol production

The pulp and paper industry is a strategic sector to be converted into a forest-based biorefinery, taking advantage of know-how, existing infrastructures and well-established logistic operations to deal with a daily high volume of forest residues. Bioethanol production from Eucalyptus globulus bark previously pretreated by kraft pulping was assessed following two configurations at the bioreactor scale: separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF). This last configuration was optimized by using a pre-saccharification and a fed-batch feeding (FB PS-SSF), allowing for a reduction in the enzyme dosage from 25 to 10 FPU gCH−1, which is very advantageous from an economic point of view. For 10 FPU gCH−1 enzyme dosage and 20 % (w/v) total solids loading, an ethanol concentration of around 70.6 g L−1 was accomplished, corresponding to overall conversion efficiency and productivity of about 78 % and 1.35 g L−1 h−1, respectively. Increasing solids loading from 20 to 26 % (w/v), using the same enzyme dosage, resulted in the highest ethanol concentration (84.6 g L−1) despite the too-long assay and the decline in productivity. Overall, FB PS-SSF improved bioethanol concentration and allowed decreased enzymatic usage over SHF, maintaining high ethanol concentration.

Improving simultaneous saccharification and fermentation by pre-saccharification and high solids operation for bioethanol production from Eucalyptus globulus bark

The European Green Deal emerged as a package of policy initiatives for a green transition, aiming to reach climate neutrality by 2050. Accordingly, the pulp and paper industry has been focused on upgrading residues into value-added products within the forest-based circular economy business model. In this context, this study considered the possibility of using bark, a residue available in high volume on factory floors, for cellulosic ethanol production instead of typical burning for energy generation. Bioconversion of lignocellulosic polysaccharides of bark is a challenge and simultaneous saccharification and fermentation (SSF) setup was chosen to boost cellulosic ethanol production. The introduction of a short pre-saccharification (PS) stage (0, 1 and 4 h) in bioethanol production from Eucalyptus globulus bark, previously submitted to a kraft pretreatment, following an integrated configuration, PS-SSF, at the bioreactor scale improved bioethanol concentration. It was observed that the longer pre-saccharification, the higher productivity. Shifting from this batch PS-SSF (4 h) to a fed-batch PS-SSF (4 h) configuration allowed to increase the solids loading from 8% to 20% (w/v), raising the final bioethanol concentration from 27.4 to 75.9 g L−1, and improving by itself the overall productivity more than 25%. These results show that in the pulp and paper mills, an integrated biorefinery should be considered to foster the total resources use within the circular economy model.

High-Efficient Production of Cellulosic Ethanol from Corn Fiber Based on the Suitable C5/C6 Co-Fermentation Saccharomyces cerevisiae Strain

As a potential alternative to fossil-based fuels, cellulosic ethanol has attracted much attention due to its great benefit to energy sustainability and environmental friendliness. However, at present, the industrial competitiveness of cellulosic ethanol production is still insufficient compared with fossil-based fuels because of the higher costs. Expanding the range of lignocellulosic biomass may be a promising measure to promote the economical production of cellulosic ethanol. Corn fiber, a byproduct from the corn deep-processing, is an attractive feedstock for cellulosic ethanol production because of its rich carbohydrate content (generally exceeding 65% of dry weight), almost no transportation cost, and low lignin content allow it to be easily handled. This study first optimized the hydrolysis conditions, including the pretreatment and enzymolysis process based on dilute sulfuric acid, to achieve a high sugar yield. Then, the corn fiber hydrolysates obtained under different hydrolysis conditions were suitably fermented by different C5/C6 co-fermentation Saccharomyces cerevisiae, indicating that the hydrolysate at high solid loading (20%) needs to detoxification to a certain extent but not low solid loading (10%) to achieve high ethanol yield. Finally, the fermentation of the 20% solid loading hydrolysates with resin detoxification was performed in a 50 L bioreactor, achieving the sugar (glucose and xylose) metabolic rate of 2.24 g L −1 h −1 and ethanol yield of 92% of the theoretical value, which are the highest reported levels to date. This study provided a potential process route for cellulosic ethanol production from corn fiber from the perspective of the suitability between the upstream hydrolysis process and the downstream fermentation strain.

Steam Explosion of Eucalyptus grandis Sawdust for Ethanol Production within a Biorefinery Approach

In this work, Eucalyptus grandis sawdust was subjected to steam explosion as the first step in cellulosic ethanol production within a biorefinery approach. The effect of the moisture content in the eucalypt sawdust (8 and 50%) and pretreatment process variables, such as temperature and residence time, were evaluated along with the influence of the water washing of steam-exploded solids on enzymatic hydrolysis and C6 fermentation yields. All other process streams were characterized to evaluate the recovery yield of valuable co-products. A recovery of nearly 100% glucans in the solid fraction and 60% xylans in the liquid fraction, mainly as partially acetylated oligomers, was obtained. The best enzymatic hydrolysis efficiencies (66–67%) were achieved after pretreatment at 205 °C for 10 min. The washing of pretreated sawdust with water improved the hydrolysis efficiencies and ethanol production yields by 10% compared to the unwashed pretreated solids under the same experimental condition. The highest ethanol yields were achieved after pretreatment of the sawdust with an 8% moisture content at 205 °C for 10 min, enzymatic hydrolysis at 13 wt% total solids with 25 FPU/g glucans, and fermentation with S. cerevisiae PE-2. In this case, 227 L ethanol and 40 kg total xylose (including xylo-oligomers) were obtained per ton of dry eucalypt sawdust.

Quantitative and qualitative evaluation of novel energy cane accessions for sugar, bioenergy, 1 G, and 2 G ethanol production

Traditionally, the sugarcane breeding programs are focused on increasing sugar content, often at the expense of fiber content and biomass yield. However, with the growing interest in 2 G (cellulosic) ethanol and bioenergy production, there has been a paradigm shift toward quantitative parameters. This study investigated the qualitative and quantitative parameters of energy cane clones throughout the harvest season. It hypothesizes that juice composition, fiber content, and maturation curve will vary, reaching a point where these characteristics become more desirable for industrial processes. Three energy cane clones (C33, C34, and C35) derived from a breeding program at the Agronomic Institute of Campinas (IAC) were selected for evaluation alongside a commercial reference cultivar (IAC-942094). The results indicate that energy cane possesses significant potential for biofuel and energy production. Additionally, energy cane clones exhibit higher agricultural yields and greater production of sugars per unit area than traditional sugarcane. The high fiber content in energy cane clones, coupled with their agricultural productivity, makes them excellent sources of lignocellulosic material for both 1 G and 2 G ethanol production and cogeneration of electric energy. Energy cane clones C34 and C35, in particular, demonstrate the potential to increase 2 G ethanol production and the supply of electrical and thermal energy by up to 300% and 250%, respectively, compared to conventional sugarcane. These findings highlight the promising role of energy cane as a sustainable bioenergy production alternative, contributing to improved sustainability indices in the biofuel and biomass energy sectors.

The effect of pretreatment choice on cellulosic ethanol production from sugarcane straw: An insight into environmental impact profile and GHG emissions mitigation potential in Brazil

The exploration of residual lignocellulosic biomass for biofuel production is crucial to achieve significant greenhouse gas (GHG) emissions mitigation within the following decades, translating to diminished agricultural environmental impact and land-use change dynamics. On the other hand, cellulosic ethanol production pathways are typically resource-intensive, in energy and chemical terms, which directly influence its carbon intensity. Pretreatment choice, to this end, is key, since it dictates the overall process performance and yield, and may include crucial flows, under the life-cycle perspective, such as solvents and other chemicals. This work, then, aims to evaluate the effect of pretreatment choice, namely hydrothermal (HT), steam explosion (SE), and alkaline (AK), in the technical and environmental performance of cellulosic ethanol production from sugarcane straw (SCS), extending this analysis to the final GHG emissions mitigation potential for gasoline and fossil-generated electricity substitution, under the Brazilian context in São Paulo. Results show that, while AK provided the highest ethanol yield, this pretreatment option gave the lowest electricity generation surplus, and its sodium hydroxide usage was identified as an important environmental hotspot in most impact categories, which narrowed down its GHG emission mitigation gap for gasoline substitution. HT and SE presented similar ethanol and electricity yields, with SE being the most balanced option in terms of productivity and environmental impact profile. By selecting the SE route, all of the available SCS in São Paulo could be converted into 10% of the Brazilian annual ethanol production, and mitigate 5.4 MtCO2e of gasoline emissions, 15% of the Brazilian Biofuel Policy (RenovaBio) target for 2022.

Recovery and characterization of cellulosic ethanol from fermentation of sugarcane bagasse

Industrial production of ethanol by fermentation using renewable feedstock such as sugarcane stalks has been demonstrated as a sustainable fuel chain in Brazil. This work focused on the production of cellulosic ethanol from sugarcane bagasse in a pilot scale unit by applying the current bioprocessing strategies with the aim of recovering and characterizing the end products. The feedstock was pretreated at 190 °C and a residence time of 10 min. Enzymatic hydrolysis was performed with commercial cellulolytic enzymes. Fermentation’s substrates were formulated with hydrolysate and supplemented with 8%wt sugarcane molasses. The fermentations were set up to mimic the conventional industrial fermentation in Brazil’s ethanol distilleries at high cell density with cell recycling. The fermentation resulted in a reproducible performance by the yield of 0.49 g/g, productivity of 6.96 g/(L∙h), and cell viability of 95.3%. Ethanol was recovered in a lab-scale distillation batch system. Distilled fractions showed higher content of higher alcohols and sulfur content than the standard specification of ANP (National Agency of Petroleum - Brazilian Agency) for ethanol fuel. The distillation bottom product (vinasse) presented most characteristics suitable for fertilizer or biogas applications, except for sodium and sulfate content. Therefore, for a successful technology, transference processing adjustments should be made to make the product commercially suitable and the side stream compatible for disposal as fertilizer or digestion for biogas production.

Technoeconomic analysis of a fungal pretreatment-based cellulosic ethanol production

Cellulosic biomass shows great potential as feedstock for bioethanol production. Despite clear benefits in terms of greenhouse gas mitigation and bioproduct potential, the commercial production of cellulosic ethanol remains economically challenging at the current state of technology. This paper presents a technoeconomic analysis of a fungal pretreatment-based cellulosic ethanol plant with a processing capacity of 2000 tonnes of switchgrass per day. The production process model was designed and simulated using SuperPro Designer. The plant's ethanol yield, capital investment per unit capacity, and unit ethanol production cost were estimated to be 211.90 L/t of switchgrass, $ 3.60/L, and $ 1.44/L of ethanol, respectively. Fungal pretreatment was the major contributor (72%) to the total capital investment, mainly due to the large quantity of equipment required in the process. A positive net present value (NPV) was generated for the baseline model at ethanol selling price of $ 1.50/L, which increased by 5-fold for 80% glucose yield. Glucose yield was the most sensitive to NPV for all the process parameters evaluated.