Generation Ethanol Production Research Articles

Selection and improvement of Saccharomyces cerevisiae by direct and mass mating for integrated first and second generation (1G + 2G) ethanol production

The integrated 1G + 2G ethanol production process seems to be a feasible strategy considering the Brazilian scenario, in which sugarcane molasses and bagasse are available substrates in biorefineries. However, such process imposes harsh conditions to yeasts, which must be able to simultaneously deal with several stresses from molasses and hydrolysate. In this work, improved hybrid strains of Saccharomyces cerevisiae with higher resistance for an integrated 1G + 2G ethanol production were obtained by hybridization technique. Initially, 663 wild S. cerevisiae strains were screened in microculture growth assays. Seven strains were pre-selected out of 40 based on their stress multi-tolerance traits. Subsequently, these pre-selected strains underwent evaluation in cell-recycling fed-batch fermentation conditions utilizing a medium containing molasses-bagasse hydrolysate. The two most successful strains from this evaluation were subjected to sporulation, yielding haploid cells. These haploid cells were then subjected to crossbreeding, employing direct and mass mating techniques. From the initial pool of 7 pre-selected strains, 3 hybrid strains were selected due to their enhanced resistance under the demanding conditions of cell recycling fed-batch fermentation, particularly when utilizing a higher osmotic molasses-hydrolysate medium. These hybrid strains consistently exhibited high cell viability rates and effectively accumulated elevated levels of trehalose and glycogen over the course of five fermentation cycles. Remarkably, they maintained ethanol productivity at levels comparable to their respective parental strains. The genotyping molecular identification attested the difference between the hybrids and the parental strains. The 3 hybrids selected seem to present valuable backgrounds for metabolic engineering for lignocellulosic-derived xylose fermentation.

Integrated techno-economic, investment risk and life cycle analysis of Indian lignocellulosic biomass valorisation via co-gasification and syngas fermentation

The current work presents techno-economic and life cycle assessment of a co-gasification- fermentation hybrid model of bio-ethanol production with recycle and recovery of different resources. The model is also equipped with waste heat recovery from the hot syngas and power generation from unconverted syngas. The co-gasification process is based on Gibbs’ free energy minimization and syngas fermentation follows chemical equilibrium. With the objective of studying the economic feasibility and environmental sustainability of the proposed model, techno-economic assessment followed by financial risk analysis and life cycle analysis has been conducted. On the basis of 1 kg product bio-ethanol the results of the life cycle analysis, the present bio-ethanol production process have been compared to those of 1st generation ethanol production and biomass to bio-ethanol conversion via sugar platform. The present process is found to be economically viable with a net present value, internal rate of return and payback period of 18.7 M$, 13.33% and 6.7 years respectively. Monte Carlo simulation of financial risk has been modelled to predict the uncertainty over net present value and 81.8% is the probability of getting a non-negative net present value. Life cycle analysis suggest that the presented process emits 1.23 kg less CO2 per kg of bio-ethanol compared to the conventional bio-ethanol production process from biomass.

Chemical and histological characterization of internodes of sugarcane and energy-cane hybrids throughout plant development

Sugarcane and energy-cane are important Saccharum spp. hybrids that encompass desirable features for energy production. Their stem lignocellulose can be used as the raw material for the second-generation ethanol industry, contributing to accelerated fossil-fuel replacement. However, knowledge on the internode composition and saccharification of these hybrids is still needed to optimize their uses, especially in energy-cane. In this work, the agronomical, chemical, and histological internode features and saccharification potential were analyzed in sugarcane and energy-cane hybrids across four critical developmental stages (tillering, grand growth, early ripening and late ripening) and several internode positions along the stem. Except for galactose content that was higher in the sugarcane hybrid compared to the energy-cane, cell-wall composition was fairly similar in both types of cane across the growing cycle. Among main cell-wall components, maximum crystalline cellulose and matrix polysaccharides contents were observed at tillering and late ripening, respectively. Lignin concentrated towards upper internode positions and advanced developmental stages. Saccharification potential augmented towards apical internodes and early developmental stages, and negatively correlated to lignin and xylose contents. The energy-cane hybrid showed lower number of vascular bundles and metaxylem diameter and its lignin deposition was more extended towards the parenchymal tissue, when compared to the commercial sugarcane throughout the growth cycle. Taken together, these findings demonstrate that developmental stage and internode position largely affect cell-wall composition and its recalcitrance to enzymatic degradation. The use of sugarcane/energy-cane lignocellulose from early developmental stages could be beneficial for the second generation ethanol production. Novel management practices for that usage should consider economic, social and environmental sustainability standards under a sugar/ethanol production scheme.

Sweet Sorghum And Sweet Pearl Millet Carbohydrate Extraction and Preservation for Bioethanol Production and Bagasse Valorization: A Review

Highlights Sweet sorghum and sweet pearl millet are interesting feedstocks for ethanol production. Biomass and juice storage are key steps for carbohydrate preservation. Produced bagasse can be valorized in many ways, including as silage or for cellulosic ethanol production. Abstract. Sweet sorghum and sweet pearl millet have been considered as potential energy crops. They have many advantages in terms of ethanol production compared to corn and sugarcane, such as lower requirements for water and fertilizers, higher tolerance to drought, and lower competition with the food sector. Sweet sorghum and sweet pearl millet stems are rich in water-soluble carbohydrates (WSC) (sucrose, fructose, and glucose), and their biomass has to be crushed for juice extraction. However, the extraction efficiency of WSC varied widely depending on the press type used and the parameters considered during the pressing process (stripping stems from leaves or not, compressive force magnitude, smooth or grooved press rollers, number of times of biomass pressing, etc.). WSCs are easily degradable, causing technical challenges related to crop handling before pressing and juice storage thereafter. Some studies focused on stem preserving methods, whereas others dealt with extending the shelf life of the juice. To make the use of sweet sorghum and sweet pearl millet as energy crops more profitable, the bagasse (residue) generated from biomass pressing can be valorized in different ways, mainly as silage or for second generation ethanol production. The objective of this review was to assess the efficiency of different presses used for juice extraction and discuss various methods tested for WSC conservation from deterioration as well as possible bagasse valorization. Keywords: Bagasse, Carbohydrates, Ethanol, Press, Sweet pearl millet, Sweet sorghum.

Metaproteomic Analysis of the Anaerobic Community Involved in the Co-Digestion of Residues from Sugarcane Ethanol Production for Biogas Generation

The proteomics analysis could contribute to better understand about metabolic pathways in anaerobic digestion community because it still as a “black-box” process. This study aimed to analyze the proteins of the anaerobic co-digestion performed in reactors containing residues from the first and second generation ethanol production. Metaproteomics analysis was carried out for three types of samples: anaerobic sludge without substrate (SI), semi-continuous stirred reactor (s-CSTR) with co-digestion of filter cake, vinasse, and deacetylation liquor (R-CoAD) and s-CSTR with co-digestion of these aforementioned residues adding Fe3O4 nanoparticles (R-NP). The R-CoAD reactor achieved 234 NmLCH4 gVS−1 and 65% of CH4 in the biogas, while the R-NP reactor reached 2800 NmLCH4 gVS−1 and 80% of CH4. The main proteins found were enolase, xylose isomerase, pyruvate phosphate dikinase, with different proportion in each sample, indicating some change in pathways. However, according to those identified proteins, the main metabolic routes involved in the co-digestion was the syntrophic acetate oxidation coupled with hydrogenotrophic methanogenesis, with the CH4 production occurring preferentially via CO2 reduction. These findings contributed to unravel the anaerobic co-digestion at a micromolecular level, and may select a more appropriate inoculum for biogas production according to that residue, reducing reaction time and increasing productivity.

Transforming second-generation ethanol production waste into sustainable enzymatic cosmetic inputs

Agro-industrial residues were used as a successful, cheap and renewable substrate, capable of increasing activity of ligninolytic enzymes for further use in melanin degradation assays to develop inputs for the treatment of skin hyperpigmentation. The analysis of melanin degradation was performed in a quantitative and qualitative way. The enzymatic crude broth extract, rich in laccases , produced by Marasmiellus palmivorus VE111 in medium formulated with lignocellulosic residues of Araucaria angustifolia subjected to hydrolysis and alcoholic fermentation , degraded almost 33% of the melanin content and enzymatic crude broth extract produced by Pycnoporus sanguineus PR_32 degraded 13%, in just 8 h, using vanillin as a mediator. Proton 2D NMR spectra show melanin changes after laccase treatment. This work has provided an insight for the development of ecofriendly, sustainable and innovative cosmetics to deal with skin hyperpigmentation. • By-products from 2nd generation ethanol production act as inducer to laccases activity. • Vanillin can be used as a safe redox mediator for laccase activity in cosmetics. • Laccase from Marasmiellus palmivorus VE111 can degrade melanin. • HSQC 2D NMR data shows changes in melanin after enzymatic treatment.

Integration of first- and second-generation ethanol production: Evaluation of a mathematical model to describe sucrose and xylose co-fermentation by recombinant Saccharomyces cerevisiae

The use of hydrolysates of lignocellulosic materials and microbial platforms present themselves as viable alternatives to the current system energy. The metabolization of the different carbohydrates present in the hydrolysates by yeasts is a process bottleneck. Genetically modified yeasts can ferment different carbohydrates. Furthermore, mathematical modelling helps to understand the dynamics and interactions during the process and predicts other conditions. The performance of the recombinant yeast Saccharomyces cerevisiae was evaluated for co-fermentation in different carbohydrates proportions (C12 – C5, 30.67 ± 0.71–70.17 ± 2.64%) and initial cell densities (0.28 ± 0.07, 10.95 ± 0.250 and 30.25 ± 0.25 g·L−1) using an unstructured – unsegregated kinetic model aiming the integration of first-and-second generation ethanol production. The method to obtain confidence region, the parameter's correlation, and the convergence of the parameters followed a pipeline previously developed by our researcher group. The mathematical models described the fermentations, and μGlu,max, μFru,max, πGlu,max, πXyl,max, ρXyl,max and ψXyl,max were the parameters with the slightest variation during the convergence process. Also, it was identified that the yeast consumed glucose and fructose simultaneously to form cell, however μGlu,max was higher relative to μFru,max in all cases (0.1909, 0.0341, 0.1815 h−1 for μGlu,max, and 1.00E-5, 2.86E-05, 2.44E-05 h−1 for μFru,max). On the other hand, πGlu,max and πFru,max were higher relative to πXyl,max.

Investigation of sugar extraction capability from rice paddy straw for potential use of bioethanol production towards energy security

ABSTRACT Over the past decades, bioethanol has emerged as an important alternative to fossil fuels. Moreover, bioethanol reduces the overall CO2 emission (greenhouse gas emission) compared to petroleum fuels as these are plant derived. Bioethanol will also provide energy security in the regions/countries where fossil fuels are in scarcity. Bioethanol is produced widely using edible resources like sugarcane, rice, and corn grains, etc. It has been a concern that the edible sources may create problem in food security. With these concerns, non-edible feedstock such as rice paddy straw and corn straw-based lignocellulose biomass has drawn tremendous attention toward the second generation (2G) ethanol production as a sustainable bioenergy source for internal combustion (IC) engine. Cellulose and hemicellulose contents are higher in biomass, which can be used as a source of reducing sugar to produce ethanol. Higher concentration of lignin fibers in the non-edible raw materials makes the sugar extraction challenging. The use of acidic medium such as hydrochloric acid (HCl) and sulfuric acid (H2SO4) makes it easier to break down the lignin fibers and enhances the sugar extraction. In this work, varying concentrations of HCl and H2SO4 were used to examine and maximize the sugar extraction from rice paddy straw. HCl was observed to provide higher yielding of sugar compared to H2SO4. Furthermore, a temperature-variation study (during the hydrolysis process) was also performed to evaluate the variation in sugar yielding with 2.0% HCl (v/v).

Modified organosolv pretreatment for improved cellulosic ethanol production from sorghum biomass

Development of an efficient pretreatment strategy to breakdown recalcitrant lignocellulosic biomass is a crucial prerequisite for commercial success of second generation ethanol production. Pretreatment using organic solvents has huge potential to release maximum sugars from the biomass. This study showed that the modified organosolv pretreatment using high boiling point glycerol solvent and ammonia as catalyst significantly improved the saccharification yield from sorghum (Sorghum bicolor (L.) Moench) biomass. The addition of ammonia as a catalyst helped in improving the xylan recovery with partial lignin removal and reduced the severity of the pretreatment process. The optimum concentrations of glycerol and ammonia for pretreatment were found to be 51.11% (w/w) and 5.14% (w/w), respectively, using response surface optimization methodology. The saccharification of biomass pretreated with the optimized concentration of solvent at 120 °C for 1 h resulted in a maximum total sugars of 421.35 mg/g. Crude glycerol, being the byproduct of biodiesel industry, could be used as a cheaper solvent for the process. The ammoniacal glycerol pretreatment of a variety of feedstocks showed high efficiency of hydrolysis of cellulose and xylan. Simultaneous hydrolysis and co-fermentation (SSCF) of the ammoniacal glycerol pretreated biomass using fed-batch strategy for 20% (w/w) solids loading gave maximum ethanol concentration of 36 g/L. Low cellulase CTec2 dose of 4 U/g solid was used to hydrolyze 20% (w/w) solids loading along with the addition of xylanase and polyethylene glycol (PEG), which gave maximum reported cellulose digestibility of 72% for sorghum biomass. Thus, ammoniacal glycerol pretreatment using crude glycerol improved the sugar and ethanol yield from sorghum biomass, benefiting both biodiesel and bioethanol industry.

Retrofitting analysis of a biorefinery: Integration of 1st and 2nd generation ethanol through organosolv pretreatment of oat husks and fungal cultivation

This study was dedicated to techno-economic analysis of an integrated 1st and 2nd generation biorefinery, where the organosolv pretreated oat husk and thin stillage is valorized through filamentous fungi and baker yeast. By this strategy, process economy can benefit from multiple value-added products including lignin (80% purity), and protein-rich biomass as feed/food ingredients. Ethanol recovery of organosolv pretreatment benefits the already existing equipment in 1st generation ethanol plant. The best results shows that the integration of 10 tons/h oat husk into a process using 18.8 tons/h grains results in increasing ethanol production from 5.2 to 7.5 tons/h, in addition to 1.6 tons/h lignin (80% purity) and 7.6 tons/h fungal biomass. Integrated process is beneficial not only for 2nd but also for 1st generation ethanol production. Selling the fungal biomass as feed and food increased the net present value (NPV) in comparison to conventional ethanol plant by 71% and 7.9-fold, respectively.

Systematic cost evaluations of biological and thermochemical processes for ethanol production from biomass residues and industrial off-gases

Bioethanol, as a sustainable fuel or as a precursor for high-value chemicals, may be produced through a variety process technologies, depending on the feedstock available. Thus, these processes are comprehensively evaluated to identify the most cost-effective process for a given feedstock, as well as cost reduction measures. Process designs for first (1G), second (2G) and third (3G) generation ethanol production were simulated in Aspen Plus® for technical evaluations, followed by economic modelling to determine the minimum ethanol selling price (MESP). 1G-ethanol from A-molasses at sugar mills was most cost-effective (MESP = 0.52US$/l). While the 1G-2G option (using sugarcane lignocelluloses) produced 98% more ethanol (MESP = 0.62US$/l), costs of enzymes were inhibitive. For 2G-ethanol using invasive alien plants, hydrolysis-fermentation had the lower MESP (0.72 US$/l) compared to gasification-fermentation because the latter had comparatively high capital costs (i.e.215vs135 million US$). Energy self-sufficiency for 3G ethanol from off-gas decreased the ethanol yield (178 to 114 l/tonne) and increased the MESPs (0.61 to 0.87 US$/l) compared to the buy-in of the required electricity. Similarly, for the gasification-fermentation scenario, a MESP of 1.58US$/l was required to obtain energy self-sufficiency. Energy self-sufficiency therefore increases process costs, but simultaneously abates the potential use of fossil fuels. Thus, it is worth pursing renewable electricity to meet process energy needs to improve ethanol yields and lower production costs. Furthermore, fermentation processes should be tailored to tolerate lower water quality requirements.

The water consumption of sugarcane bagasse post-washing after protic ionic liquid pretreatment and its impact on 2G ethanol production

Despite the water consumption of the first-generation ethanol (1G) production from sugarcane being widely studied, there are only a few experimental studies on water consumption — especially in the pulp washing — in second generation (2G) ethanol production. A quantitative evaluation of water wash consumption in the pretreatment with the protic ionic liquid (PIL) monoethanolammonium acetate [MEA][OAc] has shown that a water consumption between 600−1,000 wt% for two temperatures, 25 and 80 °C, decreased overall enzyme performance in saccharification compared to the full wash sample. The best condition in terms of high yield and low water consumption was found to be 800 wt%/80 °C, with up to 83 and 61.8 % of glucose and xylose yields against 97.9 and 85 % for the full wash sample. However, despite the full wash still presenting a superior ethanol yield, 87.4 %, the best condition with limited amount of water, 800 wt%/80 °C, also had a high ethanol yield of 86.1 %. Mass balance calculations confirmed that optimized [MEA][OAc] pretreatment with 800 wt%/80 °C and full wash conditions provided the highest ethanol yield per ton of biomass amongst several types of PIL and non-PIL pretreatments, 299 and 379 L 2G ethanol per ton of biomass, with an estimated water consumption of 56 and 647 ton, paving the way for an effective and more water-sustainable pretreatment technology for 2G ethanol production.

Diversifying the portfolio of sugarcane biorefineries: Anaerobic digestion as the core process for enhanced resource recovery

The continuous search to combine clean energy supply with the efficient exploitation of bioenergy sources is one of the most recurring efforts to meet global energy demands on an environmentally friendly basis. Sugarcane biorefineries play a central role in this context by providing sugar, ethanol and bioelectricity. However, the high energy required in ethanol production limits resource recovery efficiency in conventional sugarcane processing, motivating the investigation of approaches that maximize energetic gains. This study proposes the application of anaerobic digestion (AD) as the core processing step in sugarcane biorefineries, providing performance data for the biomethanation of juice, molasses and vinasses from different sources, namely, first generation (1G; annexed and autonomous) and second generation (2G) ethanol production. A detailed scenarization-based assessment was also carried out, comparing the proposed AD-based schemes with conventional production chains. Relatively similar performances were obtained in the experimental step, irrespective of the compositional differences of the substrates. However, the energetic potential of juice- and molasses-based methane production was at least 2-fold higher than the ones of all types of vinasses (282.81–627.84 vs. 57.10–131.52 MJ TC−1). Scenario comparison indicated the production of biogas and sugar as the most efficient energetic exploitation (94.4%) of sugars from sugarcane. Finally, the energy returned on energy invested ratio estimated for biogas-derived electricity exceeded that of ethanol production by 400%. Thus, AD-based biorefineries have great potential to meet the energy efficiency criteria of sustainable development goals in the coming decades.

Ethanol blending program in India: An economic assessment

ABSTRACT Importance of ethanol as a fuel has ever been increasing owing to its contribution to energy security, and carbon footprint reduction. India launched its ethanol fuel blending program in 2003 but the progress has lagged the targets despite various efforts. This study analyses the demand-supply gap in ethanol industry along with Government’s initiatives such as tax reforms, import policies and expansion of ethanol production in Indian context. The study evaluates viable ethanol prices in different scenarios and economic feasibility of second generation ethanol projects including and excluding social cost of carbon. To promote ethanol fuel blending, favorable taxation policies are helpful while ethanol import can only be a short term measure. Government’s initiatives and reforms are aligned in the right direction to promote ethanol fuel blending program. Further, growing value of social cost of carbon indicates importance of second generation ethanol production in India.

Unraveling continuous 2G ethanol production from xylose using hemicellulose hydrolysate and immobilized superior recombinant yeast in fixed-bed bioreactor

Development of a robust and competitive process for second generation (2G) ethanol production requires efficient fermentation of both glucose and xylose fractions generated after biomass pretreatment and saccharification, using industrial media containing high sugars concentration and inhibitors, under prolonged exposure to high ethanol titers. Thus, it is important to study the influence of these industrial operation conditions on yeast fermentation performance, which has been little addressed in the literature. In this work we evaluated the steady-state stability of continuous 2G ethanol production from xylose in a fixed bed reactor. The bioreactor was packed with recombinant, xylose-utilizing Saccharomyces cerevisiae cells entrapped in calcium alginate and it was operated with different inlet xylose concentrations and dilution rates. Medium supplementation with nutrients and scheduled washing steps were effective in maintaining high xylose conversion levels during continuous fermentation for more than 15 days with an ethanol productivity of 5.0 g/L.h. Effects of prolonged exposure to ethanol and inhibitors present in undetoxified hydrolysate were further investigated in repeated batches. Overall, the results show that improved ethanol tolerance in recombinant yeasts and innovative solutions to increase sugar concentration in the hydrolysates are the main challenges to achieve a feasible industrial process for 2 G ethanol production.

Optimization of acid-mediated delignification of corn stover, an agriculture residue carbohydrate polymer for improved ethanol production

Lignocellulose is an important carbohydrate feedstock polymer for societally-acceptable second generation ethanol production. Delignification of lignocellulose is the foremost step towards accessing the sugars that can be fermented for ethanol production. Hence, the relative efficacies of single organosolv acid pretreatments, consisting of acetic and propionic acids, for delignification of corn stover have been optimized. It was observed that amongst the pretreatments involving single organosolv agent, 40% acetic acid resulted in maximum lignin reduction. The co-pretreatment consisting of Hydrogen peroxide and acetic acid resulted in more delignification (90.2% as compared to 75.7% in case of acetic acid alone), though found to be a costlier pretreatment. On the other hand, 40% acetic acid being low-cost and with an additional advantage of acetic acid recovery through distillation offered an economical choice for organosolv pretreatment of corn stover. This work thus guides the development of a cost-effective pretreatment regime for delignification of corn stover.

Time domain NMR spectroscopy as a fast method for probing the efficiency of biomass pretreatments for second generation ethanol production

Herein we describe a simple and fast spectroscopy method based on the Time Domain Nuclear Magnetic Resonance (TD-NMR) method (or low field NMR) to determine the efficiency of lignocellulosic biomass pretreatments for increasing saccharification by enzymes, a key step in second generation (2G) ethanol production. Three different pretreatments (liquid hot water (LHW), steam explosion (SE) and steam-exploded and delignified (SED) process) were used as characteristic processes to reduce biomass recalcitrance, being the untreated and treated biomass (sugarcane bagasse) fully characterized before and after the treatments – using electron microscopy, structural techniques and the direct evaluation of commercial enzyme activity. The analyses in TD-NMR indicate that the binding mode of water (1. Shorter T2-water molecules of low mobility, which are adsorbed into the cell wall and around the lumens; 2. Intermediate T2 -looser water molecules and within small cellulose pores; 3. Longer T2-water inside larger cellulose pores and excess water outside the cellulose pores) as evinced by the technique are directly related to the ability of each process for increasing the enzymatic action in the saccharification of pretreated biomass. Given its low cost and fast acquisition time, the proposed method based in TD-NMR could be especially useful as a predictive technique for control routines in large-scale industrial production of 2G ethanol.

Liquid ammonia pretreatment optimization for improved release of fermentable sugars from sugarcane bagasse

Alkali pretreatment of biomass is a widely accepted method for efficient delignification causing significant recovery of pentoses and hexoses to be utilized for second generation ethanol production. Present study is investigated to optimize the conditions of liquid ammonia pretreatment of sugarcane bagasse using statistical design of response surface methodology with respect to liquid ammonia concentration (15–25% v/v), solid loading (5–20% w/v), temperature (70–100 °C) and retention time (16–24 h) for maximum recovery of sugars during enzymatic hydrolysis. Optimized conditions for liquid ammonia pretreatment were found as 15.64% (v/v) ammonia; 10.51% (w/v) solid loading; 84.9 °C temperature; and 23.95 h retention time. The reducing sugar yield of 545.57 ± 7.1 g/kg of raw biomass corresponding to 75.41 ± 1% of maximum theoretical sugars was achieved after 72 h of saccharification using Cellic CTec 2 (20 FPU/g pretreated biomass). Biophysical techniques further validated the efficiency of process via deeper understanding of structural and compositional changes of pretreated as well as saccharified biomass imprinted by optimized pretreatment conditions used in the study.

A differential evolution approach to estimate parameters in a temperature-dependent kinetic model for second generation ethanol production under high cell density with Spathaspora passalidarum

An unstructured–unsegregated temperature-dependent kinetic model was developed and validated to describe ethanol fermentation in a mixture of xylose and glucose for the nonconventional yeast Spathaspora passalidarum NRRL Y-27907 under high cell density in the temperature range of 26–32 °C. The kinetic model consisted of 13 equations and 16 kinetic parameters, describing cell growth, individual xylose and glucose uptake and product formation. Global parametric estimation was executed through a differential evolution algorithm. Temperature-dependent parameters were identified and adjusted to Arrhenius-type equations as a function of temperature. The overall r2 of the process calibration and validation were 0.972 and 0.959, respectively, indicating that the model satisfactorily described the process in the temperature range investigated. Furthermore, using a 3D projection of the model to simulate ethanol production, it was concluded that temperatures between 30 and 32 °C resulted in the highest productivities.

Agave: A promising feedstock for biofuels in the water-energy-food-environment (WEFE) nexus

The aim of this study was to conduct the first comprehensive life cycle assessment and economic analysis on ethanol produced from agave. Compositional and field data from a field experiment in Queensland, Australia was used. Our study shows that ethanol yields from agave (7414 L/ha/year) are comparable to Brazilian sugarcane (9900/L/ha/year) and higher than US corn ethanol (3800/L/ha/year). Furthermore, agave outperforms current first generation biofuel crops in water-related impacts, including Freshwater Eutrophication (96% lower than corn and 88% lower than sugarcane), Marine Ecotoxicity (59% lower than corn and 53% lower than sugarcane) and Water Consumption (46% lower than corn and 69% lower than sugarcane). The life cycle fossil energy use (Fossil Resource Scarcity) for agave is 58% lower than corn and 6% higher than sugarcane. The Global Warming impact for agave is also 62% and 30% lower than that of corn and sugarcane, respectively. Although its Land Use impact, measured by land occupied per unit ethanol output, is 98% higher than corn and 2% higher than sugarcane, agave can be grown on arid land that is not suitable for food crops. The economic analysis suggests that first generation ethanol production from agave is not commercially viable without government support. Overall, the results show that agave is promising for biofuel production in the water-energy-food-environment context.