Generation Ethanol Research Articles

Fed-batch strategies for saccharification of pilot-scale mild-acid and alkali pretreated sugarcane bagasse: Effects of solid loading and surfactant addition

High-solid enzymatic hydrolysis of lignocellulosic biomass is a key approach for high titer and reduced downstream costs in second generation ethanol production. Combining a pilot-scale (80 L reactor) mild acid pretreatment and an alkali pretreatment of sugarcane bagasse (SCB) with fed-batch strategies for high-solid enzymatic hydrolysis, more than 150 g/L of glucose was found in the hydrolysate. The best result of the fed-batch study (2.03 g/L/h of glucose productivity) was obtained with a total solids content of 27%w/w (being 20%w/w of solids added at 0 h), and the addition of the total amount of the non-ionic surfactant PEG 4000 and the enzymes solely at the beginning of the reaction. A semi-simultaneous saccharification and fermentation strategy of the pretreated SCB (with the yeast inoculum occurring after 12 h of a single hydrolysis stage at most proper conditions for the cellulases) resulted in 62 g/L of ethanol after 48 h, and a productivity of up to 6.6 g/L/h. The strategy here reported indicates that it is possible to achieve ethanol titers suitable for industrial distilleries avoiding mass transfer limitations that incur in operational problems during high-solid enzymatic hydrolysis.

Assessment of bagasse and trash utilization for ethanol production: A case study in india

Retrofitting existing sugar mills to produce ethanol from sugarcane bagasse provides a significant opportunity in India to meet the nation's liquid transportation fuel demands. Utilization of sugarcane trash in the sugar mill can enhance the economic feasibility of this approach. This work developed an optimization model to determine the optimal distribution of bagasse and trash for ethanol production while simultaneously ensuring energy sufficiency of the sugar mill. A superstructure of sugar mill integrated with a second generation ethanol facility along with trash utilization and lignin valorization processes is developed. The model determines the break‐even selling price (BESP) of ethanol by optimizing the distribution of bagasse and trash subjected to the mass and energy balance constraints and cost functions. The application of the model for a sugar mill with a throughput of 150 Mg (Mega grams)/h of sugarcane showed the ethanol BESP to be Rs. 63/L when trash and lignin was available along with bagasse for heat production. Trash retention on farm increased the BESP to Rs. 117/L, indicating the economic value of trash utilization. However, on‐farm trash retention led to about 82% savings in GHG emissions due to reduced fertilizer use. Lignin valorization was found to be economically infeasible. © 2018 American Institute of Chemical Engineers Environ Prog, 37: 1901–1907, 2018

Thermodynamic and economic evaluation of reheat and regeneration alternatives in cogeneration systems of the Brazilian sugarcane and alcohol sector

This work makes a technical and economic evaluation of incorporation of reheating and regeneration, as a way to increase efficiency of energetic systems and bagasse surplus, in cogeneration systems of Brazilian sugar and ethanol sector. Four scenarios were analyzed: Conventional (C0), with Reheat (C1), Regenerative (C2) and with Reheat and Regeneration (C3). Some of thermodynamic indicators used in evaluation were Surplus Bagasse Index and Exergetic Efficiency, for economic evaluation the Monte Carlo Method was used to give a Net Present Value (NPV) > 0 for each scenario. Technical evaluation indicates that Reheating (C1) increases bagasse surplus by 39.9% and exergetic efficiency by 1.90%, with respect to C0. Incorporation of 1–8 regenerators (C2) increases surplus bagasse and exergetic efficiency in the ranges of 103–160% and 5.03–8.07%, respectively. Reheat stage incorporation of 1–8 regenerators (C3) increases surplus bagasse in the range of 121–166% and increases exergetic efficiency in a range of 5.91–8.46%. Finally, it was estimated the potential of additional electric power generation during off-season and second generation ethanol production from surplus bagasse, with satisfactory results.

Energy assessment of second generation (2G) ethanol production from wheat straw in Indian scenario.

Impact of second-generation ethanol (2G) use in transportation sector mainly depends upon energy efficiency of entire production process. The objective of present study was to determine energy efficiency of a potential lignocellulosic feedstock; wheat straw and its conversion into cellulosic ethanol in Indian scenario. Energy efficiency was determined by calculating Net energy ratio (NER), i.e. ratio of output energy obtained by ethanol and input energy used in ethanol production. Energy consumption and generation at each step is calculated briefly (11,837.35MJ/ha during Indian dwarf irrigated variety of wheat crop production and 7.1148MJ/kg straw during ethanol production stage). Total energy consumption is calculated as 8.2988MJ/kg straw whereas energy generation from ethanol is 15.082MJ/kg straw; resulting into NER >1. Major portion of agricultural energy input is contributed by diesel and fertilisers whereas refining process of wheat straw feedstock to ethanol and by-products require mainly in the form of steam and electricity. On an average, 1671.8kg water free ethanol, 930kg lignin rich biomass (for combustion), and 561kg C5-molasses (for fodder) per hectare are produced. Findings of this study, net energy ratio (1.81) and figure of merit (14.8028MJ/nilkg carbon) proves wheat straw as highest energy efficient lignocellulosic feedstock for the country.

O aumento da produtividade e a busca pela excelência na produção do etanol brasileiro: uma história de sucesso

Atualmente, o Brasil é líder quando o assunto é produtividade na obtenção de etanol. Os avanços na tecnologia de produção deste biocombustível foram impulsionados por fatores mundiais e nacionais. Um desses fatores foi a criação do Programa Nacional do Álcool (Proálcool) pelo governo federal em 1973. A partir daí, os pesquisadores brasileiros começaram os estudos de otimização da cadeia produtiva que levaram o país a se destacar no cenário internacional. Os principais resultados foram: i) aumento, de 73%, na produtividade agrícola; redução, de 77%, no tempo de fermentação; e aumento, de 44 vezes, na produção anual de etanol; ii) autossuficiência e venda da energia elétrica produzida pela queima do bagaço; iii) menor custo de produção de etanol quando comparado com o custo de produção norte americano. A partir de 2010, os ganhos em produtividade foram pequenos, mesmo com a grande produção científica. Para que o Brasil continue ocupando os altos patamares no ranking mundial de produtores de etanol, será necessário: i) buscar a viabilidade econômica da produção de etanol de segunda geração; ii) transformar as usinas em biorrefinarias para converter o etanol em moléculas de maior valor agregado.

Ethanol production from Dekkera bruxellensis in synthetic media with pentose

Abstract Ethanol is obtained in Brazil from the fermentation of sugarcane, molasses or a mixture of these. Alternatively, it can also be obtained from products composed of cellulose and hemicellulose, called “second generation ethanol - 2G”. The yeast Saccharomyces cerevisiae, commonly applied in industrial ethanol production, is not efficient in the conversion of pentoses, which is present in high amounts in lignocellulosic materials. This study aimed to evaluate the ability of a yeast strain of Dekkera bruxellensis in producing ethanol from synthetic media, containing xylose or arabinose, xylose and glucose as the sole carbon sources. The results indicated that D. bruxellensis was capable of producing ethanol from xylose and arabinose, with ethanol concentration similar for both carbon sources, 1.9 g L-1. For the fermentations performed with xylose and glucose, there was an increase in the concentration of ethanol to 5.9 g L-1, lower than the standard yeast Pichia stipitis (9.3 g L-1), but with similar maximum yield in ethanol (0.9 g g TOC-1). This proves that the yeast D. bruxellensis produced lower amounts of ethanol when compared with P. stipitis, but showed that is capable of fermenting xylose and can be a promising alternative for ethanol conversion from hydrolysates containing glucose and xylose as carbon source.

Thermo-Biorrefineries: A promising concept for production of bio-electricity, 2nd generation ethanol and renewable chemicals in Portugal

Thermo-Biorrefineries: A promising concept for production of bio-electricity, 2nd generation ethanol and renewable chemicals in Portugal

English

The increased supply of ethanol fuel and its spread as an alternative to fossil fuels depend on the exploration of biomasses that can be regarded as alternatives to sugarcane and maize. In this study, the agricultural productivity and the potential for production of ethanol from roots and the aerial portion of twenty sweet potato genotypes were evaluated. The roots and branches were harvested 180 days after planting. Starch, hemicellulose, cellulose, lignin and soluble sugars from sweet potato roots or branches were determined and expressed as percentage of dry matter produced per hectare. The genotype UFVJM 28 stood out for the production of root and branches (fresh material), yielding 43.5 and 31.7 t ha-1, respectively. The roots of the Palmas, Batata Mandioca, Cariru Vermelha and UFVJM 45 genotypes had the highest total soluble sugar concentrations, between 4.1 and 5.4%. The enzymatic digestibility for starch contained in the roots ranged from 58.2 to 91.2%, and when related to the cellulose contained in the branches, it ranged from 14.2 to 42.4%. The estimates for the production of ethanol from the roots ranged between 1120 and 4940 L ha-1. The estimated production of bioethanol from sweet potato branches of the genotypes varied from 240 to 995 L ha-1. Considering the combined use of roots and branches, at least four sweet potatoes genotypes presented a potential for ethanol production greater than 4000 L ha-1 in a 180-day cycle. Key words: Ipomoea batatas, ethanol, biofuels, second generation ethanol, starch.

Steam reforming of ethanol on Rh/SiCeO2 washcoated monolith catalyst: Stable catalyst performance

The performance of a new Rh/CeSiO2 catalyst supported on a ceramic monolith for steam reforming (SR) of ethanol for hydrogen generation was investigated. It provides several advantages over a traditional pellet based catalyst in that it will reduce weight, size and pressure drop in the reactor. The effect of steam to ethanol molar ratio and temperature were first investigated on a powdered catalyst in order to establish the preferred reaction conditions to be used for tests on the monolith. The optimum temperature for coke free, high selectivity and stable catalyst operation was 1073 K at a steam to ethanol molar ratio of 3.5. The monolith supported catalyst was evaluated for aging stability, on/off performance and coke regeneration using steam gasification. After 96 h of SR of ethanol at 1028 K and water/ethanol molar ratio of 3.5 the monolith supported catalyst retained stable performance throughout the entire time on stream with the only products being H2, CO, CO2. Some coke formation was observed using Raman spectra, however, it did not cause any permanent deactivation. Regeneration via steam gasification at 973 K with 20% steam in N2 was successful for coke removal and complete catalyst regeneration.

Does straw mulch partial-removal from soil interfere in yield and industrial quality sugarcane? A long term study

Sugarcane straw mulch left in the field after its mechanical harvest has become very valuable raw material for second generation ethanol and bioelectricity production. However, little information is available on how much straw mulch is needed to be left in the field so that agricultural productivity is not affected and high sustainability is provided for the bioenergy production system. The objective of this work was to evaluate the productivity and industrial quality of sugarcane after five years of cultivation when different amount of straw mulch is removed from the field. The experiment was installed in clay texture Eutroferric Red Latosol (Oxisol). Six treatments were evaluated: 0%, 25% (5tha−1), 50% (10tha−1), 75% (15tha−1), 100% (20tha−1) of straw mulch and burnt cane harvesting (where 100% of the straw mulch was burned). Evaluated parameters included sugarcane productivity (tons/hectare) and its industrial quality (Pol, soluble solids (°Brix), apparent purity and total sugars (TS)). Productivity was calculated at the end of the cycle whereas industrial quality parameters were evaluated during three phases i.e. 180, 240 and 350days after cutting (DAC). Straw mulch of 50 and 75% were statistically at par with each other but resulted in higher sugarcane production with 47% more productivity as compared to 0 and 25% of straw mulch as well as burned cane harvesting. Straw mulch didn’t affect the industrial quality; however, higher sugar production was supported by higher agricultural productivity, under low moisture condition. It is possible to remove 50% of straw mulch from the field for the production of second generation ethanol or bioelectricity, without any damage to the crop.

Integrated bioethanol production to boost low-concentrated cellulosic ethanol without sacrificing ethanol yield

Four integrated designs were proposed to boost cellulosic ethanol titer and yield. Results indicated co-fermentation of corn flour with hydrolysate liquor from saccharified corn stover was the best integration scheme and able to boost ethanol titers from 19.9 to 123.2 g/L with biomass loading of 8% and from 36.8 to 130.2 g/L with biomass loadings of 16%, respectively, while meeting the minimal ethanol distillation requirement of 40 g/L and achieving high ethanol yields of above 90%. These results indicated integration of first and second generation ethanol production could significantly accelerate the commercialization of cellulosic biofuel production. Co-fermentation of starchy substrate with hydrolysate liquor from saccharified biomass is able to significantly enhance ethanol concentration to reduce energy cost for distillation without sacrificing ethanol yields. This novel method could be extended to any pretreatment of biomass from low to high pH pretreatment as demonstrated in this study.

New Method for Carbohydrates Determination in Sugarcane Bagasse by HPAEC‐RPAD Using Glassy Carbon Electrode Modified with Carbon Nanotubes and Nickel Nanoparticles

AbstractSecond generation ethanol can be produced from carbohydrates released from both sugarcane bagasse cell wall and sugarcane straw. The development of new method for the analysis of carbohydrates is, in this sense, seen as extremely relevant in the area of bioenergy. Based on the above considerations, the scope of this work encompasses the identification and quantification of carbohydrates composition in sugarcane bagasse without the need of sample derivatization, developing a novel analytical method using a glassy carbon electrode modified with multi‐walled carbon nanotubes containing nickel oxyhydroxide nanoparticles (GCE/MWCNT/NiOOH) and applying the modified electrode as a detector in HPAEC (High Performance Anion‐Exchange Chromatography) with reverse pulsed amperometric detection (RPAD) towards the determination of arabinose, galactose, glucose and xylose in hydrolyzed sugarcane bagasse. The carbohydrates concentrations determined in the hydrolyzed sugarcane bagasse were 6.1×10−4 mol L−1, 1.0×10−2 mol L−1 and 2.8×10−3 mol L−1 for arabinose, glucose, and xylose respectively. Our results showed that the present method is, in essence, attractive for analysis in the course of the production process of second generation ethanol production in that it does not require sample derivatization, has rapid run time, satisfactory separation, and can be used for the detection of carbohydrates without the interference of other electroactive species.

Fast spectroscopic monitoring of inhibitors in the 2G ethanol process

One of the main challenges of second generation (2G) ethanol production is the high quantities of phenolic compounds and furan derivatives generated in the pretreatment of the lignocellulosic biomass, which inhibit the enzymatic hydrolysis and fermentation steps. Fast monitoring of these inhibitory compounds could provide better control of the pretreatment, hydrolysis, and fermentation processes by enabling the implementation of strategic process control actions. We investigated the feasibility of monitoring these inhibitory compounds by ultraviolet–visible (UV–Vis) spectroscopy associated with partial least squares (PLS) regression. Hydroxymethylfurfural, furfural, vanillin, and ferulic and p-coumaric acids generated during different severities of liquid hot water pretreatment of sugarcane bagasse were quantified with highly accuracy. In cross-validation (leave-one-out), the PLS-UV–Vis method presented root mean square error of prediction (RMSECV) of around only 5.0%. The results demonstrated that the monitoring performance achieved with PLS-UV–Vis could support future studies of optimization and control protocols for application in industrial processes.

Process integration of a multiperiod sugarcane biorefinery

Process integration in sugarcane biorefineries allows reducing steam consumption. As a consequence, the bagasse surplus can be diverted to second generation ethanol production. Furthermore, sugarcane plants can vary the production of ethanol and electricity, depending on the demand. For those reasons, equipment present in the plant might be required to operate under different conditions. This study presents the energy integration of a sugarcane biorefinery. A Mixed Integer Nonlinear Programming (MINLP) optimization model is proposed to solve the problem of synthesizing a Heat Exchanger Network (HEN) able to periodically operate under the distinct conditions required in the biorefinery, i.e., a multiperiod HEN. For solving the MINLP problem, a hybrid metaheuristic approach was used, which combines Simulated Annealing and Rocket Fireworks Optimization. The proposed strategy achieved lower HEN total annualized cost (TAC) when compared with the project energy integration that is commonly found in Brazilian plants. This reduction in TAC, in particular in utilities demand, allows the surplus bagasse to be available for the most suitable application: produce 2G ethanol or more electricity.

Integrated production of second generation ethanol and lactic acid from steam-exploded elephant grass

Elephant grass was subjected to steam explosion to enhance cellulose accessibility and convert it into ethanol. After catalyzed pretreatment at 190 °C for 5 min, enzymatic hydrolysis was carried out using high rate of solid loading combined with different enzyme dosages. Assays employing 20% (w/v) solids loading and an enzyme dosage of 20 FPU g−1 substrate led to a yield of 86.02 g glucose released per 100 g potential glucose in the water insoluble solids. This condition was selected to carry out the simultaneous saccharification and fermentation procedure through S. cerevisiae CAT-1, producing 42.25 g L−1 ethanol with a yield of 74.57% regard to the maximum theoretical. The liquor containing C5 and C6-sugars was successfully converted into lactic acid using L. buchneri NRRL B-30929, resulting in 13.35 g L−1 with a yield of 68.21% in relation to the maximum theoretical.

The potential of agricultural banana waste for bioethanol production

Banana is one of the most important fruit crops around the world. After harvesting, it generates large amounts of lignocellulosic residues that could be used for second generation ethanol production. Optimal operating conditions of saccharification and fermentation processes, of the two main agricultural wastes of banana crop: pseudostem and rachis, for bioethanol production were selected in order attain conditions transferable to industry (optimizing resources and time). Both materials were previously pretreated with acid-catalyzed steam explosion. Full factorial experimental design was used in order to determine enzymatic hydrolysis process conditions to obtain glucose concentrations between 75 and 100 g.L−1. Optimal enzymatic hydrolysis conditions for rachis and pseudostem were 17.6% of solid loading and 16.0 FPU.g−1 glucan of enzyme dosage and 15.1% of solid loading and 14.9 FPU.g−1 glucan of enzyme dosage, respectively. The most suitable configuration to attain the highest volumetric ethanol productivity for rachis was 8 h prehydrolysis followed by a Simultaneous Saccharification and Fermentation (PSSF 8 h). Meanwhile, for pseudostem, higher ethanol production was obtained in Simultaneous Saccharification and Fermentation (SSF) configuration. At optimized conditions, pseudostem reached 112 L.t−1 of ethanol, and rachis 103 L.t−1. These conditions led to achieve ethanol production process at high solid loading, low enzyme dosage, low yeast inoculum, no mineral salts supplementation and maximum ethanol productivities.

Changes in carbon footprint when integrating production of filamentous fungi in 1st generation ethanol plants

Integrating the cultivation of edible filamentous fungi in the thin stillage from ethanol production is presently being considered. This integration can increase the ethanol yield while simultaneously producing a new value-added protein-rich biomass that can be used for animal feed. This study uses life cycle assessment to determine the change in greenhouse gas (GHG) emissions when integrating the cultivation of filamentous fungi in ethanol production. The result shows that the integration performs better than the current scenario when the fungal biomass is used as cattle feed for system expansion and when energy allocation is used. It performs worse if the biomass is used as fish feed. Hence, integrating the cultivation of filamentous fungi in 1st generation ethanol plants combined with proper use of the fungi can lead to a reduction of GHG emissions which, considering the number of existing ethanol plants, can have a significant global impact.

Life cycle assessment of second generation ethanol derived from banana agricultural waste: Environmental impacts and energy balance

Biofuels are considered as an alternative to partially replace fossil fuels and mitigate climate change effects. A life cycle assessment of second generation ethanol, derived from banana agricultural wastes, was developed to assess its environmental sustainability and demonstrate its capacity of reducing greenhouse gas emissions. The methodological approach was conducted in a Well-to-Wheel perspective, using as functional unit 1 MJ of energy released in the combustion of bioethanol in a passenger car from different bioethanol blends. Primary and secondary information sources were used for the assessment; mass balance and ethanol yield data came from laboratory experimentation. The environmental assessment was carried out using SimaPro 8.0.4.30 with the ReCiPe midpoint (H) impact assessment methodology. The quantified impact categories were climate change (CC), terrestrial acidification (TA), freshwater eutrophication (FE), photochemical oxidant formation (PO), particulate matter formation (PM), and fossil depletion (FD). In addition, net energy value and energy ratio (ER) were analyzed to ensure a positive energy balance. Compared to using pure gasoline, blended gasoline reduced CC, PO, PM, and FD impacts, but increased FE and TA impacts. The obtained energy balance was positive, with an ER of 2.68 MJ/MJ. Wastewater treatment is the process that presented the greatest energy consumption. Since Ecuador is the world's largest exporter of bananas, and a great amount of agricultural waste is available, a case study in this country was analyzed. This case study indicated that Ecuador could use banana residue for ethanol production, considering its positive and negative impacts. In conclusion, second generation ethanol derived from banana agricultural waste has potential to reduce greenhouse gas emissions and fossil depletion and has a positive energy balance.

Characterization of the pre-treated biomass of Eichhornia crassipes (water hyacinth) for the second generation ethanol production

ABSTRACTEichhornia crassipes (water hyacinth), is considered an aquatic pest. An alternative to solve the excess water hyacinth problem is to use the biomass for second generation ethanol. This process can be divided into: collection of biomass pre-treatment, enzymatic hydrolysis, fermentation and distillation. Some chemical processes for pre-treatment of biomass water hyacinths were evaluated to determine which procedure degrades the greater amount of lignin and hemicellulose which least affects the cellulose. Characterization was made from the analysis techniques: TG-DTA, XRD and FTIR. The results revealed that the biomass to water hyacinth the most efficient pre-treatment is chemical hydrolysis with sulfuric acid.

New Protocol Based on UHPLC-MS/MS for Quantitation of Metabolites in Xylose-Fermenting Yeasts.

Xylose fermentation is a bottleneck in second-generation ethanol production. As such, a comprehensive understanding of xylose metabolism in naturally xylose-fermenting yeasts is essential for prospection and construction of recombinant yeast strains. The objective of the current study was to establish a reliable metabolomics protocol for quantification of key metabolites of xylose catabolism pathways in yeast, and to apply this protocol to Spathaspora arborariae. Ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS) was used to quantify metabolites, and afterwards, sample preparation was optimized to examine yeast intracellular metabolites. S. arborariae was cultivated using xylose as a carbon source under aerobic and oxygen-limited conditions. Ion pair chromatography (IPC) and hydrophilic interaction liquid chromatography-tandem mass spectrometry (HILIC-MS/MS) were shown to efficiently quantify 14 and 5 metabolites, respectively, in a more rapid chromatographic protocol than previously described. Thirteen and eleven metabolites were quantified in S. arborariae under aerobic and oxygen-limited conditions, respectively. This targeted metabolomics protocol is shown here to quantify a total of 19 metabolites, including sugars, phosphates, coenzymes, monosaccharides, and alcohols, from xylose catabolism pathways (glycolysis, pentose phosphate pathway, and tricarboxylic acid cycle) in yeast. Furthermore, to our knowledge, this is the first time that intracellular metabolites have been quantified in S. arborariae after xylose consumption. The results indicated that fine control of oxygen levels during fermentation is necessary to optimize ethanol production by S. arborariae. The protocol presented here may be applied to other yeast species and could support yeast genetic engineering to improve second generation ethanol production. Graphical Abstract ᅟ.