Simulation of integrated first and second generation bioethanol production from sugarcane: comparison between different biomass pretreatment methods

Polymers without Petrochemicals: Sustainable Routes to Conventional Monomers

Access to a wide range of plastic materials has been rationalized by the increased demand from growing populations and the development of high-throughput production systems. Plastic materials at low costs with reliable properties have been utilized in many everyday products. Multibillion-dollar companies are established around these plastic materials, and each polymer takes years to optimize, secure intellectual property, comply with the regulatory bodies such as the Registration, Evaluation, Authorisation and Restriction of Chemicals and the Environmental Protection Agency and develop consumer confidence. Therefore, developing a fully sustainable new plastic material with even a slightly different chemical structure is a costly and long process. Hence, the production of the common plastic materials with exactly the same chemical structures that does not require any new registration processes better reflects the reality of how to address the critical future of sustainable plastics. In this review, we have highlighted the very recent examples on the synthesis of common monomers using chemicals from sustainable feedstocks that can be used as a like-for-like substitute to prepare conventional petrochemical-free thermoplastics.

Biochemical biorefinery: A low-cost and non-waste concept for promoting sustainable circular bioeconomy

The transition from a fossil-based linear economy to a circular bioeconomy is no longer an option but rather imperative, given worldwide concerns about the depletion of fossil resources and the demand for innovative products that are ecocompatible. As a critical component of sustainable development, this discourse has attracted wide attention at the regional and international levels. Biorefinery is an indispensable technology to implement the blueprint of the circular bioeconomy. As a low-cost, non-waste innovative concept, the biorefinery concept will spur a myriad of new economic opportunities across a wide range of sectors. Consequently, scaling up biorefinery processes is of the essence. Despite several decades of research and development channeled into upscaling biorefinery processes, the commercialization of biorefinery technology appears unrealizable. In this review, challenges limiting the commercialization of biorefinery technologies are discussed, with a particular focus on biofuels, biochemicals, and biomaterials. To counteract these challenges, various process intensification strategies such as consolidated bioprocessing, integrated biorefinery configurations, the use of highly efficient bioreactors, simultaneous saccharification and fermentation, have been explored. This study also includes an overview of biomass pretreatment-generated inhibitory compounds as platform chemicals to produce other essential biocommodities. There is a detailed examination of the technological, economic, and environmental considerations of a sustainable biorefinery. Finally, the prospects for establishing a viable circular bioeconomy in Nigeria are briefly discussed.

Comparison of Spathaspora passalidarum and recombinant Saccharomyces cerevisiae for integration of first- and second-generation ethanol production

First-generation ethanol (E1G) is based on the fermentation of sugars released from saccharine or starch sources, while second-generation ethanol (E2G) is focused on the fermentation of sugars released from lignocellulosic feedstocks. During the fractionation process to release sugars from hemicelluloses (mainly xylose), some inhibitor compounds are released hindering fermentation. Thus, the biggest challenge of using hemicellulosic hydrolysate is selecting strains and processes able to efficiently ferment xylose and tolerate inhibitors. With the aim of diluting inhibitors, sugarcane molasses (80% of sucrose content) can be mixed to hemicellulosic hydrolysate in an integrated E1G-E2G process. Cofermentations of xylose and sucrose were evaluated for the native xylose consumer Spathaspora passalidarum and a recombinant Saccharomyces cerevisiae strain. The industrial S. cerevisiae strain CAT-1 was modified to overexpress the XYL1, XYL2 and XKS1 genes and a mutant ([4-59Δ]HXT1) version of the low-affinity HXT1 permease, generating strain MP-C5H1. Although S. passalidarum showed better results for xylose fermentation, this yeast showed intracellular sucrose hydrolysis and low sucrose consumption in microaerobic conditions. Recombinant S. cerevisiae showed the best performance for cofermentation, and a batch strategy at high cell density in bioreactor achieved unprecedented results of ethanol yield, titer and volumetric productivity in E1G-E2G production process.

Cellulosic and hemicellulosic fractions of sugarcane bagasse: Potential, challenges and future perspective

Sugarcane bagasse is a rich source of cellulose (32-45%), hemicellulose (20-32%) and lignin (17-32%), 1.0-9.0% ash and some extractives. Huge amount of the generation of sugarcane bagasse has been a great challenge to industries and environment at global level for many years. Though cellulosic and hemicellulosic fractions in bagasse makes it a potential raw substrate for the production of value-added products at large scale, the presence of lignin hampers its saccharification which further leads to low yields of the value-added products. Therefore, an appropriate pretreatment strategy is of utmost importance that effectively solubilizes the lignin that exposes cellulose and hemicellulose for enzymatic action. Pretreatment also reduces the biomass recalcitrance i.e., cellulose crystallinity, structural complexity of cell wall and lignification for its effective utilization in biorefinery. Sugarcane bagasse served as nutrient medium for the cultivation of diverse microorganisms for the production of industrially important metabolites including enzymes, reducing sugars, prebiotic, organic acids and biofuels. Sugarcane bagasse has been utilized in the generation of electricity, syngas and as biosorbant in the bioremediation of heavy metals. Furthermore, the ash generated from bagasse is an excellent source for the synthesis of high strength and light weight bricks and tiles. Present review describes the utility of sugarcane bagasse as sustainable and renewable lignocellulosic substrate for the production of industrially important multifarious value-added products.

Biomass Accumulation and Cell Wall Structure of Rice Plants Overexpressing a Dirigent-Jacalin of Sugarcane (ShDJ) Under Varying Conditions of Water Availability

A sugarcane gene encoding a dirigent-jacalin, ShDJ, was induced under drought stress. To elucidate its biological function, we integrated a ShDJ-overexpression construction into the rice Nipponbare genome via Agrobacterium-mediated transformation. Two transgenic lines with a single copy gene in T₀ were selected and evaluated in both the T₁ and T₄ generations. Transgenic lines had drastically improved survival rate under water deficit conditions, at rates close to 100%, while WT did not survive. Besides, transgenic lines had improved biomass production and higher tillering under water deficit conditions compared with WT plants. Reduced pectin and hemicellulose contents were observed in transgenic lines compared with wild-type plants under both well-watered and water deficit conditions, whereas cellulose content was unchanged in line #17 and reduced in line #29 under conditions of low water availability. Changes in lignin content under water deficit were only observed in line #17. However, improvements in saccharification were found in both transgenic lines along with changes in the expression of OsNTS1/2 and OsMYB58/63 secondary cell wall biosynthesis genes. ShDJ-overexpression up-regulated the expression of the OsbZIP23, OsGRAS23, OsP5CS, and OsLea3 genes in rice stems under well-watered conditions. Taken together, our data suggest that ShDJ has the potential for improving drought tolerance, plant biomass accumulation, and saccharification efficiency.

Ethanol Production from Waste of Cassava Processing

Cassava processing produces by-products such as brown bark, between bark, disposal, bran, fiber and bagasse. Cassava bagasse is characterized as a source of starch that can be converted into sugars to obtain biofuels. The objective of this work was to produce ethanol from this cassava processing residue and to evaluate its contribution potential in the Brazilian energy matrix. Cassava processing residues were obtained from four different starch manufacturers in Brazil. Analysis of the chemical compositions of these samples provided the content of starch, sugar, crude grease, moisture, ash and also their pH values. For the ethanol process, the samples were submitted to enzymatic hydrolysis using the alpha-amylase and amyloglucosidases enzymes, followed by fermentation and distillation. The samples showed high starch indices, approximately 64% on average. The average yield of ethanol obtained was 30% after treatment of the sample like this. Considering the estimated volume of cassava bagasse in Brazil, it is possible to produce an average of 789 million cubic meters per bagasse, replacing about 24% of the first generation ethanol. Cassava bagasse can be considered an interesting biomass for the production of biofuels, contributing to the expansion of the energy matrix.

Lignocellulose integration to 1G-ethanol process using filamentous fungi: fermentation prospects of edible strain of Neurospora intermedia

Background

Integration of first- and second-generation ethanol processes is one among the alternate approaches that efficiently address the current socio-economic issues of the bioethanol sector. Edible filamentous fungus capable of utilizing pentoses from lignocelluloses and also possessing biomass application as potential animal feed component was used as the fermentation strain for the integration model. This study presents various fermentation aspects of using edible filamentous fungi in the integrated first and second generation ethanol process model.

Results

Fermentation of edible strain of N. intermedia on the integrated first and second-generation ethanol substrate (the mixture of dilute acid pretreated and enzymatically hydrolyzed wheat straw and thin stillage from the first-generation ethanol process), showed an ethanol yield maximum of 0.23 ± 0.05 g/g dry substrate. The growth of fungal pellets in presence of fermentation inhibitors (such as acetic acid, HMF and furfural) resulted in about 11 to 45% increase in ethanol production as compared to filamentous forms, at similar growth conditions in the liquid straw hydrolysate. Fungal cultivations in the airlift reactor showed strong correlation with media viscosity, reaching a maximum of 209.8 ± 3.7 cP and resulting in 18.2 ± 1.3 g/L biomass during the growth phase of fungal pellets.

Conclusion

N. intermedia fermentation showed high sensitivity to the dilute acid lignocellulose pretreatment process, with improved fermentation performance at milder acidic concentrations. The rheological examinations showed media viscosity to be the most critical factor influencing the oxygen transfer rate during the N. intermedia fermentation process. Mycelial pellet morphology showed better fermentation efficiency and high tolerance towards fermentation inhibitors.

In planta production and characterization of a hyperthermostable GH10 xylanase in transgenic sugarcane

Sugarcane (Saccharum sp. hybrids) is one of the most efficient and sustainable feedstocks for commercial production of fuel ethanol. Recent efforts focus on the integration of first and second generation bioethanol conversion technologies for sugarcane to increase biofuel yields. This integrated process will utilize both the cell wall bound sugars of the abundant lignocellulosic sugarcane residues in addition to the sucrose from stem internodes. Enzymatic hydrolysis of lignocellulosic biomass into its component sugars requires significant amounts of cell wall degrading enzymes. In planta production of xylanases has the potential to reduce costs associated with enzymatic hydrolysis but has been reported to compromise plant growth and development. To address this problem, we expressed a hyperthermostable GH10 xylanase, xyl10B in transgenic sugarcane which displays optimal catalytic activity at 105 °C and only residual catalytic activity at temperatures below 70 °C. Transgene integration and expression in sugarcane were confirmed by Southern blot, RT-PCR, ELISA and western blot following biolistic co-transfer of minimal expression cassettes of xyl10B and the selectable neomycin phosphotransferase II. Xylanase activity was detected in 17 transgenic lines with a fluorogenic xylanase activity assay. Up to 1.2% of the total soluble protein fraction of vegetative progenies with integration of chloroplast targeted expression represented the recombinant Xyl10B protein. Xyl10B activity was stable in vegetative progenies. Tissues retained 75% of the xylanase activity after drying of leaves at 35 °C and a 2 month storage period. Transgenic sugarcane plants producing Xyl10B did not differ from non-transgenic sugarcane in growth and development under greenhouse conditions. Sugarcane xylan and bagasse were used as substrate for enzymatic hydrolysis with the in planta produced Xyl10B. TLC and HPLC analysis of hydrolysis products confirmed the superior catalytic activity and stability of the in planta produced Xyl10B with xylobiose as a prominent degradation product. These findings will contribute to advancing consolidated processing of lignocellulosic sugarcane biomass.

Reference genes for normalization of qPCR assays in sugarcane plants under water deficit

BACKGROUND

Sugarcane (Saccharum spp.) is the main raw material for sugar and ethanol production. Among the abiotic stress, drought is the main one that negatively impact sugarcane yield. Although gene expression analysis through quantitative PCR (qPCR) has increased our knowledge about biological processes related to drought, gene network that mediates sugarcane responses to water deficit remains elusive. In such scenario, validation of reference gene is a major requirement for successful analyzes involving qPCR.

RESULTS

In this study, candidate genes were tested for their suitable as reference genes for qPCR analyses in two sugarcane cultivars with varying drought tolerance. Eight candidate reference genes were evaluated in leaves sampled in plants subjected to water deficit in both field and greenhouse conditions. In addition, five genes were evaluated in shoot roots of plants subjected to water deficit by adding PEG8000 to the nutrient solution. NormFinder and RefFinder algorithms were used to identify the most stable gene(s) among genotypes and under different experimental conditions. Both algorithms revealed that in leaf samples, UBQ1 and GAPDH genes were more suitable as reference genes, whereas GAPDH was the best reference one in shoot roots.

CONCLUSION

Reference genes suitable for sugarcane under water deficit were identified, which would lead to a more accurate and reliable analysis of qPCR. Thus, results obtained in this study may guide future research on gene expression in sugarcane under varying water conditions.

Nitrogen Sources Screening for Ethanol Production Using Carob Industrial Wastes

Nowadays, bioethanol production is one of the most important technologies by the necessity to identify alternative energy resources, principally when based on inexpensive renewable resources. However, the costs of 2nd-generation bioethanol production using current biotechnologies are still high compared to fossil fuels. The feasibility of bioethanol production, by obtaining high yields and concentrations of ethanol, using low-cost medium, is the primary goal, leading the research done today. Batch Saccharomyces cerevisiae fermentation of high-density sugar from carob residues with different organic (yeast extract, peptone, urea) and inorganic nitrogen sources (ammonium sulfate, ammonium nitrate) was performed for evaluating a cost-effective ethanol production, with high ethanol yield and productivity. In STR batch fermentation, urea has proved to be a very promising nitrogen source in large-scale production of bioethanol, reaching an ethanol yield of 44 % (w/w), close to theoretical maximum yield value and an ethanol production of 115 g/l. Urea at 3 g/l as nitrogen source could be an economical alternative with a great advantage in the sustainability of ethanol production from carbohydrates extracted from carob. Simulation studies, with experimental data using SuperPro Design software, have shown that the bioethanol production biorefinery from carob wastes could be a very promising way to the valorization of an endogenous resource, with a competitive cost.

Sugarcane bagasse delignification with potassium hydroxide for enhanced enzymatic hydrolysis

Alkali pretreatment of sugarcane bagasse biomass was shown to be effective for producing sugar-rich hydrolysates for biotechnological applications.

Comparative techno-economic assessment and LCA of selected integrated sugarcane-based biorefineries

This work addresses the economic and environmental performance of integrated biorefineries based on sugarcane juice and residues. Four multiproduct scenarios were considered; two from sugar mills and the others from ethanol distilleries. They are integrated biorefineries producing first (1G) and second (2G) generation ethanol, sugar, molasses (for animal feed) and electricity in the context of Brazil. The scenarios were analysed and compared using techno-economic value-based approach and LCA methodology. The results show that the best economic configuration is provided by a scenario with largest ethanol production while the best environmental performance is presented by a scenario with full integration sugar - 1G2G ethanol production.

Process design and evaluation of production of bioethanol and β-lactam antibiotic from lignocellulosic biomass

To design biorefinery processes producing bioethanol from lignocellulosic biomass with dilute acid pretreatment, biorefinery processes were simulated using the SuperPro Designer program. To improve the efficiency of biomass use and the economics of biorefinery, additional pretreatment processes were designed and evaluated, in which a combined process of dilute acid and aqueous ammonia pretreatments, and a process of waste media containing xylose were used, for the production of 7-aminocephalosporanic acid. Finally, the productivity and economics of the designed processes were compared.

Polyhydroxyalkanoate biosynthesis and simultaneous remotion of organic inhibitors from sugarcane bagasse hydrolysate by Burkholderia sp

Burkholderia sp. F24, originally isolated from soil, was capable of growth on xylose and removed organic inhibitors present in a hemicellulosic hydrolysate and simultaneously produced poly-3-hydroxybutyrate (P3HB). Using non-detoxified hydrolysate, Burkholderia sp. F24 reached a cell dry weight (CDW) of 6.8 g L−1, containing 48 % of P3HB and exhibited a volumetric productivity (PP3HB) of 0.10 g L−1 h−1. Poly-3-hydroxybutyrate-co-3-hydroxyvalerate copolymers (P3HB-co-3HV) were produced using xylose and levulinic acid (LA) as carbon sources. In shake flask cultures, the 3HV content in the copolymer increased from 9 to 43 mol% by adding LA from 1.0 to 5.0 g L−1. In high cell density cultivation using concentrated hemicellulosic hydrolysate F24 reached 25.04 g L−1 of CDW containing 49 % of P3HB and PP3HB of 0.28 g L−1 h−1. Based on these findings, second-generation ethanol and bioplastics from sugarcane bagasse is proposed.

Effects of production and market factors on ethanol profitability for an integrated first and second generation ethanol plant using the whole sugarcane as feedstock

BACKGROUND

Sugarcane is an attractive feedstock for ethanol production, especially if the lignocellulosic fraction can also be treated in second generation (2G) ethanol plants. However, the profitability of 2G ethanol is affected by the processing conditions, operating costs and market prices. This study focuses on the minimum ethanol selling price (MESP) and maximum profitability of ethanol production in an integrated first and second generation (1G + 2G) sugarcane-to-ethanol plant. The feedstock used was sugarcane juice, bagasse and leaves. The lignocellulosic fraction was hydrolysed with enzymes. Yields were assumed to be 95% of the theoretical for each of the critical steps in the process (steam pretreatment, enzymatic hydrolysis (EH), fermentation, solid/liquid separation, anaerobic digestion) in order to obtain the best conditions possible for ethanol production, to assess the lowest production costs. Techno-economic analysis was performed for various combinations of process options (for example use of pentoses, addition of leaves), EH conditions (water-insoluble solids (WIS) and residence time), operating cost (enzymes) and market factors (wholesale prices of electricity and ethanol, cost of the feedstock).

RESULTS

The greatest reduction in 2G MESP was achieved when using the pentoses for the production of ethanol rather than biogas. This was followed, in decreasing order, by higher enzymatic hydrolysis efficiency (EHE), by increasing the WIS to 30% and by a short residence time (48 hours) in the EH. The addition of leaves was found to have a slightly negative impact on 1G + 2G MESP, but the effect on 2G MESP was negligible. Sugarcane price significantly affected 1G + 2G MESP, while the price of leaves had a much lower impact. Net present value (NPV) analysis of the most interesting case showed that integrated 1G + 2G ethanol production including leaves could be more profitable than 1G ethanol, despite the fact that the MESP was higher than in 1G ethanol production.

CONCLUSIONS

A combined 1G + 2G ethanol plant could potentially outperform a 1G plant in terms of NPV, depending on market wholesale prices of ethanol and electricity. Therefore, although it is more expensive than 1G ethanol production, 2G ethanol production can make the integrated 1G + 2G process more profitable.

The sugar and alcohol industry in the biofuels and cogeneration era: a paradigm change (part II)

The aim of this paper is to discuss the major technological changes related to the implementation of large-scale cogeneration and biofuel production in the sugar and alcohol industry. The reduction of the process steam consumption, implementation of new alternatives in driving mills, the widespread practice of high steam parameters use in cogeneration facilities, the insertion of new technologies for biofuels production (hydrolysis and gasification), the energy conversion of sugarcane trash and vinasse, animal feed production, process integration and implementation of the biorefinery concept are considered. Another new paradigm consists in the wide spreading of sustainability studies of products and processes using the Life Cycle Assessment (LCA) and the implementation of sustainability indexes. Every approach to this issue has as an objective to increase the economic efficiency and the possibilities of the sugarcane as a main source of two basic raw materials: fibres and sugar. The paper briefly presents the concepts, indicators, state-of-the-art and perspectives of each of the referred issues.

Utilization of pentoses from sugarcane biomass: techno-economics of biogas vs. butanol production

This paper presents the techno-economics of greenfield projects of an integrated first and second-generation sugarcane biorefinery in which pentose sugars obtained from sugarcane biomass are used either for biogas (consumed internally in the power boiler) or n-butanol production via the ABE batch fermentation process. The complete sugarcane biorefinery was simulated using Aspen Plus®. Although the pentoses stream available in the sugarcane biorefinery gives room for a relatively small biobutanol plant (7.1-12 thousand tonnes per year), the introduction of butanol and acetone to the product portfolio of the biorefinery increased and diversified its revenues. Whereas the IRR of the investment on a biorefinery with biogas production is 11.3%, IRR varied between 13.1% and 15.2% in the butanol production option, depending on technology (regular or engineered microorganism with improved butanol yield and pentoses conversion) and target market (chemicals or automotive fuels). Additional discussions include the effects of energy-efficient technologies for butanol processing on the profitability of the biorefinery.

Butanol production in a first-generation Brazilian sugarcane biorefinery: technical aspects and economics of greenfield projects

The techno-economics of greenfield projects of a first-generation sugarcane biorefinery aimed to produce ethanol, sugar, power, and n-butanol was conducted taking into account different butanol fermentation technologies (regular microorganism and mutant strain with improved butanol yield) and market scenarios (chemicals and automotive fuel). The complete sugarcane biorefinery with the batch acetone-butanol-ethanol (ABE) fermentation process was simulated using Aspen Plus®. The biorefinery was designed to process 2 million tonne sugarcane per year and utilize 25%, 50%, and 25% of the available sugarcane juice to produce sugar, ethanol, and butanol, respectively. The investment on a biorefinery with butanol production showed to be more attractive [14.8% IRR, P(IRR>12%)=0.99] than the conventional 50:50 (ethanol:sugar) annexed plant [13.3% IRR, P(IRR>12%)=0.80] only in the case butanol is produced by an improved microorganism and traded as a chemical.

Liquid hot water pretreatment of sugarcane bagasse and its comparison with chemical pretreatment methods for the sugar recovery and structural changes

Liquid hot water (LHW), dilute hydrochloric acid (HCl) and dilute sodium hydroxide (NaOH) were applied to sugarcane bagasse (SB). Application of the same analytical methods and material balance approaches facilitated meaningful comparisons of glucose and xylose yields from combined pretreatment and enzymatic hydrolysis. All pretreatments enhanced sugar recovery from pretreatment and subsequent enzymatic hydrolysis substantially compared to untreated sugarcane bagasse. Adding Tween80 in the enzymatic hydrolysis process increased the conversion level of glucan/xylan by 0.3-fold, especially for the low pH pretreatment where more lignin was left in the solids. The total sugar recovery from sugarcane bagasse with the coupled operations of pretreatment and 72 h enzymatic digestion reached 71.6% for LHW process, 76.6% for HCl pretreatment and 77.3% for NaOH pretreatment. Different structural changes at the plant tissue, cellular, and cell wall levels might be responsible for the different enzymatic digestibility. Furthermore, a combined LHW and aqueous ammonia pretreatment was proposed to reduce energy input and enhance the sugar recovery.

Evaluation of energy cane and sweet sorghum as feedstocks for conversion into fuels and chemicals

Sweet sorghum and energy cane (high fiber cane) are potential crops for conversion into fuels and chemicals due to their low agricultural input requirements, potentially high fiber content and processing similarities with established sugarcane crops. A conceptual approach to a biorefinery producing fuels and chemicals from sweet sorghum and energy cane is proposed. The front-end of the plant processes 10,000 t/d of feedstock to extract convertible sugars by milling and concentrate them into storable syrups. The latter can be processed into gasoline, jet fuel and isoprene using proprietary technologies. The fiber remaining after extraction, called bagasse, is used in the boilers of the front-end plant to provide steam and power for entire facility and to produce additional second generation sugars by pretreatment and hydrolysis in a lignocellulosic conversion plant. Material and energy balances for the front-end plant were calculated using SugarsTM software. Results show that for the selected variety of energy cane, up to 46% of bagasse is available for further lignocellulosic conversion resulting in production of additional 33.6% of sugars. In this case, however, surplus electricity production is reduced by 86%. Calculations for sweet sorghum follow the same trend. Results show that a 13% reduction in fiber content by processing sweet sorghum instead of energy cane, reduces power export by 71% and second generation sugars by 40%.

Integrated versus stand-alone second generation ethanol production from sugarcane bagasse and trash

Ethanol production from lignocellulosic materials is often conceived considering independent, stand-alone production plants; in the Brazilian scenario, where part of the potential feedstock (sugarcane bagasse) for second generation ethanol production is already available at conventional first generation production plants, an integrated first and second generation production process seems to be the most obvious option. In this study stand-alone second generation ethanol production from surplus sugarcane bagasse and trash is compared with conventional first generation ethanol production from sugarcane and with integrated first and second generation; simulations were developed to represent the different technological scenarios, which provided data for economic and environmental analysis. Results show that the integrated first and second generation ethanol production process from sugarcane leads to better economic results when compared with the stand-alone plant, especially when advanced hydrolysis technologies and pentoses fermentation are included.

Second generation ethanol in Brazil: can it compete with electricity production?

Much of the controversy surrounding second generation ethanol production arises from the assumed competition with first generation ethanol production; however, in Brazil, where bioethanol is produced from sugarcane, sugarcane bagasse and trash will be used as feedstock for second generation ethanol production. Thus, second generation ethanol production may be primarily in competition with electricity production from the lignocellulosic fraction of sugarcane. A preliminary technical and economic analysis of the integrated production of first and second generation ethanol from sugarcane in Brazil is presented and different technological scenarios are evaluated. The analysis showed the importance of the integrated use of sugarcane including the biomass represented by surplus bagasse and trash that can be taken from the field. Second generation ethanol may favorably compete with bioelectricity production when sugarcane trash is used and when low cost enzyme and improved technologies become commercially available.

Production of bioethanol, methane and heat from sugarcane bagasse in a biorefinery concept

The potential of biogas production from the residues of second generation bioethanol production was investigated taking into consideration two types of pretreatment: lime or alkaline hydrogen peroxide. Bagasse was pretreated, enzymatically hydrolyzed and the wastes from pretreatment and hydrolysis were used to produce biogas. Results have shown that if pretreatment is carried out at a bagasse concentration of 4% DM, the highest global methane production is obtained with the peroxide pretreatment: 72.1 Lmethane/kgbagasse. The recovery of lignin from the peroxide pretreatment liquor was also the highest, 112.7 ± 0.01 g/kg of bagasse. Evaluation of four different biofuel production scenarios has shown that 63-65% of the energy that would be produced by bagasse incineration can be recovered by combining ethanol production with the combustion of lignin and hydrolysis residues, along with the anaerobic digestion of pretreatment liquors, while only 32-33% of the energy is recovered by bioethanol production alone.