Autonomous Distillery Research Articles

Techno-economic evaluation of second-generation ethanol from sugarcane bagasse: Commercial versus on-site produced enzymes and use of the xylose liquor

Biomass ethanol production presents shortcomings related to enzymes cost and efficiency of xylose fermentation. Commercial enzymes used in second-generation ethanol (2GE) plants are produced off-site/offshore, with the additional formulation, transportation and storage costs. Alternatively, lower cost cellulases can be produced on-site. This study focused on the techno-economic evaluation of enzymes produced on-site versus commercial. Another limiting feature of the 2GE technology is the use of the hemicellulose sugars for ethanol fermentation. Thus, this work addressed its use for biogas production. Process systems engineering tools were used to evaluate four different configurations of a 2GE plant annexed to an already existent autonomous distillery. The application of the methodology allowed useful perceptions of the ethanol and biogas production, water and electricity consumption, and economic profitability. The need of a second fungus strain for the on-site enzyme production was identified as the main bottleneck of this cellulase production process, which is an important insight that could guide the future research efforts.

Technoeconomic Evaluation of a Flex Ethanol Plant of Sugarcane and Corn in Brazil

AbstractThis paper aims to evaluate the integration of corn in existent sugarcane mills in Brazil to increase ethanol production. The study considered an autonomous distillery factory of medium‐capacity, and the incremental benefits from corn processing during the sugarcane off‐season. A process simulation and a cost analysis were developed to estimate the technoeconomic feasibility. The data and parameters employed were in accordance with Brazilian practice. The results show that a sugarcane plant operating 4 months during the off‐season with corn requires an investment of US$ 13.4 million, obtained the return of investment in 4 years, and a revenue estimated in US$ 666K yr−1 due to ethanol surplus production.

Sustainability analysis of bioethanol production in Mexico by a retrofitted sugarcane industry based on the Brazilian expertise

Bioethanol as fuel oxygenator is currently being introduced in Mexico with an estimated yearly demand of 3 billion liters expected to be produced mainly from sugarcane. This paper studies how to employ some of the expertise acquired by Brazil during its transition from typical mills into advanced biorefineries to retrofit the Mexican sucroalcohol industry. A typical Mexican sugarcane factory design is retrofitted to three biorefinery designs commonly found in Brazil, which are an autonomous distillery, a biorefinery with 50:50 feedstock ratio for ethanol and sugar production and a molasses distillery. The results of a techno-economic analysis considering these four designs under Mexican conditions are presented, followed by an economic comparison of the autonomous distillery design operating under Mexican and Brazilian conditions. Sustainability analysis is then carried out to identify the advantages and drawbacks of each design. The analysis compares an environment-driven scenario promoting bioethanol production and use for phasing out fossil fuels, against a commercially focused framework considering only environmental and economic issues affecting stakeholders’ profit. Results show in monetary terms the impact of each indicator of a retrofitting path from currently profitable biorefineries coproducing sugar and alcohol to sustainable distilleries using molasses and juice as feedstock to produce bioethanol.

Multi-objective optimization of a 1G-2G biorefinery: A tool towards economic and environmental viability

First-generation sugarcane ethanol production is a well-established technology. However, second-generation ethanol is not yet consolidated in industries. Under these circumstances, this work presents a multi-objective optimization of this process focusing on economic and environmental objectives. The impact of the Brazilian decarbonization program on an integrated biorefinery is analyzed, considering a first-generation ethanol conventional autonomous distillery and a second-generation process with hydrothermal pre-treatment, enzymatic hydrolysis and fermentation of the xylose liquor. The economic metric was the Net Present Value and the environmental assessment was based on the plant inventory considering Global Warming Potential. A multi-objective particle swarm optimization algorithm was used, considering the ratio of bagasse diverted to the second-generation process, enzyme loading and solid fraction in the hydrolysis reactor as optimization variables. The carbon credit price was estimated for each point in the Pareto set in order to make the process economically feasible. As the main conclusions, there is a trade-off between economic and environmental targets, indicating that carbon credits may be essential for second-generation ethanol economic feasibility. The optimized integrated biorefinery is able to increase ethanol production by approximately 24% compared to first-generation biorefineries, but an increase in ethanol production higher than 13% would make the process economically unfeasible, while the decarbonization credits are not being commercialized. A price of $ 15.77 for decarbonization credits would make it possible to produce 20% more ethanol, keeping the integrated biorefinery economically feasible.

Exergy and Environmental Analysis of a Polygeneration System of Alcohol Industry

An analyze of three case studies from environmental and energy view point, those case studies are polygeneration system, A first study is referred to a conventional distillery that produces ethanol and surplus electricity, the second one, in addition to ethanol and electricity products, also produces second generation bioethanol (2G) from sugarcane bagasse. A third case study refers to an installation producing surplus electricity, bioethanol (2G) from bagasse and bioethanol from cane juice, as well as fodder yeast from vinasses (distillery residue). After defining each study, an exergetic analysis and calculated performance indicators were made to determine best case study. A Life Cycle Analysis to verify the environmental performance of each system complemented the study. Results indicated that case study 3 presented best energy performance, with an exergetic efficiency of 45.03%, having as advantage fodder yeast for cattle feeding. From environmental point of view land occupation by agriculture remains main environmental impact for all three case studies. This paper presents an alternative for products diversification of an autonomous distillery, combining second generation ethanol and use of vinasses (distillery residue) as raw material for fodder yeasts bioproduction, a feeding cattle protein supplement, inducing also a significant reduction of vinasses contamination potential.

Comparative Performance Indexes for Ethanol Production Based on Autonomous and Annexed Sugarcane Plants

Future biomass conversion systems have to be developed using advanced technological routes in order to compete with fossil fuels, as well as to fulfill sustainability criteria. An attractive biomass feedstock for ethanol production is sugarcane, which is available in large amounts in several regions around the world. Although first-generation ethanol is a consolidated process, due to their large-scale production and tradition, there is still room for improved economic and environmental outcomes in the bioethanol industry.Bearing this in mind, this work presents a detailed process design strategy for biomass to ethanol production (1st-generation ethanol technology) from sugarcane. The simulation processes were performed using Aspen Plus® software focus on the annexed plant (production of bioethanol and sugar) and autonomous distillery(only bioethanol is produced) systems. Furthermore, a performance comparison in terms of the exergy efficiency and the destroyed exergy rate as a metric conversion of the processes are determined. Hence, the techno-economic bottlenecks in bioethanol production are attained using the exergy as an index. In addition, the sustainability aspects involved in the process design of the sugarcane biorefineries was discussed through the renewability exergy index. The results showed that the annexed plant has a reduction in the process irreversibilities rate of 6 % approximately, and in the average unitary exergy cost rate of 10 % approximately, in comparison to the autonomous distillery. Even though the proposed methodology is applied to 1G ethanol, it may well suited for several bioprocesses as a tool to help in taking decisions regarding design as well as operational policy definitions.

Environmental assessment of a standard distillery using aspen plus®: Simulation and renewability analysis

This study investigates the sustainability of the first-generation ethanol production process using a water steam condensed stream reuse approach. Determination was made of the effective water collection of an autonomous distillery and opportunities for the reuse of water streams were identified. Given the importance of the distillation design and its impacts on sustainability, relevant problems and challenges are highlighted, and suggestions are made of ways to enhance the process. Simulations were carried out using the Aspen Plus simulator to perform mass and energy balances. Three case studies were investigated: distillation with use of a reboiler as heat source (Case I); conventional direct steam injection distillation (Case II); and distillation with mechanical vapour recompression (Case III). In all cases, environmental aspects were considered using WAR software and exergy concepts. A technical-economic evaluation of the distillation system was performed in order to identify the best design. The results showed that the use of closed circuits and water reuse streams provided an overall consumption of 673 L water/t of cane in the mill. This value is lower than the statutory limit of 1000 L/t of cane established for distilleries in the State of São Paulo. Furthermore, according to the results obtained using the WAR software and the concepts of exergy and renewability index, Case II and III were considered to provide worse environmental performance, compared to Case I. In addition, Case I achieved net revenue of US$ 115 million, which was approximately 9% and 12% higher than achieved for Cases II and III, respectively. Therefore, it is environmentally and economically beneficial to employ a reboiler as a heat source in distillation systems, compared to conventional systems employed to produce bioethanol.

Sugarcane biorefineries: Case studies applied to the Brazilian sugar–alcohol industry

The use of biomasses is becoming increasingly appealing alternative, to give an partial solution lack of energy, with an ecofriendly approach, having on sugarcane a solid fundament; that receives the new and valuable complement of the innovative concept of the biorefineries it is productive installations, that can be summarized as to reach the higher overall yield from the raw materials, with the lowest environmental impact, at minimum energy input and giving the maximum of the energy output. The biorefinery is the true valuable option of a wide diversification, with by-products like the single cell protein and biogas from the distillery vinasse, new oxidants like methanol, second generation biofuels, biobutanol, etc.In this context this paper presents a study of five different configurations of biorefineries. Each case study being a system based on an autonomous distillery or sugar mill with an annexed distillery and coproduction of methanol from bagasse. The paper includes the use of sugarcane harvest residues (mainly straw) and a BIG–GT plant (Biomass Integrated Gasification–Gas Turbine) as alternatives to fulfill the energy demands of the complex.

Product diversification to enhance economic viability of second generation ethanol production in Brazil: The case of the sugar and ethanol joint production

Commercial simulator Aspen Plus® was used to simulate the conventional processes of the autonomous distillery producing ethanol and the joint production of sugar and ethanol. Changes in conventional processes were evaluated to increase electricity and second generation ethanol production using bagasse fine fraction composed by parenchyma cells (P-fraction). The evaluated processes were thermal and water integrated. The results indicated that the integration of the second generation process to the conventional processes was possible after thermal and water integration. The economic analysis showed that the second generation process integrated to the joint production presented lower payback time, 2.3 years, in comparison with this process integrated to the autonomous distillery, 4.7 years. Due to the high enzyme costs, the cases without second generation ethanol production presented higher economic viability. Product diversification, as sugar and ethanol production in the same site, lowered the impact of enzymes cost on the payback time of second generation process, showing that the integration of the second generation ethanol production process to the conventional sugar production process could be a step to cellulosic ethanol production feasibility in sugarcane mills.

Improving second generation ethanol production through optimization of first generation production process from sugarcane

Sugarcane bagasse and trash may be used as feedstock for second generation ethanol production. Production of second generation ethanol integrated with first generation plants processing sugarcane presents several advantages over the stand-alone second generation ethanol production process; however, bagasse is used as fuel to supply the energy demand of the first generation process, so the amount of bagasse and trash available for use as feedstock in second generation depends on the energy consumption of the integrated process. Therefore, process optimization leading to reduction in steam consumption will lead to the production of larger amounts of surplus bagasse. In this study the introduction of process improvements in the first generation autonomous distillery processing sugarcane were assessed through simulation using Aspen Plus. Second generation ethanol production was integrated to the optimized scenarios. Results show that process improvements can significantly increase the amount of lignocellulosic material available for use as feedstock for second generation ethanol production, thus increasing ethanol production.

Improving bioethanol production – Comparison between extractive and low temperature fermentation

One of the key issues that must be addressed in the biofuel production based on sugarcane industry is the energy consumption of the process. Process energy demand has direct impact on the amount of lignocellulosic material available for use as feedstock for second generation ethanol production. A significant fraction of the energy consumption in bioethanol production occurs in the purification step, since conventional fermentation systems employed in the industry require low substrate concentration and, consequently, produce wine of low (around 8.5°GL) ethanol content that must be distilled in order to meet product specifications. In this study alternatives to the conventional fermentation processes employed in the industry (low temperature fermentation and vacuum extractive fermentation) were assessed, in the context of a large scale sugarcane autonomous distillery, through computer simulation. Electricity consumption and lignocellulosic material surplus on each case were evaluated. It is shown that the alternative fermentation processes allow a significant reduction on vinasse generation and increases ethanol production when compared with conventional fermentation, but increases electricity consumption (for the extractive fermentation) or steam consumption (for low temperature fermentation); when vinasse concentration is considered in the conventional process, steam consumption in the extractive fermentation is also significantly smaller.

Improving bioethanol production from sugarcane: evaluation of distillation, thermal integration and cogeneration systems

Demand for bioethanol has grown considerably over the last years. Even though Brazil has been producing ethanol from sugarcane on a large scale for decades, this industry is characterized by low energy efficiency, using a large fraction of the bagasse produced as fuel in the cogeneration system to supply the process energy requirements. The possibility of selling surplus electricity to the grid or using surplus bagasse as raw material of other processes has motivated investments on more efficient cogeneration systems and process thermal integration. In this work simulations of an autonomous distillery were carried out, along with utilities demand optimization using Pinch Analysis concepts. Different cogeneration systems were analyzed: a traditional Rankine Cycle, with steam of high temperature and pressure (80 bar, 510 °C) and back pressure and condensing steam turbines configuration, and a BIGCC (Biomass Integrated Gasification Combined Cycle), comprised by a gas turbine set operating with biomass gas produced in a gasifier that uses sugarcane bagasse as raw material. Thermoeconomic analyses determining exergy-based costs of electricity and ethanol for both cases were carried out. The main objective is to show the impact that these process improvements can produce in industrial systems, compared to the current situation.

Thermodynamic analysis of an alcohol distillery

An energy analysis is performed on an autonomous distillery in Brazil for the production of alcohol from sugar cane. Selected instantaneous operational data complemented by mean operational values and design values are used to calculate the mass and energy balances. The second-law efficiency is evaluated in important sectors of the plant and in the overall process. The sectors of steam generation (54.7%), fermentation (32.0%) and distillation (7.2%) are found to account for most of the exergy losses in the plant. The fraction of the exergy output to that of the input is 33.8%, which is comparable to the effectiveness of small power plants.