Sugarcane Biorefinery Research Articles

Valorization of the sugarcane bagasse and straw hemicellulosic hydrolysate through xylitol bioproduction: effect of oxygen availability and sucrose supplementation as key factors

Sugarcane agroindustry, one of the most important in Brazilian economy, can diversify its product portfolio in a biorefinery context through the use of by-products as feedstocks to produce bioenergy and high-added value chemicals, such as xylitol, which is a sweetener with applications in the food and pharmaceutical industries and with a growing market. Opportunities for the integration of xylitol bioproduction in a sugarcane biorefinery can be based on the valorization of bagasse, straw, and molasses, which are feedstocks with high content of carbohydrates, specifically xylose from the hemicellulosic fraction of the lignocellulosic biomasses, and sucrose from molasses that can act as co-substrate on this bioprocess. Xylitol bioproduction from the hemicellulosic hydrolysate of the sugarcane bagasse and straw mixture was herein investigated. Particularly, the effects of sucrose supplementation to the medium on the fermentative performance of Candida tropicalis depending on its initial concentration and oxygen availability (expressed as KLa), which is one of the most important factors for this bioprocess, are discussed. Xylitol yield (0.86 gg−1) and volumetric productivity (0.51 gL−1 h−1) were concomitantly maximized by using sucrose (0.91 gL−1) and KLa (6.5 h−1) within the optimization range. Furthermore, the addition of sugarcane molasses to the hemicellulosic hydrolysate improved xylitol production, in comparison with the conventional supplementation. Scientific background is given to contribute to supporting the potential integration of xylitol bioproduction to a sugarcane biorefinery, which may enhance both the feasibility of this bioprocess and sugarcane agroindustry valorization based on the applications and growing xylitol market.

Techno-Economic and Environmental Assessment of Biomass Gasification and Fischer–Tropsch Synthesis Integrated to Sugarcane Biorefineries

Large-scale deployment of both biochemical and thermochemical routes for advanced biofuels production is seen as a key climate change mitigation option. This study addresses techno-economic and environmental aspects of advanced liquid biofuels production alternatives via biomass gasification and Fischer–Tropsch synthesis integrated to a typical sugarcane distillery. The thermochemical route comprises the conversion of the residual lignocellulosic fraction of conventional sugarcane (bagasse and straw), together with eucalyptus and energy-cane as emerging lignocellulosic biomass options. This work promotes an integrated framework to simulate the mass and energy balances of process alternatives and incorporates techno-economic analyses and sustainability assessment methods based on a life-cycle perspective. Results show that integrated biorefineries provide greenhouse gas emission reduction between 85–95% compared to the fossil equivalent, higher than that expected from a typical sugarcane biorefinery. When considering avoided emissions by cultivated area, biorefinery scenarios processing energy-cane are favored, however at lower economic performance. Thermochemical processes may take advantage of the integration with the typical sugarcane mills and novel biofuels policies (e.g., RenovaBio) to mitigate some of the risks linked to the implementation of new biofuel technologies.

Bioconversion of pretreated sugarcane vinasse into hydrogen: new perspectives to solve one of the greatest issues of the sugarcane biorefinery

Currently, the disposal of sugarcane vinasse is one of the greatest issues of sugarcane biorefineries in Brazil because of the large volumes produced. To contribute with an alternative energy recovery process from this by-product, this study proposed a physicochemical pretreatment and adjustment of operating conditions to improve the performance of the acidogenic stage of the anaerobic digestion of sugarcane vinasse. Therefore, this study evaluated the influence of hydraulic retention time (decreasing from 8 to 6, 4, 2, and 1 h) on the bioconversion of pretreated sugarcane vinasse (5000 mg COD L−1) to hydrogen and value-added products. Two anaerobic fluidized bed reactors were operated under mesophilic (AFBR-M, 30 °C) and thermophilic (AFBR-T, 55 °C) conditions. Despite the low similarity between the bacterial populations of AFBR-M and AFBR-T (40% similarity), the maximum hydrogen production rates (0.27 ± 0.07 and 6.42 ± 1.46 L H2 day−1 L−1) and hydrogen yields (0.27 ± 0.07 and 1.06 ± 0.15 mmol H2 g COD−1) occurred at the hydraulic retention time of 2 h by reducing the values from 8 to 2 h. The highest COD/SO42− ratios of 17.4 and 25.1 were also observed in the effluents of the AFBR-M and AFBR-T, respectively, at the hydraulic retention time of 2 h. Under both mesophilic and thermophilic conditions, a similar metabolic distribution was observed at the HRT of 2 h (acetic, propionic, and butyric acids, for AFBR-M and acetic, propionic, butyric acids, and ethanol for AFBR-T). This finding indicates the functional similarity between bacterial populations in both reactors.

Molasses vs. juice: Maximizing biohydrogen production in sugarcane biorefineries to diversify renewable energy generation

Diversifying the portfolio of bioenergy-related products in sugarcane biorefineries is required to increase substrate conversion efficiency and market reach. The suitability of producing biohydrogen (bioH2) through the thermophilic dark fermentation of juice and molasses was assessed as an alternative to conventional sugarcane processing. The energetic potential of applying anaerobic digestion with phase separation to process molasses was also investigated. Molasses outperformed juice as substrate for continuous bioH2 production due to a more balanced nutrient content, whilst nitrogen deficiency directly hindered juice fermentation. An optimal COD/N ratio (∼100) could maximize bioH2 production from both juice and molasses. Continuous bioH2 production from molasses fermentation was optimized at pH and organic loading rate values of 5.38 and 86 kg-COD m−3 d-1, which are consistent with acidogenic systems inoculated with sugarcane vinasse-derived consortia. Metabolite profiles suggested that capnophilic lactic fermentation coupled to lactate-based butyrate production were the primary conversion pathways. Bioenergy generation from molasses (bioH2 + methane) exceeded that of vinasse by over 600 %, highlighting the relevance of anaerobic digestion as an efficient core processing step in the sucroenergetic industry. In particular, phase separation enhanced the total energy production by 13.1 % (604.30 vs. 683.76 MJ per ton of sugarcane) by maximizing the methane yield up to theoretical values.

Biochemical conversion of sugarcane bagasse into the alcohol fuel mixture of isopropanol-butanol-ethanol (IBE): Is it economically competitive with cellulosic ethanol?

This work presents a techno-economic analysis of the production of isopropanol, butanol, and ethanol (IBE) from sugarcane bagasse using clostridia and compares IBE with cellulosic ethanol for the minimum selling price (MSP) and sustainability aspects. The MSPs of the fuels are similar (15 USD/GJ) provided that glucose and xylose are effectively utilized in both processes, and the IBE process is equipped with a genetically-modified Clostridium species with enhanced IBE yield and a highly productive continuous bioreactor with integrated product recovery. Notably, these technologies can reduce the size (from 23 × 3785-m3 to 3 × 3027-m3 fermentation tanks) and the wastewater footprint (from 50 to 10 m3/m3 IBE) of the IBE plant. Furthermore, given that the production of either fuel results in a similar increase in the value created by the sugarcane biorefinery and its energy efficiency, the alcohol mixture produced by clostridia is a promising alternative to the less energy-dense ethanol fuel.

Biochemical butyrate production via dark fermentation as an energetically efficient alternative management approach for vinasse in sugarcane biorefineries

Abstract This study investigated the application of dark fermentation to obtain value-added soluble metabolite products (SMP) from vinasse as a strategy to enhance the energy efficiency in sugarcane biorefineries. Batch tests comparing sucrose and vinasse as the substrates were conducted, providing data to both understand conversion pathways and measure the energetic implications of fermenting vinasse under controlled conditions. Two distinct inoculum pretreatment methods, namely, acid-thermal and thermal were also assessed. Overall, butyrate fermentation was the primary conversion pathway observed in vinasse acidogenesis, leading to butyric/isobutyric acid concentrations over 6.0 g L−1, irrespective of the inoculum pretreatment. Lactic and malic acids were the primary substrates, with the predominance of the lactate-to-butyrate fermentation, suggesting the establishment of a syntrophic relation between lactate-producing bacteria and clostridial populations. Considering energetic aspects, the enhanced butyrate production could lead to an energy recovery potential of 30.9–33.4 MW, outcompeting highly-efficient biohydrogen- (

Cultivation of Chlamydomonas reinhardtii in Anaerobically Digested Vinasse for Bioethanol Production

This study describes a new algal biofuel process that integrates sugarcane biorefinery wastewater treatment by nutrient removal with algae into bioethanol. The process is free of common industrial problems, including algal contamination, nutrients and fresh water usage, carbohydrate extraction, liquefaction, and saccharification. Cultivation and fermentation were conducted in one step by turning the light-air on and off, respectively. Three series of experiments with Chlamydomonas reinhardtii CC-1093 cultivation and fermentation were performed in anaerobically digested vinasse. Control experiments were a reference to compare the influence of chloride and ammonium-sulfate stress conditions on ethanol yield. Experimental results showed: (1) algal biomass can be successfully cultured within biorefinery wastewater (1129 mg·L−1·day−1); (2) relatively high bioremediation was achieved (26.1%–83.5%); (3) obtained ethanol yield was (maximum 68.3% of the theoretical yield) in one process step; and (4) the chloride stress condition influences on algae to synthesize extracellular polysaccharides as add-in product (120 mg/L).

Techno-economic assessment of bioenergy and biofuel production in integrated sugarcane biorefinery: Identification of technological bottlenecks and economic feasibility of dilute acid pretreatment

Techno-economic analysis of first- and second-generation (1G2G) integrated sugarcane biorefinery producing ethanol and electricity was performed, exploring the virtues and limitations of dilute acid pretreatment. Process variables such as solid content in the pretreatment reactor, enzymatic hydrolysis time, and the possibility of pentose fermentation were pondered using computational tools and simulation platforms to assess the impacts of the variables overall production chain. Previously published data reporting optimal pretreatment conditions applied to a leading sugarcane hybrid were considered in the simulation studies. Better economic returns were obtained using the lowest solids content in the pretreatment reactor, the shortest incubation time in the enzymatic hydrolysis step, as well as the use of the pentose stream to produce additional ethanol. Process profitability was mostly affected by sugarcane cost, followed by capital costs associated with investment, and input chemicals costs. Finally, this study indicates that the economic benefits do not only depend on achievement of high final product yields, but also on a set of industrial factors, demonstrating the suitability of process simulation to point out industrial bottlenecks deserving future research.

Multi-level system modelling of the resource-food-bioenergy nexus in the global south

To meet the demands for resources, food and energy, especially in fast developing countries in the Global South, new infrastructure investments, technologies and supply chains are required. It is essential to manage a transition that minimises the impacts on global environmental degradation while benefits local socio-economic development. Food-bioenergy integration optimising natural capital resources and considering wider environmental and socio-economic sustainability offers a way forward. This study presents an integrative approach enabling whole systems modelling to address the interlinkage and interaction of resource-food-bioenergy systems and optimise supply chains considering poly-centric decision spaces. Life cycle sustainability assessment, optimisation, agent-based modelling and simulation were coupled to build an integrated systems modelling framework applicable to the resource-food-bioenergy nexus. The model building blocks are described before their applications in three case studies addressing agricultural residues and macro-fungi in the Philippines, sugar cane biorefineries in South Africa, and Nipa palm biofuel in Thailand. Our case studies revealed the great potential of untapped biomass including agricultural waste and non-food biomass grown on marginal lands. Two value chain integration case studies – i.e. straw-fungi-energy in Philippines and sugar-energy in Africa – have been suggested as sustainable solutions to recover waste as value-added products to meet food and energy security. Case studies highlight how an integrative modelling framework can be applied to address multi-level questions, taking into account decision-making at different levels, which contribute to an overall sustainability goal.

Process simulation of renewable electricity from sugarcane straw: Techno-economic assessment of retrofit scenarios in Brazil

Approximately 7% of Brazilian electricity is generated from sugarcane biomass. Although this scenario is relatively optimistic when compared to the fossil-based energy matrix of other nations, there is a clear opportunity of expanding bioelectricity production in the country even more. Recent changes in the environmental legislation are progressively prohibiting burning before sugarcane harvesting in Brazilian Center-South region. Consequently, straw (i.e., sugarcane tops, dry and green leaves) has become available in most of the sugarcane fields. When considering the low availability of capital to invest in large-scale greenfield projects currently in Brazil, this paper focuses on retrofit investments, i.e., those related to existing sugarcane mills aiming to increase electricity production with incremental investments. This study is based on the Virtual Sugarcane Biorefinery framework that is developed in the Brazilian Biorenewables National Laboratory (LNBR/CNPEM). This simulation framework integrates both agricultural and industrial models to anticipate the impacts of biorefineries on different sustainability aspects. In this paper, process-based models are used to represent incremental changes caused by sugarcane straw recovery adopting the integral harvesting system. The techno-economic analysis shows that the internal rates of return (IRRs) of different alternatives depend on the conditions assumed in the sensitivity analysis. The main parameters assessed in the sensitivity are related to industrial plant scale, straw transport distance, industrial operating period, dry-cleaning system (DCS) efficiency and electricity prices. In the best incremental scenarios (operation during the offseason), IRRs ranged from 35 to 69%, 44–83%, and 54–99% per year when recovering straw in mills with original crushing capacities of 2, 4 and 8 million tons of sugarcane per year, respectively. This analysis ratifies that the economic feasibility increases as much as industrial scale increases; also, the system benefits from shorter straw transport distances. In general, higher DCS efficiencies can improve the economic viability, although some non-linear effects can be observed under specific conditions of the industrial operation. From all variables tested in the simulation, electricity price is one of the most sensitive parameters affecting the economic viability of straw recovery projects.

Towards the Production of mcl-PHA with Enriched Dominant Monomer Content: Process Development for the Sugarcane Biorefinery Context

The production of short-chain-length polyhydroxyalkanoates (scl-PHAs) in a sugarcane biorefinery setting has been demonstrated to be an effective strategy to reduce production costs. Medium-chain-length PHA (mcl-PHA) have elastomeric properties and are more suitable for high value-added applications, but its industrial production is not yet established. Mcl-PHA synthesis occurs via different metabolic routes and thus requires distinct microorganisms and substrates compared to scl-PHA. In the present study, sucrose-derived carbohydrates were evaluated as co-substrates for the production of mcl-PHA from decanoic acid (DA). Fermentation strategies were investigated to produce mcl-PHA with enriched dominant monomer content, which is desirable for commercial applications. The mcl-PHA production was investigated in carbon-limited, fed-batch fermentations with wild-type and β-oxidation knockout mutant strains of Pseudomonas putida KT2440. The experimental results demonstrated that a mixture of glucose and fructose was a suitable co-feed with DA for mcl-PHA production, yielding equivalent results to those obtained with starch-derived glucose, a more traditional feedstock for PHA production. The use of a β-oxidation-impaired strain was essential to attain high dominant monomer content. A near-homopolymeric mcl-PHA was produced under exponential feeding, containing 99 mol% of 3-hydroxydecanoate. This work demonstrates the potential for near-homopolymeric mcl-PHA production in a sugarcane biorefinery, using hydrolyzed sucrose and DA.

Upgrading sugarcane biorefineries: Acetate addition allows for conversion of fermented sugarcane molasses into high-value medium chain carboxylic acids

The aim of this study was to evaluate the role of acetate (C2) on n-butyric (C4) and n-caproic acid (C6) production, using fermented sugarcane molasses as a substrate. Inoculum sludge was acclimatized in a continuous upflow anaerobic sludge blanket reactor, where ethanol (EtOH) and acetate (C2) were administered at a ratio of 6:1 (g COD:g COD). Organic load rate increased gradually from 2.0 g COD L−1d-1 to 3.3, and 5.0 g COD L−1d−1, for 157 days. The acclimatized sludge was used as the inoculum in six batch assays fed with fermented molasses (ethanol-rich source) and C2 at EtOH:C2 ratios, g COD:g COD of 2:1; 4:1; 6:1, 8:1, and 10:1. A control assay was performed without C2 (WA). The EtOH:C2 ratio was more favorable toward C6 production with a ratio of 10:1, in which a C6 yield was observed as well as accumulated production of 0.4 g COD g COD−1 and 7.9 g COD L−1, respectively. Conversely, the EtOH:C2 ratio of 2:1, and the WA, resulted in C6 concentrations of 1.4 g COD L−1 and 4.3 g COD L−1, respectively. These findings confirmed that substrate composition control is essential for driving fermentation processes toward high medium-chain carboxylic acid conversion rate.

Dynamic study of the evaporation stage of an integrated first and second generation ethanol sugarcane biorefinery using EMSO software

Brazil is the largest producer of sugarcane ethanol in the world. Among the technologies that aim to improve the process, second generation ethanol is one of the most promising. Although still in development, it is a consensus that this process must be integrated into the production of first generation ethanol. Most of the work on this subject is involved in evaluating the steady-state process. However, the knowledge of the process dynamics plays an important role on the operational efficiency and control. In this work multiple effect evaporation is addressed. A dynamic phenomenological model of this step was developed in EMSO process simulator. A stream of glucose syrup is mixed with sugarcane juice stream at the entrance of the system and simulations were performed to analyze the integrated system dynamics. Step disturbances were applied in the sugar concentration, volumetric flow rate and temperature of the juice individually and simultaneously. Glucose syrup concentration and flow rate was also disturbed. PI/PID controllers were tested in order to control the system and the model consistency was verified in Aspen Dynamics. The analysis suggests that an adequate control system at the liquid and vapor output of each vessel cannot be achieved using only classical controllers.

Biogas Production from Anaerobic Digestion of Vinasse in Sugarcane Biorefinery: A Techno-economic and Environmental Analysis

Anaerobic digestion (AD) of effluents in sugarcane biorefineries may improve the energy balance in the bioethanol production process and the environmental suitability of wastes disposal. This study analyses the inclusion of AD of vinasse (stillage) into different configurations of sugarcane biorefineries, using technical, economic and environmental metrics. The three base-case scenarios are a first generation (1G) ethanol plant, an integrated first and second generation (1G2G) ethanol plant with alcoholic fermentation of the hemicellulose fraction (C5), and an 1G2G ethanol plant with biodigestion of the C5 fraction. These three base scenarios are compared with the similar ones including the biodigestion of vinasse. The implementation of vinasse biodigestion had positive impact on the productivity and sustainability of sugarcane biorefineries. The use of biogas from vinasse for a 1G ethanol plant increased in 9.20% the surplus of electric energy yielded to the grid. This scenario had a positive net present value, NPV: + 11.5 × 106 USD, assuming minimum acceptable rate of return, MARR = 11%. For the 1G2G + C5 fermentation scenario the NPV was + 4.63 × 106 USD. Assuming NPV = 0, the IRR for 1G becomes 19.7% and for 1G2G + C5, 13.6%, an IRR higher than the MARR. The inclusion of AD of vinasse when the C5 fraction is biodigested was not an economically feasible option. In all scenarios, vinasse biodigestion reduced environmental impacts, and the 1G2G processes exhibit better results than the consolidated 1G for almost all environmental impact categories. The AD of vinasse can be considered an environmental-friendly and economical-feasible technology to improve the process in sugarcane biorefineries.

Life cycle assessment and multi-criteria analysis of sugarcane biorefinery scenarios: Finding a sustainable solution for the South African sugar industry

Abstract The valorisation of sugarcane lignocelluloses is a potential solution to ensure the sustainability of the South African sugar industry. The sustainability of six biorefinery scenarios were assessed and compared. The scenarios are: a CHP coal supplemented itaconic acid biorefinery (Scenario 1), bioenergy self-sufficient (ESS) itaconic acid biorefinery (Scenario 2), ESS polyhydroxybutyrate (PHB) biorefinery (Scenario 3), ESS succinic acid and PHB biorefinery (Scenario 4), ESS succinic acid biorefinery (Scenario 5) and a stand-alone CHP plant (Scenario 6). An environmental life cycle assessment (eLCA) was conducted to identify potential problem or ‘hot spot’ areas in the respective processes, and to compare the environmental impacts of the bio-products to one another, as well as to their fossil reference products. Carbon footprint and water scarcity impact were included as the two eLCA parameters, together with four life cycle costing (LCC) parameters and one social life assessment (sLCA) parameter, in a life cycle sustainability assessment (LCSA). The LCSA parameters were normalized and weighed in a multi-criteria decision analysis tool to determine the most sustainable solution for implementation by the South African sugar industry. It was found that a trade-off exists between the environmental and techno-economic performance. Scenario 4 is the most sustainable scenario due to the environmental advantage obtained by the high succinic acid production volume, since the environmental burden is shared across a large number of bioproduct units together with the economic advantage of a high PHB selling price, while being bioenergy self-sufficient.

Competitive use of sugarcane for food, fuel, and biochemical through the environmental and economic factors

Bioethanol demands for transport face uncertainty; additionally, the emergence of electric vehicles is raising concerns among the ethanol producers towards the future demand and viability of the industry. Thus, there is a need to look for new pathways of sugar and ethanol utilization. However, the environmental and economic implications of the existing and proposed systems must be assessed to ensure sustainability. The study aims to evaluate and compare the environmental and economic performances of sugarcane for three new sugar-electricity-polylactic acid (PLA) systems with the existing sugar-electricity-ethanol system. The environmental hotspots of the existing and proposed sugarcane biorefinery systems are investigated and potential measures for enhancing environmental sustainability of the new systems identified. Life cycle assessment (LCA) is used for evaluating the environmental sustainability assessment of the sugarcane biorefinery and the eco-efficiency indicator, combining both the economic and environmental performances. The ReCiPe method with the hierarchist perspective at midpoint and the endpoint levels is used for quantifying the environmental impact scores. The reference unit is a tonne of cane processed at the biorefinery. The eco-efficiency is calculated based on the ReCiPe endpoint single score (“Pt”) and the values in “US$” of products from the different biorefinery systems. The results reveal that the PLA pathways to substitute ethanol and sugar production (PLA scenarios 1–3) can generate product values of about 83–220 US$/t cane processed leading to increased eco-efficiency values for all three PLA scenarios as compared to the existing sugar-electricity-ethanol system. The highest eco-efficiency (22 US$/Pt) is obtained for the pathways of PLA (scenario 3) and sugar-PLA (scenario 2). However, the LCA results show increased environmental impacts for all three PLA biorefinery scenarios. This implies that the new PLA pathways do not lead to “strong” eco-efficiency improvement, i.e., the improvement is not in both environmental and economic dimensions. Recommendations are provided to improve the environmental performances of both the existing and the new PLA biorefinery systems. The sugarcane-based PLA biorefinery could be an option for the case that the existing sugar-electricity-ethanol faces an uncertainty on ethanol demand. Nevertheless, there is a trade-off between the increased environmental impacts and the higher price. Strong eco-efficiency improvement must be encouraged to the sugarcane-based PLA biorefinery systems. Using high-pressure boilers at the mills and changing cultivation practices to avoid the cane trash burning are recommended for the better decoupling of the environmental and economic performance of the sugarcane biorefinery systems.

Sugarcane Syrup Improves Xylitol Bioproduction from Sugarcane Bagasse and Straw Hemicellulosic Hydrolysate

To evaluate the supplementation of the sugarcane bagasse and straw hemicellulosic hydrolysate with sugarcane syrup, which is a sucrose-rich co-product, for xylitol production by Candida guilliermondii FTI 20037. Recently, we demonstrated that sucrose supplementation to sugarcane straw hemicellulosic hydrolysate favoured this bioprocess. A mixture 1:1 of sugarcane bagasse and straw was submitted to dilute-acid hydrolysis with H2SO4 to obtain the hemicellulosic hydrolysate, which was concentrated, detoxified and autoclaved. Three sugarcane syrup concentrations (0.83, 2.50 and 3.33% v/v) were added to the hemicellulosic hydrolysate, which was also supplemented with rice bran extract, (NH4)2SO4, CaCl2·2H2O. Next, a full factorial design was performed to assess the replacement of conventional nutrients by sugarcane syrup. Fermentations were performed in 125 mL Erlenmeyer flasks containing 50 mL of fermentation medium, for 48 h at 30 °C and 200 rpm. Improvements of 16.85% and 12.24% in xylose uptake rate (1.04 ± 0.01 g L−1 h−1) and xylitol volumetric productivity (0.55 ± 0.02 g L−1 h−1), respectively, were achieved with syrup supplementation (2.50% v/v), which led to a final xylitol titer of 26.19 ± 0.02 g L−1. Conventionally employed nutrients (rice bran extract, (NH4)2SO4 and CaCl2·2H2O) did not have significant influence on xylitol production when sugarcane syrup was added to the fermentation medium. Sugarcane syrup as a nutritional supplement improved xylitol production from a mixture of bagasse and straw, becoming an alternative to reduce costs in the formulation of the fermentation medium and contributing to the integration of this bioprocess in a sugarcane biorefinery.

Exploring the Introduction of Plug-In Hybrid Flex-Fuel Vehicles in Ecuador

In Europe, diesel combustion is being banned due to the NOx and PM2.5 emissions impact on air quality. The bus sector is being electrified and is increasing its use of alternative fuels, such as natural gas (in spark ignition engines) and bioethanol (in compression ignition engines), to reduce such harmful emissions. Even if a diesel bus is equipped with selective catalytic reduction (SCR), its NOx emissions are reduced its but produces more NH3 emissions that are PM2.5 precursors. In developing countries, the air quality is still barely monitored, however, the air quality issue is well known and is being addressed. Moreover, the Ecuadorian sugar cane industry is seeking ways to increase its ethanol production. This is the ideal framework to explore a new technology and energy source in developing economies such as Ecuador. This paper explores the impact of the Ecuadorian diesel bus fleet conversion to hybrid compression ignition ethanol (HEV-ED95), hybrid diesel and plug-in hybrid flex-fuel using electricity and internal combustion engine ICE-E20 and ICE-E100. The impacts are measured in terms of final energy consumption, criteria pollutant emissions (NH3, NOx, PM2.5) and 100 years global warming potential in a well-to-wheels framework. For the tank-to-wheels data the method follows the typical values of conversion efficiency from final to useful energy (cross checked with a microsimulation model), the Tier 2 European Environmental Agency approach combined with ethanol influence on compression ratio, lower heating value, criteria emissions taken from a literature review, and well-to-tank emission factors for electricity (10–58% thermal natural gas or coal powerplant contribution), for ethanol from banana industry wastes (ED95, E20 and E100), gasoline and diesel from US databases. A discussion on whether sugarcane biorefineries are necessary is highlighted in the results. All input parameters have an uncertainty range between a minimum and a maximum and the probability for each is giving by a uniform distribution.

Exergoeconomic analysis of lactic acid and power cogeneration from sugarcane residues through a biorefinery approach

The present survey was devoted to exergoeconomically investigating a lignocellulosic-based sugarcane biorefinery developed for cogeneration of lactic acid and power from sugarcane bagasse and harvesting residues, specifically brown leaves (trash). More specifically, this research was aimed at identifying the hotspots of the cost losses in the developed biorefinery. Exergoeconomic parameters including irreversibility-related cost rate, component-related cost rate, total cost rate, relative cost difference, and exergoeconomic factor were determined for all the nine subunits of the biorefinery. In addition, two new exergoeconomic variables called “economic impact ratio” and “economic modification requirement index” were introduced and elaborated throughout this study. After obtaining cost balances for all subunits of the biorefinery, product and fuel rules were considered according to Specific Exergy Costing (SPECO) approach for determining the unit exergoeconomic cost of all streams involved in the process. The unit exergoeconomic costs of lactic acid, power, steam, and liquid digestate were found to be 8.55, 15.61, 15.61, and 17.96 USD/GJ, respectively. The highest total cost rate was determined at 3715.86 USD/h for the steam generation unit, accounting for 43.73% of the total cost rate of the biorefinery. The lactic acid synthesis unit stood in the next rank, contributing to 20.49% of the total cost rate of the system. Overall, attempts to promote the exergoeconomic performance of the biorefinery must mainly focus on minimizing the irreversibility-related cost rate of the steam generation unit.

Simulating scenarios for compost and vinasse use to improve the economics and environmental aspects of representative Colombian sugarcane production systems

AbstractThe Colombian industrial sector is moving toward alternative forms of treatment of industrial waste, considering that the waste can be a source of raw material in the production chain. Thus, aiming at the decrease in mineral fertilizer use, and maintaining or even raising the crop yield, the sugarcane industry has recently advanced in the composting of the industrial waste and application in the field, both of them being potentially sustainable practices. This manuscript reports the economic benefits and the greenhouse gas (GHG) emissions related to the sugarcane production system in Colombia that has been simulated in this study to evaluate the beneficial effects of reusing industrial waste from ethanol production. This study was performed using the Virtual Sugarcane Biorefinery (VSB) modeling software for the simulation of agricultural and industrial parameters on integrated alternatives for the sugarcane industry. Colombian sugarcane sector was modeled using three scenarios representing agricultural systems that do not use composted industrial waste vs a paired scenario for each condition where composted waste is utilized. Regarding compost and vinasse use as fertilizer and soil conditioner, GHG emissions from the biogenic origin are not included as a reported item in the matrix of GHG emissions of the sugarcane sector. Inputs for the economic and environmental assessment models are based on actual operational data from two mill sites, one located in the traditional sugarcane production region of Cauca River Valley and the other one, on the agricultural expansion region of Llanos Orientales. Here, we have found that the reuse of composted industrial waste is beneficial and provides an economic cost savings of 2–6% per year. However, it also results in an annual increase of 10–20% in the GHG emissions.