Energy balance optimization of sugarcane crop residual biomass

This work presents a mathematical model for helping mills choose sugarcane varieties for planting. It maximizes crop residual biomass energy balance by considering the difference between generated and consumed energy in the process of transferring this biomass from the field to the processing center; it takes into account enterprise demand restrictions and cane planting area. For this full zero-one linear programming techniques were proposed. The model is viable for choosing sugarcane varieties that would benefit sugarcane production and industrial systems, by reducing crop residue and increasing final energy production.     

Sugar-ethanol-electricity co-generation in Hawai’i: An application of linear programming (LP) for optimizing strategies

This research develops a linear programming (LP) model to assess various options for sugar and biofuel production from sugarcane and other feedstock in Hawaii. More specifically, the study focuses on finding optimal sugar and biomass feedstock that would maximize producer profits in the production of sugar, ethanol and electricity. Feedstock included in the model were sugarcane, banagrass, energy cane and sweet sorghum. Given available land resources for growing energy crops on the island of Maui, four land resource scenarios were considered. If available land resources were used in the production of sugarcane and energy crops with added utilization of non-prime lands, Hawaii's ethanol goal for year 2020 could be achieved while maintaining two-thirds of Hawaii's current sugar production. Crop yields and unit production costs are key factors in determining optimal quantities of feedstock in the optimization model tested in this study.     

Optimizing ethanol and bioelectricity production in sugarcane biorefineries in Brazil

In sugarcane biorefineries, the lignocellulosic portion of the sugarcane biomass (i.e. bagasse and cane trash) can be used as fuel for electricity production and/or feedstock for second generation (2G) ethanol. This study presents a techno-economic analysis of upgraded sugarcane biorefineries in Brazil, aiming at utilizing surplus bagasse and cane trash for electricity and/or ethanol production. The study investigates the trade-off on sugarcane biomass use for energy production: bioelectricity versus 2G ethanol production. The BeWhere mixed integer and spatially explicit model is used for evaluating the choice of technological options. Different scenarios are developed to find the optimal utilization of sugarcane biomass. The study finds that energy prices, type of electricity substituted, biofuel support and carbon tax, investment costs, and conversion efficiencies are the major factors influencing the technological choice. At the existing market and technological conditions applied in the upgraded biorefineries, 300 PJ y⁻¹ 2G ethanol could be optimally produced and exported to the EU, which corresponds to 2.5% of total transport fuel demand in the EU. This study provides a methodological framework on how to optimize the alternative use of agricultural residues and industrial co-products for energy production in agro-industries considering biomass supply chains, the pattern of domestic energy demand, and biofuel trade.     

Life-cycle greenhouse gas emissions and energy balances of sugarcane ethanol production in Mexico

The purpose of this work was to estimate GHG emissions and energy balances for the future expansion of sugarcane ethanol fuel production in Mexico with one current and four possible future modalities. We used the life cycle methodology that is recommended by the European Renewable Energy Directive (RED), which distinguished the following five system phases: direct Land Use Change (LUC); crop production; biomass transport to industry; industrial processing; and ethanol transport to admixture plants. Key variables affecting total GHG emissions and fossil energy used in ethanol production were LUC emissions, crop fertilization rates, the proportion of sugarcane areas that are burned to facilitate harvest, fossil fuels used in the industrial phase, and the method for allocation of emissions to co-products. The lower emissions and higher energy ratios that were observed in the present Brazilian case were mainly due to the lesser amount of fertilizers applied, also were due to the shorter distance of sugarcane transport, and to the smaller proportion of sugarcane areas that were burned to facilitate manual harvest. The resulting modality with the lowest emissions of equivalent carbon dioxide (CO_2e) was ethanol produced from direct juice and generating surplus electricity with 36.8 kgCO_2e/GJ_ethanol. This was achieved using bagasse as the only fuel source to satisfy industrial phase needs for electricity and steam. Mexican emissions were higher than those calculated for Brazil (27.5 kgCO_2e/GJ_ethanol) among all modalities. The Mexican modality with the highest ratio of renewable/fossil energy was also ethanol from sugarcane juice generating surplus electricity with 4.8 GJ_ethanol/GJ_fossil.     

Biowaste energy potential in Kenya

Energy affects all aspects of national development. Hence the current global energy crisis demands greater attention to new initiatives on alternative energy sources that are renewable, economically feasible and sustainable. The agriculture-dependent developing countries in Africa can mitigate the energy crisis through innovative use of the available but underutilised biowaste such as organic residues from maize, barley, cotton, tea and sugarcane. Biogas technology is assumed to have the capacity to economically and sustainably convert these vast amounts of biowaste into renewable energy, thereby replacing the unsustainable fossil energy sources, and reducing dependency on fossil fuels. However, the total energy potential of biogas production from crop residues available in Kenya has never been evaluated and quantified. To this end, we selected five different types of residues (maize, barley, cotton, tea and sugarcane) from Kenya and evaluated their energy potential through biomethane potential analysis at 30 °C and a test time of 30 days.The specific methane yields for maize, barley, cotton, tea and sugarcane residues obtained under batch conditions were respectively 363, 271, 365, 67 and 177 m³ per tonne volatile solids. In terms of energy potential, maize, cotton and barley residues were found to be better substrates for methane production than tea and sugarcane residues and could be considered as potential substrates or supplements for methane production without compromising food security in the country. The evaluated residues have a combined national annual maximum potential of about 1313 million cubic meters of methane which represent about 3916 Gigawatt hour (GWh) of electricity and 5887 GWh of thermal energy. The combined electrical potential is equivalent to 73% of the country’s annual power production of 5307 GWh. Utilization of the residues that are readily available on a ‘free on site’ basis for energy production could substitute the fossil fuels that account for a third of the country’s total electricity generation. Besides, exploitation of the potential presented by the biowaste residues can spur an energy revolution in the country resulting in a major economic impact in the region.     

Comparing biological and thermochemical processing of sugarcane bagasse: An energy balance perspective

The technical performance of lignocellulosic enzymatic hydrolysis and fermentation versus pyrolysis processes for sugarcane bagasse was evaluated, based on currently available technology. Process models were developed for bioethanol production from sugarcane bagasse using three different pretreatment methods, i.e. dilute acid, liquid hot water and steam explosion, at various solid concentrations. Two pyrolysis processes, namely fast pyrolysis and vacuum pyrolysis, were considered as alternatives to biological processing for the production of biofuels from sugarcane bagasse. For bioethanol production, a minimum of 30% solids in the pretreatment reactor was required to render the process energy self-sufficient, which led to a total process energy demand equivalent to roughly 40% of the feedstock higher heating value. Both vacuum pyrolysis and fast pyrolysis could be operated as energy self-sufficient if 45% of the produced char from fast pyrolysis is used to fuel the process. No char energy is required to fuel the vacuum pyrolysis process due to lower process energy demands (17% compared to 28% of the feedstock higher heating value). The process models indicated that effective process heat integration can result in a 10-15% increase in all process energy efficiencies. Process thermal efficiencies between 52 and 56% were obtained for bioethanol production at pretreatment solids at 30% and 50%, respectively, while the efficiencies were 70% for both pyrolysis processes. The liquid fuel energy efficiency of the best bioethanol process is 41%, while that of crude bio-oil production before upgrading is 67% and 56% via fast and vacuum pyrolysis, respectively. Efficiencies for pyrolysis processes are expected to decrease by up to 15% should upgrade to a transportation fuel of equivalent quality to bioethanol be taken into consideration.     

Energy from sugarcane bagasse under electricity rationing in Brazil: a computable general equilibrium model

In the midst of the institutional reforms of the Brazilian electric sectors initiated in the 1990s, a serious electricity shortage crisis developed in 2001. As an alternative to blackout, the government instituted an emergency plan aimed at reducing electricity consumption. From June 2001 to February 2002, Brazilians were compelled to curtail electricity use by 20%. Since the late 1990s, but especially after the electricity crisis, energy policy in Brazil has been directed towards increasing thermoelectricity supply and promoting further gains in energy conservation. Two main issues are addressed here. Firstly, we estimate the economic impacts of constraining the supply of electric energy in Brazil. Secondly, we investigate the possible penetration of electricity generated from sugarcane bagasse. A computable general equilibrium (CGE) model is used. The traditional sector of electricity and the remainder of the economy are characterized by a stylized top-down representation as nested CES (constant elasticity of substitution) production functions. The electricity production from sugarcane bagasse is described through a bottom-up activity analysis, with a detailed representation of the required inputs based on engineering studies. The model constructed is used to study the effects of the electricity shortage in the preexisting sector through prices, production and income changes. It is shown that installing capacity to generate electricity surpluses by the sugarcane agroindustrial system could ease the economic impacts of an electric energy shortage crisis on the gross domestic product (GDP).     

An experimental study on solar evaporation of sugarcane juice

In this study, an attempt is made to obtain concentrated sugarcane juice and distilled water using solar radiations that would save energy as well as environment. In this study work, the experimental performance of a sugarcane juice solar evaporation system (SJSES) is investigated for the evaporation of water from sugarcane juice. To check the influence of flow rate on the performance of SJSES units, experiments are carried out at 20, 25, 30, and 35 ml/min. The flow of sugarcane juice at 25 ml/min in SJSES unit is found optimum that resulted in highest energy saving, distilled water, and relatively more brix content of final product. The performance of SJSES unit loaded with paraffin wax at optimum flow rate (unit IV) resulted in maximum distilled water (605.1 g) which is 82.4%, 14.8%, and 39.4% higher than other units. Paraffin wax loading in SJSES increased its distillate output, brix of juice, and working time by 78.3 g, 7.9%, and 1 h, respectively. Thermal and exergy efficiencies are found maximum for unit IV having values 58.56% and 4.53%, respectively. The amount of energy saved is observed maximum for this unit along with least distillate cost and payback period.     

Determination of the optimal quantity of crop residues for energy in sugarcane crop management using linear programming in variety selection and planting strategy

The aim of this work was to present organizational models for optimizing the reduction of crop residue generated by the sugarcane culture. The first model consisted of the selection of varieties of sugarcane to be planted meeting the mill requirements and, at the same time, to minimize the quantity of residue produced. The second model discussed the use of residue to produce energy. This is related to the selection of variety and quantity to be planted, in order to meet the requirements of the mill, to reduce the quantity of residue, and to maximize as much as possible the energy production. The use of linear programming was proposed. The two models presented similar results in this study, and both may be used to define the varieties and areas to be cultivated.     

Biological saccharification by Clostridium thermocellum and two-stage hydrogen and methane production from hydrogen peroxide-acetic acid pretreated sugarcane bagasse

The present work aimed at establishing an efficient degradation and energy recovery system form sugarcane bagasse (SCB) through hydrogen peroxide-acetic acid (HPAC) pretreatment, thermophilic hydrogen production and mesophilic methane production. The degradation ratio of HPAC pretreated SCB (HPAC-SCB, 2%, w/v) exceeded 90% under the biological hydrolysis of C. thermocellum without enzyme addition. The hydrogen yield in the co-culture fermentation of T. thermosaccharolyticum and C. thermocellum from HPAC-SCB (2%, w/v) reached 226 mL/g substrate. The long-term hydrogen fermentation was successfully established with 1.59 L/(L·d), 0.159 L/g substrate for average hydrogen productivity and yield, respectively. Methane production of 0.341 L/g COD (chemical oxygen demand)_added was recovered by semi-continuous methane fermentation from hydrogen-producing effluent at 12 days of hydraulic retention time (HRT). Average energy recovery of 8.79 MJ/kg SCB was obtained under the optimal conditions. The present work indicated the promising application of the established process in valorization of lignocellulosic bio-waste.     

Power plant perspectives for sugarcane mills

Biomass, integral to life, is one of the main energy sources that modern technologies could widely develop, overcoming inefficient and pollutant uses. The sugarcane bagasse is one of the more abundant biomass. Moreover, the fluctuating sugar and energy prices force the sugarcane companies to implement improved power plants. Thanks to a multiyear collaboration between University of Rome and University of Piura and Chiclayo, this paper investigates, starting from the real data of an old sugarcane plant, the energy efficiency of the plant. Furthermore, it explores possible improvements as higher temperature and pressure Rankine cycles and innovative configurations based on gasifier plus hot gas conditioning and gas turbine or molten carbonate fuel cells. Even if the process of sugar extraction from sugarcane and the relative Rankine cycles power plants are well documented in literature, this paper shows that innovative power plant configurations can increase the bagasse-based cogeneration potential. Sugarcane companies can become electricity producers, having convenience in the use of sugarcane leaves and trash (when it is feasible). The worldwide implementation of advanced power plants, answering to a market competition, will improve significantly the renewable electricity produced, reducing CO₂ emissions, and increasing economic and social benefits.     

Methodological considerations of irrigation energetics

Methods are described to assess the total energy inputs for the irrigation of different crops. Energy yields as main products such as grain and as total biomass have been worked out. This methodology is illustrated with data from a sample farm growing wheat, paddy, berseem, sorghum fodder, and sugarcane. Energy inputs have been computed for the primary fuels used to generate electricity for pumping water. Fixed inputs embodied in materials, equipment and labor have been amortized for their expected lifetime. Compared to the energy yields in the main products, inputs in irrigation involved 6.8% for sorghum fodder, 13.9% for berseem, 15.2% for wheat, 15.9% for sugarcane, and 37.0% for rice.     

Sustainable ethanol production from lignocellulosic biomass - Application of exergy analysis

The sustainability of the second-generation biofuels requests to confirm that the energy produced from lignocellulosic biomass is significantly greater than the energy consumed in the process. As lignocellulosic biomass does not affect the food supply, sugarcane bagasse was analyzed as a raw material for second-generation biofuels production. Exergy analysis serves as a unified and effective tool to evaluate the global process efficiency. Exergy analysis evaluates the performance of sugarcane bagasse and its sustainability in the bioethanol production process. In this work, four ethanol production topologies using the typical daily amount of residual biomass produced by the sugar industry were compared. The exergy analysis concept is effective in screening design alternatives with the lowest environmental impact for second-generation bioethanol fuel production from renewable resources. This study was executed by the use of the Aspen Plus^® program and other software developed by the authors.     

Policies for improving the efficiency of the Brazilian light-duty vehicle fleet and their implications for fuel use,greenhouse gas emissions and land use

The increase in greenhouse gas concentrations in the atmosphere, energy security issues and competition for land use are putting pressure on governments and policymakers. However, these three subjects are not usually treated in integrated form. This paper shows that the implementation of energy efficiency policies combined with policies to encourage use of biofuels can help reduce greenhouse gases emissions while easing land use competition from sugarcane ethanol in Brazil. By adapting the ADVISOR (Advanced Vehicle Simulator) software to evaluate vehicle efficiency, and by estimating the Brazilian light-duty vehicle market share based on historical data, this paper estimates the possible levels of GHG emissions and area planted with sugarcane in 2030 in the country. The findings indicate that reductions from 8% to 20% in greenhouse gas emissions and 0.9–1.8 million ha in sugarcane planted area are possible with no significant technological breakthroughs over the horizon to 2030 in comparison with a baseline scenario.     

Sugarcane energy use: The Cuban case

This paper examines the history, methods, costs, and future prospects of Cuba's attempts to develop the energy potential of sugarcane. An overview of the main factors affecting the current sugarcane agro-industry in Cuba is provided, along with an analysis of why, despite attempts by the Cuban government to revive the country's sugarcane agro-industry, the industry continues to decline.

The prevailing conditions and degree of modernization in Cuban sugar factories are evaluated. The sugar-agro industry's main production bottlenecks are studied. The fall in sugarcane yield from 57.5 ton/ha in 1991 to 22.4 ton/ha in 2005 and its relation to land use is explained. The socio-economic impact of the sugarcane agro-industry's downsizing is assessed. The governmental and quasi-governmental entities in charge of sugarcane energy use development and the country's legal framework are analyzed. The Cuban sugarcane agro-industry's opportunities in the growing international biofuels and bioenergy market are evaluated. To situate Cuba within the global bioenergy market, international best practices relating to the production and commercialization of biofuels are examined to determine the degree to which these experiences can be transferred to Cuba.

The analysis of the Cuba sugar industry's biofuel potential is based on a comparative technical–economic assessment of three possible production scenarios: (1) the current situation, where only sugar is produced; (2) simultaneous production of sugar–anhydrous ethanol; and (3) production of sugar–ethanol and simultaneous generation of surplus electricity exported to a public grid.

Some of the key assumptions underlying these analyses are as follows: Ethanol production and operation costs for a 7000 ton/day-sugar mill are estimated to be 0.25 and 0.23 USD/l, respectively. The influence of gasoline prices on sugar–ethanol production is also assessed. The kWh production and operation costs starting from sugarcane bagasse are estimated at 0.06 and 0.04 USD, respectively. Cuba's potential sugarcane cogeneration capacity is estimated to be 9006 GWh/year. Investment–profit analyses are offered for two scenarios: annexing a 300,000 l/day distillery to a sugar mill, and enlarging the cogeneration capacity of a 7000 ton/day mill. Added production cost/added-value analysis was carried out. The main environmental issues associated with sugarcane-based fuel production are also analyzed.     

Energy analysis and options of Indian agriculture

Agriculture accounts for most of the energy consumed in India. Non-commercial sources may be insufficient for food production. Substitutes or alternatives have to be developed for some agricultural products. It is feasible to produce cheaper acceptable substitutes for sugar (from crop residues), milk (from corn), animal feeds (from waste recycling), etc. Physical inputs and outputs transformed to energy were used to evaluate energy utilization in agriculture. Major inputs were farmyard manure (FYM), irrigation, bullocks, and farm equipment. Inputs were computed from the stage of primary fuels. Tubewell irrigation consumed 9.4 GJ/ha and accounted for 6.8% of the energy output of sorghum fodder, 13.9% of berseem, 15.2% of wheat grain, 15.9% of sugar, and 37.0% of rice. Inputs were 249–324 MJ/cm-ha in different crops. Fully utilized, the minimum energy inputs through equipment for one hectare of wheat would be 9.2 GJ on bullock-operated farms and 5.9 GJ on tractor-operated farms. Actually, because of small farm sizes, use is 29.2 GJ on bullock-powered farms and 8.3 GJ on farms with tractors. Costs of wheat production are about 40% higher on bullock-operated farms. Pest and weed control account for less than 2% of the energy inputs of crops. Energy returns as grain are 99% for wheat, 76–90% for rice, 17–28% for corn, and 52% for planted sugar and 103% in ratooned sugar cane. An annual crop rotation of paddy and wheat in Haryana consumed less energy and yields more energy (edible and as biomass) than sugar cane.Rural fuel supplies being marginal, dung is preferentially used as fuel and hardly 10% of the recommended levels of FYM are applied. Energy utilization from dung as fuel is double that as fertilizer replacement. Biogas will not be the fuel of the poor and will force them to fell vegetation for cooking fuel. Solar cookers are promising alternatives. Considering the extensive needs for low (or no) cost cooking fuel, we conclude that the Indian energy economy (and agriculture) will improve by using more fertilizers (and less FYM) and farm machinery (with reduced dependence on bullocks). Farm residues and other biomass may be processed to augment supplies of domestic and industrial fuels.     

Power requirements and field performance in harvesting energycane and sugarcane

Energycane is emerging as a candidate bioenergy crop, and it resembles sugarcane in stature and cultivation practices. Preliminary trials indicated that sugarcane billet harvesters have insufficient power to harvest energycane. This study quantified the power requirements of selected harvester components and field performance of harvesters for sugarcane and energycane. The elevator pour rate for energycane was lower (43.3 Mg h⁻¹, wet weight) than for sugarcane (132.7 Mg h⁻¹, wet weight). At the observed pour rates, power consumption of the basecutter, elevator, and the entire harvester was comparable for energycane and sugarcane. However, the power requirements of the chopper were 1.65 times higher for energycane than for sugarcane. Greater stem damage and higher stubble heights were observed for energycane compared to sugarcane. Overflowing of the elevator was observed for energycane because of lower bulk density of the biomass (billets and trash, 143.8 kg m⁻³) compared to sugarcane (predominantly billets, 349.4 kg m⁻³). The field capacity of the harvester for energycane (0.32 ha h⁻¹) was lower than for sugarcane (0.61 ha h⁻¹), and the harvesting cost for energycane (5.91 $ Mg⁻¹) was considerably higher than for sugarcane (1.87 $ Mg⁻¹). Design modifications to the existing sugarcane harvester models would be needed to adapt them to harvest energycane.     

Influence of biomass waste from agro-industries on obtaining energetic gases assisted by chronoamperometric process

The generation of energy by thermoelectric plants powered by biomass in Brazil has grown by ～3% in the last three years. In 2016, 8.8% of the electric energy in Brazil was generated using biomass as an input. However, the generation of residues and the possibility of reapproaching have motivated the planning and uses of electrochemical processes to evaluate the obtained gases (mainly hydrogen and carbon monoxide) as clean energy sources. Although thermochemical processes using biomass as an energy source already exist, few reports regarding the study of this process through electrolysis are available. Herein, we describe a water electrolysis process using sugarcane bagasse, rice husk, and malt bagasse as biomass residues to obtain gases with potential uses as clean energy sources and analyze the mass concentration influences on the behavior of the electrochemical solution. Tafel and cyclic voltammetry analyzes showed a tendency to decrease the kinetics and current of the system with the increase of the biomass residue concentration in the solution. In contrast, sugarcane bagasse concentrations of 0.1%–1% increase the current. The faradaic efficiency and partial current density analysis confirm the results obtained from cyclic voltammetry for hydrogen production, with less faradaic efficiency for hydrogen and reduced current values in the system when the biomass residue concentration is higher. The production efficiency of carbon monoxide formed at the anode increases with the concentration for sugarcane bagasse (2.01–5.21 μA/cm²) with 1% of the biomass in solution.     

A mathematical,economic and energetic appraisal of biomethane and biohydrogen production from Brazilian ethanol plants' waste: Towards a circular and renewable energy development

The high production of sugarcane in Brazil and its application of ethanol and sugar production results in a higher generation of vinasse and bagasse. The treatment of these residues can be carried out using anaerobic co-digestion procedures. Besides promoting waste treatment, it enables energy exploration through biogas and hydrogen generation. Bioenergy use can also generate steam in sugar and alcohol plants by burning, sugarcane milling, fueling vehicles for the transport of products, among others. These energy applications allow total and efficient, energetic exploring of sugarcane. Hence, this study estimated the production of methane, hydrogen, thermal and electrical energy generated from vinasse and bagasse in the autonomous and annexed Brazilian ethanol and sugar plants. Three scenarios present the use of biogas generated: Scenario 1: energy use of all methane from biogas; Scenario 2: hydrogen production from the remaining methane, after considering the energy autonomy of the ethanol plants; Scenario 3: hydrogen production from all the methane generated. All the scenarios which considered the use of methane led to energy self-sufficiency in the sector. However, only annexed plants present economic feasibility for implementing the project. Scenario 2 is highlighted in this study, once beyond the sector's energetic self-sufficiency, the operational conditions enabled the storage of 9.26E+07 Nm³.d^?1 of hydrogen, equal 3.04E+08 ton per year. CH₄ and H₂ production seen in a global scenario of circular economy and energy security have high benefits, contributing to the gradual transformation of an economy dependent on non-renewable resources into a circular and renewable economy.