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.     

Main routes for the thermo-conversion of biomass into fuels and chemicals. Part 1: Pyrolysis systems

Since the energy crises of the 1970s, many countries have become interest in biomass as a fuel source to expand the development of domestic and renewable energy sources and reduce the environmental impacts of energy production. Biomass is used to meet a variety of energy needs, including generating electricity, heating homes, fueling vehicles and providing process heat for industrial facilities. The methods available for energy production from biomass can be divided into two main categories: thermo-chemical and biological conversion routes. There are several thermo-chemical routes for biomass-based energy production, such as direct combustion, liquefaction, pyrolysis, supercritical water extraction, gasification, air–steam gasification and so on. The pyrolysis is thermal degradation of biomass by heat in the absence of oxygen, which results in the production of charcoal (solid), bio-oil (liquid), and fuel gas products. Pyrolysis liquid is referred to in the literature by terms such as pyrolysis oil, bio-oil, bio-crude oil, bio-fuel oil, wood liquid, wood oil, liquid smoke, wood distillates, pyroligneous tar, and pyroligneous acid. Bio-oil can be used as a fuel in boilers, diesel engines or gas turbines for heat and electricity generation.     

Catalytic fast pyrolysis of sugarcane bagasse pith with HZSM-5 catalyst using tandem micro-reactor-GC-MS

Fast pyrolysis of biomass is praised as an efficient and feasible process to selectively convert lignocellulosic biomass into bio-fuels and bio-chemicals. Pith of sugarcane bagasse could be an attractive lignocellulosic waste from depithing process from pulp and paper mill, which can utilize for production of biofuel and added value products. In this study, we employed a tandem micro-reactor coupled with gas chromatography-mass spectroscopy to investigate the products distribution from pith of sugarcane bagasse via catalytic fast pyrolysis. In the operating conditions, pyrolysis temperature and HZSM-5 catalyst had significant effect on products and distributions. An increase in the pyrolysis temperature from 400°C to 550°C led to an increase in the yield of phenolic compounds (6.3%, w/w%), followed decrease at higher temperature. The maximum carboxylic acids (10.6%) and furfural (3.5%) were obtained at lower temperature. At presence of HZSM-5 catalyst, the selectivity of aromatics such as benzene, toluene, indene, and naphthalene were improved.     

生物质燃料层热解过程的传热传质模型研究

通过分析生物质热解过程的传热传质特点,建立了生物质燃料层热解过程的传热传质教学模型。通过数值计算,研究了生物质燃料层在热解过程中所发生的热量和质量迁移现象,分析了热解过程生物质床内部温度场的分布、生物质固体密度的变化和热解区的迁移规律。     

Electricity,hot water and cold water production from biomass. Energetic and economical analysis of the compact system of cogeneration run with woodgas from a small downdraft gasifier

Wood gasification technologies to convert the biomass into fuel gas stand out. On the other hand, producing electrical energy from stationary engine is widely spread, and its application in rural communities where the electrical network doesn’t exist is very required. The recovery of exhaust gases (engine) is a possibility that makes the system attractive when compared with the same components used to obtain individual heat such as electric power. This paper presents an energetic alternative to adapt a fixed bed gasifier with a compact cogeneration system in order to cover electrical and thermal demands in a rural area and showing an energy solution for small social communities using renewable fuels. Therefore, an energetic and economical analysis from a cogeneration system producing electric energy, hot and cold water, using wooden gas as fuel from a small-sized gasifier was calculated. The energy balance that includes the energy efficiency (electric generation as well as hot and cold water system; performance coefficient and the heat exchanger, among other items), was calculated. Considering the annual interest rates and the amortization periods, the costs of production of electrical energy, hot and cold water were calculated, taking into account the investment, the operation and the maintenance cost of the equipments.     

Modeling of hydrogen production process from biomass using oxygen blown gasification

Hydrogen has a great potential as fuel of the future and biomass can be a useful resource for the production of hydrogen. In the present work, a thermodynamic model has been developed to evaluate the yield of hydrogen from biomass through gasification in an oxygen-rich environment followed by carbon monoxide shift reaction with the injection of water. The effects of operating conditions, like gasifier equivalence ratio, quantity of water injected in the shift reactor and oxygen percentage in the gasifying agent, on the hydrogen concentration in the product gas from biomass have been evaluated. It is predicted that the process can generate 102 g hydrogen per kg of biomass, resulting in a cold gas efficiency of 65.4%. However, the air separation unit consumes a considerable amount of work in compression and refrigeration and these would decrease the overall efficiency by about 3.6 percentage points in a 5-stage compressor system.     

Well-to-Wheels analysis of hydrogen production from bio-oil reforming for use in internal combustion engines

The environmental profile of hydrogen depends greatly on the nature of the feedstock and the production process. In this Well-to-Wheels (WTW) study, the environmental impacts of hydrogen production from lignocellulosic biomass via pyrolysis and subsequent steam reforming of bio-oil were evaluated and compared to the conventional production of hydrogen from natural gas steam reforming. Hydrogen was assumed to be used as transportation fuel in an internal combustion engine vehicle. Two scenarios for the provision of lignocellulosic biomass were considered: wood waste and dedicated willow cultivation. The WTW analysis showed that the production of bio-hydrogen consumes less fossil energy in the total lifecycle, mainly due to the renewable nature of the fuel that results in zero energy consumption in the combustion step. The total (fossil and renewable) energy demand is however higher compared to fossil hydrogen, due to the higher process energy demands and methanol used to stabilize bio-oil. Improvements could occur if these are sourced from renewable energy sources. The overall benefit of using a CO₂ neutral renewable feedstock for the production of hydrogen is unquestionable. In terms of global warming, production of hydrogen from biomass through pyrolysis and reforming results in major GHG emissions, ranging from 40% to 50%, depending on the biomass source. The use of cultivated biomass aggravates the GHG emissions balance, mainly due to the N₂O emissions at the cultivation step.     

Thermodynamic modeling of direct internal reforming solid oxide fuel cells operating with syngas

In this paper a direct internal reforming solid oxide fuel cell (DIR-SOFC) is modeled thermodynamically from the energy point of view. Syngas produced from a gasification process is selected as a fuel for the SOFC. The modeling consists of several steps. First, equilibrium gas composition at the fuel channel exit is derived in terms mass flow rate of fuel inlet, fuel utilization ratio, recirculation ratio and extents of steam reforming and water–gas shift reaction. Second, air utilization ratio is determined according to the cooling necessity of the cell. Finally, terminal voltage, power output and electrical efficiency of the cell are calculated. Then, the model is validated with experimental data taken from the literature. The methodology proposed is applied to an intermediate temperature, anode-supported planar SOFC operating with a typical gas produced from a pyrolysis process. For parametric analysis, the effects of recirculation ratio and fuel utilization ratio are investigated. The results show that recirculation ratio does not have a significant effect for low current density conditions. At higher current densities, increasing the recirculation ratio decreases the power output and electrical efficiency of the cell. The results also show that the selection of the fuel utilization ratio is very critical. High fuel utilization ratio conditions result in low power output and air utilization ratio but higher electrical efficiency of the cell.     

生物质液化技术面临的挑战与技术选择

生物质液化技术可将低品位的固体生物质完全转化成高品位的液体燃料或化学品,是生物质能高效利用的主要方式之一。按照机理,液化技术可以分为热化学法、生化法、酯化法和化学合成法(间接液化),热化学法液化又分为快速热解技术和高压液化(直接液化)技术。生物质热化学法液化已成为国内外生物质液化的研究开发重点和热点,快速热解液化技术和高压液化技术是最具产业化前景的生物质能技术,生化法液化技术也是生物质能的研究热点。化学合成法液化技术并不适用于生物质液化,而利用生物柴油进一步生产生物航空煤油是得不偿失的,不仅成本高、资源利用率低,而且全生命周期碳排放增加,还不符合未来生物航煤的发展趋势。生物质含水量的高低是影响生物质液化过程中能耗、效率、污染指数和经济性指标等的关键因素,应根据含水量合理选择生物质液化技术。快速热解液化技术适用于低含水农林废弃物,高压液化和生化法液化技术适用于高含水生物质,酯化法液化技术适用于不可食用油脂,而各种液化技术均不适用于城市生活垃圾的处理,建议将其用作燃气型气化原料。     

The use of biomass syngas in IC engines and CCGT plants: A comparative analysis

This paper studies the use of biomass syngas, obtained from pyrolysis or gasification, in traditional energy-production systems, specifically internal combustion (IC) engines and combined cycle gas turbine (CCGT) plants. The biomass conversion stage has been simulated by means of a gas–solid thermodynamic model. The IC and CCGT plant configurations were optimised to maximise heat and power production. Several types of biomass feedstock were studied to assess their potential for energy production and their effect on the environment. This system was also compared with the coupling between biomass gasification and fuel cells.     

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.     

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.     

Continuous hydrogen production by biomass gasification in supercritical water heated by molten salt flow: System development and reactor assessment

Hydrogen production by biomass gasification using solar energy is a promising approach for overcoming the drawbacks of fossil fuel utilization, but the storage of discontinuous solar flux is a critical issue for continuous solar hydrogen production. A continuous hydrogen production system by biomass gasification in supercritical water using molten-salts-stored solar energy was proposed and constructed. A novel double tube helical heat exchanger was designed to be molten salts reactor for hydrogen production. Model compounds (glycerol/glucose) and real biomass (corn cob) were successfully gasified in this molten salts reactor for producing hydrogen-rich gas. The unique temperature profiles of biomass slurry in the reactor were observed and compared with that of conventional electrical heating and direct solar heating approaches. Product gases yield, gasification efficiency and exergy conversion efficiency of the reactor were analyzed. The results showed that the performances of reactor were determined by feedstock style, biomass concentration, residence time and biomass slurry temperature profiles.     

Electrodes based on nafion and epoxy-graphene composites for improving the performance and durability of open cathode fuel cells,prepared by electrospray deposition

Fabrication of electrodes for polymer electrolyte fuel cells is a intriguing process in which a balance between gas transport, electrical conductivity, proton transport and water managing must be optimized. In this work four different electrodes prepared by electrospray deposition have been studied using different catalytic inks, in which Nafion and epoxy doped with Graphene-Nanoplatelets were used as binders. After studying the behavior of those electrodes in a single open cathode fuel cell proton electrolyte membrane, it is clear that the addition of epoxy as binder doped with graphene, improves the performance of the fuel cell and increase the mechanical stability of the electrode avoiding the loose of catalyst during the electrode manipulation in the fuel cell assembly process and the durability of the fuel cell. To explain this behavior, an ex-situ study was carried out, in which properties such as its surface morphology, hydrophobicity and electrical and thermal conductivity of those electrodes were studied. From the results of this study, such improvement in the performance of the fuel cell was justified on the basis of the increase in the electrical conductivity, a diminution in its thermal conductivity and an enhancement of hydrophobicity (surface morphology) of the deposited catalyst layer, when an optimum quantity of epoxy is added to the catalytic ink that makes to improve the mechanical properties of those electrodes.     

A review on operating parameters for optimum liquid oil yield in biomass pyrolysis

Pyrolysis is one of the potential routes to harness energy and useful chemicals from biomass. The major objective of biomass pyrolysis is to produce liquid fuel, which is easier to transport, store and can be an alternative to energy source. The yield and composition of pyrolysis oil depend upon biomass feedstock and operating parameters. It is often necessary to explore about the effect of variables on response yield and instinct about their optimization. This study reviews operating variables from existing literature on biomass pyrolysis. The major operating variables include final pyrolysis temperature, inert gas sweeping, residence times, rate of biomass heating, mineral matter, size of biomass particle and moisture contents of biomass. The scope of this paper is to review the influence of operating parameters on production of pyrolysis oil.     

Life-cycle analysis of greenhouse gas emission and energy efficiency of hydrogen fuel cell scooters

The well-to-wheels (WTW) analysis of energy conservation and greenhouse gas emission of advanced scooters associated with new transportation fuels is studied in the present work. Focus is placed on fuel cell scooter technologies, while the gasoline-powered scooter equipped with an internal combustion engine (ICE) serves as a reference technology. The effect of various pathways of hydrogen production on the well-to-tank (WTT) efficiency for energy is examined. Both near-term and long-term hydrogen production options are explored, such as purification of coke oven gas (COG), steam reforming of natural gas, water electrolysis by generation mix and renewable electricity, and gasification of herbaceous biomass. Then, the WTW efficiency of fuel cell scooters for various hydrogen production options is compared with that of the conventional ICE scooters and electric scooters. Results showed that the fuel cell scooters fueled with COG-based hydrogen could achieve the highest reduction benefits in energy consumption and GHG emission. Finally, the potential for hydrogen production from COG resulting from the coking process in steelworks is evaluated, which is anticipated as a near-term hydrogen production for helping transition to a hydrogen energy economy in Taiwan.     

Comparative analysis of biomass and coal based co-gasification processes with and without CO2 capture for HT-PEMFCs

With the seasonal availability and low energy density of biomass and the high environmental impact of coal, the co-gasification of biomass and coal is an alternative approach facilitating a trade-off between renewable and non-renewable resources. The aim of this study was to investigate hydrogen production from the co-gasification of biomass and coal integrated by means of the sorption-enhanced water gas shift reactor (G-SEWGS) for a high temperature proton exchange membrane fuel cell (HT-PEMFC). The effects of the gasifier temperature, the steam to fuel ratio (S/F ratio), and the equivalence ratio (ER) on the hydrogen production performance and environmental impact of the G-SEWGS were theoretically analysed and compared with the conventional gasifier integrated with the water gas shift reactor (G-WGS) and the sorption-enhanced gasifier integrated with the water gas shift reactor (SEG-WGS). As compared to the conventional water gas shift reactor, the addition of a CaO sorbent in the modified water gas shift reactor not only reduces the amount of the CO₂ emission but also leads to an increase in the hydrogen concentration and hydrogen content. The G-SEWGS provides better performance in terms of its fuel processor efficiency and CO₂ emission than the G-WGS and the SEG-WGS. Also, the problem of sulphur compound in the hydrogen-rich gas can be reduced by using of the sorption-enhanced water gas shift reactor (SEWGS). The best system exergy efficiency, which was around 22% for the power generation, was determined from the HT-PEMFC integrated with the G-SEWGS. The main exergy destruction of around 70% of the total loss was caused by hydrogen production processes.     

Manufacturing gaseous products by pyrolysis of microalgal biomass

Algal biomass is considered as an alternative raw material for biofuel production. The search for new types of raw materials including high-energy types of microalgae remains relevant, since the share of motor fuels in the world energy balance remains consistently high (about 35%) with the oil price characterized by high volatility. The authors have considered the advantages of microalgae as raw materials for fuel production. Biochemical and thermochemical conversion are proposed as technologies for their processing. The paper presents the results of the study on the pyrolysis of the biomass of the blue-green microalgae/cyanobacterium Arthrospira platensis rsemsu 1/02-P clonal culture from the collection of the Research Laboratory of Renewable Energy Sources of the Lomonosov Moscow State University. The experimental investigation on the pyrolysis process of microalgal biomass has been carried out with the experimental setup made at the Institute of High Temperatures RAS in pure nitrogen 6.0 to create an oxygen-free medium with a linear heating rate of 10°С/min from room temperature to 1,000°С. The entire pyrolysis process has proceeded in the endothermic region. The specific values for solid residue, pyrolysis liquid and gaseous products have been experimentally determined. The following products have been manufactured by pyrolysis of microalgal biomass weighing 15 g: 1) char with a solid residue mass of 2.68 g, or 17.7% of MAB initial mass (while 9.3% of MAB initial mass has remained in the reactor); 2) pyrolysis liquid with a mass of 3.3 g, or 21.9% of initial mass; 3) noncondensable pyrolysis gases, 1.15 L. The specific volumetric gas yield (amount of gas released from 1 kg of RM) has amounted to 0.076 nm³/kg.In the paper, the analysis of the composition and specific volumetric yield of non-condensable pyrolysis gases produced in the pyrolysis process depending on temperature has been carried out. It is shown that the proportion of high-calorific components of the gas mixture (hydrogen, methane and carbon monoxide) increases with the temperature increase. The heating value assessment for the mixture of these gases has been performed as well.     

Thermodynamic analysis of a new process for hydrogen and electric power production by using carbonaceous fuels and high-temperature process heat

A new process for the simultaneous production of hydrogen and electrical power by using carbonaceous fuels and high-temperature process heat is presented in this paper. In an electrolytic cell, sulfur dioxide dissolved in an aqueous solution of sulfuric acid is electrochemically oxidized to sulfuric acid at the anode, while hydrogen gas is evolved at the cathode. The sulfuric acid produced in the cell provides the oxygen for the fuel combustion which subsequently takes place at high pressure. The combustion gas consisting mainly of CO₂, SO₂ and H₂O expands in a turbine in order to produce electrical power. After the expansion, the components sulfur dioxide and water are separated from the combustion gas and fed together with added water into the electrolysis cell.The process shows some advantages compared with already existing or proposed processes for the production of hydrogen or electric power. The influence of the sulfuric acid concentration and some other important process parameters on the energetic and exergetic efficiency of the total process is shown. The results shown in this paper have been obtained by using carbon (as a substitute for coal which is the preferred fuel) and a nuclear heat production plant (as an example of providing the required high-temperature process heat).     

Bio‐oil,solid and gaseous biofuels from biomass pyrolysis processes—An overview

As the global demand for energy rapidly increases and fossil fuels will be soon exhausted, bio‐energy has become one of the key options for shorter and medium term substitution for fossil fuels and the mitigation of greenhouse gas emissions. Biomass currently supplies 14% of the world's energy needs. Biomass pyrolysis has a long history and substantial future potential—driven by increased interest in renewable energy. This article presents the state‐of‐the‐art of biomass pyrolysis systems, which have been—or are expected to be—commercialized. Performance levels, technological status, market penetration of new technologies and the costs of modern forms of biomass energy are discussed. Advanced methods have been developed in the last two decades for the direct thermal conversion of biomass to liquid fuels, charcoals and various chemicals in higher yields than those obtained by traditional pyrolysis processes. The most important reactor configurations are fluidized beds, rotating cones, vacuum and ablative pyrolysis reactors. Fluidized beds and rotating cones are easier for scaling and possibly more cost effective. Slow pyrolysis is being used for the production of charcoal, which can also be gasified to obtain hydrogen‐rich gas. The short residence time pyrolysis of biomass (flash pyrolysis), at moderate temperatures, is being used to obtain a high yield of liquid products (up to 70% wt), particularly interesting as energetic vectors. Bio‐oil can substitute for fuel oil—or diesel fuel—in many static applications including boilers, furnaces, engines and turbines for electricity generation. While commercial biocrudes can easily substitute for heavy fuel oils, it is necessary to improve the quality in order to consider biocrudes as a replacement for light fuel oils. For transportation fuels, high severity chemical/catalytic processes are needed. An attractive future transportation fuel can be hydrogen, produced by steam reforming of the whole oil, or its carbohydrate‐derived fraction. Pyrolysis gas—containing significant amount of carbon dioxide, along with methane—might be used as a fuel for industrial combustion. Presently, heat applications are most economically competitive, followed by combined heat and power applications; electric applications are generally not competitive. Copyright © 2011 John Wiley & Sons, Ltd.