Recent insights into consolidated bioprocessing for lignocellulosic biohydrogen production

Biohydrogen production via dark fermentation using fermentable sugars from biomass materials is a sustainable way of procuring biohydrogen. Lignocellulosic biomass is a potential renewable feedstock for dark fermentation, but its use is challenged by the recalcitrant nature and generation of certain fermentation inhibitors resulting in compromised fermentation performance. Consolidated bioprocessing (CBP), the successful integration of hydrolysis and fermentation of lignocellulosic biomass to desirable products, has received tremendous research attentions in recent years to boost renewable fuel production in an economically feasible way. A microbial strain capable of both biomass hydrolysis and hydrogen fermentation is critical for successful CBP-based hydrogen fermentation. This review provides comprehensive information on dark fermentation for hydrogen production using lignocellulosic biomass as a potential feedstock with a CBP approach. Consolidated bioprocessing of lignocellulosic biomass for biohydrogen production via native and recombinant microbial strains is discussed in detail. Potential bottlenecks in the above mentioned processes are critically analyzed and future research perspectives are presented.     

Biomass-based energy fuel through biochemical routes: A review

Energy demand is increasing continuously due to rapid growth in population and industrialization development. The development of energy sources is not keeping pace with spiraling consumption. Even developed countries are not able to compensate even after increasing the energy production multifold. The major energy demand is provided from the conventional energy sources such as coal, oil, natural gas, etc. Two major problems, which every country is facing with these conventional fuels, are depletion of fossil fuels and deterioration of environment.The present review article aims to highlight various biochemical processes for conversion of biomass into biological hydrogen gas and ethanol. The present discussion focuses on hydrogen production through various routes viz. fermentative, photosynthesis and biological water gas shift reaction. In addition, emphasis has been laid on ethanol as biomass-based energy fuel. The discussion has been focused on the technology for ethanol production from various biomass sources such as molasses, lignocellulosic feedstock and starch. Various biochemical processes and their major steps involved during the ethanol production from biomass have been discussed in detail.     

Methane production from lignocellulosic agricultural crop wastes: A review in context to second generation of biofuel production

The aim of this paper is to present a comprehensive review on renewable methane fuel production through the biological route of biomethanation process from major lignocellulosic agricultural crop waste biomass (maize, wheat, rice and sugarcane). Global annual approximate production of major agriculture based lignocellulosic biomass has been explored. Fundamental requirements of biomethanation process have been discussed in details for optimum production of methane. The essential properties of biomass (proximate, ultimate and compositional) conscientious for quality of derived fuel have also been presented along with the pretreatment requirements for lignocellulosic biomass. Methane generation potential of the major lignocellulosic agricultural crop biomass has been explored and presented. Furthermore, the methane production potential and its energetic analysis have also been compared with the bio-ethanol productions. The overall parametric analysis involved in anaerobic digestion and alcoholic fermentation explore that methane generation from lignocellulosic agricultural crop waste biomass is more economical and environmentally beneficial way of biomass utilization in a sustainable way of energy production.     

Characteristics of hydrogen production from steam gasification of plant-originated lignocellulosic biomass and its prospects in Vietnam

Demands for the decline of CO₂ emissions resulted in a significant transformation of the energy systems working on carbon sources towards more sustainable, clean, and renewable characteristics. Hydrogen is emerging as a secondary energy vector with ever-increasing importance in the decarbonisation progress. Indeed, hydrogen, a green and renewable energy source, could be produced from steam gasification of plant-originated lignocellulosic biomass. In this current review, key factors affect the hydrogen production yield from steam gasification of plant-originated lignocellulosic biomass, including the design of the gasifier, temperature, pressure, and steam-to-biomass ratio, steam flow rate, moisture and particle size of fed biomass, and catalysts were thoroughly analysed. Moreover, the effects of the abovementioned factors on the reduction of tar formation, which is also a key parameter towards ensuring the trouble-free operation of the reactor, were critically evaluated. More importantly, the separation of produced hydrogen from steam gasification of biomass and challenges over technological, environmental, and economic aspects of biomass gasification were also presented in detail. In addition, this paper is also profiling the prospect of Vietnam in fulfilling its hydrogen economy potential because Vietnam has vast biomass due to its tropical weather and availability of arable land, providing abundant lignocellulosic biomass with 45% of agricultural waste, 30% of firewood, and 25% of other sources. Besides, some primary factors hindering the broad application of biomass for hydrogen production were indicated. Finally, some solutions for implementing the hydrogenization strategy in Vietnam have also been discussed.     

An overview on cell and enzyme immobilization for enhanced biohydrogen production from lignocellulosic biomass

Hydrogen gas, a carbon-free energy carrier, can be produced via fossil fuel reforming, coal gasification, water electrolysis, photocatalysis, or biological process. Biohydrogen production from lignocellulosic biomass (LCB) in this regard, appears as an environmental benign, sustainable, non-food competing second generation fuel. LCB serves as the largest potential carbon source for sustainable biohydrogen production with an enormous global annual capacity of more than one trillion tons. Enzymes in this case, are widely used to hydrolyse the LCB into fermentable sugars, and subsequent hydrogen production is carried out by dark fermentation. However, the untapped non-food competing LCB is currently impeded by several critical bottlenecks including sensitivity of cells and enzymes to numerous denaturing conditions, recyclability, and high cost of enzyme. Low productivity of hydrolysis and hydrogen production in this regard, lead to a larger bioreactor and capital expenditures (CAPEX) requirement, which in turn, making this approach to be less competitive in commercial application. These bottlenecks can be overcome by immobilization technique, which enables the recyclability, improves stability and productivity of the enzyme and cells. Current review accommodates for the important outlook and critical insights into the immobilization techniques, providing important guidelines for the operation of immobilization techniques to elevate commercial competitiveness of biohydrogen production from LCB in the future. The effect of geometry, surface charges, and wettability of different type of carriers for cell immobilization to enhance biohydrogen production are discussed. The critical aspects of the immobilization parameters, such as temperature, pH, and duration which could significantly affect the properties of immobilized enzymes are thoroughly examined in this review. Suggestions and future directions of this field are provided to assist the development of an efficient, economic, and sustainable hydrogen production process.     

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.     

Comparison of co–gasification efficiencies of coal,lignocellulosic biomass and biomass hydrolysate for high yield hydrogen production

The diversity in the chemical composition of lignocellulosic feedstocks can affect the conversion technologies employed for hydrogen production. Gasification and co–gasification activities of lignocellulosic biomass, biomass hydrolysate, and coal were evaluated for hydrogen rich gas production. The hydrolysates of biomass materials showed the best performance for gasification. The results indicated that biomass hydrolysates obtained from lignocellulosic biomass were more sensitive to degradation and therefore, produced more hydrogen and gaseous products than that of lignocellulosic biomass. The effects of feed (kenaf and sorghum hydrolysate), flow rate (0.3–2.0 mL/min) and temperature (700–900 °C) on hydrogen production and gasification yields were investigated. It was observed that 0.5 mL/min the optimum feed flow rate for the maximum total gas and hydrogen production. Synergism effects were observed for co–gasification of coal/biomass and coal/biomass hydrolysate. In all co–gasification processes, the main component of the gas mixture was hydrogen (≥70%).     

Constructing a new business model for fermentative hydrogen production from wastewater treatment

The development of hydrogen energy as a sustainable energy resource is essential for mitigating climate change. The primary challenge to the commercialization of hydrogen energy, relative to that of petrochemical fuels, is cost. Therefore, an innovative business model that converts the costs of procuring biomass into revenue via the production of hydrogen was developed. Profitable hydrogen production can typically be realized by lowering costs through continuous technological development and increasing scale. Feedstock procurement costs, however, limit the cost/benefit reduction flexibility. This study employs biowaste material as feedstock for biological fermentative hydrogen production. This model extends the hydrogen production value chain to include the income from biomass hydrogen production as well as the revenue from processing biowaste and reduced fuel source costs. This study investigates the costs involved in the commercialization of the hydrogen fermentation process, develops an innovative business model, and presents a case study to describe this model.     

Review on fermentative biohydrogen production from water hyacinth,wheat straw and rice straw with focus on recent perspectives

Hydrogen (H₂) is often considered as the best option to store energy coming from renewable sources. Hydrogen production from lignocellulosic biomass via fermentation offers low cost and environmental friendly method in terms of energy balance and provides a sustainable pathway for utilization of huge amount of unused biomass. In this regard, special attention on potential of different lignocellulosic biomass is required. In this paper, the fermentative hydrogen production from three carbohydrates-rich biomass: water hyacinth, wheat straw and rice straw is comprehensively reviewed. In other point of view, usage of H₂ has a 10% growth annually that will reach to 8–10% of total energy in 2025. Furthermore, research on recent trends of fermentative hydrogen production is crucial and vital. However, the majority of the published researches in the last decade confirmed that some challenges exists which are the process optimization, effecting parameters and commercialization aspects.     

Biohydrogen production: An outlook on methods,constraints, economic analysis and future prospect

Utilization of hydrogen as fuel lights into various technological, economic and ecological challenges. High production cost and low yield are main drawbacks of commercial hydrogen production methods. Hydrogen production by biological methods helps to overcome these issues owing to its merit such as cost-effective, non-pollutant, recyclability and efficiency in energy conversion. Research has been conducted in utilizing cyanobacteria and algal species for producing biohydrogen utilizing solar light and other sources. Developments have been made for improving biohydrogen productivity through genetic and metabolic engineering. This review outlines the importance of biohydrogen and the constraints in producing biohydrogen in detail. Biohydrogen production can be facilitated using photolysis, fermentation and electrochemical processes. Bioreactors can be used effectively with specific designs and configuration for increasing productivity. The challenges faced during biological production and methods to overcome those demerits are also included for bringing the uncharted principles for producing biohydrogen in an efficient method.     

Feedstock analysis sensitivity for estimating ethanol production potential in switchgrass and energycane biomass

Efficient ethanol production from lignocellulosic biomass requires highly degradable feedstock; therefore, there is a similarity between forage crop production for ruminant animals and ethanol production from lignocellulosic biomass. Feed value analysis techniques may be used to estimate lignocellulosic biomass quality. Because lignin and its derivatives in cell walls are major compounds interrupting biomass degradation, fiber analysis and in vitro incubation tests were conducted with switchgrass (Panicum virgatum) and energycane (Saccharum spp.) biomass collected at 100 and 120 g lignin (acid detergent lignin) kg^?1 DM (dry matter). Mean NDF (neutral detergent fiber) in switchgrass was consistently greater than that of energy cane regardless of lignin levels, while ADF (acid detergent fiber) did not differ. Mean of energycane in vitro true digestibility and digestible neutral detergent fiber were greater than those of switchgrass. The ADF and ruminal fermentation rate averaged by lignin levels differed, while most of the analysis results did not. Based on ADF and NDF concentrations, switchgrass contained a greater concentration of hemicellulose than energycane, while cellulose concentration was similar. Fermentability of energycane was consistently greater than that of switchgrass. Fermentation gas volume was positively correlated with cellulosic biomass degradation for ethanol production. Consequently, fermentation gas kinetic parameters obtained from biomass fermentation with rumen fluid or with yeast indicate that the fermentable pool size is the parameter most closely correlated to ethanol production potential across the species. Results obtained from feed value analyses demonstrate fermentation variability and meaningful relationships between fermentation gas parameters and ethanol production. Thus, the ruminal fermentation process is useful as a screening tool for ethanol production potential of biofuel feedstock. Copyright © 2015 John Wiley & Sons, Ltd.     

Hydrogen production from simultaneous saccharification and fermentation of lignocellulosic materials in a dual-chamber microbial electrolysis cell

In this work, a dual-chamber microbial electrolysis cell (MEC) with concentric cylinders was fabricated to investigate hydrogen production of three different lignocellulosic materials via simultaneous saccharification and fermentation (SSF). The maximal hydrogen production rate (HPR) was 2.46 mmol/L/D with an energy recovery efficiency of 215.33 % and a total energy conversion efficiency of 11.29 %, and the maximal hydrogen volumetric yield was 28.67 L/kg from the mixed substrate. The concentrations of reducing sugar and organic acids, the pH, and the current in the MEC system during hydrogen production were monitored. The concentrations of reducing sugar, butyrate, lactate, formate, and acetate initially increased during SSF and then decreased due to hydrogen production. Moreover, the highest current was obtained from the mixed substrate, which means that the mixed substrates are beneficial to microbial growth and metabolism. These results suggest that lignocellulosic materials can be used as substrate in a low-energy-input dual-chamber MEC system for hydrogen production.     

Starch: a potential substrate for biohydrogen production

Hydrogen is a clean energy carrier with great potential to be an alternative fuel. Anaerobic hydrogen fermentation seems to be more favorable, since hydrogen is yielded at high rates and various organic waste and wastewater enriched with carbohydrates as substrate result in low cost for hydrogen production. Abundant biomass from various industries could be a source for biohydrogen production where combination of waste treatment and energy production would be an advantage. Carbohydrate‐rich nitrogen‐deficient solid wastes such as starch residues can be used for hydrogen production by using suitable bioprocess technologies. Alternatively, converting biomass into gaseous fuels, such as biohydrogen, is possibly the most efficient way to use these agroindustrial residues. This review summarizes the potential of starch agroindustrial residues as a substrate for biohydrogen production. Types of potential starch agroindustrial residues, recent developments and bio‐processing conditions for biohydrogen production will be discussed. Copyright © 2014 John Wiley & Sons, Ltd.     

A state of the art review on biomass processing and conversion technologies to produce hydrogen and its recovery via membrane separation

Hydrogen is a zero-emission green fuel containing sufficient energy potentially suitable for electricity generation. Currently, large quantities of hydrogen are produced using classical fossil fuels. Nevertheless, the finite quantities of these resources have compelled the global community to look into using more sustainable and environmentally friendly resources such as bio-based waste. There are several approaches, to convert biomass to hydrogen, among which the thermochemical and biological processes are considered as the most important ones. The aim of this review paper is twofold, namely, (a) to evaluate hydrogen production and biomass processing methods to give a better insight into their potential merits and identify gaps for sustainable hydrogen generation, and (b) to evaluate current and future opportunities in membrane technology for hydrogen separation and purification from biomass processing. By fulfilling these gaps, the objectives of economical, sustainable, and environmentally-friendly resources for hydrogen production and separation can be recommended.     

Enhanced bio-hydrogen production from cornstalk hydrolysate pretreated by alkaline-enzymolysis with orthogonal design method

Bio-hydrogen (H₂) production from renewable biomass has been accepted as a promising method to produce an alternative fuel for the future. In this study, fermentative hydrogen production from cornstalk (CS) hydrolysate pretreated by alkaline-enzymolysis method was investigated. Meanwhile, a five-factor and five-level orthogonal experimental array was designed to study the influences of Ca(OH)₂ concentration, alkaline hydrolysis time, alkaline hydrolysis temperature, cellulase and xylanase dosages on cornstalk pretreatment and hydrogen production. A maximum reducing sugar yield of 0.59 g/g-CS was obtained at Ca(OH)₂ 0.5%, hydrolysis temperature 115 °C, hydrolysis time 1.5 h, cellulase dosage 4000 U/g-CS and xylanase 4000 U/g-CS. Under this same condition, the maximum hydrogen yields of 168.9 mL/g-CS, 357.6 mL/g-CS, and 424.3 mL/g-CS were obtained at dark-fermentation, photo-fermentation, and two-stage fermentation respectively. It's also found that the significance of these five parameters on H₂ production followed from high to low order as: Ca(OH)₂ concentration, cellulase dosage, xylanase dosage, hydrolysis time, and hydrolysis temperature. By comparing the energy produced with the energy spent, the maximum Energy Sustainability Index (ESI) value of 1.11 was obtained at the two-stage fermentation. The results suggested that two-stage fermentation is a promising and efficient way for hydrogen production from lignocellulosic biomass.     

Optimized model of fermentable sugar production from Napier grass for biohydrogen generation via dark fermentation

Biohydrogen is a fossil-fuel alternative. Lignocellulosic biomass is a complex part of cellulose-to-simple sugar production. Napier grass, one of the lignocellulosic biomasses, is best for biofuels or biochemicals. The dark fermentation process of Napier grass for biohydrogen proved both cost-effective and environmentally friendly. This grass contains cellulose, hemicellulose and lignin were 35.44 ± 2.01, 20.05 ± 1.55, and 28.473 ± 1.34, respectively. Sodium hydroxide was used in different concentrations to delignify lignocellulose and improve grass glucose recovery. Fermentative hydrogen production from grass biomass processing by microflora was optimized in terms of pH (4.5–7.0) and mesophilic condition (35 ± 2 °C). In this study, mesophilic conditions favored maximum hydrogen production (763.34 ml), indicating that pH 5.5 was suitable for dark-fermentative hydrogen production; study results showed Napier grass could be used successfully for dark fermentation to produce biohydrogen.     

Progress in bioethanol processing

Production of ethanol (bioethanol) from biomass is one way to reduce both consumption of crude oil and environmental pollution. Bioethanol is appropriate for the mixed fuel in the gasoline engine because of its high octane number, and its low cetane number and high heat of vaporization impede self-ignition in the diesel engine. So, ignition improver, glow-plug, surface ignition, and pilot injection are applied to promote self-ignition by using diesel-bioethanol-blended fuel. Disadvantages of bioethanol include its lower energy density than gasoline, its corrosiveness, low flame luminosity, lower vapor pressure (making cold starts difficult), miscibility with water, and toxicity to ecosystems. Bioethanol can be produced from cellulosic feedstocks. One major problem with bioethanol production is the availability of raw materials for the production. The availability of feedstocks for bioethanol can vary considerably from season to season and depends on geographic locations. Lignocellulosic biomass is the most promising feedstock considering its great availability and low cost, but the large-scale commercial production of fuel bioethanol from lignocellulosic materials has still not been implemented. Conversion technologies for producing bioethanol from cellulosic biomass resources such as forest materials, agricultural residues and urban wastes are under development and have not yet been demonstrated commercially. For designing fuel bioethanol production processes, assessment of utilization of different feedstocks (i.e. sucrose containing, starchy materials, lignocellulosic biomass) is required considering the big share of raw materials in bioethanol costs. In this work a review of the biological and thermochemical methods that could be used to produce bioethanol is made and an analysis of its global production trends is carried out.     

Pretreatment of lignocellulosic biomass for enhanced biogas production

Lignocellulosic biomass is an abundant organic material that can be used for sustainable production of bioenergy and biofuels such as biogas (about 50–75% CH₄ and 25–50% CO₂). Out of all bioconversion technologies for biofuel and bioenergy production, anaerobic digestion (AD) is a most cost-effective bioconversion technology that has been implemented worldwide for commercial production of electricity, heat, and compressed natural gas (CNG) from organic materials. However, the utilization of lignocellulosic biomass for biogas production via anaerobic digestion has not been widely adopted because the complicated structure of the plant cell wall makes it resistant to microbial attack. Pretreatment of recalcitrant lignocellulosic biomass is essential to achieve high biogas yield in the AD process. A number of different pretreatment techniques involving physical, chemical, and biological approaches have been investigated over the past few decades, but there is no report that systematically compares the performance of these pretreatment methods for application on lignocellulosic biomass for biogas production. This paper reviews the methods that have been studied for pretreatment of lignocellulosic biomass for conversion to biogas. It describes the AD process, structural and compositional properties of lignocellulosic biomass, and various pretreatment techniques, including the pretreatment process, parameters, performance, and advantages vs. drawbacks. This paper concludes with the current status and future research perspectives of pretreatment.     

木质纤维素生物质生产乙醇的预处理技术

木质纤维素生物质经过预处理后，原料的内孔面积增大，纤维素的结晶性降低，并且半纤维素和木质素被去除．预处理后的生物质容易进行酶水解生产燃料乙醇。总结了近些年来的预处理技术，如物理法、化学法和生物法。     

生物质热化学转化制氢技术

生物质是一种重要的可再生能源，是氢的载体，与矿物燃料相比，具有挥发分高，硫、氮含量低等优点。无论是从能源角度还是从环境角度，发展生物质制氢技术都具有重要的意义。目前有关生物质制氢方面的研究主要集中在热化学转换法和生物法，文章从热化学转换的角度，进行了几种生物质制氢路线的技术经济分析预测。