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The multifaceted hydrolytic enzyme xylanase has been found to play a pivotal role in the energy and green technology sectors. Extensive research is being carried out with the aim to produce xylanases that would fulfill industrial parameters, in the paper and pulp and fuel industries. Cellulase-free xylanase with good thermal stability finds promising use for biobleaching in paper manufacturing. In current scenario, it has been found that renewable energy is a burgeoning area, where xylanase finds a major role. Xylanase is synergistically involved with other cooperating enzymes for the deconstruction of lignocellulosic raw material, which ultimately paves way for the production of fuel ethanol. In other words, efficient utilization of lignocellulosic raw materials will positively boost the economics of alternate fuel industry.

This study presents a mathematical model that aids the design and management of a biofuel supply chain network based on the treatment of wastewater sludge generated at Pulp and Paper plants. The model presented here analyzes the supply chain performance under different biomass conversion processes, different requirements for plant location and capacities. We present a case study using data from the states of Alabama, Louisiana and Mississippi. The modes of transportation considered in this analysis are truck, rail and barge. The model identifies the location of biocrude plants, the amounts of glycerol and wood chip to purchase, the amounts of products to deliver, the amount of biodiesel to produce, the modes of transportation and the suppliers to use in order to minimize the system wide cost. Numerical analysis identifies Lincoln, Mississippi and Naheola, Alabama as two potential locations for biocrude plants.

Fossil fuel depletion and pollution are calling for alternative, renewable energies such as biofuels. Actual challenges include the design of efficient processes and catalysts to convert various feedstocks into biofuels. Here, we review nanoferrites heterogeneous catalysts to produce biodiesel from soybean and canola oil. For that, transesterification is the main synthesis route and offers simplicity, cost-effectiveness, better process control, and high conversion yield. Catalysis with nanoferrites and composites allow to obtain yields higher than 95% conversion with less than 5.0 wt.% of catalyst loading at 80 °C in 1–2 h. More than 90% conversion yields can be achieved with a moderate alcohol/oil molar ratio, i.e., between 12:1 to 16:1. Catalyst recovery is easy due to the magnetic properties of nanoferrite, which can be effectively reused up to 4 times with less than 10% loss of catalytic efficiency.

Lignin is a complex biological molecule and well known as a second abundant biopolymer on the planet. It also produced as a by-product of lignocellulosic biomass, paper and pulp industry. It has not been well explored for industrial applications due to its poor solubility and complex molecular structure. Hence, since last two decades, lignin has gained the attention of researchers as a raw material for the synthesis of value-added products of commercial importance. However, the major part of the lignin derived from the pulp industry is being utilized as boiler fuel. The efficacy of lignin produced from lignocellulosic-based bio-ethanol industry to synthesize the renewable polymeric material is much higher as compared to the lignin obtained from pulp industry. These days lignin has also been exploited to synthesize various chemicals like esters, ethers, bio-adhesives, biolubricants, foams, nano-particles and nano-composites. The excessive production of lignin from paper or bio-ethanol industry has also appeared as critical environmental problem. The conversion of huge amount of lignin will not only help to solve the environmental threat but also boost the bio-economy of bio-ethanol and paper industry. In this chapter, we highlight the sources, extraction of lignin and its immense industrial importance.

Renewable sources of energy and chemicals are a viable solution in current situation where world is facing extreme energy crisis. Achieving carbon neutral options for energy supply and high productive options for bulk chemicals by renewable source. Microalgal Biomass is a promising option and has the potential to provide renewable energy and products for future grown in minimum inputs and gives higher output. In this review paper three cultivation techniques are discussed such as autotrophic, heterotrophic, and mixotrophic. Mixotrophic cultivation involves combination of both auto and heterotrophic modes where both light reaction and dark reaction are combined for maximum results. Cost effective options of bioenergy and valuable co products are efficiently produced from microalgae in mixotrophic cultivation conditions. Bioprospection of microalgal options for bioenergy and cultivating those strains in mixotrophic conditions combining with wastewater treatment and CO2 fixation from atmosphere to produce biofuel and valuable co products in the main theme of this review. Concept of biorefinery is prescribed for future options.

High cultivation cost and low lipid yield are framed as a major bottleneck for the production of microalgae biodiesel. Hence, we first and foremost highlight a trophic mode transition, coupled with a combinatorial effect of organic carbon, nitrogen and light (C/N/L) on an isolated microalga Chlorococcum sp. SVF in a one pot tri-phasic intermittent feeding system by developing a lab scale Raceway tank (40L). Hitherto, waste molasses syrup without hydrolysis is unexplored in algal bioenergy arena. The direct utilisation capability of sucrose, served by waste unhydrolysed molasses syrup (WUMS), effectively modulates the intrinsic biochemical and physiological characteristics towards microalgae biomass and lipid assimilation. Response surface methodology—central composite design (RSM-CCD) tool has been employed to observe the cumulative impact of light irradiation and nutrient sources (carbon and nitrogen) on cellular stoichiometric analysis. Experimental results exhibit a potentially achievable biomass (18.88 g L(−1)) and lipid accumulation (80.34%) under the light intensity of 75.5 µmol m(−2) s(−1) with stepwise light attenuation strategy. Characterisation of fatty acid methyl esters (FAME) reveals the dominance of oleic acid (32.72%) and palmitic acid methyl esters (32.49%) in mixotrophic condition, which are considered as the upmost indicators of quality biodiesel. The biofuel properties were obtained in acquiescence with American and European standard. These findings are therefore a way forward towards the effective growth of Chlorococcum sp. SVF in sucrose rich inexpensive industrial waste stream that positively influences the lipid yield for large scale sustainable biodiesel production. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s13205-021-02823-7.

Cellulase is the largest group of industrial enzyme used worldwide for the degradation of cellulose. Since many industries use this enzyme for the production of good quality of products, hence the demand for cellulase is increasing day by day. Cellulases are preferred for different purposes by industries which include paper recycling, cotton, textile, juice extraction, food, etc. Cellulases have some major enzymatic group components such as endoglucanases, exoglucanase and β-glycosidase. Different technologies are used for the production of cellulases, i.e. shake-flask experiments to fermentations, construction of improved cellulases, batch cellulase production and fed-batch cellulase production. Each method has its own limitations; considering these limitations, recombinant technology may play a valuable function in increasing the cellulase production. In present scenario, different industries are using the recombinant technology for the enhancement of cellulase production. The recombinant technology can help to produce cellulase more effectively than the other technologies which convert cellulosic biomass to glucose and other products. In nature, microorganism has the potential to produce cellulases, which enable the function of hydrolysing cellulose. However, recent reports claim that the plants, several molluscs such as snails, a periwinkle, Nudibranchia and a few bivalves also have the ability to yield cellulases. In this chapter, we have concluded how recombinant technology can help to manage the crisis of cellulases for various objectives and also improving the availability of biofuel.

Sabkhas are home to many xero-halophytes that could be considered renewable resources for various fiber industries. Lignocellulosic fibers of these plants are proposed as raw material for bioenergy production. Nowadays, ethanol is the major biofuel in use. In this paper, fiber composition of 21 xero-halophytic species from Tunisian sabkhas was evaluated using Ankom 200 Fiber Analyzer and compared with that obtained by other studies. The lignocellulosic biomass of xero-halophytes can be considered as an attractive raw material for the future application for the production of bioethanol, paper of good quality, and reinforcement polymers. Two perennial species are considered an important source of bioethanol production which are Sarcocornia fruticosa and Aristida pungens. Suaeda fruticosa from Tunisia can be used in the production of high-quality lightweight paper.

Better living standards, population growth, and expanding urbanization escalate the energy requirement tremendously. Declining stockpile of nonrenewable fossil fuels and its severe impact on environment have created huge consciousness among government, researchers, and industries to develop alternative renewable energy sources. Bioethanol has been considered as one of the most efficient alternative liquid fuels to replace the existing conventional crude oil-based petrol. Among the different lignocellulosic biomass, agricultural residues especially sugarcane tops (SCT) are becoming a promising feedstock for bioethanol production. However, the presence of high amount of lignin possesses a major hurdle in converting this promising feedstock to bioethanol. Hence, this review paper summarizes the various pretreatment methods, hydrolysis, and fermentation techniques reported in the bioethanol production from underutilized SCT. From the overall studies, it was evident that the SCT can be used as a potential renewable feedstock for the production of fermentable sugars and bioethanol.

Oxidative pretreatment of lignocellulosic biomass improves the efficacy of plant cell wall polysaccharides in biochemical conversion processes. In presence of oxidants, recalcitrant lignins are oxidized and dissolved to enhance the access of cellulose and hemicellulose to pretreatment chemicals and hydrolytic enzymes. This chapter focuses on the common types of oxidative pretreatments, their applications in biomass conversion, and the physiochemical changes in biomass structure during the pretreatment.

To date, much attention has been paid on developing new strategies for the valorization of abundant, inexpensive, and renewable lignocellulosic biomass into liquid biofuels and chemicals. Lipids are one kind of value-added energy-rich compounds, which can produce by oleaginous microorganisms using biomass and/or biomass-hydrolysates. Recently, the conversion of lignocellulosic biomass into microbial lipid has received significant attention replacing fossil fuels. However, biomass is highly recalcitrant due to its complex structure with cellulose, hemicellulose, and lignin. Pretreatment of biomass is a critical process in the conversion due to the nature and structure of the biomass cell wall that is complex. Although green technologies for microbial production are advancing, the productivity and yield from these techniques are low. Over the past years, various biomass pretreatment techniques have been developed to disrupt the plant cell-wall structure of lignocellulosic biomass, facilitate subsequent enzymatic hydrolysis and microbial lipid fermentation, and successfully employed to improve biomass-to-lipid technology. In this chapter, the progress of pretreatment for enhancing the enzymatic digestion of lignocellulosic material is introduced. In addition, microbial lipid production from lignocellulosic biomass pretreated by effective pretreatment is discussed.

This study aims to produce renewable biofuels (bio-oil, syngas) and nutrient-rich biofertilizers (pyrochar or biochar) from Municipal Sewage Sludge (MSS) via the innovative pyrolyis process. The pre-dried MSS was analyzed using proximate and ultimate analyses, FTIR spectroscopy, and DTA-TGA thermogravimetry to evaluate their suitability as a feedstock for thermochemical conversion and biofuels production. The optimization of the pyrolysis reactions was performed using a laboratory-scale fixed-bed reactor and the investigation of the influence of some key operational parameters (final temperature and heating rate) on the pyrolysis products distribution shows that 600 °C and 10 °C/min are the optimal conditions to obtain a maximum bio-oil yield (44.31 wt.%). The characterization of the obtained pyrolysis products indicates (i) a high aliphatic character of the bio-oil, with the occurrence of several organic compounds (n-alkanes, n-alkenes, carboxylic acids and aromatic compounds); (ii) good fuel properties of the pyrolytic oil comparable to those of fossil fuels, promoting its application as liquid biofuel; (iii) a high calorific value of the obtained syngas (HHV around 16.68 MJ/m3) encouraging its use as a source of renewable energy or for pyrolysis reactor heating (iv) a highly porous biochar with good carbon and nitrogen contents which could be investigated as a biofertilizer.

Agricultural industries produce a significant amount of lignocellulosic materials and wastes that can be converted and developed into cost-effective energy and value-added bioproducts of commercial importance. Bioconversion turns organic matter into products using biological methods or agents. Straw biomass is an important agricultural residue that can be harnessed for the production of bioethanol, high-value biochemicals, special enzymes, organic products, proteins, and biomaterials. The tough lignin layer of the lignocellulosic components necessitates the pretreatment steps including the physico-mechanical, chemical, or biological methods to allow further processes such as saccharification, fermentation, and anaerobic digestion; and to enhance accessibility to the microbes and enzymes, for bioconversion into products of interest. However, there are major economic and technological challenges that have to be taken into consideration. This chapter highlights the straw biomass and its key composition for the bioconversion into valuable bioproducts. Different biological pretreatments using lignocellulolytic enzymes for the degradation of biomass are elaborated. The challenges for industrial-scale implementation to develop bio-based commercial production using straw biomass are also addressed.

Decarbonisation is at the core of energy and climate policy in the European Union. The European Green Deal reasserts the European Commission´s commitment to tackling climate and environmental challenges to reach a carbon-neutral society by 2050. Biomass is part of our low-carbon future. The use of biomass from pruning fruit trees to obtain biofuel pellets can be an interesting alternative in Southern Europe, generating added value in rural areas and favoring the development of the circular economy and green economy. Sustainable use of biomass replaces fossil fuels. Size fractionation and washing proceed to demineralization of the plum wood residues with high efficiencies. These biomass pretreatments reduce the ash content in the wood biomass with bark or debarked in water treatment and increase and reduce the ash content in different size fractions. The ash content has been studied in different treatments for plum biomass (with bark, without bark and fractionated at 3.15 and 8 mm). In turn, a washing treatment was carried out at room temperature with different times (5, 30, 60 and 180 min), together with a washing at a temperature of 45 oC for the 8 mm fractionation.

Using lignin to produce high-value-added aromatic fine chemicals and high-grade biofuels such as aromatics, cycloalkanes, and alkanes can reduce the dependence on fossil resources and highly improve the competitiveness of biorefining industry. The biological valorization of lignin includes the biological depolymerization and bioconversion of lignin. With the development of bioprospecting and systems biology technology, more and more lignin-degrading microorganisms have been discovered and separated from the natural habitat of lignin decomposition. The physiological and biochemical characteristics of microorganisms and the molecular- and systematic-level degradation mechanism on lignin and lignin-derived aromatic compounds have also been deeply recognized. All of these have laid a theoretical foundation for precisely controlling the depolymerization and metabolism of lignin and establishing the biological processing pathway of lignin. This chapter will introduce the research progress of lignin valorization from the aspects of lignin-degrading microorganisms and enzymes, lignin degradation metabolic pathways, and the application of biosynthesis in lignin conversion.

Most of dry debarking waste in Siberia is formed from larch, the processing of which is difficult due to high humidity, polydispersity, low-mechanical strength. In this research work, briquettes have been obtained in a single-seated mold from large-tonnage waste dry debarked larch on the GSM-50 laboratory press without the use of binders and elevated temperatures. Briquettes have been pyrolyzed in a laboratory retort at a temperature of 500 °C, their internal structure and mechanical strength have been studied depending on the fractional composition and molding pressure. It has been revealed that small particles of dry debarking waste contained in the mixture of fractions have little effect on the mechanical strength of the briquettes; the coals obtained from briquettes under a pressing pressure of 100 MPa are not inferior in mechanical strength to charcoals from stem wood. The characteristics of briquettes and coals obtained from the dry debarks of Siberian larch are fit to be used as biofuels in domestic and industrial fuel plants, for heating residential and industrial buildings, for gas-generating plants that produce gases used in internal combustion engines, as well as for production electricity at a mini-CHP.

Lignocellulosic (LC) feedstock is the most economical and renewable natural feedstock of chemicals and energy. It is primarily composed of lignin, cellulose, and hemicellulose which are woven together and render the biomass recalcitrant to degradation. Hemicellulose is the second largest component of this biomass that is degraded to obtain large quantities of xylose. The effective utilization of the xylose is one of the most significant pre-requirement for economical bioconversion of LC biomass into biochemicals and biofuels. However, there are still some bottlenecks in the bioconversion of xylose, due to limitations to exploit xylose metabolism pathways. To overcome these issues, various research works have been carried out to engineer the transporters and enzymes involved in xylose utilization. Successful progress in this regard will boost xylose yield and titer, leading to the economical bioprocessing of the LC biomass. In order to understand biomass transformation strategies, firstly structural composition of LC biomass is introduced that is followed by the discussion on the chemical and enzymatic hydrolysis of biomass. Moreover, the importance of pretreatment as a prerequisite operation to biomass saccharification has also been highlighted along with an overview on various pretreatment methods. Finally, the significance of xylose as a raw material, its efficient utilization and the challenges concerning co-fermentation of sugars for the production of biofuels and other value-added chemicals by yeasts have been discussed.

Biomass utilization originating from inedible farming and forest waste, as a renewable feedstock for liquid biofuels and viable products, will have important environmental and social impacts in the future. Lignocellulose, the main nonedible component of biomass, is a primordial element abundantly rich in cellulosic compounds and lignins. The conversion of cellulose and hemicellulose to biofuels and valuable platform chemicals (such as levulinic acid, formic acid, furfural, γ-valerolactone and other derivatives) has long been studied, and great progress has been made in their industrial production. Lignin being a unique raw material has gained enormous attention in the recent years being an important source for sustainable and viable products. The successful conversion of lignin into value-added chemicals involves three main processes: (1) decomposition of lignocellulose, (2) depolymerization (3) upgradation to the desirable chemicals. The choice of catalyst in either homo- or heterogeneous systems is crucial for the effective depolymerization of lignin and upgrading to desirable chemicals. Hydro-processing (hydrogenolysis, hydrogenation, hydrodeoxygenation and hydro-demethoxylation) is a highly preferred, practical method for the depolymerization leading to production of valuable products and drugs. These reactions generally occur over metals, namely, platinum, palladium, ruthenium and nickel. This chapter aims to present a holistic analysis of the role of Group VIII metals in conversion of lignin and lignin-based aromatic monomers. This simplified summary will be useful to researchers for developing heterogeneous catalyst towards effective production of industrially sound products.

Cultivation of microalgae biomass for bioethanol production appeared as one of the potential solution to drive green and sustainable fuel production. Microalgae are photosynthetic microorganism that can grow rapidly compared to the terrestrial plants and able to accumulate high content of carbohydrate within their cells. The carbohydrate is usually stored in the form of starch, which is easier to breakdown to simple reducing sugar than lignocellulosic biomass. In the present chapter, the process route to produce bioethanol from microalgae biomass is discussed, including the cultivation strategies to enhance microalgae carbohydrate productivity, biomass pre-treatment methods, hydrolysis and fermentation process.

Renewable energy, especially biofuels, has the potential to supplement a part of the existing fossil-based transportation fuels. Biofuels such as bioethanol can be produced from established glucose fermentation processes; however, cheap and efficient glucose production is a hindering factor. Cellulose, the world’s most abundant organic material, is a polymer of glucose and is locked within the lignocellulosic framework of plants. Pre-treatment is required to facilitate effective cellulose saccharification. Semiconductor photocatalysis, an advanced oxidation process, is a potential method for cellulose breakdown and the focus of this chapter will be on harnessing photocatalysis for cellulose-based renewable energy production.

Ethanol production from sustainable and inexpensive farming residues decreases greenhouse gas emissions, for instance, carbon dioxide, nitrogen dioxide, sulfur oxide, and eliminate smog from the atmosphere. A certain number of agricultural residues and plentifully misused materials are oat straw, rice straw, and wheat straw; waste potato, switchgrass, corn steep liquor, sweet sorghum, bagasse, sugar beet tubers, etc. are used as potential material for bioethanol making in different countries. Wheat straw deposits are one among the residues produced in substantial amounts globally, including Ethiopia. However, the elimination of lignin out of lignocelluloses untreated residues is the most critical step. Various pretreatment methods are explained before by numerous researchers with chemical, physical, biological, and ionic liquid pretreatment. This review carefully evaluates the performance of highly capable and recent techniques of hydrolysis and discusses the potential of wheat straw residue for bioethanol production, using less energy-demanding and more eco-friendlier techniques than the recent commercial pretreatment techniques. The most popular of these is the ionic liquids (ILs). Important pretreatment steps by ionic liquids, such as 1-allyl-3-methylimidazolium chloride,1-ethyl-3-methylimidazolium acetate, 1-butyl-3methylimiazolium,1-ethyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium hydrogen sulfate, 1-butyl-3-methylimidazolium thiocyanate, 1-ethyl-3-methylimidazolium diethyl phosphate, 1-methyl-3-(4-sulfobutyl) imidazolium bisulfate, and cholinium taurate, will be evaluated. Additionally, critical parameters affecting the treatment process, such as temperature, the ratio of ionic liquids to residue dose, concentration of ionic liquids, and time taken, would also be discussed.

A new immobilization process of Saccharomyces cerevisiae cells with calcium alginate and coating with solubilized chitosan in citric acid solution was developed. The biocatalyst is used in fermentation processes to produce bioethanol fuel through the use of carbon sources such as glucose, sugarcane juice, and corn hydrolysate, which provided very good yields of productivity (71.3–88.7%) and shows excellent biocatalyst stability during all production processes.

This project describes the processes that were implemented during the experimental tests to obtain ethanol from the ripe plantain fruit, going through the treatment, fermentation and distillation stages. Afterwards, the alcoholic grades of the different obtained ethanol samples were measured, to select the samples with the greater alcoholic grade and inject them to the HZSM-5 packed bed reactor, to determine the amount of ethanol that oligomerizes to obtain fuel. Through the experimental analysis, appropriate conditions in the distillation temperature and fermentation time were established for the process of obtaining bioethanol, as well as the temperature of the reactor and the spatial velocity (WVHS) in the biotransformation process of ethanol to high octane gasoline, using a catalytic bed heterogeneous reactor. Grades of 50 resulted in the process of obtaining the bioethanol, and a selective performance of 23.5% of the biofuel was yielded. The gasoline was characterized by means of INEN (935:2016) standardized analyses for commercial gasoline, with which an octane number of 96.5 was determined, thus obtaining a gasoline of greater octane rating than the standard (super) gasoline commercialized in Ecuador.

The continuous rise in CO2 emission is a big reason behind global warming, with the passage of time, it is getting worse. Research on algal bioenergy has opened many ways for energy production as well as reducing CO2 in the environment by capturing it with its unique systems. In 1942 Harder and von Witsch unveiled the idea of microalgae growth to obtain lipids either in the form of food or fuel. Algae can be used to get or might be converted to different types of fuels. To achieve this objective, variable techniques can be applied, depending upon the phase and kind of cell being used. This chapter will add to the comparison of reliability of various procedures, for treatment of distillery wastewater prior to utilization as a nutrient source for algae. Chlorella vulgaris SR/2, a strain has been used for the study of materialization of CO2 from distilleries. It was concluded from the study that the distillery water priory treated with biological techniques have more ability for the better growth of algae. The environment is accommodated with variable amounts of CO2, luckily microorganism who can synthesize their own food by using carbon such as cyanobacteria and algae are able to survive in both high and low levels of carbon dioxide. Excellency of the pathway is more enhanced with carboxysome or the pyrenoid like structures which carry Rubisco. Oil is extracted and the other remnants of algae are pelletized after drying. These pelletized remnants are used in industry for power generation after being burnt.

In the coming future, natural energy sources such as diesel and petrol are going to be diminished. Therefore, interest in alternate sources of reliable, affordable, and sustainable energy has prompted much attention in the past three decades. Bioethanol is one of the promising alternatives, which is obtained from different biomass feedstocks. Bioethanol production from biomass is a well-established technology. This chapter provides a detailed insight on the current technologies for sustainable production of bioethanol from Indian bamboo using enzymatic saccharification technique, sweet sorghum bagasse through microwave irradiation approach, oil palm frond through ultrasonic irradiation method, sweet sorghum stalk via advanced solid-state fermentation system (ASSF), lignocellulosic through low-intensity pulsed ultrasonic methodology, sugarcane bagasse through hydrolysis approach using yeast cellulolytic enzymes, water hyacinth Eichhornia crassipes using an approach based on the preparation of the saccharified solution, sugarcane bagasse through sono-mediated enzymatic saccharification protocol, reed straw and corn stover using liquid hot water (LHW) pretreatment method, wheat straw using gamma irradiation approach, sugarcane bagasse through consolidated bioprocessing technique using Phlebia sp. MG-60, waste of date palm fruit using solar energy, and mandarin peel wastes using steam explosion method. Further, the chapter discusses industrial scale formation processes of bioethanol from sugar-, lignocellulosic-, and starch-mediated feedstocks. Moreover, the chapter also summarizes the commonly used feedstocks for sustainable and cost-effective bioethanol production and the biochemical reactions involved in the transformation of vegetative biomass to bioethanol. Pros and Cons of each sustainable approach for bioethanol production are discussed in detail, which will be very fruitful for the research community to get knowledge about the finest technologies, improve traditional methods, and develop further new more reliable, affordable, and sustainable methodologies for bioethanol production.

Depletion of fossil fuel resources along with their disadvantages including greenhouse gas emission, pollution, price enhancement, and increased demand of fuel leads to search for alternative fuel sources from renewable substrates. One of the major bottlenecks of global economy as well as environment sustainability is an urgent requirement for alternative fuel production and climate alteration diminution. Bioconversion of lignocellulosic biomass into biofuels is an unavoidable necessity for development of green economy. Biorefining of lignocellulosic biomass provides sustainable development of socioeconomic strategies. Low-value lignocellulose biomass (weed, by-products of wood, agro-residues, and recycle paper) is a favorable resource over traditional substrates. The biofuel production from lignocelluloses biomass by fungal consortium is cost-effective and eco-friendly process. Lignocellulosic plant sources consist of lignin, cellulose, and hemicellulose in various proportions. The hydrolysis of these polymeric components by fungal enzymes is a promising green approach. The development of fungal consortium and selection of microbial strains are a concern in this process. The fungal consortium composed of complex and diversified strains include cellulase, laccase, and xylanase enzyme-producing fungal strains along with ethanol-producing strains. Potential degradation of whole lignocellulosic substrates is possible by white-rot fungi. White-rot fungi is ubiquitous in nature; various strains including Phanerochaete chrysosporium, Trametes versicolor, Pleurotus ostreatus, Cyathus stercoreus, etc. are significant strains for lignin degradation. Several advantages were reported by fungal consortium for biofuel (ethanol) production with high productivity and sustainable approach for solid waste management by green technology.

The rapid exhaustion of fossil fuels and greenhouse effect leads to work on alternate energy and fuel source. In which, ethanol and methanol are widely discussed as an alternate for fuels over the decade. Fuels derived from the microbial biomass are one of the most promising renewable energy resources when compared to the conventional fuels from the petroleum reserves, which create excessive green gas emissions. The microbes are ubiquitous and many microbes are capable of converting the carbon source into primary metabolites, especially alcohols. Waste material generated from the industries like biodiesel, cassava, paper and pulp industries are rich in carbon and cellulose, which can be utilized by the microbes as carbon and energy source for the production of ethanol and methanol.

Lignin is a complex organic material connecting cells, fibers, and vessels which constitute wood and other lignified components of the vascular plants. Because of its complex structure consolidated by three-dimensional cross-linking, it is highly inflexible and recalcitrant. The degradation of lignin is required for the efficient utilization of lignocellulosic biomass for the production of biofuels and other cellulose-based products. Removal of lignin is also necessary for the production of paper from wood during the process of delignification and bleaching. Existing physico-chemical methods of lignin degradation are cost and energy incentive and result in generation of toxic waste products. Biodegradation of lignin involving lignin-degrading microbes and their enzyme system is more efficient and environmentally sound approach. Biodegradation of lignin is considered as sustainable technology for the disposal of lignocellulosic biomass and its utilization for the production of value-added products. Among microbes, white rot fungi efficiently degrade lignin with the help of their oxidative extracellular ligninolytic enzymes in general and laccases (benzenediol oxygen oxidoreductase, EC 1.10.3.2) in particular. Laccases are multinuclear enzymes which effectively degrade lignin. In the presence of suitable mediators, laccases hold the potential to oxidize non-phenolic proportion of lignin and other substrates. In the backdrop of aforesaid context, this chapter is an attempt to put forth the details of role of fungal laccases and laccase mediator system in degradation of lignin.

Lignocellulosic materials have been shown to be essentially good feedstocks in the production of simple sugars, which may be used as starting materials in the production of a range of bioproducts. While high yield of sugars from lignocellulose and conversion of lignocellulosic and/or simple sugars to several bioproducts have been reported, efficient recovery of these products remains a challenge, especially if a food or medicinal-grade product is envisioned. Although many separation techniques have been proven to recover value-added products from fermentation broth, there is still a continuous search for alternative methods with additional advantage with respect to product safety and/or yield. The high pressure technique of supercritical fluids extraction and fractionation using CO2 is one such methods. However, these techniques have to meet various requirements such as high separation efficiency, biocompatibility, environmental acceptability, distribution coefficient and appropriate solvent for the isolation of targeted compound from aqueous broth. Extraction of organic compounds from aqueous solution using CO2 has been demonstrated, mainly for ethanol, studies dedicated to other organic compound mixtures in aqueous solution are scarce. It was shown in this review using experimental data that an integrated bioprocess-supercritical carbon dioxide process can be developed for production and recovery of some selected bioproducts (bioethanol, acetoin and vanillin) produced in high, medium and low concentrations in fermentation broth, respectively.

Conversion of lignocelluloses to bioethanol takes place in three main stages, namely pretreatment to remove lignin and expose the crystalline structure of cellulose; enzymatic hydrolysis to convert cellulose and hemicellulose to simple sugars and microbial fermentation of sugars to ethanol. The most important of these steps is the pretreatment step employed to eliminate lignin and reduce the crystallinity of cellulose to make it accessible for enzymatic hydrolysis for its conversion to glucose. The pretreatment step controls the efficiency of subsequent steps and also accounts for the maximum part of the production cost of biofuel from lignocellulosics. A large number of pretreatment methods including physical methods, chemical treatment, physico-chemical processes, thermo-chemical pretreatment and biological pretreatment are available. Among the various pretreatment methods, biological pretreatment is a promising approach because of low operational cost, does not produce waste and other compounds (phenolics) toxic to the fermenting micro-organisms and is less energy-intensive and environment-friendly. This chapter discusses some of the important pretreatment methods for the disruption of complex lignocellulosic structure and production of fermentable sugars.

Biobutanol provides an alternative fuel for petrol (i.e. Spark-Ignition) engines and has far better fuel properties than ethanol which is traditionally used in fuel blends. This biofuel can be produced from (second generation) ligno-cellulosic feedstock such as forestry and agricultural residues. There is an abundance of such agro-industrial residues available in Fiji. Biofuels produced from such residues can contribute towards the emission reduction targets as determined by Fiji’s Nationally Determined Contributions (NDC) Implementation Roadmap. Unlike the first generation biofuels, the production of biobutanol from lignocellulosic materials requires the additional steps of pretreatment and enzymatic hydrolysis followed by fermentation using the Clostridium bacteria, leading to the production of acetone, butanol and ethanol. This chapter first describes the methodology for the production of bio-butanol from sugarcane bagasse and hog fuel and reports on the yields that can be obtained. It then assesses the potential of producing butanol from sugarcane and timber industry residues and by-products. It is found that 115,203 tonnes of butanol can be produced from available residues like sugarcane bagasse, trash (cane tops and leaves), molasses and hog fuel which have the potential to avoid approximately 259 kt of CO2 emissions per year, which is approximately 41% of Fiji’s total emissions reduction target of 627 kt of CO2 per year.

Currently, the modern world is facing with a major challenge regarding the production of renewable energy for phasing out fossil fuels. Lignocellulosic biomass can potentially be used as a substrate for the production of a diverse range of different biofuels such as bioethanol while not triggering food vs. fuel debate. Generally, the bioethanol production from lignocellulosic biomass involves four major steps including lignocellulose delignification/pretreatment, hydrolysis (i.e., chemical or enzymatic), hydrolyzate sugar fermentation, and distillation. The economic and environmental feasibilities of the mentioned process could significantly be enhanced through the application of phytopathogenic fungi or their enzyme cocktails. Typically, necrotrophic pathogenic fungi have exceptionally high capabilities for a copious production of various hydrolytic enzymes with activity on wide range of plant biomass, compared to biotrophic or hemibiotrophic ones. In this chapter, ten filamentous plant-pathogenic fungi species belonging to six genera, including Fusarium, Aspergillus, Phoma, Cryphonectria, Ustilago, and Colletotrichum, have comprehensively been discussed in respect to hydrolytic enzyme capabilities from bioethanol industry viewpoint. On this basis, their potential for application in simultaneous saccharification and fermentation (or co-fermentation), separate hydrolysis and fermentation, and consolidated bioprocessing process has been investigated. Eventually, their genome richness in respect to the construction of lignocellulose-degrading microorganisms or ethanologens with astonishing hydrolysis production ability from these fungi has also been scrutinized.

Agricultural and crop residues serve as a renewable source for the production of bioethanol and other value-added chemicals. The residue which is left out after harvesting chili from chili plants constitute chili postharvest residue (CPHR). It is an abundant, inexpensive, and readily available source of renewable lignocellulosic biomass. Presently this is considered as a waste and disposed by burning after harvest. Hence this could be a viable biomass for second-generation biofuel production as well as for the production of other value-added products like biopolymer and industrial enzymes. Similar to other lignocellulosic biomass, chili postharvest residue also requires some kind of pretreatment for better enzymatic saccharification of cellulose by enzymes. The objective of the present study was to evaluate pretreatment liquor as well as the enzymatically saccharified biomass for second-generation biofuel, xylanase and biopolymer production.

Over the past few years, Rhodosporidium sp. has received a great amount of interest due to its ability to accumulate 50–70% lipid of their total dry cell weight. In addition, Rhodosporidium sp. has also been demonstrated to thrive on multiple carbon sources such as hexoses and pentoses, which made them the potential candidate for lipid production using mixed carbon sources. Despite these advantages, the feasibility of Rhodosporidium sp. as a biofuel producer is still questionable. Many strategies were developed for improving the lipid production in this strain. Genetic engineering also allowed the researchers to increase the tolerance to inhibitors and to enhance the consumption of carbon sources form lignocellulosic biomass. This chapter systematically presents the engineering strategies that have been employed for strain improvement and highlighted the potential of Rhodosporidium as a biotechnological chassis. The prospect has been further discussed, and needs of the engineering strategies and the recommendations for future research are also elaborated.

This chapter proposes an innovative biorefinery conceptual process for the production of carotenoids from microalgae using lignocellulose-based biorefinery products and/or by-products and pressurized fluids. The extraction process, which can be done also with microalgal biomass with high content of moisture avoiding high-cost downstream processes, involves the use of ethanol and 2-MethylTetraHydroFuran (2 MTHF) mixed or in a sequential form for selective extraction of carotenoids. 2 MTHF is obtained from furfural, which is produced as a by-product during lignocellulosic biomass (sugarcane bagasse, wood, corn stover, rice straw, etc.) pretreatment for ethanol production, for example. The solvent recovery step involves the use of CO2, which is obtained from ethanol fermentation as a by-product. Specific conditions for CO2 for temperature and pressure to achieve supercritical conditions would be applied in order to besides high solvent recovery and recycling provide a desirable selective carotenoid purification and encapsulation if a coating material is added. The two-step process can be converted in a one-step process minimizing carotenoid degradation if the extraction process is performed under higher pressure than that performed during extract precipitation. In addition, the proposed processing route can be well integrated into conventional existing biofuels production (gasification, combustion, etc.) scenarios using the solids recovered after carotenoids production as feedstock.

The major challenges associated with the anaerobic digestion of urban lignocellulosic biomass are its recalcitrance nature and the disposal of resulted digestate. In this study yard waste was thermally pretreated to overcome inherent recalcitrant nature during anaerobic digestion. The resulted digestate after anaerobic digestion, which poses a serious land disposal problem was hydrothermally treated to produce energy-rich solid biofuel knows as hydrochar. After pretreatment the biogas production was improved from 328 to 364 mL/g VS. Then hydrochar prepared from the digestate at a temperature of 180 and 200 °C for a treatment duration of 6 h. The produced hydrochar had a calorific value in the range of 20–23.5 MJ/kg as compared to 15 MJ/kg for raw digestate. The present research on integration of anaerobic digestion and hydrothermal carbonization not only improved the bioenergy production but also minimized the waste production.

Some concerns regarding the depletion of non-renewable sources of energy along with the environmental damage resulting from their use have motivated the search for alternative fuels. Ethanol is a renewable and important energy alternative for Otto-cycle engines. In such context, this study proposes the evaluation of carbon monoxide (CO) and total hydrocarbons (THC) concentrations and the performance of a spark-ignited non-road engine fueled with gasoline types A and C (GC, with 27% ethanol) and kerosene as adulterant in different proportions. Quality parameters of the fuel blends were also evaluated. The results revealed some difficulties in the identification of gasoline adulteration, relating to the current legal parameters in the conditions of mixtures and tests used in the study. Regarding the gaseous emissions, the addition of the adulterant resulted in an increase of the CO and THC concentrations to 74% and 78%, respectively, in gasoline type C with 30% adulterant, when compared to gasoline C free of adulterant. The addition of ethanol to the gasoline resulted in a reduction of the CO and THC concentrations to 64% and 56%, respectively, in relation to the pure gasoline (without ethanol), evidencing greater combustion efficiency due to the presence of the oxygenated fuel (ethanol).

Enhanced development of bioethanol for its use as a carbon-neutral renewable and clean fuel is ever-increasing as it reduces CO2 emissions and associated climate change; it is used as fuel mix and octane enhancer in gasoline and improves the ambient air quality. In comparison with conventional agricultural biomass, lignocellulose biomass is a potential and sustainable substrate for bioethanol production. Lignocellulose biomass commonly comes from terrestrial origins, but aquatic plants and weeds like water hyacinth can also provide adequate biomass for bioethanol production. Aquatic feedstock like water hyacinth has a decentralized availability and thus requires a distributed production strategy for efficient availability. Water hyacinth has been widely exploited for biofuel production with research dedicated to efficient pretreatment, enzymatic hydrolysis and fermentation strategies. Novel processes like CBP can increase the bioethanol conversion yield to about 92% of the theoretical value compared to ~50% by conventional methods along with a reduction in operational costs and inhibitors. Additionally, recent advances in genetically engineering have shown promising results for the generation of fermenting organisms with higher alcohol productivity and tolerance. The current chapter discusses bioethanol production from water hyacinth, various fermentation strategies and their limitations, microbes in fermentation and current advances and commercial status of bioethanol production.

In times of rethinking production processes and consumption habits to minimize the effects of global warming, it is crucial to find alternatives that lead to replacing fossil fuels by renewable materials. The development of technologies to produce chemicals and fuels from lignocellulosic biomass meets this environmentally friendly concept, thus decreasing fossil fuel dependency. Lignocellulosic biomass is rich in polysaccharides (cellulose and hemicellulose) which, after depolymerization of its constituents in soluble sugars, can be used as raw material to produce different bioproducts in individual processes or incorporated in biorefineries. To do this, heterogeneous catalysts, mainly acid-catalyzed hydrolysis, have a crucial role in the valorization of this renewable material, offering the potential to help convert cellulose to glucose. Therefore, important aspects are discussed regarding the characterization of the biomass composition; the main pretreatments for separating the cellulose, hemicellulose, and lignin fractions; and important advances in using heterogeneous catalysis, highlighting that acid-catalyzed hydrolysis of biomass is fundamental for glucose and platform chemical production.

The primary question many biofuels producers have is the suitability of densified products for biochemical and thermochemical conversion processes to produce liquid fuels. In general, the belief is the densification of biomass will increase biomass recalcitrance for both biochemical and thermochemical conversions. This chapter will discuss the suitability of densified products such as pellets and briquettes for biochemical conversion and thermochemical conversion pathways, such as gasification, pyrolysis, and combustion.