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Alfalfa (Medicago sativa L.) is a promising bioenergy and bioproduct feedstock because of its high yield, N-fixation capacity, potential for planting in rotation with corn (Zea mays L.), and valuable protein co-product (leaf meal). Our objective was to examine the effect of growth environment on biomass yield, cellulosic ethanol traits, and paper pulp fiber characteristics of alfalfa stems. Landscape position (summit and mild slope), season of harvest (four harvests per season), and multiple years (2005 and 2006) provided environmental variation. Alfalfa stem samples were analyzed for cell wall carbohydrate and lignin concentration. Stems were subjected to dilute acid pre-treatment, enzymatic saccharification, and pulping processes to measure relevant cellulosic ethanol and paper production traits. Landscape position was not a significant source of variation for yield or any biomass quality trait. Yields varied among harvests in 2005 (1,410–3,265 kg ha−1) and 2006 (1,610–3,795 kg ha−1). All cell wall, conversion test, and paper production traits exhibited year by harvest interactions with no clear pattern. Total carbohydrates and lignin ranged from 440 to 531 g kg−1 DM and from 113 to 161 g kg-1 DM, respectively. Release of cell wall sugars by the conversion test ranged widely (419 to 962 g kg−1 DM). Fiber traits were similarly variable with length and fine content ranging from 1.24 to 1.59 mm and from 15.2% to 21.9%, respectively. Utilizing alfalfa biomass for cellulosic ethanol and paper pulp production will involve dealing with significant feedstock quality variation due to growth environment.

With realizing the potential of algal biomass as a good natural resource for the harnessing of valuable bioproducts, algal biomass production has gained a lot of interest in recent years. However, due to some limitations such as low harvesting efficiency, higher nutrient supply, and high water requirement, the production of algal biomass is uneconomical. Over the past several years, researchers are continuously working on growing algae as a biofilm for easy microalgae harvesting, concentration of algal biomass to a great extent, and requiring less quantity of water as compared to other microalgae cultivation methods. Most of the documented studies have been carried out on either use of algal biomass for tertiary treatment of wastewater or cultivation and harvesting of algal biomass for biofuel production. Limited research studies have documented other applications of the algal biofilm system. The present review paper summarizes the current knowledge on various factors affecting microalgae growth, development of algal biofilm, and operation of algal biofilm systems to help properly understand and optimize these factors for better economics, more positive environmental impacts, and successful potential applications of the attached growth systems. The important factors include the structure of algal biofilms, EPS matrix, supporting materials, nutrient availability, environmental conditions, and biofilm thickness and harvesting frequency. The potential applications such as wastewater treatment, CO2 sequestration, microalgae–microbial fuel cell, large-scale biomass production, and water quality improvement are also discussed.

The effects of the blends of charcoal fines and Schizolobium parahyba var. amazonicum (parica) wood on the briquette quality and on the combustibility of this solid biofuel is not fully understood, especially from fast-growing plantations with Amazonian tree species. In addition, this paper presents new information about the occurrence of inorganic elements that may contribute to increase the emission of toxic compounds in the combustion of parica wood, for example, Cl. Thus, this study evaluated the composition of charcoal and S. parahyba var. amazonicum wood for briquettes, investigating the occurrence of inorganic elements responsible for the toxic organochlorine contaminants. Different formulations between charcoal and S. parahyba var. amazonicum wood were analyzed and later compacted in a laboratory briquetting machine with temperature of 90 °C and pressure of 5 MPa. The chemical and elemental composition of S. parahyba var. amazonicum wood was determined using X-ray fluorescence spectrometry (μ-XRF). The briquettes produced were tested for bulk and energy densities, proximate composition, heating value, equilibrium moisture, and resistance to diametral compression. S. parahyba var. amazonicum wood had chlorine levels below the recommended by international standards for solid biofuel intended for non-industrial use (< 300 mg kg−1). S. parahyba var. amazonicum, despite being a fast-growing species, has ideal chemical characteristics for energy purposes (Cl, S, and ashes). The most suitable briquettes were those produced with 50% of charcoal and 50% of S. parahyba var. amazonicum wood. This solid biofuel showed higher heating value of 22.74 MJ kg−1 and ash content of 2.65% db.

Made available in DSpace on 2022-04-29T08:30:38Z (GMT). No. of bitstreams: 0 Previous issue date: 2022-03-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) This study aimed at investigating the binderless densification of biomass for the production of a durable solid biofuel by mixing cassava rhizome, sugarcane bagasse, and sugarcane straw. Six different treatments were applied with specific percentages of these three biomass feedstocks for the densification in a lab-scale press with heating of 120 °C. Three blend treatments and three 100% material treatments (without mix) were analyzed. Achieved briquettes were examined via various tests including proximate analysis, volumetric expansion, compression test, and energy index to assess the mechanical and energetic properties. Results indicated that the mixtures are suitable for the production of briquettes and treatment B2 was the best blend for briquette production. This study suggested that binderless densification of biomass can be achieved with the mixing of cassava rhizome, sugarcane bagasse, and sugarcane straw, which will support the development of qualified solid biofuels without the cost of binders. Department of Energy Engineering BioJoule - Biomass Densification Laboratory Department of Energy Engineering São Paulo State University (Unesp), Campus of Rosana, SP Department of Mechanical Engineering São Paulo State University, SP Department of Environmental Sciences Federal University of São Carlos, SP Department of Energy Engineering BioJoule - Biomass Densification Laboratory Department of Energy Engineering São Paulo State University (Unesp), Campus of Rosana, SP Department of Mechanical Engineering São Paulo State University, SP FAPESP: #2018/11837-2 FAPESP: #2018/14827-8 CAPES: 001

Microalgae are a non-food grade, fast-growing, and non-land competitive biomass with relatively high energy content. The high lipid and mineral contents of microalgae render it beneficial for the production of biofuels and value-added products. The complete energy-effective harnessing of microalgae potentials concerning biodiesel production is faced with drawbacks because of the energy-intensive steps required to harvest and dry microalgae. The limitations have impelled the search for alternative and low-cost utilization of microalgae in wet form for biofuel production. Anaerobic digestion (AD) is among the wet techniques for the valorization of microalgae that is gaining immense research attention because of its simplicity. Also, the products can be recycled to reduce material costs. This review is focused on the recent trends and comparison of the AD process to maximize energy recovery from microalgae biomass and co-digestion of microalgae waste coupled to biodiesel production (after lipid extraction), respectively. The yield of methane gas in these two processes is compared and the pros and cons of biogas production using microalgae biomass and microalgae waste considering that the former produces biofuels and the later value-added products are discussed.

The aim of this study is to cultivate Spirulina platensis and Scenedesmus obliquus microalgae in consortia using effluents of cattle waste anaerobic treatment in order to give possibilities to the production of microalgae biomass to biorefineries uses. The biomasses obtained were characterized to evaluate the potential for the production of biofuels and other bioproducts. The effluent was used in sterile and non-sterile conditions to better understand the influence of other microorganisms in N and P removal. The biomass obtained with the addition of 10% of sterile effluent in Zarrouk media (20%) presented 44.12 and 34.62% of carbohydrates, using Spirulina platensis in monoculture or the 50%/50% consortia of Spirulina and Scenedesmus, respectively, this biomass presenting the potential to be used to bioethanol production. Nitrogen and phosphorous removal were higher in non-sterile conditions and reached 92.7 and 49.66% of nitrogen and phosphorous removal, respectively, using the consortia and with the addition of 30% effluent in the media. The cultivation of microalgae in a consortium may be used to assist the treatment of water concurrently with the production of biomass to different applications.

The possibility of using waste distillery stillage (first-generation technology) after dilute acid pretreatment, as a medium for the preparation of beet molasses mash, for ethanol production according to the simultaneous saccharification and fermentation (SSF) technology, was assessed. The combination of lignocellulosic hydrolysates made from acid-pretreated stillage with sugar-rich beet molasses is an effective way of utilizing the first-generation ethanol production by-products in the second-generation ethanol production technology. It was demonstrated that the final ethanol concentration could be as high as 90 g/L. The process yield was over 94% of the theoretical yield when the molasses was diluted using acid-pretreated maize distillery stillage. An attempt to increase the pool of fermentable sugars by using cellulases to hydrolyze cellulose failed due to product inhibition in the fermentation medium with a high glucose concentration. A more than threefold increase in the concentration of ethyl acetate (even up to 924.4±11.8 mg/L) was observed in the distillates obtained from the media incubated with cellulases. The use of beet molasses combined with the hydrolysate of pretreated distillery stillage also changed the concentration of other volatile by-products. An increase in the concentration of aldehydes (mainly acetaldehyde to a concentration of above 1500 mg/L), methanol, 1-propanol, and 1-butanol was observed, while the concentration of higher alcohols (isobutanol, 2-methyl-1-butanol, 3-methyl-1-butanol) decreased. Interestingly, the use of cellulases in fermentation media from molasses and stillage hydrolysates resulted in an average fourfold increase in the concentration of this ester to a maximum level of 924.4±11.8 mg/L. Hydrolysates made from acid-pretreated distillery stillage, combined with sugar-rich beet molasses to boost the efficiency of the conversion process, can be successfully used in the production of second-generation fuel ethanol. However, further optimization of the cellulose enzymatic hydrolysis process is required for efficient use of the raw material.

Microalgae have been reported to exhibit mutualistic interactions with other microorganisms like bacteria, filamentous fungi, and yeast and help each other co-exist. The potential of microalgae to perform photosynthesis and accumulate lipids make them suitable candidates for lipid production. Biofuel production from various single oleaginous microorganisms is already in practice. However, the high cost of biomass harvesting, extraction of lipids, and contamination issues are significant challenges of biofuel bioprocess commercialization. Recent microalgal co-culture studies showed considerable potential for easy biomass harvesting and reduction in overall energy consumption cost. Therefore, microalgal co-culture could be an alternative to overcome these constraints and enhance biomass and lipid production. Additionally, the integration of the nutrient sequestration process from potential agro-industrial wastewater using microalgal co-culture can reduce the cost of the substrate requirement for cultivation as well as ecological load. The co-culture in wastewater has shown excellent total phosphate removal efficiencies by microalgae Chlorella sorokiniana and yeast Rhodotorula glutinis, nitrogen removal by microalgae C. sorokiniana with activated sludge, and ammonium-nitrogen removal by C. vulgaris and fungi Aspergillus sp. co-culture. This review summarized the current advances towards biofuel and its value-added production from various microalgae co-culture and compared it with monoculture fermentation. It also includes some critical challenges of co-culturing for the economically viable bioprocess development for biofuel production. Furthermore, techno-economic analysis and life-cycle assessment of co-culture technology were also discussed for biofuel production feasibility from microalgal co-culture.

Microalgal biodiesel is technically viable to power diesel engines. This third-generation biofuel has great performance of combustion and can reduce emission of greenhouse gases into the atmosphere. However, its production is currently very expensive, relative to petrochemical diesel. Development and implementation of strategies to optimize productivity and quality of biomass and thus ensure this future-proof biofuel is economically feasible to fabricate and competitive with diesel oil on an industrial scale is challenging. This meta-analytic overview documents the diversity of fastest-growing, oil-accumulating microalgae; performance of cultures and systems; strategies for inducing lipids; and quality and economics of microalgal biodiesel. The microalgae, Neochloris oleoabundans, Scenedesmus obliquus, Desmodesmus sp., and Micractinium sp., are hyperaccumulators of lipids. The genre, Micractinium sp., is a thermophile, and thus it can resist hydrothermal streams. Complementarily, it is the fastest to grow and the most productive in both biomass and biodiesel. This should be of great importance to roll-out sustainable, high-performance algal systems in marginal lands in tropical zones, where the heat often makes the planning and management of projects difficult and expensive. Heat shock, nutritional starvation, and photoperiod are the most effective algae-specific strategies for inducing mechanisms for lipogenesis in Ankistrodesmus dimorphus, Chlorella vulgaris and Leptolyngbya sp., Cylindrotheca closterium and N. oleoabundans, and Amphora subtropica and Dunaliella sp., respectively. Rhodococcus sp. produces a significant amount of biomass at very low cost, relative to diesel oil. The concept of synergistically co-culturing microalgae with this photosynthetically active bacterium may be an option to save the producer the expenditures and uncertainties of third-generation biodiesel.

The use of agro-industrial waste as substrate to produce enzymes has been widely studied in order to adjust the high productions of these biocatalysts with a reduction of the final cost in an ecologically correct process in the industry. This is the first work to use peach-palm (Bactris gasipaes Kunth.) waste for the production of carboxymethylcellulases (CMCase) by the Trichoderma stromaticum AM7 under solid-state fermentation (SSF) using the artificial neural network and genetic algorithm (ANN-GA) to optimize the cellulase production. ANN-AG was used to determine the optimal influence of nitrogen source concentration (2.46%), time (12 days), and temperature (26 °C) on the cellulase production with 98% of efficiency for algorithm prediction of endoglucanase activity. The predicted and experimental values of the CMCase activity in U/g of dry initial substrate (gds) were 122.9 and 120.0, respectively. After all optimization processes, the variation of these parameters allowed a final increase of 31.58-fold when compared to the initial fermentation. Moreover, the treatment of peach-palm waste with T. stromaticum AM7 endoglucanase had an effect on the degradation of the fibers analyzed by scanning electron microscopy and the saccharification of the waste by releasing reducing sugar (807.80 mg/g) for 8 h of incubation. These results are very promising to waste valorization and the biotechnological and industrial applications of cellulase of the T. stromaticum AM7 to food processes and biofuel production.

Lignocellulosic biomass is one of the most abundant raw materials in the world, and it is mainly composed of carbohydrate polymers (cellulose and hemicellulose) and lignin. Its applications vary from the production of pulp and paper, to the most recent plant-based bioethanol production, which has challenge due to low hydrolysis conversion rates by the inherit recalcitrance of biomass. The biomass is naturally resistant due the high complexity in the component organization and interaction in the cell wall. The application of pretreatment technologies is one of the most used strategies to overcome biomass recalcitrance. These techniques often require a catalyst to modify the lignocellulosic structure which can be acids, alkaline compounds, ionic solutions, organic solvents, and even pressurized steam among others. The type of catalyst dictates the name of the pretreatment involved. This work presents an overview of these strategies, along with some recent contributions from the scientific community to improve biomass conversion technologies. The discussion is focused on the key factors related to the recalcitrance and conversion process, as well as the composition and physicochemical properties.

Rice husk is a prospective bio-oil feedstock due to its plentiful supply, but its unfavorable characteristics like high moisture content, high ash content, and low energy density tend to jeopardize both the yield and quality of bio-oil produced by fast pyrolysis. Lately, various pretreatments, namely, washing, torrefaction (dry and wet), and their combined pretreatments, have been researched on rice husk with the aim of improving its unfavorable characteristics for bio-oil production. However, the influences of different pretreatments on pretreated rice husk and the subsequent bio-oil produced have not been compared. Hence, this review paper presents an overview of rice husk as a bio-oil feedstock and its pretreatment methods for bio-oil production via fast pyrolysis. Particular emphasis is placed on the rice husk characteristics and their impacts on the bio-oil production via fast pyrolysis, as well as the different types of rice husk pretreatment and their influences on the characteristics of pretreated rice husk, product yields of fast pyrolysis, and the composition and physical properties of the bio-oil produced. A comparison of the physicochemical properties of rice husk- and other biomass-based bio-oil alongside those of petroleum fuel oil is also outlined. Major challenges and future prospects towards the utilization of rice husk as a bio-oil feedstock and the integration of rice husk pretreatment with fast pyrolysis for large-scale applications are also discussed.

In this study, biomasses of microalgae Scenedesmus and Synechocystis species were thermochemically converted to biofuel in a fast pyrolysis process. The effect of pyrolysis temperature on the products yield was investigated. The optimal pyrolysis temperature for Scenedesmus and Synechocystis biomass was 500 °C and 600 °C, respectively, resulting in higher bio-oil yield of 35.3 wt% and 21.1 wt%. The produced bio-oil had higher high heating value (HHV) (35–40 MJ/kg) than that of beech wood source bio-oil (23–35 MJ/kg). The obtained biochar had low surface area but with considerable nitrogen, phosphorus, and other mineral content was suggested as fertilizer. It was concluded that the microalgae type and its cultivation and harvesting method affects the characteristics of the products and final energy efficiency as well. Energy efficiency assessment showed that the technology needs to be improved substantially to reduce the energy demand in cultivation, harvest, and pyrolysis step to be energy efficient.

Second-generation technology (2G) is currently the industrial route that is being developed with the potential to meet the demand for biofuels and bioproducts. The technology studied in the present work is based on the non-food processing of sugarcane straw, which is unlike the bagasse processing route (a lignocellulosic residue) that is commonly used in boilers for steam and electricity generation. In the last years, cellulosic ethanol plants worldwide include the utilisation of corn stover, sugarcane bagasse, wood waste and plant residues. Therefore, a communication based on industrial aspects using sugarcane straw is important in order to expand the knowledge regarding this promising technology. The main objective of this work included listing the results obtained in a cellulosic-ethanol production industry using sugarcane straw, located in the Northeast region of Brazil and taking into account the efficiency of pre-treatment, enzymatic hydrolysis and fermentation processes and comparing these results with data found in the literature regarding studies with similar efficiency. It was possible to observe that the production of ethanol from sugarcane straw at an industrial scale achieved a productivity of 200 l of ethanol per tonne of biomass, exhibiting 90, 70 and 85% of pre-treatment, hydrolysis and fermentation efficiency, respectively.

The development of biofuels as an alternative to the use of fossil fuels is growing worldwide due to environmental concerns and energy independence; thus, considerable technical progress has been achieved in biofuel production. Microalgae have been widely used for nutrient removal during wastewater treatment and produce compounds that can be used as feedstock for biofuel synthesis. In this work, the green microalga Coelastrum sp. was cultivated using industrial wastes: molasses as the carbon source and synthetic wastewater as the culture medium to determine the potential of its use for biofuel production. The use of synthetic wastewater (SWW) and molasses improved biomass production when compared with cultures carried out in a standard laboratory culture medium, such as tris-acetate-phosphate (TAP). Growth rates of 0.31 and 1.4 day−1 were attained during exponential growth rate with SWW and molasses and TAP media, respectively. The best results in biomass and lipid content, 2.29 ± 0.05 and 0.71 ± 0.03 g L−1, were obtained after 15 days of culture in SWW with molasses. The analysis of the lipid profile, produced by Coelastrum sp. cultured under these conditions, determined that the microalga can be considered as a high-quality feedstock for producing green diesel, bio-jet fuel, or biodiesel.

A recent study by DeCicco et al. (Climatic Change 138:667–680, 2016) claims that corn used for ethanol should not be considered to be inherently biogenically carbon-neutral because not all that corn was grown additional to the level otherwise. By assessing the extent of carbon neutrality of corn for ethanol using the reference point baseline approach and historical data that study concluded that the carbon intensity of US corn ethanol is 27% higher than that of gasoline. We develop a framework to determine the carbon neutrality of corn for ethanol by assessing the additional carbon uptake by crops using an anticipated baseline approach. We also apply this framework to determine the additional corn produced for ethanol and include the direct life cycle carbon emissions of only that portion of corn in the direct life cycle carbon intensity of corn ethanol. We implement this framework by integrating an economic model of the agricultural sector in the USA with a biogenic carbon model and life cycle analysis to quantify biogenic carbon uptake and direct life cycle emissions with and without corn ethanol expansion over the 2007–2027 period. We find that the combined biogenic carbon emissions and direct life cycle carbon emission intensity of corn ethanol (not including indirect land use related emissions) is 21% lower than gasoline. The lower value of this carbon intensity of corn ethanol compared with gasoline is robust to a wide range of parametric assumptions.

Torrefaction of biomass materials has received a tremendous attention over the years due to its ability to produce a high-grade solid biofuel with enhanced durability, excellent grindability, higher bulk density and calorific value, and greater energy density, as compared to the original untreated biomass material. It is a mild pyrolysis treatment technology under inert atmosphere which can improve the chemical and physical properties of raw biomass through the elimination of oxygen, reduction of moisture content, and change of chemical compositions. When raw biomass is mildly pyrolyzed in a default-oxygen or N2 atmosphere at moderate temperatures, the properties of raw biomass including low calorific value, hydrogen-carbon ratio, hygroscopicity, and grindability can be significantly enhanced. In the present review, the operating mechanism of different torrefaction processes including wet, dry, and ionic-liquid-assisted torrefaction is analyzed and discussed. More importantly, the reactor design for commercialization purpose, reaction kinetics and mechanism, economics, and sustainability of biomass torrefaction is discussed in detail. This review is extended to the torrefaction of agro-residue biomass since torrefied agro-residue-based pellets can be produced from agro-residues. The various technological applications of biomass torrefaction are also reviewed and the prospects in ensuring the continuous production of high-grade fuels are summarized.

For every 1 tonne of bananas produced, 3 tonnes of pseudostem waste is also created. The aim of this research is to improve the pre-treatment methods used in converting this renewable resource to bioethanol. The microwave-assisted liquid hot water and alkaline with sodium hydroxide were performed on banana pseudostem followed by saccharification and fermentation to ethanol. The liquid hot water pre-treatment was performed over a range of severities (1.88–4.84). The alkaline pre-treatment was carried out to evaluate the effect of NaOH loading (0.09–0.3 g NaOH g−1 dry banana pseudostem) and severity factor (3.65–4.84). The severity factor of 4.84 from the liquid hot water pre-treatment and run 1 (Log Ro 3.65, 0.09 g NaOH g−1 dry banana pseudostem) from the alkaline pre-treatment reached the highest enzymatic hydrolysis yields for each pre-treatment conditions and were chosen to be submitted to fermentation. Subsequently, simultaneous saccharification and fermentation (SSF) at 25 °C for 120 h, using samples from alkaline (Log Ro 3.65, 0.09 g NaOH g−1 dry banana pseudostem) and liquid hot water (Log Ro 4.84) pre-treatments, resulted in 92 wt% and 95 wt% of the theoretical ethanol yield respectively, comparing to 60 wt% from the untreated biomass. The liquid hot water is considered a more suitable pre-treatment, as it is more economical and is an environmentally friendly alternative compared to the alkaline pre-treatment. The latter can lead to pollution as the sodium discharge in the process effluent is difficult to recycle and so may limit its application on a commercial scale.

Marine algae are promising third-generation feedstocks for bioethanol production as they are fast growing, require minimal inputs, and do not compete for land. However, marine algae have complex cell walls which necessitate pretreatment prior to fermentation, and this represents a major component of the cost of bioethanol production. Standard pretreatment processes using acids are costly and generate hazardous waste streams. This study aims to develop an economic and environmentally friendly pretreatment process using ozonolysis for the marine algae Kappaphycus alvarezii and Gelidium amansii. Acid and ozone pretreatments were compared across the pretreatment, enzyme hydrolysis, and fermentation stages of bioethanol production. Acid pretreatment outperformed ozonolysis over the pretreatment and enzyme hydrolysis stages. However, it also generated as by-products the compounds 5-hydroxymethyl furfural (5-HMF) and levulinic acid (LA), which inhibited ethanol fermentation and reduced the efficiency of the process overall. Ozone pretreatment did not produce these inhibitory compounds, and as such outperformed acid pretreatment across the process as a whole. These results indicate the potential of ozonolysis as an economic and environmentally friendly pretreatment for the production of bioethanol from marine algae.

Based on a circular bioeconomy strategy, eucalypt wood fines rejected from a Kraft pulp line were used as starting material in a pilot-scaled fast-pyrolysis process. The bio-oil and its coproducts were characterized regarding their physical, chemical, and thermal aspects. We put in perspective their properties to bring forward considerations for applications on biofuels, materials, and precursors. The yields of the pilot-scaled fast-pyrolysis process reached interesting values even if compared with optimized laboratory conditions. The results indicated the highest heating values (22–27 MJ/kg) for bio-oil, char, and crust material. The higher water content of aqueous extract had a negative effect for its application as fuel. The lignin/carbohydrate ratio for the bio-oil (2.82) and aqueous extract (0.53) identified a higher concentration of lignin-derived compounds in the first, mainly syringyl units. Bio-oil and aqueous extract presented chemical compounds with many functionalities, such as syringaldehyde and levoglucosan, expanding their potential application for higher value-added products besides energy.

Due to the overuse of natural gas and petroleum in Bangladesh, the excessive greenhouse gas (GHG) emission continuously worsens the countries’ air quality. To resolve this environmental concern as well as determine the sustainable bioenergy sources, research on biomass for biofuel production has been highlighted recently. Therefore, this study emphasized to identify a novel biomass for solid fuel generation as well as designed a pilot-scale biofuel production scheme. The study endeavoured to characterize the bioenergy properties of a novel wetland moss species, B. dichotomum Hedw., collected from rainforest of Chittagong Hill Tracts (CHT), Bangladesh. Current study also presented the morphological edifice and elemental composition through scanning electron microscopy (SEM)-energy dispersive X-ray (EDX) analysis. Gross and net calorific values of moss were determined through bomb calorimeter by standard method, and they were 10.77 and 9.35 MJ kg−1, respectively. Moisture content, ash content, volatile matter, fixed carbon, and bulk density were characterized on air-dried basis through standard ASTM methods, and the outcomes were 10.74%, 55.3%, 28.29%, 5.67% and 44.09 kg m−3, respectively. Other physical bioenergy parameters were biomass characteristics index 3936 kg m−3, energy density 0.475 GJ m−3 and fuel value index 5.07. Apart from that, experimental results revealed carbon element 56.6%, oxygen content 42.1% on dry weight basis and O/C ratio 0.74 in sample biomass.

Most of the citizens in developing countries use charcoal for domestic cooking and small-scale enterprises because of its high calorific value, less smoke, and easy to transport. However, a lot of charcoal dust is generated from charcoal trading activities. The dust is left as heaps of solid wastes in urban areas and sometimes thrown in water streams, thus being a nuisance to both humans and the environment. This study aimed to develop and characterize charcoal dust briquettes bonded with wild cassava Manihot glaziovii and also use of bioethanol to enhance briquette ignition. The percentages of binder to charcoal dust were varied from 5 to 30%. Proximate analysis, density, ignition time, burning rate, burning time, and calorific value were determined. The density of the produced briquettes ranged from 0.67 ± 0 to 0.83 ± 0.1 g/cm3; percentage of moisture content varied from 3.4 ± 0.2 to 4.2 ± 0.2; ash content varied from 19.6 ± 0.6 to 21.5 ± 0; percentage volatile matter ranged from 19.8 ± 0.3 to 24.3 ± 0.4; and percentage fixed carbon ranged from 51.9 ± 1.1 to 55.3 ± 0.2. The calorific value ranged from 17.7 ± 0.7 to 19.7 ± 0.3 MJ/kg, ignition time 139 to 163 s, and burning rate 0.3 to 0.7 g/min while water boiling time varied from 14 to 19 min and burning time from 85 to 116 min. Ignition test revealed that bioethanol ratio of 15 mL to 56 g of the briquette showed the best briquette ignition characteristics. It was further found that the amount of binder used influenced the combustion properties of the briquettes. This study also showed that charcoal dust could be compacted to briquettes using Manihot glaziovii as a binder. The overall performance of the briquettes showed that 5% binder gave the best results in terms of combustion characteristics.

Hydrolysis can be considered as the bottleneck for biofuel production from microalgae due to the recalcitrance of this type of biomass. Thermochemical pretreatment is an effective and widely used process to solubilize different types of biomass. Nevertheless, the variability of the cell wall composition, among different microalgae species, hinders the development of a suitable pretreatment. In this work, the most relevant factors for thermochemical pretreatment to solubilize organic matter from microalgal biomass (Scenedesmus obtusiusculus) were analyzed and identified. The aim was to obtain hydrolysates, rich in soluble organic matter, that allow attaining higher hydrogen and methane yields than with raw microalgae, using a factorial design to identify the significant factors of the thermochemical pretreatment. The results showed that temperature (100 °C) and HCl concentration (3%) were the most significant factors to achieve carbohydrates solubilization close to 100%. Further, reaction time (1.7 h) and biomass concentration (30 g total solids/L) were also important to achieve up to 60% chemical oxygen demand (COD) solubilization. Overall, the microalgal hydrolysates produced 48 NmL H2/g VS and 296 NmL CH4/g VS, which is 1.7- and 1.3-fold higher hydrogen and methane yields, respectively, than raw microalgae. These results are meaningful because high soluble carbohydrates and COD would allow the application of high organic loading rates in continuous reactors for biofuel production using renewable biomass such as microalgae.

Microalgal biomass has been widely investigated as a source of renewable energy, but currently, some alternatives are not economically competitive. Thermochemical conversion of biomass is an alternative way to transform their organic compounds into liquid and gaseous fuels. The aim of this work is twofold; first, the pyrolytic process of the microalga Botryococcus braunii (BB) by thermogravimetric analysis, as well as the relevant reaction kinetic constants and related activation energies, is assessed. Secondly, a sensitivity analysis of the biomass gasification process with air using a thermochemical model was conducted to predict the composition of a syngas as a function of the biomass moisture content and the biomass/air ratio. The results showed that BB biomass is composed mainly of carbon (62.4 wt.%) with volatile solids of 84 wt.%, while the fixed carbon represents around 7 wt.%. Additionally, observed values for heating (27.86 MJ kg−1) and activation energy (~ 110 kJ mol−1) were different from other algal feedstocks due to the capacity of accumulation of liquid hydrocarbons of this. On the other side, the gasification process showed it was found that the moisture content in the biomass and biomass/air ratio variables are key parameters for reaction temperature and producer gas composition. Accordingly, with a suitable combination of these variables, it is possible to obtain a syngas composed of gaseous species with high energy content (CO, 18 vol.%; H2, 17 vol.%; and CH4, 2 vol.%.), which can be transformed through processes such as Fisher-Tropsch process into liquid biofuels such as kerosene or gasoline.

Briquettes are widely used as a renewable energy material for solving the problem of dependency and over-consumption of wood fuel as a source of energy for human use. However, their performance depends on the types and nature of binders used during the preparation and densification process. Most of the performance-related problems such as low yield and energy content can be significantly improved with the use of binders in right proportions. This review discusses the state-of-the-art of fuel briquettes and the influence of binder’s properties on the combustion characteristics, energy content, mechanical durability, and density of fuel briquettes. The compatibility between the binders and the fuel briquettes to obtain a better yield is also discussed with the resulting mechanical and combustion properties. The mechanical durability of fuel briquettes can be improved by reducing the content of lignin, fat, and other extractives in the binder, as well as improving the binder’s variables such as the particle size, texture, and quantity. By using binders mixed with phosphorus-based additives such as Ca(H2PO4)2 and NH4H2PO4, the combustion rate of fuel briquettes can be enhanced and the pollutant emissions during the combustion process can be reduced to the minimum. In addition, the higher the binders’ compacting pressure and processing temperature, the higher the density and energy content per unit volume of fuel briquettes.

Thermochemical conversion process is one of the most promising routes to harness the potential of oil palm biomass as renewable energy alternative in Malaysia. Despite this potential, there is a lack of comprehensive study that characterises the complete spectrum of oil palm biomass. In this work, thermogravimetric-mass spectrometry (TG-MS) results of five oil palm biomass, i.e., oil palm trunk (OPT), palm kernel shell (PKS), oil palm frond (OPF), mesocarp fibre (MF) and empty fruit bunch (EFB), in pyrolysis and combustion conditions are presented and analysed. Kinetic studies on the TG data of these biomass were performed using Coats–Redfern integral method and Sestak–Berggren function to determine the activation energy and the reaction mechanism at different thermal decomposition stages. Pyrolysis of hemicellulose, cellulose, and lignin occurs at 140–331, 235–435, and 380–600 °C, respectively, while combustion of hemicellulose, cellulose, and lignin took place at 140–313, 225–395, and 372–600 °C, respectively. The activation energy was the highest for cellulose decomposition in both pyrolysis and combustion cases. Phase boundary reaction dominated during hemicellulose and cellulose decompositions, while nucleation dominated during lignin decomposition and char oxidation. MS results show that majority of the gases came out between 250 and 600 °C, mainly from CH4 and H2O in pyrolysis case and from CH4, CO2 and H2O in combustion case. Other than these major gases, NO, NO2 and SO2 were also generated although in much lower proportion compared to these gases. Based on TG-MS results, the best potential application for each biomass was also identified where OPT and OPF are suggested for gasification and fermentation, PKS for bio-char production and combustion, MF for bio-oil production, combustion, and bio-char production and EFB for bio-oil and bio-char production.

Lignocellulosic waste (here municipal trimmings) is a promising sustainable feedstock for ethanol production, but requires costly and polluting pretreatment, often resulting in toxic by-products. Ozonation, nonpolluting, effective pretreatment method, is not used commercially due to high energy requirements of ozone production at high ozone doses needed. Our results, however, demonstrated that low-dose ozonation (15 min, accumulated TOD = 318 mg L−1) of water-submerged waste resulted in improved enzymatic saccharification efficiency (31% of cellulose) compared to a non-ozonated sample (12%) although only 20% of the lignin was removed. Ozonation up to 90 min resulted in better conversion however exceptionally long ozonation (6 h and beyond) resulted in reduced conversion. These results suggest that contrary to common hypothesis, short ozonation could offer an effective and feasible pretreatment method for high sugar release without the need for delignification. In addition, the ozonation process was accompanied by changes in absorbance, mainly at 280 nm, making it a useful tool for process monitoring. Net calculated energy balance was positive for all ozonation regimes, with increased process efficiency at lower ozone doses. Furthermore, ozonation can be generated on-site and on demand, enabling decentralized pretreatment operated near the feed source, thus overcoming transportation costs.

Corn stalk is not suitable for direct combustion due to poor grindability, high moisture content, and insufficient heating value. The aim of this study was to optimize reaction conditions to improve the quality of corn stalk char, and to investigate the effects of carbonization on the physicochemical and combustion characteristics of corn stalks and chars. Optimal conditions for the carbonization of corn stalk were investigated with regard to temperature, holding time, and particle size. Response surface methodology (RSM) provided satisfactory models of responses, and the optimal conditions for higher heating values were obtained as follows: temperature of 551 °C, holding time of 150 min, and particle size range of 0.8–1.0 mm. In addition, after carbonization, changes in surface morphology, functional groups, and organic elements were clearly observed on the chars. The optimal point char experienced fairly complete carbonization, and holds promise for use as a solid biofuel.

Soaking in aqueous ammonia (SAA) is a means of pretreating biomass at moderate temperatures and ammonia concentrations (15% w/w). To establish process consistency and scalability, sieved maize stover was pretreated at 50-ml, 300-ml, and 100-l scales. Each scale was carried out through different methods. Sealed reactor tubes were used for 50-ml pretreatment. Fabric dyeing apparatus was used for the 300-ml pretreatment and a commercial Littleford DVT reactor was used for 100-l pretreatment. For each scale, biomass washing and solid-liquid separations were scaled appropriately. Washed pretreated solids were analyzed for composition and recovery of dry biomass and carbohydrates calculated. Nearly 100% of the glucan content was recovered in pretreated solids at all three scales, indicating the viability of SAA pretreatment. Pretreated solids (15% w/w) were hydrolyzed in a 1-l twin Sigma blade mixer using Cellic CTec2 (15 FPU.g-glucan−1) followed by fermentation in shake flasks. Hydrolytic yields ranged 65–70% across scale treatments. In comparison, fermentative yields averaged 95% across scale treatments, indicating saccharification to be a rate-limiting step in effective bioconversion of lignocellulose.

In traditional methods, the ethanol production from starchy raw materials includes the stages of viscosity reduction, full hydrolysis, and fermentation, which are carried out in two or more steps. We propose to perform all these steps together with the method called P-SVHF (preheating followed by simultaneous viscosity reduction, hydrolysis, and fermentation). The sweet potato starch was hydrolyzed by applying a commercial enzyme mixture specially developed to degrade granular starch. Nevertheless, when starch was previously gelatinized, the ethanol production was 52% higher than that in which starch was in the granular form. Thus, the proposed method (P-SVHF) also includes the starch gelatinization stage (preheating). In the P-SVHF method, energy is saved through (i) reducing the mass that is heated (only sweet potatoes), and (ii) applying a temperature (76 °C) which is lower than what is usually used during the liquefaction (≥ 85 °C), then an energy saving of 48% in comparison with traditional methods was estimated. After the method definition, a central composite design was carried out to evaluate the influence of pH, temperature, and time in the SVHF. The significant contributions of the optimization were the time reduction, i.e., from 24 h to 18–19 h, and the ethanol conversion efficiency increased to about 93%.

The integration of the first and second generation (1G2G) ethanol production promotes the increase of biofuel productivity per hectare of planted sugarcane, as well as the main liquid waste stream: vinasse, derived from ethanol distillation. As a sustainable way for it disposal, biogas production from anaerobic digestion (AD) promotes environmental suitability while enabling bioenergy generation. This work evaluated the potential energy generated from AD applied to vinasse within the context of an integrated 1G2G sugarcane biorefinery. Data from a literature survey based the scenario modeling and assessment, including economic and environmental indicators to compare the studied alternatives. AD allowed at least 68% increase of released bagasse for 2G ethanol production compared to 2G base scenario, being able to even double 2G ethanol productivity to 30 L t−1 cane. Organic matter removal efficiency of vinasse AD played an important role in 2G ethanol production so that higher the efficiency, larger the fraction of bagasse released for ethanol production. Economic indicators showed the unviability of 1G2G sugarcane mill including AD unit when considering the current technologies for 2G ethanol production in view of their high operational costs; however, with the envisaged technologies for 2025, the internal rate of return (IRR) of 14.3 and 17% was achieved, when considering conservative and optimistic data for vinasse AD efficiency, respectively. The results evidenced the importance of investment in R&D especially in 2G ethanol production but also in the AD of vinasse to reach the viability of this business.

The key to sustainable and commercially viable biodiesel production relies primarily on species selection. Oleaginous species with high biomass productivity, lipid content, and lipid productivity are desirable. High growth rate of the species results in high biomass productivity, which leads to high lipid productivity. It is known that algal oil technology lacks commercial feasibility predominantly due to low biomass productivity and other factors. The use of a faster-growing organism, such as oleaginous bacteria, could offset this major disadvantage. Thus, the current study analyzes two model oleaginous systems: Rhodococcus opacus PD630 (a bacterium) and Chlorella vulgaris NIOT5 (a microalga) for their growth rate and lipid productivity. It was found that the bacterial growth rate was 25-fold the microalgal growth rate. The bacterium also showed 57-fold higher biomass productivity and 75-fold higher biodiesel productivity. Further, the analysis of a large number of literature data from relevant studies under different cultivation conditions showed that R. opacus PD630 has productivities far higher than various autotrophic microalgae. Similarly, a frequency distribution of data collected from the literature showed that Rhodococcus sp. has productivities in the higher range as compared to heterotrophic microalgae. Thus, bacteria could serve as a better alternative to microalgae toward developing a commercially viable biofuel technology. Further, the biodiesel characterization study showed that the quality of diesel from the bacterium was better than that from the microalga.

Environmental concerns and depletion of fossil fuels along with government policies have led to the search for alternative fuels from various renewable and sustainable feedstocks. This review provides a critical overview of the chemical composition of common commercial plant oils, i.e., palm oil, olive oil, rapeseed oil, castor oil, WCO, and CTO and their recent trends toward potential biofuel production. Plant oils with a high energy content are primarily composed of triglycerides (generally > 95%), accompanied by diglycerides, monoglycerides, and free fatty acids. The heat content of plant oils is close to 90% for diesel fuels. The oxygen content is the most important difference in chemical composition between fossil oils and plant oils. Triglycerides can even be used directly in diesel engines. However, their high viscosity, low volatility, and poor cold flow properties can lead to engine problems. These problems require that plant oils need to be upgraded if they are to be used as a fuel in conventional diesel engines. Biodiesel, biooil, and renewable diesel are the three major biofuels obtained from plant oils. The main constraint associated with the production of biodiesel is the cost and sustainability of the feedstock. The renewable diesel obtained from crude tall oil is more sustainable than biofuels obtained from other feedstocks. The fuel properties of renewable diesel are similar to those of fossil fuels with reduced greenhouse gas emissions. In this review, the chemical composition of common commercial plant oils, i.e., palm oil, olive oil, rapeseed oil, castor oil, and tall oil, are presented. Both their major and minor components are discussed. Their compositions and fuel properties are compared to both fossil fuels and biofuels.

One of the challenges with using sweet sorghum as an energy crop is that although fermentation of the juice to ethanol does not require enzymes, the juice can easily spoil. One strategy to avoid spoilage is to harvest the juice in the field, place it into a tanker for transport, and add the yeast immediately to initiate the fermentation process to begin during transport. Hence, it is also important to understand how the fermentation process is influenced by pH, temperature, and dissolved oxygen, since these parameters would not be “controlled” during transport. A full factorial design was applied to examine and optimize yield efficiency of ethanol production for the fermentation of sweet sorghum juice. Bioethanol yield efficiency was modeled using a linear equation. Under optimal pH (5.5), temperature (28 °C), and dissolved oxygen (0%) conditions, a maximum theoretical yield efficiency of 0.75 was achieved for bioethanol produced from M81E variety of sweet sorghum.

Replacing fossil fuels with renewable fuels derived from lignocellulosic biomass can contribute to the mitigation of global warming and the economic development of rural communities. This will require lignocellulosic biofuels to become price competitive with fossil fuels. Techno-economic analyses can provide insights into which parts of the biofuel production process need to be optimized to reduce cost or energy use. We used data obtained from a pilot biorefinery to model a commercial-scale biorefinery that processes lignocellulosic biomass to ethanol, with a focus on the minimum ethanol selling price (MESP). The process utilizes a phosphoric acid-catalyzed pre-treatment of sweet sorghum bagasse followed by liquefaction and simultaneous saccharification and co-fermentation (L+SScF) of hexose and pentose sugars by an engineered Escherichia coli strain. After validating a techno-economic model developed with the SuperPro Designer software for the conversion of sugarcane bagasse to ethanol by comparing it to a published Aspen Plus model, six different scenarios were modeled for sweet sorghum bagasse Under the most optimistic scenario, the ethanol can be produced at a cost close to the energy-equivalent price of gasoline. Aside from an increase in the price of gasoline, the gap between ethanol and gasoline prices could also be bridged by either a decrease in the cost of cellulolytic enzymes or development of value-added products from lignin.

This work presents a conceptual design of an integrated biorefinery using olive tree pruning as feedstock. The biorefinery combines a state-of-the-art thermochemical technology for producing high value-added antioxidants with an energy self-sufficient biochemical platform for lignocellulosic ethanol production. These plants are integrated by exchanging energy and feedstock. The process and design parameters employed in the plant designs are based on the authors’ own lab and pilot-scale data. The paper discusses the economic dilemma of using this feedstock for producing high value-added products in small amounts versus producing large amounts of low-profit biofuels. The feasibility of this production strategy at medium scale is demonstrated via a techno-economic analysis based on total production cost for each co-product. Each plant is energy integrated, and the energy performance of the bioethanol plant is assessed by calculating the end-use-energy ratio. Both analyses are parameterized with respect to plant capacity (100–1500 t dry weight (dw)/day) and raw material price (20–100 €/ton dry weight).

Microalgae are a promising source of protein and biofuels. This study involved the extraction of soluble proteins from raw microalgae using subcritical water hydrolysis followed by pyrolysis of the resulting spent microalgal biomass for bio-oil production. The extraction process produced solubilized protein in amounts up to 10 wt% of the dry biomass. The effects of hydrolysis temperature (150–220 °C), process time (90–180 min), and initial pH (2–12) on the chemical compositions and reactivity of the spent biomass as biofuel intermediates were investigated. It was found that when the temperature and time increased, the protein and carbohydrate fractions of the spent biomass were reduced, while their lipid fraction increased. A low initial pH led to lower protein content in the spent biomass. Compared with the raw microalgae, the spent biomass gave a higher yield of pyrolytic bio-oil that contained much less of the N-containing compounds and higher amounts of long-chain fatty acids (C16) and C14–C20 long-chain hydrocarbons. In addition, enhanced energy recovery and a reduction in the energy consumption of the pyrolysis process were the other benefits acquired from the protein extraction. Therefore, subcritical water hydrolysis was considered to be an effective process to recover solubilized proteins, enhance the properties of the spent biomass, improve the energy balance of the subsequent pyrolysis process, and raise the quality of the bio-oil.

Efficient conversion of both glucose and xylose in lignocellulosic biomass is necessary to make second-generation bioethanol from agricultural residues competitive with first-generation bioethanol and gasoline. Simultaneous saccharification and co-fermentation (SSCF) is a promising strategy for obtaining high ethanol yields. However, with this method, the xylose-fermenting capacity and viability of yeast tend to decline over time and restrict the xylose utilization. In this study, we examined the ethanol production from steam-pretreated wheat straw using an established SSCF strategy with substrate and enzyme feeding that was previously applied to steam-pretreated corn cobs. Based on our findings, we propose an alternative SSCF strategy to sustain the xylose-fermenting capacity and improve the ethanol yield. The xylose-rich hydrolyzate liquor was separated from the glucose-rich solids, and phases were co-fermented sequentially. By prefermentation of the hydrolyzate liquor followed fed-batch SSCF, xylose, and glucose conversion could be targeted in succession. Because the xylose-fermenting capacity declines over time, while glucose is still converted, it was advantageous to target xylose conversion upfront. With our strategy, an overall ethanol yield of 84% of the theoretical maximum based on both xylose and glucose was reached for a slurry with higher inhibitor concentrations, versus 92% for a slurry with lower inhibitor concentrations. Xylose utilization exceeded 90% after SSCF for both slurries. Sequential targeting of xylose and glucose conversion sustained xylose fermentation and improved xylose utilization and ethanol yield compared with fed-batch SSCF of whole slurry.

The Mexican tequila industry annually processes approximately 1 × 106 Agave tequilana plants, generating approximately 1.78 × 108 kg of bagasse per year. This biomass is considered an attractive alternative to fossil fuels as an energy source and to produce biofuels and/or chemical products because it is produced and used without adversely affecting the environment. The first aim of the present work was to determine the effect of temperature, the concentration of H2SO4, and reaction time on the hydrolysis of agave bagasse to maximize the fermentable sugars using a steam explosion. This step process generated 71.11 g/L of reducible sugars in the supernatant (59.29 % glucose, 29.05 % xylose, and 11.66 % fructose) and unconverted organic matter of enzymatic hydrolysis bagasse (35.4 % α-cellulose, 7.33 % hemicellulose, 49.91 % lignin, and 7.31 % ashes). A mathematical surface response analysis of the hydrolysis was used for process optimization. The second aim involves the study of the thermodynamics of the reforming of unconverted organic matter from enzymatic hydrolysis of Agave tequilana bagasse (ATB) evaluated by the Gibbs free energy minimization method for hydrogen production. The effect of the parameters on the system performance measures, such as reaction temperature (T), Water/Biomass ratio (WBR), and pressure (P), were also investigated. The maximum H2 production obtained was 23.2 mol of H2/271.5 g ATB with a WBR ≥ 11 and a temperature of 740 °C. These findings indicate that the temperature and WBR are essential factors in the production of H2, which was reflected in the efficiency of the process.

Ethanol produced from lignocellulosic feedstock is a promising alternative to fossil fuels and corn-sourced ethanol. However, it creates unique challenges in terms of requirements for breakdown to fermentable sugars, including the need for pretreatment and enzymatic hydrolysis of structural carbohydrates. Hydrolases from microorganisms are currently utilized for biomass hydrolysis in the production of lignocellulosic ethanol; however, expressing these hydrolases in lignocellulosic feedstock is a favorable alternative, due to the large availability of biomass and the potential for the feedstock to play a dual role as both biomass substrate and enzyme provider. This review summarizes recent achievements in hydrolytic enzyme expression in a variety of model plants and potential feedstocks, including strategies to improve enzyme yield and to prevent deleterious effects on plants hosts. We propose possible scenarios for utilizing enzyme-expressing transgenic feedstock and illustrate the potential benefits of using these crops for ethanol production. Furthermore, challenges are highlighted and potential solutions proposed to move the field forward to cost-comparable lignocellulosic ethanol.

Pyrolysis of animal manure produces biochar with multiple beneficial use potentials for improving soil quality and the environment. The kinetics and energetics of pyrolysis in producing manure-based biochar were reviewed and analyzed. Kinetic analysis of pyrolysis showed that the higher the temperature, the shorter the reaction time was needed for thermal decomposition and carbonization of animal manure. This kinetic information can assist in producing biochar with a desired proximate composition. Biochar with lower volatile matter (VM) content can be produced with either higher pyrolysis temperature or longer reaction time. Energetically, pyrolysis of wet manures is not sustainable due to high energy needed for drying moisture. However, co-pyrolysis with other high energy density wastes such as agricultural plastic wastes would produce not only energetically sustainable biochar but surplus energy as well. This could be used for local power generation.

A biorefinery may produce multiple fuels from more than one feedstock. The ability of these fuels to qualify as one of the four types of biofuels under the US Renewable Fuel Standard and to achieve a low carbon intensity score under California’s Low Carbon Fuel Standard can be strongly influenced by the approach taken to their life cycle analysis (LCA). For example, in facilities that may co-produce corn grain and corn stover ethanol, the ethanol production processes can share the combined heat and power (CHP) that is produced from the lignin and liquid residues from stover ethanol production. We examine different LCA approaches to corn grain and stover ethanol production considering different approaches to CHP treatment. In the baseline scenario, CHP meets the energy demands of stover ethanol production first, with additional heat and electricity generated sent to grain ethanol production. The resulting greenhouse gas (GHG) emissions for grain and stover ethanol are 57 and 25 g-CO2eq/MJ, respectively, corresponding to a 40 and 74 % reduction compared to the GHG emissions of gasoline. We illustrate that emissions depend on allocation of burdens of CHP production and corn farming, along with the facility capacities. Co-product handling techniques can strongly influence LCA results and should therefore be transparently documented.

Lignocellulosic biomass has a complex and rigid cell wall structure that makes biomass recalcitrant to biological and chemical degradation. Among the three major structural biopolymers (i.e., cellulose, hemicellulose, and lignin) in plant cell walls, lignin is considered the most recalcitrant component and generally plays a negative role in the biochemical conversion of biomass to biofuels. The conversion of biomass to biofuels through a biochemical platform usually requires a pretreatment stage to reduce the recalcitrance. Pretreatment renders compositional and structural changes of biomass with these changes ultimately governing the efficiency of the subsequent enzymatic hydrolysis. Dilute acid, hot water, steam explosion, and ammonia fiber expansion pretreatments are among the leading thermochemical pretreatments with a limited delignification that can reduce biomass recalcitrance. Practical applications of these pretreatment are rapidly developing as illustrated by recent commercial scale cellulosic ethanol plants. While these thermochemical pretreatments generally lead to only a limited delignification and no significant change of lignin content in the pretreated biomass, the lignin transformations that occur during these pretreatments and the roles they play in recalcitrance reduction are important research aspects. This review highlights recent advances in our understanding of lignin alterations during these limited delignification thermochemical pretreatments, with emphasis on lignin chemical structures, molecular weights, and redistributions in the pretreated biomass.

Biomass pyrolysis oil has been reported as a potential renewable biofuel precursor. Although several review articles focusing on lignocellulose pyrolysis can be found, the one that particularly focus on lignin pyrolysis is still not available in literature. Lignin is the second most abundant biomass component and the primary renewable aromatic resource in nature. The pyrolysis chemistry and mechanism of lignin are significantly different from pyrolysis of cellulose or entire biomass. Therefore, different from other review articles in the field, this review particularly focuses on the recent developments in lignin pyrolysis chemistry, mechanism, catalysts, and the upgrading of the bio-oil from lignin pyrolysis. Although bio-oil production from pyrolysis of biomass has been proven on commercial scale and is a very promising option for production of renewable chemicals and fuels, there are still several drawbacks that have not been solved. The components of biomass pyrolysis oils are very complicated and related to the properties of bio-oil. In this review article, the details about pyrolysis oil components particularly those from lignin pyrolysis processes will be discussed first. Due to the poor physical and chemical property, the lignin pyrolysis oil has to be upgraded before usage. The most common method of upgrading bio-oil is hydrotreating. Catalysts have been widely used in petroleum industry for pyrolysis bio-oil upgrading. In this review paper, the mechanism of the hydrodeoxygenation reaction between the model compounds and catalysts will be discussed and the effects of the reaction condition will be summarized.