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A novel paper‐based biofuel cell with a series/parallel array structure has been fabricated, in which the cell voltage and output power can easily be adjusted as required by printing. The output of the fabricated 4‐series/4‐parallel biofuel cell reached 0.97±0.02 mW at 1.4 V, which is the highest output power reported to date for a paper‐based biofuel cell. This work contributes to the development of flexible, wearable energy storage device.

Unsorted, mixed waste office paper (MWOP) is an excellent substrate for conversion into fuel ethanol using a recombinant strain of Klebsiella oxytoca which ferments cellobiose and cellotriose to ethanol at near theoretical yields, eliminating the need for supplemental β-glucosidase. This organism was tested with commercial fungal cellulase in optimized simultaneous saccharification and fermentation experiments (SSF) using MWOP as a substrate (pH 5–15.2, 35 °C). Similar rates and yields were obtained with dilute acid-pulped (hydrolysis of hemicellulose) and water-pulped MWOP on a dry weight basis although viscosity was reduced by the acid pretreatment. In simple batch fermentations, 40 g/L ethanol was produced after 48–72 h with 100 g/L MWOP and 1000 filter paper units (FPU) of cellulase/L, a yield of 550 L of ethanol/metric ton. Cellulase usage was further reduced by recycling SSF residues containing bound enzymes in multistage fermentations. This approach reduced the requirement for fungal cellulase while retaining rapid ethanol production and high ethanol yield. In our optimal design, broths containing an average of 39.6 g/L ethanol were produced in three successive stages with an average fermentation time of 80 h (567 FPU of fungal cellulase/L; 6.1 FPU/g of substrate). This represents a yield of 0.426 g of ethanol/g of substrate, 539 L/metric ton, 129 gal/U.S. ton. MWOP contains approximately 90% carbohydrate. Thus the combined efficiency for saccharification and fermentation to ethanol was 83.3% of the theoretical maximum.

High feedstock cost and low oil yields per unit of land from temperate oilseed crops limit the growth of commercial‐scale biodiesel production. Recently, highly productive crops, such as sugarcane and energycane, have been engineered to accumulate triacylglycerides (TAGs) that allow the production of far more industrial vegetable oil than previously possible. A proof‐of‐concept suggests that biodiesel production from engineered energycane will be possible. However, before making efforts for scale‐up, it is critical to understand the commercial feasibility and economic competitiveness of this process. This study performs techno‐economic analysis of a unique biorefinery processing energycane to co‐produce biodiesel and ethanol. Comprehensive process simulation models were developed for two scenarios: (i) biodiesel from TAGs and ethanol from fermentation of sugars in juice and (ii) biodiesel from TAGs and ethanol from fermentation of sugars in juice and hydrolysis of carbohydrates in bagasse. Based on the target levels, the analysis was performed for energycane containing 0%, 5%, and 7.7% TAGs (d.b.). The biodiesel from engineered energycane was found economically viable and competitive to soybean biodiesel. Although the capital investment is higher compared to the soybean biodiesel plant, the biodiesel production costs ($0.66–$0.9/L) were lower than soybean biodiesel ($0.91/L). Biorefinery‐scenario‐1 processing energycane containing 7.7% TAG produces biodiesel with profitability (IRR 7.84) slightly lower than soybean biodiesel (IRR 8.3), but yields five times of biodiesel per unit land and is self‐sustainable for energy requirements. The surplus electricity can displace fossil electricity and provide environmental benefits. Monte Carlo simulation indicated that biorefinery is profitable with a 29%–65% probability (NPV > 0) which is largely controlled by feedstock composition and biodiesel market price. It is important to note that energycane can be grown on the marginal rainfed lands in S.E. USA, where soybean would not be viable. Biodiesel from engineered energycane would therefore be complementary to soydiesel in the United States.

Commercial‐scale production of microalgae biomass for biofuel and biochemicals requires a substantial amount of water and nutrients. Many studies are conducted to explore the potential of various aqueous streams originating from harvesting stage and different energy recovery steps as an alternative for water and nutrient supply. Presence of toxic organic compounds, unassimilated ions, particulate matter, and high alkalinity in post‐harvest water limit its recyclability. Nutrient recovery from biomass via anaerobic digestion (AD) and various hydrothermal processes is being explored. So, there is a need to understand the impact of harvesting methods, nature and impact of organic compounds, buildup of algogenic organic matter (OM), amount of unused nutrients, and salinity on water recycling. Optimum conditions for maximum nutrient recovery from AD and hydrothermal processes are discussed for effective nutrient recycling. This review is an attempt to understand the challenges associated with the recycling of aqueous streams for water and nutrient requirement for sustainable microalgae cultivation. The effectiveness of a recycling stream is defined here as “biomass ratio.” Possible growth inhibiting factors are identified, and their solutions are suggested along with potential directions for future research. Large‐scale sustainable cultivation of microalgae through recycling of different streams depends on better understanding of biological activity of algal OM through detailed characterization and in‐depth understanding of physiochemical properties.

In millennia, much attention has been paid toward agro‐industrial waste which consists of lignin and cellulosic biomass. In this perspective, biomass waste which consists of lignocellulosic mass is an inexpensive, renewable, abundant that provides a unique natural resource for large‐scale and cost‐effective bioenergy collection. In this current scenario, efforts are directed to briefly review the agro‐industrial lignocellulosic biomass as a broad spectrum of numerous functional ingredients, its utilization, and respective health benefits with special to wheat straw. Wheat straw is lignocellulosic mass owing to the presence of cellulose, hemicellulose, and lignin. Its microbial culture is the most important and well adjusted, for a variety of applications in the fermentation substrate, feed, food, medicine, industry, and agriculture in order to increase soil fertility. In industrial fermentation, wheat straw can be used as substrates for the production of a wide range of hydrolytic enzymes, drugs, metabolites, and other biofuels as a low‐cost substrate or a natural source. Conclusively, wheat straw is the best source to produce bioethanol, biogas, and biohydrogen in biorefineries because it is a renewable, widely distributed, and easily available with very low cost, and its consumption is protected and environment friendly. Wheat straw is a moiety which has health benefits including anti‐inflammatory, antimicrobial, anti‐artherogenic, anti‐allergenic, antioxidant, antithrombotic, etc., Wheat straw is the best source to produce bioethanol, biogas, and biohydrogen in biorefineries because it is a renewable, widely distributed and easily available with very low cost, and its consumption is protected and environment friendly. Wheat straw is a moiety which has health benefits including anti‐inflammatory, anti‐microbial, anti‐artherogenic, anti‐allergenic, antioxidant, antithrombotic, etc.

Future fermentations will be open, continuous and automatically controlled with fresh water and energy saving. The production strains will be extremophiles engineered by synthetic biology., Summary Microbial fermentations produce chemicals, materials, biofuels, foods and medicines for many years. The processes are less competitive compared to chemical industries. To increase its competitiveness, technologies must be developed to address the following issues including fresh water shortage, heavy energy consumption, microbial contaminations, complexity of sterile operations, poor oxygen utilization in the cultures, food‐related ingredients as substrates, low substrate to product conversion efficiency, difficult cells and broth separation, large amount of wastewater, discontinuous processes, heavy labour involvements and expensive bioreactors. Future industrial fermentations should be more effective with the above issues reasonably addressed. Recently, extremophilic bacteria have well addressed the above issues for future fermentation.

An efficient ionic liquids (ILs) recycle technology will increase the economic viability of lignocellulosic biorefinery. The availability of recycling 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) for rice straw (RS) pretreatment was conducted. The kosmotropic salt K3 PO4 (TKP) solution was used as anti-solvent for cellulose precipitation and forming a three-phase system consisting of biomass, ILs-rich and salt-rich phases. The upper ILs phase and the bottom TKP phase were recycled without additional purification, which significantly simplifies the process for recovering ILs. Subsequently, the RS pretreated with multiple reusing ILs (RPRS) were investigated by components analysis, structure evolution, enzymatic hydrolysis and fermentation experiments. The results showed that unpurified reusing ILs led to further delignification and improvement of enzyme accessibility of the pretreated RS. The reducing sugar yield of RS pretreated with 8th reusing IL (8th RPRS) could still reach 98.9%, and the ethanol and succinic acid concentrations achieved 91.9 g/L and 29.3 g/L by simultaneous saccharification and co-fermentation (SScF). The present study demonstrated that the ILs recovered by phase-separation process could be used for RS pretreatment, and achieving high titer ethanol fermentation. This article is protected by copyright. All rights reserved.

This article is a review of the scientific literature published in 2019 on topics relating to bioenergy from biofuel residues and waste. This literature review is divided into the following sections: Feedstocks, Biodiesel, Bioethanol, Hydrogen, Biohydrogen, Biofuel Residues, Microalgae, and Lignocelluloses.

Lignin is a primary component of lignocellulosic biomass and an underutilized feedstock in the growing pulping and biofuel industries. Currently, over 50 million tons of industrial lignin are produced annually from pulping and bioethanol processes in the world. Around 95 % of industrial lignin is burned as fuel in heat and power plants due to its complicated, destructive, and condensed structures hindering direct industrial utilization, while the remaining 5 % of lignin is used for potential applications, such as additives, binders, dispersants, and surfactants, through modification. Meanwhile, different biorefinery processes also produce a considerable amount of lignin with various structural features and properties. The development of technologies for its structural characterization is currently desirable for lignin valorization, which will improve the techno-economics of applications of lignins in industries.