BioEnergy Research最新文献

This study investigated the anaerobic co-digestion of sugarcane vinasse (V) and elephant grass silage (S) to produce methane. Box-Behnken experimental design was applied to verify the statistical effects of the elephant grass ensiling time (40, 80 and 120 days), alkaline pretreatment of elephant grass silage (0.5, 2.25 and 4.00% w/v NaOH) and S:V mixture ratio (25:75, 50:50 and 75:25) on the methane yield. The results showed that the ensiling process resulted in the low degradation of lignocellulosic substances, emphasizing the need for pretreatment using more efficient techniques, such as thermo-alkaline, to improve the breakdown of elephant grass fibres. COD removals varied between 35 and 85%, and carbohydrate consumptions ranged from 63 to 72%, with the higher efficiencies for both parameters occurring in the reactors with lower percentages of silage. Cumulative methane yield ranged from 190.77 mLCH₄/gVS (in the reactor with S:V of 75:25, 0.50% w/v NaOH and 80 ensiling days) to 1729.80 mLCH₄/gVS (in the reactor with S:V of 25:75, 2.25% w/v NaOH and 120 ensiling days). According to ANOVA, S:V ratio was the only variable with a significant effect (p < 0.05) on cumulative methane yield. Therefore, the findings indicate that the relative composition of substrates within the mixture exerted the most significant influence on the process, underscoring the critical role of vinasse as a co-substrate in enhancing methane production despite silage pretreatments.

The influence of ionic liquid (IL) characteristics, lignocellulosic biomass (LCB) properties, and process conditions on LCB pretreatment is not well understood. In this study, a total of 129 experimental data on LCB (grass, agricultural, and forest residues) pretreatment using imidazolium, triethylamine, and choline-amino acid ILs were compiled to develop machine learning (ML) models for cellulose, hemicellulose, lignin, and solid recovery. Following data imputation, a bilayer artificial neural network (ANN) and random forest (RF) regression, the two most widely adopted ML models, were developed. The full-featured ANN following Bayesian hyperparameter (HP) optimisation offered excellent fit on training (R²: 0.936–0.994), though cross-validation (R₂CV) performance remained marginally poor, i.e. between 0.547 and 0.761. The fitness of HP-optimised RF models varied between 0.824 and 0.939 for regression, and between 0.383 and 0.831 in cross-validation. Temperature and pretreatment time had been the most important predictors, except for hemicellulose recovery. Bayesian predictor selection combined with HP optimisation improved the R²CV boundary for ANN (0.555–0.825), as well as for RF models (0.474–0.824). As predictive performance of the models varied depending on target response, use of a larger homogeneous dataset may be warranted. The predictive modelling framework for LCB pretreatment, developed in this study, can be extended to similar biochemical process systems.

The presence of hemicellulose inhibits the enzymatic hydrolysis of lignocellulosic biomass. The purpose of this study is to investigate the effect of different hemicellulose fractions on the enzymatic hydrolysis and the way to eliminate the inhibiting effect caused by hemicellulose. Four kinds of hemicelluloses, namely, H_XF, H₁₅, H₃₀, and H₆₀, were first extracted from corn stover by ethanol fractional precipitation. The structures of hemicellulose samples were analyzed using Fourier transform infrared spectroscopy, ¹H and ¹³C nuclear magnetic resonance, and high-performance ion chromatography. The results show that H₃₀ has the strongest inhibition on the enzymatic hydrolysis of Avicel and corn stover, presenting inhibition ratio of 13.35% and 9.98%, respectively. The inhibition ratios of other hemicelluloses in Avicel and corn stover are 8–12% and 5–9%, respectively. However, the inhibiting effect caused by H₃₀ is removed by adding hemicellulase, which even presents a 4.99% increase in the efficiency of enzymatic hydrolysis of corn stover. The corresponding glucose concentration reached 68.11 g/L. This research could help design effective processes to promote the enzymatic hydrolysis of lignocellulosic biomass.

The present study aims to evaluate the use of cranberry bush fruit pomace (CBFP) (Viburnum opulus L.), which has recently become popular raw material, as a substrate in the presence of a reducing agent to increase biobutanol production by Clostridium beijerinckii DSMZ 6422. For this purpose, some factors were optimized, including the pretreatment, initial concentration of CBFP (5–20%), different types of reducing agents (ascorbic acid, L-cysteine, sodium dithionite and sodium sulfite), different concentrations of sodium dithionite (2.5–15 mM), inoculum concentration (5%, 10%, and 20%), and fermentation time (24–96 h). The maximum biobutanol, total ABE, biobutanol yield, and biobutanol productivity were 9.45 g/L, 12.08 g/L, 0.21 g/g, and 0.13 g/L/h in the medium containing enzymatically hydrolyzed 10% CBFP, 10 mM sodium dithionite, and 20% inoculum at the end of 72 h, respectively. These findings demonstrate that CBFP can be considered as a sustainable, economical, and viable substrate on biobutanol production for the first time in the literature.

The role of buffer in modulating the enzymatic hydrolysis environment of lignocellulose is crucial. However, studies on the impact of buffer on high-solid enzymatic hydrolysis remain limited. This study discovered that utilizing deionized water as a reaction medium, rather than the conventional buffer, did not influence the enzymatic hydrolysis of steam-exploded corn stover when the solid loading ranged between 15 and 25%. At 15% solid loading, the glucan conversion in the group treated with buffer was recorded at 89.8%, with a corresponding glucose concentration of 51.1 g/L. In contrast, the group without buffer exhibited a conversion of 88.9% and a glucose concentration of 50.5 g/L. The increase of acid groups in lignin was attributed to the formation of phenolic hydroxyls during steam explosion, which provided the substrate with the necessary conditions for buffering effects. Sequentially, during the high-solid enzymatic hydrolysis process, the substrate’s increased pore volume and specific surface area could potentially offset the buffering capacity, which led to the buffering effect becoming ineffective. Leveraging the self-buffering effect of the substrate, a fed-batch strategy was developed. This strategy replaced the water supplementation with buffers, augmenting the solid loading from 20 to 33% across six distinct feeding sessions over a span of 72 h. This not only reduced costs but also laid the foundation for the industrial viability of lignocellulosic high-concentration sugar production, thereby advancing the biofuels and bioproducts sector. These findings provide valuable insights for the exploration of solid reaction processes.

Lignocellulosic biomass is of significant industrial and scientific interest. Residues derived from different activities (agro-industrial work, food consumption, wood use, urban solid waste, etc.) and their subsequent use are key to extending circularity models to the different technological sectors that are beginning to implement circular economy cycles. Biorefineries are integrated platforms that value waste conversion into various value-added products. The generation of bioproducts derived from lignocellulosic waste (green fuels, green chemicals, and biomaterials) has promoted a shift from a fossil fuel–based economy to a more sustainable one. In addition, integrating biorefineries into the circular economy framework promotes a comprehensive approach to resource management, waste reduction, and sustainable development, which contributes to the overall resilience and efficiency of societal systems. There has been increased focus on the application of “canonical microorganisms” for residual biomass conversion, such as fungi, bacteria, and yeast. However, there is a plethora of other potential microorganisms that can be candidates for new biotechnological applications. This review aims to describe the valorization of different sources of lignocellulosic biomass in the global context, with a focus on Brazilian practice, and to emphasize how the use of microbial diversity is critical to enhancing current technologies, such as advanced liquid fuels. Finally, there is a discussion of the potential of anaerobic fungi, archaea, protists, and oomycetes as microbial product conversion technologies.

Three delignification treatments of corncob residues (CCR), including NaOH, formic acid, and sulfite treatments, were compared at the respective optimized condition and in light of chemical compositions, sugar recovery, and ethanol production. NaOH and sulfite treatment can remove lignin in the CCR efficiently. Though NaOH treatment showed a superior ability of delignification, its solid cellulose recovery is lower than that of sulfite treatment. The sulfite treatment has the highest selectivity between delignification and cellulose conservation. The formic acid-treated CCR still had high lignin contents because formic acid also accelerated the solvation of cellulose. In fed-batch simultaneous saccharification and fermentation (SSF) with 25% substrate loading, the highest 77.1 ± 2.33 g/L ethanol was from NaOH-treated CCR, corresponding to a CCR-to-ethanol yield of 0.208 ± 0.0021 g/g. However, the sulfite pretreated CCR also produced 68.2 ± 2.22 g/L ethanol, with a higher CCR-to-ethanol yield of 0.219 ± 0.0012 g/g. The high substrate dosage is beneficial to ethanol concentration but not beneficial to CCR-to-ethanol yield. The optimal substrate dosage required for ethanol production depends on the targeted aim (ethanol concentration or CCR-to-ethanol yield).

The characteristics of biochar vary widely depending on the type of biomass and thermochemical conversion method. In this study, four types of biomass (kenaf, rice husk, corncob, and wood chips) were subjected to hydrothermal carbonization and torrefaction at 220 °C, 260 °C, and 300 °C for 30 min. The acquired biochars showed significant differences in the type of reaction and biomass. At each temperature, the decomposition of volatiles was more severe in hydrochar (HC) than in torrefied char (TC). The mass yields of HC were 44.30–61.63 wt.% (220 °C), 20.89–37.04 wt.% (260 °C), and 12.59–29.19 wt.% (300 °C), whereas the mass yields of TC were 94.73–97.69 wt.% (220 °C), 87.19–95.04 wt.% (260 °C), and 68.22–80.78 wt.% (300 °C). The elemental and thermal characteristics of TC changed gradually as the reaction temperature increased, and the characteristics of HC were enhanced rapidly. Wood chip biochar that was reacted at 300 °C showed the highest heating values of 28.77 MJ/kg (HC) and 21.09 MJ/kg (TC). The results of chemical analyses showed that hydrothermal carbonization strongly affected the cleavage of inter- and intra-molecular carbon bonds in cellulose and hemicellulose. In contrast, torrefaction removed the thermally fragile moisture and hemicellulose content from biomass.

Graphical Abstract

Reed sawdust is a kind of paper mill waste with high cellulose and hemicellulose content. To promote the rational use of resources, it is essential to make full use of waste resources and transform them into new values. In this work, reed sawdust was pretreated with liquid hot water (LHW) at 170 °C for 30 min. A total of 39.00 g/L glucose was obtained after enzymatic saccharification of cellulose at 50 °C, 20 FPU/g-_{reed sawdust} cellulase, 25% (w/v) reed sawdust, in 5 replenishments. When the fermentation was performed 96 h, the medium contained xylo-oligosaccharides (XOS) 11.74 g/L and biomass 15.21 g/L, in which lipid was 4.14 g/L. After spray drying, feed additives containing 29.17% XOS and 10.29% docosahexaenoic acid (DHA) can be prepared. In particular, the hemicellulose and cellulose in reed sawdust are creatively used at the same time without separation, which greatly reduces the cost of purification in traditional processes and provides a new way for the high-value transformation of sawdust resources.

The surge in global biofuel demand is propelled by intensifying concerns over climate change and effective waste management. Government mandates on biofuel blending further boost this trend, underlining the significance of selecting renewable feedstocks, such as bioethanol and biodiesel, for biofuel production. The importance of selecting an efficient biomass pretreatment method cannot be overstated, given its status as the most energy-intensive and chemical-reliant step in the biofuel production chain. Thus, pretreatment becomes a crucial determinant in the feasibility and economic viability of biofuel technologies. Amid a wide array of pretreatment strategies, identifying a method that is both effective and sustainable is crucial for advancing biofuel commercialization. This review aims to rigorously evaluate both traditional and novel pretreatment techniques and their environmental footprints, leveraging life cycle assessment (LCA) studies from existing literature. By examining the sustainability of various pretreatment methods, this paper provides a holistic and clear view, serving as an essential resource for policymakers and industry stakeholders. It outlines the challenges faced in each phase of an LCA and proposes viable solutions. Additionally, the review furnishes valuable insights, recommendations, and directions for future research in achieving sustainable biofuel production.