BioEnergy Research最新文献

The purpose of this research was to develop an integrated biorefinery process of solid-state anaerobic digestion (SS-AD) and hydrothermal carbonization (HTC) for the co-production of methane and hydrochar using elephant dung (ED) as substrate. With a leachate recirculation rate of 4 times/day, the SS-AD presented the highest cumulative methane yield of 83.2 ± 1.7 NmL/g volatile solid (VS)_added and VS removal efficiency of 53.9 ± 0.3%. In subsequent HTC, the maximum higher heating value (HHV) of 10,078.5 ± 288.5 MJ/ton dry wt. was achieved for the digested ED without leachate recirculation under HTC temperature of 170 °C. In addition, the maximum mass and energy yields were 76.3 ± 0.8% and 84.1 ± 0.3%, respectively. The produced hydrochar had higher HHV compared to the raw digestate. Moreover, the HHV of the hydrochar was higher, and ash content was identical to conventional coal (lignite). An assessment of a full-scale elephant-sanctuary waste management scheme integrating SS-AD and HTC indicates that more than 10,078.5 ± 288.5 MJ of energy and 563.0 ± 5.2 kg dry weight of hydrochar could be recovered per ton dry weight of ED. The developed elephant dung management platform could enhance energy yield from ED while addressing environmental issues.

Eucalyptus branches and bark represent highly abundant and available feedstocks with great potential for obtaining bio-based products. Distinct and integrated pretreatment fractionation strategies for eucalyptus branches and bark were performed for the efficient production of xylooligosaccharides (XOS). By combining pretreatments, a high yield of XOS was obtained from eucalyptus branches and bark. The branches and bark were presoaked in 8% (w/w) sodium hydroxide at 60 °C for 30 min to provide a deacetylation effect. The residues were then hydrothermally treated. The findings revealed that 4.64% of XOS originated from the bark and 6.19% from eucalyptus branches. It has been demonstrated that xylan may be selectively depolymerized during pretreatment by preventing excessive hydrolysis through the use of deacetylation in the first phase of the process. More XOS was produced using hydrothermal treatment, yielding 8.00% (w/w) in the branches and 5.12% in the bark. A significant amount of XOS with DP 2–5 might be obtained in certain experiments, up to 60%, but the most abundant XOS are usually those with DP > 5 (approximately 80% of all XOS). This work provides new insights into the effective generation of XOS under relatively mild conditions by overcoming the recalcitrant structure of eucalyptus branches and bark, representing a noteworthy advancement towards forestry leftover valorization.

The goal of this research was to assess the efficiency of the liquid digestate treatment conducted with algal, environmental isolates illuminated entirely with sunlight. The photobioreactor was exposed to natural conditions and evaluated based on the reduction of chemical oxygen demand (COD), nitrogen compounds, and soluble phosphates. Microalgal and bacterial communities growing during the treatment process were studied. A high removal rate of soluble COD (= 91%) and nutrients (= 86%) was achieved. The average concentrations of nitrogen, phosphates, and COD in the reactor effluent were 95 mgN/L, 49 mg/L, and 735 mg O₂/L, respectively. The overall algae-bacteria biomass productivity of 22 mg/L/d, calculated on the total suspended solids (TSS) basis, was recorded. The microbial analysis revealed the dominance of Tetradesmus obliquus followed by Microglena sp. in the first 14 weeks of the experiment. At the end of the experimental run, Chlorella sorokiniana cells appeared as a result of illumination intensity changes. The dominating bacteria belonged to Firmicutes (26.31%), Patescibacteria (17.38%), and Actinobacteriota (14.86%) and could have been responsible for the transformation of nitrogen and oxidation of organic contaminants. The research demonstrated that natural sunlight can successfully be used for efficient liquid digestate treatment with the algae-bacterial community.

Bagasse and straw are the two feedstocks used to produce cellulosic ethanol from sugarcane. Although this technology is advancing commercially, the differentiation between bagasse and straw remains elusive. This work investigates bagasse and straw supply, conditioning, and pretreatment in a pilot-scale steam-explosion continuous reactor (~ 10 kg/h feed) to illuminate the critical feedstock differences for process scale-up. Evaluating biomass across four sequential harvest seasons (2018–2021) shows that straw supplied in bales requires extra conditioning to reduce mineral matter and particle size before feeding into the reactor. Moreover, straw composition is more variable and consistently has lower contents of glucan (35.6–38.8%) and carbohydrate potential (glucose + xylose, 649–704 kg/dry tonne) compared to bagasse (40.8–42.9%; 735–760 kg/dry tonne). Biomass pretreatments without (190 °C, 5–15 min) and with sulfuric acid catalyst (149–170 °C; 5–15 min; 0.5–5.12%, m/m) show that straw differs from bagasse by presenting a higher acid neutralization capacity and about 5% of labile glucans. These results suggest that straw crushing and aqueous pre-extraction are promising strategies to reduce the dissimilarities with bagasse, thus facilitating the development of feedstock-agnostic biorefining.

Abstract

One of the most important problems and the main obstacle of this process is the transformation of the complex structure of lignocellulose. One of the ways to break the lignocellulosic structure is to use suitable pretreatment compounds and nanoparticles with appropriate concentration. For this purpose, the synergistic effect of 6%NaOH pretreatment with different magnetite nanoparticle (MNP) concentrations was assessed for maximizing the biogas production. In this study, the optimal mixing ratio of MSW and SS codigestion was determined from our previous studies (MSW:SS 60:40). Application of the 6%NaOH pretreatment alone increased biogas and methane production by 24.6 and 35.4%, respectively, compared to the control. Also, the 6%NaOH pretreatment alone elevated cellulose by 85% while reducing lignin and hemicellulose by 64 and 33%, respectively. The greatest biogas and methane production was obtained in the reactor of 6%NaOH with an MNP concentration of 110 ppm, experiencing an 86 and 162% increase compared to the control. The greatest reduction in total solids and volatile solids was also obtained in this digestor by 76.6 and 79%, respectively, compared to the control reactor.

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.

Abstract

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.