BioEnergy Research最新文献

Rice straw hydrolysate produced in rice straw pretreatment, comprising a lot of fermentable sugars, is generally released into the environment. This not only causes environment pollution but also wastes fermentable sugars from rice straw. To alleviate environment impact, maximize ethanol production from rice straw, and reduce the cost of ethanol production, rice straw hydrolysate and NaOH-pretreated rice straw were converted to ethanol using ethanol-type fermentation and simultaneous saccharification and fermentation (SSF) by sludge. Meanwhile, microbial community in sludge was analyzed to find the relationship between ethanol production and microbial community succession during ethanol-type fermentation and SSF. Under the optimal condition of the COD, pH and oxidation–reduction potential (ORP) value of rice straw hydrolysate with 6280.56 mg/L, 6.7, and − 42 mV, ethanol-type fermentation with the sludge of 15 g obtained the highest ethanol concentration (8.34 g/L) and the highest COD removal rate (54.83%). For SSF, the maximum ethanol concentration (3.75 g/L) produced by pretreated rice straw and sludge from ethanol-type fermentation with the sludge of 15 g was higher than that (2.61 g/L) generated by pretreated rice straw and sludge from ethanol-type fermentation with the sludge of 22.5 g. This indicated that sludge from ethanol-type fermentation with the sludge of 15 g more efficiently converted rice straw to ethanol than sludge from ethanol-type fermentation with the sludge of 22.5 g. Microbial community analysis suggested that ethanol production had a negative correlation with the relative abundance changes of Bacteroidetes, when the relative abundance of Firmicutes constantly rose in ethanol-type fermentation and SSF. This study provides a scientific basis for maximizing ethanol production from rice straw by microbial regulation in sludge, which could further reduce the cost of ethanol production.

Xylooligosaccharides (XOS) are potential prebiotic ingredients for food industries, mainly obtained after xylan hydrolysis by endoxylanases. Enzyme immobilization offers opportunities for recovery and reuse, while also enhancing its physical and chemical characteristics, such as stability and catalytic efficiency. This work aimed to immobilize the SM2 xylanase derived from the xynA gene from Orpinomyces sp. PC-2 and to evaluate its potential for XOS production. For this, SM2 xylanase was immobilized using the cross-linking methodology. The free and immobilized enzymes were characterized regarding the effect of pH, temperature, and thermostability. The cross-linked enzyme aggregate was evaluated for reuse and storage conditions and used for xylooligosaccharide production. Both free and immobilized SM2 xylanase showed maximal activity at 60 °C. The immobilized enzyme was more active at acidic and neutral conditions, and the free enzyme showed greater activity at basic conditions. The half-life of the free and immobilized xylanase was 30 and 216 h, respectively. In reuse tests, enzymatic activity increased with each cycle, and there was no statistical difference in the activity of SM2 xylanase aggregate stored at 4 and 25 °C. After saccharification, xylobiose (0.895 g/L), xylotriose (0.489 g/L), and xylohexose (0.809 g/L) were detected. As a result, immobilization enhanced thermostability, shifted the pH of maximum activity to 5, facilitated reuse, and eliminated the need for refrigerated packaging. Finally, the xylooligosaccharides produced by the SM2 xylanase are known for their prebiotic role, providing potential application of the immobilized enzyme in the food industry.

The rapid proliferation of giant Salvinia (GS; Salvinia molesta) in various hydrostatic environments, such as ponds and paddy fields, poses a threat to water quality due to light obstruction. Thus, this study aimed to transform GS biomass into hydrochar or solid biofuel via hydrothermal carbonization (HTC). Several parameters were examined, including residence time, reaction temperature, and liquid-to-solid mass ratio (L/S). The Box-Behnken Design (BBD) was also employed to set the experimental conditions at three levels and factors. The examinations of reaction temperature (200–220 °C), residence time (2–6 h), and L/S ratio (12–20) were conducted. The physical and chemical characteristics of hydrochar were further analyzed to encompass higher heating value (HHV), proximate analysis, ultimate analysis, functional group, and morphology. The percent energy recovery (ER, %) was remarked for the experimental design response. The kinetic analysis and a comprehensive combustibility index, calculated from TGA/DTG curves, were employed to elucidate the combustion behavior of hydrochar. The optimal condition for hydrochar production, resulting in maximal ER, was identified at 220 °C, 6 h, with an L/S ratio of 16. The corresponding fixed carbon (FC), HHV, and mass yield were approximately 17.2%, 23.5 MJ/kg, and 51.4%, respectively. The H/C and O/C mole ratios in the sub-bituminous coal region. This study affirms the feasibility of converting GS biomass into a renewable fuel resembling low-rank coal.

Marine photosynthetic microbial fuel cells (mpMFCs) can utilize marine photosynthetic microorganisms to drive electrical energy-generating electrochemical reactions. Due to improved ionic mobility and superior electrical conductivity of seawater, it is a suitable electrolyte for operating bio-electrochemical devices at operating elevated salinities. This study examined the use of seawater as a conducting medium in two-chambered MFCs to enhance power production in conjunction with a marine photosynthetic biocathode as an alternative to the abiotic chemical cathode. Using a modified BG11 seawater medium as catholyte, marine cyanobacteria were grown and maintained in the MFC cathode compartment. After a significant quantity of biomass had formed, it was harvested for use as the substrate for anode microorganisms. Isolated marine cyanobacteria from photosynthetic biocathode were identified using 16 s rRNA and Sanger DNA sequencing. In electrochemical characterization, mMFC, maximum power density (P_max) was 147.84 mWm⁻² and maximum current density (J_max) reached 1311.82 mAm⁻². In mpMFC, P_max was 104.48 mWm⁻² and J_max was 1107.27 mAm⁻². P_max was 53.14 mWm⁻² and J_max was 501.81 mAm⁻² in comparable freshwater MFC employing platinum catalyst, which proves that mMFC and mpMFC worked better. Dapis pleousa and Synechococcus moorigangaii were identified as dominant marine cyanobacteria. It was demonstrated that mpMFC, operated using seawater and employing a cyanobacteria biocathode, is suitable for circularized renewable energy production. The outcomes of this study imply that mpMFCs are good candidates for circular renewable energy production.

Global energy consumption is increasing, and there is a growing demand for renewable energy systems that replace fossil fuels with clean alternatives. Low-cost organic material, including organic wastes, can produce clean energy while reducing environmental soil, water, and air emissions. Anaerobic digesters (AD) can convert multiple streams of organic materials to renewable natural gas (RNG) and electricity, but they require optimal operation to minimize costs. This study employs a dynamic mixed-integer linear programming model (MILP) to optimize the collection, allocation, conversion, and dispatch of energy resources. The model optimizes the location of AD facilities producing RNG and power from combined streams that include agricultural biomass, manure, and municipal solid waste. It also optimizes the hourly dispatch of RNG and electricity based on urban residential, industrial, and commercial energy demand. The analysis shows that AD systems could generate RNG with a levelized cost of $0.011/kWh, electricity at a levelized cost of $0.025 to $0.039/kWh, and fertilizer at a cost ranging from $0.035 to $0.055/kWh. Scenario analysis indicates that RNG production is a viable alternative to renewable electricity. These cost estimates vary by location. Larger municipalities could lower costs by leveraging economies-of-scale to reduce capital costs and infrastructure optimizations to minimize waste. Furthermore, optimized AD systems could provide dispatchable heat and power to alleviate energy demand spikes in constrained municipalities. Future studies could evaluate the feasibility of these use cases.

Pretreatment is one of the bottlenecks in the cost and energy-efficient biomass valorization. Deep eutectic solvents are potential candidates for being used to address these challenges. In this work, the deep eutectic solvent composed of choline chloride, and acetic acid was studied for its use in wheat straw fractionation. The pretreated biomass was assessed concerning the lignin and glucan content. Under optimized time and temperature conditions, defined using Doehlert matrix chemometric tool, of 3 h 47 min and 139.6 °C, the processed wheat straw contained as much as 42.5 ± 0.42 wt.% and 38.59 ± 1.26 wt.% of glucan and lignin contents, respectively. The need for biomass washing after the pretreatment with deep eutectic solvents and before the enzymatic hydrolysis step was also evaluated. The obtained enzymatic hydrolysis results, i.e., glucan to glucose yield of 27.13 ± 0.25 vs. 25.73 ± 0.08 for washed or unwashed biomass correspondingly, are equally good substrates. Fractal kinetic analysis of the data showed similar values of k and h for both glucose and xylose reactions between washed and unwashed biomass. This confirmed that biomass washing is an unnecessary step, which in turn opens room for biomass processing intensification.

This study investigates the correlation between both the chemical compositions and physicochemical properties of pretreated oil palm empty fruit bunch (OPEFB) fibre and their enzymatic saccharification/total glucose yield (TGY). Twenty OPEFB samples, pretreated with various aqueous pretreatments, with diverse cellulose (25.63–44.23%), hemicellulose (0.01–42.49%), and lignin (3.7–47.1%) levels, were examined for their correlation with TGY (8.5–40%). The quadratic regression model was verified significant (p-value = 0.0006, R² = 0.8006). It was found that the pre-refined OPEFB experienced greater cellulose loss (35%) compared to unrefined ones (9%), adversely affecting TGY. Among physicochemical properties analysed using SEM, FTIR, XRD, Py-GCMS, and XPS, only crystallinity index (CrI) was significantly correlated with TGY based on theoretical glucose concentration (TGC) (R² = 0.77, 0.91). Other characteristics (morphology, functional groups, crystallite size, S/G ratio, and O/C ratio) exhibited no significant correlation to saccharification efficiency, exhibiting random trends (R² < 0.5). OPEFB fibres with CrI of 30–40 could achieve 100% TGY based on TGC. In conclusion, regardless of pretreatments, chemical compositions predominantly affected TGY in the enzymatic saccharification of biomass. Among commonly used physicochemical analytical methods, CrI is most significant in this evaluation and OPEFB should be unrefined before treatment to avoid cellulose loss.

Graphical Abstract

The yield of green energy from solid-state anaerobic co-digestion (SSAD) has recently been enhanced by incorporating innovative pretreatment methods and nanoparticles. However, the environmental consequences of employing new processes have not been fully examined. In this study, the environmental impacts of three high-methane-yielding scenarios including SSAD of corn stover blended with dairy manure (DM) denoted as (SYM1), calcium hydroxide-pretreated corn stover (CpCS) blended with DM (SYM2), and the CpCS blended with DM and nanoparticles (SYM3) were assessed and compared the baselines of solid-state and semi-solid-state anaerobic digestion using a life cycle assessment (LCA) approach. The approach investigated the best management practices that would result in high methane yield and low environmental impact. Results of the life cycle assessment indicate the inclusion of calcium hydroxide and nanoparticle has minimal negative environmental impact. There was an environmental gain in GWP when corn stover was co-digestion with DM (SYM1) relative to DM mono-digestions (baselines) and the carbon footprint of SYM1 was less by more than 85% compared to SYM2 and SYM3. However, the large volume of untreated corn stover harnessed for SYM1 scenario resulted in over 75% fossil fuel depletion compared to the other scenarios. The surplus methane from the SYM3 (at least twofold of other scenarios and baselines) in conjunction with being the least with the environmental implication makes the scenario the most attractive option for on-farm practice capable of harnessing the growing organic waste volume. These outcomes can guide trade-off between pretreatment and nanoparticle application to reduce solid-state anaerobic digestion’s negative environmental impact.