Biodegradation Of Substances Research Articles

The effect of low-temperature plasma pretreatment on the biodegradability of polyethylene films

ABSTRACT With the increasing focus on environmental friendliness and sustainable development, extensive research has been conducted on the biodegradation of plastics. The non-hydrolyzable, highly hydrophobic, and high-molecular-weight properties of polyethylene (PE) pose challenges for cell interaction and biodegradation of PE substrates. To overcome these obstacles, PE films were treated with low-temperature plasma before biodegradation. The morphology, surface chemistry, molecular weight, and weight loss of PE films after plasma treatment and biodegradation were studied. The plasma treatment decreased the surface water contact angle, formed C–O and C = O groups, and decreased the molecular weight of PE films. With the increased pretreatment time, the biodegradation efficiency rose to 2.6% from 0.63% after 20 days of incubation. The mechanism was proposed that the surface oxygen-containing groups formed by plasma treatment can facilitate the bio-accessibility and be further decomposed and utilised by the microbes. This study provided an effective and rapid pretreatment strategy for improving biodegradation of PE.

Marine biodegradation of natural potential carrier substrates for seagrass restoration

AbstractSeagrass meadows provide essential ecosystem services but have been strongly declining over the past. Due to their incapability to recover effectively naturally, assisted restoration is used. This study aimed to test textile fabrics from natural derivatives to serve as carrier substrates for seagrass transplantation. The use of biotextile fabrics should enable seagrasses to better withstand hydrodynamic forces, especially in high‐energy areas and during autumn and winter storms in the initial phase of restoration, thereby increasing restoration success. Here, the biodegradation behavior of three natural textiles was assessed in different configurations. Coir, sisal, and jute meshes were fixed on the top and bottom of a coir nonwoven mat, forming a so‐called “sandwich structure.” Specimens were buried in the Ria Formosa Lagoon, Portugal, and retrieved weekly within the first months of burial and subsequently monthly over a total period of 3 months. Weight, tensile strength, and oxygen consumption rate were used as descriptors for biodegradation and tested after each retrieval. The results obtained in this study were discussed in the context of the application of the tested materials on Zostera marina transplants. Due to experimental errors, these results are solely used for discussion purposes in a conservative manner. Based on the three descriptors, coir mesh was the least degraded by the end of the experiment. Yet, it is vital to analyze the microbiome in a study site to understand the biodegradation process and based on that select a textile material. Coir fibers appear to be a good choice in highly biologically active areas to prolong the degradation process, whereas in areas with less activity sisal could be sufficient and even beneficial through the release of compounds that foster vegetations induced by degradation.

Bioremediation of trichloroethylene-contaminated groundwater using green carbon-releasing substrate with pH control capability

In this research, a sustainable substrate, termed green and long-lasting substrate (GLS), featuring a blend of emulsified substrate (ES) and modified rice husk ash (m-RHA) was devised. The primary objective was to facilitate the bioremediation of groundwater contaminated with trichloroethylene (TCE) using innovative GLS for slow carbon release and pH control. The GLS was concocted by homogenizing a mixture of soybean oil, surfactants (Simple Green™ and soya lecithin), and m-RHA, ensuring a gradual release of carbon sources. The hydrothermal synthesis was applied for the production of m-RHA production. The analyses demonstrate that m-RHA were uniform sphere-shape granules with diameters in micro-scale ranges. Results from the microcosm study show that approximately 83% of TCE could be removed (initial TCE concentration = 7.6 mg/L) with GLS supplement after 60 days of operation. Compared to other substrates without RHA addition, higher TCE removal efficiency was obtained, and higher Dehalococcoides sp. (DHC) population and hydA gene (hydrogen-producing gene) copy number were also detected in microcosms with GLS addition. Higher hydrogen concentrations enhanced the DHC growth, which corresponded to the increased DHC populations. The addition of the GLS could provide alkalinity at the initial stage to neutralize the acidified groundwater caused by the produced organic acids after substrate biodegradation, which was advantageous to DHC growth and TCE dechlorination. The addition of m-RHA reached an increased TCE removal efficiency, which was due to the fact that the m-RHA had the zeolite-like structure with a higher surface area and lower granular diameter, and thus, it resulted in a more effective initial adsorption effect. Therefore, a significant amount of TCE could be adsorbed onto the surface of m-RHA, which caused a rapid TCE removal through adsorption. The carbon substrates released from m-RHA could then enhance the subsequent dechlorination. The developed GLS is an environmentally-friendly and green substrate.

BIOGAS PRODUCTION POTENTIAL FROM ANAEROBIC CO-DIGESTION OF FOOD WASTE AND ANIMAL MANURE

The potential of biogas production by the anaerobic codigestion (AcoD) of canteen food waste and animal manure was investigated using the biochemical methane potential assay (BMP). The BMP assay was conducted under thermophilic temperature of 35 °C in a batch process at digestion time of 40 d. Waste substrate mixture was digested at a fixed proportion of 1:1 with different animal manure as co-substrate. Maximum cumulative biogas production (418 ml g-1 VS) was achieved during codigestion of food waste with pig manure > chicken manure (408 ml g-1 VS) > goat manure (319 ml g-1 VS). Generally, all manure codigested reactors produced 1.01 to 1.34 times more biogas than food waste alone indicating the synergistic effect of codigestion on overall biogas productivity. With analogous increase in biogas production, manure amendment produced significant (p<0.05) substrate biodegradation in terms of total and volatile solids loss. The microbial load profile prior and post-AD revealed significant reduction (p<0.05)in microbial species suggestion that anaerobic digestion can be adopted as a method of waste treatment and hygienization.

Coupling pathway prediction and fluorescence spectroscopy to assess the impact of auxiliary substrates on micropollutant biodegradation.

Some bacteria can degrade organic micropollutants (OMPs) as primary carbon sources. Due to typically low OMP concentrations, these bacteria may benefit from supplemental assimilation of natural substrates present in the pool of dissolved organic matter (DOM). The biodegradability of such auxiliary substrates and the impacts on OMP removal are tightly linked to biotransformation pathways. Here, we aimed to elucidate the biodegradability and effect of different DOM constituents for the carbofuran degrader Novosphingobium sp. KN65.2, using a novel approach that combines pathway prediction, laboratory experiments,and fluorescence spectroscopy. Pathway prediction suggested that ring hydroxylation reactions catalysed by Rieske-type dioxygenases and flavin-dependent monooxygenases determine the transformability of the 11 aromatic compounds used as model DOM constituents. Our approach further identified two groups with distinct transformation mechanisms amongst the four growth-supporting compounds selected for mixed substrate biodegradation experiments with the pesticide carbofuran (Group 1: 4-hydroxybenzoic acid, 4-hydroxybenzaldehyde; Group 2: p-coumaric acid, ferulic acid). Carbofuran biodegradation kinetics were stable in the presence of both Group 1 and Group 2 auxiliary substrates. However, Group 2 substrates would be preferable for bioremediation processes, as they showed constant biodegradation kinetics under different experimental conditions (pre-growing KN65.2 on carbofuran vs. DOM constituent). Furthermore, Group 2 substrates were utilisable by KN65.2 in the presence of a competitor (Pseudomonas fluorescens sp. P17). Our study thus presents a simple and cost-efficient approach that reveals mechanistic insights into OMP-DOM biodegradation.

Hydrogel Substrates of Collagen-Starch-Selenium Complexes for Stimulating Plant Metabolism

Various selenium (IV) complexes with essential amino acids such as phenylalanine, histidine, and tryptophan were encapsulated within polymeric matrices in hydrogel state based on collagen-starch, generating the biomatrices Col-St(Se-F), Col-St(Se-H), and Col-St(Se-T), respectively. 1 mg of each type of selenium complex was employed per mass ratio in matrices consisting of 60% collagen and 18% starch by mass. The advanced materials were surface-characterized using scanning electron microscopy (SEM), and their properties such as swelling capacity and degradation rate in commercial vegetable substrate were also evaluated. The amino acid involved in the selenium complex forms characteristic granules that determine the microstructure and porosity of the biomatrix; reporting that in the case of all biomatrices with selenium complexes, swelling capacities exceeding 2900% are shown, resulting statistically significant compared to the sole collagen-starch matrix. Likewise, the matrices exhibit resistance to degradation in the presence of the commercial vegetable substrate for up to 30 days of evaluation. In vitro biocompatibility studies with green and red tomato cells derived from fresh seeds reveal that the biomatrices Col-Str(Se-F) and Col-Str(Se-H) overstimulate the metabolism of green tomato cells, while for red tomato cells, greater stimulation is appreciated in the Col-Str(Se-T) biomatrix. The chemical composition of the biomatrices promotes the proliferation of these types of plant cells as inspected by epifluorescent microscopy. Such advanced materials could be successfully applied in agricultural applications related to tomato cultivation by regulating water capacity, substrate biodegradation, and stimulated metabolism to promote tomato growth.

Plant based surfactant combined sonication pretreatment on food waste for biomethane generation: Cost and energy procurement

Food waste (FW) can be used as an appropriate feedstock for bioenergy generation. However, the rate limiting hydrolysis step during Anaerobic Digestion (AD) limits the biodegradation of substrate. Hence, pretreatment of food waste is essential prior to AD to circumvent the rate limiting step. Ultrasonic pretreatment of FW has been restricted owing to its greater energy requirement, aggregation of FW particles and lignin binding to methanogenic enzymes during biomethanation process. These limitations could reduce the efficiency of the whole treatment. In this study an effort has been made to enhance the hydrolysis and to improve the methanogenesis by pretreating the FW with plant-based surfactant (saponin) coupled ultrasonic pretreatment. The ultrasonic alone (US alone) pretreatment experimental run was done by varying the ultrasonic power from 80 to 180 Watt and pretreatment time from 0 to 20 min. The ultrasonic combined saponin (US-saponin) pretreatment experimental run was done by varying the time from 0 to 10 min and saponin dosage from 0.0005 to 0.008 g/g TS. The outcome reveals that the specific energy input of 5052 kJ/kg TS, saponin concentration of 0.002 g/g SS, and 2 min pretreatment time was optimum to achieve the maximum solubilization of 37 % in US- saponin sample. The US alone demands a specific energy input of 25263 kJ/kg TS and a pretreatment time 10 min to achieve the maximum solubilization of 30.5 %. The US-saponin pretreatment shows 269 mL/gCOD of methane production, higher than the US alone (148 mL/gCOD) and control (53 mL/gCOD). Regarding energy and cost assessment, the US- saponin pretreatment shows 12.07 USD/ton of net profit, greater than the US alone pretreatment (−260.8 USD/ton).

Digestate quality and biogas enhancement with laterite mineral and biochar: Performance and mechanism in anaerobic digestion

Low biodegradation poses significant challenges to widespread adaptation of anaerobic digestion (AD) technology mainly attributed to low biogas yield. The biodegradation of organic substrate can be increased by enhancing direct interspecies electron transfer (DIET) by adding laterite mineral and biochar to the AD system. This study evaluates the efficiency of Laterite-mineral (LM), biochar (BC) and combination of LM and BC (LM-BC) to enhance biogas yield. Varying concentrations of LM (0.1–0.3%), BC (0.2–0.6 g/L), and LM-BC (0.05% + 0.1 g/L- 0.15% + 0.3 g/L) were introduced in AD systems of cow-manure (CM) at mesophilic conditions (37 °C). Results showed that BC0.6 g/L and LM0.3% produced the highest biogas (417 mLg−1 VS and 409 mLg−1 VS, respectively), followed by LM0.05% - BC0.1 g/L (367 mLg−1 VS). The BC0.6 g/L and LM0.3% also showed a higher chemical oxygen demand (COD) removal rate (41% and 40.2%, respectively) than the control group (30.1%) and LM0.05% - BC0.1 g/L (37.1%). Moreover, digestate with BC0.6 g/L and LM0.3% (5.73 and 5.65%, respectively) had higher fertility than LM0.05 % -BC0.1 g/L (5.39%) and control check CK (4.56%). Hence, BC0.6 g/L and LM0.3% are comparable to enhance the efficiency of AD system via DIET and are recommended for integration into large-scale AD systems.

Identification of functional microflora underlying the biodegradation of sulfadiazine-contaminated substrates by Hermetia illucens

The increasing discharge of antibiotic residues into the natural environment, stemming from both human activities and animal farming, has detrimental effects on natural ecosystems and serves as a significant driving force for the spread of antibiotic resistance. Biodegradation is an important method for the elimination of antibiotics from contaminated substrates, but the identifying in situ microbial populations involved in antibiotic degradation is challenging. Here, DNA stable isotope probing (DNA-SIP) was employed to identify active sulfadiazine (SDZ) degrading microbes in the gut of black soldier fly larvae (BSFLs). At an initial SDZ concentration of 100 mg kg−1, the highest degradation efficiency reached 73.99% after 6 days at 28 °C. DNA-SIP revealed the incorporation of 13C6 from labeled SDZ in 9 genera, namely, Clostridum sensu stricto 1, Nesterenkonia, Bacillus, Halomonas, Dysgonomonas, Caldalkalibacillus, Enterococcus, g_unclassified_f_Xanthomonadaceae and g_unclassified_f_Micrococcaceae. Co-occurrence network analysis revealed that a significant positive correlation existed among SDZ degrading microbes in the gut microbiota, e.g., between Clostridium sensu stricto 1 and Nesterenkonia. Significant increases in carbohydrate metabolism, membrane transport and translation were crucial in the biodegradation of SDZ in the BSFL gut. These results elucidate the structure of SDZ-degrading microbial communities in the BSFL gut and in situ degradation mechanisms.

Enhanced biodegradation kinetics in the copper-polluted sediment through bioaugmentation with water spinach and peanut husk-derived biochar

Stenotrophomonas maltophilia is a copper-tolerant bacterium that is used for improving the resilience and efficacy of microorganisms engaged in degrading substrate under high copper contamination. Examination of reaction kinetics indicates that the original consortia, Stenotrophomonas maltophilia and the mixed culture, follow a first-order reaction. The Michaelis-Menten model suggests that elevated copper concentrations exert stress on the original bacterial population and Stenotrophomonas maltophilia. However, when a mixed culture is employed during the bioaugmentation process, it brings about an enhancement in microbial resistance and performance. This study demonstrates that the poor performance of indigenous bacteria in media that are highly contaminated with copper can be improved by adding exogenous copper-tolerant bacteria. Furthermore, poor mass transfer in sediments can be improved by adding plants and biochar. This strategic addition serves a dual purpose: it increases the affinity of the substrate for sediments characterized by poor mass transfer and alleviates the inhibitory effects induced by copper. In addition, high percentages of Firmicutes, Bacteroidetes, and Euryarchaeota within the biochar matrix were verified to expedite the substrate biodegradation process even at high copper concentrations. The findings in this work provide an important basis for the future design of in situ bioremediation systems for heavy metal-contaminated sites.

Metabolic division of labor between Acetivibrio thermocellus DSM 1313 and Thermoanaerobacterium thermosaccharolyticum MJ1 enhanced hydrogen production from lignocellulose

In this consortium, DSM 1313 was responsible for degrading lignocellulose by cellulosome, while the highly efficient hydrogen-producing bacterium MJ1 consumed the sugar produced by DSM 1313 to grow and produce more hydrogen. The results showed that the maximum hydrogen production of 259.57 mL/g substrate was obtained at the inoculation ratio (OD600) of 2:1 (DSM 1313:MJ1) and substrate concentration of 10 g/L, 70.84 % higher than pure culture. Furthermore, MJ1 dominated the co-culture system by using various sugars resulting from the biodegradation of substrate, thereby relieving the inhibition of sugar on DSM 1313 and leading to more hydrogen production. In the co-culture system, the value of extracellular oxidation–reduction potential and the ratio of NAD+/NADH was lower than that of pure culture. Additionally, at the gene level, [NiFe]-hydrogenase and [FeFe]-hydrogenase related enzymes were significantly up-regulated, leading to a two-fold increase in hydrogenase activity of co-culture compared with pure culture.

Effects of Iron, Lime, and Porous Ceramic Powder Additives on Methane Production from Brewer's Spent Grain in the Anaerobic Digestion Process.

The process of anaerobic digestion used for methane production can be enhanced by dosing various additive materials. The effects of these materials are dependent on various factors, including the processed substrate, process conditions, and the type and amount of the additive material. As part of the study, three different materials-iron powder, lime, and milled porous ceramic-were added to the 30-day anaerobic digestion of the brewer's spent grain to improve its performance. Different doses ranging from 0.2 to 2.3 gTS × L-1 were tested, and methane production kinetics were determined using the first-order model. The results showed that the methane yield ranged from 281.4 ± 8.0 to 326.1 ± 9.3 mL × gVS-1, while substrate biodegradation ranged from 56.0 ± 1.6 to 68.1 ± 0.7%. The addition of lime reduced the methane yield at almost all doses by -6.7% to -3.3%, while the addition of iron powder increased the methane yield from 0.8% to 9.8%. The addition of ceramic powder resulted in a methane yield change ranging from -2.6% to 4.6%. These findings suggest that the use of additive materials should be approached with caution, as even slight changes in the amount used can impact methane production.

Nutritional evaluation of spent and uninoculated mushroom substrate of Pleurotus ostreatus grown on cassava peels and sawdust

<p><span>This study aims to evaluate the role of edible fungi in the biodegradation of mushroom substrate by comparing the mineral and proximate composition of a pasteurized substrate before inoculation (BI) with the spent mushroom substrate (SMS) of </span><em><span>Pleurotus ostreatus</span></em><span> cultivated on cassava peels and sawdust. The experiment was conducted at the Federal University of Technology, Owerri, Imo State Nigeria. The treatment for this investigation comprised different levels of wheat bran namely: T1 (C/N 17:0 in the control), T2 (C/N ratio 17:1), and T3 (C/N ratio 17:3). 2% lime was added to the substrate to stabilize the pH. The experiment was laid out in a completely randomized design (CRD) which was replicated three times. The mineral and proximate compositions were determined using standard procedures. The data generated were subjected to analysis of variance (ANOVA) at (p = 0.05). The result obtained from this investigation reviewed that the mineral composition before substrate inoculation was significantly higher than those obtained from the SMS which were in the range: of Na (0.10-0.17 mg/kg), Mg (0.25-0.40 mg/kg), Ash (1.56-2.65%), Ca (0.62-1.40 mg/kg), K (0.25-0.42 mg/kg), and P (0.11-0.44 mg/kg) while the proximate composition is in the range: dry matter (81.6-93.3%), N (0.18-0.31%), crude protein (CP) (1.13-1.94%), crude fiber (2.84-4.82%). This result revealed that significant quantities of the nutrients unlocked by </span><em><span>Pleurotus ostreatus</span></em><span> were assimilated into the mushroom fruit bodies. Therefore, </span><em><span>Pleurotus ostreatus</span></em><span> could be used to enrich cassava peels and sawdust substrates which can further be utilized in the formulation of livestock feeds. However, further studies are recommended especially in evaluating more nutritional indices of the substrate.</span></p>

Preliminary Study on Mini-Modus Device Equipped with a Bioreactor to Purify and Oxygenate a Synthetic Effluent

To explore the possibility of recovering a polluted anoxic environment characterized by an elevated organic load, a bench-scale novel technology, called the module for the decontamination of units of sediment (MODUS), was studied. The bench-scale apparatus is able to aerate an effluent by a sparger that uses an air flow. The apparatus was implemented with a bioreactor to biodegrade a synthetic effluent made by glucose, urea, and potassium acid phosphate; an apparatus that will be here referred to as the BIOmini-MODUS. To test its performance, seven series of biodegradation experiments were done, each series corresponding to one of the seven different selected air flows in the range 5–20 L min−1. The purpose was to determine the best operative conditions for the BIOmini-MODUS, especially in terms of energy efficiency. These were found by studying eight parameters deemed particularly crucial: (1) dissolved oxygen concentration of the synthetic effluent, (2) time required to complete the substrate biodegradation, (3) air pressure (head losses) of the pumped air, (4) power needed to pump the air, (5) total energy used during a single biodegradation experiment, (6) biodegradation efficiency, (7) biological oxygen demand BOD as a function of time, and (8) the maximum biodegradation velocity reached by each biodegradation experiment. All of them, except BOD, were a function of the air flow. The air flow resulted in being particularly important to optimize the performance of the BIOmini-MODUS in terms of biodegradation velocity and oxygen concentration at the apparatus exit, in conjunction with energy efficiency. This last one, which showed a sharp maximum for an air flow of 10 L min−1, was determined on the basis of the biodegradation rate. At low air flows, a high biodegradation rate resulted in being a good parameter to indicate high energy efficiency; while, on the other hand, a high oxygen concentration resulted in being a good parameter to determine a high biodegradation rate.

Predictive Biodegradation of Multiple Toxic Pollutants in Bioreactors Treating Real Wastewater using ANN and GP

Industrial wastewater contains eco-toxic organic pollutants such as phenol, cyanide and xylenol, which are usually the most common toxic compounds from steel industries and their high concentrations negatively affects biological treatments through substrate inhibition. Optimizing the biodegradation of multiple substrates found in wastewater such as phenol, xylenol and cyanide under Aerobic (in presence of oxygen), Anaerobic (in absence of oxygen) and Anoxic (in presence of nitrates) biotreatment systems has been done in this study. To predict the performance and design control systems to meet the environmental regulatory standards, the complex non-linear behavior presented in the biological treatment requires an accurate model. Herein, by using Artificial intelligence (ANN, GA and GP), the mathematical modelling of biological reactors operating under batch and continuous systems treating phenol, xylenol and cyanide were attempted. Mathematical modelling of biological systems is complex due to lack of process knowledge and multiple governing factors thereby significantly increasing the research trends using data based driven models. To correlate the biological non-linear relationship and to achieve the minimum error goal for pollutant removal with an acceptable R2 value of 0.847, 0.892, 0.937 in the anoxic system for phenol, cyanide and xylenol removal, the ANN and GA were designed. These models represent, analyse and reliably make predictions of complex biological systems helping in controlling and enhancing the performance of the wastewater treatment plant. From these results, the better pollutant removal was done by the anoxic system when compared to aerobic and anaerobic systems especially for phenol and cyanide removal.

Enhancing biogas production from livestock manure in solid-state anaerobic digestion by sorghum-vinegar residues

This study investigated the performance of sorghum vinegar residue to enhance methane production from livestock manures during solid-state anaerobic digestion. Sorghum vinegar residue was co-digested with cattle, sheep, and pig manure, respectively. Results show that co-digesting vinegar residue with livestock manures effectively diluted inhibitory substances (e.g. ammonium, sodium ion, and potassium ion) to alleviate the accumulation of volatile fatty acids and amend microbial composition to enhance digester stability and thus methane production by 10.1 – 58.2%. The highest increase was observed for cattle manure, possibly due to its low inhibitory substances to induce effective synergistic effects with vinegar residue in co-digestion. Modified Gompertz model well fitted the experimental methane yield and exhibited an increase in the maximum methane production rate of livestock manures by 35.2 –58.0% to corroborate their enhanced methanogenesis kinetics with the addition of vinegar residue. Further microbial analyses also indicated that co-digesting vinegar residue with livestock manures enriched hydrolytic bacteria (e.g. the genus vadinBC27_wastewater-sludge_group ), acetogenic bacteria (e.g. the genera Syntrophomonas and Petrimonas ) and aceticlastic methanogens (e.g. the genera Methanosarcina and Methanosaeta ) to promote substrate biodegradation and secure methane production. • Sorghum vinegar residue was co-digested with livestock manures at solid state. • Digester stability and methane production were enhanced in anaerobic co-digestion. • Modified Gompertz model corroborated enhanced methanogenesis kinetics in co-digestion. • Vinegar residue addition enriched functional microbes to sustain methane production.

Microbial interaction promote the degradation rate of organic matter in thermophilic period

Composting is an efficient, microbe-driven method for the biodegradation of solid organic substrates. In such a complex engineering ecosystem, microbial interaction is more important to function than relative abundance and alpha diversity. However, microbial interaction and its driving force in the composting process has been rarely reported. Thus, we combined network analysis and positive cohesion to analyze the relationship between cooperation among bacteria taxa and the degradation of organic matter in ten industrial-scale food waste composting piles. The results showed that although the complexity of network and microbial diversity were inhibited by high temperature, microbial cooperation was stimulated in the thermophilic period. The positive cohesion, which reflected the degree of microbial cooperation, tended to be positively correlated with the degradation rate of organic matter, functional genera, and genes associated with organic matter degradation. Thus, microbial cooperation was a key factor in the promotion of the degradation of organic matter. From the insight microbial community, Thermobifida was the genera with high abundance, high occurrence frequency, and high contributions to microbial structure. Additionally, it was not only highly associated with the degree of cooperation but was also highly linked with the functional genera in the composting, implying that it might play an important role in regulating cooperation to promote the functional genera. Our research provides a deep understanding of the interaction among bacteria taxa during the composting process. Focusing on the abundance of Thermobifida might be an efficient way to improve composting quality by enhancing the cooperation of microbes.

Pretreatment methods to enhance solubilization and anaerobic biodegradability of lignocellulosic biomass (wheat straw): Progress and challenges

Agro-waste (wheat straw) is considered most effective (heating value 16 MJ/kg) for energy recovery through anaerobic digestion (AD). However, the complex lignocellulosic structure obstructs their biotransformation and is a rate-limiting step of the AD process. The pretreatment of agro-waste could remove the physical and chemical barriers and accelerate the downstream AD process. The physical pretreatments (mechanical, thermal, sonication) improve the biodegradation kinetics of wheat straw (>50% and can reach up to 92%) but require more energy. High external or internal heat sources may lead to the formation of recalcitrant compounds, i.e., furan derivatives from cellulose. Chemical pretreatment is effective for rapid reaction rate but is uneconomical due to high chemical cost. It may produce toxic intermediary products, and hinder microbial activities in AD. The ionic liquids are emerging chemical pretreatment and are renewable, recoverable, difficult to oxidize, and bio-based salts. The chemical pretreatment induces cellulose loss up to 59% and lignin up to 69%, while the bio-degradability is as high as 88.3%. In biological pretreatment, bacterial pretreatment is superior to fungal and algal pretreatments, and also helps in the substrate bio-degradation during AD. The FTIR, TGA-DTG, XRD, and SEM technologies can validate the efficiency of the pretreatment method, such as modifications in lignocellulosic functional groups, mass loss, crystal feature, surface topography, and morphology of lignocellulosic biomass. Different mathematical models, especially the modified Gompertz model, are employed to facilitate the insight into the AD research. Energy use and balance are necessary for the pretreatment process to figure out the real synergic effects rather than aiming to achieve enhanced methane production.

Modified fractional-order model for biomass degradation in an up-flow anaerobic sludge blanket reactor at Zenein Wastewater Treatment Plant.

This paper presents a modified fractional-order model (FOM) for microorganism stimulation in an up-flow anaerobic sludge blanket (UASB) reactor treating low-strength wastewater. This study aimed to examine the famine period of methanogens due to biomass accumulation in the UASB reactor over long time periods at a constant organic loading rate (OLR). This modified model can investigate the substrate biodegradation in a UASB reactor while considering substrate diffusion into biological granules during the feast and famine periods of methanogens. The Grünwald-Letnikov numerical technique was used to indicate the effect of biomass degradation on the biogas production rate and substrate biodegradation in a UASB reactor installed at Zenein Wastewater Treatment Plant (WWTP) in Giza, Egypt. Several fractional orders were applied in the dynamic model at biomass concentrations of [Formula: see text] and [Formula: see text] in the reactor bed and blanket zones, respectively. An OLR of [Formula: see text] using the calibrated kinetic parameters at [Formula: see text] was applied to comply with the experimental outcomes. The simulation results indicate that the removal efficiency of chemical oxygen demand (COD) was maintained at approximately [Formula: see text], whereas the biogas production rate declined from [Formula: see text] in the reactor bed zone due to a decline in food to microorganism (F/M) ratio from [Formula: see text] during the sludge retention time (SRT) in the UASB reactor.

Fly ash from coal combustion as improver of anaerobic digestion: A review

The increasing production of fly ash from coal combustion has become a problem due to the environmental risks involved in its disposal. These wastes have a porous structure and contain several transition metal oxides that are active components of many catalytic systems. This document presents the possibility of using fly ash as an additive to improve anaerobic digestion processes. To this end, the effect of fly ash on methane production and the biodegradation of different substrates is reviewed. Moreover, this review gives emphasis on possible mechanisms responsible for improving anaerobic digestion by adding fly ash. In this context, the importance of trace elements for methanogenic archaea, as well as the techniques studied to determine the availability of trace elements for microorganisms are addressed. The importance of the metallic oxides contained in the fly ash on the direct interspecies electron transfer and the possibility that the fly ash can act as a support for the formation of biofilms is reviewed. In addition, in this review, the possible effects that can occur in the digestate by adding metals in the anaerobic process are presented, and the mathematical models that incorporate the effect of fly ash on anaerobic digestion. Finally, this manuscript discusses the limitations on the use of fly ash on an industrial scale and the outlook for its continued use.