Search

To determine the evolution of microbial community and microbial shift under anaerobic processes, this study investigates the use of denaturing gradient gel electrophoresis (DGGE). In the DGGE, short- and medium-sized DNA fragments are separated based on their melting characteristics, and this technique is used in this study to understand the dominant bacterial community in mesophilic and thermophilic anaerobic digestion processes. Dairy manure is known for emitting greenhouse gases (GHGs) such as methane, and GHG emissions from manure is a biological process that is largely dependent on the manure conditions, microbial community presence in manure, and their functions. Additional efforts are needed to understand the GHG emissions from manure and develop control strategies to minimize the biological GHG emissions from manure. To study the microbial shift during anaerobic processes responsible for GHG emission, we conducted a series of manure anaerobic digestion experiments, and these experiments were conducted in lab-scale reactors operated under various temperature conditions (28 °C, 36 °C, 44 °C, and 52 °C). We examined the third variable region (V3) of the 16S rRNA gene fingerprints of bacterial presence in anaerobic environment by PCR amplification and DGGE separation. Results showed that bacterial community was affected by the temperature conditions and anaerobic incubation time of manure. The microbial community structure of the original manure changed over time during anaerobic processes, and the community composition changed substantially with the temperature of the anaerobic process. At Day 0, the sequence similarity confirmed that most of the bacteria were similar (>95%) to Acinetobacter sp. (strain: ATCC 31012), a Gram-negative bacteria, regardless of temperature conditions. At day 7, the sequence similarity of DNA fragments of reactors (28 °C) was similar to Acinetobacter sp.; however, the DNA fragments of effluent of reactors at 44 °C and 52 °C were similar to Coprothermobacter proteolyticus (strain: DSM 5265) (similarity: 97%) and Tepidimicrobium ferriphilum (strain: DSM 16624) (similarity: 100%), respectively. At day 60, the analysis showed that DNA fragments of effluent of 28 °C reactor were similar to Galbibacter mesophilus (strain: NBRC 10162) (similarity: 87%), and DNA fragments of effluent of 36 °C reactors were similar to Syntrophomonas curvata (strain: GB8-1) (similarity: 91%). In reactors with a relatively higher temperature, the DNA fragments of effluent of 44 °C reactor were similar to Dielma fastidiosa (strain: JC13) (similarity: 86%), and the DNA fragments of effluent of 52 °C reactor were similar to Coprothermobacter proteolyticus (strain: DSM 5265) (similarity: 99%). To authors knowledge, this is one of the few studies where DGGE-based approach is utilized to study and compare microbial shifts under mesophilic and thermophilic anaerobic digestions of manure simultaneously. While there were challenges in identifying the bands during gradient gel electrophoresis, the joint use of DGGE and sequencing tool can be potentially useful for illustrating and comparing the change in microbial community structure under complex anaerobic processes and functionality of microbes for understanding the consequential GHG emissions from manure.

In colder regions, relatively low temperatures results in low microbial activity and low biogas production in anaerobic digestion. This study investigated if microbial electrosynthesis system (MES) can enhance biogas production from pig manure wastewater under sub-psychrophilic conditions (20 °C). Results showed that the applied voltage of MES (0.4 V and 0.8 V) significantly increased the biogas production and COD removal rate. Biogas production and COD removal rate increased most when the voltage reached 0.8 V (34.77 %, 26.67 %), and decreased when the voltage was 1.2 V. Low voltage (≤ 0.8 V) did not significantly alter the microbial structure, but higher voltage (1.2 V) resulted in a significant decrease in Clostridium and Methanosarcina. Coenzyme F420, NADH, as indicators for methanogenic efficiency, showed the highest fluorescence intensity at 0.8 V and decreased at 1.2 V. Results indicated that the improvement of gas production was mainly due to the improvement of key enzymes rather than the shift of microbial structure. The information provided will be useful to improve the efficiency of biogas production. [Display omitted] • The optimal voltage was explored in 5 L MES under sub-psychrophilic condition. • Optimized applied voltage on MES was 0.8 V. • Applied voltage at 1.2 V led to lower concentration of F420 and NADH. • Clostridium and Methonasarcina were significantly reduced at 1.2 V. [ABSTRACT FROM AUTHOR]

Anaerobic digestion has been defined as a competitive approach to facilitate the recycling of corn stalks. However, few studies have focused on the role of direct interspecies electron transfer (DIET) pathway in the acidification stage under the addition of different particle sizes of zero-valent iron (ZVI). In this study, three types of ZVI, namely iron filings, iron powder and nanoscale iron, were investigated, respectively, to enhance its high-value conversion. Variations in volatile fatty acids (VFAs) and methane (CH 4) production associated with the underlying mechanisms were emphatically determined. Results indicated that the addition of ZVI could increase the concentration of VFAs, with the most outstanding performance observed with the use of nanoscale iron. Importantly, the conversion of propionic acid to acetic acid was driven by adding ZVI with no between-group differences in acidizing phase. Conversely, the substrate was more fully utilized when supplied with iron powder compared with other groups in methanogenic phase, thereby displaying the maximum CH 4 yield with a value of 263.1 mL/(g total solids (TS)). However, adding nanoscale iron could signally shorten the digestion time (T 80), saving 7 days in comparison to the group of iron powder. [Display omitted] [ABSTRACT FROM AUTHOR]

The anaerobic digestion of the organic fraction of municipal solid waste (OFMSW) has shown to be a viable alternative since it allows energy recovery in the form of methane and generates a residue (digestate) that can be applied effectively as a soil improver or fertiliser. The potential for methane production and the digestates' characteristics depend on the substrate characteristics and the process variables such as temperature, solids retention time, and organic load. This study dealt with OFMSW anaerobic digestion under different organic loading rates and temperatures and the characteristics of the resulting digestates. Three semi-continuous reactors were operated at 20, 35, and 55°C and fed daily with ground, fresh OFMSW from Mexico City. The inoculum was temperature-adapted UASB granular sludge. The main results indicate that the anaerobic digestion was adequate, as the pH values were slightly alkaline, which is sufficient for methanization, and the alkalinity was not a limiting factor. Potassium and PO4-P increased with the organic load, and Kjeldahl nitrogen decreased. At 20°C, total organic carbon (TOC) increased substantially with the organic load; at 35°C, it remained without significant changes; and at 55°C, TOC slightly decreased with the organic load. The C/N ratio changed accordingly to TOC variations. At 20°C, the residual biogas potential increased with the organic load; at 35 and 55°C, it decreased with increasing organic load; the residual biogas potential increased with residual fatty acids concentrations. To comply with international standards for agricultural use, the digestates need only dewatering and supplementing with PO4-P. [ABSTRACT FROM AUTHOR]

A high rate upflow anaerobic polyfoam‐based bioreactor (UAPB) was developed for lab‐scale in‐situ biogas upgrading by H2 injection. The reactor, with a volume of 440 mL, was fed with synthetic wastewater at an organic loading rate (OLR) of 3.5 g COD/L·day and a hydraulic retention time (HRT) of 7.33 h. The use of a porous diffuser, alongside high gas recirculation, led to a higher H2 liquid mass transfer, and subsequently to a better uptake for high CH4 content of 56% (starting from 26%). Our attempts to optimize both operational parameters (H2 flow rate and gas recirculation ratio, which is the total flow rate of recirculated gas over the total outlet of gas flow rate) were not initially successful, however, at a very high recirculation ratio (32) and flow rate (54 mL/h), a significant improvement of the hydrogen consumption was achieved. These operational conditions have in turn driven the methanogenic community toward the dominance of Methanosaetaceae, which out‐competed Methanosarcinaceae. Nevertheless, highly stable methane production rates of 1.4–1.9 L CH4/Lreactor.day were observed despite the methanogenic turnover. During the different applied operational conditions, the bacterial community was especially impacted, resulting in substantial shifts of taxonomic groups. Notably, Aeromonadaceae was the only bacterial group positively correlated with increasing hydrogen consumption rates. The capacity of Aeromonadaceae to extracellularly donate electrons suggests that direct interspecies electron transfer (DIET) enhanced biogas upgrading. Overall, the proposed innovative biological in‐situ biogas upgrading technology using the UAPB configuration shows promising results for stable, simple, and effective biological biogas upgrading. [ABSTRACT FROM AUTHOR]

The increasing volume of textile waste in landfills and incineration poses severe environmental challenges. Waste valorisation of textile waste via anaerobic digestion (AD) is preferable, as it offers economic and environmental benefits, but it is hindered by textile complexity, necessitating effective pretreatment technologies to improve biogas production. This study aims to evaluate various pretreatment technologies for biogas production from textile fibres via AD. A weighted‐scoring analysis (WSA) assessed pretreatment methods based on technical, economic, environmental and operational criteria. Hydrothermal pretreatment emerged as the most technically effective method, scoring 140 owing to its substantial methane enhancement. Economically, shredding was the most viable option, scoring 125, as a consequence of low capital and O&M cost. Environmentally, hydrothermal and deep eutectic solvent (DES) pretreatments were top performers with 100 points owing to low environmental impact and positive heat reactions. In a case study conducted in the Auckland region, the potential environmental impact (PEI) obtained from hydrothermal and DES were 169 and 92 per year, respectively, resulting in minimal environmental impact. Operationally, ultrasonic and biological pretreatments scored highest owing to their ease of operation, and minimal health and safety requirements. Overall, hydrothermal pretreatment achieved the highest WSA score of 340, reflecting its balanced performance across all criteria. Hydrothermal pretreatment is the most promising technology for enhancing biogas production from textile waste. Its technical efficiency, economic feasibility and environmental benefits regarding the WSA score make it suitable for upscaling and providing a viable solution for managing textile waste in the AD plant. © 2024 The Author(s). Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

The USA has committed to cutting its emissions of methane, an extremely potent greenhouse gas, by at least 30% by 2030 (‘30 × 30’). This is part of the Global Methane Pledge, signed by 155 countries, to keep global warming within 1.5 °C and thereby to forestall the disastrous effects of ‘runaway climate change’. It will be a major challenge for the USA to reach 30 × 30 and there is no consensus on how to do so. This paper provides a concrete, data‐driven roadmap to indicate how to reach 30 × 30 feasibly, focusing on two enormous sources of methane emissions: organic waste and oil and gas production. It calculates that building approximately 4700 anaerobic digesters (ADs) to process food waste and animal manure would cost about $74.2 billion in capital expenditure (capex) and cut 13.6% of total US methane emissions per year. On average, each project would take roughly 2–6 years to build. Of the various methane mitigation measures analyzed in the oil and gas sectors, the most impactful would be full compliance with the US Environmental Protection Agency's (EPA's) revised New Source Performance Standards (NSPS) for oil and gas production by 2029. This would cut 17.5% of total US methane emissions annually, at a cumulative capex of $20.7 billion from 2024 to 2029. Together, the 13.6% cut from food waste and manure ADs and the 17.5% cut from full NSPS compliance would amount to a 31.5% reduction, exceeding the 30 × 30 goal. Greater clarity from the federal government on funding eligibility and additional incentives would accelerate the buildout of ADs. [ABSTRACT FROM AUTHOR]

Expanding green areas in cities results in growth in green waste generation. This study presents the findings of an investigation into green waste from selective collection in a large Central European city (Warsaw, Poland), which can be identified as a valuable biomass resource. The research objective was to identify the properties of garden waste from single-family housing to determine valorization opportunities, emphasizing the utilization of GW as a source of energy. The research yielded several findings, including a notable degree of variability in fuel properties, including moisture content (CV = 30%), lower heating value (CV = 14.3%), and ash content (CV = 62.7/56.2%). The moisture content suggests composting, while the fertilizing properties indicate suitability for anaerobic digestion. The instability of the fuel properties, coupled with the elevated levels of chlorine, sulfur, and moisture, constrains the use of garden waste in thermal processes and alternative fuel production. Pyrolysis could be a viable approach for green waste feedstock, offering value-added products depending on the processing conditions and pre-treatment. Nevertheless, implementing a selective collection system is a critical condition for the optimal utilization of bio-waste, facilitating the quality and property control of green and food waste. This is essential for their effective processing, including energy recovery, thereby contributing to the efficient valorization of biomass. [ABSTRACT FROM AUTHOR]

The study aimed to compare the development of an artificial neural network (ANN) and multilinear regression (MLR) model used to predict the performance of biogas in a batch-mode underground fixed dome biogas digester. In this study, 50 experimental datasets were used to assess the rate of biogas production with developed ANN and MLR models. The six variables, including solar irradiance, relative humidity, slurry temperature, biogas temperature, pH, and ambient temperature, were selected as the input parameters or predictors of the model. Therefore, the developed ANN and MLR models were used to describe the rate of biogas yield. The study found that the determination coefficient (R2) and root mean square error (RMSE) for ANN and MLR were 0.999/0.968 and 8.33 × 10−6/1.84 × 10−4, respectively. Both models were significant because of their high correlation between measured and predicted values of the biogas yield. However, the ANN performs better because of the smaller RMSE and higher R2 derived compared to the corresponding values of the MLR. The study proved that both the ANN and MLR can accurately predict the rate of biogas production but with better predictions obtained from ANN. [ABSTRACT FROM AUTHOR]

The steel industry is one of the hard-to-abate sectors for decarbonization, and direct electrification is not possible or economically infeasible. This study investigates the application of the Water-Energy-Carbon nexus in the steel industry through a multi-generation plant, addressing the industry's demands for water, energy, and alternative fuel. The proposed multi-generation plant consists of parabolic trough solar collectors, an organic Rankine cycle, urban wastewater treatment, carbon capture, anaerobic digestion combined with heat and power, a proton exchange membrane electrolyzer, and a steelmaking plant. Thermodynamic and exergoeconomic analyses are conducted to investigate the system's efficiency and economic performance. A sensitivity analysis is conducted to identify the optimal links between nexus resources, followed by a multi-dimensional evaluation and multi-objective optimization. The results showed that under base conditions, the plant can annually produce 900 ktons of steel, 105 GWh of net power, 430.1 tons of water, and 517 tons of hydrogen, while preventing 34.7 ktons of CO 2 emissions. The exergy efficiency and unit exergy cost of the products are 46.1% and 57.8 $/GJ, respectively. Under optimized conditions, the plant achieves a maximum net annual power output of 160 GWh, an exergy efficiency of 46.9%, and a minimum unit exergy cost of 51.4 $/GJ. [Display omitted] • Multi-generation plant for energy, water, and fuel for steel industry. • System integrates solar, wastewater treatment, and carbon capture. • Thermodynamic and exergoeconomic analyses assess efficiency and costs. • Optimization achieves 46.9% exergy efficiency and 51.4 $/GJ unit exergy cost. • Plant annually produces 900 kt steel, 105 GWh power, 430.1 t water, 517 t hydrogen. [ABSTRACT FROM AUTHOR]

Biogas is a type of biomass energy source, primarily composed of methane and carbon dioxide. It is generated through the controlled anaerobic digestion of manure or other organic residues. As a cleaner alternative to conventional fuels, fully purified biogas can produce approximately 36.68 MJ/m3 of en.ergy. As the separation of CO2/CH4 in biogas became an important part of the energy industry, we used membrane separation technique to study its separation methods. At first, 3,3′‐dihydroxy‐4,4′‐diamino‐biphenyl (HAB) and 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride (6FDA) were polymerized by open‐loop as polyamide acid macromolecules. Then it was divided into two research routes. One was condensation to polyimide (PI) membranes directly and then thermal rearrangement (TR); the other one was ionic liquid (IL) added before condensation and thermal rearrangement. Through adjusting the thermal rearrangement temperature, different modified polyimide membranes were obtained and tested their separation performance of CO2/CH4. For the result of the test, the best one, membrane HAB‐6FDA‐IL‐TR400, could reach a good separation performance as PCO2 = 403.80 Barrer, αCO2/CH4 = 82.35. It was beyond the Robeson's 2019 upper limit and proved that the modification by IL and thermal rearrangement was benefit for the separation performance of polyimide membranes. [ABSTRACT FROM AUTHOR]

Anaerobic digestion (AD) is one of the most significant processes for treating fecal sludge. However, a substantial amount of microplastics (MPs) have been identified in septic tanks, and it remains unclear whether they impact the resource treatment of feces. To investigate this, polyethylene terephthalate (PET) was used as an indicator of MPs to study their effect on the anaerobic digestion of fecal sludge (FS). Two digestion systems were developed: FS mono-digestion and FS co-digestion with anaerobic granular sludge. The results indicated that the effects of PET varied between the two systems. PET inhibited volatile fatty acid synthesis in both systems, but the inhibition period differed. During mono-digestion, PET slightly increased gas and methane production, in contrast to the co-digestion system, where PET reduced methane production by 75.18%. Furthermore, in the mono-digestion system, PET increased soluble chemical oxygen demand and ammonia nitrogen concentrations while blocking phosphorus release, whereas the co-digestion system showed the opposite effects. Ultimately, the choice of digestion method is crucial for the resource utilization of septic tank sludge, and the impact of MPs on AD cannot be ignored. [ABSTRACT FROM AUTHOR]

Sludge disintegration is an environmental and industrial challenge that requires intensive research and technological development. Sludge has a complex structure with a high yield of various chemical and biological compounds. Anaerobic digestion is the most commonly used process for sludge disintegration to produce biogas, detoxify sludge, and generate biosolids that can be used in agriculture. Biological cell lysis is the rate‐limiting cell lysis. This review discusses the application of sonolysis as a sludge pretreatment for enhanced anaerobic digestion via three combined processes: thermal destruction, hydrochemical shear forces, and radical oxidation. The mechanistic pathways of sono‐pretreatment to enhance biogas, sludge‐enhanced dewatering, activation of filamentous bacteria, oxidation of organic pollutants, release of heavy metals, reduction of bulking and foaming sludge, and boosting ammonia‐oxidizing bacterial activity are discussed in this review. This article also discusses the use of ultrasound in sludge disintegration, highlighting its potential in conjunction with Fenton and cation‐binding agents, and reviews common large‐scale sonoreactors available on the market.. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine the effect of sorption of Basic Red 46 (BR46) dye by lignocellulosic biomass on the susceptibility of the sorbed waste to anaerobic decomposition by anaerobic digestion. The research material used in the experiment consisted of two types of biomass: stalks with leaves and inflorescences after mowing Canadian goldenrod (Solidago canadensis L.) (GB), and rapeseed hulls (RHs) after oil pressing. During the anaerobic decomposition of RHs, 732.30 NmL/gVS and 646.63 NmL/gVS of methane were obtained from the non-sorbed substrate and the plant material after dye sorption, respectively. Similarly, in the variants using Canadian goldenrod, the production was 220.70 NmL/gVS and 183.20 NmL/gVS. The GB sorbent sorbed 34% more BR46 dye than the RH sorbent, which is likely to have resulted in the accumulation of VFA and contributed to the partial inhibition of methane production. In light of the obtained results and the literature data, it is concluded that there is a possibility of effective use of dye sorption waste for methane production. [ABSTRACT FROM AUTHOR]

[Display omitted] • Machine learning model could predict methane yield of pretreated LW accurately. • Digestion time, pretreatment agent and pretreatment agent were crucial factors. • NaOH, KOH and AHP pretreatments were suitable for LW with low lignin content. • LW with high lignin content preferred AHP pretreatment. Chemical pretreatment is a common method to enhance the cumulative methane yield (CMY) of lignocellulosic waste (LW) but its effectiveness is subject to various factors, and accurate estimation of methane production of pretreated LW remains a challenge. Here, based on 254 LW samples, a machine learning (ML) model to predict the methane production performance of pretreated feedstock was constructed using two automated ML platforms (tree-based pipeline optimization tool and neural network intelligence). Furthermore, the interactive effects of pretreatment conditions, feedstock properties, and digestion conditions on methane production of pretreated LW were studied through model interpretability analysis. The optimal ML model performed well on the validation set, and the digestion time, pretreatment agent, and lignin content (LC) were found to be key factors affecting the methane production of pretreated LW. If the LC in the raw LW was lower than 15%, the maximum CMY might be achieved using the NaOH, KOH, and alkaline hydrogen peroxide (AHP) with concentrations of 3.8%, 4.4%, and 4.5%, respectively. On the other hand, if LC was higher than 15%, only high concentrations of AHP exceeding 4% could significantly increase methane production. This study provides valuable guidance for optimizing pretreatment process, comparing different chemical pretreatment approaches, and regulating the operation of large-scale biogas plants. [ABSTRACT FROM AUTHOR]

This study evaluated the effectiveness of using iron (Fe) powder and ferrous chloride (FeCl2) to decrease hydrogen sulfide (H2S) concentration ([ H2S ]) from biogas production by anaerobic digestion (AD) of primary sludge, and to decrease phosphate (PO4-P) concentration ([ PO4-P ]) in the sludge. [ H2S ] and [ PO4-P ] removal increased as doses of Fe powder and FeCl2 increased to a certain point. Optimal supplementation was 5 g/L for Fe powder (H2S reduction=98% , PO4-P removal=95%) and 0.5 g/L for FeCl2 (H2S reduction=98% , PO4-P removal=97%). Appropriate dosage of Fe powder or FeCl2 can control [ H2S ] in biogas and decrease [ PO4-P ] in AD effluent, but excessive dosage can inhibit the digestion. The biogas production and methane content were higher with Fe powder compared with FeCl2 , but neither treatment had a significant effect on methane yield. The measured biogas production was accurately captured by the first-order kinetic model, as evidenced by a strong fit with high R2 values (0.957–0.980), and the deviations between the measured and predicted biogas production using the first-order kinetic model were <10%. [ABSTRACT FROM AUTHOR]

Palm oil mill effluent (POME), wastewater generated from palm oil production, is known for its extremely high chemical oxygen demand and brownish color. Anaerobic digestion is the primary treatment method for POME in the palm oil industry; however, anaerobically treated POME has high concentrations of residual contaminants and color intensity. This study proposes an approach to treat anaerobically-treated POME in recycled water for industrial applications by integrating preliminary organic precipitation, electrocoagulation, and electrooxidation (EO). The EO process was optimized in terms of the current density, electrolysis time, electrode arrangement, and feed flow rate. At a current density of 60 mA/cm2 and an electrolysis time of 9 min, the EO process with a graphite anode and stainless-steel cathode in the monopolar electrode configuration reduced the phenolic concentration and color in the preliminary-treated POME from 8.95 mg/L and 317.19 ADMI to 0.25 mg/L and 26.10 ADMI, respectively. Additionally, the EO process exhibited a 92.26% efficiency in lowering the ammonium-nitrogen content. [ABSTRACT FROM AUTHOR]

Textile waste is becoming among the most polluting waste in the world, discarded mostly in landfills. Valorizing textile waste via anaerobic digestion (AD) helps conserve resources, reduce environmental impact, and foster a circular economy. Although several reviews have discussed textile waste AD, there is a lack of detailed understanding of the challenges encountered during textile waste AD. Therefore, the goal of this review is to focus on challenges encountered and possible solutions for those challenges for biogas and fertilizer conversion via AD. Potential strategies include chemical, biological, and thermal pretreatments that significantly increase the digestion process. Co‐digestion of natural textile waste, cotton, and wool with carbon and nitrogen‐rich substrates improves AD efficiency by twofold. Moreover, separating polyester from polycotton and textile dye removal via solvent and advanced oxidation processes significantly increases methane yield compared with untreated textile waste. This review can aid in analyzing suitable methods to optimize the biogas production of textile waste via AD. [ABSTRACT FROM AUTHOR]

Natural habitats in littoral salt marshes and desert salt marshes along the coastline of the Red Sea are inhabited by several halophytes, which tolerate salinity stress in these areas. Two distinct halophytes inhabiting the Red Sea coast, Limonium axillare and Nitraria retusa, were studied for their physiological adaptations and energy sources. Results revealed the accumulation of the most abundant soil salts in their tissues. The soils in the study area recorded high concentrations of Na+ and Cl- compared with other ions such as Ca2+, Mg2+, and K+. To combat this stress, the two species absorb salts to adjust the osmotic potential and raise the concentrations of soluble organic compounds - such as proline, soluble sugars, and nitrogen components - in their leaves. In anaerobic digestion, both species yield many organic components that might act as a source to produce biogas. L. axillare produced more biogas 277.58 ml g-1 TS (361.23 ml g-1 VS) compared with N. retusa which produced 204.2 ml g-1 TS (309.4 ml g-1 VS). The presence of soluble organic solutes represents easily breakable molecules in anaerobic digestion. Therefore, L. axillare produced more biogas with more soluble carbohydrates (22.15 mg g-1 dry wt), proline (13.47 mg g-1 dry wt), and soluble protein (33.06 mg g-1 dry wt) compared with N. retusa which contains less soluble carbohydrates (18.53 ml g-1 dry wt), proline (13.64 mg g-1 dry wt), and soluble protein (20.04 mg g-1 dry wt). [ABSTRACT FROM AUTHOR]

Fungal pre-treatment using Pleurotus ostreatus (PO) was carried out on individual and combinations of agro-waste wheat straw (WS), rice straw (RS), and pearl millet straw (PMS) with the addition of biochar (5%,7.5% and 10%) to reduce the pre-treatment duration. Further remaining substrate known as spent mushroom substrate (SMS) was used in anaerobic digestor (AD) for estimation enhanced biomethane yield. Equal ratios of RS + WS, WS + PMS, PMS + RS, and RS + PMS + WS and biochar addition were taken for enhancing pre-treatment, PO growth and AD process. The extent of pre-treatment was recorded with the maximum lignin removal of 40.4% for RS + PMS + WS as compared to untreated counterparts and 0.5%, 2.2%, and 3.3% times more lignin removal from individual PMS, RS, and WS respectively. Addition of biochar to the substrates reduced the total pre-treatment duration by days as compared to the non-biochar substrates. Biological efficiency (BE) used for the analysis of mushroom growth varied from 51–92%. Further, the average bio-methane yield was 187 ml/gVS for SMS of PMS + WS + RS with 10% biochar indicating an increment of 83.33% from untreated SMS of PMS + WS + RS. This, higher biomethane yield was 9.35%, 22.22% and 57.14% times higher than individual SMS of PMS, RS, and WS respectively. The current study shows that biochar not only enhances the bio-methane yield but also reduces the biological pre-treatment duration and removes the dependency on one lignocellulosic biomass for energy (bio-methane) and food (mushroom) production. [ABSTRACT FROM AUTHOR]

Global waste management challenges demand innovative and multi-functional solutions. The Nordic Biogas Model (NBM) based on anaerobic digestion of organic waste and valorization of its outputs provides several benefits beyond waste treatment such as energy recovery, nutrient recycling and climate impact mitigation. Despite these benefits, its international adoption remains limited, revealing an implementation gap. One way to address this gap is to adapt technology and knowledge from the provider to each specific context. This involves the embedding of the technology into the local context and the development of conditions such as formal and informal institutions over time. Based on decade-long interactions with Nordic companies and municipal decision-makers, we highlight the importance of communication between the technology provider and potential adopter, to ensure that the diverse sustainability benefits of NBM are acknowledged. Furthermore, most provider companies can benefit from a systematic guideline that supports early-stage decision-making as an essential component of the adaptation and implementation of the NBM in diverse international contexts. In this article, we offer suggestions for both: (1) how to better communicate the sustainability benefits of the NBM, and (2) how to assess the risk and opportunities of entering new markets at the early stages of decision-making. [ABSTRACT FROM AUTHOR]

Food waste (FW) biotransformation into bioenergy has garnered a lot of scientific interest as a way to address the energy crisis and trash disposal issues. FW is converted into biogas, a gaseous combination of biomethane and carbon dioxide. In order to valorize FW, anaerobic digestion (AD) with combined pretreatment (hydrothermal (HT) and ultrasonic (US)) is used as a potential method. Three digesters were investigated: the control (unpretreated), HT(121°C) + US, and HT(134°C) + US, respectively. Based on changes in the combined pretreatment conditions, the paper assessed the methane productivity. Furthermore, kinetic modeling was evaluated with six kinetic models. The results show that the HT pretreatment at 121°C combined with US improves the volatile solid (VS) removal to 73 ± 5% and the methane yield to 529.7 ± 11 NmL/gVS. Both the Transference model and the first order have the greatest fits in terms of R2, and they also have the best fits in terms of relative errors, and methane production rate, respectively. The combined pretreatment has a positive impact on increasing methane yield as well as stabilizing the anaerobic digestion process. [ABSTRACT FROM AUTHOR]

Hydrothermal carbonization (HTC) emerges as a promising avenue for converting food waste into valuable resources while addressing environmental concerns. This study investigated the optimization of HTC parameters, utilizing landfill leachate as a sustainable moisture source and exploring methane recovery from process water. Employing the response surface methodology (RSM) and artificial neural networks (ANN), the influence of key process variables on HTC efficiency was meticulously analyzed. Notably, the superior predictive capability of ANN over RSM was demonstrated, with a lower mean-squared error and a higher correlation coefficient. The identified optimal HTC conditions were 193°C for 175 min at a solid/liquid ratio of 0.2; under these conditions, RSM and ANN predicted mass yields of 66.37 ± 1.15% and 65.68 ± 0.11%, respectively. Furthermore, under these conditions, process water exhibited a remarkable biomethane production rate of approximately 283.11 ± 13.5 mL/g COD, fitting well with the modified Gompertz model. This study advances HTC optimization strategies and underscores the potential of integrating landfill leachate and methane recovery into food waste valorization processes, thereby paving the way for sustainable resource management practices. [ABSTRACT FROM AUTHOR]

Pretreatment is compulsory to obtain the greatest possible biofuel production from lignocellulosic biomass. Among the many different pretreatment methods, enzymatic and ultrasonic pretreatments are attracting attention as environmentally friendly methods. In this framework, this study aims to optimize enzymatic and ultrasonic pretreatment to achieve high methane production by anaerobic digestion of lignocellulosic biomass consisting of agricultural residues. The optimization studies selected independent variables such as cellulase and β-glycosidase doses for enzymatic pretreatment and ultrasound power, reaction time, and solid content for ultrasonic pretreatment. The optimum conditions for enzymatic pretreatment were determined as 32.68FPU/gTS cellulase and 14.56 IU/gTS β-glucosidase concentrations to achieve a 60.15% increase in methane production. On the other hand, an 80.04% increase in methane production was obtained in the ultrasonic pretreatment under optimum conditions determined as 20 W ultrasound power, 60-min reaction time, and 5.46% solids content. The decrease in methane production by increasing the cellulose concentration in enzymatic pretreatment and by increasing the ultrasound power in ultrasonic pretreatment shows the importance of process optimization to achieve methane production. The theoretical energy productions were calculated and then compared with other pretreatment methods and the theoretical direct combustion energy. Since 90% energy recovery with ultrasonic pretreatment compared to direct combustion of lignocellulosic biomass was achieved, it is recommended to determine the effects of ultrasound in the pretreatment of other lignocellulosic biomass types. Thus, it will be possible to obtain energy from lignocellulosic waste in a much more environmentally friendly way compared to direct combustion. [ABSTRACT FROM AUTHOR]

The coupling between anaerobic digestion and hydrothermal carbonization (HTC) is a promising alternative for sustainable energy production. This study presents a dynamic model tailored for a lab-scale anaerobic digester operating on HTC products, specifically hydrochar and HTC liquor derived from sewage and agro-industrial digestate. Leveraging a modified version of the Anaerobic Model 2 (AM2), our simplified model of four states integrates pH and biomass decay rates into biomass kinetics. Simulation results of the mode were compared with experimental data collected over 164 days from the digester. The obtained results have proven the ability of the proposed model to predict the trend of the biogas production as well as important measured outputs of the bioreactor. The developed model could be used to control and optimize the performance of the digester, which provides potential for bioenergy production from waste streams such as digestate and digestate treated through the HTC process. [ABSTRACT FROM AUTHOR]

This case study aimed to isolate and identify methanogenic bacteria from landfill soil, mud, and leachate samples to assess their role in anaerobic digestion and biogas production. Anaerobic digestion involves the breakdown of organic matter by a diverse group of bacteria under oxygen-free conditions, resulting in the production of methane and carbon dioxide. The collected samples from the landfill were cultured in a modified mineral salt medium (MSM). Microscopic observations revealed distinct coccus and bacillus morphologies of the isolated methanogenic bacteria. Gas production experiments and substrate utilization studies identified two types of methanogens. Methanosarcina sp., which utilized acetate and methanol for methane production, and Methanobacterium sp., utilizing hydrogen and carbon dioxide, as well as acetate. Scanning electron microscope (SEM) analysis confirmed the different morphotypes of the isolated methanogens. The study findings demonstrated the presence of diverse methanogens in the landfill environment, contributing to anaerobic digestion and biogas production. [ABSTRACT FROM AUTHOR]

Background: The integration of anaerobic digestion into bio-based industries can create synergies that help render anaerobic digestion self-sustaining. Two-stage digesters with separate acidification stages allow for the production of green hydrogen and short-chain fatty acids, which are promising industrial products. Heat shocks can be used to foster the production of these products, the practical applicability of this treatment is often not addressed sufficiently, and the presented work therefore aims to close this gap. Methods: Batch experiments were conducted in 5 L double-walled tank reactors incubated at 37 °C. Short microwave heat shocks of 25 min duration and exposure times of 5–10 min at 80 °C were performed and compared to oven heat shocks. Pairwise experimental group differences for gas production and chemical parameters were determined using ANOVA and post–hoc tests. High-throughput 16S rRNA gene amplicon sequencing was performed to analyse taxonomic profiles. Results: After heat–shocking the entire seed sludge, the highest hydrogen productivity was observed at a substrate load of 50 g/l with 1.09 mol H2/mol hexose. With 1.01 mol H2/mol hexose, microwave-assisted treatment was not significantly different from oven-based treatments. This study emphasised the better repeatability of heat shocks with microwave-assisted experiments, revealing low variation coefficients averaging 29%. The pre-treatment with microwaves results in a high predictability and a stronger microbial community shift to Clostridia compared to the treatment with the oven. The pre-treatment of heat shocks supported the formation of butyric acid up to 10.8 g/l on average, with a peak of 24.01 g/l at a butyric/acetic acid ratio of 2.0. Conclusion: The results support the suitability of using heat shock for the entire seed sludge rather than just a small inoculum, making the process more relevant for industrial applications. The performed microwave-based treatment has proven to be a promising alternative to oven-based treatments, which ultimately may facilitate their implementation into industrial systems. This approach becomes economically sustainable with high-temperature heat pumps with a coefficient of performance (COP) of 4.3. [ABSTRACT FROM AUTHOR]

Background: Production of cheese whey in the EU exceeded 55 million tons in 2022, resulting in lactose-rich effluents that pose significant environmental challenges. To address this issue, the present study investigated cheese-whey treatment via membrane filtration and the utilization of its components as fermentation feedstock. A simulation model was developed for an industrial-scale facility located in Italy's Apulia region, designed to process 539 m3/day of untreated cheese-whey. The model integrated experimental data from ethanolic fermentation using a selected strain of Kluyveromyces marxianus in lactose-supplemented media, along with relevant published data. Results: The simulation was divided into three different sections. The first section focused on cheese-whey pretreatment through membrane filtration, enabling the recovery of 56%w/w whey protein concentrate, process water recirculation, and lactose concentration. In the second section, the recovered lactose was directed towards fermentation and downstream anhydrous ethanol production. The third section encompassed anaerobic digestion of organic residue, sludge handling, and combined heat and power production. Moreover, three different scenarios were produced based on ethanol yield on lactose (YE/L), biomass yield on lactose, and final lactose concentration in the medium. A techno-economic assessment based on the collected data was performed as well as a sensitivity analysis focused on economic parameters, encompassing considerations on cheese-whey by assessing its economical impact as a credit for the simulated facility, dictated by a gate fee, or as a cost by considering it a raw material. The techno-economic analysis revealed different minimum ethanol selling prices across the three scenarios. The best performance was obtained in the scenario presenting a YE/L = 0.45 g/g, with a minimum selling price of 1.43 €/kg. Finally, sensitivity analysis highlighted the model's dependence on the price or credit associated with cheese-whey handling. Conclusions: This work highlighted the importance of policy implementation in this kind of study, demonstrating how a gate fee approach applied to cheese-whey procurement positively impacted the final minimum selling price for ethanol across all scenarios. Additionally, considerations should be made about the implementation of the simulated process as a plug-in addition in to existing processes dealing with dairy products or handling multiple biomasses to produce ethanol. [ABSTRACT FROM AUTHOR]

One of the well‐known methods for correctly managing sludge disposal is using produced sludges as fuel in biogas‐burning power plants. This study employed the ReCiPe2016 life cycle assessment methodology in conjunction with SimaPro software to assess the environmental impacts of a biogas‐fired power plant in Tehran with a total capacity of 2.4 MW. The results were analyzed, and the 13 necessary pieces of information for the biogas burning system per 1 MWh produced heat and power by the combined heat and power unit were considered. In anaerobic digestion, heat and power in all classes had reducing effects on the environment. The heat and power classes, reinforced steel, chrome steel, low alloy steel, copper, and cast iron, exhibited the highest environmental impacts within the integrated heat and power system. Among all impact classes, power (for anaerobic digestion) in the class of carcinogenic toxicity in humans with a value of −6.01976 kg 1,4‐DCB and copper (for combined heat and power) in the marine environmental toxicity class with a value of 0.731434 kg 1,4‐DCB had the most reduction effect and the most impact of pollutant on the environment among the considered classes, respectively. Conclusively, in the anaerobic digestion process, heat and power had a positive effect on the environment in all impact classes. So, sludge can be an adequate candidate and anaerobic digestion can be an eco‐friendly method for power generation. Other effect classes are presented in detail as results. This study could guide the development of similar facilities globally, considering factors like wastewater volume and combined heat and power technology. [ABSTRACT FROM AUTHOR]

Dry anaerobic digestion (dry-AD) is an attractive process for solid wastes such as agri-food waste. However, some limitations mainly associated to lack of effective mixing, can hinder the methane production capacity of the systems. Bulking agent (BA) has been proposed as a solution to the compaction issues in systems without mechanical agitation, such as leaching bed reactors. However, effects of BA are still not clear, and, thus, the factors to consider for its dose has not been optimized yet. This work studies the effect of BA in dry-AD. Two substrates with different characteristics were proposed as models, bean peel as a lignocellulosic substrate and a mixture of food waste as a readily biodegradable substrate. Inert plastic rings were used as BA at different BA:S ratios. Assessed BA:S ratio did not affect the performance of methane production for the lignocellulosic waste, but it did significantly affect to the easily biodegradable substrate, showing up to a 28% of methane production increase. This result could be due to the presence of lignocellulosic compounds in the bean peel, behaving like a natural BA. In assays with an increased bed height, the compaction of the system was more severe, resulting in the rapid acidification of the processes. At these conditions, the positive effect of BA addition was more marked, allowing methane production and no acidification of the system. Thus, the addition of BA is a suitable strategy for improving methane production or stability in dry-AD systems without requiring the stirring of the systems. • Bulking agent (BA) addition is assessed as alternative to stirring in dry AD. • Positive effects by BA was due to an increase of the porosity in the digester bed. • Optimal BA:S ratio was strongly dependent on the characteristics of the substrate. • Low lignocellulosic content substrates were more favoured by BA addition. • BA addition was able to avoid acidification by enhancing the methanogenic activity. [ABSTRACT FROM AUTHOR]

AbstractIn this study, the impact of cobalt iron oxide(CoFe2O4) on the anaerobic digestion (AD) of food waste (FW) was investigated including the variations in pH, VFAs, ORP, Fe2+/Fe3+ concentrations, SCOD, dehydrogenase activity, methane production and microbial community structure. The results showed that CoFe2O4 had a positive effect on the anaerobic digestion of food waste. CoFe2O4 could promote the release of SCOD, increase the dehydrogenase concentration and reduce ORP resulting in an increase of methane production. At a CoFe2O4 concentration of 200 mg/L, the cumulative methane production reached to 414.75 mL/(gVS) which was increased by 79.1% compared to the control group(231.59 mL/(gVS)). Meanwhile, the variation of microbial community showed that CoFe2O4 could increase the relative abundance of Methanobacterium and the methane production pathway in the AD was shifted from acetoclastic to hydrogenotrophic. [ABSTRACT FROM AUTHOR]

Wheat straw (WS) is a promising substrate for biogas production by anaerobic digestion (AD) due to its high carbohydrate content. An estimated 0.603 million t yr−1 of WS are generated from wheat production systems in South Africa. This is equivalent to an energy potential of 11 PJ. Despite this, WS is still undervalued as a bioenergy resource in South Africa due to its structural complexity and low nitrogen content. WS disposal methods, such as use in livestock bedding, burning and burying into the soil, inter alia, are not sustainable and may contribute to global warming and climate change. The commercialization of the AD of WS needs to be further developed and promoted. Pre-treatment (i.e., physical, chemical, biological and hybrid methods) and anaerobic co-digestion (AcoD) are novel strategies that can support the conversion of WS into biogas and other value-added products. Current and future research should focus on optimizing pre-treatment and AcoD conditions towards industrialization of WS into valuable products. This paper focuses on the potential use of WS for biogas production in South Africa. The aim is to create information that will promote research and development, and encourage policy makers and stakeholders to participate and invest in WS biogas technology. Were WS biogas technology fully adopted, we believe that it would alleviate energy insecurity and environmental degradation, and sustain the livelihoods of citizens in South Africa. [ABSTRACT FROM AUTHOR]

Triclosan (TCS) is an anti-microbial widely used in personal care and medical antibacterial products. Despite the widespread occurrence of TCS in municipal sewage sludge, understanding toward the fate of TCS within sewage treatment and environmental risks in the eventual land application is still limited. This review summarizes the TCS loads and transfer mechanisms in the sewage treatment process, sludge management process, land application, and its potential environmental impacts. TCS transfer from sewage to sludge mainly occurs in the primary sedimentation process, representing 2.50 to 4.58 times more compared to the secondary sedimentation process. This transfer is facilitated through adsorption because of the presence of humic acid-like and protein-like substances in sludge. Both anaerobic digestion and aerobic composting contribute to the degradation of TCS with aerobic composting being more effective, exhibiting TCS degradation rates 1.04–2.87 times higher than those observed in anaerobic digestion. After sludge land application, TCS majorly dissipates in the soil through biodegradation by fungi and bacteria, potentially posing environmental risks, such as inhibiting the seedling growth of plant species. Additionally, the degradation of TCS, coupled with the formation and subsequent degradation of MeTCS, is observed, with MeTCS exhibiting a higher half-life and greater toxicity than its parent compound (TCS). Overall, this research offers vital insights to enhance understanding of TCS's migration and degradation processes in sewage treatment and soil. It also provides guidance in environmental protection and sustainable resource management. [ABSTRACT FROM AUTHOR]

Brazil is the major producer and exporter of orange juice in the world. Orange peel (OP) derived from juice processing, the main industrial by-product, is generally intended for animal feed without further revalorization. The frozen concentrated orange juice (FCOJ) productive chain presents high energy requirements. A possible route to revalue OP and to generate renewable energy is the anaerobic digestion (AD) technology, for which a previous assessment of the theoretical electricity generation from biogas combustion indicated that 0.017 MWh per ton of OP could be obtained. Aiming to support a clean and renewable energy transition for the citrus industry, a thorough literature search regarding OP revalorization routes was made to investigate the potential energy recovery from AD technology for the Brazilian's FCOJ scenario. The results indicated that the AD of the total OP amount derived from industry could be enough to supply from 71 to 111% of the total energy consumption in the FCOJ chain (from the initial step, i.e., permanent orange fields and their fertilization technologies—organic or conventional systems—until the industrial energy requirements). Despite the agricultural system (organic or conventional), a positive energy replacement can be achieved through the adoption of AD. Finally, the study concluded that FCOJ industry presents an opportunity to obtain energy savings. Moreover, for the Brazilian FCOJ production, OP revalorization could mitigate 9.74 tCO2eq/year of GHG. A decarbonization strategy and a healthy circular economy for the Brazilian citrus industry could flourish from AD adoption as an alternative route for OP disposal. [ABSTRACT FROM AUTHOR]

Oat husks are produced during the milling process of oats. Oat husks are a lignocellulosic material that have the potential for valorization thereby improving the circular economy of agricultural by-products. However, due to the high lignocellulosic content, there are limited valorization pathways for oat husks. To improve the anaerobic digestibility of oat husks, pretreatment was investigated as a method to aid valorization. A novel extrusion process was used in an attempt to fragment the lignocellulosic structure of oat husks prior to anaerobic digestion. The extrusion pre-treatment was investigated to determine the effect it may have on altering the methane yield and digestibility of oat husks. Biochemical methane potential assays were undertaken using oat husks with no pre-treatment and extruded oat husks. These assays demonstrated that extruded oat husks produced a significantly higher methane yield of 264ml/gVS fed, which was 27% greater than the methane yield produced from the untreated oat husks. Similarly, the total solids degradation was also significantly higher for extruded oat husks treatment compared to the untreated oat husks. Overall, the extrusion process demonstrated an increased methane yield for oat husks compared to previously published data. The biomethane potential tests suggest that extruded oat husks would be a feedstock suitable for anaerobic digestion. [ABSTRACT FROM AUTHOR]

Abstract\nNOVELTY STATEMENTCommercial microalgae production is often interrupted by contamination, leading to short production cycles, reinoculation needs, and culture collapses, significantly increasing costs. This study focuses on investigating Recirculated Sedimentation Application (RSA) to control contamination in microalgae culture systems used for wastewater treatment. Chlorella vulgaris culture was grown in an unsterilized mixture of tertiary treatment effluent and centrate of anaerobic digestion wastewater sludge over a 90-day experimental period. 60 L raceway reactor was operated under a light intensity of 275 μM m−2.s−1 with a 16:8 h light-dark photoperiod. To evaluate the effect of RSA on biological-based problems, the experiment was conducted in three phases. The benefits of utilizing RSA were established through the following observations: effective removal of contaminants at an acceptable level without releasing the culture; extension of the biofilm formation time on the inner walls; inhibition of heterotrophic bacteria and nitrification; enhancement of the suspended solids retention capacity of the raceway tank (up to 770 mg.L−1); and improvement in ammonium removal rate to approximately 30 mg.L−1d−1. The ideal salinity level for both ammonium removal and biomass concentration in RSA should be below 0.02%. These findings demonstrate the potential of phycoremediation for sustainable wastewater treatment and contribute to environmental bioremediation strategies.This study investigates the effects of recirculated sedimentation using freshly formed and mature algae, based on settleability differences, for microalgae cultivation in open ponds with unsterilized wastewater, with the aim of maintain a stable and productive biomass community. Additionally, this study contributes to expand the current knowledge on several fronts: including removing contaminants without discharging the culture, improving biomass holding capacity of the reactor, reducing biofilm formation on reactor walls, suppressing bacterial growth in the culture media and enhancing ammonium removal rate. To the best of our knowledge, there have not been no previous studies to evaluate the effectiveness of sedimentation for these purposes. [ABSTRACT FROM AUTHOR]

AbstractThis study explores a novel enzymatic pretreatment approach in anaerobic reactors for dairy wastewater, using lipase AY Amano to enhance methane production and modify microbial and archaeal community composition. Batch and semi-batch reactors with a total volume of 2000 mL were used to treat dairy wastewater with initial COD of 2000 and 15,000 mg L−1, respectively. In a new novel approach, the semi-batch reactors underwent a three-phase operation: 30 days of acclimation, 30 days of rest, and 30 days of active operation. Adding lipase (0.05% wv−1) as a pretreatment significantly increased methane yield over the 90 days by 135–138% compared with the control (without enzyme addition). The organic loading rate reached 0.22 g COD day−1 L−1. Furthermore, 30 days after the end of the semi-batch reactor approach (120 days from the start), reusing sludge in batch reactors increased methane yield by 114–122% compared to the control. This increase was linked to the emergence and shift of new methanogenic communities within the sludge. Integrating hydrolytic enzymes into the anaerobic treatment enhances performance and sustainability by fostering methanogen-enriched microbial communities. This is crucial for maximizing methane production but may increase costs, requiring further economic feasibility research. [ABSTRACT FROM AUTHOR]

In recent years, pelagic Sargassum has invaded the Caribbean coasts, and anaerobic digestion has been proposed as a sustainable management option. However, the complex composition of these macroalgae acts as a barrier to microbial degradation, thereby limiting methane production. Microbial adaptation is a promising strategy to improve substrate utilization and stress tolerance. This study aimed to investigate the adaptation of a microbial consortium to enhance methane production from the pelagic Sargassum. Microbial adaptation was performed in a fed-batch mode for 100 days by progressive feeding of Sargassum. The evolution of the microbial community was analyzed by high-throughput sequencing of 16S rRNA amplicons. Additionally, 16S rRNA data were used to predict functional profiles using the iVikodak platform. The results showed that, after adaptation, the consortium was dominated by the bacterial phyla Bacteroidota, Firmicutes, and Atribacterota, as well as methanogens of the families Methanotrichaceae and Methanoregulaceae. The abundance of predicted genes related to different metabolic functions was affected during the adaptation stage when Sargassum concentration was increased. At the end of the adaptation stage, the abundance of the predicted genes increased again. The adapted microbial consortium demonstrated a 60% increase in both biomethane potential and biodegradability index. This work offers valuable insights into the development of treatment technologies and the effective management of pelagic Sargassum in coastal regions, emphasizing the importance of microbial adaptation in this context. [ABSTRACT FROM AUTHOR]

Background: Clean energy hydrogen (H2) produced from abundant lignocellulose is an alternative to fossil energy. As an essential influencing factor, there is a lack of comparison between constant temperatures (35, 55 and 65 °C) and gradient heating temperature (35 to 65 °C) on the H2 production regulation potential from lignocellulose-rich straw via high-solid anaerobic digestion (HS-AD). More importantly, the microbial mechanism of temperature regulating H2 accumulation needs to be investigated. Results: Constant 65 °C led to the lowest lignin residue (1.93%) and the maximum release of cellulose and hemicellulose, and the highest H2 production (26.01 mL/g VS). H2 production at 35 and 55 °C was only 14.56 and 24.13 mL/g VS, respectively. In order to further explore the potential of ultra-high temperature (65 °C), HS-AD was performed by gradient heating conditions (35 to 65 °C). However, compared to constant 65 °C, gradient heating conditions led to higher lignin residue (2.49%) and lower H2 production (13.53 mL/g VS) than gradient heating conditions (47.98%). In addition, metagenomic analysis showed the cellulose/hemicellulose hydrolyzing bacteria and genes (mainly Thermoclostridium, and xynA, xynB, abfA, bglB and xynD), H2-producing bacteria and related genes (mainly Thermoclostridium, and nifD, nifH and nifK), and microbial movement and metabolic functions were enriched at 65 °C. However, the enrichment of two-component systems under gradient heating conditions resulted in a lack of highly-enriched ultra-high-temperature cellulose/hemicellulose hydrolyzing genera and related genes but rather enriched H2 consumption genera and genes (mainly Acetivibrio, and hyaB and hyaA) resulting in a weaker H2 production. Conclusions: The lignin degradation process does not directly determine H2 accumulation, which was actually regulated by bacteria/genes contributing to H2 production/consumption. In addition, it is temperature that enhances the hydrolysis process of lignin rather than lignin-degrading enzymes, bacteria and genes by promoting microbial material transfer and metabolism. In terms of temperature, one of the key parameters of HS-AD for H2 production, we developed an important regulatory strategy, enriched the theoretical basis of temperature regulation for H2 production to further expanded the research horizon in this field. ABqfqNejHM5MQBNj5XnjcN Video Abstract [ABSTRACT FROM AUTHOR]

Background: In this study, individual methanogenic (anaerobic), granular biofilms were used as true community replicates to assess whole-microbial-community responses to environmental cues. The aggregates were sourced from a lab-scale, engineered, biological wastewater treatment system, were size-separated, and the largest granules were individually subjected to controlled environmental cues in micro-batch reactors (μBRs). Results: Individual granules were identical with respect to the structure of the active community based on cDNA analysis. Additionally, it was observed that the active microbial community of individual granules, at the depth of 16S rRNA gene sequencing, produced reproducible responses to environmental changes in pH, temperature, substrate, and trace-metal supplementation. We identified resilient and susceptible taxa associated with each environmental condition tested, as well as selected specialists, whose niche preferences span the entire trophic chain required for the complete anaerobic degradation of organic matter. Conclusions: We found that single anaerobic granules can be considered highly-replicated whole-ecosystems with potential usefulness for the field of microbial ecology. Additionally, they act as the smallest whole-community unit within the meta-community of an engineered bioreactor. When subjected to various environmental cues, anaerobic granules responded reproducibly allowing for rare or unique opportunities for high-throughput studies testing whole-community responses to a wide range of environmental conditions. [ABSTRACT FROM AUTHOR]

The effects of exogenous acMitivcs such as iron-based materials, compatible solutes and carbon materials on the anaerobic digestion of high-salt wastewater were renewed・ Under the action of high salini* t}\iron ami carbon matrriak can enhance the methanogenesis cfficicnc)-of anaerobic digestion in high sa・ linity by enhancing direct interspecific electron transfer and enriching functional microorganisms・ The compatible solute can be absorbed by microorganisms to halancc the osmotic pressure diflcrcncc, so as to help microorganisms adapt to the high-salt cnnronmrnt faster, and improve the anaerobic digestion treatment effect of high-salt wastru*atrr. [ABSTRACT FROM AUTHOR]

The present study analyzed the effect of temperature, pH, pre-treatment and mixing ratio on the anaerobic digestion process. The parameters during the anaerobic co-digestion of cow manure and food waste were then optimized using the Taguchi experimental design method. ANOVA was carried out to find the significant parameters which influence biogas production. Experimental tests were carried out at laboratory-scale reactors kept at different temperatures (28 °C, 35 °C, and 50 °C). The specific methanogenic performance (SMP) during anaerobic digestion at higher temperatures was characterized with the analysis of acetate, propionate, butyrate, hydrogen, glucose, and formate, and was validated with the literature. The improvement of biogas production with different pre-treatments, i.e., ultrasonic, autoclave, and microwave techniques, was also analyzed. The results showed that the reactor that was maintained at 35 °C showed the highest biogas production, while the reactor that was maintained at a lower temperature (28 °C) produced the lower volume of biogas. As the retention time increases, the amount of biogas production increases. Methanogenic activities of microorganisms were reduced at higher temperature conditions (65 °C). Biogas production increased by 28.1%, 20.23%, and 13.27% when the substrates were treated with ultrasonic, autoclave, and microwave, respectively, compared to the untreated substrate. The optimized condition for the highest biogas production during anaerobic co-digestion of food waste and cow manure is a temperature of 35 °C, a pH of 7 and a mixing ratio (CM:FW = 1.5:0.5). ANOVA showed that temperature is the most important input parameter affecting biogas production, followed by mixing ratio. [ABSTRACT FROM AUTHOR]

Anaerobic digestion is a biological process that transforms high-strength organic effluents into biogas with multiple benefits. However, concurrent with organics' biological transformation, a liquid phase with a high solid content is also derived from this process. Valorizing this fraction is not an easy task if an agronomic application cannot be considered as a suitable option. The thermal valorization of this fraction allows for energy extraction but also gives rise to additional capital investment and increases the energy demand of the global process. In addition, the thermal treatment of digestate has to deal with a mineralized material. The changes in organic matter due to anaerobic digestion were studied in the present manuscript, by evaluating the thermal behavior of samples, activation energy, and organic transformation using Fourier transform infrared (FTIR) spectroscopy. Digested samples of a mixture composed of manure and glycerin (5% v/v) were studied. The stabilization caused a dramatic decrease in aliphatic compounds, greatly increasing the mineral content of the sample. Results from differential scanning calorimetry (DSC) indicated an energy content of 11 kJ/g for the feed material and a reduction to 9.6 kJ/g for the long-term stabilized sample. The activation energy of the feed was 249.5 kJ/mol, whereas this value was reduced to 70–80 kJ/mol for digested samples. If the valorization route selected for digestates is thermal conversion, the lower energy content and more complex structure of these materials (higher content of lignin and protein-type compounds) must be carefully evaluated. [ABSTRACT FROM AUTHOR]

Power scarcity and pollution can be overcome with the use of green energy forms like ethanol, biogas, electricity, hydrogen, etc., especially energy produced from renewable and industrial feedstocks. In hilly areas, pine needles are the most abundant biomass that has a low possibility of valorization due to high lignin content. On the other hand, anaerobic digestion (AD) of lignin and animal waste has low biogas yield due to poor conductivity. This study focuses on the simultaneous production of biogas and electricity through the co-digestion of cow dung and pine needles. The digester was initially established and stabilized in the lab to ensure a continuous supply of inoculum throughout the experiment. The optimization process involved the determination of an ideal cow dung-to-water ratio and selecting the appropriate conductive material that can enhance the energy generation from the feedstock. Afterward, both batch and continuous anaerobic digestion experiments were conducted. The results revealed that the addition of powdered graphite (5 mM), activated charcoal (15 mM), and biochar (25 mM) exhibited maximum voltage of 0.71 ± 0.013 V, 0.56 ± 0.013 V, and 0.49 ± 0.011 V on the 30th, 25th and 20th day of AD, respectively. The batch experiment showed that 5 mM graphite powder enhanced electron transfer in the AD process and generated a voltage of 0.77 ± 0.014 V on the 30th day, indicating an increase of ~1.5-fold as compared to the control (0.56 ± 0.019 V). The results from the continuous AD process showed that the digester with cow dung, pine needle, and a conductive material in combination exhibited the maximum voltage of 0.76 ± 0.012 V on the 21st day of AD, while the digester with cow dung only exhibited a maximum voltage of 0.62 ± 0.015 V on the 22nd day of AD, representing a 1.3-fold increase over the control. Furthermore, the current work used discarded plastic items and electrodes from spent batteries to emphasize waste management and aid in attaining sustainable energy and development goals. [ABSTRACT FROM AUTHOR]

Wastewater treatment plants (WWTPs) contribute to the release of microplastics into the environment. While the removal efficiency of MPs in WWTPs can reach up to 99.9 %, the highest amount of microplastics is retained in the sludge. Anaerobic digestion, one of the most promising and common processes, can help reduce sludge volume and odour, and due to the formation of biogas, mainly consisting of methane (CH4) and carbon dioxide (CO2), can help decrease the operating costs of WWTPs. A test measuring the inhibition of biogas production using the OxiTop® measuring system was employed to determine the effect of added microfibres (MFs) on biogas production. Particles less than 1 mm in size of polyester, polyamide, and polyacrylic, were added to anaerobic sludge at concentrations ranging from 0.05 to 0.10 g l–1 to simulate their effect on biogas production. The yields of CH4 and CO2 produced during anaerobic digestion of the MFs-contaminated sludge were determined. The addition of MFs to sewage sludge affects methane production. The results indicated that the lowest added concentrations of 0.05 g l–1 of MFs promoted methane production, while the presence of 0.1 g l–1 decreased methane production for all types of MFs used. Polyacrylic at 0.1 g l–1 had the most negative effect on methane production (up to 27 %), while polyamide at 0.05 g l–1 reached the highest methane production (up to 25 %). [ABSTRACT FROM AUTHOR]

The influence of adding surfactants on the performance of high-solid anaerobic digestion of horticultural waste was extensively investigated in batch systems. Adding Tween series and polyethylene glycol series non-ionic surfactants had positive effects on biogas production, resulting in 370.1 mL/g VS and 256.6 mL/g VS with Tween 60 and polyethylene glycol 300 at a surfactant-to-grass mass ratio of 0.20, while the biogas production of anaerobic digestion without surfactants was 107.54 mL/g VS. The optimal and economically feasible choice was adding Tween 20 at a ratio of 0.08 g/g grass in high-solid anaerobic digestion. A kinetics model reliably represented the relationship between surfactant concentration and biogas production. The mechanism of surfactants working on lignocellulose was investigated. The improvement in high-solid anaerobic digestion by adding surfactants was attributed to the interaction between lignocelluloses and surfactants and the extraction of biodegradable fractions from the porous structure. An economic analysis showed that adding Tween 20 was likely to make a profit and be more feasible than adding Tween 60 and polyethylene glycol 300. This study confirms the enhancement in biogas production from horticultural waste by adding non-ionic surfactants. [ABSTRACT FROM AUTHOR]

A review of the current state of the theory and practice of bioenergy production from waste allowed us to identify the scientific and applied problem of substantiating the rational configuration of a modular anaerobic bioenergy system, taking into account the volume of organic waste generated in settlements. To solve this problem, this paper develops an approach and an algorithm for matching the configuration of a modular anaerobic bioenergy production system with the amount of organic waste generated in residential areas. Unlike the existing tools, this takes into account the peculiarities of residential areas, which is the basis for accurate forecasting of organic waste generation and, accordingly, determining the configuration of the bioenergy production system. In addition, for each of the scenarios, the anaerobic digestion process is modeled, which allows us to determine the functional indicators that underlie the determination of a rational configuration in terms of cost and environmental performance. Based on the use of the developed tools for the production conditions of the Golosko residential area, Lviv (Ukraine), possible scenarios for the installation of modular anaerobic bioenergy production systems are substantiated. It was found that the greatest annual benefits are obtained from the processing of mixed food and yard waste. The payback period of investments in modular anaerobic bioenergy production systems for given conditions of a residential area largely depends on their configuration and ranges from 3.3 to 8.4 years, which differ from each other by 2.5 times. This indicates that the developed toolkit is of practical value, as it allows the coordination of the rational configuration of modular anaerobic bioenergy production systems with real production conditions. In the future, it is recommended to use the proposed decision support system to model the use of biomass as an energy resource in residential areas, which ensures the determination of the rational configuration of a modular anaerobic bioenergy production system for given conditions. [ABSTRACT FROM AUTHOR]

Additives for anaerobic digestion (AD) can play a significant role in optimizing the process by increasing biogas production, stabilizing the system, and improving digestate quality. The role of additives largely boils down to, among others, enhancing direct interspecies electron transfer (DIET) between microbial communities, resulting in improved syntrophic interactions, adsorption of toxic substances that may inhibit microbial activity, improving microbial activity, and increasing process stability and accelerating the decomposition of complex organic materials, thereby increasing the rate of hydrolysis. Through the aforementioned action, additives can significantly affect AD performance. The function of these materials varies, from enhancing microbial activity to maintaining optimal conditions and protecting the system from inhibitors. The choice of additives should be carefully tailored to the specific needs and conditions of the digester to maximize benefits and ensure sustainability. In light of these considerations, this paper characterizes the most commonly used additives and their combinations based on a comprehensive review of recent scientific publications, including a report on the results of conducted studies. The publication features chapters that describe carbon-based conductive materials, metal oxide nanomaterials, trace metal, and biological additives, including enzymes and microorganisms. It concludes with the chapters summarising reports on various additives and discussing their functional properties, as well as advantages and disadvantages. The presented review is a substantive and concise analysis of the latest knowledge on additives for the AD process. The application of additives in AD is characterized by great potential; hence, the subject matter is very current and future-oriented. [ABSTRACT FROM AUTHOR]