Sign in to use this feature.

Years

Between: -

Subjects

remove_circle_outline
remove_circle_outline
remove_circle_outline
remove_circle_outline
remove_circle_outline
remove_circle_outline
remove_circle_outline
remove_circle_outline
remove_circle_outline

Journals

Article Types

Countries / Regions

Search Results (164)

Search Parameters:
Keywords = organic loading rate (OLR)

Order results
Result details
Results per page
Select all
Export citation of selected articles as:
17 pages, 2975 KiB  
Article
Investigating the Impact of Organic Loading Rates and Magnetic Nanoparticles on the Performance and Stability of Continuous Stirred Tank Reactors
by Asim Ali, Adham Mohammed Alnadish, Sallahuddin Panhwar, Hareef Ahmed Keerio, Abdul Waheed and Rasool Bux Mahar
Processes 2025, 13(7), 2126; https://doi.org/10.3390/pr13072126 - 4 Jul 2025
Viewed by 1233
Abstract
Research on energy demand is advancing, with the addition of nanomaterials in anaerobic digestion increasing stability, accelerating hydrolysis, and reducing microbial inhibition. However, further research is needed to determine the mechanisms, ideal dosages, and long-term impacts. This work used continuous stir tank reactors [...] Read more.
Research on energy demand is advancing, with the addition of nanomaterials in anaerobic digestion increasing stability, accelerating hydrolysis, and reducing microbial inhibition. However, further research is needed to determine the mechanisms, ideal dosages, and long-term impacts. This work used continuous stir tank reactors (CSTRs) to experimentally examine the biocompatibility of iron oxide nanoparticles (Fe3O4-NPs) at a concentration of 75 mg/L at various organic loading rates (OLRs) of 0.3, 0.8, and 1.3 gVS/L.d (CSTRs). The efficiency of the reactors was observed by considering various parameters, such as pH, soluble chemical oxygen demand (sCOD), TVFA formation and degradation, total solids (TS), and volatile solids (VS) removal, as well as methane (CH4) generation. Hence, it was found that the reactor with added NPs (R1) yielded an optimum 725.9 mL/gVS of CH4 and this was achieved at the lowest OLR of 0.3 gVS/Ld. However, another reactor (R2, without NPs), exhibited more stabilized results, ranging from 372.8 to 424.4 mL/gVS at 0.3 to 1.3 gVS/Ld of OLR, respectively. Therefore, in R1, the maximum removal of sCOD, TVFAs, and VS was achieved at 90%, 74%, and 93%, respectively, as compared to R2. Full article
(This article belongs to the Special Issue Advances in Biomass Conversion and Biorefinery Applications)
Show Figures

Figure 1

26 pages, 1964 KiB  
Review
Food Waste Anaerobic Digestion Under High Organic Loading Rate: Inhibiting Factors, Mechanisms, and Mitigation Strategies
by Hong-Ming Wu, Xiang Li, Jia-Ning Chen, Yi-Juan Yan, Takuro Kobayashi, Yong Hu and Xueying Zhang
Processes 2025, 13(7), 2090; https://doi.org/10.3390/pr13072090 - 1 Jul 2025
Viewed by 430
Abstract
Anaerobic digestion (AD) for food waste (FW) treatment has faced many challenges, especially ammonia nitrogen, acid, and salinity inhibition at a high organic loading rate (OLR). Therefore, a systematic understanding of the issues arising during the FW AD process is a necessity under [...] Read more.
Anaerobic digestion (AD) for food waste (FW) treatment has faced many challenges, especially ammonia nitrogen, acid, and salinity inhibition at a high organic loading rate (OLR). Therefore, a systematic understanding of the issues arising during the FW AD process is a necessity under a high OLR (over 3 g-VS/L d). Primarily, in terms of ammonia nitrogen inhibition, ammonia ions inhibit methane synthesis enzymes, and free ammonia (FAN) contributes to the imbalance of microbial protons. Regulation strategies include substrate C/N ratio regulation, microbial domestication, and ammonia nitrogen removal. In addition, with regard to acid inhibition, including volatile fatty acid (VFA) and long-chain fatty acid (LCFA) accumulation, the elevated acid concentration can contribute to reactive oxygen species stress, and a solution to this includes the addition of alkaline agents and trace elements or the use of microbial electrochemical and biofortification technology and micro-aeration-based AD technology. Furthermore, in terms of salinity inhibition, high salinity can result in a rapid increase in cell osmotic pressure, which can cause cell rupture, and water washing and bio-electrochemical AD are defined as solutions. Future research directions are proposed, mainly in terms of avoiding the introduction of novel containments into these regulation strategies and applying them in large-scale AD plants under a high OLR. Full article
Show Figures

Graphical abstract

23 pages, 2646 KiB  
Article
Simultaneous Liquid Digestate Treatment and High-Value Microalgal Biomass Production: Influence of Post-Harvest Storage on Biochemical Profiles
by Ewelina Sobolewska, Michał Komar, Sebastian Borowski, Paulina Nowicka-Krawczyk, António Portugal, Nuno Mesquita, Mariana F. G. Assunção, Berk Aksoy, João Cotas and Leonel Pereira
Molecules 2025, 30(13), 2778; https://doi.org/10.3390/molecules30132778 - 27 Jun 2025
Viewed by 758
Abstract
This study investigated the treatment of unsterilized, undiluted, and unfiltered liquid digestate in a large-scale photobioreactor over a period of 33 weeks using a consortium of microalgae and bacteria. The generated biomass was analyzed for a wide spectrum of value-added compounds. The impact [...] Read more.
This study investigated the treatment of unsterilized, undiluted, and unfiltered liquid digestate in a large-scale photobioreactor over a period of 33 weeks using a consortium of microalgae and bacteria. The generated biomass was analyzed for a wide spectrum of value-added compounds. The impact of organic loading rates (OLR) on the microbial culture was determined, and the influence of the biomass storage method on its qualitative composition was also analyzed. The experiment showed optimal growth of microalgae at OLR = 0.1 gCOD/L/day (where COD is Chemical Oxygen Demand), while a higher OLR value led to culture destabilization. Microglena sp., an algae not commonly applied for digestate treatment, showed low tolerance to changes in process conditions (OLR increase) but high readaptation potential when the OLR was lowered to its initial value. Significant changes in the microbial community were observed during the treatment. In Phases 1 and 2, Desmodesmus subspicatus and Actinomycetota phylum dominated in the community, while in Phase 3, Microglena sp. and Firmicutes were the most abundant. Total nitrogen, orthophosphates, and soluble COD were reduced by 89–99%. The biomass storage method had a notable impact on the content of lipids, fatty acids, and pigments. The protein amount was 32.75–33.59% of total solids (TS), while total lipid content was 15.76–19.00% TS, with stearic and palmitic acid being dominant. The effect of the storage regime on the potential biomass valorization was also discussed. Full article
Show Figures

Figure 1

17 pages, 1333 KiB  
Article
Anaerobic Digestion of the Halophyte Salicornia ramosissima in Co-Digestion with Swine Manure in Lab-Scale Batch and Continuous Reactor Tests
by Aadila Cayenne and Hinrich Uellendahl
Energies 2025, 18(12), 3085; https://doi.org/10.3390/en18123085 - 11 Jun 2025
Viewed by 314
Abstract
This laboratory study investigated the anaerobic co-digestion process of the halophyte S. ramosissima (Sram) together with swine manure (SM) in different mixing ratios in batch and continuous reactor experiments. In the batch experiments, a methane yield of 214 mLCH4·gVS−1 was [...] Read more.
This laboratory study investigated the anaerobic co-digestion process of the halophyte S. ramosissima (Sram) together with swine manure (SM) in different mixing ratios in batch and continuous reactor experiments. In the batch experiments, a methane yield of 214 mLCH4·gVS−1 was obtained for Sram in mono-digestion. In co-digestion with SM, the methane yields were slightly higher than calculated from the yields of each substrate in mono-digestion. Also, the kinetic rate constant in the co-digestion with swine manure increased from 0.219 d−1 for mono-digested S. ramosissima to 0.318 d−1 in the co-digestion of 50:50 Sram:SM (based on VS). Two continuous 5 L lab-scale CSTR reactors were operated: one as a control (100% SM) and the other as a co-digestion reactor with an increasing VS share of Sram (15, 25, and 35%) in the feed. Both reactors were operated at an organic loading rate (OLR) of 2.5 gVS.L−1·d−1 and a hydraulic retention time (HRT) of 20 days. In the continuous process, the highest methane yield of 276 mLCH4·gVS−1 was achieved at a co-digestion VS ratio of Sram:SM 25:75, corresponding to a methane yield from the added S. ramosissima of 277 mLCH4·gVS−1. This showed successful operation of the continuous co-digestion process of S. ramosissima and swine manure, with higher methane yields of S. ramosissima than in the mono-digestion batch tests. Full article
(This article belongs to the Special Issue Biomass Resources to Bioenergy: 2nd Edition)
Show Figures

Figure 1

20 pages, 3749 KiB  
Article
Performance Characteristics of a Pilot-Scale Electromethanogenic Reactor Treating Brewery Wastewater
by Kyle Bowman, Marcelo Elaiuy, George Fudge, Harvey Rutland, William Gambier, Theo Hembury, Ben Jobling-Purser, Thomas Fudge, Izzet Kale and Godfrey Kyazze
Energies 2025, 18(11), 2939; https://doi.org/10.3390/en18112939 - 3 Jun 2025
Viewed by 557
Abstract
A pilot-scale (4000 L) continuous flow electromethanogenic reactor (EMR), also known as a microbial electrochemical cell coupled with an anaerobic digester (MEC-AD), treating brewery wastewater was designed and installed at Hepworth’s Brewery, UK. This investigation presents a 4-fold increase in size compared to [...] Read more.
A pilot-scale (4000 L) continuous flow electromethanogenic reactor (EMR), also known as a microbial electrochemical cell coupled with an anaerobic digester (MEC-AD), treating brewery wastewater was designed and installed at Hepworth’s Brewery, UK. This investigation presents a 4-fold increase in size compared to the next largest pilot-scale MEC-AD system presented in the literature, providing findings to inform the operation of a 52,000 L MEC-AD system (currently under construction). Housed in a 20 ft shipping container, the pilot system features four 1000 L reaction vessels arranged in series, each with a working volume of 900 L. Each reaction vessel contained 8 electrode modules. The system was tested over varying organic loading rates (OLRs), achieved through systematic reductions in hydraulic retention time (HRT). HRTs between 24 and 1.8 days were investigated to align with commercial viability targets. OLRs were observed from 0.4 to 7.5 kgCOD/m3/d. A maximum stable OLR of 6.75 kgCOD/m3/d at a HRT of 2.3 days was observed while maintaining COD removal of 65 and 88% over the first two vessels. This pilot demonstrated commercially viable performance of an EMR at a brewery, resulting in the purchase of the technology at commercial scale (52,000 L) to form part of a wastewater treatment system. Full article
(This article belongs to the Section A: Sustainable Energy)
Show Figures

Graphical abstract

30 pages, 6159 KiB  
Article
Co-Digestion of Cattle Slurry and Food Waste: Perspectives on Scale-Up
by Angela Bywater, Jethro A. H. Adam, Sigrid Kusch-Brandt and Sonia Heaven
Methane 2025, 4(2), 8; https://doi.org/10.3390/methane4020008 - 4 Apr 2025
Viewed by 753
Abstract
Anaerobic digesters fed with dairy cow slurry struggle to achieve economic viability, particularly when animals are housed seasonally, so additional feedstocks are usually required. This study applied experimentally derived data from the co-digestion of cow slurry (CS) and food waste (FW) to the [...] Read more.
Anaerobic digesters fed with dairy cow slurry struggle to achieve economic viability, particularly when animals are housed seasonally, so additional feedstocks are usually required. This study applied experimentally derived data from the co-digestion of cow slurry (CS) and food waste (FW) to the UK dairy herd as a whole, and at average (AH) and large (LH) herd sizes of 160 and 770 animals, respectively. The experimental data confirmed stable operation at an organic loading rate (OLR) of 5 g VS L−1 day−1 at CS:FW ratios of 3:1 and 6:1 on a wet weight basis, and these parameters were considered for both AH and LH by herd size and country (Scotland, England, Wales, Northern Ireland) in order to provide energy production and policy observations. The results showed that these scenarios could provide between 959 to 23,867 GJ per year, and that a targeted policy intervention could affect slurry treatment from a significant number of animals in a relatively small number of large herds across the UK. For a more detailed analysis, better data are required on non-domestic FW arisings and FW transportation needs. Full article
(This article belongs to the Special Issue Anaerobic Digestion Process: Converting Waste to Energy)
Show Figures

Figure 1

17 pages, 3495 KiB  
Article
Optimizing Anaerobic Co-Digestion Formula of Agro-Industrial Wastes in Semi-Continuous Regime
by Ana I. Parralejo, Jerónimo González, Luis Royano and Juan F. González
Energies 2025, 18(7), 1689; https://doi.org/10.3390/en18071689 - 28 Mar 2025
Viewed by 390
Abstract
The actual environmental and energy crises are two of the main problems existing in the world. Among the different technologies that can be implemented is anaerobic digestion, which employs waste and renewable biomass materials. To reach the optimum ratio of different raw materials [...] Read more.
The actual environmental and energy crises are two of the main problems existing in the world. Among the different technologies that can be implemented is anaerobic digestion, which employs waste and renewable biomass materials. To reach the optimum ratio of different raw materials or substrates in the feed of digesters, laboratory tests are necessary. This work aims to study the increase in the Organic Load Rate (OLR) (1 g VS L−1d−1, 2 g VS L−1d−1, 3 g VS L−1d−1 and 4 g VS L−1d−1, VS: Volatile Solid) and the raw materials number (sorghum (S), pig manure (P), triticale (T), corn stover (C) and microalgae biomass (M)) in the feedstock of the anaerobic digestion process. Mean values of methane yields for the evaluated set were lower in SMP and SMPTC assays (149.80 LCH4 kg VS−1 and 157.15 LCH4 kg VS−1, respectively) than SP, SM and SMPT assays (195.09 LCH4 kg VS−1, 197.69 LCH4 kg VS−1 and 195.76 LCH4 kg VS−1, respectively). Along the experiments, several parameters were evaluated, along with their interactions with OLR and number of raw materials. Two kinetic models were employed to fit the COD (Chemical Oxygen Demand) removal results. Full article
(This article belongs to the Special Issue Sustainable Biofuels for Carbon Neutrality)
Show Figures

Figure 1

14 pages, 2506 KiB  
Article
Bio-Refinery of Organics into Value-Added Biopolymers: Exploring the Effects of Hydraulic Retention Time and Organic Loading Rate on Biopolymer Harvesting from a Biofilm-Based Process
by Qingna Shang, Lin Li, Yi Zhang, Xueqing Shi, Harsha Ratnaweera, Dong-Hoon Kim and Haifeng Zhang
Toxics 2025, 13(3), 183; https://doi.org/10.3390/toxics13030183 - 28 Feb 2025
Viewed by 872
Abstract
This study aimed to examine the impacts of hydraulic retention time (HRT) and organic loading rate (OLR) on the alginate-like exopolymers’ (ALEs) recovery potential from a biofilm-based process. A lab-scale moving bed biofilm reactor (MBBR) was operated under different HRT (12.0, 6.0, and [...] Read more.
This study aimed to examine the impacts of hydraulic retention time (HRT) and organic loading rate (OLR) on the alginate-like exopolymers’ (ALEs) recovery potential from a biofilm-based process. A lab-scale moving bed biofilm reactor (MBBR) was operated under different HRT (12.0, 6.0, and 2.0 h) and OLR (1.0, 2.0, and 6.0 kg COD/m3/d) conditions. The results demonstrated that the reduction in HRT and increase in OLR had remarkable effects on enhancing ALE production and improving its properties, which resulted in the ALE yield increasing from 177.8 to 221.5 mg/g VSS, with the protein content rising from 399.3 to 494.3 mg/g ALE and the enhanced alginate purity by 39.8%, corresponding to the TOC concentration increasing from 108.3 to 157.0 mg/g ALE. Meanwhile, to illustrate different ALE recovery potentials, microbial community compositions of the MBBR at various operational conditions were also assessed. The results showed that a higher relative abundance of EPS producers (29.86%) was observed in the MBBR with an HRT of 2.0 h than that of 12.0 h and 6.0 h, revealing its higher ALE recovery potential. This study yields crucial results in terms of resource recovery for wastewater reclamation by providing an effective approach to directionally cultivating ALEs. Full article
Show Figures

Graphical abstract

30 pages, 4323 KiB  
Article
A Multilayer Perceptron Feedforward Neural Network and Particle Swarm Optimization Algorithm for Optimizing Biogas Production
by Arief Abdurrakhman, Lilik Sutiarso, Makhmudun Ainuri, Mirwan Ushada and Md Parvez Islam
Energies 2025, 18(4), 1002; https://doi.org/10.3390/en18041002 - 19 Feb 2025
Cited by 1 | Viewed by 1172
Abstract
Efficient biogas production significantly impacts greenhouse gas (GHG) emissions and carbon sequestration by reducing emissions and enhancing carbon storage. Nonetheless, the consistency and optimization of biogas production are hindered by fluctuations in key input variables, namely, pH, moisture content, organic loading rate (OLR), [...] Read more.
Efficient biogas production significantly impacts greenhouse gas (GHG) emissions and carbon sequestration by reducing emissions and enhancing carbon storage. Nonetheless, the consistency and optimization of biogas production are hindered by fluctuations in key input variables, namely, pH, moisture content, organic loading rate (OLR), and temperature, which significantly impact the quality of agricultural waste biomass and biogas production. Any fluctuations in these variables can affect biogas productivity. This study aims to provide valuable optimization parameters for maximum biogas production using rice straw and cow dung as agricultural waste biomass for biogas input materials. Therefore, machine learning techniques such as multilayer perceptron feedforward neural networks with a particle swarm optimization (PSO) combination generate optimal values for each variable for maximum biogas production. This study uses three variants of the training function for neural networks, namely gradient descent with momentum and adaptive learning rate, gradient descent with momentum, and gradient descent with adaptive learning rate. The findings reveal that, under an optimum pH value of 6.0000, a humidity of 62.3176%, an OLR of 67.6823 kg.m3/day, and a temperature of 37.0482 °C, biogas production has the potential to increase to 2.91 m³/day with a high accuracy testing value of R2 = 0.90. These methods in use accurately predict the optimal parameters, with a maximum deviation of 8.48% from experimentally derived values and mean square error (MSE) of 0.0051243. This study emphasizes the benefits of using multilayer perceptron feedforward neural networks and particle swarm optimization to optimize operational parameters and accurately predict biogas production. Full article
(This article belongs to the Special Issue Environmental Applications of Bioenergy and Biomass, 2nd Edition)
Show Figures

Figure 1

28 pages, 6080 KiB  
Article
Meat-Processing Wastewater Treatment Using an Anaerobic Membrane Bioreactor (AnMBR)
by Ferdinand Hummel, Lisa Bauer, Wolfgang Gabauer and Werner Fuchs
Fermentation 2025, 11(2), 68; https://doi.org/10.3390/fermentation11020068 - 1 Feb 2025
Cited by 1 | Viewed by 1707
Abstract
This study explores AnMBR technology as a promising method for treating wastewater from the meat-processing industry by analysing its characteristics and impact under continuous feeding. The solids were retained, utilising an ultrafiltration membrane with a pore size of 0.2 µm, and the efficacy [...] Read more.
This study explores AnMBR technology as a promising method for treating wastewater from the meat-processing industry by analysing its characteristics and impact under continuous feeding. The solids were retained, utilising an ultrafiltration membrane with a pore size of 0.2 µm, and the efficacy of reducing the organic load was evaluated. Although the COD removal rate decreased from 100% at an OLR of 0.71 g/(L*d) to 73% at an OLR of 2.2 g/(L*d), maximum methane yields were achieved at the highest OLR, 292.9 Nm3/t (COD) and 397.8 Nm3/t (VS) per loaded organics and 353.1 Nm3/t (COD) and 518.7 Nm3/t (VS) per removed organics. An analysis of the microbial community was performed at the end of the experiment to assess the effects of the process and the substrate on its composition. The AnMBR system effectively converts meat-processing wastewater into biogas, maintaining high yields and reducing the loss of dissolved methane in the permeate, thanks to a temperature of 37 °C and high salt levels. AnMBR enables rapid start-up, efficient COD removal, and high biogas yields, making it suitable for treating industrial wastewater with high organic loads, enhancing biogas production, and reducing methane loss. Challenges such as high salt and phosphate levels present opportunities for a wider use in nutrient recovery and water reclamation. Full article
(This article belongs to the Special Issue Food Wastes: Feedstock for Value-Added Products: 5th Edition)
Show Figures

Figure 1

13 pages, 2084 KiB  
Article
Methane Production, Microbial Community, and Volatile Fatty Acids Profiling During Anaerobic Digestion Under Different Organic Loading
by Paulina Rusanowska, Marcin Zieliński, Marta Kisielewska, Magda Dudek, Łukasz Paukszto and Marcin Dębowski
Energies 2025, 18(3), 575; https://doi.org/10.3390/en18030575 - 25 Jan 2025
Cited by 3 | Viewed by 1119
Abstract
The organic loading rate (OLR) is a crucial parameter in the anaerobic digestion of lignocellulosic biomass. Optimizing the OLR ensures a balanced substrate release for gradual hydrolysis, thereby preventing the accumulation of inhibitors that can disrupt methanogenesis. Its significance lies in its direct [...] Read more.
The organic loading rate (OLR) is a crucial parameter in the anaerobic digestion of lignocellulosic biomass. Optimizing the OLR ensures a balanced substrate release for gradual hydrolysis, thereby preventing the accumulation of inhibitors that can disrupt methanogenesis. Its significance lies in its direct impact on the stability, efficiency, and overall performance of the digestion process. This study investigated the long-term anaerobic co-digestion of lignocellulosic biomass (Sida hermaphrodita) and cattle manure under varying organic loading rates (S1: 2 kgVS/m3·d, S2: 3 kgVS/m3·d, and S3: 4 kgVS/m3·d). Methane production, microbial community dynamics, and volatile fatty acid (VFA) profiles were analyzed. During S1 and S2, methane production was stable, achieving 446.3 ± 153.7 NL/kgVS and 773.4 ± 107.8 NL/kgVS, respectively. However, at S3, methane production declined, accompanied by a pH drop from 7.68 to 6.11, an increase in the FOS/TAC ratio from 0.272 to 0.35, and the accumulation of acetic and propionic acids at the end of the digestion cycle. Microbial analysis revealed that the abundance of Firmicutes increased with higher OLRs, reaching 93.6% in S3, while the Bacteroidota abundance decreased, reaching 3.0% in S3. During S1, methane production occurred through both acetoclastic and hydrogenotrophic pathways. Full article
(This article belongs to the Section A4: Bio-Energy)
Show Figures

Figure 1

19 pages, 11809 KiB  
Article
Synergistic Promotion of Direct Interspecies Electron Transfer by Biochar and Fe₃O₄ Nanoparticles to Enhance Methanogenesis in Anaerobic Digestion of Vegetable Waste
by Hongruo Ma, Long Chen, Wei Guo, Lei Wang, Jian Zhang and Dongting Zhang
Fermentation 2024, 10(12), 656; https://doi.org/10.3390/fermentation10120656 - 18 Dec 2024
Cited by 3 | Viewed by 1394
Abstract
When vegetable waste (VW) is used as a sole substrate for anaerobic digestion (AD), the rapid accumulation of volatile fatty acids (VFAs) can impede interspecies electron transfer (IET), resulting in a relatively low biogas production rate. In this study, Chinese cabbage and cabbage [...] Read more.
When vegetable waste (VW) is used as a sole substrate for anaerobic digestion (AD), the rapid accumulation of volatile fatty acids (VFAs) can impede interspecies electron transfer (IET), resulting in a relatively low biogas production rate. In this study, Chinese cabbage and cabbage were selected as the VW substrates, and four continuous stirred tank reactors (CSTRs) were employed. Different concentrations of biochar-loaded nano-Fe3O4(Fe3O4@BC) (100 mg/L, 200 mg/L, 300 mg/L) were added, and the organic loading rate (OLR) was gradually increased during the AD process. The changes in biogas production rate, VFAs, and microbial community structure in the fermentation tanks were analyzed to identify the optimal dosage of Fe3O4@BC and the maximum OLR. The results indicated that at the maximum OLR of 3.715 g (VS)/L·d, the addition of 200 mg/L of Fe3O4@BC most effectively promoted an increase in the biogas production rate and reduced the accumulation of VFAs compared to the other treatments. Under these conditions, the biogas production rate reached 0.658 L/g (VS). Furthermore, the addition of Fe3O4@BC enhanced both the diversity and abundance of bacteria and archaea. At the genus level, the abundance of Christensenellaceae_R-7_group, Sphaerochaeta, and the archaeal genus Thermovirga was notably increased. Full article
Show Figures

Graphical abstract

14 pages, 2061 KiB  
Article
Response of Metabolic Gene Panel to Organic Loading Stress in Propionate-Degrading Methanogenic Anaerobic Digesters
by Kris Anthony Silveira, Soraya Zahedi Diaz, Anna Calenzo, Vincent O’Flaherty and Fernando G. Fermoso
Agronomy 2024, 14(12), 2922; https://doi.org/10.3390/agronomy14122922 - 6 Dec 2024
Viewed by 1018
Abstract
Propionate, a critical intermediate in anaerobic digestion, and its syntrophic removal, is sensitive to stress. To our knowledge, this study investigates for the first time the response of a metabolic gene panel to organic loading rate (OLR) stress in propionate-degrading methanogenic consortia in [...] Read more.
Propionate, a critical intermediate in anaerobic digestion, and its syntrophic removal, is sensitive to stress. To our knowledge, this study investigates for the first time the response of a metabolic gene panel to organic loading rate (OLR) stress in propionate-degrading methanogenic consortia in lab-scale upflow anaerobic sludge blanket (UASB) reactors. The experimental phases included stabilisation (1.4–2.8 g COD/L/day), electroactive enrichment, OLR shock (6 g COD/L/day), and early recovery. Quantitative PCR was used to assess the abundance of key functional genes (16SrRNA, mcrA, pilA, and hgtR). During stabilisation, ~200 mLCH₄/h was produced, the mcrA/16SrRNA ratio was 0.78–2.64, and pilA and hgtR abundances were 1.29–2.27 × 105 and 2.12–4.37 × 104 copies/gVS. Following the OLR shock, methane production ceased entirely, accompanied by a sharp decline in the mcrA/16S ratio (0.08–0.24) and significant reductions in pilA (1.43-log) and hgtR (1.34-log) abundance. Partial recovery of pilA and hgtR abundance (1.19 × 105 and 8.57 × 104) was observed in the control reactor after the early recovery phase. The results highlight the utility of mcrA, 16SrRNA, pilA, and associated ratios, as reliable indicators of OLR stress in lab-scale UASB reactors. This study advances the understanding of molecular stress responses in propionate-degrading methanogenic consortia, focusing on direct interspecies electron transfer in process stability and recovery. Full article
Show Figures

Graphical abstract

13 pages, 1880 KiB  
Article
Investigating the Influence of Organic Loading Rate, Temperature and Stirring Speed on Biogas Production Using Agricultural Waste in South Africa
by Ephodia Sihlangu, Primrose Magama, Idan Chiyanzu, Thierry Regnier, Dibungi Luseba and Khathutshelo Agree Nephawe
Agriculture 2024, 14(11), 2091; https://doi.org/10.3390/agriculture14112091 - 20 Nov 2024
Cited by 2 | Viewed by 1513
Abstract
Biogas production offers an alternate method for managing agricultural waste and contributes to sustainable renewable energy generation. Anaerobic digestion (AD) enables the transformation of organic waste, including agricultural substrates, into biogas, mostly consisting of methane, carbon dioxide, and trace gases such as ammonia [...] Read more.
Biogas production offers an alternate method for managing agricultural waste and contributes to sustainable renewable energy generation. Anaerobic digestion (AD) enables the transformation of organic waste, including agricultural substrates, into biogas, mostly consisting of methane, carbon dioxide, and trace gases such as ammonia and hydrogen sulphide. The objective of this study was to employ a 30 L semi-continuous stirred tank reactor to evaluate the effects of organic loading rate, temperature, and speed of stirring on biogas production. The reactor was inoculated with 8.6 L and filled with 11.4 L of a mixed substrate including cattle manure, potato waste, potato starch waste, fruit waste, and expired dry dog food. The reactor was evaluated with organic loading rates (OLRs) of 11.2, 12.2, and 13.2 g VS/L d, and stirring speeds of 25.5, 35.5, and 45.5 rpm. The results indicated that the maximum yield was 12.2 g VS/L d at 45.5 rpm, and in thermophilic conditions, the biogas yield surpassed that of mesophilic conditions, measuring 105,860 NmL/g VS compared to 69,800 NmL/g VS. This study emphasises the significance of optimising operational parameters to improve biogas output, thereby contributing to sustainable energy resources and advancing the Sustainable Development Goals (SDGs). Full article
(This article belongs to the Section Agricultural Technology)
Show Figures

Figure 1

26 pages, 1613 KiB  
Review
Food Waste as Feedstock for Anaerobic Mono-Digestion Process
by Wirginia Tomczak, Monika Daniluk and Anna Kujawska
Appl. Sci. 2024, 14(22), 10593; https://doi.org/10.3390/app142210593 - 17 Nov 2024
Viewed by 1975
Abstract
There is a growing recognition that food waste (FW) comprises a significant amount of unused energy. Indeed, FW shows great potential to produce methane (CH4)-rich biogas via an anaerobic digestion (AD) process. Nevertheless, to ensure high AD process performance, deepening the [...] Read more.
There is a growing recognition that food waste (FW) comprises a significant amount of unused energy. Indeed, FW shows great potential to produce methane (CH4)-rich biogas via an anaerobic digestion (AD) process. Nevertheless, to ensure high AD process performance, deepening the knowledge of FW characteristics is required. Furthermore, the biogas yield is strongly influenced by several operational parameters. Taking into account the above, in the current study, based on the data in the literature, the physicochemical parameters of FW generated throughout the world are presented and discussed. In addition, the performance profile of the single-stage anaerobic mono-digestion process with the use of FW as a feedstock was investigated. The performed analysis clearly demonstrated that FW is characterized by significant variations in several parameters, such as pH, the total solid (TS) and volatile solid (VS) contents, the volatile solids to total solids ratio (VS/TS), soluble chemical oxygen demand (sCOD), the concentrations of VFAs and ammonium nitrogen (NH4+-N), and the carbon-to-nitrogen ratio (C/N). Moreover, it was shown that the selected operational parameters, such as temperature, pH, the ratio of food waste to inoculum (I) (FW/I), and the organic loading rate (OLR), may have the most significant impact on the performance of the single-stage anaerobic mono-digestion process. In addition, it was found that most of the experimental investigations presented in the literature were conducted on a laboratory scale. Hence, in future research, more effort should be made to determine the biogas yield with the use of full-scale systems. To summarize, it should be clearly highlighted that the analysis presented in this study may have important implications for the management and application of FW as feedstock for an anaerobic mono-digestion process on an industrial scale. Full article
(This article belongs to the Special Issue Advances in Bioprocess Monitoring and Control)
Show Figures

Figure 1

Back to TopTop