Anaerobic Digestion Processes

Journal Name	Impact Factor	CiteScore	Launched Year	First Decision (median)	APC
Processes processes	2.8	5.1	2013	14.4 Days	CHF 2400
Energies energies	3.0	6.2	2008	17.5 Days	CHF 2600
Microorganisms microorganisms	4.1	7.4	2013	13.4 Days	CHF 2700
Biomass biomass	-	2.9	2021	24.1 Days	CHF 1000
Water water	3.0	5.8	2009	16.5 Days	CHF 2600
Sustainability sustainability	3.3	6.8	2009	20 Days	CHF 2400
Applied Sciences applsci	2.5	5.3	2011	17.8 Days	CHF 2400

16 pages, 3833 KiB

Open AccessArticle

Comparison of Anaerobic Co-Digestion of Buffalo Manure and Excess Sludge with Different Mixing Ratios under Thermophilic and Mesophilic Conditions

by Youfei Zhou, Weijie Hu, Jun Sheng, Cheng Peng and Tianfeng Wang

Sustainability 2023, 15(8), 6690; https://doi.org/10.3390/su15086690 - 14 Apr 2023

Cited by 1 | Viewed by 1364

Abstract

In this study, the main aim is to evaluate the mixing ratio of co-digestion of buffalo manure (BM) and excess sludge (ES) influenced for methane yield and digestate dewaterability. Five batch experiments with different BM and ES mixing ratios were carried out under [...] Read more.

In this study, the main aim is to evaluate the mixing ratio of co-digestion of buffalo manure (BM) and excess sludge (ES) influenced for methane yield and digestate dewaterability. Five batch experiments with different BM and ES mixing ratios were carried out under thermophilic and mesophilic conditions. The methane yield of co-digestion of BM and ES increased by 10.1–73.5% under thermophilic conditions and 87.9–153.3% under mesophilic conditions, compared with the mono-anaerobic digestion of ES under the same conditions. Shannon and Chao1 indices showed that the bacterial species of the mesophilic digesters were more abundant than that of the thermophilic digesters. With the increase in the BM proportion in the substrate, the normalized capillary suction time (NCST) and total solids (TS) of sediment (centrifugal dewatering) increased. The NCST at thermophilic temperature (8.98–12.54 s∙g⁻¹-TS) was greater than that at the mesophilic temperatures (5.45–12.32 s∙g⁻¹-TS). However, the TS of sediment was not directly related to the digestion temperature. This study has shown that anaerobic co-digestion of BM and ES at the appropriate ratio (BM/ES = 1:1.5) has a significant meaning in a high methane yield. Full article

(This article belongs to the Topic Anaerobic Digestion Processes)

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15 pages, 7296 KiB

Open AccessArticle

Patterns in the Course of Gas Production Rates in Anaerobic Digestion—Prediction of Gas Production Rates Based on Deconvolution and Linear Regression

by Christian Hubert, Steffen Krause and Christian Schaum

Water 2023, 15(4), 614; https://doi.org/10.3390/w15040614 - 4 Feb 2023

Viewed by 1756

Abstract

Anaerobic digestion, including the gas storage and the CHP unit plays a key role in energy management of water ressource recovery facilities (WRRF). By demand-driven feeding management, a higher degree of utilization of the gas storage tanks can be achieved, which means that [...] Read more.

Anaerobic digestion, including the gas storage and the CHP unit plays a key role in energy management of water ressource recovery facilities (WRRF). By demand-driven feeding management, a higher degree of utilization of the gas storage tanks can be achieved, which means that a greater decoupling of energy demand and energy generation is taking place. In this context, the predictability of the produced gas volume plays an important role. In this study, a concept was suggested to forecast gas production rates without the need for any analytical substrate characterization. Substrates lead to specific patterns in the course of the gas production rates, which can be fitted using Gaussian functions. As the parameters describing the Gaussian functions have a good correlation to the amount of substrate fed to the digester a prediction of the rates is possible. Within this study a coefficient of determination 82.9% over a period of 5 days was achieved. Full article

(This article belongs to the Topic Anaerobic Digestion Processes)

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<math display="inline"><semantics> <msub> <mi>k</mi> <mrow> <mi>h</mi> <mi>y</mi> <mi>d</mi> </mrow> </msub> </semantics></math>-values for carbohydrates, proteins and lipids evaluated by Christ et al. [<a href="#B19-water-15-00614" class="html-bibr">19</a>] (a), Gujer [<a href="#B20-water-15-00614" class="html-bibr">20</a>] with data of O’Rourke [<a href="#B21-water-15-00614" class="html-bibr">21</a>] (b) and Garcia-Heras [<a href="#B22-water-15-00614" class="html-bibr">22</a>] in [<a href="#B23-water-15-00614" class="html-bibr">23</a>] (c). Full article ">Figure 2
Course of the gas production rate after feeding the reactor with glycerin (a) and after feeding with a sewage sludge sample spiked with glycerin (b). The diagram below shows the intersection of (a) and (b). Full article ">Figure 3
Deconvolution of gas production rate curve 7 into three gaussian functions; COD-balance: Percentages represent the share of the COD-equivalents of the deconvoluted peaks on the amount of COD of the feed. For better illustration the course of gas production rate was flattend. Full article ">Figure 4
Gas production rates during 20 days of reactor operation. Blue dots are representing the extreme values due to the feeding. The numbers are a sequential numbering of the gas production rate curves that occur after feeding. For better visualisation feeding events 8 to 12 were excluded. Full article ">Figure 5
Linear relationship between <math display="inline"><semantics> <mrow> <msub> <mi>w</mi> <mi>i</mi> </msub> <mo>,</mo> <msub> <mi>A</mi> <mi>i</mi> </msub> <mo>,</mo> <msub> <mi>x</mi> <mrow> <mi>c</mi> <mo>,</mo> <mi>i</mi> </mrow> </msub> </mrow> </semantics></math> and the amount of substrate added. Red dots represent OLR > 5 kg TVS/L. They were not taken into account in calculating R<math display="inline"><semantics> <msup> <mrow/> <mn>2</mn> </msup> </semantics></math>. Full article ">Figure 6
Proposed model scheme for prediction of gas production rates consisting of 5 steps. Full article ">Figure 7
Gaussian fit of the curves 1, 2 and 3 (see <a href="#water-15-00614-f004" class="html-fig">Figure 4</a>). Upper figure shows the fitted gas production rate course (green) in comparison to the measured (blue) and the course calculated with initial values (red). Lower figure shows the separated Gaussian functions (green) for each curve. Full article ">Figure 8
Prediction of gas production rates from 5 feeding events. The first three curves are used to optimize the Gaussian parameters (green). Based on the optimized values the following 5 curves are predicted (yellow). Full article ">

17 pages, 5083 KiB

Open AccessArticle

pH-Based Control of Anaerobic Digestion to Maximise Ammonium Production in Liquid Digestate

by Lonestar Gonde, Tristan Wickham, Hendrik Gideon Brink and Willie Nicol

Water 2023, 15(3), 417; https://doi.org/10.3390/w15030417 - 19 Jan 2023

Cited by 5 | Viewed by 4272

Abstract

A typically overlooked by-product of the anaerobic digestion process is the liquid digestate. The digestate is generally high in valuable nutrients like nitrogen, potassium, and phosphorus, which are essential for plant growth. This indicates that digestate can be an effective fertilizer. In this [...] Read more.

A typically overlooked by-product of the anaerobic digestion process is the liquid digestate. The digestate is generally high in valuable nutrients like nitrogen, potassium, and phosphorus, which are essential for plant growth. This indicates that digestate can be an effective fertilizer. In this study, the pH of the anaerobic digestion process was controlled at three different set points (6, 7, and 8) for three different substrates (banana peels, cow dung, and red lentils) in order to determine the ammonium release characteristics at each set point. This was achieved by using two different set-ups; one set-up, named the daily dosing set-up (DDS), incorporated pH corrections once a day, and the other set-up, named the continuous dosing set-up (CDS), corrected the pH every minute. It was discovered that a pH of 7 is the optimal set point for both ammonium release as well as the gas production rate. In terms of a comparative analysis between precise pH control being performed every minute and pH control that was performed once a day, there were differences present in the gas production profiles with the CDS providing enhanced rates compared to the DDS. However, there was a negligible difference in the ammonium release rate. Full article

(This article belongs to the Topic Anaerobic Digestion Processes)

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38 pages, 3153 KiB

Open AccessReview

Exploring Potentials for Bioresource and Bioenergy Recovery from Vinasse, the “New” Protagonist in Brazilian Sugarcane Biorefineries

by Lucas T. Fuess, Piet N. L. Lens, Marcelo L. Garcia and Marcelo Zaiat

Biomass 2022, 2(4), 374-411; https://doi.org/10.3390/biomass2040025 - 13 Dec 2022

Cited by 7 | Viewed by 2945

Abstract

Vinasse management in biorefineries bears a burden for sugarcane industries. Despite its high potassium-related fertilizer potential, a series of negative environmental impacts is expected to occur in long-term soil applications of vinasse through fertirrigation. Conversely, a high biodegradable organic content characterizes vinasse as [...] Read more.

Vinasse management in biorefineries bears a burden for sugarcane industries. Despite its high potassium-related fertilizer potential, a series of negative environmental impacts is expected to occur in long-term soil applications of vinasse through fertirrigation. Conversely, a high biodegradable organic content characterizes vinasse as a potential substrate for bioresource and bioenergy recovery from numerous (bio)technological perspectives. This review presents the alternative approaches proposed for sugarcane vinasse management in Brazil, with special attention dedicated to the role of anaerobic digestion as the core conversion step. The suitability of applying phase separation, i.e., the separation of fermentation from methanogenesis in sequential reactors, is discussed in detail. Laboratory and full-scale experiences were considered to discuss the energetic potential of sugarcane vinasse through biogas generation. With a national installed capacity of up to 1603 MW, energy from vinasse could replace half of the coal-derived electricity in Brazil. Meanwhile, investing in vinasse fermentation to obtain soluble organic metabolites could provide more than 10 g L⁻¹ of (iso)butyrate. This is the first review addressing the potential use of sugarcane vinasse in anaerobic biorefineries that discusses applications far beyond conventional biogas production, and encourages the rational use of vinasse as a raw material for bioprocesses, either in short- or long-term scenarios. Full article

(This article belongs to the Topic Anaerobic Digestion Processes)

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Graphical abstract

Graphical abstract
Full article ">Figure 1
Generation and destination of solid and liquid residual streams in (<bold>a</bold>) conventional first generation (1G) and (<bold>b</bold>) integrated first and second generation (1G2G) sugarcane biorefineries. Full article ">Figure 2
Simplified diagram of the anaerobic bioconversion of organic matter into methane, including the main involved microbial populations. Bold lines indicate the process without the interference of sulfate reduction; dashed lines indicate possible biochemical pathways associated with the reduction of sulfate into sulfide. Note: The diagram is based on McCarty and Smith [<xref ref-type="bibr" rid="B150-biomass-02-00025">150</xref>] and Chenicharo [<xref ref-type="bibr" rid="B160-biomass-02-00025">160</xref>]. Full article ">Figure 3
Potential technological routes for the exploitation of sugarcane vinasse using biodigestion with phase separation. (↑) means “high values”, while (↓) means “low values”. Full article ">Figure 4
Potential applications for the biogas streams from biodigestion with phase separation. Full article ">Figure 5
Opportunities for inserting biodigestion in 1G sugarcane biorefineries. Notes: a Requires the post-treatment of the effluent, such as concentration, blending with other residual streams (e.g., filter cake), and mineral supplementation. b Aims to reduce the recalcitrance of the lignocellulosic materials. c Composed of pentoses and hexoses. d Requires the post-treatment of the digestate, such as mineral supplementation. Full article ">

16 pages, 1137 KiB

Open AccessArticle

Bioenergy, Electricity, Biogas Production, and Emission Reduction Using the Anaerobic Digestion of Organic Municipal Solid Waste in Campinas, One of the Largest Brazilian Cities

by Lívia Alencar Pacheco, Jenniffer Tamayo-Peña, Bruna de Souza Moraes and Telma Teixeira Franco

Processes 2022, 10(12), 2662; https://doi.org/10.3390/pr10122662 - 10 Dec 2022

Cited by 2 | Viewed by 1812

Abstract

Anaerobic digestion (AD) is an attractive process for bioenergy production and is considered to be an alternative way to reduce landfills. AD improves municipal solid waste (MSW) management, representing a profitable application of the circular economy and could reduce environmental impact. The methane [...] Read more.

Anaerobic digestion (AD) is an attractive process for bioenergy production and is considered to be an alternative way to reduce landfills. AD improves municipal solid waste (MSW) management, representing a profitable application of the circular economy and could reduce environmental impact. The methane (CH₄) potential of four different organic fractions of MSW—paper (PFW), garden (GFW), food (FFW), and a mixture of these three (OFMSW)—via AD was used to investigate the energy potential and the economic and environmental impact of Campinas. Theoretical and experimental biochemical methane potential (BMP) and substrate biodegradability were determined using the Buswell and Müller equation and the VDI 4630 method. The Gompertz model was used to predict the kinetics of the biochemical processes. The highest experimental BMP (410.7 NmLCH₄ gVS⁻¹) and biodegradability (86.6%) were reached with OFMSW. OFMSW can avail an energetic potential of approximately 119 GWh year⁻¹, with a biomethane production equivalent to diesel at 49.9 × 10³ m³ year⁻¹, hence, potentially curtailing the CO₂ emissions of heavy-duty vehicles by almost 133 kt year⁻¹. The electricity demand for approximately 11% of the households in Campinas could be met by the biogas produced by OFMSW, thus increasing local energy security. The replacement of fossil diesel with biomethane to fuel garbage trucks in Campinas could reduce 25% of the diesel demand. Full article

(This article belongs to the Topic Anaerobic Digestion Processes)

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16 pages, 2864 KiB

Open AccessArticle

Metaproteomic Analysis of the Anaerobic Community Involved in the Co-Digestion of Residues from Sugarcane Ethanol Production for Biogas Generation

by Maria Paula. C. Volpi, Larissa O. Magalhães, Flávia V. Winck, Mônica T. V. Labate and Bruna S. Moraes

Biomass 2022, 2(4), 358-373; https://doi.org/10.3390/biomass2040024 - 5 Dec 2022

Cited by 2 | Viewed by 2064

Abstract

The proteomics analysis could contribute to better understand about metabolic pathways in anaerobic digestion community because it still as a “black-box” process. This study aimed to analyze the proteins of the anaerobic co-digestion performed in reactors containing residues from the first and second [...] Read more.

The proteomics analysis could contribute to better understand about metabolic pathways in anaerobic digestion community because it still as a “black-box” process. This study aimed to analyze the proteins of the anaerobic co-digestion performed in reactors containing residues from the first and second generation ethanol production. Metaproteomics analysis was carried out for three types of samples: anaerobic sludge without substrate (SI), semi-continuous stirred reactor (s-CSTR) with co-digestion of filter cake, vinasse, and deacetylation liquor (R-CoAD) and s-CSTR with co-digestion of these aforementioned residues adding Fe₃O₄ nanoparticles (R-NP). The R-CoAD reactor achieved 234 NmLCH₄ gVS⁻¹ and 65% of CH₄ in the biogas, while the R-NP reactor reached 2800 NmLCH₄ gVS⁻¹ and 80% of CH₄. The main proteins found were enolase, xylose isomerase, pyruvate phosphate dikinase, with different proportion in each sample, indicating some change in pathways. However, according to those identified proteins, the main metabolic routes involved in the co-digestion was the syntrophic acetate oxidation coupled with hydrogenotrophic methanogenesis, with the CH₄ production occurring preferentially via CO₂ reduction. These findings contributed to unravel the anaerobic co-digestion at a micromolecular level, and may select a more appropriate inoculum for biogas production according to that residue, reducing reaction time and increasing productivity. Full article

(This article belongs to the Topic Anaerobic Digestion Processes)

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s-CSTR operation scheme and obtaining samples for proteomics analysis. Full article ">Figure 2
Relative abundance of proteins found in each sample. Average of triplicates. SI: seed inoculum, R-NP: Nanoparticle’s reactor, R-CoAD: Co-digestion reactor. Full article ">Figure 3
Relative abundance and distribution of identified proteins assigned to bacterial and archaea in each sample. Average of triplicates. SI: seed inoculum, R-NP: Nanoparticle’s reactor, R-CoAD: Co-digestion reactor. Full article ">Figure 4
(<bold>A</bold>) Hierarchical clustering analysis of the abundance profiles of the identified 139 proteins. The nine columns represent triplicates of different treatments (SI, R-CoAD and R-NP). The rows represent individual proteins. The more and less abundant proteins are, respectively, shown in orange and blue. The intensity of color increases with increased abundance differences, as shown in the bar. (<bold>B</bold>) Functional categories of clusters originated in (<bold>A</bold>). The two different clusters were analyzed using BlastKOALA and are comparatively shown as a bar chart. (<bold>C</bold>) Molecular functions of samples, according to UniProtKB ontology (GO) gene classification. Full article ">Figure 4 Cont.
(<bold>A</bold>) Hierarchical clustering analysis of the abundance profiles of the identified 139 proteins. The nine columns represent triplicates of different treatments (SI, R-CoAD and R-NP). The rows represent individual proteins. The more and less abundant proteins are, respectively, shown in orange and blue. The intensity of color increases with increased abundance differences, as shown in the bar. (<bold>B</bold>) Functional categories of clusters originated in (<bold>A</bold>). The two different clusters were analyzed using BlastKOALA and are comparatively shown as a bar chart. (<bold>C</bold>) Molecular functions of samples, according to UniProtKB ontology (GO) gene classification. Full article ">Figure 5
General proposed map of the metabolic pathways for 3 samples. SI: seed inoculum, R-NP: Nanoparticle’s reactor, R-CoAD: Co-digestion reactor. The red enzymes were detected in process. The white background is the metabolic maps for all samples, the light orange background maps are found for the sample R-NP and R-CoAD, and the map with a gray background is found in sample SI. Full article ">

15 pages, 2573 KiB

Open AccessFeature PaperArticle

Microwave-Hydrogen Peroxide Assisted Anaerobic Treatment as an Effective Method for Short-Chain Fatty Acids Production from Tannery Sludge

by Giulia Adele Tuci, Francesco Valentino, Edoardo Bonato, Paolo Pavan and Marco Gottardo

Processes 2022, 10(11), 2167; https://doi.org/10.3390/pr10112167 - 23 Oct 2022

Cited by 7 | Viewed by 1658

Abstract

Tannery sludge is disposed of in landfills as it is considered a special residue by the Italian legislation, creating pollution and waste. This paper aims at evaluating the performance of the anaerobic fermentation process to obtain short-chain fatty acids (SCFAs) from this waste. [...] Read more.

Tannery sludge is disposed of in landfills as it is considered a special residue by the Italian legislation, creating pollution and waste. This paper aims at evaluating the performance of the anaerobic fermentation process to obtain short-chain fatty acids (SCFAs) from this waste. The assessment of the most appropriate conditions, in terms of pH, temperature, initial total solids (TSs) content, and application of oxidizing-thermal pretreatment has been developed. The batch test trials revealed that the combined microwave and hydrogen peroxide (MW-H₂O₂) pretreatment followed by thermophilic conditions gave the best results, in terms of the acidification yield (0.31 gCOD_SCFA/gVS₀) and maximal SCFA concentration (above 26 g COD_SCFA/L). In the tests conducted without pretreatment, the mesophilic temperature should be preferred since the acidification performances were comparable to or even better than their thermophilic counterparts. The SCFA composition analysis showed that in mesophilic fermentation, tannery sludge can generate up to 50% acetic acid (COD_Ac/COD_SCFA), if previously pretreated (MW-H₂O₂). This research acts as a forerunner for the appropriate handling of this resource, to employ it for the development of a new tannery industry focused on a circular approach, rather than to simply dispose of it in landfills. Full article

(This article belongs to the Topic Anaerobic Digestion Processes)

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SCFA concentration trends (g COD/L) in the mesophilic batch test M8 (a); mesophilic batch test M12 (b); mesophilic batch test M8-P (c). All three series under the initial pH of 5.0, 7.0, 9.0, and 11.0. Full article ">Figure 2
SCFA concentration trends (g COD/L) in the thermophilic batch test T8 (a); thermophilic batch test T12 (b); thermophilic batch test T8-P (c). All three series under the initial pH of 5.0, 7.0, 9.0, and 11.0. Full article ">Figure 3
SCFAs/CODSOL ratio (COD/COD) of the mesophilic batch series M8, M12, and M8-P under the initial pH 5.0, 7.0, 9.0, and 11.0 (a); SCFAs/CODSOL ratio (COD/COD) of the thermophilic batch series T8, T12, and T8-P under the initial pH 5.0, 7.0, 9.0, and 11.0 (b). Full article ">Figure 4
Fermentation yield values (YF; g CODSCFA/g VS0) in the mesophilic batch series M8, M12, and M8-P (a); fermentation yield values (YF; g CODSCFA/g VS0) in the thermophilic batch series T8, T12, and T8-P (b). Full article ">Figure 5
Composition in terms of the CODSOL percentage of the SCFAs obtained from the mesophilic batch series M8 (a), M12 (b), and M8-P (c) as the average of all the initial pH. Full article ">Figure 6
Composition in terms of the CODSOL percentage of the SCFAs obtained from the thermophilic batch series T8 (a), T12 (b), and T8-P (c) as the average of all the initial pH. Full article ">

10 pages, 1271 KiB

Open AccessArticle

Enhancement of Biogas Production in Anaerobic Digestion Using Microbial Electrolysis Cell Seed Sludge

by Myoung Eun Lee, Yongtae Ahn, Seung Gu Shin and Jae Woo Chung

Energies 2022, 15(19), 7042; https://doi.org/10.3390/en15197042 - 25 Sep 2022

Cited by 3 | Viewed by 2129

Abstract

Anaerobic digestion (AD) can produce renewable energy and reduce carbon emissions, but the energy conversion efficiency is still limited in some waste streams. This study tested the effect of applied voltage removal for microbial electrolysis cells (MECs) treating primary sewage sludge. Two MECs [...] Read more.

Anaerobic digestion (AD) can produce renewable energy and reduce carbon emissions, but the energy conversion efficiency is still limited in some waste streams. This study tested the effect of applied voltage removal for microbial electrolysis cells (MECs) treating primary sewage sludge. Two MECs were operated in parallel: a MEC-0.3 V with an applied voltage of 0.3 V and a MEC-OCV with open circuit voltage. Both reactors were inoculated with seed sludge originating from a MEC at 0.3 V applied voltage, and three batch cycles were operated for 36 d. The methane production of the MEC-OCV was 3759 mL/L in the first cycle and 2759 mL/L in the second cycle, which was similar (105% and 103%, respectively) to that of the MEC-0.3 V. However, in the third cycle, the methane production of the MEC-OCV (1762 mL/L) was 38.8% lower than that of the MEC-0.3 V (4545 mL/L). The methane contents in the biogas were 68.6–74.2% from the MEC-OCV, comparable to those from the MEC-0.3 V (66.6–71.1%). These results indicate that not only the MEC-0.3V but also the MEC-OCV outperformed AD in terms of methane yield and productivity, and the promotion using MEC-derived inoculum persisted equally with the MEC-OCV for two batch cycles after removing the applied voltage. Therefore, a MEC operation with cycled power supply may be beneficial in reducing the electric energy usage and improving the biogas production performance, compared to conventional AD. Full article

(This article belongs to the Topic Anaerobic Digestion Processes)

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15 pages, 1686 KiB

Open AccessFeature PaperArticle

Flexibility as the Key to Stability: Optimization of Temperature and Gas Feed during Downtime towards Effective Integration of Biomethanation in an Intermittent Energy System

by Brian Dahl Jønson, Lars Ole Lykke Mortensen, Jens Ejbye Schmidt, Martin Jeppesen and Juan-Rodrigo Bastidas-Oyanedel

Energies 2022, 15(16), 5827; https://doi.org/10.3390/en15165827 - 11 Aug 2022

Cited by 7 | Viewed by 2507

Abstract

Biological methanation is the production of CH₄ from CO₂ and H₂. While this approach to carbon capture utilization have been widely researched in the recent years, there is a gap in the technology. The gap is towards the flexibility [...] Read more.

Biological methanation is the production of CH₄ from CO₂ and H₂. While this approach to carbon capture utilization have been widely researched in the recent years, there is a gap in the technology. The gap is towards the flexibility in biomethanation, utilizing biological trickling filters (BTF). With the current intermittent energy system, electricity is not a given surplus energy which will interfere with a continuous operation of biomethanation and will result in periods of operational downtime. This study investigated the effect of temperature and H₂ supply during downtimes, to optimize the time needed to regain initial performance. Short (6 h), medium (24 h) and long (72 h) downtimes were investigated with combinations of three different temperatures and three different flow rates. The results from these 27 experiments showed that with the optimized parameters, it would take 60 min to reach 98.4% CH₄ in the product gas for a short downtime, whereas longer downtimes needed 180 min to reach 91.0% CH₄. With these results, the flexibility of biomethanation in BTFs have been proven feasible. This study shows that biomethanation in BTFs can be integrated into any intermittent energy system and thereby is a feasible Power-2-X technology. Full article

(This article belongs to the Topic Anaerobic Digestion Processes)

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Illustration of the variation in electricity spot prices. (a) A representation of the electricity spot price variation that can occur during a full calendar year. (b) Variation that can occur during a 24-h period. Data used for this figure was from Nord Pool [<a href="#B16-energies-15-05827" class="html-bibr">16</a>]. Full article ">Figure 2
Grouped electrical spot prices for 2020, with overview of periods with consecutive too high electrical price, compared to preset limit, to find downtime lengths that needs investigation. (a) Grouping of electrical spot prices. Blocks indicate the number of periods with that number of periods within that grouping. Line indicates the accumulative number of hours from the number of periods in that hour range. (b) Experimental overview for each length of downtime. The influence of temperature and gas flow gave 9 combinations for each downtime length. Full article ">Figure 3
Examples of the drop-, lag phase-, and decrease-tendency observed of product gas quality after start of refeeding. Illustrating the effect of the parameters set during downtime have on the product gas after refeed initiation. Each line represents an experiment for a certain downtime length. (a) Short downtime of 6 h at 32 °C and 10% flow; (b) Long downtime of 72 h at 32 °C with 0% flow; (c) Medium downtime of 24 h at 12 °C with 0% flow; (d) Long downtime of 72 h at 52 °C with 0% flow. Full article ">Figure 4
CH4-% in product gas in relation to the effect of the parameters set during downtime lengths for three specific times after initiation of refeeding strategy. The contour plots are divided into three graphs for each downtime length; left graph (6 h), middle graph (24 h) and right graph (72 h). (--) Target product gas quality of 95.4% CH4. Product gasses are shown for periods of (a) 120 min after initiating the refeed of the BTFs; (b) 180 min after initiating the refeed of the BTFs. Full article ">

11 pages, 886 KiB

Open AccessReview

Enhancement of Anaerobic Digestion with Nanomaterials: A Mini Review

by Raquel Barrena, Javier Moral-Vico, Xavier Font and Antoni Sánchez

Energies 2022, 15(14), 5087; https://doi.org/10.3390/en15145087 - 12 Jul 2022

Cited by 10 | Viewed by 2219

Abstract

In recent years, the number of articles reporting the addition of nanomaterials to enhance the process of anaerobic digestion has exponentially increased. The benefits of this addition can be observed from different aspects: an increase in biogas production, enrichment of methane in biogas, [...] Read more.

In recent years, the number of articles reporting the addition of nanomaterials to enhance the process of anaerobic digestion has exponentially increased. The benefits of this addition can be observed from different aspects: an increase in biogas production, enrichment of methane in biogas, elimination of foaming problems, a more stable and robust operation, absence of inhibition problems, etc. In the literature, one of the current focuses of research on this topic is the mechanism responsible for this enhancement. In this sense, several hypotheses have been formulated, with the effect on the redox potential caused by nanoparticles probably being the most accepted, although supplementation with trace materials coming from nanomaterials and the changes in microbial populations have been also highlighted. The types of nanomaterials tested for the improvement of anaerobic digestion is today very diverse, although metallic and, especially, iron-based nanoparticles, are the most frequently used. In this paper, the abovementioned aspects are systematically reviewed. Another challenge that is treated is the lack of works reported in the continuous mode of operation, which hampers the commercial use of nanoparticles in full-scale anaerobic digesters. Full article

(This article belongs to the Topic Anaerobic Digestion Processes)

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12 pages, 2596 KiB

Open AccessArticle

Hydrogen Production by the Thermophilic Dry Anaerobic Co-Fermentation of Food Waste Utilizing Garden Waste or Kitchen Waste as Co-Substrate

by Na Wang, Chunmeng Chui, Siying Zhang, Qianjing Liu, Baoguo Li, Jiping Shi and Li Liu

Sustainability 2022, 14(12), 7367; https://doi.org/10.3390/su14127367 - 16 Jun 2022

Cited by 10 | Viewed by 2491

Abstract

Multicomponent collaborative anaerobic fermentation has been considered a promising technology for treating perishable organic solid wastes and producing clean energy. This study evaluated the potential of hydrogen production by thermophilic dry anaerobic co-fermentation of food waste (FW) with garden waste (GW) or kitchen [...] Read more.

Multicomponent collaborative anaerobic fermentation has been considered a promising technology for treating perishable organic solid wastes and producing clean energy. This study evaluated the potential of hydrogen production by thermophilic dry anaerobic co-fermentation of food waste (FW) with garden waste (GW) or kitchen waste (KW) as co-substrate. The results showed that when the ratio of FW to GW was 60:40, the maximum cumulative hydrogen production and organic matter removal rate reached 85.28 NmL g⁻¹ VS and 63.29%, respectively. When the ratio of FW to KW was 80:20, the maximum cumulative hydrogen production and organic matter removal rate reached 81.31 NmL g⁻¹ VS and 61.91%, respectively. These findings suggest that thermophilic dry anaerobic co-fermentation of FW using GW or KW as co-substrate has a greater potential than single-substrate fermentation to improve hydrogen production and the organic matter removal rate. Full article

(This article belongs to the Topic Anaerobic Digestion Processes)

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Cumulative hydrogen production for the thermophilic dry anaerobic co-fermentation of (a) FW + GW and (b) FW + KW. Full article ">Figure 2
Cumulative hydrogen production on the 30th day for the thermophilic dry anaerobic co-fermentation of (a) FW + GW and (b) FW + KW. Letters indicate significant differences between the different mixing ratios (p < 0.05). Full article ">Figure 3
Daily hydrogen production for the thermophilic dry anaerobic co-fermentation of (a) FW + GW and (b) FW + KW. Full article ">Figure 4
Changes in the VS contents for the thermophilic dry anaerobic co-fermentation of (a) FW + GW and (b) FW + KW. Letters indicate significant differences between the different mixing ratios (p < 0.05). Full article ">Figure 5
Changes in the TS contents for the thermophilic dry anaerobic co-fermentation of (a) FW + GW and (b) FW + KW. Letters indicate significant differences between the different mixing ratios (p < 0.05). Full article ">Figure 6
Organic matter removal rates for the thermophilic dry anaerobic co-fermentation of (a) FW + GW and (b) FW + KW. Letters indicate significant differences between the different mixing ratios (p < 0.05). Full article ">Figure 7
C/N ratios for the thermophilic dry anaerobic co-fermentation of (a) FW + GW and (b) FW + KW. Full article ">

15 pages, 2985 KiB

Open AccessArticle

Continuous Production of Volatile Fatty Acids (VFAs) from Swine Manure: Determination of Process Conditions, VFAs Composition Distribution and Fermentation Broth Availability Analysis

by Zhiwei Wang, Weiwu Wang, Ping Li, Yaping Leng and Jinhua Wu

Water 2022, 14(12), 1935; https://doi.org/10.3390/w14121935 - 16 Jun 2022

Cited by 1 | Viewed by 2528

Abstract

For pollution control and waste utilization, a promising future direction is to obtain high-value carbon sources from organic waste. In this experiment, swine manure was efficiently converted into high concentration volatile fatty acids through continuous hydrolysis-acidification bioreactors. This study determined the process conditions, [...] Read more.

For pollution control and waste utilization, a promising future direction is to obtain high-value carbon sources from organic waste. In this experiment, swine manure was efficiently converted into high concentration volatile fatty acids through continuous hydrolysis-acidification bioreactors. This study determined the process conditions, the composition distribution of volatile fatty acids and the availability of fermentation broth. The results showed that the reactor with a hydraulic retention time of 1.5 days had the optimal production performance of volatile fatty acids. The highest hydrolysis degree (62.2%) and acidification degree (42.5%) were realized in this reactor at the influent soluble chemical oxygen demand of 5460 mg/L. Furthermore, when the influent soluble chemical oxygen demand was 7660 mg/L, volatile fatty acids of 6065 mg-COD/L could be produced stably, and the proportion of volatile fatty acids in soluble chemical oxygen demand was the largest (75%). Additionally, the fermentation broth rich in volatile fatty acids could be applied to deep nitrogen and phosphorus removal. This work provides a productive approach to resource recovery from swine manure. Full article

(This article belongs to the Topic Anaerobic Digestion Processes)

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17 pages, 2140 KiB

Open AccessArticle

Composition Characterization and Transformation Mechanism of Dissolved Organic Matters in a Full-Scale Membrane Bioreactor Treating Co-Digestion Wastewater of Food Waste and Sewage Sludge

by Ying Zhou, Shuohui Shi, Jiong Zhou, Lei He, Xuejie He, Yang Lu, Qiang He and Jian Zhou

Sustainability 2022, 14(11), 6556; https://doi.org/10.3390/su14116556 - 27 May 2022

Cited by 1 | Viewed by 1801

Abstract

The membrane bioreactor (MBR) serves as the most widely used technology in anaerobic digestion wastewater treatment, but the composition and transformation of the dissolved organic matters (DOMs) are vague. This study focused on the composition characterization and transformation mechanism of DOMs in real [...] Read more.

The membrane bioreactor (MBR) serves as the most widely used technology in anaerobic digestion wastewater treatment, but the composition and transformation of the dissolved organic matters (DOMs) are vague. This study focused on the composition characterization and transformation mechanism of DOMs in real co-digestion wastewater of food waste and sewage sludge from a full-scale MBR via molecular weight cut-off, 3D-EEM, FT-IR, and SPME-GC/MS. The results indicated that the co-digestion wastewater mainly comprised organics with molecular weight (MW) lower than 1 kDa and dominated by tryptophane-protein-like substances. The hydrolytic/acidogenic process improved the biodegradability with the conversion of high-MW organics into low-MW organics, while the two-stage A/O process possessed the highest contribution to the organic removal with the consumption of most DOMs. However, the deficient removal of refractory organics (MW < 5 kDa) in the ultrafiltration unit led to the residual DOMs in the effluent. The potential functional bacteria in the biological processes have also been identified and were principally affiliated with Proteobacteria and Firmicutes. These findings could help to advance the understanding of the co-digestion wastewater and provide fundamental information for the optimization and development of MBR in anaerobic digestion wastewater treatment. Full article

(This article belongs to the Topic Anaerobic Digestion Processes)

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14 pages, 2509 KiB

Open AccessArticle

Effects of Increasing Concentrations of Enrofloxacin on Co-Digestion of Pig Manure and Corn Straw

by Qihang Shu, Hongkuan Cheng, Xiaxia Chen, Jie Wang, Zunqing Du, Jun Hong, Zheng Zheng and Xingzhang Luo

Sustainability 2022, 14(10), 5894; https://doi.org/10.3390/su14105894 - 12 May 2022

Cited by 1 | Viewed by 1616

Abstract

Enrofloxacin (ENR) is one of the most commonly used antibiotics in pig farms. In this study, using fresh pig manure and corn straw powder as substrates, the effects of different concentrations of ENR (2.5, 10, and 20 mg/L) on anaerobic digestion in completely [...] Read more.

Enrofloxacin (ENR) is one of the most commonly used antibiotics in pig farms. In this study, using fresh pig manure and corn straw powder as substrates, the effects of different concentrations of ENR (2.5, 10, and 20 mg/L) on anaerobic digestion in completely mixed anaerobic reactors were investigated. A relatively low concentration of ENR (2.5 mg/L) increased methane production by 47.58% compared with the control group. Among the volatile fatty acids (VFAs) in the reactors, the propionic acid content was the lowest, and the concentrations of acetic acid kinase and coenzyme F420 were highest in the first seven days during peak gas production. However, methane production in the reactors with 10 mg/L and 20 mg/L ENR decreased by 8.59% and 20.25%, respectively. Furthermore, the accelerated hydrolysis of extracellular polymeric substances causes a significant accumulation of VFA levels. The microbial community in anaerobic reactors was analyzed by 16S rRNA sequencing. Proteiniphilum was the dominant bacterial genus. In addition, ENR at 2.5 mg/L effectively increased the abundance and diversity of anaerobic microorganisms, whereas a high concentration of ENR (10 and 20 mg/L) significantly decreased these parameters. This study demonstrated that different concentrations of ENR had significantly different effects on anaerobic digestion. Full article

(This article belongs to the Topic Anaerobic Digestion Processes)

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Effect of R1 (Control group), R2 (with 2.5 mg/L ENR addition), R3 (with 10 mg/L ENR addition), and R4 (with 20 mg/L ENR addition) on (a) daily CH4 yield; (b) cumulative CH4 yield and the line used to fit the modified Gompertz equation. Full article ">Figure 2
Changes of volatile fatty acids (VFAs) components in (a) R1 (Control group); (b) R2 (with 2.5 mg/L ENR addition); (c) R3 (with 10 mg/L ENR addition); (d) R4 (with 20 mg/L ENR addition). Full article ">Figure 3
Changes in (a) pH and (b) total ammoniacal nitrogen (TAN) of R1 (control group); R2 (with 2.5 mg/L ENR addition); R3 (with 10 mg/L ENR addition); R4 (with 20 mg/L ENR addition). Full article ">Figure 4
Changes in total organic carbon (a) (TOC) concentration (days 1–3); (b) TOC concentration (days 1–30); (c) protein concentration (days 1–3); (d) polysaccharide concentration (days 1–3), and (e) concentration of protein and propionic acid (day 3) in four groups. (a, b in (a,c–e) indicate whether there is a significant difference). Full article ">Figure 5
Microbial community analysis: (a) Venn diagram of the distribution of OTUs in different groups, and (b) percent of community abundance on genus level. Full article ">Figure 6
Changes of coenzymes throughout the reaction: (a) acetic acid kinase (ACK); (b) F420. Full article ">

9 pages, 1458 KiB

Open AccessArticle

Substrate Characteristics Fluctuations in Full-Scale Anaerobic Digesters Treating Food Waste at Marginal Organic Loading Rates: A Case Study

by Seung Gu Shin, Sang Hyeok Park and Seokhwan Hwang

Energies 2022, 15(9), 3471; https://doi.org/10.3390/en15093471 - 9 May 2022

Cited by 3 | Viewed by 1901

Abstract

The design of a full-scale bioprocess is typically based on parameters derived from smaller-scale experiments from a previous study. However, disagreements often occur at up-scaling of waste-to-energy processes due to the fluctuations of the substrate characteristics, etc. Therefore, once a commercial-scale waste digester [...] Read more.

The design of a full-scale bioprocess is typically based on parameters derived from smaller-scale experiments from a previous study. However, disagreements often occur at up-scaling of waste-to-energy processes due to the fluctuations of the substrate characteristics, etc. Therefore, once a commercial-scale waste digester has been built and operated, it is essential to test if the performance of the process agrees with its design value; during this process, fluctuations might occur in digesters operated at marginal organic loading rates. In this study, triplicate full-scale anaerobic digesters treating food waste were monitored for five months. The digesters, operated at the design feeding ratio, showed increasing volatile fatty acid (VFA) trends (per total alkalinity) due to a 30% higher chemical oxygen demand of the influent, than the design. The organic loading rate was adjusted on a daily basis until a stable performance was observed. Significant shifts of methanogen populations from Methanobacteriales to Methanomicrobiales and Methanosarcinales were observed during the stable operation period. Full article

(This article belongs to the Topic Anaerobic Digestion Processes)

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Full article ">Figure 1
The schematic diagram of the system. 1, FW transportation; 2, FW storage tank; 3, pretreatment system to remove indigestible parts and to add some water; 4, storage tank; 5, pre-acidification tank; 6, triplicate digesters; 7, digestate storage tank; 8, solid-liquid separator; 9, composter; 10, wastewater treatment system; 11, gas flowmeter; 12, biogas storage tank; 13, biogas purification and utilization system. Black and green arrows indicate mass and gas flows, respectively. Full article ">Figure 2
Profiles of selected operational parameters for the full-scale digesters: (a) daily feeding and biogas production, (b) chemical oxygen demand (COD), and (c) organic loading rate (OLR). Dotted lines represent design values for daily feeding, input COD, and OLR. Full article ">Figure 3
Profiles of selected indicator parameters for the full-scale digesters: (a) pH, (b) total alkalinity, and (c) ethanol and volatile fatty acids (summed). Ethanol was only detected in the influent. Full article ">Figure 4
Profiles of 16S rRNA gene concentrations for the full-scale digesters: (a) digester A, (b) digester B, and (c) digester C. Abbreviations: ARC, total archaea; MBT, Methanobacteriales; MMB, Methanomicrobiales; MSL, Methanosarcinales. Full article ">

15 pages, 4982 KiB

Open AccessArticle

Monitoring the Process of Anaerobic Digestion of Native and Microwave Pre-Treated Sludge by Dielectric and Rheological Measurements

by Zoltán Jákói, Cecilia Hodúr and Sándor Beszédes

Water 2022, 14(8), 1294; https://doi.org/10.3390/w14081294 - 15 Apr 2022

Cited by 6 | Viewed by 2377

Abstract

The anaerobic digestion (AD) of wastewater sludge presents a promising and efficient method of wastewater and sludge treatment, as it can lower the organic content of sludge while producing a renewable source of energy—biogas—at the same time. However, using native, non-treated industrial wastewater [...] Read more.

The anaerobic digestion (AD) of wastewater sludge presents a promising and efficient method of wastewater and sludge treatment, as it can lower the organic content of sludge while producing a renewable source of energy—biogas—at the same time. However, using native, non-treated industrial wastewater sludge as a substrate for AD may present difficulties, hence we focused our research primarily on the applicability of measuring techniques—viscosity and dielectric measurement. One of our research goals was to investigate the presence of any connection between the aforementioned properties and the overall biogas production, in order to prove whether these measurement techniques were capable of monitoring the process of AD. Our other aim was to investigate how microwave (MW) pre-treatment affected the anaerobic fermentation. Our results revealed that in terms of total biogas yield, microwave irradiation could enhance fermentation by 14%, and also reduced the viscosity of the fermentation media by 13%. However, microwave irradiation did not change the overall tendencies of the AD process regarding these aspects. Moreover, it was discovered that dielectric and absolute viscosity measurements were effective methods for monitoring the fermentation. Additionally, a correlation was found between the accumulating biogas yield, the dielectric constant and loss factor, and the absolute viscosity of the digested media—each of these share a similarity in tendency and can indicate the occurrence of different phases during batch anaerobic fermentation. Full article

(This article belongs to the Topic Anaerobic Digestion Processes)

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16 pages, 2900 KiB

Open AccessArticle

High Salinity Wastewater Treatment Study Using an Automated Pilot Combining Anaerobic and Aerobic Biofilm Processes

by Anirudh Nelabhotla, Ilya Savva, Jens Tarjei Jensen and Shuai Wang

Processes 2022, 10(4), 766; https://doi.org/10.3390/pr10040766 - 13 Apr 2022

Cited by 3 | Viewed by 2657

Abstract

A 20-ft containerized biological pilot system consisting of both an anaerobic expended granular sludge bed (EGSB) and an aerobic biofilm continuous flow intermittent clean (CFIC^®) system has been designed, constructed, and delivered onsite at a pharmaceutical wastewater producer for a wastewater [...] Read more.

A 20-ft containerized biological pilot system consisting of both an anaerobic expended granular sludge bed (EGSB) and an aerobic biofilm continuous flow intermittent clean (CFIC^®) system has been designed, constructed, and delivered onsite at a pharmaceutical wastewater producer for a wastewater treatment study. The pilot was operated for a total of 317 days, including 147 days of adaptive phase and 170 days of testing phase. A pilot adaptive phase feeding wastewater COD concentration from 2 to 50 g/L with salinity up to 16 g/L was carried out, achieving EGSB where COD removal reached over 80 to 95% at OLR up to 22 kg COD/m³·d. In the testing phase, with repressive practical wastewater, the EGSB can remove over 97% of feed COD (with up to 82% acetic acid) at an average 16.3 kg COD/m³·d. The high wastewater salinity at 20 g/L did not inhibit COD removal efficiency by the system. The complete system with EGSB and aerobic stage was very stable and removed over 90–97% of the total COD dependent on the wastewater composition. The pilot was demonstrated as a valuable tool because of its user-friendly nature with high automation level, as well as its high efficiency in treating specific wastewater under varying operational conditions. This study provides critical information for full-scale system design and offers training for the customer in handling a previously unfamiliar process in a confident manner. Full article

(This article belongs to the Topic Anaerobic Digestion Processes)

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22 pages, 1318 KiB

Open AccessArticle

Physico-Chemical and Metagenomic Profile Analyses of Animal Manures Routinely Used as Inocula in Anaerobic Digestion for Biogas Production

by Asheal Mutungwazi, Grace N. Ijoma, Henry J. O. Ogola and Tonderayi S. Matambo

Microorganisms 2022, 10(4), 671; https://doi.org/10.3390/microorganisms10040671 - 22 Mar 2022

Cited by 15 | Viewed by 3677

Abstract

Anaerobic digestion (AD) of organic waste is considered a sustainable solution to energy shortage and waste management challenges. The process is facilitated by complex communities of micro-organisms, yet most wastes do not have these and thus need microbial inoculation using animal manures to [...] Read more.

Anaerobic digestion (AD) of organic waste is considered a sustainable solution to energy shortage and waste management challenges. The process is facilitated by complex communities of micro-organisms, yet most wastes do not have these and thus need microbial inoculation using animal manures to initiate the process. However, the degradation efficiency and methane yield achieved in using different inocula vary due to their different microbial diversities. This study used metagenomics tools to compare the autochthonous microbial composition of cow, pig, chicken, and horse manures commonly used for biogas production. Cows exhibited the highest carbon utilisation (>30%) and showed a carbon to nitrogen ratio (C/N) favourable for microbial growth. Pigs showed the least nitrogen utilisation (<3%) which explains their low C/N whilst horses showed the highest nitrogen utilisation (>40%), which explains its high C/N above the optimal range of 20–30 for efficient AD. Manures from animals with similar gastrointestinal tract (GIT) physiologies were observed to largely harbour similar microbial communities. Conversely, some samples from animals with different GITs also shared common microbial communities plausibly because of similar diets and rearing conditions. Insights from this study will lay a foundation upon which in-depth studies of AD metabolic pathways and strategies to boost methane production through efficient catalysis can be derived. Full article

(This article belongs to the Topic Anaerobic Digestion Processes)

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20 pages, 3477 KiB

Open AccessArticle

Methods of Handling the Cup Plant (Silphium perfoliatum L.) for Energy Production

by Kamil Witaszek, Marcin Herkowiak, Agnieszka A. Pilarska and Wojciech Czekała

Energies 2022, 15(5), 1897; https://doi.org/10.3390/en15051897 - 4 Mar 2022

Cited by 8 | Viewed by 2282

Abstract

The aim of the study was to determine the possibilities of using cup plants (Silphium perfoliatum L.) to generate energy. The energy balances of the combustion and anaerobic digestion were compared. The research showed that cup plants could be used as a [...] Read more.

The aim of the study was to determine the possibilities of using cup plants (Silphium perfoliatum L.) to generate energy. The energy balances of the combustion and anaerobic digestion were compared. The research showed that cup plants could be used as a raw material for solid fuel and for anaerobic digestion. An energy balance simulation showed that electricity could be generated through the anaerobic digestion of cup plants. The following amounts could be generated in the anaerobic digestion process: 1069 kWhe from 1 Mg of the raw material fragmented with an impact mill, 738.8 kWhe from 1 Mg of the raw material extruded at a temperature of 150 °C, and as much as 850.1 kWhe from 1 Mg of the raw material extruded at 175 °C. The energy balance of the combustion of biofuel in the form of cup plant pellets showed that 858.28 kWht could be generated from 1 Mg of the raw material. The combustion of solid biofuel generated a relatively low amount of heat in comparison with the expected amount of heat from a biogas-powered cogeneration system due to the high energy consumption of the processes of drying and agglomeration of the raw material for the production of pellets. Full article

(This article belongs to the Topic Anaerobic Digestion Processes)

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17 pages, 1151 KiB

Open AccessArticle

Metagenomic Analysis of Bacterial Community Structure and Dynamics of a Digestate and a More Stabilized Digestate-Derived Compost from Agricultural Waste

by Stefania Mirela Mang, Vincenzo Trotta, Antonio Scopa and Ippolito Camele

Processes 2022, 10(2), 379; https://doi.org/10.3390/pr10020379 - 16 Feb 2022

Cited by 5 | Viewed by 3630

Abstract

Recycling of different products and waste materials plays a crucial role in circular economy, where the anaerobic digestion (AD) constitutes an important pillar since it reuses nutrients in the form of organic fertilizers. Knowledge about the digestate and compost microbial community structure and [...] Read more.

Recycling of different products and waste materials plays a crucial role in circular economy, where the anaerobic digestion (AD) constitutes an important pillar since it reuses nutrients in the form of organic fertilizers. Knowledge about the digestate and compost microbial community structure and its variations over time is important. The aim of the current study was to investigate the microbiome of a slurry cow digestate produced on a farm (ADG) and of a more stabilized digestate-derived compost (DdC) in order to ascertain their potential uses as organic amendments in agriculture. The results from this study, based on a partial fragment of 16S bacterial rRNA NGS sequencing, showed that there is a greater microbial diversity in the DdC originated from agricultural waste compared to the ADG. Overall, the existence of a higher microbial diversity in the DdC was confirmed by an elevated number (1115) of OTUs identified, compared with the ADG (494 OTUs identified). In the DdC, 74 bacterial orders and 125 families were identified, whereas 27 bacterial orders and 54 families were identified in the ADG. Shannon diversity and Chao1 richness indexes were higher in DdC samples compared to ADG ones (Shannon: 3.014 and 1.573, Chao1: 68 and 24.75; p < 0.001 in both cases). A possible association between the microbiome composition at different stages of composting process and the role that these microorganisms may have on the quality of the compost-like substrate and its future uses is also discussed. Full article

(This article belongs to the Topic Anaerobic Digestion Processes)

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11 pages, 1637 KiB

Open AccessArticle

Energy-Positive Disintegration of Waste Activated Sludge—Full Scale Study

by Monika Zubrowska-Sudol, Katarzyna Sytek-Szmeichel, Piotr Krawczyk and Agnieszka Bisak

Energies 2022, 15(2), 555; https://doi.org/10.3390/en15020555 - 13 Jan 2022

Cited by 6 | Viewed by 1769

Abstract

This study aimed to evaluate the effects of mechanical disintegration of waste activated sludge (WAS) on full scale anaerobic digestion, considering the possibility of obtaining a positive energy balance. The results showed that an increase in energy density (ε_L) used in [...] Read more.

This study aimed to evaluate the effects of mechanical disintegration of waste activated sludge (WAS) on full scale anaerobic digestion, considering the possibility of obtaining a positive energy balance. The results showed that an increase in energy density (ε_L) used in disintegration was accompanied by an increase in the release of organic compounds from sludge (SCOD increased from 211 ± 125 mg O₂/L for ε_L = 0 kJ/L to 6292 ± 2860 mgO₂/L for ε_L = 180 kJ/L). Some of them were volatile fatty acids. The percentage share of WAS subject to disintegration was also documented as a crucial parameter affecting the efficiency of biogas production. An increase in the value of this parameter from 25% to 100%, even at much lower ε_L used in disintegration (therefore with much smaller amounts of organic compounds released from sludge flocs) resulted in an increase in biogas production. Conducting disintegration of the entire stream of WAS directed to the fermentation tank at ε_L 30 kJ/L resulted in an increase in biogas production by 14.1%. Such a surplus would allow production of approximately 360 kWh/d net electricity. Mechanical disintegration of thickened WAS therefore may be an economically justifiable strategy for the intensification of anaerobic sludge stabilisation. Full article

(This article belongs to the Topic Anaerobic Digestion Processes)

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16 pages, 2937 KiB

Open AccessFeature PaperReview

Hydrogen Production from Biomass and Organic Waste Using Dark Fermentation: An Analysis of Literature Data on the Effect of Operating Parameters on Process Performance

by Rita Noelle Moussa, Najah Moussa and Davide Dionisi

Processes 2022, 10(1), 156; https://doi.org/10.3390/pr10010156 - 13 Jan 2022

Cited by 30 | Viewed by 5603

Abstract

In the context of hydrogen production from biomass or organic waste with dark fermentation, this study analysed 55 studies (339 experiments) in the literature looking for the effect of operating parameters on the process performance of dark fermentation. The effect of substrate concentration, [...] Read more.

In the context of hydrogen production from biomass or organic waste with dark fermentation, this study analysed 55 studies (339 experiments) in the literature looking for the effect of operating parameters on the process performance of dark fermentation. The effect of substrate concentration, pH, temperature, and residence time on hydrogen yield, productivity, and content in the biogas was analysed. In addition, a linear regression model was developed to also account for the effect of nature and pretreatment of the substrate, inhibition of methanogenesis, and continuous or batch operating mode. The analysis showed that the hydrogen yield was mainly affected by pH and residence time, with the highest yields obtained for low pH and short residence time. High hydrogen productivity was favoured by high feed concentration, short residence time, and low pH. More modest was the effect on the hydrogen content. The mean values of hydrogen yield, productivity, and content were, respectively, 6.49% COD COD⁻¹, 135 mg L⁻¹ d⁻¹, 51% v/v, while 10% of the considered experiments obtained yield, productivity, and content of or higher than 15.55% COD COD⁻¹, 305.16 mg L⁻¹ d⁻¹, 64% v/v. Overall, this study provides insight into how to select the optimum operating conditions to obtain the desired hydrogen production. Full article

(This article belongs to the Topic Anaerobic Digestion Processes)

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Relationships between hydrogen yield and operational parameters: (a,c,e,g) all considered experiments; (b,d,f,h) average values of experiments in each narrow range (width maximum 20%) of the operating parameters (error bars indicate the standard error) with second-order polynomial curve. The polynomial curve is only used to visualise the general trend, without any statistical significance. Full article ">Figure 1 Cont.
Relationships between hydrogen yield and operational parameters: (a,c,e,g) all considered experiments; (b,d,f,h) average values of experiments in each narrow range (width maximum 20%) of the operating parameters (error bars indicate the standard error) with second-order polynomial curve. The polynomial curve is only used to visualise the general trend, without any statistical significance. Full article ">Figure 2
Relationships between hydrogen productivity and operational parameters: (a,c,e,g) all considered experiments; (b,d,f,h) average values of experiments in each narrow range (width maximum 20%) of the operating parameters (error bars indicate the standard error) with second-order polynomial curve. The polynomial curve is only used to visualise the general trend, without any statistical significance. Full article ">Figure 2 Cont.
Relationships between hydrogen productivity and operational parameters: (a,c,e,g) all considered experiments; (b,d,f,h) average values of experiments in each narrow range (width maximum 20%) of the operating parameters (error bars indicate the standard error) with second-order polynomial curve. The polynomial curve is only used to visualise the general trend, without any statistical significance. Full article ">Figure 3
Relationships between hydrogen content in biogas and operating parameters: (a,c,e,g) all the considered experiments; (b,d,f,h) average values of experiments in each narrow range (width maximum 20%) of the operating parameters (error bars indicate the standard error) with second-order polynomial curve. The polynomial curve is only used to visualise the general trend, without any statistical significance. Full article ">Figure 3 Cont.
Relationships between hydrogen content in biogas and operating parameters: (a,c,e,g) all the considered experiments; (b,d,f,h) average values of experiments in each narrow range (width maximum 20%) of the operating parameters (error bars indicate the standard error) with second-order polynomial curve. The polynomial curve is only used to visualise the general trend, without any statistical significance. Full article ">

13 pages, 1423 KiB

Open AccessArticle

Biogas Generation from Maize and Cocksfoot Growing in Degraded Soil Enriched with New Zeolite Substrate

by Mariola Chomczyńska, Małgorzata Pawłowska, Oliwia Szczepaniak and Ewelina Duma

Energies 2022, 15(1), 377; https://doi.org/10.3390/en15010377 - 5 Jan 2022

Cited by 2 | Viewed by 1732

Abstract

Degraded lands are potential areas for obtaining biomass which can serve as an energy source after its conversion into biogas. Thus, the studies on biogas production from maize and cocksfoot biomasses obtained from degraded soil supplemented with additions of new zeolite substrate (Z-ion [...] Read more.

Degraded lands are potential areas for obtaining biomass which can serve as an energy source after its conversion into biogas. Thus, the studies on biogas production from maize and cocksfoot biomasses obtained from degraded soil supplemented with additions of new zeolite substrate (Z-ion as the nutrient carrier) and on arable soil (reference soil) were carried out during batch digestion tests. It was found that the biogas and biomethane potentials and specific energy of the test species growing in degraded soil enriched with Z-ion additions (1% and 5% v/v in the cases of cocksfoot and maize, respectively) did not differ significantly from the values of these parameters that were found for the plants growing in arable soil. The application of Z-ion to the degraded soil (especially in a dose of 5% v/v) resulted in an increase in the nitrogen content and decrease (below the lower optimum value) in the C/N ratio in the plant biomass. However, these changes did not negatively influence the final values of the biogas or methane potentials or the specific energy found for the maize biomass. Therefore, the study results indicated the usefulness of Z-ion substrate for improving the growth conditions for energy crops in degraded soils and, as a consequence, obtaining a plant feedstock suitable for the digestion process. Full article

(This article belongs to the Topic Anaerobic Digestion Processes)

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22 pages, 1413 KiB

Open AccessReview

Recovery of Household Waste by Generation of Biogas as Energy and Compost as Bio-Fertilizer—A Review

by Youssef Benyahya, Abderrahim Fail, Abdelhakim Alali and Mohamed Sadik

Processes 2022, 10(1), 81; https://doi.org/10.3390/pr10010081 - 31 Dec 2021

Cited by 12 | Viewed by 9685

Abstract

Nowadays, organic waste and especially household waste represents a significant global issue due to population growth. The anaerobic digestion (AD) process is an essential operation contributing powerfully to the valorization of organic waste including food waste in terms of renewable energy generation (biogas) [...] Read more.

Nowadays, organic waste and especially household waste represents a significant global issue due to population growth. The anaerobic digestion (AD) process is an essential operation contributing powerfully to the valorization of organic waste including food waste in terms of renewable energy generation (biogas) and the rich-nutrient residue that can be utilized as bio-fertilizer. Thus, this process (AD) allows for good recovery of household waste by generating biogas and compost. However, the AD operation has been affected by several key factors. In this paper, we aim to involve different critical parameters influencing the AD process, including temperature, pH, organic loading rate (OLR), carbon to nitrogen ratio (C/N), and total solid content (TS(%)). Further, the paper highlights the inhibition caused by the excessive accumulation of volatile fatty acids (VFAs) and ammoniac, which exhibits the positive effects of co-digestion, pretreatment methods, and mixing techniques for maintaining process stability and enhancing biogas production. We analyze some current mathematical models explored in the literature, such as distinct generic, non-structural, combined, and kinetic first-order models. Finally, the study discusses challenges, provides some possible solutions, and a future perspective that promises to be a highly useful resource for researchers working in the field of household waste recovery for the generation of biogas. Full article

(This article belongs to the Topic Anaerobic Digestion Processes)

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20 pages, 3359 KiB

Open AccessArticle

Specific Methane Yield of Wetland Biomass in Dry and Wet Fermentation Technologies

by Robert Czubaszek, Agnieszka Wysocka-Czubaszek, Wendelin Wichtmann and Piotr Banaszuk

Energies 2021, 14(24), 8373; https://doi.org/10.3390/en14248373 - 12 Dec 2021

Cited by 16 | Viewed by 3081

Abstract

Our study evaluated the specific methane yield (SMY) of selected wetland species subjected to wet and dry anaerobic digestion: Carex elata All. (CE), a mixture (~50/50) of Carex elata All. and Carex acutiformis L. (CA), Phragmites australis (Cav.) Trin. ex Steud. (PA), Typha [...] Read more.

Our study evaluated the specific methane yield (SMY) of selected wetland species subjected to wet and dry anaerobic digestion: Carex elata All. (CE), a mixture (~50/50) of Carex elata All. and Carex acutiformis L. (CA), Phragmites australis (Cav.) Trin. ex Steud. (PA), Typha latifolia L. (TL) and Phalaris arundinacea L. (PAr). Plants were harvested in late September, and therefore, the study material was characterised by high lignin content. The highest lignin content (36.40 ± 1.04% TS) was observed in TL, while the lowest (16.03 ± 1.54% TS) was found in CA. PAr was characterised by the highest hemicellulose content (37.55 ± 1.04% TS), while the lowest (19.22 ± 1.22% TS) was observed in TL. Cellulose content was comparable in almost all plant species studied and ranged from 25.32 ± 1.48% TS to 29.37 ± 0.87% TS, except in PAr (16.90 ± 1.29% TS). The methane production potential differed significantly among species and anaerobic digestion (AD) technologies. The lowest SMY was observed for CE (121 ± 28 NL kg_VS⁻¹) with dry fermentation (D–F) technology, while the SMY of CA was the highest for both technologies, 275 ± 3 NL kg_VS⁻¹ with wet fermentation (W–F) technology and 228 ± 1 NL kg_VS⁻¹ with D–F technology. The results revealed that paludi-biomass could be used as a substrate in both AD technologies; however, biogas production was more effective for W–F. Nonetheless, the higher methane content in the biogas and the lower energy consumption of technological processes for D–F suggest that the final amount of energy remains similar for both technologies. The yield is critical in energy production by the AD of wetland plants; therefore, a promising source of feedstock for biogas production could be biomass from rewetted and previously drained areas, which are usually more productive than natural habitats. Full article

(This article belongs to the Topic Anaerobic Digestion Processes)

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Specific methane yield (SMY) produced by both types of fermentation: W–F—wet fermentation; D–F—dry fermentation. CE—Carex elata; CA—Carex acutiformis + Carex elata; PA—Phragmites australis; TL—Typha latifolia; PAr—Phalaris arundinacea. Standard errors are shown as vertical bars. Full article ">Figure 2
Percentage of methane in biogas produced by both types of fermentation: W–F—wet fermentation; D–F—dry fermentation. CE—Carex elata; CA—Carex acutiformis + Carex elata; PA—Phragmites australis; TL—Typha latifolia; PAr—Phalaris arundinacea. Standard errors are shown as vertical bars. Full article ">Figure 3
Daily methane production: (a)—wet fermentation; (b)—dry fermentation. CE—Carex elata; CA—Carex acutiformis + Carex elata; PA—Phragmites australis; TL—Typha latifolia; PAr—Phalaris arundinacea. Standard errors are shown as vertical bars. Full article ">Figure 3 Cont.
Daily methane production: (a)—wet fermentation; (b)—dry fermentation. CE—Carex elata; CA—Carex acutiformis + Carex elata; PA—Phragmites australis; TL—Typha latifolia; PAr—Phalaris arundinacea. Standard errors are shown as vertical bars. Full article ">Figure 4
Cumulative methane production: (a)—wet fermentation; (b)—dry fermentation. CE—Carex elata; CA—Carex acutiformis + Carex elata; PA—Phragmites australis; TL—Typha latifolia; PAr—Phalaris arundinacea. Standard errors are shown as vertical bars. The yellow squares and green diamonds indicate T50 and T95, respectively. Full article ">Figure 4 Cont.
Cumulative methane production: (a)—wet fermentation; (b)—dry fermentation. CE—Carex elata; CA—Carex acutiformis + Carex elata; PA—Phragmites australis; TL—Typha latifolia; PAr—Phalaris arundinacea. Standard errors are shown as vertical bars. The yellow squares and green diamonds indicate T50 and T95, respectively. Full article ">Figure 5
Heat supply from biomass combustion: Comparison of less productive and highly productive (paludiculture) habitats. CE—Carex elata; CA—Carex acutiformis + Carex elata; PA—Phragmites australis; TL—Typha latifolia; PAr—Phalaris arundinacea. Full article ">

18 pages, 1866 KiB

Open AccessArticle

Challenges in Treatment of Digestate Liquid Fraction from Biogas Plant. Performance of Nitrogen Removal and Microbial Activity in Activated Sludge Process

by Aleksandra Chuda and Krzysztof Ziemiński

Energies 2021, 14(21), 7321; https://doi.org/10.3390/en14217321 - 4 Nov 2021

Cited by 6 | Viewed by 2962

Abstract

Even thoughdigestate, which is continually generated in anaerobic digestion process, can only be used as fertilizer during the growing season, digestate treatment is still a critical, environmental problem. That is why the present work aims to develop a method to manage digestate in [...] Read more.

Even thoughdigestate, which is continually generated in anaerobic digestion process, can only be used as fertilizer during the growing season, digestate treatment is still a critical, environmental problem. That is why the present work aims to develop a method to manage digestate in agricultural biogas plant in periods when its use as fertilizer is not possible. A lab-scale system for the biological treatment of the digestate liquid fraction using the activated sludge method with a separate denitrification chamber was constructed and tested. The nitrogen load that was added tothe digestate liquid fraction accounted for 78.53% of the total nitrogen load fed into the reactor. External carbon sources, such as acetic acid, as well as flume water and molasses, i.e., wastewater and by-products from a sugar factory, were used to support the denitrification process. The best results were obtained using an acetic acid and COD (Chemical Oxygen Demand)/NO₃–N (Nitrate Nitrogen) ratio of 7.5. The removal efficiency of TN (Total Nitrogen), NH₄–N (Ammonia Nitrogen) and COD was 83.73%, 99.94%, 86.26%, respectively. It was interesting to see results obtained that were similar to those obtained when using flume water and COD/NO₃–N at a ratio of 8.7. This indicates that flume water can be used as an alternative carbon source to intensify biological nitrogen removal from digestate. Full article

(This article belongs to the Topic Anaerobic Digestion Processes)

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23 pages, 9492 KiB

Open AccessArticle

A Low to Medium-Shear Extruded Kibble with Greater Resistant Starch Increased Fecal Oligosaccharides, Butyric Acid, and Other Saccharolytic Fermentation By-Products in Dogs

by Isabella Corsato Alvarenga, Matthew I. Jackson, Dennis E. Jewell and Charles G. Aldrich

Microorganisms 2021, 9(11), 2293; https://doi.org/10.3390/microorganisms9112293 - 4 Nov 2021

Cited by 3 | Viewed by 2073

Abstract

The objective of this study was to assess whether diets with increased resistant starch (RS) had a positive effect on markers of colonic health in dogs. Three identical diets were extruded with high, medium and low shear (HS, MS and LS) to incrementally [...] Read more.

The objective of this study was to assess whether diets with increased resistant starch (RS) had a positive effect on markers of colonic health in dogs. Three identical diets were extruded with high, medium and low shear (HS, MS and LS) to incrementally increase RS, and fed to 24 dogs in a replicated 3 × 3 William’s Latin square design for 28-day periods. Fasting blood and fresh feces were collected on the last week of each period. Fecal quality was maintained among treatments. Gut integrity markers were measured by ELISA. Fecal short-chain fatty acids (SCFAs) were measured by LC MS/MS. In addition, the microbiota of dogs was determined from fresh feces by 16s rRNA high throughput sequencing. Untargeted metabolomics of both feces and serum were determined by UPLC. Data were analyzed using mixed models. There were no treatment effects on satiety hormones or gut integrity markers. Dogs fed LS or MS diets had marginal evidence (p < 0.10) for decreased fecal pH and for higher concentration (p < 0.05) of butyric acid and fecal oligosaccharides, succinate and lactate. Also, dogs fed the MS or LS diets had a shift towards more saccharolytic bacteria. Full article

(This article belongs to the Topic Anaerobic Digestion Processes)

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Figure 1
Relative proportions of stool scores for dogs fed dietary treatments produced at high, medium and low shear diets (n = 23, 24 and 24, respectively). Full article ">Figure 2
Heatmap of fecal saccharides metabolomics of dogs (n = 24) fed diets produced at high, medium and low shear (HS, MS and LS, respectively). Specific analytes were numbered 1 to 26 and grouped as starch derivatives, other sugars, epithelial sugars and energetic metabolism. Estimate treatment means expressed in the Log2 scale were color coded within each metabolite across diets on a color scale. Blue indicates a relative concentration lower than the other treatments, white indicates an intermediate relative concentration, and red indicates a higher relative concentration than the other treatments. Full article ">Figure 3
Fecal lipid metabolism analytes heatmap of dogs (n = 24) fed diets produced at high, medium and low shear (HS, MS and LS, respectively), with each individual group of analytes ((A): MCFA, medium-chain fatty acids; LCSFA, long-chain saturated fatty acids; LCMUFA, long-chain mono-unsaturated fatty acids; LCPUFA, long-chain poly-unsaturated fatty acids. (B): monoacylglycerols and diacylglycerols. (C): primary and secondary components of bile salt metabolism). Log2 values were conditionally formatted within each metabolite across diets on a color scale. Blue indicates a relative concentration lower than the other treatments, white indicates an intermediate relative concentration, and red indicates a higher relative concentration than the other treatments. (A): 1, caproate (6:0); 2, heptanoate (7:0); 3, caprylate (8:0); 4, caprate (10:0); 5, 5-dodecenoate (12:1n7); 6, palmitate (16:0); 7, stearate (18:0); 8, arachidate (20:0); 9, palmitoleate (16:1n7); 10, 10-heptadecenoate (17:1n7); 11, oleate/vaccenate (18:1); 12, 10-nonadecenoate (19:1n9); 13, erucate (22:1n9); 14, hexadecadienoate (16:2n6); 15, hexadecatrienoate (16:3n3); 16, linoleate (18:2n6); 17, stearidonate (18:4n3); 18, docosadienoate (22:2n6); 19, mead acid (20:3n9); 20, adrenate (22:4n6); 21, arachidonate (20:4n6); 22, eicosapentaenoate (EPA; 20:5n3); 23, docosapentaenoate (n6 DPA; 22:5n6); 24, docosahexaenoate (DHA; 22:6n3). (B): 25, 1-palmitoylglycerol (16:0); 26, 2-palmitoylglycerol (16:0); 27, 1-palmitoleoylglycerol (16:1); 28, 2-palmitoleoylglycerol (16:1); 29, 1-heptadecenoylglycerol (17:1); 30, 1-oleoylglycerol (18:1); 31, 2-oleoylglycerol (18:1); 32, 1-linoleoylglycerol (18:2); 33, 2-linoleoylglycerol (18:2); 34, 1-linolenoylglycerol (18:3); 35, palmitoyl-linoleoyl-glycerol (16:0/18:2); 36, palmitoyl-linoleoyl-glycerol (16:0/18:2); 37, diacylglycerol (16:1/18:2 [<a href="#B2-microorganisms-09-02293" class="html-bibr">2</a>], 16:0/18:3 [<a href="#B1-microorganisms-09-02293" class="html-bibr">1</a>]); 38, oleoyl-oleoyl-glycerol (18:1/18:1); 39, oleoyl-linoleoyl-glycerol (18:1/18:2); 40, oleoyl-linoleoyl-glycerol (18:1/18:2); 41, linoleoyl-linoleoyl-glycerol (18:2/18:2); 42, linoleoyl-linoleoyl-glycerol (18:2/18:2); 43, linoleoyl-linolenoyl-glycerol (18:2/18:3); 44, linoleoyl-linolenoyl-glycerol (18:2/18:3); 45, linolenoyl-linolenoyl-glycerol (18:3/18:3). (C): 46, cholate; 47, taurocholate; 48, 12-dehydrocholate; 49, 12-ketolithocholate; 50, 3b-hydroxy-5-cholenoic acid; 51, 3-dehydrodeoxycholate; 52, 6-oxolithocholate; 53, 7alpha-hydroxycholestenone; 54, 7-ketodeoxycholate; 55, dehydrolithocholate; 56, deoxycholate; 57, deoxycholic acid 12-sulfate; 58, hyocholate; 59, isohyodeoxycholate; 60, lithocholate; 61, taurodeoxycholate; 62, ursocholate. * p < 0.05; q < 0.10. Full article ">Figure 4
Serum non-esterified fatty acids heatmap of dogs (n = 24) fed diets produced at high, medium and low shear (HS, MS and LS, respectively), with each individual group of fatty acids (MCFA: medium-chain fatty acids; LCSFA: long-chain saturated fatty acids; LCMUFA, long-chain mono-unsaturated fatty acids; LCPUFA, long-chain poly-unsaturated fatty acids). Log2 values were conditionally formatted within each metabolite across diet on a color scale. Blue indicates a relative concentration lower than the other treatments, white indicates an intermediate relative concentration, and red indicates a higher relative concentration than the other treatments. 1, heptanoate (7:0); 2, caprylate (8:0); 3, caprate (10:0); 4, laurate (12:0); 5, 5-dodecenoate (12:1n7); 6, myristate (14:0); 7, pentadecanoate (15:0); 8, palmitate (16:0); 9, margarate (17:0); 10, stearate (18:0); 11, nonadecanoate (19:0); 12, arachidate (20:0); 13, palmitoleate (16:1n7); 14, 10-heptadecenoate (17:1n7); 15, oleate/vaccenate (18:1); 16, 10-nonadecenoate (19:1n9); 17, erucate (22:1n9); 18, hexadecadienoate (16:2n6); 19, hexadecatrienoate (16:3n3); 20, linoleate (18:2n6); 21, stearidonate (18:4n3); 22, arachidonate (20:4n6); 23, eicosapentaenoate (EPA; 20:5n3); 24, heneicosapentaenoate (21:5n3); 25, docosadienoate (22:2n6); 26, docosatrienoate (22:3n3); 27, docosapentaenoate (n6 DPA; 22:5n6); 28, docosahexaenoate (DHA; 22:6n3). Full article ">

11 pages, 3401 KiB

Open AccessArticle

Fe²⁺ Alleviated the Toxicity of ZnO Nanoparticles to Pseudomonas tolaasii Y-11 by Changing Nanoparticles Behavior in Solution

by Yuran Yang, Can Zhang, Kaili Li and Zhenlun Li

Microorganisms 2021, 9(11), 2189; https://doi.org/10.3390/microorganisms9112189 - 20 Oct 2021

Cited by 6 | Viewed by 1499

Abstract

The negative effect of ZnO nanoparticles (ZnO-NPs) on the biological removal of nitrate (NO₃⁻) has received extensive attention, but the underlying mechanism is controversial. Additionally, there is no research on Fe²⁺ used to alleviate the cytotoxicity of NPs. In [...] Read more.

The negative effect of ZnO nanoparticles (ZnO-NPs) on the biological removal of nitrate (NO₃⁻) has received extensive attention, but the underlying mechanism is controversial. Additionally, there is no research on Fe²⁺ used to alleviate the cytotoxicity of NPs. In this paper, the effects of different doses of ZnO-NPs on the growth and NO₃⁻ removal of Pseudomonas tolaasii Y-11 were studied with or without Fe²⁺. The results showed that ZnO-NPs had a dose-dependent inhibition on the growth and NO₃⁻ removal of Pseudomonas tolaasii Y-11 and achieved cytotoxic effects through both the NPs themselves and the released Zn²⁺. The addition of Fe²⁺ changed the behavior of ZnO-NPs in an aqueous solution (inhibiting the release of toxic Zn²⁺ and promoting the aggregation of ZnO-NPs), thereby alleviating the poisonous effect of ZnO-NPs on the growth and nitrogen removal of P. tolaasii Y-11. This study provides a theoretical method for exploring the mitigation of the acute toxicity of ZnO-NPs to denitrifying microorganisms. Full article

(This article belongs to the Topic Anaerobic Digestion Processes)

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16 pages, 4646 KiB

Open AccessArticle

Management of Dark Fermentation Broth via Bio Refining and Photo Fermentation

by Karolina Kucharska, Patrycja Makoś-Chełstowska, Edyta Słupek and Jacek Gębicki

Energies 2021, 14(19), 6268; https://doi.org/10.3390/en14196268 - 1 Oct 2021

Cited by 15 | Viewed by 2704

Abstract

Lignocellulose and starch-based raw materials are often applied in the investigations regarding biohydrogen generation using dark fermentation. Management of the arising post-fermentation broth becomes a problem. The Authors proposed sequential processes, to improve the efficiency of both hydrogen generation and by-products management carried [...] Read more.

Lignocellulose and starch-based raw materials are often applied in the investigations regarding biohydrogen generation using dark fermentation. Management of the arising post-fermentation broth becomes a problem. The Authors proposed sequential processes, to improve the efficiency of both hydrogen generation and by-products management carried under model conditions. During the proposed procedure, the simple sugars remaining in broth are converted into organic acids, and when these products are used as substrates for the photo fermentation process. To enhance the broth management also conditions promoting Deep Eutectic Solvents (DES) precursors synthesis are simultaneously applied. Application of Box-Behnken design allows defining of the optimal conditions for conversion to DESs precursors. During the procedure hydrogen was obtained, the concentration of hydrogen in the photo fermentation reached up to 819 mL _H2/L _medium/7 d, depending on the broth type, i.e., when the broth was optimized for formic acid concentration. The DESs precursors were separated and engaged in DESs synthesis. To confirm the formation of the DESs, FT-IR analyses were performed. The Chemical Oxygen Demand of post-fermentation broths after dark fermentation optimized for formic acid was reduced by ca. 82%. The proposed procedure can be successfully used as a method of post-fermentation broth management. Full article

(This article belongs to the Topic Anaerobic Digestion Processes)

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Design of experiment. Full article ">Figure 2
Response surface plots. (a) Surface plot of FA concentrations in dependence of X1, X2 for hold value of concentration X3 = 35%; (b) Surface plot of LA concentrations in dependence of X1, X2 for hold value of concentration X3 = 60%; (c) Surface plot of FF concentrations in dependence of X1, X3 for hold value of concentration X3 = 60%; (d) Surface plot of HMF concentrations in dependence of X1, X2 for hold value of time X2 = 46 h; (e) Surface plot of glucose and xylose concentrations in dependence of X1, X3 for hold value of time X2 = 24 h. Full article ">Figure 3
(a) Selection of the appropriate HBD for the selective removal of FA, LA, HMF and FF from the model fermentation broth and simultaneous formation of DES (b) Optimization of the amount of HBD used for effective removal of HMF, FF from the model fermentation broth and simultaneous formation of DES. Full article ">Figure 4
FT-IR spectrums from optimization of the kind of HBD used for effective removal of FF (a) and HMF (b) from the model fermentation broth and simultaneous formation of DES. Full article ">Figure 5
FT-IR spectrums from optimization of the amount of thymol (Th) to effective removal of FF from the model fermentation broth and simultaneous formation of DES; (a) all spectrum; (b) zoom spectrum at 4000–3000 cm−1; (c) zoom spectrum at 1650–850 cm−1. Full article ">Figure 6
FT-IR spectrums from optimization of the amount of thymol (Th) to effective removal of HMF from the model fermentation broth and simultaneous formation of DES, (a) all spectrum; (b) zoom spectrum at 4000–3000 cm−1; (c) zoom spectrum at 1650–850 cm−1. Full article ">

13 pages, 2411 KiB

Open AccessArticle

Investigation on the Interactive Effects between Temperature and Chemical Composition of Organic Wastes on Anaerobic Co-Digestion Performance

by Siqi Zhang, Ying Wang, Jinghui Song, Chenjing Sheng, Zezhou Shang, Rui Wang, Xiaojiao Wang, Gaihe Yang, Yongzhong Feng and Guangxin Ren

Processes 2021, 9(9), 1682; https://doi.org/10.3390/pr9091682 - 20 Sep 2021

Cited by 1 | Viewed by 1908

Abstract

Synergistic effects among different chemical components under the anaerobic co-digestion (AcoD) process played an important role in improving its performance, which might be affected by the digesting temperature. The results showed that the actual methane production (AMP) and gasification rate (GR) of 50% [...] Read more.

Synergistic effects among different chemical components under the anaerobic co-digestion (AcoD) process played an important role in improving its performance, which might be affected by the digesting temperature. The results showed that the actual methane production (AMP) and gasification rate (GR) of 50% lipid content were the highest, and the carbohydrate and protein content should be adjusted according to the temperature. Under mesophilic conditions, the M1 reactor with high protein content (carbohydrate–lipid–protein ratio, CLP = 20:50:30) had the highest AMP of 552.02 mL/g VS and GR of 74.72%. However, as the temperature increased, the high protein content produced high levels of ammonia nitrogen (AN) and free ammonia (FA), which formed a certain degree of ammonia inhibition, resulting in lower AMP and GR. Under thermophilic conditions, the low protein T2 reactor (CLP = 40:50:10) had the highest AMP and GR at 485.45 mL/g VS and 67.18%. In addition, the M1 and T2 reactors had the highest microbial diversity, which promoted substrate degradation and methane production. In the M1 reactor, acetoclastic metabolism is the main methanogenic pathway, while in the T2 reactor changes to hydrogenotrophic metabolism. Therefore, understanding the synergistic effect between temperature and chemical compositions was an effective way to improve the AcoD effect. Full article

(This article belongs to the Topic Anaerobic Digestion Processes)

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Daily methane production from different mixtures of substrates under mesophilic conditions (A) and thermophilic conditions (B) (note: the data were the mean of three repetitions). Full article ">Figure 2
Profiles of volatile fatty acid (VFA) concentration and pH value variation of co-digestion under mesophilic conditions (a,A) and thermophilic conditions (b,B) (note: the data were the mean of three repetitions, and error bars indicate standard deviation. a and A represent VFA concentration and pH value at mesophilic conditions, b and B represent VFA concentration and pH value at thermophilic conditions.). Full article ">Figure 3
Concentrations of ammonium nitrogen (AN) and free ammonia (FA) under mesophilic conditions (A,a) and thermophilic conditions (B,b) (note: the data were the mean of three repetitions, and error bars indicated standard deviation. A and a represent concentrations of AN and FA at mesophilic conditions, B and b represent concentrations of AN and FA at thermophilic conditions.). Full article ">Figure 4
Microbial profiles of the bacterial genera (A) and the archaeal genera (B) (only bacterial and archaeal genera with relative abundance of ≥0.5% in at least one digester are presented; the rest were classified as others; all other unidentified were included in unclassified). Full article ">Figure 5
Principal component analysis (PCA) of bacterial (A) and archaeal (B) operational taxonomic unit (OTU) distribution generated by 16S rRNA gene sequencing. Full article ">

9 pages, 953 KiB

Open AccessArticle

Co-Digestion of Kitchen Waste with Grass and Leaves after Hyperthermophilic Pretreatment for Methane and Hydrogen Production

by Przemysław Liczbiński and Sebastian Borowski

Energies 2021, 14(18), 5880; https://doi.org/10.3390/en14185880 - 17 Sep 2021

Cited by 3 | Viewed by 1909

Abstract

The study investigated co-digestion batch experiments using kitchen waste (KW) and garden waste (GW) collected from individual households. Grass and leaves were first subjected to a 3-day hyperthermophilic pretreatment at 70 °C and 80 °C and then co-digested with kitchen waste at 35 [...] Read more.

The study investigated co-digestion batch experiments using kitchen waste (KW) and garden waste (GW) collected from individual households. Grass and leaves were first subjected to a 3-day hyperthermophilic pretreatment at 70 °C and 80 °C and then co-digested with kitchen waste at 35 °C and 55 °C. The hyperthermophilic pretreatment resulted in the solubilization of organic material with the release of fatty acids, whereas the biogas yield was negligible. In the second stage, the greatest methane yield of 387 NmL/gVS was achieved for the mono-digestion of leaves, whereas the co-digestion of grass with 50% KW gave the highest hydrogen production of 88 NmL/gVS. Considering the overall process performance, the best operating conditions were established using a 3-day hyperthermophilic pretreatment at 70 °C, followed by co-digestion at 55 °C in the second stage for the mixture of 25% garden waste with 75% KW. Full article

(This article belongs to the Topic Anaerobic Digestion Processes)

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15 pages, 2675 KiB

Open AccessArticle

The Effect of Detoxification of Lignocellulosic Biomass for Enhanced Methane Production

by Katarzyna Kotarska, Wojciech Dziemianowicz and Anna Świerczyńska

Energies 2021, 14(18), 5650; https://doi.org/10.3390/en14185650 - 8 Sep 2021

Cited by 5 | Viewed by 2146

Abstract

The aim of this research is to examine the effect of lignocellulosic biomass detoxification on the efficiency of the methane fermentation process. Both for corn straw and rye straw, the methane yield was expressed per volume of fermentation medium and per mass of [...] Read more.

The aim of this research is to examine the effect of lignocellulosic biomass detoxification on the efficiency of the methane fermentation process. Both for corn straw and rye straw, the methane yield was expressed per volume of fermentation medium and per mass of volatile solids (VS) added. Lignocellulosic biomass was subjected of thermo-chemical and enzymatic sequential pretreatments. It was found that methane yield was higher by 22% when using the detoxification process. In these variants, CH₄ yield was 18.86 L/L for corn straw and 17.69 L/L for rye straw; while methane yield expressed per mass of VS added was 0.31 m³/kg VS for corn straw and 0.29 m³/kg VS for rye straw. The inclusion of a detoxification step in pretreatments of biomass lignocellulosic increases the degree of organic substance decomposition and enhances methane yield. The results show that a two-step pretreatment, alkaline/enzymatic with a detoxification process, is necessary for the effective generation of high methane concentration biogas. Full article

(This article belongs to the Topic Anaerobic Digestion Processes)

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13 pages, 1231 KiB

Open AccessArticle

The Effect of Ammonia Toxicity on Methane Production of a Full-Scale Biogas Plant—An Estimation Method

by Sotirios D. Kalamaras, Georgios Vitoulis, Maria Lida Christou, Themistoklis Sfetsas, Spiridon Tziakas, Vassilios Fragos, Petros Samaras and Thomas A. Kotsopoulos

Energies 2021, 14(16), 5031; https://doi.org/10.3390/en14165031 - 16 Aug 2021

Cited by 13 | Viewed by 2563

Abstract

Ammonia accumulation in biogas plants reactors is becoming more frequently encountered, resulting in reduced methane (CH₄) production. Ammonia toxicity occurs when N-rich substrates represent a significant part of the biogas plant’s feedstock. The aim of this study was to develop an [...] Read more.

Ammonia accumulation in biogas plants reactors is becoming more frequently encountered, resulting in reduced methane (CH₄) production. Ammonia toxicity occurs when N-rich substrates represent a significant part of the biogas plant’s feedstock. The aim of this study was to develop an estimation method for the effect of ammonia toxicity on the CH₄ production of biogas plants. Two periods where a biogas plant operated at 3200 mg·L⁻¹ (1st period) and 4400 mg·L⁻¹ (2nd period) of ammonium nitrogen (NH₄⁺–N) were examined. Biomethane potentials (BMPs) of the individual substrates collected during these periods and of the mixture of substrates with the weight ratio used by the biogas plant under different ammonia levels (2000–5200 mg·L⁻¹ NH₄⁺–N) were determined. CH₄ production calculated from the substrates’ BMPs and the quantities used of each substrate by the biogas plant was compared with actual CH₄ production on-site. Biogas plant’s CH₄ production was 9.9% lower in the 1st and 20.3% in the 2nd period in comparison with the BMP calculated CH₄ production, of which 3% and 14% was due to ammonia toxicity, respectively. BMPs of the mixtures showed that the actual CH₄ reduction rate of the biogas plant could be approximately estimated by the ammonia concentrations levels. Full article

(This article belongs to the Topic Anaerobic Digestion Processes)

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43 pages, 4597 KiB

Open AccessArticle

A Review of the State of the Art of Biomethane Production: Recent Advancements and Integration of Renewable Energies

by Francesco Calise, Francesco Liberato Cappiello, Luca Cimmino, Massimo Dentice d’Accadia and Maria Vicidomini

Energies 2021, 14(16), 4895; https://doi.org/10.3390/en14164895 - 10 Aug 2021

Cited by 25 | Viewed by 5085

Abstract

Anaerobic Digestion (AD) is a well-established process that is becoming increasingly popular, especially as a technology for organic waste treatment; the process produces biogas, which can be upgraded to biomethane, which can be used in the transport sector or injected into the natural [...] Read more.

Anaerobic Digestion (AD) is a well-established process that is becoming increasingly popular, especially as a technology for organic waste treatment; the process produces biogas, which can be upgraded to biomethane, which can be used in the transport sector or injected into the natural gas grid. Considering the sensitivity of Anaerobic Digestion to several process parameters, mathematical modeling and numerical simulations can be useful to improve both design and control of the process. Therefore, several different modeling approaches were presented in the literature, aiming at providing suitable tools for the design and simulation of these systems. The purpose of this study is to analyze the recent advancements in the biomethane production from different points of view. Special attention is paid to the integration of this technology with additional renewable energy sources, such as solar, geothermal and wind, aimed at achieving a fully renewable biomethane production. In this case, auxiliary heat may be provided by solar thermal or geothermal energy, while wind or photovoltaic plants can provide auxiliary electricity. Recent advancements in plants design, biomethane production and mathematical modeling are shown in the paper, and the main challenges that these fields must face with are discussed. Considering the increasing interest of industries, public policy makers and researchers in this field, the efficiency and profitability such hybrid renewable solutions for biomethane production are expected to significantly improve in the next future, provided that suitable subsidies and funding policies are implemented to support their development. Full article

(This article belongs to the Topic Anaerobic Digestion Processes)

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Anaerobic Digestion Processes

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