Performance Of Anaerobic Co-digestion Research Articles

Effect of plastic additives on anaerobic biological reutilization of biodegradable plastics and sludge: Focusing on the digestion process, microbial composition and metabolic traits

The inevitable release of plastic additives (PAs) from biodegradable plastics (BPs) might affect the ensuing biological reutilization, and the impact of PAs on anaerobic co-digestion performance is still controversial. This study evaluated the impacts of three typical PAs (bis(2-ethylhexyl) phthalate (DEHP), acetyl tributylcitrate (ATBC), tributyl citrate (TBC)) on the BPs anaerobic co-digestion with waste-activated sludge (WAS). Results indicated that the BPs type had a significant effect on methane production, but the effect of PAs was negligible within a concentration range (0.5–50 mg/g TSS). Mechanistic exploration revealed that PAs addition exhibited insignificant effects on solubilization, hydrolysis, and acidification stage. Microbial communities' analyses suggested that PAs did not change the diversity and composition of microbial communities. Furthermore, the addition of PAs has no direct effect on the metabolic function of microorganisms. This study shed light on the effects of PAs on BPs biological reutilization and help to gain a better understanding of the potential environmental hazards of plastics.

Colimoxin influences on the anaerobic co-digestion performance of chicken manure and wheat straw: volatile fatty acids generation and utilization trends and regression modelling

Colimoxin influences on the anaerobic co-digestion performance of chicken manure and wheat straw: volatile fatty acids generation and utilization trends and regression modelling

Effect of biochar on anaerobic co-digestion performance and microbial communities of hulless barley straw and pig manure

Effect of biochar on anaerobic co-digestion performance and microbial communities of hulless barley straw and pig manure

Enhancement effects and mechanisms of iron filings on the performance of anaerobic co-digestion of hulless barley straw and pig manure

In order to study the enhancing effects and mechanisms of iron filings in anaerobic co-digestion (co-AD), we investigated the effects of different concentrations of iron filings (0 g L−1, 6 g L −1, 10 g L −1, 14 g L −1, 18 g L −1) on the co-AD of hulless barley straw and pig manure, based on medium-temperature batch anaerobic digestion. The results revealed that the addition of iron filings improved the methane production performance of co-AD, and that cumulative methane production was the highest (375.26 mL g−1 VS) when the addition concentration was 14 g L −1, which was 21.33 % higher than that of the treatment group without added iron filings. The addition of an appropriate amount iron filings can also provide certain economic benefits. The addition of iron filings increased the relative abundances of bacterial groups such as Fermentimonas, Proteiniphilum, Syner-01, Ercella, Thermovirga, unclassified Synergistaceae and unclassified Anaerolineaceae as well as acetate trophic methanogens such as Methanothrix and Methanosarcina, but it did not promote the growth of hydrogenotrophic methanogens. The addition of iron filings increased the electron transport system (ETS) activity of the co-AD and enhanced the enrichment of microorganisms involved in direct interspecies electron transfer (DIET), such as Methanothrix, Methanosarcina and unclassified Anaerolineaceae. This may represent one of the key reasons behind the observed increase in methane production. A metabolomic analysis found that the presence of 47 metabolites may have been related to the addition of iron filings, suggesting that their addition significantly affected the related metabolic pathways of the co-AD. The differential metabolites were mainly enriched in metabolic pathways such as ATP-binding cassette (ABC) transport, purine metabolism, linoleic acid metabolism, and alpha-linolenic acid metabolism.

Association of magnetic-flyash in anaerobic co-digestion for biomethane optimization: Promoting biofilm formation

The application of low-cost magnetic industrial wastes as accelerants can significantly improve the performance of anaerobic co-digestion (AcoD), thereby enhancing the biogas yield. In this work, varying concentrations (1.0–4.0 wt.%) of magnetic flyash (MFA) were applied to the AcoD of cow manure (CM) and aloe peel waste (APW). All AcoD systems were operated under mesophilic condition (37 ᴼC) with a 5 mT magnetic field. The AcoD system with 2.0 wt.% of MFA showed the highest cumulative biogas yield (487 mL/g VS), methane content (65.17%), COD, TS and VS removal rates (36.45, 45.49 and 52.10%, respectively), and fertility (3.4%). However, the 1.0 wt.% of NMFA also showed higher cumulative biogas yield (432 mL/g VS), methane content (60.23%), COD, TS and VS (27.69, 18.24 and 43.64%, respectively), and fertility (3.31%) than other NMFA concentrations (1.5 & 2.0 wt.%). Kinetic models verified that MFA coupled with a magnetic field could increase biogas potential and production rate. A strategy for determining the role of MFA in microbial biofilm formation and improving biodegradation, which increases the biogas yield, is also suggested. This work demonstrates a cost-effective application of MFA in bioenergy production systems by improving the AD process.

Investigates of substrate mingling ratio and organic loading rate of KOH pretreated corn stover and pig manure in batch and semi-continuous system: Anaerobic digestion performance and microbial characteristics

The effects of substrate mingling ratio (SMR) (1:1, 1:2, 1:3, 3:1, and 2:1) and organic loading rate (OLR) (50–90 g total solids per liter per day) on anaerobic co-digestion performance and microbial characteristics were investigated for pig manure (PM) and pretreated/untreated corn stover in batch and semi-continuous anaerobic digestion (AD) system. The results showed that SMR and pretreatment affected co-digestion performance. The maximum cumulative methane yield of 428.5 ml⋅g−1 (based on volatile solids (VS)) was obtained for PCP13, which was 35.7% and 40.0% higher than that of CSU and PM. In the first 5 days, the maximum methane yield improvement rate was 378.1% for PCP13. The daily methane yield per gram VS of PCP13 was 11.4%–18.5% higher than that of PCU13. Clostridium_sensu_stricto_1, DMER64, and Bacteroides and Methanosaeta, Methanobacterium, and Methanospirillum had higher relative abundance at the genus level. Therefore, SMR and OLR are important factor affecting the AD process, and OLR can affect methane production through volatile fatty acids.

Development of a Statistical Model to Predict Methane Production from Waste Activated Sludge Co-Digested with Olive Mill Wastewater and Cattle Dung by Response Surface Methodology

Nowadays, population growth is likely to lead to a wide variety of biomass wastes generation from the diversified human, industrial, and agricultural activities. Anaerobic digestion is mostly applied to manage biomass wastes and mitigate a huge spectrum of environmental damages. This paper aims to enhance the anaerobic digestion efficiency of multicomponent substrates, using a mixture of waste activated sludge (WAS), olive mill wastewater (OMW), and cattle manure (CM). A Response Surface Methodology is employed in experimental design to determine individual and interactive effects on methane yield and chemical oxygen demand reduction. After numerical optimization using Design Expert®, the optimum values of the test factors in actual were as follows: initial pH = 8, COD/N ratio = 47, 42, CM/WAS-OMW ratio = 0.352, TS = 42.94 g/L. The obtained results indicate that anaerobic co-digestion performance could be achieved by optimising substrate composition to assure a larger microbial synergistic effect.

Co-digestion of food waste and hydrothermal liquid digestate: Promotion effect of self-generated hydrochars

Hydrothermal treatment (HTT) can efficiently valorize the digestate after anaerobic digestion. However, the disposal of the HTT liquid is challenging. This paper proposes a method to recover energy through the anaerobic co-digestion of food waste and HTT liquid fraction. The effect of HTT liquid recirculation on anaerobic co-digestion performance was investigated. This study focused on the self-generated hydrochars that remained in the HTT supernatant after centrifugation. The effect of the self-generated hydrochars on the methane (CH4) yield and microbial communities were discussed. After adding HTT liquids treated at 140 and 180 °C, the maximum CH4 production increased to 309.36 and 331.61 mL per g COD, respectively. The HTT liquid exhibited a pH buffering effect and kept a favorable pH for the anaerobic co-digestion. In addition, the self-generated hydrochars with higher carbon content and large oxygen-containing functional groups remained in HTT liquid. They increased the electron transferring rate of the anaerobic co-digestion. The increased relative abundance of Methanosarcina, Syntrophomonadaceae, and Synergistota was observed with adding HTT liquid. The results of the principal component analysis indicate that the electron transferring rate constant had positive correlationships with the relative abundance of Methanosarcina, Syntrophomonadaceae, and Synergistota. This study can provide a good reference for the disposal of the HTT liquid and a novel insight regarding the mechanism for the anaerobic co-digestion.

Enhancing methane yield from duck waste by co-digestion with Xyris capensis

This study examined the possibilities of enhancing methane yield from anaerobic digestion of Xyris capensis and duck wastes based on improved feeding composition and the C/N ratio. Batch anaerobic digestion of Xyris capensis and duck wastes was conducted at mesophilic temperature (37 ± 2 °C) with the mixing ratios of 100:0, 75:25, 50:50, 25:75, and 0:100% of duck wastes: Xyris capensis. The highest methane yield of 301.17 mL CH4/ gVSadded was recorded when the mixing ratio of 50:50% (duck wastes: Xyris capensis) and C/N ratio of 19.26 was digested. The biodegradability (BD) of duck wastes and Xyris capensis were 86.60 and 58.57%, respectively. The BD of duck wastes increases with the addition of Xyris capensis, and it started to decline after a 50:50% mixing ratio. A stronger synergistic influence of co-digestion was noticed compared to monodigestion of the individual of each feedstock. This study showed a better performance of anaerobic co-digestion and can be used to enhance feeding composition and the C/N ratio. In general, methane production from duck wastes co-digested with Xyris capensis is a good strategy to generate renewable energy and minimize waste management challenges.

Enhanced methane production in anaerobic co-digestion systems with modified black phosphorus

Black phosphorus (BP) and BP modified by hydrogen peroxide (MBP) were used as accelerants to enhance CH4 production and CO2 reduction in microbial electrolysis cells (MECs) coupled with anaerobic co-digestion systems (MEC-AcoD). The MEC-AcoD group with a voltage of 0.6 V and 0.03 wt.% of MBP accelerant (MEC0.6MBP0.03) had the largest CH4 yield (242.1 mL/g VS) and the smallest carbon dioxide yield (97.6 mL/g VS) compared with the control group (141.2 mL/g VS, 146.9 mL/g VS). The digestates that used MEC0.6MBP0.03 exhibited superior thermal stability (46.2 %) and total nutrient contents (44.5 g/kg). These improvements may be attributed to the superior electron exchange capacity and physicochemical properties of MBP. Herein, we propose a strategy to understand enhanced CH4 production and CO2 reduction in anaerobic co-digestion and MEC-AcoD systems using MBP accelerants. Notably, combining MBP and MEC could effectively promote anaerobic co-digestion performance.

Impact of total solids content on biochar amended co-digestion of food waste and sludge: Microbial community dynamics, methane production and digestate quality assessment

This study evaluates the impact of biochar addition on the performance of anaerobic co-digestion of food waste (FW) and sewage sludge at different total solids (TS) contents (2.5 %, 5.0 %, and 7.5 %). Biochar co-digestion improved hydrolysis and acidogenesis by neutralizing volatile fatty acids (VFAs) reducing its inhibitions (2.6-fold removal), which elevated the soluble chemical oxygen demand (sCOD) degradation by 2.5 folds leading to a higher cumulative methane production compared to the control. This increase corresponded to an improvement of methane yields by ∼21 %−33 % (242–340 mL/gVSadd) at different TS contents. The biochar surface area offered substantial support for direct interspecies electron transfer (DIET) activity, and biofilm-mediated growth of methanogens i.e., Methanosarcina, Methanosata, and Methanobrevibacter. The biochar-enriched digestate improved the seed germination index, and bioavailability of plant nutrients such as N, P, K, and NH4+-N. This study reports an improved biochar-mediated anaerobic co-digestion for efficient and sustainable FW valorization.

Performance of anaerobic co-digestion with honey processing wastewater as co-substrate for treating synthetic wastewater containing commercial anthraquinone dye Remazol blue RSP: Effect of C:N ratio and HRT

Anaerobic co-digestion (ACoD) using solid waste as co-substrate is inefficient for industrial wastewater treatment. This study investigated the effect of honey processing wastewater as a co-substrate on the performance of ACoD in treating synthetic wastewater containing commercial anthraquinone dye. The objective of this study was to determine the optimum C:N ratio and HRT in ACoD to obtain COD removal and decolorization efficiently. The experiment was conducted using laboratory UASB reactors with a total volume of 4.8 L inoculated with anaerobic granule and the variations of C:N and HRT were used. The result showed optimal configuration was obtained in 5:1 C:N ratio at 24 h HRT resulted in 76.69 ± 2.83 % COD removal and 97.37 ± 3.62 % decolorization. Metagenomic analysis showed that the optimal ACoD configuration was suitable for both COD removal and reductive decolorization, by the presence of phylum Halobacteriota (38.2 %), Euryacrhaeota (4 %), Desulfobacteriota (16 %), Actinobacteriota (10 %) and, other Bacterial phylum.

Anaerobic co-digestion of dissolved air floatation slurry and selenium rich wastewater for simultaneous methane production and selenium bioremediation

The energy potential of dissolved air floatation (DAF) slurry, a lipid-rich waste, is largely disregarded with the common practice of land spreading or landfilling. On the other hand, selenium (Se) contaminated wastewaters are perceived as unsuitable feedstocks because of their toxicity. This study aimed to evaluate the anaerobic co-digestion performance of a DAF slurry with Se rich wastewater using anaerobic granular sludge and waste activated sludge as the inocula. Anaerobic batch assays of DAF slurry supplemented with 0.05, 0.10, 0.25 and 0.50 mM selenate (SeO42−) and selenite (SeO32−), along with a control (without Se) were performed at 30 °C. Methanogenesis of the DAF slurry using anaerobic granular sludge was realised during co-digestion up to 0.50 mM SeO42−, whereas SeO32− was already toxic from 0.05 mM onwards. Co-digestion of the DAF slurry with 0.05 and 0.10 mM Se oxyanions (both selenate and selenite) containing wastewater using waste activated sludge achieved a similar cumulative methane yield of about 180 mL/g COD as that of mono-digestion (Se free DAF slurry) after 65 days of incubation. Simultaneously, more than 90% removal of Se was accomplished. The lag phase duration was, however, extended by 50 and 90% in the presence of 0.05 and 0.10 mM Se, respectively. The half maximal inhibitory concentration (IC50) for methane production using waste activated sludge was 0.08 mM for SeO42− and 0.07 mM for SeO32−. The IC50 amounted to 2.10 mM for SeO42− and 0.08 mM for SeO32− with anaerobic granular sludge. SeO42− and SeO32− were reduced to elemental Se nanoparticles, as shown by transmission electron microscopy. This study indicates the feasibility of methane production from a DAF slurry, codigested with wastewaters containing up to 0.10 mM SeO42− or SeO32−.

Iron-fortified Anaerobic Co-digestion Performance of Kitchen Waste and Pennisetum Hybrid

Iron-fortified Anaerobic Co-digestion Performance of Kitchen Waste and Pennisetum Hybrid

Performance of Anaerobic Co-Digestion with Honey Processing Wastewater as Co-Substrate for Treating Synthetic Wastewater Containing Commercial Anthraquinone Dye Remazol Blue Rsp: Effect of C:N Ratio and Hrt

Performance of Anaerobic Co-Digestion with Honey Processing Wastewater as Co-Substrate for Treating Synthetic Wastewater Containing Commercial Anthraquinone Dye Remazol Blue Rsp: Effect of C:N Ratio and Hrt

Anaerobic Co-Digestion of Cow Manure and Palm Oil Mill Effluent (POME): Assessment of Methane Production and Biodegradation Efficiency

The performance of anaerobic co-digestion of cow manure and POME was evaluated. The anaerobic composting process was carried out by using semi-continuous reactors under the mesophilic condition (35 ± 1℃). The addition of POME to the on-going anaerobic composting of cow manure was applied stepwise within a cycle of HRT (20 days). Results showed that the anaerobic co-digestion reactor could produce methane at about six times higher (7.2 L CH4) than the control reactor (1.3 L CH4). An increasing of POME loaded to the on-going anaerobic composting cow manure culture (4% to 64%) did not affect pH of the culture in which pH was still stable between 7.11 and 7.5. Assessment of biodegradation efficiency revealed that nitrogen removal of the anaerobic co-digestion reactor was six times higher (21%) than the nitrogen removal of the control reactor (3.4%). This suggested that the anaerobic co-digestion reactor performed sufficiently well in which no organic acid as well as ammonia accumulated in the reactor that could be effective to decompose the organic matters.

Enhanced anaerobic co-digestion performance by using surface-annealed titanium spheres at different atmospheres

A series of surface-annealed titanium spheres (Ti-A, Ti-B, and Ti-C) in different atmospheres were used as accelerants in anaerobic co-digestion (AcoD) systems under magnetic field (MF). Surface-annealed titanium spheres and MF exhibit remarkable coupling and promoting effects on the AcoD performance. The cumulative biogas yield (435.84–552.60 mL/g VS) and total chemical oxygen demand (COD) degradation efficiency (59.76%–71.28%) of the AcoD systems with TiMF, Ti-AMF, Ti-BMF, and Ti-CMF were significantly higher than control (357.66 mL/g VS and 51.5%). The digestates of the AcoD system with surface-annealed Ti spheres delivered excellent stability (49.83%–59.90%) and fertilizer (4.21%–4.56%). This work clarifies the possible role of surface-annealed Ti spheres in enhancing methanogenesis.

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

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.

Mechanism study of improving anaerobic co-digestion performance of waste activated sludge and food waste by Fe3O4

A large amount of waste activated sludge (WAS) and food waste (FW) are produced every year in China. Anaerobic co-digestion is considered to be an effective way to solve this problem. This study applied FW/WAS mixture as co-substrate to create different digestive environment, aiming to understand the mechanism of Fe3O4 particles in promoting AD performance. The results showed that the addition of Fe3O4 presented various performances when facing different digestive acidification stress brought by different mixing ratios of WAS and FW. Methanogenic pathways and microbial communities varied with substrates’ properties. For group A (WAS mono-digestion), the acetoclastic methanogens dominated, 20 mg/g VS (according to the iron element) Fe3O4 could promote methane production, while 200 mg/g VS Fe3O4 would inhibit microbial activity. The promoted methane production by Fe3O4 was attributable to the promotion of sludge hydrolysis. For group B (WAS: FW = 1:0.5, based on VS addition, similarly hereinafter), Fe3O4 triggered direct interspecific electron transfer (DIET) between bacteria and methanogens. For group C (WAS: FW = 1:1), the hydrogenotrophic methanogens dominated, bacteria excreted more non-conductive polysaccharides in EPS to resist unfavorable environment, thereby it prevented their contact with Fe3O4 particles. So, it was difficult for Fe3O4 to trigger DIET and promote the digestive performance of batch experiments in such condition.

Enhancement of anaerobic co-digestion performance at the high organic load by application of waste seashell: the synergistic impacts of alkaline additive

Enhancement of anaerobic co-digestion performance at the high organic load by application of waste seashell: the synergistic impacts of alkaline additive