Performance Of Co-digestion Research Articles

Effect of biochar on anaerobic co-digestion performance of cellulosic ethanol refinery waste liquor with swine manure

Recently, the high investment in the treatment of waste liquor and residue has become an important issue in the cellulosic ethanol refining industry. This study investigated the biogas production performance of anaerobic digestion (AD) by mixing different proportions of waste liquor (WL) with swine manure (SM). Additionally, the effect of biochar derived from waste residue (WR) pyrolyzed at different temperatures in the AD system was examined. The results indicated that: (1) when refinery WL and SM were mixed at 75:25 (on a basis of g sCOD: g VS), the cumulative methane yield (CMY) reached 225.48 ± 20.63 mL/g VS, demonstrating a synergistic effect of 1.14; (2) biochar prepared at lower pyrolysis temperature was more effective than that prepared at higher temperatures, with BC400 exhibiting remarkable promoting effects. The CMY with BC400 was 255.67 mL/g VS, 15.25 % higher than the control group; (3) the promoting effect of BC400 in the AD system was attributed to the biochar's porous structure and oxygen-containing functional groups, which enriched the hydrolytic, acid-producing, and methanogenic bacterial communities, enhancing direct interspecies electron transfer (DIET) efficiency. The addition of biochar accelerated the AD process and improved methane production efficiency. This research offered reference for the recycling and treatment of cellulosic ethanol refinery waste.

An Examination of Calculations: From Anaerobic Mono-digestion to Co-digestion

Anaerobic digestion is a biochemical process and form of sustainable technology. In comparison to mono-digestion, co-digestion is more effective in the utilization of diverse resources, supply of nutrient balance, and overall digestibility and stability. The co-digestion biodegradability index, co-digestion performance index, and synergistic effect index are generally used as anaerobic metrics to evaluate the co-digestion performance. Although they are numerical parameters, little information on their working procedures has been revealed. There is also a lack of supporting calculations for some published data hence their values cannot be verified. The aim of this article is to reconsider and examine the mathematical calculations from anaerobic mono-digestion to co-digestion. The method of study is a pen-and-paper analysis that processes both experimental and theoretical data from past studies. The article serves four purposes. First, it identifies processing parameters. Second, it shows step-by-step procedures of a series of calculations. Third, it identifies the core parameter in the calculation of anaerobic co-digestion. Fourth, it establishes the relationships between co-digestion biodegradability index, co-digestion performance index, and synergistic effect index. Critically, the mass fraction of volatile solid is identified as the core parameter that determines the valid calculations of co-digestion.

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

Utilization strategy for algal bloom waste through co-digestion with kitchen waste: Comprehensive kinetic and metagenomic analysis

Anaerobic co-digestion (AcoD) with kitchen waste (KW) is an alternative utilization strategy for algal bloom waste (AW). However, the kinetic characteristic and metabolic pathway during this process need to be explored further. This study conducted a comprehensive kinetic and metagenomic analysis for AcoD of AW and KW. A maximum co-digestion performance index (CPI) of 1.13 was achieved under the 12% AW addition. Co-digestion improved the total volatile fatty acids generation and the organic matter transformation efficiency. Kinetic analysis showed that the Superimposed model fit optimally (R2Adj = 0.9988–0.9995). The improvement of the kinetic process by co-digestion was mainly reflected in the increase of the methane production from slowly biodegradable components. Co-digestion enriched the cellulolytic bacterium Clostridium and the hydrogenotrophic methanogenic archaea Methanobacterium. Furthermore, for metagenome analysis, the abundance of key genes concerned in cellulose and lipid hydrolysis, pyruvate and methane metabolism were both increased in co-digestion process. This study provided a feasible process for the utilization of AW produced seasonally and a deeper understanding of the AcoD synergistic mechanism from kinetic and metagenomic perspectives.

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.

Correlation between kinetic parameters, reactor performance, and biogas and methane potential of co-digestion and mono-digestion of active sludge and olive mill wastewater

Abstract Anaerobic co-digestion(AcoD) of active sludge (AS) and olive mill wastewater (OMW) is becoming an increasingly recognized alternative to manage waste and generate renewable energy. A kinetic study of the performance of biochemical methane potential (BMP) and continuous stirred tank reactors (CSTR) bioreactors was conducted to identify critical parameters influencing. Substrates of 100%OMW, 100%AS, 25:75%, 75:25%, and 50:50 were utilized in the BMP and CSTR digesters. To identify the optimum mixing, BMP tests were conducted under three different operating conditions: no mixing (NM), low-continuous mixing intensity (LM) of 25 rpm, and high continuous mixing intensity (HM) of 60 rpm. CSTR with an optimum mixing regime is utilized to identify the optimum substrate. In particular, the removal efficiency of volatile solids (VSs), total chemical oxygen demand (TCOD), and the production of biogas and methane (CH4) were investigated to specify the performance of the anaerobic digestion (AD) process. The results revealed that the optimum mixing regime is LM with BMP tests. Also, the maximum performance in CSTR-ML was achieved by 75:25 AS:OMW, 0.339 Nm3/kg VS of biogas, 69.89% of CH4, and a removal efficiency of 87.12% of VS and 79.23% of TCOD. For BMP tests, the biogas and CH4 yield production kinetics were best fitted by the modified Gompertz models: mono-digestion and co-digestion 75:25 and 50:50 of AS:OMW, while the best-fit model for co-digestion 25:75 was achieved by the transfer model. The production kinetics were well described by modified Gompertz models in CSTR tests. These results point to the possibility of optimizing digester systems on a wide scale using the outputs that have been observed. Novelty statement. This research work provides novel insights into the performance of the digester under diverse mixing conditions and varying co-substrate concentrations of AS:OMW and presents the best model to predicate the biogas and CH4 at various operation conditions.

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.

Metagenomic characterization of the enhanced performance of multicomponent synergistic thermophilic anaerobic co-digestion of food waste utilizing kitchen waste or garden waste as co-substrate

Food waste (FW) single-substrate anaerobic digestion usually suffers from rapid acidification and inhibition of oil and salt. To overcome these problems and improve the process efficiency, supplementing other substrates has been used in FW anaerobic digestion. This study investigated the biogas production potential through co-digestion of FW with kitchen waste (KW) or garden waste (GW) in different ratios under thermophilic conditions. The results showed that the optimal ratios were FW:KW=60:40 and FW:GW=80:20 which biogas production improved 73.33% and 68.45% compared with single FW digestion, respectively. The organic matter removal rate of co-digestion was 84.46% for FW+KW group (RFK) and 65.64% for FW+GW group (RFG). Co-digestion increased the abundance of the dominant hydrolytic bacteria Defluviitoga and Hydrogenispora and hydrogenotrophic methanogen Methanoculleus. Furthermore, glycoside hydrolases (GHs), vital carbohydrate-active enzymes (CAZymes), were improved by co-digestion. Co-digestion could also effectively promote the function of cellulase and hemicellulose. This strategy for utilizing different organic wastes together as co-substrate provides a new avenue for bioenergy production.

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.

Enhanced methane production from the anaerobic co-digestion of food waste plus fruit and vegetable waste.

Food waste (FW) and fruit, vegetable waste (FVW) are important components of municipal solid waste, yet the performance and related mechanisms of anaerobic co-digestion of FW and FVW for methane production have been rarely investigated. In order to get a deeper understanding of the mechanisms involved, the mesophilic FW and FVW anaerobic co-digestion in different proportions was investigated. The experimental results showed that when the ratio of FW and FVW was 1/1 (in terms of volatile suspended solid), the maximum biomethane yield of 269.9 mL/g TCOD from the codigested substrate is significantly higher than that in FW or FVW anaerobic digestion alone. FW and FVW co-digestion promoted the dissolution and biotransformation of organic matter. When the recommended mixing ratio was applied, the maximum concentration of dissolved chemical oxygen demand (COD) was high as 11971 mg/L. FW and FVW co-digestion reduced the accumulation of volatile fatty acids (VFA) in the digestive system, thus reducing its negative impact on the methanogenesis process. FW and FVW co-digestion process synergistically enhanced microbial activity. The analysis of microbial population structure showed that when FW and FVW were co-digested at the recommended ratio, the relative abundance of Proteiniphilum increased to 26.5%, and the relative abundances of Methanosaeta and Candidatus Methanofastidiosum were also significantly increased. The results of this work provide a certain amount of theoretical basis and technical support for the co-digestion of FW and FVW.

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.

High-solid co-digestion performance of lipids and food waste by mesophilic hollow fiber anaerobic membrane bioreactor

The co-digestion performance of mesophilic (37℃) hollow fiber anaerobic membrane bioreactor (HF-AnMBR) in treating high-solid lipids and food waste (FW) for 180 days was investigated. The organic loading rate (OLR) was increased from 2.33 to 14.64 g-chemical oxygen demand (COD) /L/d by increasing the lipids/FW from 10%, 30%, and 50% on dry based. The COD conversion efficiency for methane was 83.13%, 84.85%, 82.63%, and 84.30%, and the sludge growth rate was 0.001, 0.097, 0.065, 0.016 g TS/g COD at OLR of 2.33, 9.36, 12.76 and 14.64 g-COD/L/d, respectively. The COD, proteins, and carbohydrates concentrations in permeate were stable, with an average of 2.25, 0.50, and 0.18 g/L, respectively. The long-term stable performance of the HF-AnMBR indicated that this study will help guide application of the co-digestion of lipids and food waste.

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.

Intermittent energization improves microbial electrolysis cell-assisted thermophilic anaerobic co-digestion of food waste and spent mushroom substance

Microbial electrolysis cell-assisted thermophilic anaerobic digestion (MEC-TAD) is a promising method to improve anaerobic co-digestion efficiency; however, its application is restricted by high energy consumption. To improve the energy use efficiency of MEC-TAD, this study investigated the effect of different intermittent energization strategies on thermophilic co-digestion performance. Results revealed that an 18 h-ON/6h-OFF energization schedule resulted in the fastest electron transfer rate and the highest methane yield (364.3 mL/g VS). Mechanistic analysis revealed that 18 h-ON/6h-OFF resulted in the enrichment of electroactive microorganisms and increased abundance of enzyme-coding genes associated with energy metabolism (ntp, nuo, atp), electron transfer (pilA, nfrA2, ssuE), and the hydrogenotrophic methanogenic pathway. Finally, energy balance analysis revealed that 18 h-ON/6h-OFF had the highest net energy benefit (2.52 kJ) and energy conversion efficiency (110.76 %). Therefore, intermittent energization of MEC-TAD using an 18 h-ON/6h-OFF schedule can provide improved performance and more energy savings.

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.

Assessment of sludge reduction and biogas production in two-step anaerobic co-digestion using sesame oil cake and sewage sludge.

The aim of this study was to investigate the sewage sludge reduction and biogas production using two-stage anaerobic co-digestion of sesame oil cake and sewage sludge. In the first stage (acidogenic fermentation), sesame oil cake (SOC) was acidogenic fermented to produce fermented sesame oil cake (FSOC). In the second step (anaerobic co-digestion), sewage sludge and FSOC were mixed in various ratios of (100:0 (R1), 70:30 (R2), 50:50 (R3), and 30:70 (R4)) and observed for 30 days at a mesophilization temperature of 35±2 °C. In the anaerobic co-digestion using FSOC as a co-feedstock, the volatile solids (VS) and total solids (TS) removal were in the range of 53.7-64.9 and 42.6-53.2% for R2 and R3, respectively. The highest cumulative biogas production (389.67 mL/g·VSin) and methane production (0.56 m3·CH4/kg·VS) was achieved with the R3. In addition, R3 had the shortest reaction delay time (λ), and stabilization of the process was the fastest of all samples. The co-digestion performance index (CPI) was determined to be 1.29, 1.39, and 1.10 for R2, R3, and R4, respectively. The highest value for R3 confirmed the highest synergistic effect. This suggests the possibility of biogas production using sesame oil cake.

Comparative study of the effect of loading increments on the mesophilic codigestion of waste activated sludge and food waste: Reactor performance, stability analysis, and microbial community

The performance and stability of mesophilic codigestion of waste activated sludge (WAS) and food waste (FW) were compared in two parallel, continuously stirred tank reactors using high- and low-magnitude loading increments for the loading regimes. The results indicated that a high methane (CH4) production of 6.98 L L−1·d−1 was realized without volatile fatty acid accumulation via low-magnitude loading increments at a high loading of 26.5 g-COD·L−1·d−1, and this system was more stable and achieved a higher efficiency than the codigestion system that used high-magnitude loading increments at similar loading and operating conditions. Furthermore, higher CH4 yields of 258–334 mL-CH4·g-COD−1, TCOD removal efficiencies of 64–79%, conversion ratios of 62–88%, and methanogenic activities of 0.37–0.40 g-CH4-COD·g-VS−1·d−1 were consistently maintained via the low-magnitude loading increments during the high-rate period. High abundances of the phyla Firmicutes (63.3%) and genus Methanosarcina (94.5%) contributed to the high rates and stable operating conditions of the mesophilic system for WAS and FW codigestion using low-magnitude loading increments.