Anaerobic Digestion For Biogas Production Research Articles

Land cover changes with the development of anaerobic digestion for biogas production in France

AbstractAnaerobic digestion is developing in various countries worldwide to produce renewable energy. In addition, the resulting digestates provide readily available nutrients when applied to cropping systems as fertilizers. The introduction of a biogas plant on a farm can induce land cover changes, in relation to the production of feedstock for the biogas plant and/or to the modification of the farming system. The aim of this study was therefore to characterize and quantify the land cover changes in farms associated with biogas plants in France. We combined two national spatialized databases: the Land Parcel Identification System (yearly French land cover at the parcel scale with farm identifier per parcel) and the SINOE database (biogas plant location and year of start‐up). We showed that, on average, the changes were limited, with an increase in maize areas (+3.4% of the total farm areas) compensated by a decrease in wheat and rapeseed areas (−1.8% and −1.9%, respectively), but with a certain variability. The French regulation and market limiting the use of dedicated energy crops seems to have limited land cover changes in France compared to other countries. However, we elaborated a typology of land cover changes and characterized five clusters of farms across the country. The main one (67% of the farms) corresponded to unchanged land cover after the introduction of a biogas plant. The four other clusters showed contrasting changes, for example, an increase or a decrease in grassland areas, a strong increase in maize areas, or a replacement of winter wheat by winter barley. The diversity and the driving factors behind these changes deserve to be better studied and understood through further farmer surveys.

Ultrasonication-enhanced biogas production in anaerobic digestion of waste active sludge: A pilot scale investigation

In this study, long-term pilot experiments were conducted to investigate the effects of ultrasonication (US) pretreatment on anaerobic digestion (AD) performance. Life cycling assessment (LCA) was used to assess energy efficiency and environmental impacts. With the response to 90-s US at 0.8 W/mL, the soluble COD concentrations increased by 359.0%, whereas the sludge particle size decreased by 56.7%. The positive effects of US increased biogas production by 15.0% and 25.6% at raw sludge VS/TS averages of 0.60 and 0.43, respectively. LCA results indicated that energy neutralization for US-AD was feasible, with a total energy balance of 461.3 kW·h/t DS because of increased energy recovery. The use of US pretreatment allowed for a more diverse microbial community in AD, thereby improving resilience to environmental fluctuations. Unfortunately, US-AD exhibited weak efficiency in inactivating pathogens and antibiotic resistance genes (ARGs), and US could hardly improve the AD control of pathogens carrying ARGs.

A comparative study on polyaluminum chloride (PACl) and Moringa oleifera (MO) chemically enhanced primary treatment (CEPT) in enhanced biogas production: anaerobic digestion performance and the Gompertz model.

A comparative study was performed to estimate biogas production from sludge produced by organic and inorganic chemically enhanced primary treatments (CEPTs). To this end, the effects of two coagulants, polyaluminum chloride (PACl) and Moringa oleifera (MO), on CEPT and biogas production in anaerobic digestion were surveyed within an incubation period of 24 days. The optimal dosage and pH of PACl and MO were optimized in terms of sCOD, TSS and VS parameters in the CEPT process. Next, the digestion performance of anaerobic digestion reactors fed with sludge obtained from PACl and MO coagulants at a batch mesophilic reactor (37 ± 1 °C) was surveyed from the biogas production, volatile solid reduction (VSR) and Gompertz model. At the optimal conditions (pH = 7 and dosage = 5 mg L-1), the removal efficiency of COD, TSS and VS in CEPT assisted with PACL was 63, 81 and 56%, respectively. Moreover, CEPT assisted with MO led to the removal efficiency of COD, TSS and VS until 55, 68 and 25%, respectively. The highest methane yield (0.598 L gVS removed-1) was obtained in an anaerobic digestion reactor with sludge from the MO coagulant. The anaerobic digestion of CEPT sludge instead of primary sludge resulted in higher sCOD removal efficiency, and 43-50% of sCOD was observed compared with the removal of 32% for the primary sludge. Furthermore, the high coefficient of determination (R2) demonstrated the trustworthy predictive precision of the modified Gompertz model with actual data. The combination of CEPT and anaerobic digestion, especially using natural coagulants, provides a cost-effective and practical way to increase BMP from primary sludge.

Co-digestion of food waste with cow dung by anaerobic digestion for biogas production.

Food waste is categorized under household waste which were produce in large amount every day and it can be a good potential to generate biogas production via anaerobic digestion. In this research, the characteristics of co-digestion process are measured to determine the biogas production between food waste and cow dung. The food waste is co-digest with two different type of cow dung are collected depends on their food consuming (grass:bran); 100% grass and 95% grass : 5% bran. The digester is maintained at 35°C of temperature for mesophilic condition. pH values and C/N ratio are noted until 35 days. The biogas production is analysed by using biogas analyzer. The highest biogas production in this study is 67.2% which are co-digest between food waste and cow dung (100%) compared cow dung (95%) is 53.9% on day 26. This shows that the cow dung (100%) produces more biogas than cow dung (95%). Anaerobic digestion process will best suits for biogas production and for the best utilization of food waste.

Thermal modelling and experimental validation for biogas production in anaerobic digestion

The thermal model was developed to calculate the anaerobic digester's heat loss or gain. In addition, a daily comparison of the predicted and actual biogas production from the 2m3 KVIC anaerobic digester has also been completed. When compared to the slurry inside the digester (5000 kg slurry with an average of 60 J/kg per day), the heat gain/loss from the biogas inside the gas holder was found to be very low (1.5 kg biogas with an average of 400 J/kg per day). On the other hand, the average heat energy retained in biogas was 154.69 and 465.49 J/kg, while the minimum and maximum average solar radiations were 37.23 and 216.36 W/m2, respectively. The developed model's validation was assessed using RMSE and RRMSE. The RMSE and RRMSE values were found to be 0.105 m3/day and 7.96 %, respectively, confirming a good correlation between the predicted and measured values.

Synergistic effect of hydrogen and nanoscale zero-valent iron on ex-situ biogas upgrading and acetate recovery

Hydrogen (H2) assisted ex-situ biogas upgrading and liquid chemicals production can augment the fossil fuel-dominated energy market, and alleviate CO2-induced global warming. Recent investigations confirmed that nanoscale zero-valent iron (nZVI) enabled the enhancement of anaerobic digestion for biogas production. However, little is known about the effect of nZVI on the downstream ex-situ biogas upgrading. Herein, different levels (0 mg L−1, 100 mg L−1, 200 mg L−1, 500 mg L−1, 1000 mg L−1, 2000 mg L−1) of nZVI were added for H2-assisted ex-situ biogas upgrading, to study whether nZVI could impact the biomethane purity and acetate yield for the first time. Results showed that all tested nZVI levels were favorable for biogas upgrading in the presence of H2, the highest biomethane content (94.1 %, v/v), the CO2 utilization ratio (95.9 %), and acetate yield (19.4 mmol L−1) were achieved at 500 mg L−1 nZVI, respectively. Further analysis indicated that increased biogas upgrading efficiency was related to an increase in extracellular polymeric substances, which ensures the microbial activity and stability of the ex-situ biogas upgrading. Microbial community characterization showed that the Petrimonas, Romboutsia, Acidaminococcus, and Clostridium predominated the microbiome during biogas upgrading at 500 mg L−1 nZVI with H2 supply. These results suggested that nZVI and H2 contributed jointly to promoting the bioconversion of CO2 in biogas to acetate. The findings could be helpful for paving a new way for efficient simultaneous ex-situ biogas upgrading and liquid chemicals recovery.

Anaerobic digestion of sewage sludge for biogas & biohydrogen production: State-of-the-art trends and prospects

Advancement in the anaerobic digestion of sewage sludge for biogas production is constantly required for effective commercialization. There is great interest in exploring the scientometric and technical assessment in biogas production using sewage sludge from various sources in the anaerobic digestion process. Therefore, this work provides a bibliometric and technical study of anaerobic digestion for biogas production from sewage sludge in the last ten years, based on Web of Science data. The vital parameters of the bibliometric study are authors, countries, and institutional collaboration along with the authors' keywords. In terms of technical assessment, challenges are highlighted with critical analysis of previous work performed both on a laboratory scale and on a pilot scale. The study recommends key considerations and new combination techniques to enhance biohydrogen production with optimized process conditions which will provide vital economic impact for technological adaptation and commercialization.

Insight into enhanced acetic acid production from food waste in anaerobic hydrolysis/acidification with Fe3O4 supplementation

Fe3O4 supplementation has been reported as a high-efficient approach to enhance biogas production in anaerobic digestion (AD). Volatile fatty acids (VFAs), especially acetic acid (HAc), are considered as important products in acidification process of AD. However, the possible mechanisms involved in promotion effect of Fe3O4 on HAc production in hydrolysis and acidification processes of AD have not been comprehensively studied. This study first investigated the promotion effect of Fe3O4 on hydrolysis, acidogenesis and acetogenesis stages of AD and proposed the underlying mechanisms, using food waste (FW) as the feedstock, which is considered as the most suitable substrate for VFAs production. Results indicated that the HAc production (77.38 g-C/kg-VS) was enhanced by 79 % in AD of FW with addition of 10 g/L Fe3O4. The duration to reach the maximum HAc production was also shortened from 14 days to 10 days. The AD tests using model substrates revealed that Fe3O4 enhanced hydrolysis, acidogenesis, and degradation of propionic acid, thus resulting in enhanced HAc production. The enhanced activities of hydrolytic and acid-forming enzymes, and electron transport system (ETS) with Fe3O4 addition further demonstrated its function as an electron acceptor to stimulate electron transfer and accelerate microbial metabolisms in AD, which contributed to the enhanced HAc production from FW.

A critical review of experimental and CFD techniques to characterize the mixing performance of anaerobic digesters for biogas production

A critical review of experimental and CFD techniques to characterize the mixing performance of anaerobic digesters for biogas production

Exploring CO2 Bio-Mitigation via a Biophotocatalytic/Biomagnetic System for Wastewater Treatment and Biogas Production

Carbon dioxide (CO2) emissions from fossil fuels have led industries to seek cheaper carbon abatement technologies to mitigate environmental pollution. Herein, the effect of a magnetic photocatalyst (Fe-TiO2) on biogas production in anaerobic digestion (AD) of wastewater was investigated with three bioreactors coupled with UV-light (18 W). Three experimental setups defined as the control (AD system with no Fe-TiO2), biophotoreactor (BP), and biophotomagnetic (BPM) systems were operated at a mesophilic temperature (35 ± 5 °C) for a hydraulic retention time (HRT) of 30 days. The control system (ADs) had no Fe-TiO2 additives. The BPMs with 2 g Fe-TiO2 were exposed to a magnetic field, whereas the BPs were not. The removal rate of the chemical oxygen demand (COD), volatile solids (VS), and total solids (TS), together with biogas production and composition were monitored for each reactor. The degree of degradation of 75% COD was observed for the BPMs at a pH of 6.5 followed by the BPs (65% COD) and the ADs (45% COD). The results showed that the rate of degradation of COD had a direct correlation with the cumulative biogas production of the BPMs (1330 mL/d) > BPs (1125 mL/d) > AD (625 mL/d). This finding supports the use of biophotomagnetic systems (BPMs) in wastewater treatment for resource recovery and CO2 reduction (0.64 kg CO2/L) as an eco-friendly technology.

Stabilization of Sludge in Zakho Municipal Wastewater by Anaerobic Digestion for Biogas Production in Kurdistan Region, Iraq

Raw wastewater sludge samples were collected from two sanitary point sources in Zakho city wastewater pipes. Anaerobic digestion is utilized sludge stabilization as it was effective in reducing the volume of sludge and cheap source of clean biogas. the sludge of municipal wastewater of Zakho district is worth to be used for the generation of biogas and just 15 -17 kg sludge produced 233 to 350 m3 gas in solid retention time of 18 and 24 day respectively. Suspended solid is close related to the amount of COD that removed from sludge and approximately 1 kg COD generate 0.5-0.55 Kg suspended solid in the water. Volatile solid (VS) /total solid (TS) ratio is 0.46 after anaerobic digestion which locate in the range of anaerobic lagoon stabilization. Anaerobic digestion lead to reduction in total solid of wastewater especially organic or volatile suspended solid. Specific gravity of the sludge solid is1.5 which indicate that the sludge is stabilized by anaerobic digestion. Sludge volume index (SVI) indicate that the settleable biosolids are old, good quality and low turbidity. Sludge density index (SDI) increased from 1.83 to 2.9 ml/g after stabilization by anerobic digestion. CO2 and H2S are reduced to zero after stabilization by anaerobic digestion. Nutrients N, P, Ca, Mg, Cl are elevated significantly in final stabilized sludge to be used as organic fertilizer, except sulfate is decreased to acceptable ranges after stabilization.

Enhancing biogas production in anaerobic digestion by the addition of oxidized and non-oxidized biochars

Anaerobic digestion (AD) is a well-known biological conversion process to obtain a gaseous biofuel from organic matter: in fact, upgrading biogas to biomethane is a mean to substitute conventional natural gas. It is also known that biochar can improve the biogas production in AD processes. In this work, different biochars have been produced from various feedstocks at different process conditions. Biochars obtained from the carbonization of wheat straw (WS) and poplar (P) were produced in a Thermo Gravimetric Analyser at lab scale, at a temperature of 400 °C and 2 h of retention time at the maximum temperature, with a heating rate of 20 °C min−1. Another biochar from poplar (Pc) was also produced in a pilot plant (CarbOn, RE-CORD) working in oxidative pyrolysis conditions, at a temperature range between 500 and 600 °C. Biochars were oxidized with Oxone® using two different methods (ball-milling and simple aqueous solution mixing) to increase the amount of functional groups on their surface. Oxidized biochars (Ws_Ox and P_Ox) were characterized by FTIR, BET, and CEC, and their impact on biogas production was investigated through a lab scale biochemical methane potential (BMP) test using maize silage as substrate. 0.33 g of biochar was used for each treatment. BMP test shows that all batches containing biochar as additive produced more biogas than control (C). WS_Ox and P_Ox produced respectively a + 7.7% and + 11.3% of biogas than C, obtaining the higher productivities with respect to not oxidized biochars. The addition of P and Pc biochars were similar performances in AD, thus highlighting that no significant differences are due to different biochar production scales and process parameters from the same feedstock. This study highlights how in addition to the various examined parameters (nature of the feedstock, pyrolysis parameters, size of biochar and its concentration in AD), also the presence of specific functional groups on the biochar surface influences the AD performance.

Availability and Co-Substrate Potential of Typha latifolia for Biogas Production in Funtua, Katsina State, Nigeria

In order to reduce global warming through fossil fuel utilization, biogas production from biodegradable biomass seems a sustainable alternative. This study evaluated the availability and co-substrate potential of T. latifolia for biogas production in Funtua, Katsina State Nigeria. A purposive sampling technique was used in selecting the wards that were used for this study. A 1204 metres transect was used for 32 quadrats; 19 of these were laid on the 953m contiguous land area at intervals of 50m; 9 quadrats covered 450m, 5 quadrats were on 250m, 3 on 153m, and 2 on 100m. The remaining 13 transects were laid on the 251m un-contiguous patches. Coordinates of various potentials sites were recorded using Global positioning system. There were an average of 27 T. latifolia stands per m2. A total of 32,388 of T. latifolia stands were recorded in the study area; Dukke ward (23,968), Makera (8,205) and Maska 216. T. latifolia is available in lqrge quantities, and a potential co substrate in anaerobic digestion for biogas production in Funtua. It is recommended that the study should be replicated in time later to establish a trend of the T. latifolia species in terms of population.

Impact of temperature, inoculum flow pattern, inoculum type, and their ratio on dry anaerobic digestion for biogas production

This study is aimed to apply dry anaerobic digestion (DAD) for methane (CH4) enriched biogas production from unsorted organic municipal solid waste (MSW). Cumulative biogas production was monitored for 35 days of operation in batch digesters at fixed feedstock to inoculum (F/I) ratio 2. Anaerobic sludge (AS) and cow manure (CM) were used as inoculum in single and mixed modes. Several process parameters such as inoculum flow pattern (single layer, multilayer, and spiral), digestion temperature (25 to 40 °C), inoculation modes (single and mixed mode), and inoculation proportion (AS:CM = 1:1, 1:2, 1:3, and 2:1) were investigated to determine the optimum DAD conditions to maximize the CH4 laden biogas yield. The study of inoculum flow pattern showed that digester with multilayer inoculum configuration generated the maximum 555 mL cumulative biogas with the production rate of 195 mL/day (at 25 °C). Biogas production rate and cumulative biogas production were found to increase with a rise in temperature and the maximum values of 380 mL/day and 1515 mL respectively were observed at 37 °C. The mixed mode of inoculation containing AS and CM augmented the biogas yield at previously optimized conditions. Final results showed that digester with multilayer inoculum flow pattern at 37 °C produced 1850 mL cumulative biogas with 1256.58 mL CH4/kg volatile solid (VS) when the mixed inoculum was used at the AS:CM—1:2 ratio. Biogas production with this significant amount of CH4 justifies the use of the DAD process for energy (biogas) generation from widely available biomass feedstock (MSW), offering various advantages to the environment.

Effect of Fe3O4 nanoparticles on microbial diversity and biogas production in anaerobic digestion of crude glycerol

This study investigated the effects of citrate-coated Fe3O4 nanoparticles in the anaerobic digestion of crude glycerol, the main by-product of the biodiesel industry. Fe3O4 nanoparticles were synthesized by the coprecipitation method and Scanning Electron Microscopy (SEM) characterized it. The method designed for synthesis produced stable Fe3O4 nanoparticles with diameters about 20 nm. Duplicate of anaerobic batch reactors (500 mL) were used for assessing the influence of Fe3O4 nanoparticles in four assays performed at 37 °C. The reactors were filled with anaerobic granular sludge; crude glycerol (25.0 g COD L−1); buffer solution; citrate-coated Fe3O4 nanoparticles suspension (0.2 g L−1; 0.4 g L−1 and; 0.8 g L−1 and a control without Fe3O4 nanoparticles); deionized water up to 250 mL. There were increases of 49.8%, 28.5% and 26.0% in the accumulated production of CH4 and 25.7%, 17.1% and 20.0% in the maximum rate of CH4 production in assays supplemented with 0.2, 0.4 and 0.8 g L−1 of Fe3O4 nanoparticles, respectively, in relation to control reactors. It was also observed a substantial increase on relative abundance of Bacteria and Archaea Domains, specially Bacteroides, Clostridiales, Methanomicrobiales and Methanosarcinales orders, after anaerobic digestion supplemented with Fe3O4 nanoparticles. The addition of Fe3O4 nanoparticles could improve the anaerobic digestion of crude glycerol, optimizing bacterial and archaeal communities enhancing the CH4 production.

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

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.

Effect of temperature and pH variation on anaerobic digestion for biogas production

A comparative analysis study of pH and temperature effects on the anaerobic digestion process of different agricultural wastes was carried out during the production of biogas. The investigation was in two phases. Phase one involved the use of a single substrate of cow dung, cassava peels, yam peels and pineapple peels while the second involved co-digestion of the substrates with cow dung. The composition of gas produced by a single substrate and a mixture of these substrates were determined. The feedstock for each experiment was a 1:1 mixture of the substrates with water. For the co-digestion, one part of the substrate and one part of cow dung were used with two parts of water, making the ratio 1:1:2. Routine measurements of pH and temperature of the feedstock were taken and the composition of the produced biogas was determined. It was deduced that cow dung co-digested with cassava peels gave a higher yield with methane content of 65.3% followed by cow dung only, co-digestion of cow dung and yam peels, cassava peels only, yam peels only and pineapple peels with 63.4%, 51.4%, 46.2%, 42.3% and 0.0%, respectively. Therefore co-digestion, with cow dung and cassava peels is most efficient for biogas production.

Anaerobic Digestion for Biogas Production from Municipal Sewage Sludge: A Comparative Study between Fine Mesh Sieved Primary Sludge and Sedimented Primary Sludge

Two different types of primary sewage sludge have been used as feedstock for production of biogas through anaerobic digestion (AD): the one type was sludge from a typical primary clarifier (PC), while the other type of sludge produced by a rotating belt filter, commonly called microsieve (MS). Initially the main physicochemical characteristics of the sludges, such as total solids (TS), volatile solids (VS), VS/TS, pH and carbon to nitrogen ratio (C/N) were determined, for MS: 37.86 ± 0.08%, 83.00 ± 0.41%, 0.83 ± 0.00, 6.67 ± 0.08 and 19.68 ± 0.69, respectively, and for PC: 2.61 ± 0.08%, 78.77 ± 1.91%, 0.79 ± 0.02, 6.61 ± 0.10 and 14.46 ± 1.23, respectively. Then, calculated amounts of the sludges were inserted into airtight vials and were inoculated using anaerobic sludge. The daily biogas production was measured over a period of 30 days. PC sludge maximized the daily biogas production (44.20 mlbiogas/gvsd) 11 days after inoculation, while the MS sludge reach a peak (37.74 mlbiogas/gvsd) 14 days after inoculation. The cumulative biogas production over the 30 days of AD was in the same laver (442.29 mlbiogas/gvs for PC versus 434.73 mlbiogas/gvs for MS). However, PC sludge indicated higher daily biogas production, compared to MS sludge, while the opposite was observed for the period following the peak point. The Volatile Solids Reduction for PC and MS sludges was recorded as 46.06% and 32.39%, respectively.

Enhanced biogas production in anaerobic digestion of sludge medicated by biochar prepared from excess sludge: Role of persistent free radicals and electron mediators

The addition of biochars to promote the efficiency of anaerobic digestion (AD) has widely received concerns. However, the role of persistent free radicals (PFRs) and the electron transfer ability of biochar in AD has not yet been noticed. In this study, biochars were prepared from excess sludge under 400 °C (B400) or 600 °C (B600) and different ratios of sludge to biochar (5:1, 10:1, 20:1) were applied in the AD of sludge. The results verified that PFRs in biochar participated in the sterilization of microorganisms in sludge, resulting in the release of organic matters. Similar to electron mediators, biochars possessed electron exchangeability and the addition of biochars boosted the biogas production by maximum of 54.5%. The enhancing effect of B400 surpassed that of B600 as high temperature destroyed functional groups and reduced the defect degree of biochar. This study achieved in-situ resource utilization and provided references for the improvement of anaerobic digestion.

Development of an innovative MFC-biosensor for real-time monitoring of anaerobic digestion for biogas production: Controlled substrate feeding strategy

A microbial fuel cell (MFC) based biosensor was designed to monitor volatile fatty acids (VFAs) in anaerobic digestion (AD) to control substrate feeding. The VFAs concentrations 7–40.83 mM showed a linear relationship with biosensor voltage (18–67 mV) indicating that voltage < 18 mV was due to low organic matter. Likewise, VFAs concentration lower than 7.87 mM resulted in decreased biogas production rate (BPR) and required substrate feeding. In a continuous food waste AD, the biosensor guided feeding produced 558 mL/g VS with the highest biomethane (62.17%), comparing with 344 and 387 mL/g VS produced by conventional 3- and 7-days intervals feeding, respectively. The microbial community was also more stable under the new strategy, where Prevotella and Methanosarcina were ~6-fold and 1.5-fold higher than conventional groups. The developed portable biosensor (~$200) worked effectively during outdoor monitoring of a domestic biogas plant. The VFAs based MFC biosensors can enhance the biogas yield with minimum substrate feeding while maintaining a suitable microbial community.