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This review addresses the critical issue of a rapidly increasing worldwide waste stream and the need for sustainable management. The paper proposes an integrated transformation toward a next-generation methanization process, which leads not only to treating waste but also to converting it into higher value compounds and greener energy. Although the current and commonly used anaerobic digestion process is useful for biogas production, it presents limitations of resource exploitation and some negative environmental impacts. Focusing on the acidogenic stage in waste stream processing, the paper discusses the recent strategies to enhance the recovery of volatile fatty acids (VFAs). These acids serve as precursors for synthesizing a variety of biochemicals and biofuels, offering higher value products than solely energy recovery and soil fertilizers. Additionally, the importance of recycling the fermentation residues back into the biorefinery process is highlighted. This recycling not only generates additional VFAs but also contributes to generating clean energy, thereby enhancing the overall sustainability and efficiency of the waste management system. Moreover, the review discusses the necessity to integrate life cycle assessment (LCA) and techno-economic analysis (TEA) to evaluate the environmental impacts, sustainability, and processing costs of the proposed biorefinery. [ABSTRACT FROM AUTHOR]

For optimum methanization of cotton residues, four (4) samples were made up in vases, with cotton residues as the main component. The first sample consisted of 30g of cotton residue and 270 ml of inoculum, the second of 30g of cotton residue, 270 ml of inoculum and 0.1g of sodium, the third of 15 g of cotton residue, 270 ml of inoculum and 15g of cow dung, and the fourth of 15g of cotton residue, 270 ml of inoculum, 15g of cow dung and 0.1g of sodium. It took 75 days to digest the 30 g of organic matter contained in each sample. The results of this study showed that the sample 4, made up of cotton residue, inoculum, cow dung and sodium, gave the highest biogas volume (1.068 m3), methane volume (0.66 m3) and methane content in the biogas (89%). The best conditions for optimal biogas production from cotton residues are those of a combination of cotton residues, inoculum, cow dung and sodium ash. The results of this study provide knowledge for choosing the optimum conditions for the methanization of organic matter from agricultural waste. [ABSTRACT FROM AUTHOR]

The formation of natural lakes is a process that takes place over thousands of years, although the volumetric formation depends on hydrological and climatological phenomena, reaching a stationary hydraulic regime, the evolution of hydrochemistry is more complex and obeys not only phenomena of stoichiometry and chemical kinetics but also diffusion processes. Depending on the depth of the lakes, the anoxization process originating from the bottom is the first phase of the lake's methanogenesis. For this, the course of many thousands of years is necessary, so the studies carried out in the lakes are limited to the current knowledge of the state in which they are, without being able to have real information in this process of methanogenesis. There are no data available on the generation process of a natural lake in its primary stages. In this case, taking advantage of the rehabilitation of the old open-pit mining of Meirama (Northwest Spain), consisting of the controlled flooding of the hole by groundwater, by stopping the perimeter pumping, and the derivation of the nearby streams, whose contribution was the majority with respect to the subterranean contribution, there has been the opportunity to physically and chemically monitor the complete filling of the said hole. The present study focuses on the analysis of the evolution of the different processes initiated in the methanogenesis of the lake bottom identified in the well-known Redox ladder: obtaining oxygen from the reduction of nitrogenous compounds and metallic oxides, from the reduction of the sulfate and the generation of methane from carbon compounds, the latter phase without reaching. Although the methanization process is very slow, it has had the opportunity to know the formation of a lake at its origin, from the hydrochemical point of view. It has been possible to verify that the methanization processes at the bottom, given the anoxia conditions, are in a very primitive phase with the reduction of nitrate and nitrite to ammonium and beginning a reduction of metal oxides and sulfate. [ABSTRACT FROM AUTHOR]

In Chlef, the management of urban solid bio-waste is limited to "all in controlled landfill or in wild landfill". This bio-waste can be treated by composting-methanization. With this in mind, two temperature regimes were chosen, the mesophilic regime (35°C) and the thermophilic regime (55°C). The choice of a neutral pH is an optimal value indicating the stability and the good progress of the anaerobic digestion. As well as monitoring the parameters of the composting process. The results of the composting process show that the values of temperature (35°C to 62°C), pH (5 to 8), moisture content (60% and 40%) and percentage of organic matter (74% to 41%) indicate that the fermentation process is going well. The composting process enters the cooling phase after 60th day of fermentation. While the results of the methanization show that a substrate with an organic matter content of 73% causes an accumulation of acids in the digester and a stop of the reaction in mesophilic conditions. Therefore, the thermophilic mode is more suitable for the anaerobic degradation of raw bio-waste. The tests were conclusive in obtaining a flammable biogas. The values of the VFA (Volatile Fatty Acid)/ACT (Alkalimetric Title) ratios below 0.1 show the good functioning of the anaerobic digestion. The methanization of two masses of substrate at the beginning and during the cooling phase of composting allows a gain in residence time, thus a lower energy cost. [ABSTRACT FROM AUTHOR]

Slaughterhouses generate highly polluted effluents, and if not treated before discharge can cause major adverse environmental and public health impacts. Treatment of this waste by anaerobic digestion can reduce those impacts while producing a potentially valuable source of energy. The purpose of this study was to investigate this process efficiency under pilot operating conditions for a more accurate scaling up. Blood waste from a slaughterhouse was treated in a pilot‐scale digester of 30 dm3 total volume under mesophilic temperature conditions. Operating parameters such as pH, alkalinity, organic loading, volatile fatty acids, biogas composition, total and volatile solids were monitored in order to study the behavior of the fermentation process. The results show that no significant inhibition were caused by the accumulation of volatile fatty acids, due to the high buffering capacity of treated sludge. An efficient reduction of organic matter was obtained with a COD decrease of about 67% within 40 days of fermentation. The biogas produced was of a good quality with high CH4 yields (above 70%) and low CO2 yields, corresponding to a biomethane potential of 225.9 dm3 CH4/kg TVS. Logistic model described accurately the methane production kinetic and enables an easy process scaling up for industrial applications. [ABSTRACT FROM AUTHOR]

Anaerobic digestion (AD) or methanization is a biological process that allows the treatment of organic wastes and the production of renewable energy as biogas. This research describes assessment and optimization of dates pedicels rich in organic components under the conditions of mesophiles in co-digestion in association with the cattle manure and sludge of the wastewater treatment plant (WWTP). To realize this objectives, we investigated the impact of substrate load (date pedicel) on the co-digestion anaerobic of date pedicels and the sludge in wastewater treatment plants. The different parameters of the digester stability such as the pH, VFA, CAT, ammoniacal nitrogen, and the volume of biogas produced were followed. The results show that by increasing the mass of the pedicels and therefore the percentage of the substrate in the reactor, from 0.5 to 1% (W/V), the volume of produced biogas increases by five times. However, an increase in the percentage of the substrate introduced into the digester from 1 to 2% resulted in a slight decrease in the volume of biogas produced. The use of fresh cattle manure as inoculum shown a significant improvement (40%) in the production of biogas, which can be attributed to the nature of the inoculum. Indeed, cattle manure fresh is more adapted for the fermentation of lignocellulosic materials unlike sludge of wastewater treatment plants which may contain toxic substances that limit their use in AD. HIGHLIGHTS Pedicels of dates mixed with cattle manure and sludge from the waste water treatment plant (WWTP) were effective feedstocks for biogas production.; Production optima of biogas are 1395 mL for WWTP and 1953.4 mL for cattle manure.; Load maximum admissible in a digester depends on the nature of the substrate.; Use of fresh cattle manure as the inoculum is more adapted for the fermentation of lignocellulosic materials.;

Facilitating the circulation of resources and knowledge in territories is a key dimension in the transition to a circular economy. The purpose of this article is to identify the factors and dynamics of development of circularity at meso-economic level through the study of the eco-innovations on which it is based. We study collective methanization projects in the South-West of France. We use a mixed method, 'quantified narrative method' to characterize the development process of the projects via the nature of the resources mobilized and how they have been acquired. The analysis of the 167 resources mobilized highlights technological and organizational eco-innovation dynamics that support the development of circular economy in rural areas. Our results confirm the role of three eco-innovation factors: local resources, sectoral and institutional environments, i.e. place-based and extra-local factors. They also highlight the importance and interdependence of local and regional networks of project leaders, institutional actors and market actors. The construction of circularity results in exchanges between the agricultural and energy sectors, which intensify throughout the projects, thus reinforcing the effects of related variety. However, this circularity remains incomplete and could be reinforced through public policies designed to help these projects gain a stronger foothold. [ABSTRACT FROM AUTHOR]

BACKGROUND During anaerobic digestion of wastes, volatile fatty acid (VFA) production has been studied, but little attention has been paid to alcohols and lactic acid. Thermodynamically, lactic acid and alcohols are better substrates to produce methane than other VFA. This research identified the metabolites produced during the fermentation of the organic fraction of municipal solid waste and studied their methanization in a second stage. Analysis of the methane production curves is provided and explained according to Gibbʼs free energy of acetogenesis and methanogenesis. Based on the Michaelis–Menten model, a kinetic analysis is presented. RESULTS: The specific methane production of the identified acids and alcohols are acetic acid, 343 NL/kgCOD; ethanol, 296; methanol, 181; butyric acid, 108; lactic acid, 64. Lactic and butyric acids present a long adaptation phase followed by a fast and short methane production. Acetic acid and ethanol finished the reaction in less than 16 h. The highest methane production rates (Vmax) were for butyric acid, methanol, and ethanol with 2136, 1934, and 1928 NmL L–1, respectively. The best affinity (lowest Km) values were for acetic and lactic acids and ethanol with 1.2, 1.9, and 2.0 gCOD L–1. CONCLUSION: Together, acetic acid and ethanol represent 92% of all fermentation products. No endogenous methane production was observed during the methanization from acetic acid and ethanol. The highest specific methane production belongs to acetic acid (98% of the theoretical) and the lowest corresponds to lactic acid. Except for propionic acid, the methanization of the selected substrates follows the Michaelis and Menten model. © 2021 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

Data in this article provides detailed information on the microbial dynamics and degradation performances in two full-scale anaerobic digesters operated in parallel for 476 days. One of them was kept at 35 °C for the whole experiment, while the other was submitted to sub-mesophilic (25 °C) conditions between days 123 and 373. Sludge samples were collected from both digesters at days 0, 80, 177, 218, 281, 353, and 462. The provided data include the operational conditions of the digesters and the characterization of the sludge samples at the physicochemical level, indicative of the digesters’ degradation performance. It also includes the characterization of the sludge samples at the multiomics level (16S rRNA gene sequencing, metagenomics, and metabolomics profiling), to decipher the changes in the microbial structure and molecular activity. The 16S rDNA gene sequencing, metagenomics, and metabolomics data were generated using an IonTorrent PGM sequencer, an Illumina NextSeq 500 sequencer, and LTQ-Orbitrap XL mass spectrometer respectively. The 16S rDNA gene raw data and the metagenomics data have been deposited in the BioProject PRJEB49115, in the ENA database (https://www.ebi.ac.uk/ena/browser/view/PRJEB49115). The metabolomics data has been deposited at the Metabolomics Workbench, with study id ST002004 (DOI: 10.21228/M8JM6B). The data can be used as a source for comparisons with other studies working with data from full-scale anaerobic digesters, especially for those investigating the effect of the temperature modification. The data is associated with the research article “Metataxonomics, metagenomics, and metabolomics analysis of the influence of temperature modification in full-scale anaerobic digesters” (Puig-Castellví et al [1]).

Algeria is experiencing a crucial need in municipal solid waste management improving system. According to the National Agency or Waste (- AND) more than 11 million tons of waste are produced annually, and this production is growing significantly. Algerian cities have to deal with the hard situation of the increase in the amount of waste produced. This results in environmental degradation and a risk to public health. Biogas technology is one of the technologies that have continued to receive a lot of attention. In Algeria, the first biodigester was constructed in 1938 under the impulse of two teachers of the National School of Agriculture of Algiers Ducellier and Isman. That work has been considered as precursor of the biogas production mastery not only in Algeria but also at the world level. Based on their patent, many agricultural installations were equipped with gas digesters of manure, and that various pieces of equipment of valorization of biogas have been developed. The main benefits of biogas technology include its ability to add value to biomass chains by closing equipment cycles and enabling improved fuel efficiency. Taking into account the interests presented above, the objective of this work is to extrapolate the current environmental regulatory side for the Algerian case in terms of energy recovery of fermentable organic waste via the production of biogas, and to propose a law on the energy transition-biomass to accelerate the deployment of this renewable energy. We are interested in the topic of organic municipal waste management in the case of Algeria. The aim is to contribute to a new waste recovery policy based on theoretical and practical knowledge. These instructions presents guidelines for preparing papers.

Résumé: Des unités de production de biogaz sont de plus en plus souvent implantées en Europe. Cette filière de traitement des déchets organiques, en plein essor, est caractérisée par une grande diversité, aussi bien en termes de procédés qu'en termes de déchets traités. Le caractère fermentescible des déchets peut être à l'origine de l'émission de composés chimiques dont certains, du fait de leur caractère odorant, peuvent générer des nuisances. L'objet de cette étude était de caractériser ces émissions, en les analysant sur trois sites de méthanisation. Il a pu être montré que certaines activités ponctuelles, mais récurrentes, telles que les chargements/déchargements de camions ou les préparations des intrants, sont la source principale des nuisances odorantes subies par les riverains de ces sites. The number of biogas production plants is increasing in Europe. This fast-growing organic waste treatment industry uses a variety of processes to treat many different types of waste. The fermentable nature of some types of waste may lead to the emission of chemical compounds, some of which may be sources of annoyance because of their odor. The purpose of this study was to characterize these emissions by analyzing them at 3 methanization sites. The results show that certain specific but recurring activities, such as truck loading/unloading and input preparation, are the main source of annoying odors in the neighborhood. [ABSTRACT FROM AUTHOR]

Biogas is an ideal fuel for sustainable energy and an alternative to wood energy in sub-Saharan Africa. Its valorisation in rural areas is limited to cooking despite its enormous potential for electricity production. However, the inaccessibility of biogas analyzers to assess the quality of biogas and trigger its use in an engine is one of the main obstacles to this new trend. The aim of this work is to develop a simple and inexpensive portable digital device capable of analysing any biogas together with its production parameters. To achieve this, a prototype analyser using an Arduino card fitter with sensors was designed and built, then experimented with biogas produced from cow dung. Sampling tests were carried out after 4 and 10 days of loading 10-liter bioreactors with cow dung. A Better flammable biogas production was recorded at 10 days of loading with 66.41% methane (CH4), 32.43% CO2, and 1.14% water vapour (H2O). This biogas analyser was quite efficient and could identify gases produced by the methanization process while controlling the bioconversion parameters. Nonetheless, the biogas obtained can be purified for more efficient use.

Renewable energy projects are far from being unanimously accepted at local level, while they are often supported by public opinion as a mean of combating climate change. Most of the time, the NIMBYist attitude is invocated as a factor explaining these local oppositions. However, we believe that social acceptability is a much more complex phenomenon. The objective of the study is therefore to identify the factors that explain the differences in terms of social acceptability. To do this, we rely on the case of the deployment of methanization in France, through the analysis of semi-directive interviews conducted with 49 project stakeholders. Our results suggest that NIMBYism is not the main factor explaining the difficulties of social acceptability in renewable energy projects. This principle only very rarely explains the behaviour of local residents (opposition and support) towards methanization units. Other much more important parameters come into play. For example, methanization units are more easily accepted when they are accompanied by an overall policy of territorial governance based on the creation of trust, a systematic integration of all stakeholders, including those who might be opposed to them. Relationship-based management at an early stage of the project considerably increases social acceptability. Our paper put forward the role of territorial governance but also of place-attachment as major parameters to explain a greater or lesser degree of local acceptability. Far from being perceived as a hindrance to a project, citizen opposition must be understood as an integral part of territorial governance, calling for the implementation of more participatory approaches.

Highlights • Biomethanation of cattle manure was validated in a 100 L digester. • Permeation membranes were used to strongly limit undissolved H 2 in the biogas. • A linear relationship was clearly shown between biogas CH 4 content and H 2 flowrate. • Biogas production was probably limited by CO 2 transport within the bioreactor. Abstract This study aimed at studying the biomethanation process using a 100 L pilot-scale digester equipped with a dense membrane for hydrogen injection. Hydrogen mass transfer was characterized and the impact of hydrogen flowrate, agitation rate and of the co-injection of CO 2 , on biogas production and composition, was precisely studied. A linear relationship between H 2 flowrate and the CO 2 and CH 4 rates in biogas was found but no impact on biogas flowrate was shown. It was also noticed that, without exogenous CO 2 injection, and for high H 2 injection flowrates, residual H 2 could be found at the digester outlet due to local CO 2 limitation. Thus, this study suggested that biogas production in biomethanation process at the pilot scale was probably rather limited by the dissolved CO 2 transport within the liquid phase than by the hydrogen mass transfer itself. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Temperature was shown to have a strong influence on microbial populations. • Archaea adapt slowly after temperature shock and are temperature specific. • Temperature tolerant Bacteria are the main drivers for a rapid recovery. • Methanobacterium is the first Archaea to recover after return to mesophilic condition. • Ruminococcaceae are driver of reactor resilience after return to mesophilic condition. Abstract Temperature is a key parameter of anaerobic digestion. Its modification can have drastic consequences on microbial communities and performances. However it can be an interesting parameter to adjust the productivity, energy efficiency or stability of bioreactors. The objective of this work was to give insights into the consequences of abrupt temperature modifications on the microbiota of anaerobic digestion. Two complementary experiments were performed. A continuously stirred lab-scale bioreactor (5-L) simulated the functioning of a semi-continuous industrial digester. Five batch-fed incubations (1-L) served as replicated experiments. Each experiment was divided into three successive steps: reactors were first operated at 35 °C followed by an abrupt increase to 55 °C and finally a decrease to 35 °C. After the first temperature shock, gas production rate increased temporarily and then fell for 1 month before a new steady-state was reached. When temperature was reset to 35 °C in step 3 gas production decreased sharply again. The semi-continuous reactor recovered after 15 days while the batch-fed incubations never recovered. Ecological changes associated to these performance drops and recovery were sought using 16S sequencing of Bacteria and Archaea and multivariate analyses. In brief, Bacteroidales order was rapidly and strongly affected by temperature increase, while Clostridiales became dominant in thermophilic conditions. Several thermotolerant Bacteria were identified as responsible for reactors early recovery, but were outcompeted by a very diverse bacterial population a few weeks after temperature shock. Methanosarcina and Methanobacterium Archaea dominated at 35 °C but were slowly replaced by thermophilic Methanoculleus or Methanosarcina at 55 °C that were essential to methane production. In step 3, when returning to initial temperature conditions after the thermophilic period, Ruminococcaceae and Methanobacterium appeared to drive digester resilience. [ABSTRACT FROM AUTHOR]

We described mathematically the process of peat methanization in a boreal mesotrophic fen. Gaseous and dissolved CH4 and CO2 as well as their δ13C signatures were considered in the dynamic equations for incubation bottles. In accordance with the model, acetate, H2, and CO2 were produced during cellulose hydrolysis and acidogenesis. 13C/12C in CO2 was a key variable reflecting dynamic changes in the rates of cellulose hydrolysis and acidogenesis, acetoclastic and hydrogenotrophic methanogenesis. As CO2 is the substrate in hydrogenotrophic methanogenesis, δ13C-CO2 increased from the start till the dissolved hydrogen concentration became very low. Thereafter, the rate of acetoclastic methanogenesis with the significant current acetate concentration dominated over the rate of hydrogenotrophic methanogenesis leading to the decreasing δ13C-CO2 and the increasing δ13C-CH4. The model was validated by describing the system’s dynamics under strong and weak inhibition of acetoclastic and hydrogenotrophic methanogenesis by methyl fluoride, respectively. During peat methanization at the lowered temperature of 10 °C, the processes of hydrogenotrophic methanogenesis and homoacetogenesis competing for H2 may occur. However, based on dynamics of the carbon isotope signatures, especially on dynamics of δ13C-CO2, the model showed no significant contribution of homoacetogens in peat methanization. [ABSTRACT FROM AUTHOR]

A wide variety of inhibitors can induce anaerobic digester disruption. To avoid performance losses, support media can be used to mitigate inhibitions. However, distinguishing the physico-chemical from the biological mechanisms of such strategies remains delicate. In this framework, the impact of 10  g/L of different types of zeolites and activated carbons (AC) on microbial community dynamics during anaerobic digestion of biowaste in the presence of 1.3 g/L of phenol was evaluated with 16 S rRNA gene sequencing. In the presence of AC, methanogenesis inhibition was rapidly removed due to a decrease of phenol concentration. This abiotic effect related to the physico-chemical properties of AC led to increased final CH4 and CO2 productions by 29–31% compared to digesters incubated without support. Interestingly, although zeolite did not adsorb phenol, final CH4 and CO2 production reached comparable levels as with AC. Nevertheless, compared to digesters incubated without support, methanogenesis lag phase duration was less reduced in the presence of zeolites (5 ± 1 days) than in the presence of activated carbons (12 ± 2 days). Both types of support induced biotic effects. AC and zeolite both allowed the preservation of the major representative archaeal genus of the non-inhibited ecosystem, Methanosarcina . By contrast, they distinctly shaped bacterial populations. OTUs belonging to class W5 became dominant at the expense of OTUs assigned to orders Clostridiales , Bacteroidales and Anaerolinales in the presence of AC. Zeolite enhanced the implantation of OTUs assigned to bacterial phylum Cloacimonetes . This study highlighted that supports can induce biotic and abiotic effects within digesters inhibited with phenol, showing potentialities to enhance anaerobic digestion stability under disrupting conditions. [ABSTRACT FROM AUTHOR]

The effects of microbial electrolysis cells (MECs) at three applied voltages (0.8, 1.3, and 1.6 V) on simultaneously enhancing methanization and reducing hydrogen sulfide (H 2 S) production in the anaerobic digestion (AD) of sewage sludge were studied. The results showed that the MECs at 1.3 V and 1.6 V simultaneously enhanced the methane production by 57.02 and 12.70% and organic matter removal by 38.77 and 11.13%, and reduced H 2 S production by 94.8 and 98.2%, respectively. MECs at 1.3 V and 1.6 V created a micro-aerobic conditions for the digesters with oxidation-reduction potential as −178∼-232 mv, which enhanced methanization and reduced H 2 S production. Sulfur reduction, H 2 S and elemental sulfur oxidation occurred simultaneously in the ADs at 1.3 V and 1.6 V. The relative abundances of sulfur-oxidizing bacteria increased from 0.11% to 0.42% and those of sulfur-reducing bacteria decreased from 1.24% to 0.33% when the applied voltage of MEC increased from 0 V to 1.6 V. Hydrogen produced by electrolysis enhanced the abundance of Methanobacterium and changed the methanogenesis pathway. [Display omitted] • The effects of high applied voltages on MEC-AD of sewage sludge were studied. • Methanization enhancement and H 2 S production reduction was simultaneously realized. • High voltages (1.3 V and 1.6 V) created micro-aerobic condition for the AD. • High voltages increased the abundances of SOB and decreased those of SRB. • High voltages enhanced the hydrogenotrophic methanogenesis. [ABSTRACT FROM AUTHOR]

This study aimed at providing a better understanding of the influence of support media (10 g/L of zeolites, 10 g/L of activated carbons, and 1 g/L of chitosan) on key phylotypes steering anaerobic digestion (AD) performance in presence of 19 g/L of Total Ammonia Nitrogen (TAN) within batch digesters. Support media did not influence TAN concentration. However, both zeolites and activated carbon 1 reduced methanization lag phase by 47% and 25%, respectively. By contrast, activated carbon 2 and chitosan led to an increase of methanization lag phase by 51% and 32%, respectively. 16S rRNA gene sequencing revealed that zeolites preserved Methanosarcina and enhanced Methanobacterium. In presence of activated carbon 1, Methanoculleus , became predominant earlier than without support while chitosan and activated carbon 2 limited its implantation. This study highlighted potentialities to use supports to enhance AD stability under extreme TAN concentration and evidenced their specific influence on the microbiota composition. [ABSTRACT FROM AUTHOR]

Organic-rich shales are populated by methanogenic consortia that are able to degrade the fossilized organic matter into methane gas. To identify the organic fraction effectively degraded, we have sequentially depleted two types of organic-rich rocks, shales and coal, at two different maturities, by successive solvent extractions to remove the most soluble fractions (maltenes and asphaltenes) and isolate kerogen. We show the ability of the consortia to produce methane from all rock samples, including those containing the most refractory organic matter, i.e. the kerogen. Shales yielded higher methane production than lignite and coal. Mature rocks yielded more methane than immature rocks. Surprisingly, the efficiency of the consortia was not influenced by the removal of the easily biodegradable fractions contained in the maltenes and asphaltenes. This suggests that one of the limitations of organic matter degradation in situ may be the accessibility of the carbon and energy source. Indeed, bitumen has a colloidal structure that may limit the accessibility to asphaltenes in the bulk rock. Solvent extractions might favor the access to asphaltenes and kerogen by modifying the spatial organization of the molecules in the rock matrix.

A wide variety of inhibitory substances can induce anaerobic digester upset or failure. In this work the possibility to improve the resistance of an anaerobic microbiota to a common pollutant, the phenol, was evaluated in a lab-scale semi-continuous bioreactor. An acclimation strategy, consisting in a regular step-wise adaptation of the microbiota to stressful condition was employed. Degradation performances were monitored and molecular tools (16S sequencing and ARISA fingerprinting technique) were used to track changes in the microbial community. The acclimation strategy progressively minimized the effect of phenol on degradation performances. After 3 successive disturbance episodes, microbiota resistance was considerably developed and total inhibition threshold increased from 895 to 1942 mg/L of phenol. Microbiota adaptation was characterized by the selection of the most resistant Archaea OTU from Methanobacterium genus and an important elasticity of Bacteria , especially within Clostridiales and Bacteroidales orders, that probably enabled the adaptation to more and more stressful conditions. [ABSTRACT FROM AUTHOR]

Performance stability is a key operational issue for anaerobic digestion (AD) and phenolic compounds are regularly mentioned as a major cause of digester failures. To get more insights into AD microbiota response to a wide range of inhibition levels, anaerobic batch toxicity assays were conducted with ten phenol concentrations up to 5.00 g/L. Final AD performance was not impaired up to 1.00 g/L. However, progressive shifts in microbial community structure were detected from 0.50 g/L. The methanogenic function was maintained along with increasing initial phenol concentrations up to 2.00 g/L thanks to the emergence of genus Methanoculleus at the expense of Methanosarcina . Within syntrophic populations, family Syntrophomonadaceae proportion was gradually reduced by phenol while Synergistaceae gained in importance in the microbiome. Moreover, at 2.00 g/L, the relative abundance of families belonging to order Clostridiales dropped, leading to the predominance of populations assigned to order Bacteroidales even though it did not prevent final AD performance deterioration. It illustrates the high level of adaptability of archaeal and bacterial communities and suggests the possibility of determining early warning microbial indicators associated with phenol inhibition. [ABSTRACT FROM AUTHOR]

In natural settings, anaerobic digestion can take place in a wide temperature range, but industrial digesters are usually operated under either mesophilic (~35 °C) or thermophilic (~55 °C) conditions. The ability of anaerobic digestion microbiota to switch from one operating temperature to the other remains poorly documented. We therefore studied the effect of sudden temperature changes (35 °C/55 °C) in lab-scale bioreactors degrading C-labelled cellulose. An asymmetric behaviour was observed. In terms of methane production, after an adaptation period, mesophilic inoculum exhibited a functional resistance to temperature increase but no functional resilience when temperature was reset to 35 °C, while thermophilic inoculum methanogenic activity strongly decreased under mesophilic conditions but partially recovered when temperature was reset to 55 °C. Automated ribosomal intergenic spacer analysis community fingerprints evidenced a strong influence of temperature on microbial diversity, particularly pronounced and persistent for Archaea. Key phylotypes involved in C-cellulose degradation were identified with a coupled stable isotope probing (SIP)-16S rDNA pyrotag sequencing approach, suggesting that the hydrolytic and fermentative metabolic functions could be maintained thanks to functional redundancy between members of the class Clostridia, whereas methanogenic activity primarily relied on specialized groups affiliated either to genus Methanosarcina (mesophilic conditions), Methanothermobacter or Methanoculleus (thermophilic conditions) that were irreversibly modified by temperature increase. [ABSTRACT FROM AUTHOR]

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Magnified preparation of the catalyst was studied in this paper. Activity and stability of the catalyst were evaluated through long period, and deactivation mechanism of the catalyst was studied. The study result showed that average conversion of CO and H2 reached 99. 9% and 9.8% respectively, average selectivity of CH4 attained 98. 5%, and the activity of application catalyst was stable after continuous running of 1 000 hours. Deactivation mechanism study of the catalyst showed that the causes of catalyst deactivation with long period operation were carbon deposition and sintering, in which sintering is the main factor resulting in the decrease of catalyst activity. [ABSTRACT FROM AUTHOR]

Abstract: Clear economic advantages may be obtained from the management of seasonal fruit wastes by codigestion at existing facilities which are working throughout the year with other residues. We have explored the biomethanization of pear residues in a 5L stirred reactor loaded with sludge from the anaerobic digester of a municipal wastewater treatment plant. Different organic loading rates (OLRs) of fruit waste were tested with two delivery procedures: a discontinuous one (fed once a day) and a pseudocontinuous one. For both procedures, as the OLR increases the pH of the digester drops to acidic values and large OLRs may cause the reactor failure. Nevertheless, the pseudocontinuous delivery allows the treatment of more residue, (10.5 versus 6.0g of volatile solids per litre of reactor and day), maintaining the specific biogas production (0.44L of biogas per gram of volatile solids), with some improvement in methane concentration (44% vs 39%). [Copyright &y& Elsevier]

Abstract: Landfill leachate (LFL) collected from the controlled discharge of Jebel Chakir in Tunisia was treated without any physical or chemical pretreatment in an anaerobic membrane bioreactor (AnMBR). The organic loading rate (OLR) in the AnMBR was gradually increased from 1gCODl−1 d−1 to an average of 6.27gCODl−1 d−1. At the highest OLR, the biogas production was more than 3 volumes of biogas per volume of the bioreactor. The volatile suspended solids (VSSs) reached a value of approximately 3gl−1 in the bioreactor. At stable conditions, the treatment efficiency was high with an average COD reduction of 90% and biogas yield of 0.46l biogas per g COD removed. [Copyright &y& Elsevier]

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Anaerobic conversion of dairy manure into biogas is an attractive way of managing this waste. It is well known that the hydrolysis of large molecules into small, directly biodegradable ones is the rate limiting step of the overall anaerobic process. The present work studies the development of the hydrolytic and acidogenic stages of dairy manure with different solid concentrations (40, 60 and 80 g VS/L) at ambient temperature (20 °C). The purpose was to determine the operational conditions that provide a liquid fraction with a high soluble chemical oxygen demand (COD) and a high volatile fatty acids (VFA) content in manure before the methanogenic stage starts up. At 20 °C, the evolution of the studied parameters showed that, in a controlled plug-flow dung pit, the hydrolytic and acidogenic stages progressed moderately in a continuous way during the 25 days that the experimentation lasted, whereas no methanization was observed. Supernatant COD and VFA concentrations increased 30% and 107%, respectively, for the 60 g VS/L samples. Manure was also operated at 35 °C with a similar increase in supernatant COD but a higher increase in VFA, 154%. For both operational temperatures, the predominant VFAs were, in this order, acetic, propionic and butyric acids. During the operation at 35 °C, the methanogenic stage started between days 20 and 25 for the samples with lower solids content, i.e. 40 and 60 g VS/L. [ABSTRACT FROM AUTHOR]

Reconstituted municipal solid waste (MSW) with varying contents of putrescible and cellulosic waste was incubated anaerobically under mesophilic conditions. Standard physicochemical parameters were monitored, together with stable isotopic signatures of produced CH4 and CO2. δ13C values for CH4 indicated a change of methanogenic metabolism with time. CH4 was predominantly produced from H2/CO2 at the beginning of the incubations. This period was associated with important shifts in archaeal communities monitored by automated ribosomal intergenic spacer analysis (ARISA) and FISH of oligonucleotidic probes targeting specifically 16S rRNA gene of various methanogenic groups. The onset of the active methane generation phase was characterized by an increase of CH4δ13C, indicating a progressive shift toward an aceticlastic metabolism. When the methane production levelled off, a decrease in the isotopic signature was observed toward values characteristics of hydrogenotrophic metabolism. ARISA profiles were, however, found to be stable from the beginning of the active methane generation phase until the end of the experiment. FISH observation indicated that members of the family Methanosarcinaceae were predominant in the archaeal community during this period, suggesting that these methanogens might exhibit a high metabolic versatility during methanization of waste. [ABSTRACT FROM AUTHOR]

Thermal treatments with temperature ranging from 60 to 210°C were applied to 6 waste-activated sludge samples originating from high or medium load, extended aeration wastewater treatment processes that treated different wastewaters (urban, urban and industrial or slaughterhouse). COD sludge solubilisation was linearly correlated with the treatment temperature on the whole temperature range and independently of the sludge samples. Sludge batch mesophilic biodegradability increased with treatment temperature up to 190°C. In this temperature range, biodegradability enhancement or methane production increase by thermal hydrolysis was shown to be a function of sludge COD solubilisation but also of sludge initial biodegradability. The lower the initial biodegradability means the higher efficiency of thermal treatment. [ABSTRACT FROM AUTHOR]

Milk fat is considered to be the main limiting component of the kinetics of dairy wastewater anaerobic digestion. The objective of this work was to give a better understanding of the nonelucidated anaerobic degradation steps of milk fat. For that purpose, the kinetics of fat degradation was quantified in comparison with other milk components (lactose, proteins), regarding the milk fat polluting load and structure [globular (native state), triglycerides]. This work confirms that milk fat is degraded after a lag phase of several days, with a maximal degradation rate 2 to 5 times less than the degradation rate of the other milk components. It was shown that (1) the structure of the fat does not influence the limits of its anaerobic degradation; (2) the lag phase before biogas production is mainly due to unsaturated free fattyacids (FFA); and (3) conversion to biogas occurs at a lower rate for saturated than for unsaturated FFA. Therefore, the prehydrolysis of fat, which increases the instantaneous concentration of unsaturated FFA, sharply increases the length of the lag phase with no significant change in the maximal biogas production rate. To reduce the delay imposed in the biogas production, it is necessary to reduce the concentration of unsaturated FFA. [ABSTRACT FROM AUTHOR]

Although the direct involvement of nitrogen and phosphorus has been shown, eutrophication remains poorly managed to this day. The excessive growth of some opportunist seaweeds is the consequence in coastal ecosystems close to agricultural or strongly urbanized and industrialized zones. In Brittany, a leading tourist region of France, green tides set down on the beaches big quantities of Ulva, of which some 100,000 m3 are harvested annually, with significant ecological and economic consequences. In Florida, although the macroalgae (notably Codium) drift about with the currents, they are of sufficient mass and spread over such areal extent to inhibit penetration of sunlight through the water column to the coral reef surface. They strand also on the beaches. Stabilization of algae by composting and methanization of hydrolyzed and pressed algae juice are two methods which have been studied in Brittany and can be used to enhance the value of the harvested seaweed, depending on local conditions and on evolution of needs in energy, basic materials or organic products. But the parallel made here between two very different ecosystems, both disturbed, leads above all to the question of what course to follow now to avoid a worldwide disaster. Bien que le rôle de l'azote et du phosphore dans les processus d'eutrophication ait été montré, celle-ci reste mal contrôlée à ce jour. La croissance excessive d'algues opportunistes en est la conséquence dans des écosystèmes côtiers proches de zones agricoles ou fortement urbanisées et industrialisées. En Bretagne, région touristique de France, des marées vertes déversent sur les plages de grandes quantités d'ulves, dont environ 100,000 m3 sont récoltés annuellement, avec d'importantes conséquences écologiques et économiques. En Floride, bien que les macroalgues (notamment Codium) dérivent avec les courants, elles sont en masse suffisante et suffisamment réparties pour empêcher la pénétration de la lumière dans la colonne d'eau jusqu'au récif de corail. Elles s'échouent également sur les plages. La stabilisation par compostage et la méthanisation de jus d'algues hydrolysées et pressées sont deux méthodes qui ont été étudiées en Bretagne afin de valoriser l'algue récoltée, en fonction des conditions locales et de l'évolution des besoins en énergie, matières premières ou produits organiques. Mais le parallèle fait ici entre deux écosystèmes très différents, tous deux perturbés, mène surtout à se demander quelle voie suivre maintenant pour éviter un désastre mondial. [ABSTRACT FROM AUTHOR]