Temperature and Inoculum Origin Influence the Performance of Ex-Situ Biological Hydrogen Methanation.

The conversion of H into methane can be carried out by microorganisms in a process so-called biomethanation. In ex-situ biomethanation H and CO gas are exogenous to the system. One of the main limitations of the biomethanation process is the low gas-liquid transfer rate and solubility of H which are strongly influenced by the temperature.

Biomethanation processes: new insights on the effect of a high H partial pressure on microbial communities.

Background: Biomethanation is a promising solution to upgrade the CH content in biogas. This process consists in the injection of H into an anaerobic digester, using the capacity of indigenous hydrogenotrophic methanogens for converting the injected H and the CO generated from the anaerobic digestion process into CH. However, the injection of H could cause process disturbances by impacting the microbial communities of the anaerobic digester.

Soft Microwave Pretreatment to Extract -Hydroxycinnamic Acids from Grass Stalks.

The aim of this article is to provide an analysis of microwave effects on ferulic and coumaric acids (FA and CA, respectively) extraction from grass biomass (corn stalks and miscanthus). Microwave pretreatment using various solvents was first compared to conventional heating on corn stalks. Then, microwave operational conditions were extended in terms of incident power and treatment duration.

Methanosarcina plays a main role during methanogenesis of high-solids food waste and cardboard.

Anaerobic digestion of food waste is a complex process often hindered by high concentrations of volatile fatty acids and ammonia. Methanogenic archaea are more sensitive to these inhibitors than bacteria and thus the structure of their community is critical to avoid reactor acidification. In this study, the performances of three different inocula were compared using batch digestion tests of food waste and cardboard mixtures.

Addition of granular activated carbon and trace elements to favor volatile fatty acid consumption during anaerobic digestion of food waste.

The effect of supplementing granular activated carbon and trace elements on the anaerobic digestion performance of consecutive batch reactors treating food waste was investigated. The results from the first batch suggest that addition of activated carbon favored biomass acclimation, improving acetic acid consumption and enhancing methane production. Adding trace elements allowed a faster consumption of propionic acid.

Accumulation of propionic acid during consecutive batch anaerobic digestion of commercial food waste.

The objective of this study was to test three different alternatives to mitigate the destabilizing effect of accumulation of ammonia and volatile fatty acids during food waste anaerobic digestion. The three options tested (low temperature, co-digestion with paper waste and trace elements addition) were compared using consecutive batch reactors. Although methane was produced efficiently (∼500ml CHgVS; 16l CHlreactor), the concentrations of propionic acid increased gradually (up to 21.

Kinetic study of dry anaerobic co-digestion of food waste and cardboard for methane production.

Dry anaerobic digestion is a promising option for food waste treatment and valorization. However, accumulation of ammonia and volatile fatty acids often occurs, leading to inefficient processes and digestion failure. Co-digestion with cardboard may be a solution to overcome this problem.

Cardboard proportions and total solids contents as driving factors in dry co-fermentation of food waste.

This study evaluated the influence of the co-substrate proportions (0-60% of cardboard in dry basis) and the initial total solid contents (20-40%) on the batch fermentation performance. Maximum hydrogen yields were obtained when mono-fermenting food waste at high solids contents (89mlH·gVS). The hydrogen yields were lower when increasing the proportions of cardboard.

Dry anaerobic digestion of food waste and cardboard at different substrate loads, solid contents and co-digestion proportions.

The increasing food waste production calls for developing efficient technologies for its treatment. Anaerobic processes provide an effective waste valorization. The influence of the initial substrate load on the performance of batch dry anaerobic co-digestion reactors treating food waste and cardboard was investigated.

Total solid content drives hydrogen production through microbial selection during thermophilic fermentation.

In this study, the effect of total solid content (TS) on thermophilic hydrogen production from wheat straw was investigated. Six TS contents ranging from wet to dry conditions (10-34%TS) were tested in batch tests. A decrease of H₂ yields was observed and three statistical groups were distinguished according to the TS content: wet conditions (10% and 14%TS) with 15.

Single-phase and two-phase anaerobic digestion of fruit and vegetable waste: comparison of start-up, reactor stability and process performance.

Single-phase and two-phase digestion of fruit and vegetable waste were studied to compare reactor start-up, reactor stability and performance (methane yield, volatile solids reduction and energy yield). The single-phase reactor (SPR) was a conventional reactor operated at a low loading rate (maximum of 3.5 kgVS/m3 d), while the two-phase system consisted of an acidification reactor (TPAR) and a methanogenic reactor (TPMR).

Total solids content: a key parameter of metabolic pathways in dry anaerobic digestion.

Background: In solid-state anaerobic digestion (AD) bioprocesses, hydrolytic and acidogenic microbial metabolisms have not yet been clarified. Since these stages are particularly important for the establishment of the biological reaction, better knowledge could optimize the process performances by process parameters adjustment.

Results: This study demonstrated the effect of total solids (TS) content on microbial fermentation of wheat straw with six different TS contents ranging from wet to dry conditions (10 to 33% TS).

Microbial community signature of high-solid content methanogenic ecosystems.

In this study, changes in bacterial and archaeal communities involved in anaerobic digestion processes operated with high solid contents were investigated. Batch tests were performed within a range of total solids (TS) of 10-35%. Between 10% and 25% TS, high methanogenic activity was observed and no overall specific structure of active bacterial communities was found.

Anaerobic co-digestion of solid waste: Effect of increasing organic loading rates and characterization of the solubilised organic matter.

The impact of stepwise increase in OLR (up to 7.5kgVS/m(3)d) on methane production, reactor performance and solubilised organic matter production in a high-loading reactor were investigated. A reference reactor operated at low OLR (<2.

Chemical and toxicological assessment of a full-scale biosolid compost.

The impact of a full-scale biosolid composting plant on the fate of a broad range of priority organic pollutants was investigated. Chemical analysis was performed at different steps of the process during two seasons. Simultaneously, the toxicological quality was assessed using estrogen α-, dioxin-, and pregnane X-receptor reporter cell lines.

Total solids content drives high solid anaerobic digestion via mass transfer limitation.

The role of the total solids (TS) content on anaerobic digestion was investigated in batch reactors. A range of TS contents from 10% to 35% was evaluated, four replicates were performed. The total methane production slightly decreased with TS concentrations increasing from 10% to 25% TS.

Control of start-up and operation of anaerobic biofilm reactors: an overview of 15 years of research.

Anaerobic biofilm reactors have to be operated in a way that optimizes on one hand the start-up period by a quick growth of an active biofilm, on the other hand the regular operation by an active control of the biofilm to avoid diffusion limitations and clogging. This article is an overview of the research carried out at INRA-LBE for the last 15 years. The start-up of anaerobic biofilm reactors may be considerably shortened by applying a short inoculation period (i.

Occurrence of estrogens in sewage sludge and their fate during plant-scale anaerobic digestion.

Estrogens, which contribute greatly to the endocrine-disrupting activity in sewage, are partially sorbed onto particulate matter during sewage treatment. We thus investigated the occurrence of estrogens in different kinds of sludge and throughout a plant-scale anaerobic digestion process. The analytical method was first validated when sorption interaction between spiked estrogens and sludge could occur.

Selective microbial aerosolization in biogas demonstrated by quantitative PCR.

Aerosolization of Bacteria, Archaea, Synergistes, Staphylococcus spp. and Propionibacterium acnes was investigated in situ with quantitative real-time PCR of DNA isolated from sludge and biogases of anaerobic digesters. The data revealed that in biogas, Staphylococcus spp.

Molecular and kinetic characterization of mixed cultures degrading natural and synthetic estrogens.

The biodegradation of estradiol (E2), estrone (E1), and ethinylestradiol (EE2) was investigated using mixed bacterial cultures enriched from activated sludge. Enrichments were carried out on E2 or EE2 in batch conditions with acetonitrile as additional carbon source. Degradation experiments were performed both using hormones as sole carbon source or with an additional source.

Diversity of bacteria and fungi in aerosols during screening in a green waste composting plant.

This article outlines a comprehensive analysis of the microbial diversity of aerosols produced during screening in a green waste composting plant using both culture and molecular techniques. Bacteria, thermophilic actinomycetes and fungi were quantified in the aerosols. The structure of the microbial community was examined using a fingerprint technique and DNA libraries.

Saponification of fatty slaughterhouse wastes for enhancing anaerobic biodegradability.

The thermochemical pretreatment by saponification of two kinds of fatty slaughterhouse waste--aeroflotation fats and flesh fats from animal carcasses--was studied in order to improve the waste's anaerobic degradation. The effect of an easily biodegradable compound, ethanol, on raw waste biodegradation was also examined. The aims of the study were to enhance the methanisation of fatty waste and also to show a link between biodegradability and bio-availability.

A comprehensive method for organic matter characterization in solid wastes in view of assessing their anaerobic biodegradability.

The calculation of the anaerobic biodegradability requires the knowledge of the COD of the organic waste considered. Unfortunately, standard COD measurements are not available for solid wastes. In addition, sample processing generally requires a drying step (for TS and VS assessment for instance).

Impact of initial biodegradability on sludge anaerobic digestion enhancement by thermal pretreatment.

Thermal treatments with temperature ranging from 60 to 210 degrees 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 degrees C.

Removal of polycyclic aromatic hydrocarbons (PAH) during anaerobic digestion with recirculation of ozonated digested sludge.

PAH are particularly monitored because of their carcinogenic properties and their ubiquity in the environment. Their presence in municipal sewage sludge is a major problem due to the environmental risks associated with the sludge spreading on agricultural soils. The objective of this work was to asses the removal of PAH naturally present in sludge by continuous anaerobic digestion with recirculation of ozonated sludge.