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National audience; Cette contribution présente les enjeux de l'écoconception à l'échelle des filières de valorisation des déchets au regard de trois approches : l'ingénierie inverse, l'évaluation environnementale et le diagnostic territorial.

International audience; Knowledge and mitigation of gazeous emission that can occur at differents steps of digestats post-processing and used (liquid/solid separation, drying, storage, pelletisation, spreading,…) result in a very important chalenge as well at the environmental point of view as economic. These gaseous emission could seriously influence : -The impact of anaerobic digestion sector on ammonia emission from agricultural activities, and enviromental associated impacts (air quality, acidification,…) -The impact of anaerobic digestion sector on climate change (N2O and CH4 emission) -The possibility of substitution of mineral fertilizer by the digestats (ammonia emission is one of the main sources of nitrogen loss on the sector) -The social acceptability of the sector (emission of odorous compounds) In a goal of optimization of the strategies of spreading, or to allow an export from production area, many strategies of post-processing of the digestats can be put in work. Steps of post-processing influence significantly digestat properties and emission behavior during management. The aim of this work is to evaluate the impact of these different strategies for 4 scenario including : one with no particular post-processing to manage a raw digestat, and 3 others with liquid/solid separation step, solid phase drying, and pelletization; the evaluation of impact include each time storage and land-spreading steps. Emissions concerned in this work are NH3, CH4, and N2O (only during storage), and odors (measured with dynamic olfactometry) Results allow to define post-processing strategies according with a goal of emission mitigation on the whole process ; According to the post-processing of digestats applied, we can define steps on which mitigation or reduction of emission should focus, in the aim of improving the enviromental balance.

International audience; Digested manure can generate high ammonia emissions during landspreading because of their high pH value and ammonium content. In addition, its landspreading can generate odour emissions, even if they are reduced comparing to raw manure (Orzi et al., 2010). Hence, ammonia and odour emissions have to be mitigated to optimize the environmental balance of anaerobic digestion. Post-treatments can strongly modify digested manure properties and contribute to emission mitigation. Nevertheless, to quantify the impact of post-treatments on ammonia and odors emissions associated to the landspreading step, most of the studies only consider emissions following landspreading without considering emissions during landspreading. The objective of this paper is to quantify ammonia and odour emissions during digested manure dispersion in comparison to those observed following landspreading. To this purpose, raw and post-treated digested manure were landspreaded in a hermetic experimental room with a real-scaled spreader. Ammonia and odor emissions during manure landspreading were accumulated into the experimental room. Emissions following landspreading were assessed using wind tunnel systems (Van Der Weerden et al., 1996). Ammonia emissions were quantified using an infrared multi-gas monitor (INNOVA 1412) combined with acid traps. Odour emissions were quantified using olfactory measurements (dynamic dilution olfactometer-ONOSE-8). Concerning ammonia, results highlight that emissions during digested manure landspreading are between 0.11 and 0.95% of total ammonium content of the manure. Hence, these emissions can be considered as non-significant comparing to ammonia emissions following landspreading. That kind of result is also observed for raw manure. Indeed, for cow manure and poultry droppings, ammonia emissions during landspreading reach 4.86% and 0.55% of total ammonium content, respectively. Concerning odour emissions, results highlight that emissions during digested manure landspreading are significant and, depending on the digested manure considered, can be superior to emissions following landspreading. For example, for dried digested manure, odour emissions during landspreading reach 819 OU.kg-1. However, odour emissions following landspreading reach only 53 OU.kg-1.h-1. In addition, depending on the considered digested manure, impact of post-treatments on odour emissions during and following landspreading can be different. For example, digested manure drying leads to an increase of odour emissions during landspreading, and a decrease of odour emissions following landspreading. To conclude, to estimate ammonia emission factors for landspreading, emissions during landspreading can be considered as non-significant. Only emissions following landspreading can be considered. However, concerning odour emissions, emissions during and following landspreading have to be considered together.

International audience; Substitution des engrais minéraux, émissions de gaz à effets de serre et d’ammoniac, stockage du carbone dans les sols, excédents d’azote sur un territoire,… autant de problématiques environnementales qui dépassent la production de biogaz et auxquelles les projets de méthanisation doivent pourtant répondre. Cette conférence propose de faire un état des lieux des connaissances actuelles sur l’impact de la méthanisation, en tant que filière, sur ces principales problématiques environnementales. Les leviers d’actions lors de la construction d’un projet ainsi que les questions encore en suspens seront également discutées.

International audience; With the recent development of anaerobic digestion plants in France, farmers should manage new organic products often more concentrated in N or P fertilizer. In the same time they have to decrease the use of inorganic fertilizers in order to minimize environmental damages. In agriculture, organic fertilizer are spread using big band robust spreader, because of the product specificities, variabilities, etc. Intrinsic fertilizer value is more and more considerate nowadays and application quality in the field has to be always better, as well to maximize agronomical return as to minimize environmental impacts. This new method, named IMOB (Irstea Method or Mobile Organic Bench) has been developed in order to test and evaluate solid organic matter spreading on soil, particularly for solid fraction of digestate applications. Objective is to evaluate land-spreading performances regarding spreader and organic fertilizer characteristics, in order to improve land-spreading quality. This test provides the volumetric three dimensional spread pattern and its correspondence with the mass (transverse distribution represents the mass of organic matter distributed perpendicularly to the travel direction while longitudinal distribution represents evolution of the rate along the total spreading time). Also criteria which are defined in the European standard EN 13080 can be estimated using this method: optimum working widths, transverse variation coefficient, application rate, flow characteristics, stretch within the tolerance zone and longitudinal variation coefficient. 3D spread pattern distribution and land-spreading flow are measured during the same spreader unloading. A globally plan and horizontal area is required in order to install mobile axle weighing system which supports the spreader and the tractor. In a relatively short time (around one hour) and without complicated and fastidious works, land-spreading measurements are performed. Innovation in the measurement is the use of a 3D laser scanner (FARO® Laser scanner Focus 3D) which allows measuring the topography of the global fertilizer mass distributed during the unloading. This land-spreading topography is obtained computing the difference between the laser measurement after the unloading and the one before unloading, the spreader being fixed during the test, weighted continuously by the static platforms to register the mass flow. Using the land-spreading obtained map, transversal distribution is calculated adding fertilizer densities column by column in the travel direction, as required in the European standard EN 13080. The laser telemeter is handly positioned because of its small size and weight (around 5kg), and the precision of each of the measured distances is less than 2mm. Samples of obtained spread patterns have been compared using the specific Irstea test bench 'CEMOB' which validated the method. For these test, material used during land-spreading was a solid fraction obtained from a mechanical separation of digestate. Results give information about spreader / matter interactions and allow improving land-spreading efficiency. Using correctly user machine instructions and obtained test data, high quality land-spreading can be obtained. Many working width variation coefficients are computed in order to define the optimal working width regarding different settings. In a small time, without complicated and costly devices, the global picture of the obtained land-spreading can be measured. It has been showed to be very closed to the 3D spread pattern measured using CEMOB device, even if it represents the distribution of the total amount for the unloading. The volumetric measurement which is performed by the scanner, crossed with the unloading value measured using static platforms, provides a consistent measurement of the land-spreading performance. In the future, this new test could be an alternative to perform improvement test easily and everywhere. Manufacturer could use it in order to improve spreader design and construction, and so minimise environmental damages and optimise fertilization. For existing spreaders, this method could be used in order to identify correct settings and land-spreading requirements for different product to be spread. User’s manual should be more precise by this way. This new test method should be proceeded to encourage farmers and spreader users, to realize better spreading.

International audience; During the last decades, European institution establishes regulations which aim at protecting the environment from the adverse effects of the collection, treatment and discharge of waste water imposing wastewater treatment plants (WWTP) to release a good water quality in the environment. The constant diminution of the organic pollution of wastewater due to higher performance of water treatment through biological treatments leads to an increase in sludge production. The treatment processes used to concentrate and stabilize the sludge are of great importance as the sewage sludge treatment line can constitute 25 % to 72 % of total emissions of the WWTP [1]. Our study aims to present the sensitivity of Life Cycle Assessment environmental impacts results of a sewage sludge treatment line combining primary and secondary sludge thickening, anaerobic digestion, press filter dewatering, sludge storage and land spreading as final disposal (reference scenario) according to several types of parameters. Life Cycle Assessment of the reference scenario was conducting using GaBi software and environmental impacts results with the Recipe method. A sensitivity analysis was then conducted by changing reference value with a range of value for four types of parameters relevant of the treatment process performances. The studied parameters are: (a) Primary and secondary sludge composition (N, Volatile matter, P, K, Mg, Ca), (b) Anaerobic digestion performances (Volatile matter abatement, N mineralization rate, P solubilization rate, biogas composition, Hydraulic Retention Time) (c) Dewatering performances (dewatered sludge dry content based on literature value, dewatered sludge dry content based on pressure, cake thickness, filtration duration, N, P and K capture rate, polymer and FeCl3 dosage) (d) Primary and secondary thickening performances (thickened sludge dry content, N, P and K capture rate) By analyzing the sensitivity of each environmental impact (global warming, acidification, eutrophication, human toxicity…) according to each studied parameter, we identified several hotspots that research should be focused on to improve the efficiency of treatment performances and so the environmental impact of the whole sewage sludge treatment line.

National audience; Méthanisation et enjeux territoriaux de développement dans le Grand Ouest.

National audience; néant; néant

International audience; During this study, nuclear magnetic resonance (NMR) was compared to the soxhlet extraction for determination of the lipid content of organic waste usually used in anaerobic digestion. Thus, 48 different wastes were analyzed using both methods and three replicates were performed for each. The correlation between Soxhlet methods and NMR was 0.90 and the regression slope was equal to 1.02. A better precision was obtained for NMR method with a coefficient of variation of 5%, while for the Soxhlet method, this coefficient is 14%. In contrast, the NMR method gave overall values below the reference method soxhlet. This difference can be explained by the advanced state of hydrolysis of fats where a large amount of volatile fatty acids, saturated molecules small chains linked would be present, and the degree of saturation of fatty acids long chains. NMR method seems suited to the analysis of lipids with better repetition and has the advantage of not using any solvent, be fast and non-destructive. However, the determination of some lipid matrices seems undervalued using the conditions established by the NMR protocol. Finally, this study also established data on lipid content of organic waste.

Recovering (bio) Ressources for the World, Santiago de Compostella, ESP, 25-/06/2013 - 28/06/2013; International audience; To design co-digestion systems, most of the designers consider that the methane production will be equal to 80% of the weighted sum of the biochemichal methanogenic potentials (BMPs) of substrates. However, interactions between substrates can influence the methane production and are generally not taken into account. The objectives of this paper are: (1) the identification of the effect of interactions between substrates on the methane production of co-digestion systems and (2) the identification of the control factors of these phenomena. For this purpose, BMP tests were processed with 30 binary mixtures of substrates and the obtained results were compared with the theoretical BMP values of each mixture obtained by the weighted sum of the BMP value of each substrate in monodigestion. No antagonism was identified. However, synergies were identified for co-digestion tests including porcine slurry and bovine slurry. A statistic analysis highlights that these interaction phenomena are correlated with the biochemical characteristics of co-substrates which can induce enzymatic activation phenomena.

International audience; This study aims to evaluate the impact of pretreatment on the anaerobic digestion of wheat straw and other lignocellulosic materials. For that, an original procedure named “Anaerobic Respirometry” is used as a tool to monitor the Methane Production Rate (MPR) of treated and untreated materials, allowing determining the impact of pretreatment in terms of CH4 production and degradation kinetics. Results from various grinding technologies, namely impacts mill, knife mill, air-jet mill, ball mill illustrate this procedure. The MPR experimental curves obtained for pretreated substrates show two distinct peaks in the methane production rate. This can result from an accumulation of acetate which is then consumed and gives rise to the second peak. A second hypothesis can also involve a phenomenon of bacteria colonization on the cellulose delaying methane production. Although this double peak complicated the results interpretation, CH4 production over the 10 days period was determined from the MPR in order to evaluate the impact of the mechanical pretreatment on the anaerobic digestion efficiency. The results demonstrate an increase up to 44% in CH4 production from 122 for the knife mill sample up to 175 NLCH4/kgVS for samples grinded by ball mill.

International audience; Catch crops cultivated in autumn or over winter can be used as feedstock for agricultural biogas production. Brassicaceae crops are good candidates for this specific use due to their agronomic values in intercropping conditions. However their high content in glucosinolate may conduct to sulphur release in the digesters and induce anaerobic digestion troubles or biogas pollution with hydrogen sulphide. In this study, Brassicaceae crops were used as co-substrate with pig slurry in anaerobic digesters. Their anaerobic biodegradability was close to other lignocellulosic biomass with a large fraction of slowly biodegradable organic matter content. The sulphur and glucosinolates contents in plants did not inhibit the overall anaerobic process neither severely impacted hydrogen sulphide concentration in the biogas.

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National audience; Depuis de nombreuses années, la production de déchets organiques est en augmentation constante en raison de pratiques d’élevage, d’industrialisation, de procédés de traitement et collecte des déchets. Pour répondre aux enjeux environnementaux de la gestion des déchets, des procédés biologiques de traitement et de valorisation sont mis en oeuvre, notamment la digestion anaérobie (méthanisation). Cependant, l’ajout de graisse peut entraîner, dans certains cas, des inhibitions dans le procédé de digestion [1]. La bibliographie décrit de nombreuses méthodes concernant la détermination des lipides. La plus connue et utilisée consiste, à l’aide d’un soxhlet, à extraire à chaud par solubilisation des composants à l’aide d’un solvant [2]. Une autre méthode de mesure des lipides totaux par résonance magnétique RMN a été étudiée sur des muscles de poisson séché et a donné une bonne corrélation [3]. Dans le domaine des déchets, la RMN a déjà été utilisée pour la caractérisation de la matière organique, notamment les acides humiques, et les transformations de cette matière lors du compostage [4], mais aucune référence ne semble disponible sur l’analyse des lipides. Au cours de cette étude, la méthode RMN a été comparée à la méthode soxhlet sur des déchets organiques susceptibles d’être utilisés en méthanisation. Ainsi, 48 déchets d’origine différente ont été analysés avec les 2 méthodes Trois répétitions ont été effectuées pour chacun des substrats. La corrélation entre les méthodes soxhlet et RMN a été de 0.90 et la pente de régression de 1.02. Une meilleure précision de la méthode RMN a été calculée avec un coefficient de variation de 5% alors que pour la méthode sohxlet il est de 14%. En revanche, la méthode RMN a donné globalement des valeurs inférieures à la méthode de référence soxhlet : la sous-estimation peut être liée à l’extraction non sélective au soxhlet, à une température de chauffage insuffisante liée à l’état amorphe des lipides ou au degré de saturation des matières grasses dans les différents produits pour la RMN. L’état d’hydrolyse des graisses lié à leur stockage et le degré de saturation des acides gras à longues chaînes pourrait influencer la mesure des lipides par RMN. La méthode RMN semble adaptée à l’analyse des graisses avec une meilleure répétition et présente l’avantage de n’utiliser aucun solvant, d’être rapide et non destructrice malgré une sous-évaluation par le protocole RMN actuel. Enfin, cette étude a également permis d’établir des données lipidiques sur des déchets organiques et suppléer la méthode d’analyse soxhlet de référence.

Pour assurer l’équilibre économique des unités de méthanisation, l’ajout de co-substrats est en général nécessaire. Pour les choisir, deux questions se posent aux porteurs de projets : quelles sont les caractéristiques des co-substrats disponibles et quel est l’impact des mélanges sur le fonctionnement du digesteur. Le présent article se propose de répondre à ces questions sur la base des résultats du projet Biodecol2.

International audience; Catch crops cultivated in autumn or over winter can be used as feedstock for agricultural biogas production. Brassicaceae crops are good candidates for this specific use due to their agronomic values in intercropping conditions. However their high content in glucosinolate may conduct to sulphur release in the digesters and induce anaerobic digestion troubles or biogas pollution with hydrogen sulphide. In this study, Brassicaceae crops were used as co-substrate with pig slurry in anaerobic digesters. Their anaerobic biodegradability was close to other lignocellulosic biomass with a large fraction of slowly biodegradable organic matter content. The sulphur and glucosinolates contents in plants did not inhibit the overall anaerobic process neither severely impacted hydrogen sulphide concentration in the biogas.

Les travaux concernant la caractérisation physique des digestats bruts ont abordé trois aspects : (i) une analyse rhéologique des digestats se focalisant sur leurs propriétés de structure et d’écoulement ainsi que sur leurs points communs et spécificités, (ii) une analyse à dires d’experts de leur aptitude à l’épandage et (iii) l’étude de leur déshydratabilité (aptitude à la séparation de phase) via des mesures de cinétique de déshydratation en cellule de filtration compression et de siccité limite, tout en portant une attention particulière à l’étape de floculation. Du point de vue rhéologique, les digestats considérés dans le projet peuvent tous être définis comme des fluides non-Newtoniens, certains avec un seuil d’écoulement (c'est-à-dire qu’ils présentent des caractéristiques solides aux faibles contraintes et des caractéristiques liquides aux contraintes les plus élevées), d’autres sans seuil (ils ne présentent que des caractéristiques liquides, quelle que soit la contrainte appliquée). L’existence ou non du seuil de contrainte est liée à la fois à la concentration et à la composition des matières sèches : les deux paramètres clés permettant de distinguer le comportement rhéologique des digestats sont la concentration en matières sèches (MS) et le rapport MO/MS (où MO indique la teneur en matière organique). Ainsi, deux digestats de même MS et MO/MS ont le même comportement rhéologique. En termes d’épandabilité, les digestats les plus fluides (sans seuil de contrainte) peuvent, à dires d’expert, être épandus avec une tonne à lisier équipée de pendillards. Les autres digestats, à l’état brut, seront plus difficiles à épandre et une séparation de phase est préconisée. Concernant la déshydratation mécanique, une étape de floculation s’est avérée nécessaire en amont de la séparation de phase pour que des essais de laboratoires soient faisables : en effet, les digestats sont très chargés en matières colloïdales et la déshydratation en système de filtration sur toile ne donne des rendements exploitables que si un conditionnement chimique est utilisé pour favoriser la séparation eau/matières solides. Les résultats montrent également que la dose de polymère nécessaire pour une floculation optimale (si elle est réalisable) est 2 à 3 fois plus élevée que celle que l’on peut observer classiquement sur les boues résiduaires, ce qui est notamment dû à la forte salinité des digestats. On notera que les performances en déshydratation des digestats sont très variables selon la filière de digestion et les substrats digérés. Néanmoins, un lien a pu être établi entre la siccité limite des digestats et le ratio MO/MS des digestats considérés.

International audience; Dewatering properties of various digestates were investigated with filtration-compression tests. Results show an important variability of the cake siccity, optimal polymer dose and filtrate concentrations. These observed differences can be correlated to analytic paramaters, without considering the origin of the digestates.

International audience; Agriculture substantially contributes to anthropogenic emissions of both N2O and CH4 as well as ammonia (NH3). As signatories to international conventions, EU Member States must reduce their emissions. Moreover, the European Council (December 12, 2008) defined the energy-climate package and implemented a target called "3 X 20". The aim of this target is to reduce GHG emissions by 20% by 2020 compared to 1990 levels. It also aims to bring to a 20% share of renewable energy in the final consumption and to increase energetic efficiency by 20%. In response to these commitments, anaerobic digestion of livestock wastes is expected to expand in France in the coming years. The objectives of economic performance lead to a particular interest in centralized treatment plants involving other wastes, specifically wastes with high potential for energy production (agri-food waste, crop residues, etc.) which may be collected over long distances. However, such development is complex and requires the awareness of social and technical constraints (heat recovery, access to bio-resources...) as well as adhering to legal restrictions in the concerned areas. In this context of potential development of collective biogas plants in France, the use of Geographic Information Systems (GIS) in order to georeference the bio-resources and then to locate the optimal sites appears very interesting and useful tools. Such investigations have been carried out on both national and regional scales (Batzias, 2005; Dagnall, 2010) but need to be adapted for local diagnosis. For this purpose, a research project is devoted to the development of such methodologies, then applied in the “Pays de Fougères”, a 1000 km² wide rural area located in the north-eastern Brittany in France. Firstly, a bio-resource mapping is drawn by applying a calculation method specific for each substrate. A derived layer, the energy potential grid (EPG), is calculated as the sum of the energy potential at any point in the area (100 m resolution per pixel) considering for each substrate a maximum distance proportional to the energetic potential of the substrate. Next, sensitive areas (wetlands, distances from housing…) are identified as areas where the development of biogas plants is restricted, resulting in a constraint map (CM). A final suitability map is constructed by combining the CM and the EPG, synthesized in the form of a raster GIS file. To go further on this issue, the network analysis capability of GIS is used, in order to take into account the actual transport route and competitive access to bio-resources. As a result, it allows refining the diagnosis of candidate sites. This study initiates the construction of a GIS model to determine optimal sites for collective biogas plants. The specificity of the approach is that methodologies are implemented to reach a very fine level of spatialization. The precise geolocation of farms is successfully obtained through the analysis of aerial photographs and Landsat imagery is used to help the identification of crop residues. However, some improvements could be implemented in the future, such as assigning a weight factor to the bio-resources reflecting their relative importance (liquid/solid form, no additional N content in the digestate, etc.). Although this mapping provides a basis for discussion in the context of decision support, it does not allow itself to make a choice on a future location, particularly since in the investigated area, the availability of bio-resources is not a major barrier (range from 6800 to 9300 ton of oil equivalent (toe)/year). Complementary parameters could be considered like social acceptance and environmental concerns generated by such a collective biogas plant. To explore this aspect in depth, the question of local impacts like eutrophication should be taken into consideration. Thus, beyond this GIS-based model, in order to test different scenarios for the development of collective biogas plants, a Life Cycle Assessment (LCA) is realised, assessing the environmental impacts of three scenarios as described in the paper of Aissani (2012). Future work will be to link more closely the GIS in LCA studies through the integration of spatial data and the spatial differentiation of local environmental impacts, the ultimate goal being to build a generic model for maximizing energy recovery from bio-resources in conjunction with a low environmental impact.

[Departement_IRSTEA]Ecotechnologies [Departement_IRSTEA]Territoires [Departement_IRSTEA]Eaux [TR1_IRSTEA]SEDYVIN [Axe_IRSTEA]Co TED-SOWASTE et TED-EPURE [TR2_IRSTEA]QUASARE [TR2_IRSTEA]SPEE [TR2_IRSTEA]TED [TR2_IRSTEA]INSPIRE [TR2_IRSTEA]DTAM [TR2_IRSTEA]MOTIVE [TR2_IRSTEA]SYNERGIE; Une énergie facilement disponible et bon marché a permis l'amélioration de notre qualité de vie au cours des deux derniers siècles. Cette disponibilité constitue un pilier fondateur de notre société technologique actuelle. Avec la croissance démographique mondiale qui portera à 9 milliards le nombre d'habitants sur la planète en 2050, comment faire face à l’augmentation mondiale des besoins en énergie alors que, dans le même temps, les énergies fossiles s'épuisent et que leurs usages intensifs augmentent la quantité de gaz à effet de serre dans l'atmosphère responsable en partie du réchauffement climatique ? Les énergies renouvelables sont un complément indispensable, une alternative crédible, y compris au plan économique. Ne peuvent-elles permettre au moins une transition énergétique ? Il faut pour cela accentuer les efforts de recherche.

Face à l'épuisement programmé de la ressource énergétique fossile et au réchauffement climatique, les énergies renouvelables suscitent un intérêt croissant. Parmi ces énergies renouvelables, le biogaz issu de la méthanisation agricole présente de nombreux intérêts environnementaux, économiques et sociaux.

National audience; Vers une gestion territoriale des déchets et effluents organiques : focus sur la méthanisation des boues de STEP.

International audience; The aim of this article is to investigate the effect of the Hydraulic Retention Time (HRT) on the anaerobic CSTR digester performance in term of methane production using modelling combined with a specific characterization of wastes. Hence, a recently developed methodology (“anaerobic respirometry”) has been applied to define input state variable set for the “Anaerobic Digestion Model n°1” (ADM1) adapted to each substrate including also hydrolysis rates. Then, ADM1 was used to simulate CSTRs with different HRT for each substrate. The results obtained for 12 common organic wastes from agro-industries (slaughterhouses and meat industry) are significantly different in function of the considered substrates. As an example, an HRT of 7 days is sufficient to reach 80% of the maximal methane production for bovine blood whereas HRT values of 32 and 78 days are required for waste activated sludge and rumen content, respectively, to reach the same yield. These results highlight the interest in the adaptation of the reactor design according to the composition of the reactor feed.

International audience; Anaerobic digestion of sludge from wastewater treatment is largely applied in France for the plants with an important capacity (> 50 000 eq. hab.) but remains little used for the smaller plants. Indeed, such a process is generally not interesting economically for the smaller plants compared to other sludge treatment techniques. However, the advantages of anaerobic digestion of sludge are well-know: production of renewable and local energy, reduction of greenhouse gas emissions, odour abatement and sludge reduction. In order to promote anaerobic digestion of sludge even for the small wastewater treatment plants, one of the possibilities for increase the rentability of the process is to add co-substrates available locally with the sludge in order to increase methane production. Such an approach was studied considering the Mordelles town (about 7000 hab.). Mordelles is located close to a larger city (Rennes, France) and is equipped with an activated sludge wastewater treatment plants for about 15000 eq. hab. So, activated sludge from the wastewater treatment plants and various co-substrates available locally were characterized for their ability to be anaerobically co-digested. Subsequently, co-digestion experiments were performed with activated sludge and lipid-rich waste from meat industry using batch and continuous experiments. Additionally to the specific results obtained, this work shows the difficulty to extrapolate from the results obtained in batch reactor to the prediction of continuous process.

This study aims to investigate the feasibility of using seaweed stranded on the beaches as a co‐substrate in the anaerobic digestion of pig slurry. The biochemical methane potential of Ulva sp. was measured and tests for co‐digestion with pig slurry were carried out in a pilot laboratory project. The methanogenic potential of this seaweed was low compared to other co‐substrates potentially available for use by farmers: 148 Nm3CH4.t‐1 volatile solids or 19 Nm3 CH4.t‐1 of crude product. Used as a co‐substrate, it did not appear their use caused any notable disruption in the process of digestion. The amount of hydrogen sulphide found in a biogas is an important consideration. At equilibrium, the biogas produced had a content of 3.5% H2S for a substrate mixture of pig manure / Ulva sp. (48/52%), making it unsuitable for energy recovery without treatment. As a comparison, the content of biogas during digestion of pig manure alone was around 0.2%. The high concentrations of dissolved sulphide in the digesta would be problematic for its agronomic use because the dissolved sulphides would be converted to hydrogen sulphide gas during land application (spreading). Lastly, this study showed that green seaweed was rich in organic nitrogen, which was partially mineralised in ammonium, and this would impact the land application (spreading) plan implemented by the farmer., Cette étude avait pour objectifs principaux d'étudier la faisabilité d'utiliser les ulves échouées sur les plages comme co-substrat dans les unités de méthanisation agricoles. Le potentiel méthanogène maximal des ulves a été mesuré et des essais de co-digestion avec du lisier de porcs ont été réalisés sur des pilotes de laboratoire. Le potentiel méthanogène des ulves est faible comparativement à d'autres co-substrats utilisables par la filière : 148 NlCH4.kg-1de matières volatiles, soit 19 NlCH4.kg.-1 de produit brut. De plus, les algues d'échouage ont une teneur en matières minérales importantes ce qui limitent les apports dans les réacteurs infiniment mélangés. Leur utilisation en tant que co-substrat ne semble pas occasionner de perturbations notoires sur le procédé, aucune inhibition n'a pue être mise en évidence. La quantité d'hydrogène sulfuré retrouvé dans le biogaz est très importante. Ainsi, _a l'équilibre des réacteurs, le biogaz produit présentait une teneur de 3.5% d'H2S pour un mélange lisier de porc/ulves (48/52%), le rendant inutilisable pour une valorisation énergétique sans traitement. A titre de comparaison, la teneur en biogaz lors de la digestion d'un lisier de porcs seul est de l'ordre de 0.2%. Les fortes concentrations de sulfures dissous dans les digestats sont problématiques quant à sa valorisation agronomique car ils sont transférés vers la phase gazeuse sous la forme d'hydrogène sulfuré au moment de l'épandage. Enfin cette étude met en évidence que les algues vertes sont riches en azote organique étant, pour partie, minéralisé sous sa forme ammoniacale impactant le plan d'épandage mis en place par l'exploitant agricole.

Waste water treatment plant sludge methanization has been used for many years to reduce their volume and to produce a biogas used as an energy source. Certain waste water treatment plants, treating effluent from tourist areas, must deal with significant seasonal fluctuations and hence the digesters are under-used for a significant part of the year. During these periods, it is therefore advantageous to be able to supplement digester feed with other substrates available locally. This article reports an example of digestion (laboratory scale) of waste water treatment plant sludge alongside fat waste from agribusinesses. It is interesting to note that the authors obtained very favourable performance levels in the presence of 40% of the fat (expressed in COD), without observing any significant inhibition in the presence of continuous fermentation methanization, and this with a residence time > 20 days without prior hydrolysis. This strategy, which incorporates co-substrates from a territorial source serves to improve the profitability of sludge methanization-related investments, not only in tourist areas, but also for small-scale waste water treatment plants (René Moletta, Moletta Méthanisation)., La méthanisation des boues de stations d'épuration est appliquée depuis de très nombreuses années pour diminuer leurs volumes et produire un biogaz qui est utilisé comme source d'énergie. Certaines stations d'épuration qui traitent des effluents issus de zones touristiques, doivent faire face à des fluctuations saisonnières importantes et donc les digesteurs sont souvent sous-alimentés une grande partie de l'année. Pendant ces périodes, il est donc particulièrement intéressant de chercher à compléter les alimentations du digesteur par d'autres substrats présents sur le territoire. Cet article rapporte un exemple de digestion de boues (au stade laboratoire) de stations d'épuration avec des graisses issues de flottation d'industries agroalimentaires. Il est intéressant de noter que les auteurs obtiennent des performances très intéressantes lors de la présence de 40 % des graisses (exprimée en DCO) sans observer d'inhibition notable lors de la mise en oeuvre de la méthanisation en fermentation continue, et ceci avec des temps de résidence > 20 jours et sans hydrolyse préalable. Cette stratégie qui incorpore des co-substrats issus d'un gisement territorial permet une meilleure rentabilisation des investissements liés à la méthanisation des boues non seulement dans des zones touristiques mais aussi pour les petites stations d'épuration (René Moletta, Moletta Méthanisation).

National audience; La méthanisation est un procédé actuellement en pleine expansion en France, notamment du fait de ses avantages environnementaux (réduction des émissions de gaz à effet de serre, production d’énergie renouvelable...). Ce procédé permet, sous l’action d’une succession de transformations microbiologiques complexes (hydrolyse, acidogenèse, acétogenèse et méthanogenèse), de minéraliser une partie de la matière organique en biogaz composé majoritairement de méthane (CH4) et de dioxide de carbone (CO2). Il est surtout mis en oeuvre en milieu liquide et dans des réacteurs themo-régulés à 35-40°C. En méthanisation agricole, les substrats issus de l’exploitation (effluents d’élevage, ensilage...) peuvent être supplémentés avec des déchets provenant de l’industrie agro-alimentaire ou des collectivités. Le biogaz produit est valorisé par des moteurs de cogénération permettant de produire de l’électricité et de la chaleur. Les modèles de développement de la méthanisation sont différents à travers l’Europe avec notamment : - le modèle Allemand développé à l’échelle de la ferme et basé sur la co-digestion d’effluents d’élevage et d’ensilage de maïs ; - le modèle Danois avec des unités centralisées permettant la co-digestion des effluents d’élevage, des déchets industriels et des collectivités. En France, la filière est encore en cours de développement mais les modèles semblent se situer à mi-chemin entre ces deux modèles emblématiques.

International audience; This paper presents two methods for the characterisation of input and calibration of an ADM1 model. The first, which is adapted for predictive studies, is named anaerobic respirometry and consists of a fractionation obtained by the numerical interpretation of methane production rate curves. These curves are obtained in batch experiments after a pulse of studied substrate in an anaerobic sludge. The second method is developed for full-scale application and complex substrates. The fractionation is initially based on balancing previously measured nitrogen, NH4-N and COD contents in influent, reactor and effluent, and combined with the online gas curve calibration procedure for further fine tuning of input fractionation and detection of kinetic parameters for calibration.

International audience; Modelling of anaerobic digestion is more and more used as a tool for process optimization or interpreting observed phenomena within research projects. The most used model is the Anaerobic Digestion Model n°1 (ADM1) but some other models are also available (either simpler or more complex). Whatever the model, one of the major key issue is the fractionation and characterisation of the influent. For substrates like activated sludge from wastewater treatment plants, detailed influent characterisation models have been developed. But, the other substrates more complex as slurries or those from co-digestion systems require a more detailed input characterisation. Chemical analysis can be used to give the basic splits required into proteins, fats, and carbohydrates. However, this does not provide biodegradability. Moreover, this required a conversion of analysis results into COD fractions often used as unit in models which lead to difficulty in term of mass balance. The aim of this approach is to develop a method for the characterisation of the influent of anaerobic digestion models. Named anaerobic respirometry, this method is based on the interpretation of the results (in term of methane production kinetics) of batch experiment performed at low substrate to biomass ratio. Already used specifically for the characterisation of sludges from wastewater treatment plants (Yasui et al., 2008), here this method was applied on more complex substrates (livestock effluents and common co-substrates). In this work, eight similar mesophilic batch reactors (1L of working volume) on which biogas and methane production rates are continuously measured were developed to perform anaerobic respirometry for substrate characterisation. After a study concerning the optimal conditions in term of substrate to biomass ratio and influence of the origin of biomass, substrates commonly used for anaerobic co-digestion were characterized including piggery slurry, wastes from slaughterhouse (fat, blood, sludges,), green waste, Three origin of sludge have been tested. The results show a low influence of the choice of the sludge it is not too much specialized for a specific substrate. Four substrate/biomass ratios have been evaluated between 0.05 and 0.35 gCODbiodegradable/gVSS with an optimum at 0.14 gCODbiodegradable/gVSS. From these results, substrates were characterized as presented on figure 1 allowing to determine a kinetic fractionation. On most of substrates a readily and a slowly biodegradable fraction of COD could be identified with the help of a simplified version of ADM1. These results could be useful for the modelling and optimization of anaerobic digestion processes.

Suite à la réévaluation des tarifs d'achat de l'électricité (Juillet 2006), à des éclaircissements réglementaires et à une vague de subventions à l'investissement, la filière méthanisation semble bel et bien lancée dans le secteur agricole. Cet article propose un première photographie du modèle de méthanisation agricole " à la française " en cours de développement.

Modelling of anaerobic digestion processes is a key aspect to study and optimize the digesters and related waste streams. However, some parameters have to be calibrated according to the substrates characteristics for an adequate representation of the biogas production and effluent characteristics. This article presents a calibration procedure for the IWA Anaerobic Digestion Model n°1. After a selection of the most sensitive parameters, a calibration of the selected parameters was performed using simultaneously the results issued from a digester working continuously and results from batch trials made with the sludge issued from the digester and specific substrates additions. This method was successfully applied for the modelling of a digester fed with piggery wastewater., La modélisation de la digestion anaérobie est de lus en plus utilisée pour l'étude et l'optimisation du fonctionnement des méthaniseurs et des flux de déchets qui y sont associés. Néanmoins, certains paramètres des modèles biologiques doivent être ajustés en fonction des caractéristiques de l'influent pour permettre une représentation satisfaisante de la production de biogaz et des caractéristiques de l'effluent. Ainsi, cet article présente une procédure de calage pour le modèle ADM1 (Anaerobic Digestion Model n°1). Après une sélection des paramètres les plus influents, un calage de ces derniers a été effectué. La procédure de calage repose sur l'utilisation simultanée des résultats d'un digesteur « continu » que l'on veut modéliser et des résultats de tests « batch » effectués avec des boues du digesteur « continu » et des ajouts de substrats spécifiques. Cette méthode a pu être appliquée avec succès pour modéliser un digesteur expérimental traitant du lisier de porc.

International audience; In order to deal with the environmental problems associated with the industrialization of the animal production and at the same time considering energy costs increasing, a piggery wastewater treatment process consisting of combined anaerobic digestion and biological nitrogen removal was developed. This contribution presents a modelling framework in order to optimize the whole process. Modified versions of the well-established ASM1 and ADM1 models have been used. The ADM1 was extended with biological denitrification and pH calculation and liquid gas-transfer were modified to take into account the effect of associated components. Finally, two interfaces (ADMtoASM and ASMtoADM) were built in order to combine both models. These interfaces set up the COD, nitrogen, alkalinity and charge fractionation between both models. However, for the mass continuity between both models, some hypotheses were considered and evaluated.