•BMP test displayed high gas potential generation capacity of MBT waste.•Strong inhibition effects were observed due to ammonia and VFA accumulation.•Waste water content was found as the key ...parameter limiting gas generation.•First order k-values were determined for different operating conditions.
In this work, the influence of different operating conditions on the biogas production from mechanically–biologically treated (MBT) wastes is investigated. Specifically, different lab-scale anaerobic tests varying the water content (26–43% w/w up to 75% w/w), the temperature (from 20 to 25°C up to 55°C) and the amount of inoculum have been performed on waste samples collected from a full-scale Italian MBT plant. For each test, the gas generation yield and, where applicable, the first-order gas generation rates were determined. Nearly all tests were characterised by a quite long lag-phase. This result was mainly ascribed to the inhibition effects resulting from the high concentrations of volatile fatty acids (VFAs) and ammonia detected in the different stages of the experiments. Furthermore, water content was found as one of the key factor limiting the anaerobic biological process. Indeed, the experimental results showed that when the moisture was lower than 32% w/w, the methanogenic microbial activity was completely inhibited. For the higher water content tested (75% w/w), high values of accumulated gas volume (up to 150Nl/kgTS) and a relatively short time period to deplete the MBT waste gas generation capacity were observed. At these test conditions, the effect of temperature became evident, leading to gas generation rates of 0.007d−1 at room temperature that increased to 0.03–0.05d−1 at 37°C and to 0.04–0.11d−1 at 55°C. Overall, the obtained results highlighted that the operative conditions can drastically affect the gas production from MBT wastes. This suggests that particular caution should be paid when using the results of lab-scale tests for the evaluation of long-term behaviour expected in the field where the boundary conditions change continuously and vary significantly depending on the climate, the landfill operative management strategies in place (e.g. leachate recirculation, waste disposal methods), the hydraulic characteristics of disposed waste, the presence and type of temporary and final cover systems.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Les contraintes techniques et économiques induites par la gestion des lixiviats de déchets ménagers et assimilés (LDMA) pourraient être minimisées en considérant le LDMA non plus comme un déchet mais ...comme un « co-produit » partiellement valorisable. Parmi la diversité des constituants des LDMA, la matière organique dissoute (MOD) présente 2 intérêts majeurs : une forte charge et des processus de transformations comparables à ceux de la matière organique naturelle (MON). Ce travail de thèse s’attache donc à extraire cette MOD des LDMA selon son caractère hydrophobe et à identifier des axes de valorisation. Seules les fractions de type hydrophobe (HPO*) et transphilique (TPH*), de par leurs caractéristiques et leur réactivité, ont été considérées dans cette étude et 2 voies de valorisation ont été testées : une valorisation énergétique et une valorisation matière par amendement sur un sol en déficit de carbone organique (Corg).La caractérisation des fractions de MOD anthropiques et leur comparaison à des fractions de MON a confirmé l’intérêt majeur de leur valorisation. En effet, elles sont (i) physiquement et chimiquement comparables à la MON, (ii) quantifiables à des concentrations jusqu’à plus de 1000 fois supérieures à la MON permettant ainsi un potentiel d’extraction conséquent en comparaison aux matrices environnementales telles que les eaux de surface, et (iii) plus facilement biodégradables que la MON, tout en ne présentant aucun caractère phytotoxique avéré.Un test BMP optimisé et adapté au LDMA a été développé via un plan d’expérience, puis utilisé pour mettre en évidence l’impact du caractère hydrophobe de la MOD du LDMA sur la digestion anaérobie, et notamment la production de méthane. Selon les résultats obtenus, les molécules organiques de type transphilique favorisent la production de biogaz. De plus, la fraction hydrophile, faiblement aromatique, diminue la teneur en méthane du biogaz, contrairement à la fraction hydrophobe.Enfin, l’amendement de fractions organiques extraites de LDMA présente un réel intérêt dans le cas d’un sol initialement pauvre en Corg. La fraction HPO* permet un apport de Corg plus important comparé à la fraction TPH*, tandis que les composés transphiliques favorisent l’activité biologique du sol.Ce travail de thèse a ainsi mis en évidence l’intérêt d’extraire les fractions hydrophobe (HPO*) et transphilique (TPH*) de la MOD de LDMA afin de les engager dans des processus de valorisation énergétique et agronomique.
The management of municipal solid waste leachates (MSWL) is technically and economically restrictive. It thus should be interesting to consider this effluent no more as a waste but rather as a partially valorizable “co-product”. The dissolved organic matter (DOM) is one of the major components of MSWL and presents a twofold interest: a high load and comparable processes of transformation to those of natural organic matter (NOM).This study thus aimed at extracting the DOM from MWSL according to its hydrophobic character and identifying ways of valorization. Only hydrophobic (HPO*) and transphilic (TPH*) fractions were considered because of their characteristics and reactivity. Two different ways of valorization were investigated: energetic valorization and enrichment of a soil with low content in organic carbon (Corg).The characterization of HPO* and TPH* fractions and their comparison with fractions of NOM confirmed their high valorizable potential. Indeed, they are physically and chemically comparable to NOM, they can be quantified at concentrations up to 1000 times higher than NOM (high extraction potential when compared to environmental matrices such as surface water), and they are more easily biodegradable than NOM without any phytotoxic character.An optimized BMP test was first developed by using an experimental design to adapt the experimental conditions to the digestion of MSWL. It was then applied in different conditions to highlight the impact of the hydrophobic character of the DOM of MSWL on the anaerobic digestion, and mainly on methane production. According to the results, the transphilic-like organic molecules improve the biogas production. Besides, the hydrophilic-like compounds with low aromatic character decrease the methane content of the produced biogas contrary to the hydrophobic fraction.Finally, organic fractions extracted from MSWL were relevant to enrich soil with low content in organic carbon. The HPO* fraction better improves the Corg content when compared to the TPH* fraction whereas transphilic-like molecules enhances the soil biological activity.With the results of this research study, the HPO* and TPH* fractions extracted from a MSWL can thus be considered both to produce biogas and particularly methane and to be amended on soils. Their extraction can thus be economically viable and their treatment no more highly costly.
Les deux principaux objectifs de cette thèse sont de développer les aspects théoriques et expérimentaux sur la co-méthanisation des déchets fermiers et alimentaires. Les objectifs de nos études ...portent sur l'élimination du maximum de déchets mis en ISDND, la réduction des pollutions des milieux naturels (eau, sol, air) par les effluents d'élevage, les boues de STEP et sur la mise en disposition d'une source énergétique renouvelable via le biogaz obtenu. Premièrement, nous avons effectué des expérimentations sur la co-méthanisation des effluents liquides, lisier de porc, boues de STEP, et de la vinasse et le mélange de ces effluents d'élevage avec les déjections solides des animaux (fumier, fientes) et des biodéchets (restes de repas). Ces expérimentations avaient pour but de suivre l'évolution du milieu réactionnel en fonction du composant du mélange ainsi co-digéré. Deuxièmement des tests des potentiels méthane et biogaz issus de mélange associant plusieurs types de déchets organiques sous différents états physiques (liquide, semi liquide, pâteux, solide) ont été effectués. La problématique qui se posait étant de savoir parmi les déchets à mélanger, quelle proportion de chaque mono-substrat donnera le meilleur potentiel méthanogène et s'il était possible de mettre en avant des effets synergétiques entre déchets. Nous avons fait appel à un outil statistique, le plan de mélange pour définir les mélanges à tester. Pour un mélange à 3 composants (fumier de vache, lisier de porc, restes de repas), le nombre d'expériences optimum à réaliser a été de 13. La réalisation du plan de mélange, c'est à dire la campagne expérimentale sur les co-méthanisations des 13 mélanges proposés nous a permis d'observer que le potentiel méthane d'un mélange dépend tout premièrement de sa texture (état physique) à l'entrée du processus. Un mélange contenant un maximum en proportion en co-produits liquides (lisier de porc) associé avec le maximum de déchets riches en substrats solubles (restes de repas) nous a donné les meilleurs potentiels méthane et biogaz. Cette observation a été confirmée par le taux de conversion de la matière sèche (MS) en matière volatile (MV) du mélange. Compte tenu du taux de MS, MV et le ratio MV/MS d'un mélange, ainsi que les interactions entre les composants du mélange, une loi permettant de prédire le potentiel biogaz d'un mélange doit considérer ces facteurs. Cette loi doit tenir compte de l'effet positif (synergisme) et l'effet négatif (antagonisme) entre les composants du mélange. Cette loi a été définie dans le but de prédire le potentiel méthane des mélanges constitués de fumier de vache, lisier de porc et restes de repas et se situant à l'intérieur du domaine expérimental défini par les limites sur les proportions minimale et maximale de chaque composant du mélange. Toutefois, cette loi définie n'est applicable qu'aux mélanges d'association de fumier de vache, de lisier de porc et des restes de repas. Cette loi a été définie pour estimer le BMP des mélanges, et ne permet pas de suivre le procédé de la méthanisation. Aussi, pour prédire le volume de biogaz (méthane) journalier ou cumulé de la cométhanisation.
The two main objectives of this thesis are to develop theoretical and experimental aspects of the anaerobic co-digestion of farm wastes associated with food. Our general studies have for objectives the elimination as much as possible the maximum of organic waste into non-hazardous landfills, reduce pollution of natural environments (water, soil, air) by the effluent livestock, sewage sludge, and dispose of energy via the produced biogas.Firstly, we carried out experiments on the anaerobic co-digestion of the liquid effluents association (pig slurry, sewage sludge, vinasse effluents) and the mixture of animal slurries, manures, and food waste. The aim of these experiments was to follow the evolution of the reactor behavior according to the component of the co-digested mixture.Secondly, BMP tests of mixture of association several types of organic waste under different physical condition (liquid, semi liquid, pasty, solid) were carried out. We have been tried to know, which proportion of each mono-substrate will give the best BMP among waste to mix? We used a statistical tool, the mixture design to define the mixtures to be tested. For a mixture with 3 components (cow dung, pig slurry, food waste), the optimum number of experiments to realize was 13.The realization of the mixture design, i.e. the experiment series on the anaerobic co-digestion of the 13 proposed mixtures enabled us to observe that the BMP of a mixture firstly depends on its texture (physical state) at the entry of the process. A mixture containing a maximum in proportion in liquid substrate (pig slurry) associated with food waste gave us the best biogas and methane potential. This observation was confirmed by the conversion rate of dry matter to volatile solid (VS) of the mixture. These results were proven by the activity (synergism, antagonism) of mixtures components influencing to BMP tests.The empiric law defined to predict the BMP of a mixture must to account the rate of VS/DM of a mixture, and the interactions between components of the mixture. This law must also include the positive effect (synergism) and negative (antagonism) between components of the mixture. This law has been defined in order to predict the potential methane mixtures of cow dung, pig slurry and food wastes and being within the experimental domain defined by the limits on minimum and maximum proportions of each component of the mixture. However, this definite law is applicable only to the mixtures of cow dung, pig slurry and food waste. The definite law is limited for prediction of mixtures BMP. However, this empiric law can not be used to follow reactor process. Model with three stages (hydrolysis of soluble substrate, acidogenic production stage and methanogenic stage) was used to predict daily and cumulative of biogas and methane production of anaerobic digestion of farm waste associated with vegetable waste. This model must be adapted with substrate type used and experimentations conditions (batch and mesophilic conditions). An adjustment of the model equations describing hydrolysis polymers stage was necessary in order to take into account of the concentration of polymers in particulate forms contained in complex substrates such as manure, slurry, and vegetable food waste. This adapted model was called model of Coupling. Indeed, a calibration of the most influential parameters of the model of Coupling, on the output must be carried out in order to validate the model.Daily and cumulative predictions of biogas and methane production of anaerobic digestion of farm waste associated with food waste were obtained by using adapted dynamical model. Model parameters values depend on the substrate type using in experimentation processes. Moreover, parameters values must be verified, needing further work.
Assessment of biogas production from MBT waste under different operating conditions Pantini, Sara; Iason VerginelliauthorDepartment of Civil Engineering and Computer Science Engineering, University of Rome Tor Vergata, Via del Politecnico, 1, 00133 Rome, Italy; Francesco LombardiauthorDepartment of Civil Engineering and Computer Science Engineering, University of Rome Tor Vergata, Via del Politecnico, 1, 00133 Rome, Italy ...
2015
Journal Article
Despite the considerable amount of data generated with respect to biochar application in the anaerobic digestion of sewage sludge, there is a research gap for correlations linking biochar ...physico-chemical parameters to anaerobic digestion performance. In the current study, cumulative methane production (CMP) from anaerobic digestion of sewage sludge amended with biochar is modeled by an Artificial Neural Network (ANN) (2 hidden layers, 12 neurons each) based on data compiled from 51 published biomethane potential tests (BMP). The model reflects the effects of 13 operational parameters covering physico-chemical properties of biochar, sludge characterization and operating conditions. Various types of sewage sludge and biochar under both mesophilic and thermophilic conditions have been successfully modeled with an R2 of 0.9924. An importance analysis is conducted to evaluate the significance of the model input parameters to CMP. Results indicate that operating conditions are more significant to CMP and that CMP is strongly correlated with biochar physical properties and chemical composition where chemical composition has the dominant effect. Overall, this study proves that biochar physico-chemical parameters are correlated to CMP and enables its forecasting under unexamined conditions thus assisting in process optimization, scale up and techno-economic analyses without resorting to BMP tests.
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•An ANN model for anaerobic digestion of sludge amended with biochar is developed.•Methane yield is predicted for various biochars and operating conditions.•Thirteen independent process parameters are considered for the first time.•Biochar physico-chemical properties are strongly correlated to methane yield.•Dominant effect of biochar chemical composition on cumulative methane production.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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