Performance of Coupling an Aerobic Pre-treatment Prior to a Solid-State Anaerobic Digestion of Food Waste

International audienceAn experimental design was proposed to test the influence of three parameters on the performance of food waste (FW) dry anaerobic digestion (AD) coupled with aerobic pre-treatment: (1) the type of aerobic pre-treatment (no pre-treatment/dynamic aeration/static storage); (2) the composition of FW (paper/no paper) and (3) the frequency of leachate recirculation in the batch leach bed reactor (LBR) used as dry AD process. Performance of AD was assessed by measuring pH, VFA, biogas production and by modelling the kinetics of methane production using modified Gompertz equation. A statistical analysis of variance showed that AD leachate recirculation condition was the most impacting parameter on methane production. A high production of VFA was noticed (~ 25 gDCO·L '1 ) that did not lead to inhibition due to high buffer capacity of inoculum (5.2 gN-NH 4 + ·L '1 ). 80% of the biomethane potential was reached in the batch test with a daily leachate recirculation and with FW without paper. According to simulations, an experimental duration of 31'32 days showed to be optimal to reach 90% of degradation potential under these LBR conditions. A lower frequency of leachate recirculation or the addition of paper decreased methane production. The introduction of a two-day aeration step stabilized the production of VFA along the digestion process and enhanced the methane production on FW with paper. Conversely a two-day storage step induced a rapid acidification and a subsequent significant decrease of methane production rate. © 2019, Springer Nature B.V

Méthode d'optimisation pour l'élaboration de réseaux de micro digesteurs anaérobies pour le traitement décentralisé des biodéchets en milieu urbain et périurbain

International audienceInnovative small scale treatments solutions are currently proposed to handle the growing need of biowaste valorization through a more circular economy. These new approaches are designed to be embedded in a decentralized treatment scheme which raises new challenges for the biowaste management at the territorial scale. This study, aimed at developing a method to design decentralized and micro-scale Anaerobic Digestion (mAD) networks in urban and peri-urban areas. A mixed integer linear program (MILP) was set up to identify the number of mAD, their sites and their capacities in order to minimize the payload-distances of biowaste and digestate transportation while taking into account the technical constraints of the system. A Geographic Information System (GIS) methodology was developed to feed the MILP model with very fine-scale data about (1) the location and the characterization of the biowaste sources and of the digestate outlets (agricultural areas), and (2) the location of the potential sites for mAD based on a multi-criteria analysis that includes environmental regulations, urban planning rules, site accessibility and heat outlets for valorization. The method was applied to the territory of The Grand Lyon Metropole (534 km2) in France. Optimized mAD networks were identified through the MILP according to different scenarios tested

Influence of Origin and Post-treatment on Greenhouse Gas Emissions After Anaerobic Digestate Application to Soil

Anaerobic digestion is a beneficial organic waste management technology that, in addition to biogasused for energy production, produces a by-product called anaerobic digestate, which can be used as a fertilizer or as an amendment as long as it has no harmful effects on the environment. The objective of the research described in this article was to assess one of these possible harmful effects, associated with the release of greenhouse gas emissions (GHG). Four anaerobic digestates were subjected to phase separation, and some of them also to composting, drying or reverse osmosis. Carbon dioxide (CO2) and nitrous oxide (N2O) emissions were measured during incubations of soil-digestate mixtures under controlled conditions. The mineralization of organic carbon reached 28–58 % of digestate organic carbon after 3 months in the presence of the solid digestates, and was lower (18–42 %) for the liquid digestates. The raw digestates had intermediate intensity of organic carbon mineralization to CO2. Drying and composting reduced CO2 emissions by stabilizing the digestate organic matter. N2O emission factors varied between 0.11 and 2.10 % of total digestate N depending on the origin and state of the digestates (raw, solid, liquid, composted). The highest emissions were measured with the raw digestates, and the lowest generally with the liquid ones. The study showed that in addition to phase separation, composting also reduced GHG emissions whereas drying and reverse osmosis considerably increased these emissions. Compostedand dried digestates can be used as organic amendment leading to potential carbon storage larger than GHG emission, while for raw digestates, the GHG emissions always exceeded potential C storage

Storage of Food Waste: Variations of Physical'Chemical Characteristics and Consequences on Biomethane Potential

International audienceFood waste (FW) storage influences its physical'chemical characteristics and anaerobic digestion (AD) performance. In this work we present the results of two weeks long experiment where two types of FW were stored in dedicated cells (10 L and 300 L). Air was evenly flushed on the top surface of the substrates and then analyzed to identify and quantify possible gaseous emissions. Solid and liquid fractions were also periodically sampled and analyzed for total solid, volatile solid, ammonia and VFA contents. Results showed that storage initiated a hydrolysis process that modified the physical structure of FW, leading to the production of gases (CH4, CO2 and ethanol) and a partly liquefied FW. Depending on experimental conditions, a fraction between 61 and 70% of the initial substrate remained solid at the end of the storage period. In the liquid phase, a large proportion of lactic acid was measured with maximum contents of 5.9 and 14.8 g/kgvs for the small-scale experiments with two different FW types and 3.0 g/kgvs for the large-scale experiment, leading to inhibition of the biomethane potential (BMP) tests. In conclusion, this work showed that when storage of FW is needed before AD, the optimal time recommended to keep a high methane yield is one week. © 2019, The Author(s)

La méthanisation en milieu rural et ses perspectives de développement en France

De nombreux pays européens s’accordent sur le fait que la méthanisation est un réel atout pour le développement durable. Les différentes approches qu’ils mettent en œuvre sont autant de modèles intéressants à étudier. En effet, quelles prises de positions par rapport aux points positifs et négatifs de ce procédé dénotent ces choix ? Dans quelle mesure permettent-ils une mise en perspective constructive pour l’avenir de la méthanisation

Physico-chemical, biochemical and nutritional characterisation of 42 organic wastes and residues from France

International audienceThe data presented in this article regroup characterisation of organic matter and nutritional composition of 42 organic wastes and residues usually used as substrates for anaerobic digestion. Those wastes have different origins from agro-industrial, agricultural and urban sectors in France including: algae, slaughterhouse waste, fat, food waste, fruits and vegetables residues, green waste, slurry, manure, wastewater treatment plant sludge and agricultural residues. The properties of organic matter are distinguished between global parameters (pH, total solids, volatile solids, COD and BMP), organic matter fractionation (biochemical and Van Soest) and the main nutrients content (N, P, K, Mg, Ca and S). © 2018 The Author

Methods to Assess Biological Transformation of Biomass

The aim of this chapter is to provide a description of the main methods used to assess biological transformation of biomass. It will address saccharification tests which account for the ability of biomass to release sugars during enzymatic hydrolysis. Biochemical methane potential (BMP) tests, which are widely used to assess anaerobic digestibility of biomass for the production of methane and BMP prediction by near infra-red spectroscopy will be presented. Biohydrogen potential (BHP), used to assess the ability to produce biohydrogen from biomass by dark fermentation will be described. Respirometry tests accounting for assessing aerobic degradability of biomass will be described. Incubation tests used to assess carbon and nitrogen degradation in soils will also be presented