1,721,072 research outputs found
Thermophilic anaerobic co-digestion of cattle manure with agro-wastes and energy crops: comparison of pilot and full scale experiences
No full textThe paper deals with the benefits coming from the application of a proper process temperature (55 °C) instead of a ‘reduced’ thermophilic range (47 °C), that is often applied in European anaerobic co-digestion plants. The experimental work has pointed out that biogas production improve from 0.45 to 0.62 m3/kg VS operating at proper thermophilic conditions. Moreover, also methane content was higher: from 52% to 61%. A general improvement in digester behaviour was clear also considering the stability parameters comparison (pH, ammonia, VFA content). The second part of the study takes into account the economic aspects related to the capital cost of anaerobic digestion treatment with a 1 MW co-generation unit fro heat and power production (CHP). Moreover, the economic balance was also carried out considering the anaerobic supernatants treatment for nitrogen removal. The simulation showed how a pay-back-time of 2.5 yr and between 3 and 5 yr respectively could be determined when the two options of anaerobic digestion only and together with the application of a nitrogen removal process were considered.<br/
Smart approaches to food waste final disposal
Full text linkFood waste, among the organic wastes, is one of the most promising substrates to be used as a renewable resource. Wide availability of food waste and the high greenhouse gas impacts derived from its inappropriate disposal, boost research through food waste valorization. Several innovative technologies are applied nowadays, mainly focused on bioenergy and bioresource recovery, within a circular economy approach. Nevertheless, food waste treatment should be evaluated in terms of sustainability and considering the availability of an optimized separate collection and a suitable treatment facility. Anaerobic codigestion of waste-activated sludge with food waste is a way to fully utilize available anaerobic digestion plants, increasing biogas production, energy, and nutrient recovery and reducing greenhouse gas (GHG) emissions. Codigestion implementation in Europe is explored and discussed in this paper, taking into account different food waste collection approaches in relation to anaerobic digestion treatment and confirming the sustainability of the anaerobic process based on case studies. Household food waste disposal implementation is also analyzed, and the results show that such a waste management system is able to reduce GHG emissions due to transport reduction and increase wastewater treatment performance
Optimization of two-phase thermophilic anaerobic digestion of biowaste for bio-hythane production through reject water recirculation
Full text linkThe optimization of a two-phase thermophilic anaerobic process treating biowaste for hydrogen and methane production was carried out at pilot scale using two stirred reactors (CSTRs) and without any physical/chemical pretreatment of inoculum. During the experiment the hydrogen production at low hydraulic retention time (3d) was tested, both with and without reject water recirculation and at two organic loading rate (16 and 21 kgTVS/m3d). The better yields were obtained with recirculation where the pH reached an optimal value (5.5) thanks to the buffering capacity of the system. The specific gas production of the first reactor was 51 l/kgVSfed and H2 content in biogas 37%. The mixture of gas obtained from the two reactors met the standards for the biohythane mix only when lower loading rate were applied to the first reactor, with a composition of 6.7% H2, 40.1% CO2 and 52.3% CH4, and with an overall SGP of 0.78 m3/kgVSfed
Sustainability assessment of two digestate treatments: A comparative life cycle assessment
No full textDigestate derived from the anaerobic digestion of biowaste is a nutrient-rich substance whose direct use on land is not permitted by the Italian Legislation. The possibility of recovering its nutrients can be given by the processes of stabilisation and sanitation required by the Italian Legislation. Among these processes, composting and calcium hydrolysis with neutralization (CHN) permit to obtain useful soil improvers like compost and defecation gypsum (DG). In this paper a gate-to-gate Life Cycle Assessment (LCA) of these two processes is performed to evaluate their relative environmental sustainability, by using the ReCiPe H midpoint and endpoint impact assessment methods. The functional units (FUs) used in this analysis are one tonne of digestate treated by each process, and the amount of compost and DG necessary to amend one hectare of maize cultivation. Data used in the assessment were collected from plants located in Northern Italy and were referred to one year of operation. The processes of transport and spreading on land of the final products were not considered. The results of both the analyses show that CHN is the process with the largest environmental impacts, mainly due to the use of chemicals (i.e., sulfuric acid and calcium oxide). For both processes and FUs, the most impacted midpoint categories are Natural land transformation, Marine ecotoxicity and Freshwater ecotoxicity. Among the endpoint categories Resources is the most impacted one (followed by Human Health and Ecosystems), for both FUs, although showing larger differences for the agronomic use
Mesophilic to thermophilic conditions in codigestion of sewage sludge and OFMSW: evaluation of effluent stability using dynamic respirometric index (DRI) and biochemical methane potential (BMP).
No full textThe paper deals with the change from the mesophilic to thermophilic conditions in the codigestion process applied to secondary sludge from a biological nutrients removal (BNR) together with the organic fraction of municipal solid waste (OFMSW) or biowaste. The first part of the study was carried out at pilot scale in a 0.38 nr' pilot scale plant, in order to evaluate the process behaviour during short-time meso-thermo passage and the relative yield increase, in the second part, the same set of operational conditions was applied to a full scale 2000 m 3 digester: both pilot and full scale trials evidenced the same behaviour and results. The thermophilic range of temperature showed a general increase of performance of about 50% in terms of biogas yields and allowed for a better stabilisation of the effluent (digestate). In order to evaluate this aspect, both the aerobic and anaerobic rate of stability was evaluated: the effective rate of stabilisation of the digested material by means of aerobic (Dynamic Respirometric Index), and anaerobic batch tests (Biochemical Methane Potential) was determined. Preliminary tests on the effluents originated from three plants showed a DRI lower than 1000 mgO 2/kgVSh which is the minimum value required for a stable compost following the Italian regulation system, and an average SGP of 0,15-0,30 m 3/kgVS which demonstrated a partial conversion of the organic matter into biogas
Single and two phase thermophilic co-digestion of waste activated sludge and market waste. Performance comparison on pilot scale
No full textAnaerobic co-digestion effluent as substrate for chlorella vulgaris and scenedesmus obliquus cultivation
Full text linkAnaerobic digestate supernatant can be used as a nutrient source for microalgae cultivation, thus integrating phytoremediation processes with high value products storage in microalgae biomass. Microalgae are able to use nitrogen and phosphorous from digestate, but high nutrient concentration can cause growth inhibition. In this study, two microalgae strains (C. vulgaris and S. obliquus) were cultivated on the anaerobic co-digestion supernatant (obtained from the organic fraction of municipal solid waste (OFMSW) and waste activated sludge (WAS)) in a preliminary Petri plate screening at different dilutions (1:10 and 1:5) using a synthetic medium (ISO) and tap water (TW). Direct Nile red screening was applied on colonies to preliminarily identify hydrophobic compound storage and then a batch test was performed (without air insufflation). Results show that C. vulgaris was able to grow on digestate supernatant 1:5 diluted, while Nile red screening allowed the preliminary detection of hydrophobic compound storage in colonies. The analysis carried out at the end of the test on ammonia, phosphate, nitrate and sulphate showed a removal percentage of 47.5 ± 0.8%, 65.0 ± 6.0%, 95.0 ± 3.0% and 99.5 ± 0.1%, respectively
Hydrogen and Methane production from OFMSW and sewage sludge by two phases anaerobic codigestion.
No full textIn this paper a two-phase anaerobic codigestion of organic fraction of municipal solid waste and sewage sludge has been investigated experimentally. The aim of this work is to verify the feasibility and the performance of the process for the hydrogen and methane production. The experimental was carried out at pilot scale using two stirred reactors both maintained at thermophilic temperature (55°C) and fed semicontinuously with separate collected biowaste and sewage sludge. Nor chemicals neither recirculation were used to control the pH in first phase. The study lasted 50 days in which there were no evidences of any instability in the process.It was confirmed the possibility to obtain a stable hydrogen production with a specific average hydrogen production of 40 l per kg of total volatile solid (TVS) fed and a specific biogas production in the second phase of 0.32 m3per kgTVS fed.The biogas produced has a composition characterized by a stable presence of hydrogen over 5%. Therefore, the biogas produced meets the composition characteristic of biohythane
Evaluation of wine lees ultrasonic cavitation as pre-treatment and its possible use as substrate for microalgae biomass production
No full textUltrasonic cavitation is a technology used to improve organic carbon solubilization of a substrate, increasing its biodegradability for further biological treatment. Moreover, its application has a pasteurization effect on waste stream. In this study, different cavitation times (5, 10, 20 and 30 min) are tested on white and red wine lees to evaluate the organic compounds solubilization, physical-chemical variation and antimicrobial cavitation effects, with the aim of further valorization with biotechnological applications such as microalgae growth. Wine lees cavitated effluents are applied as substrate for Chlorella vulgaris growth, obtaining a microalgae-yeast microbial community biomass of 2.4 ± 0.7 g L−1 (WL) and 1.7 ± 0.0 g L−1 (RL) with 33.9 ± 4.1 % (WL) and 60.5 ± 5.3 % (RL) of lipids content. Ultrasound cavitation is efficient in controlling native microorganism proliferation (yeast and mold) only applying at least 10 min of pretreatment. This pretreatment allows to change chemical-physical and microbiological properties of wine lees, that are compatible as organic substrate for microalgae cultivation in a circular economy approach
Pretrattamenti di fanghi e FORSU per l’ottimizzazione della digestione anaerobica
No full textI fanghi di supero e la Frazione Organica dei Rifiuti Solidi Urbani (FORSU) rappresentano due comuni matrici organiche impiegate in processi di digestione anaerobica. Tuttavia, una conduzione del processo che restituisca risultati vantaggiosi in termini di produzione del biogas e stabilizzazione delle matrici richiede che esse vengano sottoposte a trattamenti preliminari. Tali trattamenti hanno necessariamente caratteristiche diverse in funzione della tipologia di matrice che si intende trattare e dei risultati che si intendono conseguire. L’obiettivo da raggiungere, nel caso dei fanghi, è rappresentato da un incremento della biodegradabilità, ottenibile, soprattutto per i cosiddetti fanghi di supero, attraverso il trasferimento della materia organica dall’interno delle cellule dei microorganismi al liquido interstiziale attraverso processi di lisi meccanica o termica. Circa la FORSU, la scelta del pretrattamento ottimale va nell’ottica di massimizzare l’efficienza di separazione del materiale organico da avviare a digestione anaerobica con la contemporanea ottimizzazione dei costi di gestione del processo
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