Suchergebnisse

"Thèse en cotutelle pour le doctorat en génie des eaux Université Laval Québec et Ghent University à Ghent, Belgique" ; La prise de conscience croissante de l'épuisement des ressources naturelles, la demande croissante de nutriments et d'énergie pour la production alimentaire et les normes de plus en plus strictes de décharge des nutriments et de fertilisation, ont donné lieu à une attention accrue pour la récupération des nutriments à partir des déchets municipaux et agricoles. Cette thèse de doctorat vise à stimuler la transition vers une bio-économie en fournissant des (moyens à développer des) stratégies durables pour la récupération des nutriments à partir des déchets organiques après la production de bio-énergie par la digestion anaérobie. Une attention particulière est accordée à la valorisation des produits récupérés comme substituts renouvelables aux engrais chimiques et/ou comme engrais organo-minéraux durables dans l'agriculture. Trois phases de recherche complémentaires ont été exécutées: 1) l'inventaire des technologies et la classification des produits, 2) l'évaluation de la valeur des produits, 3) la modélisation et l'optimisation des procédés. Dans la première phase, une revue systématique des technologies et une classification des produits ont été réalisées. Dans la seconde phase, la caractérisation des produits et des analyses de bilan de masse dans des stations de récupération des ressources de l'eau et des déchets (StaRRED) à grande échelle ont été exécutées. Une évaluation économique et écologique de différents scénarios de bio-fertilisation a été menée et les scénarios les plus durables ont été sélectionnés pour une évaluation agronomique réalisée ultérieurement sur le terrain et à l'échelle de la serre. Dans la troisième phase, une librairie générique de modèles pour la récupération des nutriments a été élaborée visant à modéliser la quantité et la qualité d'engrais. Une meilleure compréhension de la performance et des interactions des processus unitaires a été obtenue par des analyses de sensibilité globale. Les modèles ont été utilisés avec succès comme un outil pour la configuration et l'optimisation des chaînes de traitement. Sur la base de toutes les connaissances acquises, une feuille de route générique pour la mise en place des stratégies de récupération des nutriments en fonction des marchés et des législations des engrais, et de la caractérisation des déchets a été développée. En tant que telle, la présente thèse développe les concepts de fermeture maximale des cycles des nutriments dans une approche du berceau-au-berceau. Le travail apporte des preuves importantes de l'impact positif des produits récupérés sur l'économie, l'agronomie et l'écologie de la production végétale intensive. En outre, cette thèse offre des informations et des outils fondamentaux pour faciliter la mise en œuvre et l'optimisation des stratégies durables de récupération des nutriments. Ces résultats ouvrent de nouvelles possibilités pour une croissance économique durable axée sur les ressources biologiques et créent ainsi une situation gagnant-gagnant pour l'environnement, la société et l'économie en Belgique, au Canada, et au-delà. ; The increasing awareness of natural resource depletion, the increasing demand of nutrients and energy for food production, and the more and more stringent nutrient discharge and fertilization levels, have resulted in an increased attention for nutrient recovery from municipal and agricultural wastes. This PhD dissertation aims at stimulating the transition to a bio-based economy by providing (tools to develop) sustainable strategies for nutrient recovery from organic wastes following bio-energy production through anaerobic digestion (= bio-digestion waste). Particular attention is paid to the valorization of the recovered products as renewable substitutes for chemical fertilizers and/or as sustainable organo-mineral fertilizers in agriculture. Three complementary research phases were conducted: 1) technology inventory and product classification, 2) product value evaluation, 3) process modelling and optimization. In the first phase, a systematic technology review and product classification was performed. In phase 2, product characterizations and mass balance analyses at full-scale waste(water) resource recovery facilities (WRRFs) were executed. An economic and ecological evaluation of different bio-based fertilization scenarios was conducted and the most sustainable scenarios were selected for subsequent agronomic evaluation at field and greenhouse scale. In phase 3, a generic nutrient recovery model library was developed aiming at fertilizer quantity and quality as model outputs. Increased insights in unit process performance and interactions were obtained through global sensitivity analyses. The models were successfully used as a tool for treatment train configuration and optimization. Based on all acquired knowledge, a generic roadmap for setting up nutrient recovery strategies as function of fertilizer markets, legislations, and waste characterization was established. As such, the present dissertation further develops the concepts of maximally closing nutrient cycles in a cradle-to-cradle approach. The work reveals important evidence of the positive impact of recovered products on the economy, agronomy, and ecology of intensive plant production. Moreover, it provides the fundamental information and tools to facilitate the implementation and optimization of sustainable nutrient recovery strategies. All of this may open up new opportunities for sustainable and more bio-based economic growth and thus create a win-win situation for the environment, the society, and the economy in Belgium, Canada, and beyond.

Although to date some technologies producing bio-based phosphorus (P) fertilizers have been proposed and implemented, the efficient use of the recovered products is still limited due to legislative constraints and lack of insights in the P release with time and in the corresponding mechanisms. The aim of this work was to evaluate the fertilizer performance in terms of P release and use efficiency of recovered struvite, FePO4-sludge, digestate, and animal manure as compared to fossil reserve-based mineral triple superphosphate (TSP). First, product physicochemical characteristics and P fractions in the context of European fertilizer legislation were assessed. Next, a controlled greenhouse experiment was set up to evaluate plant reactions as well as changes of P availability in a sandy soil with high P status and a Rheinsand soil with low P status. Soil P fractions were determined in the extracts with water, ammonium lactate and CaCl2, and in soil solution sampled with Rhizon soil moisture samplers. Based on all results, it is worth conducting long-term field trials to evaluate the P release effect of struvite and digestate as compared to animal manure and TSP on different soil types with varying P status. These products showed promise as sustainable substitutes for conventional P fertilizers and could contribute to a more efficient use of P in agriculture. A refined classification of P application standards/recommendations in terms of soil P status, soil texture, and fertilizer characteristics, next to the crop P demand, is recommended. Moreover, the additional use of Rhizon samplers for determination of direct available P, including dissolved organic P, is proposed for better understanding and categorization of different P fertilizers in environmental and fertilizer legislations.

In the transition from a fossil to a bio-based economy, it has become an important challenge to maximally recuperate valuable nutrients coming from waste streams. Nutrient resources are rapidly depleting, significant amounts of fossil energy are used for the production of chemical fertilizers, whereas costs for energy and fertilizers are increasing. In the meantime, biogas production through anaerobic digestion produces nutrient-rich digestates. In high-nutrient regions, these products cannot or only sparingly be returned to agricultural land in its crude unprocessed form. The consequent processing of this digestate requires a variety of technologies producing lots of different derivatives, which could potentially be re-used as green fertilizers in agriculture. As such, a sustainable alternative for fossil-based mineral fertilizers could be provided. This study aims to characterize the physico-chemical properties of digestates and derivatives, in order to identify the fertilizer value and potential bottlenecks for agricultural re-use of these products, in line with European legislative constraints. In addition, the economic and ecological benefits of substituting conventional fertilizers by bio-based alternatives are quantified and evaluated. Waste water from acidic air scrubbers for ammonia removal shows potential for application as N-S fertilizer. Analogously, concentrates resulting from membrane filtrated liquid fraction of digestate show promise as N-K fertilizer. Substituting conventional fertilizers by digestate derivatives in different cultivation scenarios can result in significant economic and ecological benefits for the agriculturist. Starting from theoretical scenarios outlined in the current study, field test validation will be required to confirm the potential substitution of fossil-based mineral fertilizers by bio-based alternatives.

Anaerobic digestion is an established technology to convert biowaste into renewable energy and nutrient-rich digestates. Nutrient recovery from these digestates as renewable fertilizers with high-nutrient use efficiency or as P-poor alternative fertilizers has gained increased attention in order to meet both regulatory drivers and market demands, while producing an internal revenue source. However, until now, this opportunity has been difficult to realize due to obstacles and inconsistencies in legislative systems, and lack of insights into the composition and properties of these products, as well as in their impact on crop yield and soil quality. The aim of this review is to prove the effectiveness of fertilization strategies using biodigestion waste derivatives as compared to conventional practices using animal manure and chemical fertilizers. As adequate field-scale data are lacking in the literature, a ground-breaking three-year field trial has been performed. The value and impact of these biobased fertilizers are demonstrated by the use of high-level performance indicators measuring farming pressure on the environment and how that pressure is changing over time. Bottlenecks for marketing and legislative constraints are discussed. An economic and ecological evaluation is also assessed. The proof of concept provided in this chapter should help to better classify these biobased products into fertilizer and environmental legislations and serve as a support to stimulate their use in the farming community. Moreover, this review should stimulate and provide guidance for further field research on biobased fertilizers, which is highly essential in the development and implementation of more effective and environmentally friendly farming strategies.

In the transition from a fossil to a bio-based economy, it has become an important challenge to maximally recycle valuable nutrients that currently end up in waste streams. Nutrient resources are rapidly depleting. Significant amounts of fossil energy are required for the production of synthetic fertilizers, whereas costs for energy and fertilizers are increasing. Meanwhile, biogas production through anaerobic digestion produces nutrient-rich digestates, which could potentially be reused as green fertilizers in agriculture, thereby providing a sustainable substitute for synthetic fertilizers. The aim of this study was to evaluate the impact of using bio-digestion waste derivatives instead of synthetic fertilizers and/or animal manure on soil and crop production. In a field trial, nutrient balances were assessed and the physicochemical soil fertility and quality were evaluated. The biogas yield of the harvested energy crops was determined. An economic and ecological evaluation was conducted. Application of bio-digestion waste derivatives induced small, albeit statistically insignificant improvement in crop yield, soil fertility and quality compared to current common practices using animal manure and synthetic fertilizers. Moreover, the use of these products might stimulate nutrient mobilization from the soil, thereby increasing the use efficiency of soil minerals. For all reuse scenarios the calculated economic and ecological benefits were significantly higher than the reference. It is clear that the reuse of bio-based products as nutrient supply in agriculture should be stimulated in European legislation. Further field research is on-going in order to validate the results and evaluate the impact on soil quality in the longer term.

Nutrient recovery from digested biodegradable waste as marketable products has become an important task for anaerobic digestion plants to meet both regulatory drivers and market demands, while producing an internal revenue source. As such, the present waste problem could be turned into an economic opportunity. The aim of this study was to provide a comprehensive overview and critical comparison of the available/emerging technologies for nutrient recovery from digestate, and a classification of the resulting end-products according to their fertilizer characteristics. Based on the stage of implementation, the technical performance, as well as financial aspects, struvite precipitation/crystallization, ammonia stripping and (subsequent) absorption using an acidic air scrubber were selected as best available technologies to be applied at full-scale for nutrient recovery as marketable fertilizer commodities. The resulting end-products can and should be classified as renewable nitrogen–phosphorus (N/P) precipitates and nitrogen–sulfur (N/S) solutions, respectively, in fertilizer and environmental legislations. This would stimulate their use and foster nutrient recovery technology implementation.