Composting modelling : towards a better understanding of the fundamentals, applications for enhanced nutrient recycling, greenhouse gas reduction, and improved decision-making

Cette thèse de doctorat vise à consolider, développer et appliquer nos connaissances sur la modélisation du compostage, dans le but de fournir des informations, des outils et des perspectives accessibles et utilisables pour les chercheurs et les décideurs. L'espoir est que les travaux développés tout au long de cette thèse puissent aider à optimiser les procédés de compostage, notamment en réduisant les émissions de gaz à effet de serre (GES) et en améliorant le recyclage des nutriments. A ce titre, la thèse est divisée en trois phases : (1) la phase 1 est une consolidation et un développement des notions fondamentales de la modélisation du compostage, (2) suivie de la phase 2, où la modélisation de la perte de nutriments et des émissions de GES est étudiée, (3) avec la phase 3 qui est axée sur la manière d'assurer que ce travail puisse être utilisé par les décideurs et acteurs dans le milieu de compostage. Dans la première phase, une revue complète et systématique de l'ensemble de la littérature sur la modélisation du compostage a été entreprise (chapitre 2), cherchant à fournir une meilleure compréhension du travail qui a été fait et sur la direction des travaux futurs. Ceci a été suivi d'une étudie détaillée des approches de modélisation cinétique actuelles, notamment par rapport aux facteurs de corrections cinétiques appliqués à travers le domaine (chapitre 3). La phase 2 s'est ensuite focalisée sur les notions spécifiques relatives aux émissions de GES et aux pertes de nutriments lors du compostage, et à la modélisation de ces phénomènes. Cette thèse présente les réacteurs expérimentaux et le plan conçu pour suivre et évaluer le processus de compostage (chapitre 4), ainsi que le modèle de compostage compréhensif développé pour prédire avec précision les émissions et la transformation des nutriments pendant le compostage (chapitre 5). Enfin, la phase 3 visait à rendre ces informations facilement et largement utilisables. Cela a commencé par une évaluation des meilleures pratiques pour développer des modèles et des systèmes d'aide à la décision pour la prise de décision environnementale (chapitre 6), suivi par le développement de nouvelles approches de modélisation cinétique simples (chapitre 7), culminant avec le développement, l'ajustement paramétrique et la validation d'un modèle de compostage parcimonieux (chapitre 8). Grâce à ce travail, une base consolidée de l'état actuel de la modélisation du compostage a été développée, suivie par l'exploration et le développement de connaissances et d'outils à la fois fondamentaux et applicables.This PhD thesis aims consolidating, developing, and applying our knowledge on composting modelling, with the goal of providing accessible and usable information, tools, and perspectives for researchers and decision-makers alike. The hope is that the work developed throughout this dissertation can help in optimizing composting, notably by reducing greenhouse gas (GHG) emissions and improving nutrient recycling. As such, the thesis is divided into three phases: (1) phase 1 is a consolidation and development of the fundamentals of composting modelling, (2) followed by phase 2, where the modelling of nutrient loss and GHG emissions is investigated, (3) with phase 3 focusing on how to ensure that this work can be used by decision-makers. In the first phase, a comprehensive and systematic review of the entirety of the literature on composting modelling was undertaken (chapter 2), seeking to provide a better understanding on the work that has been done and guidance on where future work should focus and how it should be approached. This review then raised some interesting questions regarding modelling approaches, notably regarding modelling of composting kinetics, which was studied in detail through the evaluation of current modelling approaches (chapter 3). Phase 2 then focused on the specific notions relating to GHG emissions and nutrient loss during composting, and how to model these phenomena. This section starts with a presentation of the experimental reactors and plan designed to monitor and evaluate the composting process (chapter 4), followed by the comprehensive composting model developed to accurately predict emissions and nutrient transformation during composting (chapter 5). Finally, phase 3 aimed to make this information easily and widely usable, especially for decision-makers. This started with a review on the best practices to develop models and decision support systems for environmental decision-making (chapter 6), followed by the development of novel simple kinetic modelling approaches (chapter 7), culminating with the development, calibration, and validation of a parsimonious composting model (chapter 8). Through this work, a consolidated basis of the current state on composting modelling has been developed, followed-up by the exploration and development of both fundamental and applicable knowledge and tools

Evaluation of the odoriferous impact derived from the treatment of organic waste

El aumento progresivo de la población, la industrialización y el consumismo son los factores principales por los que ha incrementado la generación de residuos en los últimos años, requiriendo de una gestión integral para proteger la salud pública y el medio ambiente. La gestión y tratamiento adecuado de los residuos sólidos urbanos constituye, actualmente, un problema clave en materia de sostenibilidad, ya que es necesario dar solución a un problema ambiental, económico, social y sanitario, evitando la clásica deposición en vertederos. Sin embargo, el tratamiento de residuos orgánicos incrementa la contaminación por olores desagradables. Dichas emisiones han de ser evaluadas, cualitativa y cuantitativamente, con el propósito de minimizarlas. Actualmente se utilizan diversas herramientas y dispositivos de muestreo que permiten, según las normativas aplicables en el seguimiento de olores (EN 13725 y VDI 3880), llevar a cabo la evaluación de los procesos que generan malos olores y cuantificar las emisiones para dar una magnitud real de cuánto olor emite un foco emisor. Para analizar los compuestos olorosos, en focos emisores, la olfatometría dinámica se ha establecido como una técnica sensorial adecuada que cuantifica la concentración de olor de una muestra olorosa (ouE/m3). Sin embargo, los materiales utilizados en el almacenamiento de las muestras gaseosas pueden no ser estancos para ciertos compuestos olorosos. En este sentido, y en colaboración con el Laboratory of Industrial Environment Engineering (Ecole des Mines d'Alès, Francia), se ha realizado un estudio de los efectos de permeabilidad y adsorción de diversos compuestos de azufre volátiles a través de las bolsas de muestreo de Nalophan®. El sulfuro de hidrógeno (H2S), metilmercaptano (metil-SH) y disulfuro de carbono (CS2) son los que presentan una menor retención en el interior de las bolsas debido a su tamaño y estructura molecular, lo cual ha derivado en una pérdida global del 10% a las 30 h de almacenamiento y del 25% a las 95 h. Además, las válvulas necesarias para la recolección de muestras han dado lugar a pequeñas pérdidas de compuestos por adsorción. Con objeto de profundizar en las emisiones de olor generadas durante el tratamiento de residuos orgánicos, se han llevado a cabo estudios a escala de laboratorio, piloto e industrial de distintas materias residuales. A escala de laboratorio se ha realizado el seguimiento del proceso de co-compostaje en vasos Dewar de lodo de depuradora de aguas residuales municipales con distintas proporciones de residuo del cultivo de la planta de berenjena, insertando como novedad unas conducciones verticales de PVC perforadas para favorecer las condiciones aerobias del proceso. El pico de olor generado durante la etapa hidrolítica del proceso de compostaje se ha minimizado con una mayor proporción de residuos de berenjena en la mezcla con los lodos. Asimismo, la estabilidad del compost obtenido al final del proceso, demuestra la viabilidad de la tecnología para valorizar ambas materias residuales, al igual que la concentración de fósforo arroja mejores resultados, en cuanto a calidad del producto final, que el lodo compostado individualmente. Se ha demostrado que la reducción de la concentración de sólidos volátiles ha sido la principal causa en la emisión de compuestos olorosos durante el proceso, de forma más significativa que la eliminación de compuestos nitrogenados. A escala piloto se ha evaluado el proceso de compostaje en un respirómetro dinámico y, dado que las condiciones operacionales están más controladas que en una instalación industrial, se han realizado estudios con diversas materias residuales (lodo de depuradora, cáscara de naranja, residuo de la manufactura del pescado, residuo del extrusionado de fresa y fracción orgánica de residuos sólidos urbanos) evaluando, mediante la aplicación de herramientas estadísticas avanzadas, la importancia de las variables del proceso sobre el impacto oloroso. En este sentido, un análisis de componentes principales de la matriz de datos obtenida ha permitido clasificar los sustratos por su origen, siendo el índice respirométrico dinámico (proporcional a la velocidad de consumo de oxígeno en la biodegradación) y la tasa de emisión de olor las variables más influyentes. Otra de las herramientas estadísticas aplicada es la regresión multivariante, demostrando ser una técnica adecuada en la predicción de concentración y/o tasa de emisión de olores. La regresión multivariante ha sido una herramienta a partir de la cual se han evaluado las variables operacionales más influyentes en la generación de olores. Además, se han determinado los grupos funcionales, asociados a los compuestos presentes en las materias residuales mediante la aplicación de la novedosa tecnología NIR, encontrándose una clara relación entre estas y las emisiones de olor generadas durante el tratamiento. A escala industrial, se ha elaborado un mapa global de olor de una planta de tratamiento de residuos sólidos urbanos de Córdoba capital, en el que se han identificado los puntos críticos de emisión de olor y las variables más influyentes en su generación. En este sentido, la recepción de basura orgánica y de lodos de depuradora (procedentes de la planta de tratamiento de aguas residuales “La Golondrina”) son los puntos críticos más olorosos, con tasas de emisión de 14,57 y 2,41 ouE/s·m2, respectivamente. Además, considerando la variabilidad de puntos críticos en la planta, y tras realizar un estudio global de ellas, las variables respirométricas, la concentración de nitrógeno y el tiempo de residencia de los materiales residuales han destacado como las más influyentes en el impacto oloroso. Finalmente, también se ha estimado dicho impacto oloroso en una planta de compostaje que gestiona lodos de depuradora (pretratado y sin pretratar) y residuos de mercado mediante compostaje en pilas, en términos de concentración de inmisión, con el propósito de evaluar la generación y posterior dispersión de las emisiones olorosas en las zonas colindantes. A partir de un modelo de dispersión Gaussiano de pluma se han obtenido los perfiles de inmisión en función de la distancia de la planta considerando la orografía, condiciones meteorológicas y atmosféricas más desfavorables. La concentración de inmisión máxima observada no ha superado en ningún caso los límites establecidos en el borrador del Anteproyecto de ley contra la contaminación odorífera de Cataluña de 3 ou/m3, con una estabilidad atmosférica neutra y una velocidad del viento de 2,6 m/s. Además, el seguimiento del proceso de compostaje a partir de las variables tradicionales ha demostrado que las emisiones olorosas derivadas de la planta de tratamiento y gestión de residuos sólidos orgánicos mediante compostaje están nuevamente relacionadas con la volatilización de nitrógeno y la eliminación de los sólidos volátiles. Los novedosos resultados obtenidos en los trabajos de investigación que componen esta Tesis Doctoral suponen un avance científico significativo en términos de cuantificación y determinación de emisiones olorosas derivadas del tratamiento de residuos. La aplicación de las nuevas herramientas utilizadas en este trabajo podrían contribuir a mitigar el impacto oloroso que genera la gestión y tratamiento de residuos, un proceso que a día de hoy se considera indispensable y que trata de dar una nueva vida a los millones de toneladas de materia orgánica que cada día genera el ser humano.The progressive increase in population, industrialization and consumerism are the main factors leading to the enhancement of waste generation during the last years, which requires integrated management to protect public health and environment. The adequate management and treatment of urban solid waste is nowadays a major issue in terms of sustainability, leading to the necessity of solving an environmental, economic, social and sanitary problem by avoiding classical landfilling. Nevertheless, the treatment of organic waste promotes pollution by the generation of unpleasant odor. The emission of odor should be evaluated qualitative and quantitatively with the aim of achieving its minimization. Several sampling tools and devices are currently being used in accordance with the legislation on odor monitoring (EN 13725 and VDI 3880) to evaluate those processes that generate unpleasant odor and to quantify their emission by providing a real magnitude on how much odor an emission source generates. Dynamic olfactometry has been stablished as an adequate sensorial technique to analyze the odor concentration in an odorous sample (ouE/m3). However, the materials used for storing gaseous samples might not be watertight for certain odorous compounds. In this context, and in collaboration with the Laboratory of Industrial Environment Engineering (Ecole des Mines d'Alès, France), a study of the permeability and sorption effects of several volatile sulfur compounds stored in sampling Nalophan® bags was carried out. Hydrogen sulfide (H2S), methyl mercaptan (methyl- SH) and carbon disulfide (CS2) showed the lowest retention inside the sampling bags due to their molecular size and structure, which led to global loss of 10% after 30 h of storage time and 25% at 95 h. Furthermore, the valves necessary to store gaseous samples led to small loss due to sorption processes. With the aim of deepening in odorous emissions derived from the treatment of organic waste, several research studies of different residual substrates were carried out at laboratory, pilot plant and industrial scales. The monitoring process of co-composting sewage sludge from wastewater treatment at different mixing proportions with eggplant waste was carried out in Dewar vessels at laboratory scale. As a novel aspect, vertical and perforated PVC pipes were inserted in the vessels to favor aerobic conditions inside the substrates being composted. The odor peak generated during the hydrolytic stage of composting was minimized by increasing the proportion of eggplant waste in the mixture with sewage sludge. Likewise, the stability of the final product demonstrates the feasibility of cocomposting to valorize both residual substrates simultaneously. Furthermore, the concentration of phosphorus was higher in the final compost than the value obtained when sewage sludge was composted individually. The reduction of the concentration of volatile solids was found to be the main cause of odor emission, being more influential than the removal of nitrogenous compounds. On the other hand, the composting process was also evaluated in a dynamic respirometer at pilot plant scale. As the operational conditions were more controlled than at industrial scale, several studies were carried out with several residual substrates (sewage sludge, orange peel, fish waste, strawberry extrudate and organic fraction of municipal solid waste) to evaluate the importance of the process variables on the odorous impact through advanced statistical tools. In this sense, a principal components analysis applied to the data matrix obtained allowed classifying residual substrates by origin, with the dynamic respirometric index (proportional to the oxygen consumption rate during biodegradation) and the odor emission rate being the most influential variables. Another statistical tool used was multivariate regression, which has been demonstrated to be an adequate technique to predict odor concentration and/or emission rate. Multivariate regression was used to evaluate the most influential operational variables in odor generation. In addition, the functional groups associated to the compounds contained in the residual substrates were determined by the innovative NIR technology. A relationship between functional groups and odor emission generated during waste treatment was identified. At industrial scale, a global odor map of a solid waste plant that treats residues generated in the city of Cordoba was elaborated. Such a map identified the critical odor emission points and the most influential variables in its generation. Reception of organic waste and sewage sludge derived from the wastewater treatment plant “La Golondrina” were found to be the most critical points in terms of odor generation, with odor emission rates up to 14.57 and 2.41 ouE/s·m2, respectively. Furthermore, after considering the variability of critical points inside the plant and having carried out a global analysis, respirometric variables, nitrogen concentration and residence time of residual substrates were identified as the most influential variables on the odorous impact. Finally, the odorous impact derived from a plant that manages sewage sludge (raw and pretreated) and market waste through composting in piles was estimated in terms of immision concentration, with the aim of evaluating the generation and subsequent dispersion of odorous emissions in neighboring areas. By applying a plume Gaussian dispersion model, the immision profiles as a function of distance were obtained considering orography and the most unfavorable weather and atmospheric conditions. The maximal immision concentration did not exceed the threshold stablished by the draft law against odorous pollution in Cataluña (3 ou/m3), at neutral atmospheric stability and wind speed of 2.6 m/s. In addition, monitoring composing process through traditional variables demonstrated again that odorous emissions derived from the treatment and management of organic solid waste are related to nitrogen volatilization and volatile solids removal. The innovative results reported in the research studies included in this Doctoral Thesis have led to an important scientific advance in terms of quantification and determination of odorous emissions derived from waste treatment. The application of new tools developed in this Thesis might contribute to mitigate the odorous impact derived from waste management and treatment, which is considered essential in current societies and tries to take the advantage of millions of tons of organic waste generated by human beings every day

Integrated Waste Management

This book reports research on policy and legal issues, anaerobic digestion of solid waste under processing aspects, industrial waste, application of GIS and LCA in waste management, and a couple of research papers relating to leachate and odour management

Biomass for Sustainability

The decarbonization of all sectors is essential in addressing the global challenge of climate change. Bioenergy can contribute to replacing our current dependence on fossil fuels and offers significant possibilities in many conventional and advanced applications, from power to heating and cooling installations. Energy systems in the building and industrial sectors can convert biomass to other usable forms of energy and improve energy performance. Moreover, bioenergy sustainability means energy can be managed for an extended period of time. Further research is needed to develop better green energy production methods and new procedures to evaluate and valorize biomass in a circular economy context. Some of the most critical bottlenecks to increase the use of bioenergy are energy conversion and management from resource to final energy. The countries where this source is strengthened can achieve security of energy supply and energy independence. In addition, biomass boilers and biomass district heating systems are interesting options to achieve nearly zero-energy buildings, contributing the needed biomass harvesting to rural development and to improve resource planning and distribution. The aim of this book is to present a comprehensive overview and in-depth technical research papers addressing recent progress in biomass-based systems and innovative applications

Wastewater irrigation and health: assessing and mitigating risk in low-income countries

Wastewater irrigation / Public health / Health hazards / Risk assessment / Epidemiology / Sewage sludge / Excreta / Diseases / Vegetables / Leaf vegetables / Economic impact / Wastewater treatment / Irrigation methods / Developing countries

Soil Water Properties of Kerangas Forest Soil after Invasion by Acacia

Soil water is important for forest ecosystems as infiltration and percolation process use soil water for plant growth. The presence of invasive Acacia species may limit the availability of soil water because these species absorb more water than native species. Hence, the objective was to investigate the effect of Acacia invasion on the soil water properties of Kerangas forests. In each invaded and non-invaded Acacia plots, holes a lysimeter was installed into the holes and used to extract soil water by direct contact to the soil. The results shows the invasion of Acacia has affected the Kerangas forest by higher absorption of water and higher fixation of nitrate

Capacity building and public awareness raising on Nitrates Directive in the countries aspiring to EU accession

The governments of the EU Member States have agreed to potentially enlarge the Union with seven South East European countries (Croatia, the Former Yugoslav Republic of Macedonia, Albania, Bosnia and Herzegovina, Montenegro, Serbia, Kosovo under UN Security Council Resolution 1244) and Turkey. However, these countries will be granted full member status only when all political, legislative and administrative requirements for membership are fulfilled. Transposition, implementation and enforcement of the EU Nitrate Directive (91/676/EC) is one of these requirements. Many policy makers, farmers and consumers from the EU accession countries perceive the Nitrate Directive as a very demanding piece of legislation with little relevance for their countries. Moreover, there is a widespread belief that the Nitrate Directive can potentially limit the competitiveness of their agricultural sector. Limited or partial information and misconceptions about the Nitrate Directive in these countries provokes fear (and sometimes anger), notably by farmers. Consequently, the adoption of the Nitrate Directive receives low political priority. In most countries aspiring to EU membership, there are no other driving forces besides EU accession pushing Governments to adopt the Nitrate Directive. Pressure exerted by health, consumer or environmental protection NGOs hardly exists. Training and education on the Nitrate Directive is poorly covered and addressed by the curricula at higher education organisations, as well as by NGO training programmes. Consequently experts from these countries do not have much opportunity to get acquainted with the Nitrate Directive. The problem persists when these people become governmental officials, extension officers, farm managers, etc., and are supposed to make policy decisions and administer the Nitrate Directive – or advise farmers and manage farms according to EU Nitrates Directive requirements. In order to remedy this problem, several international projects, financed by the Global Environmental Facility fund (administered by the World Bank or the UN Development Programme), the European Commission, and the EU Member State Governments (notably the Netherlands) have been initiated recently. The experience from these projects shows that transfer of information - capacity building and public awareness raising programmes – play a vital role in understanding the rationale behind the Nitrate Directive and in accepting the farming practices it requires. Participatory training, demonstration of nutrient management planning software, on-farm water quality testing with mobile kits, experiments using piezometers/lysimeters and field trials involving various cover crops, buffer strips, etc. accompanied with Web pages, demonstration videos, posters, leaflets, etc. have been shown to be powerful tools to demonstrate the link between water quality and (adverse) agricultural practices. The valuation (“monetisation”) of ecosystem services and environmental costs generated by the fertiliser industry and farming is a newly emerging concept that seems to be a particularly promising tool for awareness raising on the Nitrate Directive. Emerging assessments from the accession countries suggest that hidden costs (public investments and environmental costs) associated with elevated content of nitrates in water can be substantial. Making policy makers and the public at large aware of these costs and of potential savings on them by practising water friendly farming methods (e.g. organic or pastoral farming) can foster the adoption of the EU Nitrate Directive in EU candidate counties and beyond