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Extra virgin olive-oil (EVO) production is an important economic activity for several countries, especially in the Mediterranean area such as Spain, Italy, Greece and Tunisia. The two major by-products from olive oil production, solid-liquid Olive Pomace (OP) and the Olive Mill Waste Waters (OMWW), are still mainly disposed on soil, in spite of the existence of legislation which already limits this practice. The present study compares the environmental impacts associated with two different scenarios for the management of waste from olive oil production through a comparative Life Cycle Assessment (LCA). The two alternative scenarios are: (I) Anaerobic Digestion and (II) Disposal on soil. The analysis was performed through SimaPro software and the assessment of the impact categories was based on International Life Cycle Data and Cumulative Energy Demand methods. Both the scenarios are mostly related to the cultivation and harvesting phase and are highly dependent on the irrigation practice and related energy demand. Results from the present study clearly show that the waste disposal on soil causes the worst environmental performance of all the impact categories considered here. Important environmental benefits have been identified when anaerobic digestion is chosen as the final treatment. It was consequently demonstrated that anaerobic digestion should be a feasible alternative for olive mills, to produce biogas from common olive oil residues, reducing the environmental burden and adding value to the olive oil production chain. Publicado

The production of biogas from anaerobic digestion (AD) of residual agro-food biomasses represents an opportunity for alternative production of energy from renewable sources, according to the European Union legislation on renewable energy. This review provides an overview of the various aspects involved in this process with a focus on the best process conditions to be used for AD-based biogas production from residual agro-food biomasses. After a schematic description of the AD phases, the biogas plants with advanced technologies were described, pointing out the strengths and the weaknesses of the different digester technologies and indicating the main parameters and operating conditions to be monitored. Subsequently, a brief analysis of the factors affecting methane yield from manure AD was conducted and the AD of fruit and vegetables waste was examined. Particular attention was given to studies on co-digestion and pre-treatments as strategies to improve biogas yield. Finally, the selection of specific microorganisms and the genetic manipulation of anaerobic bacteria to speed up the AD process was illustrated. The open challenges concern the achievement of the highest renewable energy yields reusing agro-food waste with the lowest environmental impact and an increment of competitiveness of the agricultural sector in the perspective of a circular economy.

[ES] El presente Trabajo Fin de Máster permitirá aplicar los conocimientos adquiridos en el Máster Universitario en Tecnologías Energéticas para el Desarrollo Sostenible, así como afianzar lo aprendido en el Grado en Ingeniería de la Energía. Este proyecto, realizado en colaboración con una empresa valenciana de ingeniería de proyectos energéticos, trata de dar una solución de valorización de residuos con alto contenido orgánico. Estos residuos provienen de dos líneas diferenciadas: por un lado, hay residuos agrícolas (frutas y verduras no aptas para consumo, restos de poda, restos ganaderos ) y por otro hay una línea de restos alimentarios (restos de supermercados o de hostelería). En el proyecto se propone una planta de valorización de residuos que consiste en un pretratamiento en el que se adecúan los residuos antes mencionados para las fases posteriores; después se realiza digestión anaerobia donde se obtiene biogás. Este gas, con un 54% de metano y un 46% de CO2, puede ser valorizado en un motor de cogeneración para producir electricidad y energía térmica, y en una planta de upgrading (biometanización), donde se purifica hasta tener un 99% de metano, permitiendo su inyección a red de gas con una pureza superior a la del Gas Natural convencional. Debido a que este proceso de biometanización requiere gran cantidad de energía térmica, se incluye una caldera a biogás para aportar ese calor necesario. Por otro lado, de la digestión se obtiene un residuo líquido con alto contenido en nitrógeno que no puede ser proyectado al campo sin ser tratado previamente. Por tanto, se propone un sistema de tratamiento del digerido con el objetivo de gestionar adecuadamente este residuo., [EN] This Master's Thesis allows applying the acquired knowledge in Master's Degree in Energy Technologies for Sustainable Development, as well as to consolidate what has been learned in in Energy Engineering Degree. This project, carried out in collaboration with a Valencian engineering company for energy projects, tries to provide a solution for the recovery of waste with a high organic content. This waste comes from two differentiated lines: on the one hand, there are agricultural residues (fruits and vegetables not suitable for consumption, pruning waste, livestock remains ...) and, on the other hand, there is a line of food waste (supermarket or hospitality remains). The project proposes a waste recovery plant that consists of a pre-treatment in which the aforementioned waste is adapted for the subsequent phases; then anaerobic digestion is performed where biogas is obtained. This gas, with 54% methane and 46% CO2, can be upgraded in a cogeneration engine to produce electricity and thermal energy, and in an upgrading plant (biomethanization), where it is purified until it has 99% methane, allowing its injection into the gas network with a purity superior to that of conventional natural gas. Because this biomethanization process requires a large amount of thermal energy, a biogas boiler is included to provide that necessary heat. On the other hand, digestion produces a liquid waste with a high nitrogen content that can not be projected to the field without being previously treated. Therefore, a digested treatment system is proposed with the objective of managing adequately this residue., [CA] This Master's Thesis is designed to demonstrate the acquired knowledge in Master's Degree in Energy Technologies for Sustainable Development, as well as to consolidate what has been learned in in Energy Engineering Degree. This project, carried out in collaboration with a Valencian engineering company for energy projects, tries to provide a solution for the recovery of waste with a high organic content. This waste comes from two differentiated lines: on the one hand, there are agricultural residues (fruits and vegetables not suitable for consumption, pruning waste, livestock remains ...) and, on the other hand, there is a line of food waste (supermarket or hospitality remains). The project proposes a waste recovery plant that consists of a pre-treatment in which the aforementioned waste is adapted for the subsequent phases; then anaerobic digestion is performed where biogas is obtained. This gas, with 54% methane and 46% CO2, can be upgraded in a cogeneration engine to produce electricity and thermal energy, and in an upgrading plant (biomethanization), where it is purified until it has 99% methane, allowing its injection into the gas network with a purity superior to that of conventional natural gas. Because this biomethanization process requires a large amount of thermal energy, a biogas boiler is included to provide that necessary heat. On the other hand, digestion produces a liquid waste with a high nitrogen content that can not be projected to the field without being previously treated. Therefore, a digested treatment system is proposed with the objective of "cleaning" this residue.