El digestat : de residu a recurs en un paradigma descentralitzat

El digestat és el material residual que es genera a partir de la digestió anaeròbia, un procés utilitzat per obtenir energia de la matèria orgànica dels residus urbans. Normalment, sol ser utilitzat com a fertilitzant. Tanmateix, l'estudi presentat pel Grup de Recerca GICOM ha analitzat quines utilitats podria tenir el digestat com a matèria primera en obtenció de bioproductes. Han conclòs que aquest es podria utilitzar com a un biopesticida de baix impacte ambiental i amb gran efectivitat, gràcies a l'acció del bacteri Bacillus thuringiensis.El digestato es el material residual que se genera a partir de la digestión anaeróbica, un proceso utilizado para obtener energía de la materia orgánica de los residuos urbanos. Normalmente, suele ser utilitzado como fertilizante. Sin embargo, el estudio presentado por el Grupo de Investigación GICOM ha analizado las utilidades que podría tener el digestato como materia prima en la obtención de bioproductos. Han concluido que este se podría utilizar como un biopesticida de bajo impacto ambiental y con gran eficiencia, gracias a la acción de la bacteria Bacillus thuringiensis

El bioassecatge com a opció per al tractament dels fangs de depuradora

En els últims anys s'ha produït un considerable augment de la instal·lació de plantes depuradores per al tractament d'aigües residuals, beneficiós pels nostres rius i mars. Però els investigadors estan treballant per reduir encara més el baix impacte ambiental d'aquest procés i valorant alternatives per al tractament dels fangs que es generen, més enllà de la seva conversió en compostatge. En aquest estudi, s'analitzen els pros i contres del bioassecatge, una altra manera emergent d'aprofitar els fangs, en aquest cas per produir un biocombustible similar a la biomassa.En los últimos años se ha producido un considerable aumento de la instalación de plantas depuradoras para el tratamiento de aguas residuales, beneficioso para nuestros ríos y mares. Pero los investigadores están trabajando para reducir aún más el bajo impacto ambiental de este proceso y valorando alternativas para el tratamiento de los lodos que se generan, más allá de su conversión en compostaje. En este estudio, se analizan los pros y contras del biosecado, otra manera emergente de aprovechar los lodos, en este caso para producir un biocombustible similar a la biomasa

Gestió més sostenible de residus : el temps de compostatge influeix sobre l'estabilitat del compost i les seves emissions gasoses

Per tal de gestionar els residus d'una manera sostenible, l'objectiu d'aquest treball és l'optimització del compostatge de fangs d'estacions depuradores d'aigües urbanes residuals en una planta de compostatge. S'ha avaluat com l'efecte del temps en les diferents fases del procés de compostatge afecta l'estabilitat del compost final i a la quantitat d'emissions d'amoníac que emet. Els resultats obtinguts podrien suposar una millora dels costos d'explotació i una disminució de la contaminació en un futur.Con el fin de gestionar los residuos de una manera sostenible, el objetivo de este trabajo es la optimización del compostaje de lodos de estaciones depuradoras de aguas urbanas residuales en una planta de compostaje. Se ha evaluado como el efecto del tiempo en las diferentes fases del proceso de compostaje afecta la estabilidad del compost final y la cantidad de emisiones de amoníaco que emite. Los resultados obtenidos podrían suponer una posible mejora de los costes de explotación y una disminución de la contaminación en un futuro

Compostatge de residus alimentaris : estat i reptes

Un article publicat pel Grup d'Investigació en Compostatge (GICOM) de la UAB ha fet una compilació tècnica de la situació actual del compostatge de residus generals de les llars, ressaltant aquells aspectes en els quals es necessiten més investigació i tecnologia per reforçar aquesta eina consolidada a Europa.Un artículo publicado por el Grupo de Investigación del Compostaje (GICOM) de la UAB ha hecho una compilación técnica de la situación actual del compostaje de residuos generales de los hogares, resaltando aquellos aspectos en los que se necesitan más investigación y tecnología para reforzar esta herramienta consolidada en Europa

A new control strategy for composting process based on the oxygen uptake rate

Up to now different control strategies to supply the oxygen requirements to the composting process have been studied. All of them seek for the biological activity optimization. In general, temperature and oxygen content are identified as the key parameters to assess the microbial activity. For this reason, the most favorable range of temperature and oxygen content for composting has frequently been studied and used as controllers' set points. On contrast, no previous works have studied the feasibility of oxygen supply according to the biological activity during the process, measured as oxygen uptake rate. In this field, a new automatic composting controller has been developed using the oxygen uptake rate measure as the measured variable. After setting up and to start-up this new technique, two pilot composting trials were undertaken with municipal solid waste. Oxygen, temperature and cyclic controllers were also implemented and tested in the composting of the same waste, in order to compare the results and to determine what the optimum system is. The four systems studied had similar temperature profiles, whereas except for the new controller, the oxygen content was constantly oscillating during most part of the process due to severe airflow changes. Through all the most relevant parameters determined, it can be observed that the new controller offers the most optimum system performance, since with low energy consumption a higher total oxygen uptake is achieved and, in consequence, the most stable end-product is obtained. Hence, the oxygen uptake rate controller is recommended for the airflow regulation in composting systems with automatic control

Short-time estimation of biogas and methane potentials from municipal solid wastes

Biogas (GB) and methane (BMP) potentials are important parameters for the energy potential of the anaerobic digestion of municipal solid wastes (MSW) and to design full-scale facilities. However, no standard protocol has been defined for this measure. Several samples of mixed MSW and the source-selected organic fraction of municipal solid waste (OFMSW) obtained at different stages of their mechanical-biological treatment were analyzed. GB and BMP values obtained at different times were correlated. Biogas potentials calculated at 3, 4, 5, 6, 7, 14, 21, 50 and 100 days correlated well for the OFMSW samples. In the case of the MSW samples, only GB values obtained at times of 14 or more days correlated well with the ultimate biogas production (considered at 100 days). The biogas potential analyzed at 21 days (as proposed in some standard methods) accounted for 77% of the total biogas potential in OFMSW samples and for 71% in the MSW samples. These results are useful for the correct design and operation of anaerobic digestion plants in terms of retention time estimation and expected biogas and methane production

Anaerobic co-digestion of the organic fraction of municipal solid waste with several pure organic co-substrates

A strategy to improve the operation of working anaerobic digesters treating the organic fraction of municipal solid wastes (OFMSW) to increase the biogas production is studied. It consists of increasing the organic loading rate of the digesters by adding extra organic matter from some problematic organic wastes. Vegetable oil (VO), animal fats (AF), cellulose and protein (protein) were used as pure co-substrates and the co-digestion anaerobic process was analysed in terms of the ultimate methane production, the methane production rate and the hydraulic residence time. The analysis of methane or biogas production led to different conclusions when expressing this parameter on a volatile solids basis or on a reactor volume basis. The need for a combined analysis is highlighted. In addition a new model to predict the biodegradability rate and evaluating the organic matter fraction susceptible to biodegradation was developed and proved to be suitable for assessing anaerobic digestion processes. All four co-substrates used led to some operative improvements. Vegetable oil is the most suitable co-substrate to be anaerobically digested with the OFMSW since all the parameters evaluated were greatly improved compared to the OFMSW digestion

Solid-state fermentation of soybean residues for bioflocculant production in a pilot-scale bioreactor system

An innovative approach using soybean residues for the production of bioflocculants through solid-state fermentation was carried out in 4.5 L near-to-adiabatic bioreactors at pilot-scale level. An added inoculum of the strain Bacillus subtilis UPMB13 was tested in comparison with control reactors without any inoculation after the thermophilic phase of the fermentation. The flocculating performances of the extracted bioflocculants were tested on kaolin suspensions, and crude bioflocculants were obtained from 20 g of fermented substrate through ethanol precipitation. The production of bioflocculants was observed to be higher during the death phase of microbial growth. The bioflocculants were observed to be granular in nature and consisted of hydroxyl, carboxyl and methoxyl groups that aid in their flocculating performance. The results show the vast potential of the idea of using wastes to produce bioactive materials that can replace the current dependence on chemicals, for future prospect in water treatment applications

Uniaxial and shear deformations in smectic-C main-chain liquid-crystalline elastomers

ABSTRACT: A novel cross-linked smectic-C main-chain liquid-crystalline elastomer has been synthesized by polycondensation of vinyloxy-terminated mesogens, tetramethyldisiloxane and pentamethylpentaoxapentasilecane. The introduction of the functional vinyloxy group allows the synthesis of well-defined networks having low soluble content and good mechanical properties due to elimination of side reactions as in the case of vinyl groups. Networks having a macroscopic uniformly ordered director and a conical distribution of the smectic layer normal with respect to the director are mechanically deformed by uniaxial and shear deformations. Under uniaxial deformations two processes were observed: parallel to the director the mechanical field directly couples to the smectic tilt angle while perpendicular to the director a reorientation process takes place. A shear deformation parallel and perpendicular to the director causes a uniform layer orientation and the network exhibits a smectic-C monodomain phase having a macroscopic uniform director and layer orientation. This process is reversible for shear deformation perpendicular and irreversible by applying the shear force parallel to the director

Thermal and mechanical properties of new main-chain liquid-crystalline elastomers

New Main-Chain Liquid-Crystalline Elastomers (MCLCEs) were synthesised based on reacting vinyloxy-terminated mesogens under hydrosilylation conditions with a flexible crosslinker. These main-chain systems showed smectic and nematic mesophases and their anisotropic properties were mechanically and thermally analysed as function of the crosslinking density. Due to the suitable chemistry used in this work low crosslinking densities have been achieved (2.5 mol-%) with low soluble content (5%). For the first time, the degree of crosslinking could be adjusted and nematic or smectic MCLCEs with tuneable thermal and mechanical properties were obtained