La indústria del curtit, menys contaminant

Els processos productius que s'usen en la indústria del curtit generen una elevada quantitat de residus sòlids i líquids. Entre els primers destaca sobretot el pèl que s'extrau de la pell dels animals per transformar-la en cuir. Tanmateix, aquest material pot convertir-se, degut a la seva riquesa en matèria orgànica, en compost beneficiós per al sòl, mitjançant el procés de compostatge. Investigadors de la UAB ho han demostrat en un experiment realitzat a escala industrial.Los procesos productivos que se usan en la industria del curtidogeneran una elevada cantidad de residuos sólidos y líquidos. Entre losprimeros destaca sobre todo el pelo que se extrae de la piel de losanimales para transformarla en cuero. Sin embargo, este material puedeconvertirse debido a su riqueza en materia orgánica, a través delproceso de compostaje. Investigadores de la UAB lo han demostrado enun experimento realizado a escala industrial

Impacte ambiental del tractament de residus per compostatge

El compostatge és una tècnica viable i molt estesa al nostre país per tractar la fracció orgànica dels residus municipals. Com qualsevol procés industrial, el compostatge porta associada una sèrie d'impactes ambientals, com ara els derivats de les emissions gasoses i del consum de recursos. S'han determinat els impactes de dues instal·lacions reals de compostatge a Catalunya que tracten els residus urbans utilitzant com a eina l'anàlisi de cicle de vida: una d'aquestes instal·lacions és una planta de túnels amb equips per al tractament de les emissions gasoses i, l'altra, una de piles airejades completament oberta.El compostaje es una técnica viable y muy extendida en nuestro pais para tratar la fracción orgánica de los residuos municipales. Como cualquier proceso industrial, el compostaje conlleva una serie de impactos ambientales, como los derivados de las emisiones gaseosas y del consumo de recursos. Se han determinado los impactos asociados a dos instalaciones reales de compostaje en Cataluña que tratan los residuos urbanos utilizando como herramienta el análisis de ciclo de vida: una de estas instalaciones es una planta de túneles con equipos para el tratamiento de las emisiones gaseosas y, la otra, una de las pilas aireadas completamente abierta

Enzymatic hydrolysis of the organic fraction of municipal solid waste : Optimization and valorization of the solid fraction for Bacillus thuringiensis biopesticide production through solid-state fermentation

Altres ajuts: Acord transformatiu CRUE-CSICAltres ajuts: Generalitat de Catalunya pre-doctoral grant (DI 7, 2019)To reach a more sustainable society, the implementation of a circular economy perspective in municipal waste management becomes essential. In this work, the enzymatic hydrolysis of source-separated organic fraction of municipal solid waste (OFMSW) has been optimized as a sugar-releasing step. A liquid sugar concentrate, with a maximum reducing sugar concentration of 50.56 g L, and a solid hydrolyzed fraction were obtained. The effect of the harshness of the hydrolysis conditions was evaluated on the performance of the resulting solid fraction as a substrate for Bacillus thuringiensis biopesticide production through solid-state fermentation. A production of 3.9 × 10 viable cells g dry matter with a 33% sporulation ratio was achieved for milder hydrolysis conditions, highlighting the potential of the solid fraction of hydrolysis as a substrate of SSF processes. The proposed valorization pathway for the OFMSW results in a sugar concentrate with potential for fermentative processes and a fermented solid containing biopesticides from Bacillus thuringiensis

Biodegradation of animal fats in a co-composting process with wastewater sludge

A composting process was proposed as an effective technology for the biodegradation of fats in a proportion of 40-50%. Anaerobically digested sludge was used as co-substrate for animal fats to balance the C/N ratio of the composting mixture and to provide additional biodegradable organic matter and active biomass. Two different strategies were studied: static pile and dynamic turned pile. Air-filled porosity was initially adjusted to 40% for both experiments. It was observed that non-turned strategy increases the formation of material agglomerates which derived in a non-homogeneous fat distribution, the development of filamentous fungi, and a considerable increase in the amount of leachate generated. Turning the composting material resulted in the best results for composting fat-enriched wastes, preventing the formation of agglomerates. An effective biodegradation up to 92% of the fats was observed under these conditions. Besides, the addition of fats increased significantly the duration of the thermophilic period of the composting process

Factors affecting air pycnometer performance for its use in the composting process

Air filled porosity (AFP) is a crucial factor in composting to guarantee aerobic conditions inside the composting matrix. Among the different methods proposed to measure AFP in composting processes, air pycnometry is defined as the most adequate. There is a lack of a standard methodology for air pycnometry utilization for AFP determination in heterogeneous samples as those from composting materials. Air pycnometers currently used for this purpose are custom made instruments operating under different conditions (sample volume, initial pressure, etc.). All factors affecting air pycnometry accuracy in the composting process are related to the proper maintenance and handling of the air pycnometer and the composting sample. In this study, AFP measurements have been performed in more than 50 samples of a wide range of composting materials using two different custom made pycnometers, one of them coupled to a composting reactor allowing in situ AFP measurement. While temperature variation during AFP measurement has been discarded as an error source, the determination of the sample volume has been found to be a significant factor affecting the air filled porosity calculation. Regarding the initial pressure to use, a compromise between accuracy and practicality has to be established for each pycnometer design as AFP values obtained with diverse initial pressures (from 200 to 500 kPa gauge pressure) were found to present no statistical differences. An initial pressure in the range of 300-500 kPa (gauge pressure) is recommended. In conclusion, there is a need for a standard methodology for AFP determination or prediction at industrial scale. A complete procedure for air filled porosity determination by air pycnometry is also presented in this work

Bacillus thuringiensis Production Through Solid‑State FermentationUsing Organic Fraction of Municipal Solid Waste (OFMSW) EnzymaticHydrolysate

Altres ajuts: acords transformatius de la UABThis paper aims to explore an alternative pathway to valorize the organic fraction of municipal solid waste. It is based on the use of enzymatic hydrolysis to obtain a sugar-rich fraction with the potential for liquid fermentative processes and a partially hydrolyzed solid that is evaluated as a substrate for solid-state fermentation. Different strategies to modify the pH of the solid substrate to reach a neutral pH, suitable for the growth of biopesticide producer Bacillus thuringiensis, have been explored. The use of alkaline cosubstrates was evaluated on two different scales and temperature was assessed as a preliminary indicator of the scale-up viability of the process strategy. By ensuring a proper pH throughout the process, the growth and sporulation of Bacillus thuringiensis were achieved. The best cosubstrates and mixing ratios were 50% of digested sewage sludge and 25% of digested organic fraction of municipal solid waste, which led to a spore concentration of 1.1 × 109 spores g−1 of dry matter and 6.4 × 108 spores g−1 of dry matter, respectively. Overall, a reproducible and flexible solid-state fermentation process has been achieved for hydrolyzed organic municipal waste based on the use of alkaline urban wastes as cosubstrates. This valorization pathway fits with the concept of urban biorefineries

Residus més biodegradables

El tractament de residus sòlids orgànics per obtenir compost -esmena orgànica estable i aplicable al sòl- és un procés d'àmplia aplicació, però complex. Aconseguir que un residu sigui compostat amb èxit, dependrà de que aquest tingui certes característiques químiques i biològiques. Per això, quan aquestes no hi són, existeix la possibilitat de compensar-les mitjançant el cocompostatge. Aquest es basa en l'addició de cosubstrats al residu original, per tal que aquest superi les seves deficiències de partida i pugui ser tractat posteriorment. Seguint aquesta línia, s'han dut a terme una sèrie de proves en el laboratori afegint proteïna, greix i cel·lulosa per separat a fangs de depuradora d'aigües residuals urbanes. Els resultats han estat força positius, tant pel que fa al desenvolupament del procés, com per la conservació del nitrogen en el producte final. Els cosubstrats utilitzats es troben en un nombre important de residus orgànics, especialment aquells que provenen de la indústria agroalimentària. El seu tractament mitjançant compostatge obre una excel·lent via de valorització.El tratamiento de residuos sólidos orgánicos para obtener compuesto - enmienda orgánica estable y aplicable al suelo- es un proceso de amplia aplicación, pero complejo. Conseguir que un residuo sea compostado con éxito, dependerá de que éste tenga ciertas características químicas y biológicas. Por eso, cuando éstas no están, existe la posibilidad de compensarlas mediante el cocompostaje. Éste se basa en la adición de cosustratos en el residuo original, a fin de que éste supere sus deficiencias de partida y pueda ser tratado posteriormente. Siguiendo esta línea, se han llevado a cabo una serie de pruebas en el laboratorio añadiendo proteína, grasa y celulosa por separado a barros de depuradora de aguas residuales urbanas. Los resultados han sido bastante positivos, tanto con respecto al desarrollo del proceso, como por la conservación del nitrógeno en el producto final. Los cosustratos utilizados se encuentran en un número importante de residuos orgánicos, especialmente aquéllos que provienen de la industria agroalimentaria. Su tratamiento mediante compostaje abre una excelente vía de valorización.The treatment of organic solid waste to obtain compost - which can be used as soil conditioner or fertilizer - is a complex process. However, certain physico-chemical and biological characteristics are required in a waste to be successfully composted. When these characteristics are not present, there is the possibility of compensating them through cocomposting. This technique consists in adding a cosubstrate to the original waste to make up for its original deficiencies and facilitate its treatment by composting. Cocomposting was tested with a series of laboratory trials in which protein, fats and cellulose were added to sewage sludge separately. The results were quite positive not only due to enhancement of the composting process evolution but also for the increase in nitrogen conservation in the final product. The cosubstrates used can be found in different organic wastes specially those from the food industry. The treatment of these wastes though composting offers an excellent opportunity for their valorization

Monitoring the biological activity of the composting process : oxygen uptake rate (OUR), respirometric index (RI) and respiratory quotient (RQ)

Composting of several organic wastes of different chemical composition (source-separated organic fraction of municipal solid waste, dewatered raw sludge, dewatered anaerobically digested sludge and paper sludge) was carried out under controlled conditions to study the suitability of different biological indexes (oxygen uptake rate, respirometric index, and respiratory quotient) to monitor the biological activity of the composting process. Among the indexes tested, oxygen uptake rate (also referred to as dynamic respirometric index) provided the most reliable values of microbial activity in a compost environment. On the other hand, values of the static respirometric index measured at process temperature, especially in the early stages of the composting process, were significantly lower than those of the dynamic index, which was probably due to oxygen diffusion limitations present in static systems. Both static and dynamic indexes were similar during the maturation phase. Static respirometric index measured at 37°C should not be used with samples obtained during the thermophilic phase, since it resulted in an underestimation of the respiration values. Respiratory quotient presented only slight variations when changing the process temperature or the waste considered, and its use should be restricted to ensure aerobic conditions in the composting matrix

Influence of different co-substrates biochemical composition on raw sludge co-composting

The influence of biochemical composition of different co-substrates added to raw sludge during co-composting process was studied. The physical properties of the composting mass and their influence on the biological activity were also investigated. Three treatments composed of mixtures of raw sludge and co-substrate (commercial fats, protein, and cellulose) were carried out and compared to a control composed of raw sludge. Mixture conditioning was performed on the basis on air filled porosity (40%). The results obtained in the co-composting processes reflected a higher biological activity and higher degradation percentages of dry and organic matter when compared with control. Higher temperatures (60, 67 and 62°C for fats, protein and cellulose, respectively) were also achieved in all co-composting experiments as compared to the control test (55°C). Biological activity was measured using both Static and Dynamic Respiration Indices obtaining higher values in co-composting experiments compared to the control test. Fats content reduction was higher (66%) at higher fats content in the initial mixture (10.6%). The addition of fats seems also to promote the degradation of cellulose and lignin. Co-composting experiments with fats and cellulose presented higher initial C/N ratio and lower nitrogen losses, 27.5 and 34.2% compared to 40% for raw sludge. It has been demonstrated that the addition of an adequate co-substrate to raw sludge leads to a higher degradation percentages of the different biochemical fractions and higher nitrogen conservation

Optimal bulking agent particle size and usage for heat retention and disinfection in domestic wastewater sludge composting

Composting of two types of sludge produced in wastewater treatment plants, raw sludge (RS) and anaerobically digested sludge (ADS), has been systematically studied by means of the experimental design technique. The results have been analyzed using a full factorial experimental design in order to determine the optimal conditions for composting such sludges in terms of bulking agent particle size and bulking agent:sludge volumetric ratio, two of the key parameters to ensure an optimal performance of the composting process. The objective function selected was a simulated death kinetics of Salmonella, which was chosen as a model pathogen microorganism to represent the disinfection of the material. For both types of sludge, optimal values were found at 5 mm bulking agent particle size and 1:1 bulking agent:sludge volumetric ratio when a Gaussian function was fitted to the experimental data. Pilot scale experiments using optimal values obtained were successfully undertaken and confirmed a full disinfection of the sludge by means of the composting process. A mathematical model to simulate the disinfection performance of a composting material is presented. The model can be applied to simulate the disinfection performance of a given pathogen