Study of the effect of process parameters on the thermophilic anaerobic digestion of sewage sludge, evaluation of a thermal sludge pre-treatment and overall energetic assessment

The aim of this PhD Thesis was to study the impact of process parameters on the thermophilic anaerobic digestion of sewage sludge, to evaluate the effect of implementing a low temperature pre-treatment step, and to assess alternative processes from an energy perspective.Postprint (published version

Life cycle assessment of drinking water: comparing conventional water treatment, reverse osmosis and mineral water in glass and plastic bottles

This study evaluated the environmental impacts caused by drinking water consumption in Barcelona (Spain) using the Life Cycle Assessment (LCA) methodology. Five different scenarios were compared: 1) tap water from conventional drinking water treatment; 2) tap water from conventional drinking water treatment with reverse osmosis at the water treatment plant; 3) tap water from conventional drinking water treatment with domestic reverse osmosis; 4) mineral water in plastic bottles, and 5) mineral water in glass bottles. The functional unit was 1 m3 of water. The water treatment plant considered in scenarios 1, 2 and 3, treats around 5 m3 s-1 of surface water. The water bottling plants considered in scenarios 4 and 5 have a production capacity of 200 m3 of bottled water per day. The LCA was performed with the software SimaPro®, using the CML 2 baseline method. The results showed how tap water consumption was the most favourable alternative, while bottled water presented the worst results due to the higher raw materials and energy inputs required for bottles manufacturing, especially in the case of glass bottles. The impacts generated by domestic reverse osmosis were between 10 and 24% higher than tap water alternative depending on the impact category. It was due to the higher electricity consumption. Reverse osmosis at the water treatment plant showed impacts nearly twice as high as domestic reverse osmosis systems scenario, mainly because of the higher energy inputs. Water treated by domestic reverse osmosis equipment was the most environmentally friendly solution for the improvement of tap water organoleptic characteristics. An economic analysis showed that this solution was between 8 and 19 times cheaper than bottled water.Peer ReviewedPostprint (author's final draft

Enhancement of microalgae anaerobic digestion by thermo-alkaline pretreatment with lime (CaO)

The aim of this study was to evaluate for the first time the effect of a thermo-alkaline pretreatment with lime (CaO) on microalgae anaerobic digestion. The pretreatment was carried out by adding different CaO doses (4 and 10%) at different temperatures (room temperature (25 °C), 55 and 72 °C). The exposure time was 4 days for pretreatments at 25 °C, and 24 h for pretreatments at 55 and 72 °C. Following, a biochemical methane potential test was conducted with pretreated and untreated microalgae. According to the results, the pretreatment enhanced proteins solubilisation by 32.4% and carbohydrates solubilisation by 31.4% with the highest lime dose and temperature (10% CaO and 72 °C). Furthermore, anaerobic digestion kinetics were improved in all cases (from 0.08 to 0.14 day- 1 for untreated and pretreated microalgae, respectively). The maximum biochemical methane potential increase (25%) was achieved with 10% CaO at 72 °C, in accordance with the highest biomass solubilisation. Thus, lime pretreatment appears as a potential strategy to improve microalgae anaerobic digestion.Peer ReviewedPostprint (author's final draft

Cooperation and human development projects as bachelor, master and PhD thesis: evaluating an internship program

The Research Group on Cooperation and Human Development (GRECDH) of the Technical University of Catalonia (UPC) has long promoted Bachelor, Master and PhD Theses in the framework of sustainable energy projects in low income countries. In this way, students combine their work at UPC with tasks in these countries. The aim of this paper is to present and evaluate the program through the experience of several students who participated in sustainable energy projects in Central and South America.Postprint (published version

El paper dels sistemes naturals de tractament d'aigües residuals en la protecció dels recursos hídrics

L’aigua és un bé valuós i essencial, indispensable per a totes les formes de vida. Aquest fet, conjuntament amb la seva fragilitat enfront la contaminació, i l’escassetat d’aigua potable en moltes regions del planeta, remarca la necessitat d’una bona gestió de l’aigua, aspecte clau pel desenvolupament humà sostenible. La preservació dels recursos hídrics rau principalment en la prevenció de la seva contaminació. Malgrat tot, la creixent generació d’aigües residuals evidencia la necessitat de sistemes de tractament. El tractament de les aigües residuals és una pràctica àmpliament estesa en la majoria dels països desenvolupats. No obstant, és menys comú en comunitats petites i sobretot en països en vies de desenvolupament on, a més, la potabilització de l’aigua és escassa. Aquest fet es deu bàsicament als elevats costos de construcció i explotació de les plantes de tractament convencionals o intensives. Tècniques de tractament alternatives, com ara els sistemes naturals o extensius, es presenten en aquesta ponència com a sistemes pont per a una gestió sostenible en un futur pròxim. Els avantatges principals d’aquest sistemes són: baix o nul consum energètic, baixa generació de residus, baix impacte sonor, bona integració en el medi, simple operació i fàcil manteniment. Per contra, les principals limitacions són el requeriment de grans superfícies i el cost de construcció (lligat als moviments de terra). Degut a què el control operacional és bastant limitat, les fases de disseny i de construcció són crucials per a assegurar un bon funcionament i una bona qualitat de l’aigua depurada.Peer Reviewe

Recent achievements in the production of biogas from microalgae

The final publication is available at Springer via http://dx.doi.org/10.1007/s12649-016-9604-3Microalgae are nowadays regarded as a potential biomass feedstock to help reducing our dependence on fossil fuels for transportation, electricity and heat generation. Besides, microalgae have been widely investigated as a source of chemicals, cosmetics and health products, as well as animal and human feed. Among the cutting-edge applications of microalgae biomass, anaerobic digestion has shown promising results in terms of (bio)methane production. The interest of this process lies on its potential integration within the microalgae biorefinery concept, providing on the one hand a source of bioenergy, and on the other hand nutrients (nitrogen, phosphorus and CO2) and water for microalgae cultivation. This article reports the main findings in the field, highlighting the options to increase the (bio)methane production of microalgae (i.e. pretreatment and co-digestion) and bottlenecks of the technology. Finally, energy, economic and environmental aspects are considered.Peer ReviewedPostprint (author's final draft

Producción de biogás a partir de residuos organicos en biodigestores de bajo coste

PRODUCCIÓN DE BIOGÁS A PARTIR DE RESIDUOS ORGANICOS EN BIODIGESTORES DE BAJO COSTE Ivet Ferrer*, Enrica Uggetti**, Davide Poggio***, Enric Velo**** Grup de Recerca en Cooperació i Desenvolupament Humà C. Jordi Girona, 31 08034 - Barcelona, Spain Phone: +34 93 401 64 63 Pàgina web: http://www.upc.edu/grecdh [email protected] *, [email protected]**, [email protected]***, [email protected]**** Palabras clave: Digestión anaerobia; Biodigestor; Biogás; Energía; Fertilizante. RESUMEN La digestión anaerobia, o biodigestión, es una tecnología ampliamente difundida a escala familiar en países como China, India o Nepal. En estos sistemas los residuos orgánicos son convertidos en productos aprovechables como el biogás y el biol. En los proyectos piloto que se presentan, ubicados en Perú, hasta la fecha se han implementado alrededor de 20 biodigestores familiares, en comunidades rurales de la zona de Cusco y de Cajamarca. La mayoría se encuentran a 3000-4000 m.s.n.m, y la temperatura dentro del biodigestor oscila entre 10-23 ºC gracias a la implementación de invernaderos que permiten amortiguar las oscilaciones térmicas día-noche. Los biodigestores producen aproximadamente 0.2 m 3 biogas m -3 biodigestor día -1 , dentro del rango psicrofílico, que con biodigestores de 5 m 3 es suficiente para cocinar 3-4 h diarias, sustituyendo los combustibles tradicionales. El coste de construcción de los biodigestores (40 €/ m 3 ) seria asumible, al menos parcialmente, por familias campesinas. A nivel financiero, la instalación es más viable cuando el biogás sustituye un combustible con valor de mercado como el gas propano, resultando en un payback de 2 años y 8 meses; o bien cuando permite elaborar productos con valor añadido (quesos, yogures, mermeladas, etc.). Por otro lado, la eficacia del sistema también podría aumentar mediante la integración del biodigestor en la granja, conectándolo con la letrina y usando el biol como fertilizante para los cultivos. Estas aproximaciones son objeto de trabajos futuros. INTRODUCCIÓN Biodigestores familiares de bajo coste La digestión anaerobia, o biodigestión, es una tecnología que permite mejorar el aprovechamiento energético tradicional de la biomasa, tanto desde el punto de vista medioambiental, como social y económico [1]. Al mismo tiempo, permite una gestiónPostprint (published version

Enzymatic pretreatment of microalgae using fungal broth from Trametes versicolor and commercial laccase for improved biogas production

Coupling microalgae production to wastewater treatment can reduce the costs of microalgae production for non-food bioproducts and energy consumption for wastewater treatment. Furthermore, microalgae anaerobic digestion can be enhanced by applying pretreatment techniques. The aim of this study is to improve the biogas production from microalgal biomass grown in urban wastewater treatment systems by applying an enzymatic pretreatment with crude fungal broth and commercial laccase. To this end, the fungus Trametes versicolor was cultured, and the enzymatic activity of the culture broth analysed by measuring laccase concentration. The results showed that both the fungal broth and commercial laccase pretreatment (100 U L- 1) over an exposure time of 20 min increased the methane yield in batch tests. Indeed, the fungal broth pretreatment increased the methane yield by 74%, while commercial laccase increased the methane yield by 20% as compared to non-pretreated microalgal biomass. In this manner, laccase addition enhanced microalgal biomass anaerobic biodegradability, and addition of T. versicolor broth further improved the results. This fact may be attributed to the presence of other molecules excreted by the fungus.Peer ReviewedPostprint (author's final draft

A robust multicriteria analysis for the post-treatment of digestate from low-tech digesters. Boosting the circular bioeconomy of small-scale farms in Colombia

Low-tech digesters are sustainable technologies to produce a clean fuel (biogas), which can be used for cooking and heating. Moreover, the degradation of organic waste in the digester also produces a liquid effluent (digestate), which can be reused in agriculture as a biofertilizer. The direct application of digestate to the soil may not be either feasible due to regulations or safe due to poor quality. The study aims to apply, for the first time, a multicriteria analysis to select the most suitable solution for the post-treatment and reuse of digestate from low-tech digesters implemented in small-scale farms. The post-treatments considered are: a degassing tank, a sand filter, a vermifilter, digestate recirculation, a facultative pond, and combinations of them. Ten criteria and twenty-one sub-criteria including technical, environmental and socio-economic aspects are defined to be weighted by experts. The analysis employs triangular fuzzy numbers to consider uncertainty and increase the robustness of the results, and it is validated using three case studies in Colombia. The alternatives are designed using data collected in-situ on the design and operation of the digesters and the quality of the digestates. Results confirm the robustness of the rankings and show that vermifiltration is the best alternative for the post-treatment of digestates from low-tech digesters implemented in small-scale farms. It is due to the fact that it produces a high-quality biofertilizer, it is easy to manage and it is implemented using local materials. Other prominent alternatives are sand filtration, recirculation and a degassing tank coupled with vermifiltration.Peer ReviewedObjectius de Desenvolupament Sostenible::7 - Energia Assequible i No Contaminant::7.1 - Per a 2030, garantir l’accés universal a serveis d’energia assequibles, confiables i modernsObjectius de Desenvolupament Sostenible::7 - Energia Assequible i No ContaminantObjectius de Desenvolupament Sostenible::7 - Energia Assequible i No Contaminant::7.a - Per a 2030, augmentar la cooperació internacional per tal de facilitar l’accés a la investigació i a les tecnolo­gies energètiques no contaminants, incloses les fonts d’energia renovables, l’eficiència energètica i les tecnologies de combustibles fòssils avançades i menys contaminants, i promoure la inversió en infraestructures energètiques i tecnologies d’energia no contaminantObjectius de Desenvolupament Sostenible::7 - Energia Assequible i No Contaminant::7.b - Per a 2030, ampliar la infraestructura i millorar la tecnologia per tal d’oferir serveis d’energia moderns i sos­tenibles per a tots els països en desenvolupament, en particular els països menys avançats, els petits estats insulars en desenvolupament i els països en desenvolupament sense litoral, d’acord amb els programes de suport respectiusPostprint (author's final draft

Microalgae recycling improves biomass recovery from wastewater treatment high rate algal ponds

Microalgal biomass harvesting by inducing spontaneous flocculation (bioflocculation) sets an attractive approach, since neither chemicals nor energy are needed. Indeed, bioflocculation may be promoted by recycling part of the harvested microalgal biomass to the photobioreactor in order to increase the predominance of rapidly settling microalgae species. The aim of the present study was to improve the recovery of microalgal biomass produced in wastewater treatment high rate algal ponds (HRAPs) by recycling part of the harvested microalgal biomass. The recirculation of 2% and 10% (dry weight) of the HRAPs microalgal biomass was tested over one year in an experimental HRAP treating real urban wastewater. Results indicated that biomass recycling had a positive effect on the harvesting efficiency, obtaining higher biomass recovery in the HRAP with recycling (R-HRAP) (92–94%) than in the control HRAP without recycling (C-HRAP) (75–89%). Microalgal biomass production was similar in both systems, ranging between 3.3 and 25.8 g TSS/m2d, depending on the weather conditions. Concerning the microalgae species, Chlorella sp. was dominant overall the experimental period in both HRAPs (abundance >60%). However, when the recycling rate was increased to 10%, Chlorella sp. dominance decreased from 97.6 to 88.1%; while increasing the abundance of rapidly settling species such as Stigeoclonium sp. (16.8%, only present in the HRAP with biomass recycling) and diatoms (from 0.7 to 7.3%). Concerning the secondary treatment of the HRAPs, high removals of COD (80%) and N-NH4+ (97%) were found in both HRAPs. Moreover, by increasing the biomass recovery in the R-HRAP the effluent total suspended solids (TSS) concentration was decreased to less than 35 mg/L, meeting effluent quality requirements for discharge. This study shows that microalgal biomass recycling (10% dry weight) increases biomass recovery up to 94% by selecting the most rapidly settling microalgae species without compromising the biomass production and improving the wastewater treatment in terms of TSS removal.Peer ReviewedPostprint (author's final draft