Innovative approaches for enhancing the cost-efficiency of biological methane abatement

Methane (CH4), which is considered the second most important greenhouse gas (GHG), represents nowadays 18 % of the total EU-28 GHG emissions and possesses a global warming potential 25 times higher than that of CO2 (in a 100 yr horizon). The methane produced during the anaerobic digestion of organic waste (wastewater and organic solid waste) can be collected and combusted for the generation of electricity and/or heat, thus replacing fossil fuels. However, methane can be only used for energy generation when its concentration in the emission is higher than 20 %. Unfortunately, more than 56 % of the anthropogenic CH4 emissions contain CH4 concentrations below 5 %, which significantly limits the implementation of energy recovery-based treatment technologies. Therefore, cost-efficient abatement methods to mitigate the pernicious environmental effects of residual CH4 emissions are required.Departamento de Ingeniería Química y Tecnología del Medio AmbienteDoctorado en Ingeniería Química y Ambienta

Liderazgo político, comunicación y percepción ciudadana. El caso de Mariano Rajoy (2011-2016).

Este artículo presenta la evolución de la opinión pública de la sociedad española aplicada al caso de Mariano Rajoy. A través de encuestas preelectorales y poselectorales del Centro de Investigaciones Sociológicas (CIS), se estudian los cambios en la valoración del líder, así como también la variación del interés por la política y las campañas electorales en relación a las elecciones generales de 2011 y 2016.Departamento de Historia Moderna, Contemporánea y de América, Periodismo y Comunicación Audiovisual y PublicidadGrado en Periodism

The effect of temperature during culture enrichment on methanotrophic polyhydroxyalkanoate production

Producción CientíficaClimate change and plastic pollution are likely the most relevant environmental problems of the 21st Century. Thus, one of the most promising solutions to remedy both environmental problems simultaneously is the bioconversion of greenhouse gases, such as methane (CH4), into bioplastics (PHAs). However, the optimization of this bioconversion platform is still required to turn CH4 biotransformation into a cost-effective and cost-competitive process. In this context, the research presented here aimed at elucidating the best temperature culture conditions to enhance both PHA accumulation and methane degradation. Six different enrichments were carried out at 25, 30 and 37 °C using different inocula and methane as the only energy and carbon source. CH4 biodegradation rates, specific growth rates, PHA accumulations and the community structure were characterized. Higher temperatures (30 and 37 °C) increased the PHAs accumulation up to 30% regardless of the inoculum. Moreover, Methylocystis became the dominant genus (∼30% of the total population) regardless of the temperature and inoculum used. This research demonstrated for the first time the fundamental role of temperature in increasing both the accumulation of PHAs and methane abatement during the enrichment of PHA cell-factories from methane, thus enhancing the cost-effectiveness of the process.Ministerio de Economía, Industria y Competitividad, TheEuropean FEDER program and the European Commission (CTM2015-73228-JIN, H2020-MSCA-IF-2016: CH4BioVal-GA:750126 and Red NOVEDAR)

Indoor air VOCs biofiltration by bioactive coating packed bed bioreactors

Producción CientíficaBioactive coatings are envisaged as a promising biotechnology to tackle the emerging problem of indoor air pollution. This solution could cope with the low concentrations, the wide range of compounds and the hydrophobicity of some indoor air VOCs, which are the most important bottlenecks regarding the implementation of conventional biotechnologies for indoor air treatment. A bioactive coating-based bioreactor was tested in this study for the abatement of different VOCs (n-hexane, toluene and α-pinene) at different empty bed residence times (EBRT) and inlet VOC concentrations. The performance of this reactor was compared with a conventional biofilm-based bioreactor operated with the same microbial inoculum. After an acclimation period, the bioactive coating-based bioreactor achieved abatements of over 50% for hexane, 80% for toluene and 70% for pinene at EBRTs of 112–56 s and inlet concentrations of 9–15 mg m−3. These results were about 25, 10 and 20% lower than the highest removals recorded in the biofilm-based bioreactor. Both bioreactors experienced a decrease in VOC abatement by ∼25% for hexane, 45% for toluene and 40% for pinene, after reducing the EBRT to 28 s. When inlet VOC concentrations were progressively reduced, VOC abatement efficiencies did not improve. This fact suggested that low EBRTs and low inlet VOCs concentration hindered indoor air pollutant abatement as a result of a limited mass transfer and bioavailability. Metagenomic analyses showed that process operation with toluene, hexane and pinene as the only carbon and energy sources favored an enriched bacterial community represented by the genera Devosia, Mesorhizobium, Sphingobacterium and Mycobacterium, regardless of the bioreactor configuration. Bioactive coatings were used in this work as packing material of a conventional bioreactor, achieving satisfactory VOC abatement similar to a conventional bioreactor.Ministerio de Ciencia e Innovación y Ministerio de Universidades [project RTI2018-0-096441-B-I00]Junta de Castilla y León - EU-FEDER [grant number CLU 2017–09, CL-EI-2021-07 y UIC 315]Junta de Castilla y León y Fondo Social Europeo (PhD grant BDNS 487971)Comisión Europea-H2020-MSCA–IF–2019 (ENHANCEMENT, ref. 897284

Assessment of the mass transfer strategy and the role of the active bacterial population on the biological degradation of siloxanes

Producción CientíficaUpgrading of biogas to remove siloxanes is mandatory to meet the standards required for its use as a substitute of fossil fuels. The biological degradation of these pollutants is a low cost and environmental friendly alternative to conventional techniques, albeit certain limitations, such as the low solubility of siloxanes, still hinder its application. In the present work, two parameters were optimized in aerobic and anoxic two-phase biotrickling filters (TP-BTF): the trickling liquid velocity (TLV) and the internal gas recirculation, with the aim of improving siloxanes biological removal. The results obtained showed that the increase in TLV from 2 to 10 m h−1 resulted in higher removal efficiency (RE) under both anoxic and aerobic conditions, reaching maximum values of 55 and 47%, respectively. This effect was more significant for the linear siloxanes. On the contrary, a further increase in the TLV to 20 m h−1 together with the implementation of internal gas recirculation caused an excessive turbulence in the liquid side, detaching the biofilm and having a negative effect for the RE. The cyclic siloxanes were more effectively eliminated along the process (maximum REs of 75% were recorded for decamethylcyclopentasiloxane (D5)), but the studied system modifications exerted a minor effect on their RE. The active bacterial population involved in siloxanes degradation (studied throughout RNA extraction and sequencing) was dominated by the clade Acidithiobacillacea KCM-B-112 and the genus Parvibaculum in aerobic conditions, while the members of the family Phyllobacteriacea and the genera Nocardia and Baekduia dominated in anoxic conditions.European Union’s Horizon 2020 research and innovation program under grant agreement No 745785Junta de Castilla León - EU-FEDER (CLU 2017-09, CL-EI-2021-07 y UIC 315)European Commission-H2020- MSCA-IF-2019 grant (ENHANCEMENT, ref. 897284

Comparative evaluation of bacterial and fungal removal of indoor and industrial polluted air using suspended and packed bed bioreactors

Producción CientíficaThe abatement of indoor volatile organic compounds (VOCs) represents a major challenge due to their environmental risk, wide nature and concentration variability. Biotechnologies represent a cost-effective, robust and sustainable platform for the treatment of hazardous VOCs at low and fluctuating concentrations. However, they have been scarcely implemented for indoor air purification. Thus, little is known about the influence of the reactor configuration or the VOC nature and concentration variability on the removal, resilience and the microbial population of bioreactor configurations susceptible to be implemented, both in indoors and industrial environments. The present study aims at comparing the removal performance of four VOCs with different hydrophobicity and molecular structure -acetone, n-hexane, α-pinene and toluene-at two inlet concentrations (5 and 400 mg m−3), which mimics the concentrations of contaminated indoor and industrial air. To this aim a stirred tank, flat biofilm and latex-based biocoated flat bioreactor were comparatively evaluated. The results demonstrated the superior performance of the stirred tank reactor for the removal of hydrophilic VOCs at high inlet concentrations, which achieved removals >99% for acetone and toluene. At low concentrations, the removal efficiencies of acetone, toluene and α-pinene were >97% regardless of the bioreactor configuration tested. The most hydrophobic gas, n-hexane, was more efficiently removed in the flat biofilm reactor without latex. The microbial community analyses showed that the presence of VOCs as the only carbon and energy source didn't promote the growth of dominant bacterial members and the populations independently evolved in each reactor configuration and operation mode. The fungal population was more diverse in the biofilm-based bioreactors, although, it was mainly dominated by uncultured fungi from the phylum Cryptomycota.Ministerio de Ciencia, Innovación y Universidades (project RTI2018-0-096441-B-I00)Junta de Castilla y Leon - Fondo Europeo de Desarrollo Regional (grants CLU 2017-09, and CL-EI-2021-07

Biofiltration based on bioactive coatings for the abatement of indoor air VOCs

Producción CientíficaBiotechnologies are a feasible alternative for indoor air pollutant abatement. Among biotechnologies, bioactive coatings consist of microorganisms embedded in polymeric matrices, allowing a direct contact between microorganisms and gas pollutants, thus enhancing their abatement. Three bioreactors (BR1, BR2 and BR3) were inoculated with a VOC-degrading enriched culture, a latex bioactive coating with the VOC-degrading enriched culture, and a latex bioactive coating with fresh activated sludge. The influence of empty bed residence time (EBRT) and inlet concentrations on the removal of toluene, α-pinene and n-hexane was assessed. BR1 and BR2 achieved steady-state toluene and pinene removals >90% down to 30 s. BR3 lower removals could be attributed to the lack of acclimation of activated sludge. When inlet concentrations were progressively reduced to 80% in BR1 and BR2, but only to 64.2% in BR3. Pinene removals reached 90.9% in BR1, and >70% in BR2 and BR3. The bacterial population was dominated by Rhodococcus, Mycobacterium, Devosia and Rhodobacteraceae members in BR1 and BR2. No significant and robust hexane removal was observed regardless of the inoculum or operational conditions, probably due to mass transfer limitations, which entailed a low dominance of organisms with this metabolic capability.Ministerio de Ciencia, Innovación y Universidades (project RTI2018-0-096441-B-I00)Junta de Castilla y León y EU-FEDER (program grant number CLU 2017–09, CL-EI-2021-07 and UIC 315)European Commission-H2020-MSCA–IF–2019 grant (ENHANCEMENT, ref. 897284

Influence of the gas-liquid flow configuration in the absorption column on photosynthetic biogas upgrading in algal-bacterial photobioreactors

Producción CientíficaThe potential of an algal-bacterial system consisting of a high rate algal pond (HRAP) interconnected to an absorption column (AC) via recirculation of the cultivation broth for the upgrading of biogas and digestate was investigated. The influence of the gas-liquid flow configuration in the AC on the photosynthetic biogas upgrading process was assessed. AC operation in a co-current configuration enabled to maintain a biomass productivity of 15 g m−2 d−1, while during counter-current operation biomass productivity decreased to 8.7 ± 0.5 g m−2 d−1 as a result of trace metal limitation. A bio-methane composition complying with most international regulatory limits for injection into natural gas grids was obtained regardless of the gas-liquid flow configuration. Furthermore, the influence of the recycling liquid to biogas flowrate (L/G) ratio on bio-methane quality was assessed under both operational configurations obtaining the best composition at an L/G ratio of 0.5 and co-current flow operation.Ministerio de Economía, Industria y Competitividad (Project CTM2015-70442-R and Red NOVEDAR

Ectoine bio-milking in methanotrophs: A step further towards methane-based bio-refineries into high added-value products

Producción CientíficaThis communication showed for the first time that the methanotrophic strain Methylomicrobium alcaliphilum 20Z (M. alcaliphilum 20Z) can efficiently synthesize and excrete (through a tailored bio-milking process) ectoine under continuous mode using methane (CH4) as the sole energy and carbon source. First, three consecutive 50 h fed batch fermentations consisting of alternating high salinity (6% NaCl for 24 h) and low salinity (0% NaCl for 24 h) cultivation stages were carried out in triplicate to determine the influence of sudden modifications in media salinity on ectoine synthesis and excretion. The results demonstrated that M. alcaliphilum 20Z exhibited a rapid response to osmotic shocks, which resulted in the release of the accumulated ectoine under hyposmotic shocks and the immediate uptake of the previously excreted ectoine during hyperosmotic shocks. A second experiment was carried out under continuous cultivation mode in two sequential stirred tank reactors operated at NaCl concentrations of 0 and 6%. Cells exhibited a constant intra-cellular ectoine concentration of 70.4 ± 14.3 mg g biomass−1 along the entire operation period when cultivated at a NaCl concentration of 6%. The centrifugation of the cultivation broth followed by a hyposmotic shock resulted in the excretion of ∼70% of the total intra-cellular ectoine. In brief, this research shows the feasibility of the continuous bioconversion of diluted CH4 emissions into high added-value products such as ectoine, which can turn greenhouse gas (GHG) abatement into a sustainable and profitable process.Ministerio de Economía, Industria y Competitividad (Project CTM2015-70442-R and Red NOVEDAR

Continuous abatement of methane coupled with ectoine production by Methylomicrobium alcaliphilum 20Z in stirred tank reactors: A step further towards greenhouse gas biorefineries

This study demonstrates for the first time the feasibility of producing ectoine (a high added value osmoprotectant intensively used in the cosmetic industry) during the continuous abatement of diluted emissions of methane by Methylomicrobium alcaliphilum 20Z in stirred tank reactors under non-sterile conditions. An increase in NaCl concentration in the cultivation broth from 3 to 6% increased the intra-cellular ectoine yield by a factor of 2 (from 16.5 to 37.4 mg ectoine (g biomass)−1), while high stirring rates (600 rpm) entailed a detrimental cellular stress and 3 times lower ectoine yields (5.6 mg ectoine (g biomass)−1) compared to process operation at 300 rpm. An increase in Cu2+ concentration from 0.05 to 25 μM enhanced methane abatement by a factor of 2 (up to elimination capacities of 24.5 g m−3 h−1), did not enhance intra-cellular ectoine production but promoted the excretion to the cultivation broth of 20% of the total ectoine synthesized regardless of the NaCl concentration and stirring rate. The results obtained by culture hybridization with the specific probe Mγ1004 showed that Methylomicrobium alcaliphilum 20Z accounted for more than 80% of the total bacterial population in most experimental runs. This work confirmed the technical feasibility of a new generation of biorefineries based on the abatement of diluted CH4 emissions using extremophile methanotrophs.2019-03-21Ministerio de Economía y Competitividad (CTM2015-70442-R project and Red NOVEDAR)Unión Europea-FEDER Funding Program y Junta de Castilla y León (hD Grant contract Nº E-47-2014-0140696 y UIC71