Performance of a biogas upgrading process based on alkali absorption with regeneration using air pollution control residues

This work analyzes the performance of an innovative biogas upgrading method, Alkali absorption with Regeneration (AwR) that employs industrial residues and allows to permanently store the separated CO₂. This process consists in a first stage in which CO₂ is removed from the biogas by means of chemical absorption with KOH or NaOH solutions followed by a second stage in which the spent absorption solution is contacted with waste incineration Air Pollution Control (APC) residues. The latter reaction leads to the regeneration of the alkali reagent in the solution and to the precipitation of calcium carbonate and hence allows to reuse the regenerated solution in the absorption process and to permanently store the separated CO₂ in solid form. In addition, the final solid product is characterized by an improved environmental behavior compared to the untreated residues. In this paper the results obtained by AwR tests carried out in purposely designed demonstrative units installed in a landfill site are presented and discussed with the aim of verifying the feasibility of this process at pilot-scale and of identifying the conditions that allow to achieve all of the goals targeted by the proposed treatment. Specifically, the CO₂ removal efficiency achieved in the absorption stage, the yield of alkali regeneration and CO₂ uptake resulting for the regeneration stage, as well as the leaching behavior of the solid product are analyzed as a function of the type and concentration of the alkali reagent employed for the absorption reaction.     

Nepotistic access to food resources in cooperatively breeding carrion crows

Offspring delayed dispersal is the principal mechanism leading to formation of kin-based societies. It has been suggested that parents promote offspring philopatry by providing them with preferential access to the food resources of the territory and that parental tolerance may be affected by territory quality. However, few studies have addressed this hypothesis in kin-living vertebrate species. Here, we show that in cooperative breeding groups of carrion crows (Corvus corone corone) containing retained offspring and immigrants, dominant breeding males behaved nepotistically on an experimental source of food by (1) attacking immigrants with more frequency and intensity than offspring and (2) associating preferentially with their offspring on the feeding spot and sharing food with them. This parental facilitation allowed the offspring to spend more time feeding than higher-rank immigrants. We also found that a year-round experimental food supplementation neither increased breeding males’ tolerance nor relented the overall aggressiveness in the groups. This indicates that higher natal philopatry observed on fed territories compared to unfed ones is not a consequence of a more benign social environment. Rather, it suggests that offspring value territory resource wealth and adjust the timing of dispersal accordingly.     

Mediterranean Coastal Sand Dune Vegetation: Influence of Natural and Anthropogenic Factors

The aim of the present work was to assess the conservation status of coastal dune systems in Tuscany (Italy). Emphasis was given to the presence and abundance of plant communities identified as habitat in accordance with the Directive 92/43/EEC. Twenty transects perpendicular to the shoreline were randomly positioned on the whole coastal area (30 km in length) in order to sample the full spectrum of plant communities. Vegetation zonation and relationships with the most frequent disturbance factors in the study area—beach cleaning, coastline erosion, presence of paths and roads, bathing settlements and trampling—were investigated through principal coordinate analysis and canonical correspondence analysis. Natural factors, such as distance from the sea and total length, were also considered. Differences in the conservation status of the sites were found, ranging from the total disappearance of the foredune habitats to the presence of the complete psammophilous (sand-loving) plant communities. Erosion, trampling, and paths were found to be closely correlated with degradation and habitat loss. Furthermore, the overall plant species diversity of dunes was measured with NH_Dune, a modified version of the Shannon index; while the incidence of invasive taxa was calculated using N, a naturalness index. However, these diversity indices proved to be a weaker bioindicator of ecosystem integrity than habitat composition along transects. A possible strategy for the conservation and management of these coastal areas could be to protect the foredunes from erosion and limit trampling through the installation of footbridges or the use of appropriate fences.     

From waste to value-added products: A review of opportunities for fish waste valorization

The fishing industry is responsible for generating large amounts of organic waste rich in compounds of commercial interest. This review aimed to present the state of the art about the possibilities of using solid waste to obtain value-added products. Skins, fins, and scales have been used to obtain gelatin and collagen, a promising compound for use as an additive in yogurts and creams, as well as for the synthesis of biodegradable packaging that, if applicable, can reduce the environmental impact caused by petroleum packaging. Other parts, such as the head and the viscera, contain polyunsaturated fatty acids and other fat-soluble vitamins that have been studied for the production of omega-3 capsules for the pharmaceutical industry, but when the extracted oil does not fit the feeding parameters, it can be applied for the production of biodiesel. Furthermore, fishes are a promising source of astaxanthin, a carotenoid with high antioxidant properties. The use of combined techniques such as chemical and enzymatic methods can increase the extraction yield and favor the obtaining of more purified compounds, in addition to promoting the reduction of chemicals that are aggressive to the environment. In general, conscious production in the fishing industry through the valorization of waste generated for use as inputs for other value chains encompasses aspects of the circular economy, which can positively impact several Sustainable Development Goals.     

Bioassays for the evaluation of reclaimed opencast coal mining areas

Environmental Science and Pollution Research - This study aimed to use bioassays (single and multispecies) with organisms from different trophic levels to assess soil quality in reclaimed coal...     

Image analysis application for the study of activated sludge floc size during the treatment of synthetic and real fishery wastewaters

Background, aim, and scope  

Fishery wastewater treatment can be compromised due to seasonal production. The use of sequencing batch reactors is not completely successful, despite flexibility being one of the principal advantages. Most research on activated sludge is performed using synthetic wastewater to ensure a stable and constant feed. The current work compared biomass morphology and settling ability using image analysis of synthetic and real fishery wastewaters, with and without NaCl addition.     

Behaviour of arsenic in forested catchments following a high-pollution period

Due to high availability of adsorption sites, forested catchments could be net sinks for pollutant arsenic both during the period of increasing and decreasing pollution. We tested this hypothesis along a north-south pollution gradient in spruce die-back affected areas of Central Europe. For two water years (2007-2008), we monitored As fluxes via spruce-canopy throughfall, open-area precipitation, and runoff in four headwater catchments (Czech Republic). Since 1980, atmospheric As inputs decreased 26 times in the north, and 13 times in the south. Arsenic export by runoff was similar to atmospheric inputs at three sites, resulting in a near-zero As mass balance. One site exhibited a net export of As (2.2 g ha⁻¹ yr⁻¹). In contrast, the preceding period (1995-2006) showed much higher As fluxes, and higher As export. Czech catchments do not serve as net sinks of atmospheric As. A considerable proportion of old industrial arsenic is flushed out of the soil.     

DGT use in contaminated site characterization. The importance of heavy metal site specific behaviour

The objective of this study is to provide an insight into the techniques for measuring the lability of heavy metals in solid-phase pool of soils in order to assess the environmental risk arising from pollution. The technique of diffusive gradients in thin films (DGT) and a sequential extraction procedure were used to quantify the labile pools of Cu, Fe, Mn and Ni. These results were compared to metal concentrations in groundwater, measured directly using the in situ piezometers, and to the total concentration of metal in the soils. High concentrations of metal in the directly analysed soil solution compared to DGT measurement were attributed to the presence of colloidal metal. The use of DGT allowed only to calculate leaching parameters of the free ions and labile fractions of the metals. For this reason DGT technique needs preliminary investigation on metal speciation in soil solution before its application as a good tool in the characterization procedure of contaminated sites.     

Ecotoxicological effects of sediments from Mar Piccolo,South Italy: toxicity testing with organisms from different trophic levels

The Mar Piccolo of Taranto (Ionian Sea, Southern Italy) is a semi-enclosed and strongly polluted basin. For decades, it has been subjected to different anthropogenic impacts. These stressors caused severe sediments contamination with high concentration of different pollutants (PAHs, PCB, heavy metals). In order to assess the current status of sediments contamination, an ecotoxicological investigation combined with chemical analysis (heavy metals, PAH, and PCB) has been performed. In order to derive ecologically relevant conclusions, a multiorganisms and multiend-points approach has been applied, exposing organisms from different trophic levels to elutriate and whole sediment. The battery of bioassays consists of a microalgal growth inhibition test (Dunaliella tertiolecta), acute and sublethal assays (end-points: mortality, immobilization and swimming speed alteration) on crustaceans larvae and juveniles, and rotifers (Amphibalanus amphitrite, Artemia salina, Corophium insidiosum and Brachionus plicatilis), and embryotoxicity test on echinoderms (Paracentrotus lividus). Considering the high levels of sediment contamination highlighted from chemical analysis, an unexpected very low toxic effect was observed, even considering the sublethal end-point (larval swimming speed alteration). The results of this study suggest a very complex contaminants dynamic in the Mar Piccolo sediments that, despite a strong level of contamination, seems to not affect in a proportional manner the biological compartment.