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Biogas is a renewable energy resource produced during the anaerobic digestion of various organic substrates. A wide community of microorganisms is involved, including methanogens. These Archaea are the biologic key to the process because they accomplish the methane-forming reaction. Despite its crucial role, the microbiome inside the digester is poorly understood. The aim of this work is to develop bioindicators of efficiency for the anaerobic process through the quantification and characterisation of the methanogens and sulphate-reducing bacteria. From a full-scale digester fed with organic wastes, 31 samples were collected. Temperature, pH, acidity, alkalinity and biogas quantity and quality were monitored over time. The methanogens were detected from the samples both in total and as belonging to different taxa units. These evaluations, by real-time quantitative PCR (RT-qPCR) methods, produced valuable results for Methanosarcina, Methanosaeta, Methanocorpusculaceae and sulphate-reducing bacteria. Methanosarcina was the most abundant family, followed by Methanocorpusculaceae and then Methanosaeta. The methanogen taxa are significantly and directly correlated with each other (p < 0.05). Methanosaeta and Methanocorpusculaceae are present in significantly different amounts at different temperatures. While Methanosaeta levels also change when the organic load increases (t test, p < 0.05), Methanosarcina is more tolerant, and its levels are quite constant. Methanosarcina and Methanosaeta are proposed to be bioindicators of the stability of the process (the first) and of susceptibility (the second) to detect early sufferance conditions in the digester. These methods will be useful in the control and optimisation of an eco-friendly waste-to-energy system.

Abstract Purpose of the Review The scope of this work is to present a critical review of the novel class of plants for the enhanced production of bioproducts in power and biomass-to-X (PBtX) plants, where the excess carbon in the feedstock is converted into a product thanks to the addition of hydrogen from water electrolysis, rather than being vented as CO2. Recent Findings The review of the recent literature shows that (i) a significant gain in carbon efficiency can be achieved with this class of plants compared to corresponding biomass-to-X plants; (ii) there is high dependency of the power-to-X efficiency on the efficiency of the electrolysis system and a relatively low dependency on the final product; and (iii) the economic competitivity of PBtX plants is closely associated to the cost of hydrogen (i.e., electrolysis capital cost, electricity cost, and capacity factor) and such systems cannot rely only on green hydrogen from the low expected amounts of excess electricity from intermittent renewables. Summary In this work, through a simplified economic analysis, the region of competitiveness of this class of plants compared to other possible uses of biomass has been qualitatively identified. The research gaps mainly lie in the lack of assessments on the design and operating criteria of flexible PBtX plants and of studies providing insights on the value of flexibility for a PBtX plant, when integrated in the electric energy systems of the future.

Filter feeding invertebrates are a relevant component of fouling assemblages with a pivotal role in ecological processes, since they improve water quality, enhance habitat heterogeneity and transfer organic matter from the water column to the benthos. They modulate the availability of resources to other species, with effects on the density and behavior of the surrounding macrofauna. The fanworm Sabella spallanzanii, one of the largest and most abundant Mediterranean filter feeders, provides a shelter for predation and a secondary substrate for algae and settlement for sessile invertebrates. We tested its role in driving the structure of fouling assemblages, through a removal experiment.The experiment was one-year-long, with four sampling times. The effect of the removal on the fouling community was marginal in terms of species richness and evenness, while the biomass showed important differences, with a constant increase over time with higher values in the samples containing S. spallanzanii. At the end of observations, the biomass reached the value of 3917 g DW m-2 in controls and 2073 g DW m-2 in treatments. The empty space left by fanworms was not used by other species with similar biomasses. It is possible that the functioning of fouling communities may, in the event of loss of species, fluctuate in terms of biomass mobilization to different compartments, either towards the pelagic compartment or to the detritus chain. In systems with reduced water turnover, this by-pass can have important consequences in terms of stability and ecological balance.

Annually, 115.000 tons of plastic tableware are used in Italy. The end of life of these objects is particularly troubled because no efficient way of recycling or reusing exist. Studies performed by the European Union demonstrate that about 80% of sea waste is made of plastic, representing a danger to human health and ecosystem. The aim of this paper is to analyse substitutes to disposable plastic tableware using the Life Cycle Assessment methodology. The alternatives are objects made of bio compostable plastic, both disposable and reusable. This article compares single-use and multi-use tableware made of a Polylactic acid (PLA) - Polybutylene succinate (PBS) blend with traditional disposable tableware made of polypropylene and of polystyrene. In order to perform an effective assessment, the objects are grouped in place settings, each made of a cup, a plate and cutlery. The use of tray mat and napkin is also taken into account. It was assumed that the fossil-based items are sent to landfill whereas the bio-based ones are sent to a compost plant. The functional unit chosen was “the service of 1000 meals”. The impact categories taken into account are Global Warming 100a, Ozone Depletion, Ozone Formation (Vegetation), Acidification, Aquatic Eutrophication, Human Toxicity water and Ecotoxicity water chronic. The results show that the compostable table sets have lower impact than the sets made of fossil-based plastic in all the categories except in Ozone Depletion and in Aquatic Eutrophication. In the categories of Human Toxicity water and Ecotoxicity water chronic, fossil-based materials have higher impact than multi-use one mainly due to the landfill scenario chosen as end of life. Disposable and reusable systems give a different contribution to total impact in different life stages. For disposable systems, the production and the end of life are the critical stages in terms of environmental burden, whereas for reusable systems washing is the most impactful phase. Further improvements can be obtained in the production of bio-based materials by using renewable energy to power the facilities whereas the washing phase can be improved by adopting certified ecopower. The impact of the reusable system strongly depends on the assumptions made on the number of reuses and on the washing modality.

A dynamic model was developed for representing the abatement of sulfates and metals in column reactors inoculated with sulfate reducing bacteria. The model framework includes both bioactive mechanisms (bioreduction of sulfates and bioprecipitation of metals) and passive abiotic mechanism (sorption onto the column filling). Sorption capacities of column filling material were determined by dedicated tests of sulfate and cadmium removal. These experimental data implemented in model framework denoted that before steady state sorption mechanism could predominate over bioactive mechanism. Sensitivity analysis confirmed that, varying sorption and bioreduction parameters in typical range of laboratory scale systems, sorption cannot be neglected before steady state. An operative equation was obtained by literature data and model simulations showing that in the majority of works reported in the literature the operational times used for column experiments are not sufficient to saturate column sorption capacity. © 2013 American Institute of Chemical Engineers Environ Prog, 33: 70–80, 2014

AbstractGlobal impact models represent process-level understanding of how natural and human systems may be affected by climate change. Their projections are used in integrated assessments of climate change. Here we test, for the first time, systematically across many important systems, how well such impact models capture the impacts of extreme climate conditions. Using the 2003 European heat wave and drought as a historical analogue for comparable events in the future, we find that a majority of models underestimate the extremeness of impacts in important sectors such as agriculture, terrestrial ecosystems, and heat-related human mortality, while impacts on water resources and hydropower are overestimated in some river basins; and the spread across models is often large. This has important implications for economic assessments of climate change impacts that rely on these models. It also means that societal risks from future extreme events may be greater than previously thought.