Towards the Assessment of an Ecological Index for Quantifying Sustainability of Day Life. A Case Study of the Environmental Consequences of Dietary and Transport in a Standard Workday

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Energy Sustainability Analysis (ESA) of Energy-Producing Processes: A Case Study on Distributed H2 Production

In the sustainability context, the performance of energy-producing technologies, using different energy sources, needs to be scored and compared. The selective criterion of a higher level of useful energy to feed an ever-increasing demand of energy to satisfy a wide range of endo- and exosomatic human needs seems adequate. In fact, surplus energy is able to cover energy services only after compensating for the energy expenses incurred to build and to run the technology itself. This paper proposes an energy sustainability analysis (ESA) methodology based on the internal and external energy use of a given technology, considering the entire energy trajectory from energy sources to useful energy. ESA analysis is conducted at two levels: (i) short-term, by the use of the energy sustainability index (ESI), which is the first step to establish whether the energy produced is able to cover the direct energy expenses needed to run the technology and (ii) long-term, by which all the indirect energy-quotas are considered, i.e., all the additional energy requirements of the technology, including the energy amortization quota necessary for the replacement of the technology at the end of its operative life. The long-term level of analysis is conducted by the evaluation of two indicators: the energy return per unit of energy invested (EROI) over the operative life and the energy payback-time (EPT), as the minimum lapse at which all energy expenditures for the production of materials and their construction can be repaid to society. The ESA methodology has been applied to the case study of H2 production at small-scale (10–15 kWH2) comparing three different technologies: (i) steam-methane reforming (SMR), (ii) solar-powered water electrolysis (SPWE), and (iii) two-stage anaerobic digestion (TSAD) in order to score the technologies from an energy sustainability perspective

Development of a Photosynthetic Microbial Electrochemical Cell (PMEC) Reactor Coupled with Dark Fermentation of Organic Wastes: Medium Term Perspectives

In this article the concept, the materials and the exploitation potential of a photosynthetic microbial electrochemical cell for the production of hydrogen driven by solar power are investigated. In a photosynthetic microbial electrochemical cell, which is based on photosynthetic microorganisms confined to an anode and heterotrophic bacteria confined to a cathode, water is split by bacteria hosted in the anode bioactive film. The generated electrons are conveyed through external "bio-appendages" developed by the bacteria to transparent nano-pillars made of indium tin oxide (ITO), Fluorine-doped tin oxide (FTO) or other conducting materials, and then transferred to the cathode. On the other hand, the generated protons diffuse to the cathode via a polymer electrolyte membrane, where they are reduced by the electrons by heterotrophic bacteria growing attached to a similar pillared structure as that envisaged for the anode and supplemented with a specific low cost substrate (e.g., organic waste, anaerobic digestion outlet). The generated oxygen is released to the atmosphere or stored, while the produced pure hydrogen leaves the electrode through the porous layers. In addition, the integration of the photosynthetic microbial electrochemical cell system with dark fermentation as acidogenic step of anaerobic digester, which is able to produce additional H2, and the use of microbial fuel cell, feed with the residues of dark fermentation (mainly volatile fatty acids), to produce the necessary extra-bias for the photosynthetic microbial electrochemical cell is here analyzed to reveal the potential benefits to this novel integrated technology

Closing the Loop: a Sustainable Strategy for MSW Management with Zero Residues and Energy Production

he management of Municipal Solid Waste (MSW) has always represented an important challenge of our society, and it is a constantly evolving issue characterized by variable temporal and spatial specificities. Despite recent technological developments, Waste-to-Energy (WtE) approaches considering environmental and energy sustainability factors and their implementation in real contexts are rather scarce. Unsorted MSW (the residue aside from the differentiate collection of recyclables) can be divided into key fractions for WtE applications, such as the gasification of the Refuse Derived Fuel (RDF) cut or the anaerobic digestion (AD) of the Organic Fraction of Municipal Solid Waste (OFMSW); however, there are certain residues of these processes as well as other fractions of MSW which typically end up in landfills. The present ex-ante study evaluates the convenience of introducing a Plasma Torch (PT) in the management strategy for unsorted MSW replacing the landfill option. The research is based on the modeling of the PT, considering the possible feed streams to this unit. In addition, sensitivity studies are carried to shed light on suitable operating conditions (temperature, equivalence ratio, gasifying agent) and the convenience of the process is assessed from an environmental and energy point of view, by comparing the PT scenario with the baseline case of landfilling. The Life Cycle Assessment (LCA) suggests that the environmental loads can be significantly reduced (>80%) by introducing the PT unit, while the system shows an increase of more than 50 % in the Energy Sustainability Index (ESI)

Repurposing Tempeh Fermentation: a Promising Protein Source Using Food Residues and Edible Filamentous Fungi

Brewers' spent grains (BSG) are the main by-product of the brewery industry, accounting for more than 80 % of total produced by-products. Although this matrix is primarily composed of hemicellulose, cellulose, protein and lignin, the current end-of-life scenario for BSG is as livestock feed. In the present study, a valorisation approach for BSG that uses an edible fungus (Rhizopus oligosporus) in solid state fermentations (SSF) is proposed. First, a microbiological characterization is performed, to shed light on the indigenous microorganisms that are present in the BSG matrix. Then, an appropriate technology approach is used for the SSF that can be conducted both at laboratory and household levels. In the SSF experiments, different temperature (30-35 °C), mass of BSG substrate, inoculum ratio (10 and 15 % v/m) and drilling patters for the aeration of the systems are investigated. The fermentation products were characterized by preparing homogenized samples; it was registered an increase in protein content (5-64%), a slight acidification (ΔpH=0.1-1.2), a decrease of °Brix and the loss of organic matter (and water). The formation of the tempeh cakes was variable, and the differences are analyzed in terms of the operational parameters of each studied batch

Measurements of Protein Content in Aqueous and Alkaline Extracts from Brewer's Spent Grains (bsg): Insights Into the Extraction Kinetics and Energy Consumption

The brewers’ spent grain (BSG) is a rich biomass matrix containing several compounds of interest that require urgent and suitable valorisation strategies, due to its high production volume in the brewing industry. Among the most widespread approaches is the preparation of extracts, targeting particular compounds or soluble and/or insoluble fractions, after operating pre-treatment processes. In the present study, extraction experiments are carried out with fresh untreated BSG, under very gentle extraction conditions (room temperature and moderate agitation, in the 0-5 h interval), and using different solvents: deionized water, 0.1 M NaOH and 0.5 M NaOH in a 1:5 m/v solid-to-solvent ratio. The extraction dynamics were followed by monitoring the dry matter (DM) content obtained in the extracts after a centrifugation step. The protein content is estimated in each case by means of two different methods: direct measurements of absorbance at 280 nm (using bovine serum albumin, BSA, and commercial whey protein isolate as standards) as well as using the Bradford colorimetric method and BSA standard; the consistency of these measurements is contrasted against the DM values. The apparent extraction kinetics were studied, using a saturation model; the coefficients and their range of uncertainty were obtained. Extraction efficiencies in the range 14.24%-53.60% gDM ext/gDM BSG are achieved, which correspond to extraction yields of 38.88-150.09 gDM ext/kg fresh BSG. In addition, the energy footprint of the process is estimated at laboratory scale