• Energy Research

The effect of different management techniques for plant control in the vineyard were compared in the present work, focusing on plant diversity preservation and management efficacy in a two-year experiment on vineyard row weed community. Biomass-fueled flame weeding (with two intensities) was applied as an innovative plant control technique in contrast to tillage and mowing practices. The results showed that flaming was comparable to tillage regarding weed control effectiveness, and was more efficient than mowing. However, species number and functional evenness were not substantially modified by changing the applied management technique. Functional trait analysis demonstrated that row management significantly affected the frequency of annual plants, plant height, root depth index, and the occurrence of plants with storage organs. As for species composition, meaningful differences were found: only the two flaming treatments (i.e. gentle vs intense) and the gentle flaming vs mowing had consistent species composition. Flame wedding showed some potential benefits in plant control in the vineyard by favouring small plant and controlling overall weed abundance. On the other hand, flaming favoured plant species with asexual reproduction, with a potential negative impact on weed-vine competition and species persistence in the vineyard. Further studies are required to investigate such contrasting aspects, also considering other weed control techniques (e.g. cover-crops), considering a sustainable perspective of an herbicide-free environment.

Abstract The aim of the work was to evaluate the techno-economic feasibility of anaerobic digestion implementation in small breweries located in the mountain area of Friuli-Venezia Giulia region (Italy). A territory-oriented approach was adopted, analysing the production of organic residues in local breweries and the potential methane production from each residue. An energy balance and a simplified dimensioning for anaerobic reactor installation at brewery scale was proposed, analysing actual energy consumption and the effect of biogas on plant energy balance improvement. Brewery spent grain, spent yeast, whirlpool residue and end-of-fermentation beer were identified as the main organic residues in the analysed plants. Biochemical methane potential tests revealed high methane potential of spent yeast, up to 486.9 NL CH4/kg VSadded, and spent grain, up to 356.2 NL CH4/kg VSadded. Granular activated carbon and biochar were added to selected tests to evaluate an eventual increase in methane yield; a noticeable effect was observed in particular on spent yeast, due to the enhanced microorganism activity and C/N ratio optimization. Co-digestion tests were performed on spent grain and spent yeast: a synergistic effect arose with a mixture of 70% spent yeast and 30% spent grain, where methane yield increased up to 447.7 NL CH4/kg VSadded. Electricity consumption was estimated as 130.6–148.9 MJ/hL, while heat need was 116.4–147.0 MJ/hL; it was showed that anaerobic digestion implementation, through a digester having 65 m3 volume, could provide up to 53.9% of electric and 64.4% of thermal need of the facility.

In recent years, the entire agricultural and agri-food sector, and in particular the wine sector, has been comparing and adapting to the issue of environmental sustainability, both within the vineyard and within the winery. In this context, various projects and methodologies have been developed to measure the environmental sustainability of the wine sector as a whole (VIVA project). To enter into this perspective, however, the wineries must equip themselves with very complex parameter measurement systems as well as data processing and currently only few of them are able to do so, as most wineries do not have the equipment both at the instrumentation and software level and also do not possess the required expertise. In order to verify the measurement and size of some cellar parameters related to sustainability, a survey was carried out in the area of Friuli Venezia Giulia and Eastern Veneto.The results showed that electricity consumption in Wh/l of produced wine varies considerably depending on the average temperature during the harvesting period and, in the specific case of a small-medium sized Friulian winery (about 2,000 hl/year of wine), the performance indicator shows consumption of around 250-350 Wh/l. As for the consumption of water in the cellar, blue water consumption from the aqueduct in general is around a value of 4 liters of water per liter of produced wine. In the three wineries that take part in the VIVA project, the value is 2.5 liters of water/liter of wine (medium-large wineries). From the analysis it can be observed that water and electricity consumption are high but very variable depending on the climate, place, type of wine, type of cellar.

Nowadays, sustainable approaches to waste management are becoming critical, due to increased generation and complex physicochemical composition. Waste electric and electronic equipment (WEEE) management, in particular, is being given increasing attention due to the continuous augment in electronic equipment usage and the limited recycling rates. In this work, a multi-objective engineering optimization approach using a decision support system (DSS) was used to analyze the feasibility of installing a WEEE treatment plant in the Friuli-Venezia Giulia region (Northeastern Italy), considering that most of the produced WEEE is currently exported outside the region. Meaningful economic and environmental parameters were considered in the assessment, together with current WEEE production and composition. Plant investment cost was in the range of EUR 7–35 M for a potentiality of 8000–40,000 ton of treated WEEE/yr, the lower bound corresponding to the WEEE produced in the region. Payback time was 4.3–10 yr, strongly depending on the market’s economic conditions as well as on plant potentiality. Proper public subsidies should be provided for a plant treating only the locally produced WEEE, establishing a circular economy. The fraction of recovered materials was 78–83%, fulfilling the current EU legislative requirements of 80% and stabilizing around values of 80% for a higher washing machine fraction. An increase in personal computers may allow to augment the economic revenues, due to the high conferral fees, while it reduces the amounts of recovered materials, due to their complex composition. CO2 emission reduction thanks to material recovery was in the range of 8000–38,000 ton CO2/yr, linearly depending on the plant potentiality. The developed DSS system could be used both by public authorities and private companies to preliminarily evaluate the most important technical, financial and environmental aspects to assess overall plant sustainability. The proposed approach can be exported to different locations and integrated with energy recovery (i.e., incineration of the non-recoverable fractions), analyzing both environmental and economic aspects flexibly.

Up-flow anaerobic sludge blanket (UASB) reactor belongs to high-rate systems, able to perform anaerobic reaction at reduced hydraulic retention time, if compared to traditional digesters. In this review, the most recent advances in UASB reactor applications are critically summarized and discussed, with outline on the most critical aspects for further possible future developments. Beside traditional anaerobic treatment of soluble and biodegradable substrates, research is actually focusing on the treatment of refractory and slowly degradable matrices, thanks to an improved understanding of microbial community composition and reactor hydrodynamics, together with utilization of powerful modeling tools. Innovative approaches include the use of UASB reactor for nitrogen removal, as well as for hydrogen and volatile fatty acid production. Co-digestion of complementary substrates available in the same territory is being extensively studied to increase biogas yield and provide smooth continuous operations in a circular economy perspective. Particular importance is being given to decentralized treatment, able to provide electricity and heat to local users with possible integration with other renewable energies. Proper pre-treatment application increases biogas yield, while a successive post-treatment is needed to meet required effluent standards, also from a toxicological perspective. An increased full-scale application of UASB technology is desirable to achieve circular economy and sustainability scopes, with efficient biogas exploitation, fulfilling renewable energy targets and green-house gases emission reduction, in particular in tropical countries, where limited reactor heating is required.

Char is a valuable product obtained from thermochemical conversion processes of different biomass feedstocks, mainly pyrolysis and hydrothermal carbonization (HTC). In this work, anaerobic digestion (AD) integration with pyrolysis/HTC is critically reviewed, considering anaerobic digestates as feedstocks for char production. This virtuous interconnection can boost sustainable digestate valorization in the circular economy framework. Different substrates for AD are investigated, including sewage sludge, food waste, agricultural residues, and animal manure. The available thermochemical technologies, including pyrolysis, HTC and other processes are considered, analyzing the effects of substrate characteristics and process parameters on char quality. The possible fields of char application are successively presented, including agricultural application, energy recovery, pollutants adsorption, catalysts production, and electrochemical technologies; the advantages and drawbacks of each application are highlighted. Limitations still preventing the full-scale application of digestate-derived char production and utilization include the variability in substrate characteristics and the presence of undesired pollutants (especially in sewage sludge digestate), full-scale development of thermochemical plants, lacking legislative frameworks, uncertain economic sustainability, limited eco-toxicological studies, and stakeholders’ acceptance. Future research needed on the topic is finally depicted, with the aim of widening digestate reuse applications, as thermochemical processes may prevent safety concerns linked to direct agricultural reuse, leading to sustainable biorefinery platforms.

Abstract In this work, different pretreatment technologies (low temperature thermal treatment, ultrasonication, alkali treatment, combined alkali-thermal treatment, icing-thawing) were investigated together with biochar addition to increase biogas yield from sewage sludge. The aim of the work was to develop a standardized protocol, including physicochemical characterization, biochemical methane potential (BMP) tests, digestate characterization, life cycle assessment (LCA) and economic analysis, to verify the techno-economic suitability and the related environmental impacts of upgrading conventional full-scale anaerobic digesters. Low-temperature (65–85 °C) thermal pretreatment showed the best performances in enhancing sludge solubilization and methane yield (up to 110%), followed by ultrasonication (up to 53%) and biochar addition (about 16%). The solubilization rate obtained after each pretreatment was similar for municipal and industrial sludge; however, it did not correspond to a proportional increase in methane yield. LCA showed that ultrasonication led to the worst environmental impacts at laboratory scale, due to the huge electricity request; however, at full-scale conditions, green-house gases (GHG) emissions could be reduced by 22%, fossil depletion by 25% and stratospheric ozone depletion by 18%, when compared to the baseline scenario (raw sludge anaerobic digestion). The economic analysis proved that the high ultrasonication capital costs could not be recovered in the considered timeframe (15 yr), while biochar price should be significantly lowered (down to 6.5 €/ton) to give an overall positive outcome. Finally, the thermal scenario would be convenient only when considering waste heat recovery. The proposed protocol, including physicochemical sludge characterization, BMP tests, digestate characterization, LCA and economic analysis, could be extended to other existing digesters to compare alternative pretreatment strategies, enhancing renewable energy generation in biogas form.

A methodological procedure, based on results from batch experiments, is proposed and applied to a selected wastewater treatment plant generating a poorly degradable sludge, to identify the best configuration and ozone dosage for full-scale application of sludge ozonation. Samples of pre-thickened and digested sludge were collected, tested at different ozone dosages and characterized to gather useful data for energy, economic and carbon footprint balances. The most viable scenario was found to be sludge pre-treatment at the lowest tested dosage (20 mg O3/g VS), yielding energy, cost and GHG emission net savings of 177 MWh/y, 57.8 k€/y and 6.38 Mg CO2-eq./y, respectively. Sensitivity analyses, conducted by varying the specific energy required for ozone generation and the unit costs for sludge disposal and resource supply, confirmed the stability of this scenario, whereas a field pilot-scale testing is advisable to verify modified process conditions for a safe and efficient application of sludge ozonation. The proposed methodology, including laboratory batch anaerobic digestion tests, scenario definition and energy/economic/environmental balances, could be preliminary applicable to all situations to broadly analyze all involved aspects and give a useful overview about the effective applicability of sludge ozonation.