Anaerobic digestion (AD) could be considered as a mature technology and nowadays it can still play a pivot role because of the urgent need to provide renewable energy sources and efficiently manage ...the continuously growing amount of organic waste. Biochar (BC) is an extremely versatile material, which could be produced by carbonization of organic materials, including biomass and wastes, consistently with Circular Economy principles, and “tailor-made” for specific applications. The potential BC role as additive in the control of the many well-known critical issues of AD processes has been increasingly explored over the past few years. However, a clear and comprehensive understanding of the connections between BC and AD is still missing. This review paper analyses and discusses significant references (review articles, research papers and international databases and reports), mostly published in the last 10 years. This review is aimed at addressing three key issues related to the better understanding of the BC role in AD processes: 1. Investigation of the influence of BC properties on AD performances and of their ability to counteract its main challenges; 2. Assessment of the optimal BC production chain (i.e. feedstock-pyrolysis-activation) to achieve the desired features; 3. Evaluation of the economic and environmental advantages connected to BC use in AD processes, compared to conventional solutions applied to address AD challenges.
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•Biochar key properties were specific surface, pores and surface functional groups.•Lignocellulosic biomass, slow pyrolysis and physical activation made the best biochar.•Biochar addition exhibited economic and environmental advantages.•Biochar improved methane production (in average 25 %) and digestate quality.
This work has as main objective the analysis of waste from electric and electronic equipment (WEEE or e-waste) management through material flow analysis and life cycle assessment of a full-scale ...Italian facility that is significant about the e-waste flows treated (9900 t/y) and representative of a developed EU country about the industrial process outline, based on manual dismantling phases and physic-mechanical automatic processes. Three WEEE categories (i.e. R1-Cooling equipment, R2-Large household appliances and R3- TVs and screens) have been chosen with the reason that they are the most abundant in EU. The methodology was based on two end-of-life scenarios: S0-partial recycling of valuable fractions and landfilling of the rest, which is conventional e-waste processing in Italian facilities; S1-complete recycling of valuable fractions, limited incineration and landfilling of the rest, which describes what happens in the considered case study. Mass balance of the three treatment lines showed recycling rate (RR) values equal to: for R1 40% for S0 and 80% for S1; for R2 65% for S0 and 99% for S1; for R3 86% for S0 and 91% for S1, with significant fractions incinerated or landfilled only for R1 treatment line. Life cycle assessment considered transport (post-consumer collection), treatment, recycling, incineration and disposal. As main results, eco-toxicity aquatic potentials referring to marine and fresh water were the most relevant impact categories. In conclusion, recycling (mostly of metals) played a crucial role for environmental benefits, and transport and polyurethane plus rubber incineration for the environmental impacts.
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•WEEE management was analyzed in an Italian full-scale plant•Two recycling scenarios (S0,- partial and S1 - enhanced) were investigated•Recycling rates were 40-86% for S0 and 80-99% for S1 for different WEEE types•Main environmental benefits derived from recycling of metals and other fractions•Main environmental impacts were due to transport and polyurethane incineration
This study explored the performances of waste polyurethane foam (PUF) derived from the shredding of end-of-life refrigerators as an adsorbent for wastewater treatment. The waste PUF underwent a basic ...pre-treatment (e.g., sieving and washing) prior the adsorption tests. Three target pollutants were considered: methylene blue, phenol, and mercury. Adsorption batch tests were performed putting in contact waste PUF with aqueous solutions of the three pollutants at a solid/liquid ratio equal to 25 g/L. A commercial activated carbon (AC) was considered for comparison. The contact time necessary to reach the adsorption equilibrium was in the range of 60-140 min for waste PUF, while AC needed about 30 min. The results of the adsorption tests showed a better fit of the Freundlich isotherm model (R
= 0.93 for all pollutants) compared to the Langmuir model. The adsorption capacity of waste PUF was limited for methylene blue and mercury (K
= 0.02), and much lower for phenol (K
= 0.001). The removal efficiency achieved by waste PUF was lower (phenol 12% and methylene blue and mercury 37-38%) compared to AC (64-99%). The preliminary results obtained in this study can support the application of additional pre-treatments aimed to overcome the adsorption limits of the waste PUF, and it could be applied for "rough-cut" wastewater treatment.
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•New concept of cascadic use of food waste was investigated.•SHF and SSF approaches for LA have been executed.•Yield and productivity were slightly higher for SHF compared to ...SSF.•Integration of biogas production from fermentative residues.•Preliminary economic and environmental assessment of the proposed two-step biorefinery process.
This work concerns the investigation of the sequential production of lactic acid (LA) and biogas from food waste (FW). LA was produced from FW using a Streptococcus sp. strain via simultaneous saccharification and fermentation (SSF) and separate enzymatic hydrolysis and fermentation (SHF). Via SHF a yield of 0.33gLA/gFW (productivity 3.38gLA/L·h) and via SSF 0.29gLA/gFW (productivity 2.08gLA/L·h) was obtained. Fermentation residues and FW underwent anaerobic digestion (3wt% TS). Biogas yields were 0.71, 0.74 and 0.90Nm3/kgVS for FW and residues from SSF and SHF respectively. The innovation of the approach is considering the conversion of FW into two different products through a biorefinery concept, therefore making economically feasible LA production and valorising its fermentative residues. Finally, a mass balance of three different outlines with the aim to assess the amount of LA and biogas that may be generated within different scenarios is presented.
The shredding of end-of-life refrigerators produces every year in Italy 15,000 tons of waste polyurethane foam (PUF), usually destined for energy recovery. This work presents the results of the ...investigation of the oil sorption potential of waste PUF according to ASTM F726-17 standard. Three oils (diesel fuel and two commercial motor oils) having different densities (respectively, 0.83, 0.87, and 0.88 kg/dm
) and viscosities (respectively, 3, 95, and 140 mm
/s at 40 °C) were considered. The waste PUF was sampled in an Italian e-waste treatment plant, and its characterization showed 16.5 wt% particles below 0.71 mm and 13 wt% impurities (paper, plastic, aluminum foil), mostly having dimensions (d) above 5 mm. Sieving at 0.071 mm was applied to the waste PUF to obtain a "coarse" (d > 0.71 mm) and a "fine" fraction (d < 0.71 mm). Second sieving at 5 mm allowed an "intermediate" fraction to be obtained, with dimensions between 0.71 and 5 mm. The oil sorption tests involved the three fractions of waste PUF, and their performances were compared with two commercial oil sorbents (sepiolite and OKO-PUR). The results of the tests showed that the "fine" PUF was able to retain 7.1-10.3 g oil/g, the "intermediate" PUF, 4.2-7.4 g oil/g, and the "coarse" PUF, 4.5-7.0 g oil/g, while sepiolite and OKO-PUR performed worse (respectively, 1.3-1.6 and 3.3-5.3 g oil/g). In conclusion, compared with the actual management of waste PUF (100 wt% sent to energy recovery), the amount destined directly to energy recovery could be limited to 13 wt% (i.e., the impurities). The remaining 87 wt% could be diverted to reuse for oil sorption, and afterward directed to energy recovery, considered as a secondary option.
This study introduces to a one-step process for the fermentative production of L(+)-lactic acid from mixed restaurant food waste. Food waste was used as carbon and nitrogen source in simultaneous ...saccharification and fermentation (SSF) using Lactobacillus sp. or Streptococcus sp. strains for L(+)-lactic acid production. Waste consisted of (w/w) 33.5% starch, 14.8% proteins, 12.9% fat and 8.5% free sugars. Lactobacillus sp. strains showed a productivity of 0.27–0.53 g L−1 h−1 and a yield of 0.07–0.14 g g−1 of theoretically available sugars, while Streptococcus sp. more efficiently degraded the food waste material and produced lactic acid at a maximum rate of 2.16 g L−1 h−1 and a yield of 0.81 g g−1. For SSF, no enzymes were added or other hydrolytic treatments were carried out. Outcomes revealed a linear relationship between lactic acid concentration and solid-to-liquid ratio when Streptococcus sp. was applied. Statistically, from a 20% (w/w) dry food waste blend 52.4 g L−1 lactic acid can be produced. Experimentally, 58 g L−1 was achieved in presence of 20% (w/w), which was the highest solid-to-liquid ratio that could be treated using the equipment applied. Irrespective if SSF was performed at laboratory or technical scale, or under non-sterile conditions, Streptococcus sp. efficiently liquefied food waste and converted the released nutrients directly into lactic acid without considerable production of other organic acids, such as acetic acid. Downstream processing including micro- and nanofiltration, electrodialysis, chromatography and distillation gave a pure 702 g L−1 L(+)-lactic acid formulation.
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•An isolated Streptococcus sp. strain converted food waste efficiently into lactic acid.•Max. productivity was 2.16 g L−1 h−1 and yield was 0.81 g g−1 of available sugars.•Increase in solid-to-liquid ratio resulted in increased lactic acid titer.•A solid-to-liquid ratio of 20% (w/w) gave 58 g L−1 lactic acid.•Downstream processing resulted in a 702 g L−1 optical pure L(+)-lactic acid solution.
This study aimed at a quantitative analysis of the material flows associated with End of Life (EoL) lithium-ion batteries’ (LIBs) materials in Europe. The European electric vehicles fleet in 2020 was ...taken as a case study, assuming a 10-year lifetime for the batteries and that the related EoL LIBs would be processed by existing recycling plants via pyrometallurgy, hydrometallurgy, or their combination in sequence. The economic implications (recycling operative costs compared to the revenues from the sales of the recycled metals) and the environmental performances (CO2 eq. emitted, energy demand and circularity performances) were assessed. Based on the gathered results, the existing European recycling capacity will overlook over 78% of the forecasted EoL LIBs. The treatment efficiencies of the full-scale recycling processes allow for the recovery of over 90% of copper, cobalt, nickel, and manganese, 87% of aluminum, and only 42% of lithium and 35% of iron entering the recycling facilities. In overall, LIBs recycling in 2030 will involve the emission of 3.7 Mt of CO2 eq. and an energy demand of 33.6 GWh. Hydrometallurgy presents the best economic and environmental trade-off compared to other recycling strategies. In conclusion, this study demonstrated that current European LIBs’ recycling infrastructure will be inadequate in the near future and the direction (i.e., hydrometallurgy) that its strengthening should pursue.
This review analyzed the literature data about the global warming potential (GWP) of the lithium-ion battery (LIB) lifecycle, e.g., raw material mining, production, use, and end of life. The ...literature data were associated with three macro-areas—Asia, Europe, and the USA—considering common LIBs (nickel manganese cobalt (NMC) and lithium iron phosphate (LFP)). The GWP (kgCO2eq/kg) values were higher for use compared to raw material mining, production, and end of life management for hydrometallurgy or pyrometallurgy. Considering the significant values associated with the use phase and the frequent application of secondary data, this study also calculated the GWP of LIBs applied in public urban buses in Turin, Italy. The 2021 fleet (53% diesel, 36% natural gas, and 11% electric buses) was compared to scenarios with increasing shares of hybrid/electric. The largest reduction in CO2eq emissions (−41%) corresponded to a fleet with 64% electric buses. In conclusion, this review highlighted the bottlenecks of the existing literature on the GWP of the LIB lifecycle, a lack of data for specific macro-areas for production and use, and the key role of public transportation in decarbonizing urban areas.
Municipal wastewater treatment plants (MWWTPs) are essential infrastructures in any urban context, but they may be considered as a potential source of greenhouse gas (GHG) emissions and should be ...coherent with European Union (EU) policy on energy efficiency. This study presents a sustainability evaluation of four Italian and Romanian MWWTPs in terms of energy efficiency and greenhouse gas emissions using Energy Performance and Carbon Emissions Assessment and Monitoring (ECAM) tool software. The obtained results indicated that biogas recovery improved energy performances, while the largest contributions in terms of GHG emissions were in all cases caused by energy consumption and methane produced during wastewater treatment. The Romanian plants exhibited higher GHG emissions, compared to the Italian plants, mainly because of the different values of national conversion factors for grid electricity (0.41 kg CO2/kWh for Italy and 1.07 kg CO2/kWh for Romania). Two scenarios aimed at enhancing the overall sustainability were hypothesized, based on increasing the serviced population or energy efficiency, achieving significant improvements. A sustainability assessment of MWWTPs should be adopted as a useful tool to help water utilities to introduce low-energy, low-carbon management practices as well as being useful for policy recommendations.
Hydropower (HP) is a key source of renewable energy, but also poses significant environmental challenges, including habitat fragmentation, hydropeaking and perturbations of flow and sediment regime. ...This study analyzed how Italian companies managing HP plants, and registered to the European Eco-Management and Audit Scheme (EMAS) in 2022, evaluated their sustainability and publicly disclosed related data. The analysis was based on the environmental statements (ESs) of 206 hydropower plants (29% of Italian HP production in 2019). The applied methodology involved an inventory of the plants and their categorization about technical features and the reporting of technical, environmental, and social aspects. The results of the analysis revealed that the companies rarely described the environmental state of the site, even less frequently adopting quantitative indicators. “Soil contamination”, “biodiversity”, “waste production”, “risk of environmental accidents”, “water pollution and flow management”, and “noise emissions” were the aspects considered most significant. No correlation was found among the significance of an aspect, the number of indicators used to describe the associated impacts, and the number of objectives set for reducing those impacts. “Biodiversity” was mostly described through irrelevant indicators (i.e., total site area) and 76% of the allocated budget was assigned to technical aspects without a clear connection with any environmental improvement. In particular, the specific impacts on the aquatic ecosystems were scarcely reported, mitigation measures were rarely mentioned and with few details. In conclusion, the results of the study highlight the need for specific guidelines, directed to the HP sector, for effectively reporting the environmental performances and the effectiveness of the adopted Environmental Management Systems, while providing valuable information to policymakers and researchers.
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