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Considering the current geopolitical situation that has hindered the gas supply gas from Russia, Europe’s main supplier, it is necessary to find alternative routes to guarantee the Italian gas stocks in winter at a reasonable cost. Such energetic strategies should consider the environmental sustainability of the different available options, fitting the targets of the EU environmental policy. With the aim of supplying a quantitative tool to support the European green transition, this paper reports the entire life cycle assessment (LCA) of three different options for the production and supply of natural gas/methane in Italy: the production of biomethane from biogas (considering a real-scale plant in Italy), the use of liquefied natural gas (LNG) supplied by Qatar by vessel, and the use of compressed gas delivered from Algeria via pipeline. The application of the LCA standardized method allowed for the quantification of the environmental benefit provided by the first option, against all the considered impact categories, thanks to a combination of several advantages: (a) its low-impact anaerobic production, (b) its exploitation of a waste product from the food/agriculture industries, and (c) its production of valuable by-products, which can be considered environmental credits. The results proved the possible environmental gain resulting from an integrated energy supply system that would be able to enhance the economic fabric of specific areas.

The work presented here focused on the extraction of gold (Au), silver (Ag) and palladium (Pd) from electronic waste using a solution of ammonium thiosulfate. Thiosulfate was used as a valid alternative to cyanide for precious metal extractions, due to its non-toxicity and high selectivity. The interactions between sodium thiosulfate, total ammonia/ammonium, precious metal concentrations and the particle size of the waste printed circuit boards (WPCBs) were studied by the response surface methodology (RSM) and the principal component analysis (PCA) to maximize precious metal mobilization. Au extraction reached a high efficiency with a granulometry of less than 0.25 mm, but the consumption of reagents was high. On the other hand, Ag extraction depended neither on thiosulfate/ammonia concentration nor granulometry of WPCBs and it showed efficiency of 90% also with the biggest particle size (0.50 < Ø < 1.00 mm). Pd extraction, similarly to Au, showed the best efficiency with the smallest and the medium WPCB sizes, but required less reagents compared to Au. The results showed that precious metal leaching is a complex process (mainly for Au, which requires more severe conditions in order to achieve high extraction efficiencies) correlated with reagent concentrations, precious metal concentrations and WPCB particle sizes. These results have great potentiality, suggesting the possibility of a more selective recovery of precious metals based on the different granulometry of the WPCBs. Furthermore, the high extraction efficiencies obtained for all the metals bode well in the perspective of large-scale applications.

When environmental conditions change, microalgae can modulate the size of their macromolecular pools and their elemental composition in order to accommodate their nutritional and energetic demands....

The contamination of coastal marine sediments with heavy metals (HMs) is a widespread phenomenon that requires effective remediation actions. Bioremediation based on the use of bacteria is an economically and environmentally sustainable effective strategy for reducing HM contamination and/or toxicity in marine sediments. However, information on the efficiency of marine-derived fungi for HM decontamination of marine sediments is still largely lacking, despite evidence of the performance of terrestrial fungal strains on other contaminated matrixes (e.g., soils, freshwater sediments, industrial wastes). Here, we carried out for the first time an array of parallel laboratory experiments by using different combinations of chemical and microbial amendments (including acidophilic autotrophic and heterotrophic bacteria, as well as filamentous marine fungi) for the bioremediation of highly HM-contaminated sediments of the Portman Bay (NW Mediterranean Sea), an area largely affected by long-term historical discharges of mine tailings. Our results indicate that the bioleaching performance of metals from the sediment is based on the addition of fungi (Aspergillus niger and Trichoderma sp.), either alone or in combination with autotrophic bacteria, was higher when compared to other treatments. In particular, fungal addition allowed obtaining bioleaching yields for As eight times higher than those by chemical treatments and double compared with the addition of bacteria alone. Moreover, in our study, the fungal addition was the only treatment allowing effective bioleaching of otherwise not mobile fractions of Zn and Cd, thus overtaking bacterial treatments. We found that the lower the sediment pH reached by the experimental conditions, as in the case of fungal addition, the higher the solubilization yield of metals, suggesting that the specific metabolic features of A. niger and Trichoderma sp. enable lowering sediment pH and enhance HM bioleaching. Overall, our findings indicate that fungi can be more effective than acidophilic autotrophic and heterotrophic bacteria in HM bioleaching, and as such, their use can represent a promising and efficient strategy for the bioremediation of marine sediments highly contaminated with heavy metals.

An innovative cryo-mechano-hydrometallurgical process (named LIBAT) was demonstrated at pilot scale for the treatment of EOL lithium primary batteries with chemistry Li(0)-MnO2. The process allowed the recycling of steel scraps from external cases after cryomechanical dismantling, and the recovery of Mn and Li products after hydrometallurgical processing. During demonstration activities, about nine tons of batteries were treated in the cryomechanical section, and one ton of black mass was treated in the hydrometallurgical section for the recovery of Mn hydroxides and Li2CO3. The environmental impacts of the process were evaluated in comparison with an innovative pyrometallurgical approach allowing Li recovery, confirming the benefits of the proposed process due to a reduction in energy consumption. Process simulations were performed considering different mixture feeds (only Li primary, or mixture with Li-ion batteries) and process options (only the cryomechanical section of the integral process) to assess the lower limits of potentiality that would ensure economic sustainability.

Acetic acid is an organic acid of great importance globally and the demand of this product is currently increasing. The production of this acid has consequently aroused more and more interest over the years, especially for more sustainable processes. From a biological point of view, acetic acid can be produced by acetogenesis using inorganic substrates like CO2 or CO (with acetogenic bacteria) and aerobic fermentation (with acetic acid bacteria or fungi). With the aim of investigating the progress of technological innovation, the methodology applied by this review was an analysis of the international patents with the Espacenet platform, which ensured a worldwide invention overview. Another criterion was the selection of a precise period of time, from 1990 to 2020. A patent review is able to create an overview of the inventions designed for the real scale implementation, providing a whole picture of the state of the art of the technological innovation change. In addition, the most representative works of literature, that consider the influence of operating conditions (T, pH, oxygenation), have been analysed for each process. The present review, with an innovative approach focused on the technological innovation change, highlighted the ongoing interest for acetic acid bioproduction by acetogenic and acetic acid bacteria. The number of patents related to acetic acid bacteria was consistent also in the past years, but recently the interest is moving forward the utilization of genetic engineering (36% of the patents) and new substrates, like agriculture waste (26% of the patens), responding to circular economy principles. On the other hand, the acetic acid production by acetogenic bacteria is most recent, with over the 90% of the patents developed in the last 10 years. In this case the interest is mainly focused on the use of synthesis gas as substrate, that could increase the process sustainability.

One of the most significant effects of an earthquake is the production of a huge amount of waste. An incorrect management of the rubbles causes relevant environmental damages, economic losses and a psychological impact for the population. In this context, the present manuscript assesses different strategies of waste management, estimating the carbon footprint and the economic impact, in order to define the best choices. Overall, different management options can be applied, that have different costs and impacts on the environment: a temporary storage site could be used, rubbles can be treated through different technologies (either simple crushing or advanced refining), and the treatment can be carried out at different distances from the site of the event. The environmental impact assessment evidenced the importance of an in-situ pre-treatment of the rubbles and of an enhanced refining, addressed at the achievement of high quality inert. On the other hand, the economic analysis suggests that the best option is to transport everything to the treatment site, and to carry out a simple treatment of the rubbles. Consequently, our assessment resulted in conflicting conclusions, where an enhanced treatment of the rubbles is positive, from an environmental point of view, but negative, for the increase in the management costs. The economic criteria are currently pushing any decision taken by the emergency managers; however, the environmental load may have a long-term effect with even more significant economic consequences, and it cannot be neglected.

This study compared the sustainability of six alternatives for the treatment of industrial wastewater from a gasifier, considering both environmental and economic aspects by the approaches of: uses Life Cycle Assessment (LCA) and Life Cycle Cost (LCC). The processes have been developed under the zero liquid discharge approach and included a chemical removal of pollutants by using Fenton and neutralization, evaporation and crystallization to concentrate salts and stripping for the removal of ammonia from distillate of evaporation step and recover water useful for industrial reuses. The scenarios differed for the type of utilities used for the operation (steam and hot water from thermal waste) and from an optimization of the crystallization that provided a reduction of the amount of waste and an energy recovery from distillate. LCA indicated that the six scenarios produced comparable results, since the common chemical treatment (raw material and waste disposal) causes the highest contribution. The optimal scheme used hot water as utilities and had an optimization of the crystallization section (scenario B2), this options allowed a decrease of emission to air of 25% and reduction of 15% of deposited goods. Scenario B2 is much more financially attractive than the other proposed treatment, having a total cost of 123 €/t, with a reduction of 17% respect to the current disposal of 150 €/t. LCA and LCC results prove the effectiveness of thermal waste use as utilities for the wastewater treatment operations and the optimization of crystallization unit is the most environmentally and economically favourable alternative.

The construction and building field represents a key sector for the recent Circular Economy Action Plan (March 2020). Therefore, the production of low impact materials represents an essential step towards the implementation of a sustainable market. In this regard, the present paper focused on the production of painting wooden products for interior design. These industrial processes include an essential phase consisting of the reduction of odor emissions, which produce negative impacts on the environment and a persistent annoyance for the population close to the facilities. The main cause of the odor emissions in wood painting manufacturing is the production of volatile organic compounds (VOCs). In this context, the present research aimed to develop an innovative process able to combine the use of lower impact paints with a more efficient UV system for the abatement of the emissions.

The mobile phone is a fast-growing E-waste stream that includes hazardous substances and valuable metals. Smartphone touch screens (SPTS) contain a considerable amount of critical metals, such as indium and strontium that can be recovered from end of life devices as a secondary resource. Bioleaching is an emerging and environmentally friendly method for metal recovery from electronic waste. In the present study, bioleaching was assessed for the extraction of indium and strontium from organic light emitting diode type smartphone touch screens. A statistical approach based on the response surface methodology was successfully applied. The effects of influential variables: pH, ferrous sulfate, elemental sulfur, and solid content and their interactions on indium and strontium recovery using adapted Acidithiobacillus ferrooxidans were evaluated. Under optimum conditions (ferrous sulfate: 13.0 g/L; solid content; 3.0 g/L; elemental sulfur: 5.6 g/L; and initial pH of 1.1), a complete indium extraction was observed, with a concentration in solution of about 200 mg/L indium. As concerns strontium, a 5% extraction efficiency was observed, which, even if quite low, resulted in a relatively high strontium concentration in solution, around 3000 mg/L, due to its high content in the solid (2%). This work opens new perspectives in the application of clean technologies for the extraction of valuable metals, such as indium and strontium from smartphone screens. [Image: see text]

Citric acid is considered one of the most valuable weak organic acids on the market and its production by biotechnological approaches is a very interesting topic. Despite the related scientific research, the literature still lacks a state of the art for the technological innovation change, necessary for a study of the inventions designed for real scale implementation. In this context, the present review looks to account for more than 100 worldwide patents (1929–2018), necessary for the identification of the innovative markets and the most promising fields for economic investments. This deepened study identified an increasing invention number, combined with the current worldwide citric acid export flows, with China as the leader (with an economic contribution of 75%, in 2017). In order to satisfy the requests of the market which has moved toward a circular economy, the possibility to use waste substrates represents one of the main options considered in the recent patents. The discussion highlights the sustainability improvement, achieved by the conversion from a submerged technology to a solid-state fermentation (koji process). The listed results are essential for both a scientific audience and the stakeholders involved in citric acid production, in order to have a complete and updated overview of this topic.

Large amounts of waste debris occur in urbanised areas when heavy rain on local geology generates flooding and landslides. Improved understanding of disaster waste management helps to support future strategies. This study aims to find management solutions that are environmentally and economically sustainable, hypothesizing three different options. There are many variables which influence the environmental impact and the operational cost. The distances between the areas of interest and the management site, the extent of a first manual sorting carried out by citizens, the economic load of each involved step. Overall, both the environmental and the economic analysis confirmed the usefulness of the non‐advanced option, which includes a temporary debris storage site for a preliminary shredding. On the other hand, the impact due to a possible biological treatment is not balanced by the advantage of the further volume decrease. The article shows a simple analysis schema, easily adaptable to different geographical context, is useful as supporting tool for the decision makers in flood emergency scenarios.

In the last few decades, challenges of the aquatic environment have been dramatically changed in terms of magnitude of disturbances or types of hazards, along with the rise of new scientific and technological opportunities. In addition to the traditional (legacy) chemicals like metals or organic chemicals (including PAHs, PCBs and dioxins), emerging pollutants such as endocrine disruptors (EDCs), pharmaceuticals and microplastics are examples of worrying stressors for health of aquatic organisms and ecosystems. These compounds, introduced by different environmental sources and having a wide distribution, are absorbed by several species causing potential deleterious effects. The challenges of such pollutants will be discussed focusing on (i) new detection strategies, (ii) mode of action, (iii) ecological risk assessment and (iv) implementation of mitigation actions, to reduce the contaminant impact in terms of health care costs and maintenance of biodiversity. Sustainable and ecologically compatible methods and strategies for the reclamation of aquatic sediments contaminated with organic pollutants and toxic metals will also be described. Such knowledge will foster the reduction of use or release of many hazardous substances, together with providing insights on the early warning detection of chemical harmful agents within an environmental monitoring and security application program. Based on this knowledge, in this review we attempted to describe the approaches that are taken by research groups with different backgrounds operating at Universita Politecnica delle Marche.

The biosorption capacities of dried meal and a waste product from the processing for biostimulant extract of Ascophyllum nodosum were evaluated as candidates for low-cost, effective biomaterials for the recovery of indium(III). The use of indium has significantly grown in the last decade, because of its utilization in hi-tech. Two formats were evaluated as biosorbents: waste-biomass, a residue derived from the alkaline extraction of a commercial, biostimulant product, and natural-biomass which was harvested, dried and milled as a commercial, “kelp meal” product. Two systems have been evaluated: ideal system with indium only, and double metal-system with indium and iron, where two different levels of iron were investigated. For both systems, the indium biosorption by the brown algal biomass was found to be pH-dependent, with an optimum at pH3. In the ideal system, indium adsorption was higher (maximum adsorptions of 48 mg/g for the processed, waste biomass and 63 mg/g for the natural biomass), than in the double metal-system where the maximum adsorption was with iron at 0.07 g/L. Good values of indium adsorption were demonstrated in both the ideal and double systems: there was competition between the iron and indium ions for the binding sites available in the A. nodosum-derived materials. Data suggested that the processed, waste biomass of the algae, could be a good biosorbent for its indium absorption properties. This had the double advantages of both recovery of indium (high economic importance), and also definition of a virtuous circular economic innovative strategy, whereby a waste becomes a valuable resource.

This work presents a review of the international patents dealing with printed circuit board (PCB) recycling. PCBs are present in the majority of electric and electronic devices, and when the appliances reach their end-of-life phase, they need to be properly handled for the presence of valuable and hazardous materials. Many technologies have been developed and reviewed by the scientific community. However, the literature still lacks of a review of international patents, important to understand the technological innovation in this field. For this purpose, the current status of the international patents dealing with PCB recycling since the 1990s is presented. The main technologies for the mechanical treatment, the metal recovery and purification, the non-metal fraction exploitation are described and reviewed. As a whole, the present analysis is fundamental for the effective boost of a circular economy approaches.

The geomorphology of the Italian territory causes the incidence of many disasters like earthquakes and floods, with the consequent production of large volumes of waste. The management of such huge flows, produced in a very short time, may have a high impact on the whole emergency response. Moreover, historical data related to disaster waste management are often not easily accessible; on the other hand, the availability of data concerning previous events could support the emergency managers, that have to take a decision in a very short time. In this context, the present paper analyses four relevant recent case studies in Italy, dealing with disaster waste management after geologic and hydrologic natural events. Significant differences have been observed in the quantity and types of generated wastes, and, also, in the management approach. Such differences are mainly associated with the kind of disaster (i.e. earthquake vs. flood), to the geographical location (i.e. internal vs. coastal area), to the urbanisation level (i.e. industrial vs. urban). The study allowed the identification of both strengths and weaknesses of the applied waste management strategies, that represent “lessons to learn” for future scenarios. Even though it deals with Italian case studies, this manuscript may have a high impact also at international level, making available for the first-time emergency waste management data, that are considered an indispensable support for decision makers.

The growing production of green technologies (such as electric vehicles and systems for renewable electricity production, e.g., wind turbine) is increasing the rare earth element (REE) demands. These metals are considered critical for Europe for their economic relevance and the supply risk. The end-of-life permanent magnets are considered a potential secondary resource of REEs thanks to their content of neodymium (Nd), praseodymium (Pr) or dysprosium (Dy). The scientific literature reports many techniques for permanent magnet recovery. This work used a life cycle assessment (LCA) to identify the most sustainable choice, suggesting the possible improvements to reduce the environmental load. Three different processes are considered: two hydrometallurgical treatments (the first one with HCl and the other one with solid-state chlorination), and a pyrometallurgical technique. The present paper aims to push the stakeholders towards the implementation of sustainable processes for end-of-life permanent magnet exploitation at industrial scale.

The spent light emitting diode (LED) lamp is a new type of electronic waste contains the large amount of valuable metals. In this study, a novel green hybrid acidic-cyanide bioleaching process was developed for the high efficiency recovery of valuable metals from spent LED lamps. The spent LEDs were bio-pretreated using biogenic ferric produced by Acidithiobacillus ferrooxidans to efficiently harvest all base and heavy metals, 93% Sn, 94% Ni, 80% Cu, 68% Al, 60% Ga, 51% Pb, 46% Cr, and 35% Fe were leached. Then the bio-pretreated residue was bioleached by Bacillus megaterium (B. megaterium). Under optimum conditions (pH 7; glycine 2.5 g/L; L. methionine 10 g/L), 15 mg/L cyanide was produced by B. megaterium in short time of 14 h. At 10 g/L bio-pretreated spent LED, under direct hybrid bioleaching, a 47% gold extraction efficiency was observed after 36 h. The better performance of direct hybrid bioleaching suggests the important role of extracellular polymeric substances (EPS) and the continuous production of CN−. Compared to single cyanide bioleaching with un-pretreated LEDs, the amounts of metals recovered through hybrid direct bioleaching were significantly high; 93% Au, 91% Ag, 98% Ni, 87% Cu, and 84% Ga were leached after 4 d. This study developed an approach for the efficient recycling of spent LEDs that will result in a huge economic interest and better environmental performance.

Acidophilic S-oxidising bacteria isolated from sulphur-rich deep caves (Frasassi, Italy), characterised by relatively low temperature, were tested for their ability to mobilise (semi-)metals from contaminated sediments. Sediment samples from two commercial Italian seaports were used to set up bioleaching experiments. The effect of different growth substrates was also investigated. Our experiments revealed that S-oxidising bacteria isolated from Frasassi caves have a high potential to remove As from contaminated marine sediments, as never reported before. Although As solubilisation efficiency was quite low (i.e. about 30%), only a small amount of As was associated with non-residual fractions of the sediment. On the contrary, the solubilisation efficiencies of Zn and Ni (20% and 10%, respectively) were lower than those previously obtained by the use of other acidophilic bacteria and mainly influenced by the experimental conditions rather than by the presence of the S-oxidising bacteria. Results pres...

The strong growth of the electrical and electronic equipment production combined with its short lifespan are causing the production of a significant amount of waste to treat. In particular, the present paper focuses on end-of-life liquid crystal displays (LCDs) for their significant content of valuable materials, like plastic, glass and metals that could be recovered after dismantling. In the recent literature, traditional LCD recycling processes are combined with innovative treatments, which allow to recover critical raw materials, such as indium. In this context, we have evaluated the environmental impact of four different strategies of end-of-life LCD management: the disposal in landfilling sites, the incineration, the traditional recycling treatment and an innovative process also addressed to the recovery of indium. The traditional recycling treatment resulted to be the best scenario for the environment. Indeed, a life cycle assessment study gave following environmental burdens (if negative they are credits): 18, 81, −68, −60 kg CO2-equiv. and 0.08, 0.01, −0.25, −0.18 mol H+-equiv., for the four scenarios in the categories of global warming and acidification, respectively. The limit of the variability of LCD composition was overcome including additional literature data in the study. In order to improve the innovative process sustainability, a system of water recirculation was optimized with a consequent impact decrease of 35% in the global warming category. Nevertheless, this action should be combined with an increase of indium concentration in the panel because the low metal content represents the bottleneck of the overall approach. In this regard, a sensitivity analysis showed that an increase of at least five times in indium concentration in the waste is needed to observe an advantage of the innovative vs the traditional recycling process, when the impact category of climate change is considered. As a whole, the life cycle assessment was confirmed as a key tool for the choice of the best option of WEEE management.

End-of-life liquid crystal displays (LCD) represent a potential source of secondary raw materials for their relevant content of valuable materials, like plastics and metals. Furthermore, the combination of traditional and innovative recycling processes allows the recovery of indium, defined as critical raw material by European Commission. In this context, we have evaluated the environmental impacts of different management scenarios: incineration, the current recycling strategies and more innovative options addressed at indium recovery. Currently, end-of-life monitors are recycled through two different approaches: either manual dismantling, that allows the processing of homogeneous LCD flows, or mechanical treatment, where heterogeneous flows of monitor are processed, to guarantee the continuous operation of the high capacity plant. Such difference does not allow a direct comparison among the two current recycling approaches; however, the three scenarios (incineration vs. current recycling vs. innovative strategies) were assessed for each one of the two recycling approaches. The advantage of the materials recovery was confirmed in both the cases by a life cycle assessment, which showed a whole environmental credit in the range 60-130 kg CO2-equiv., mainly due to the avoided primary production of recovered fractions. Nevertheless, the low indium concentration and the impacts of its recovery make the innovative recycling disadvantageous, if compared to the traditional one. A metal upgrading in the panel, feasible through physical treatments, can overcome this criticality, in the case of manual dismantling. The present study confirmed the life cycle assessment as support tool for the definition of the best option of waste management.

End of life photovoltaic panels of different technologies (poly crystalline Si, amorphous Si, and CdTe) were treated mechanically in pilot scale by single shaft shredder minimizing the production of fine fractions below 0.4 mm (18% weight). Grounded material was sieved giving: an intermediate fraction (0.4-1 mm) of directly recoverable glass (18% weight); a coarse fraction (which should be further treated for encapsulant removal), and fine fractions of low-value glass (18%), which can be treated by leaching for the removal of metal impurities. Encapsulant removal from coarse fraction was successfully performed by solvent treatment using cyclohexane at 50 °C for 1 h giving high-grade glass (52% weight), which can be reused for panel production. Experimental results of solvent treatment were compared with those from thermal treatment by economic analysis and Life Cycle Assessment, denoting in both cases the advantages of solvent treatment in recovering high-value glass.

A kinetic study of the process for the copper leaching from printed circuit board, by Fe3+, was reported. A mathematical model, supported by experimental data, considered the mechanisms that control the reaction (chemical reaction, particle or liquid film diffusion). The kinetic of the chemical reaction was studied by two models (pseudo-first and pseudo-second order), with a calculated activation energy of 18-25 kJ/mol. Nevertheless, both the models showed two criticalities: the Cu concentration dependence from the 〖Fe〗_0^(3+) and the 〖Fe〗^(3+) reducing rate. Therefore, a new mathematical model was proposed to predict the recoverable Cu from PCB, by three parameters: the Cu content, the Fe3+ concentration and the temperature. The high reliability of the model makes it an essential tool for the urban mining process optimization.

The agriculture sector produces significant amounts of organic residues and the choice of the management strategy of these flows affects the environmental sustainability of the sector. The scientific literature is rich with innovative processes for the production of bio-based products (BBP) from agriculture residues, aimed at the implementation of circular economy principles. Based on literature data, the present paper performed a life cycle assessment and assessed the environmental sustainability of five processes for the exploitation of rice and wheat straw, tomato pomace, and orange peel. The analysis identified as significant issues the high energy demand and the use of high impact organic solvent. The comparison of BBP with conventional products showed higher environmental loads for the innovative processes that used organic residues (except for rice straw case). The obtained results do not want to discourage the circular strategy in the agriculture sector, but rather to draw the attention of all stakeholders to the environmental sustainability aspects, focusing on the necessity to decrease the electricity demand and identify ecological agents to use in BBP manufacturing, in agreement with the most recent European policies.

This study uses Life Cycle Assessment (LCA) and Life Cycle Cost (LCC) to compare three process design alternatives for treating wastewater from galvanic industry. The proposed processes have been developed in according to a zero-liquid discharge, ZLD, approach and included reverse osmosis for the concentration, evaporation and crystallization of salts, mainly calcium chloride. The various scenarios differ for the type of utilities used for the operation (steam and as alternative hot water from thermal waste) and from an optimization of the crystallization step that provided an energy recovery from distillate. Results show that by using thermal waste as utilities for the operation of evaporation, crystallization and the optimization of crystallization unit is the most environmentally and economically favourable alternative.

Coastal sediments subjected to high anthropogenic impacts can accumulate large amounts of polycyclic aromatic hydrocarbons (PAHs) and metals, demanding effective and eco-sustainable remediation solutions. In this study, we carried out bioremediation experiments on marine sediments highly contaminated with PAHs and metals. In particular, we investigated the effects of biostimulation (by the addition of inorganic nutrients), bioaugmentation (by the addition of fungi belonging to Aspergillus sp.) and microbial fuel cell-based strategies on PAH degradation and on changes in metal partitioning. Results reported here indicate that all biotreatments determined a significant decrease of PAH concentrations (at least 60%) in a relatively short time interval (few weeks) and that biostimulation was the most effective approach (>90%). Biostimulation determined a faster degradation rate of high than low molecular weight PAHs, indicating a preferential biodegradation of specific PAH congeners. At the same time, the biotreatments changed the partitioning of metals, including their solubilization, suggesting the need of parallel environmental risk assessment. Our findings also suggest that ex situ biotreatments can have a lower carbon footprint than current management options of contaminated sediments (i.e., landfill disposal and/or disposal in confined aquatic facilities), but integration with other strategies for metal removal (e.g. through bioleaching) from sediments is needed for their safe re-use. Overall, results presented here provide new insights into the development of effective and eco-sustainable bioremediation strategies for the reclamation of highly contaminated marine sediments.

Polymetallic nodules on abyssal seafloor represent a major reservoir of valuable metals. Here we analysed fungal-mediated leaching of metals from nodules collected at ca. 5000 m depth in the Clarion-Clipperton Fracture Zone of the Pacific Ocean. The bioleaching efficiency of Aspergillus and a mixed cultures of A. niger and Trichoderma sp., at different growing conditions, were investigated and compared to chemical treatments using citric acid. 11 days of treatment with A. niger growing in optimal medium conditions, produced the best result with the extraction of more than 80% of Mn, Cu, Ni, and 70% and 30% of Co and Fe, respectively. Our findings suggest that biotechnological processes can be a sustainable approach in terms of carbon footprint reduction compared to chemical strategies. Results presented here provide the potential of fungal-mediated leaching and pave the way for the development of effective and eco-sustainable biotechnologies for the metal recovery from deep-sea nodules.

According to the WEEE European directives, efforts must be undertaken to reuse or safely dispose liquid crystal displays (LCD) waste, however no practical process was reported yet, although it is possible to recover glass, plastic and precious metals, in particular indium. Indium is one of the elements included by the European Commission in the list of 20 raw materials critical for economic importance and high supply risk (European Commission, https://ec.europa.eu/ growth/tools-databases/eip-raw-materials/en/system/files/ged/79%20report-b_en.pdf [1]). The work aims to valorize LCD scraps after indium recovery with low cost applications both economically and environmentally speaking. Applications have been explored by many researchers, although most focused only on the use of glass powder waste LCD to design concrete. This work deals the use of LCD scraps as it is after cross-current leaching of indium with H2SO4. The experimental work consists of scraps characterization, washing procedure optimization to remove residual acid, mortar production, performance testing, and life cycle assessment (LCA). The results show that LCD scraps exhibit little or no pozzolanic activity. This delay on reactivity can be ascribed to organic residues that prevent the pozzolanic reaction and/or to a lower fineness than that typical of binders or fillers. For this reason the actual investigation focuses to exploit the waste as partial replacement of traditional aggregates. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

In 2014, the European Union identified 20 raw materials critical for economic importance and high supply risk. Indium, used in several innovative technologies, is among such critical raw materials. Generally, it is mined as a by-product of zinc from a mineral named sphalerite, with a concentration between 1 and 100 ppm. Currently, the largest producer of indium is China and about 84% of the worldwide indium consumption is used for liquid crystal display (LCD) production, in particular to form an indium-tin-oxide (ITO) film with transparent conductor properties. The fast evolution of LCD technologies caused a double effect: the growth of indium demand and an increase of waste electrical and electronic equipment (WEEE). Considering these two factors, the aim of this study is to make the end-of-life LCDs a secondary indium resource. With this purpose, an indium recovery process was developed carrying out an acidic leaching, followed by a zinc cementation. The first step allowed a complete indium extraction using 2M sulfuric acid at 80 °C for 10 min. The problem of low indium concentration in the scraps (around 150 ppm) was overcome using a cross-current configuration in the leaching phase that allowed an increase of metal concentration and a decrease of reagents consumption. An indium recovery higher than 90% was obtained in the final cementation step, using 5 g/L of zinc powder at pH 3 and 55 °C for 10 min. Considering its high efficiency, this process is promising in a context of circular economy, where a waste becomes a resource. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Indium is a critical raw material with economic importance and high supply risk. In the present study, we recovered indium by means of cementation from a leaching solution of waste liquid crystal display panels. Cementation with zinc powder was optimized through the investigation of the effects of different variables (zinc concentration, pH, cementation time) on cementation efficiency and purity of the solid product. Almost all the indium present in the leaching solution passed to the solid phase when cementation was performed with a low (2–5 g/L), a medium (15–20 g/L) and a high (100 g/L) concentration of zinc, at pH 3. At pH 2, a complete cementation was obtained only with the highest concentration of zinc. Moreover, the highest purity of the indium product (62% indium percentage in the solid product, calculated in the 4-metal system indium-aluminum-calcium-iron) was achieved after a cementation of 10 min, whereas the presence of impurities increased with time. An empirical model successfully fitted the experimental data and suggested that the highest purity of the cemented product was expected at pH 2. A quantification of the environmental impact of the process for indium recovery from end-of-life liquid crystal display panels was also carried out through a life cycle analysis approach, and it outlined that relevant benefits to the environment were obtained thanks to the recovery of indium from waste electric and electronic equipment. The results obtained in the present study are promising since this is the first time that cementation was applied to a leaching solution of waste liquid crystal display panels. In this paper we found that indium cementation took place also with low concentrations of zinc at pH 3, allowing important reagent saving. Investigations in progress are aimed at increasing the purity of indium and at improving the environmental sustainability of the process. The approach presented here is considered extremely useful in the frame of urban mining strategies. It can help ensure progress towards sustainable societies, encourage industrial innovation of the recycling companies and the implementation of cleaner processes.

The growing production and use of electric and electronic components has led to higher rates of metal consumption and waste generation. To solve this double criticality, the old linear management method (in which a product becomes waste to dispose), has evolved towards a circular approach. Printed circuit boards (PCBs) are the brains of many electronic devices. At the end of their life, this equipment represents a valuable scrap for the content of base metals such as Cu and Zn (25 and 2 wt %, respectively) and precious metals such as Au, Ag, and Pd (250, 1000, and 110 ppm, respectively). Recently, biotechnological approaches have gained increasing prominence in PCB exploitation since they can be more cost-efficient and environmentally friendly than the chemical techniques. In this context, the present paper describes a sustainable process which uses the fungal strain Aspergillus niger for Cu and Zn extraction from PCBs. The best conditions identified were PCB addition after 14 days, Fe3+ as oxidant agent, and a pulp density of 2.5% (w/v). Extraction efficiencies of 60% and 40% for Cu and Zn, respectively, were achieved after 21 days of fermentation. The ecodesign of the process was further enhanced by using milk whey as substrate for the fungal growth and the consequent citric acid production, which was selected as a bioleaching agent.

The circularity represents the key strategy of the modern economy, where the waste becomes a raw material, ready to be reprocessed for a second life. In this context, the main aim of the present work was the development of a sustainable process for the recovery of Cu and Zn from end-of-life printed circuit boards (PCBs). The exploitation of this hazardous waste produces a double effect: the recovery of metals, suitable for the current metal market, and the avoided disposal of scraps produced worldwide. The process allowed to exceed the limits of several approaches reported in the literature, mainly due to the highest consumptions (both energy and raw materials) and the loss of Zn content. The best identified conditions, suitable for the treatment of both chemical and bio- leach liquor included: the Fe precipitation with sodium hydroxide, followed by the Cu cementation with Zn (Zn/Cu molar ratio of 1.1) and a final Zn precipitation with oxalic acid (O.A./Zn molar ratio of 1.5). The metals showed recovery efficiencies higher than 95% and purities up to 95%. An efficient recirculation system contributes to the sustainability growth, as confirmed by the carbon footprint assessment, towards the implementation of a zero waste treatment. Future perspective should include the further exploitation of the residue, rich in precious metals.

The increase of waste from electric and electronic equipment has pushed the research towards the development of high sustainability treatments for their exploitation. The end-of-life printed circuit boards (PCBs) represent one of the most significant waste in this class. The interest for these scraps is due to the high Cu and Zn content, with concentrations around 25% and 2% respectively, combined with further precious metals (e.g. Au, Ag, Pd). Currently, the most common approaches developed for PCBs recycling include pyrometallurgical and hydrometallurgical treatments. On the other hand, biohydrometallurgical strategies are gaining increasing prominence, for the possibility to decrease both the environmental and the economic costs. Nevertheless, these techniques show the main limit due to the possibility to treat low quantities of waste, which makes unsustainable the further scale-up. To overcome this criticality, the present paper introduces an innovative bioleaching process carried out by Acidithiobacillus ferrooxidans (At. ferrooxidans) and Leptospirillum ferrooxidans (L. ferrooxidans). The developed technology allows to reach high PCB concentration, up to 5% (w/v), thanks to a high efficiency two-step design, able to reduce the metal toxicity on the bacteria metabolism. The treatment uses the ferric iron generated by bacterial oxidation, as oxidant, to leach Cu and Zn from PCBs. The possibility to overcome the solid concentration criticality is combined with high yield of 94% and 70% for Cu and Zn, respectively. The best selected conditions involve the At. ferrooxidans bacteria use at: 30 °C, solid concentration of 5% (w/v), 10 g/L of Fe2+, time of treatment 9 days. The experimental results are further enhanced by the carbon footprint assessment which proved the environmental advantage, compared to both the reference chemical treatment through ferric iron and literature processes (hydrometallurgical and bioleaching approaches). The analysis explained as the PCBs concentration in the solution allows to decrease the bioreactor size with the consequent reduction of energy and raw material demand. This benefit can be translated into a 4 times reduction of the CO2-eq./kg treated PCB emissions, compared to the best bioleaching processes, reported in the literature.

A huge quantity of end-of-life liquid crystal displays (LCD) is collected, every year, around the world. Nowadays, this equipment is disassembled, for the removal of hazardous components (e.g. the backlight fluorescent lamps), and the resulting panel is stored. The reason is the significant content of valuable fractions (e.g. glass, metals and liquid crystals) and the lack of a recycling process, sustainable from an economic and an environmental point of view. Considering the relevance of this critical issue, the scientific community focused on the development of different recovery strategies, summarized in several available reviews. Nevertheless, the literature has not yet dealt with the technological innovation aspect. With the aim of filling this gap, the present review presents the international patents about LCD recycling, from 1999 to 2017, using the Espacenet platform, that has access to all the most relevant patent databases worldwide. The inventions include a first waste disassembling, followed by the classification of the target fractions and the recovery of metal (e.g. indium, indium tin oxide) and non-metal (e.g. glass, polarizing film, liquid crystal) components.

Rapid technological development has caused considerable growth of the liquid crystal display (LCD) market. Considering their average lifetime of between 3 and 8 years, the management of end-of-life LCDs represents a modern critical issue. Nevertheless, this kind of waste could also represent a source of secondary raw materials, especially indium, a metal classified as a critical raw material by the European Commission, on the basis of supply risk. This element is present, in oxide form, in the indium tin oxide film, an optoelectronic material with characteristics of transparency to visible light, electric conduction, and thermal reflection. Currently, no commercial recycling processes are available but many researches have focused on the optimization of high-efficiency treatments, carried out at different conditions. This chapter aims to provide an overview of the hydrometallurgical approaches developed for indium recovery and the final valorization of end-of-life LCD.

European industry is dependent on the import of raw materials. The European Commission has recognized that some raw materials are crucial for the function of the European economy and show a high risk of supply shortage. This communication addresses supply and substitution options for selected critical raw materials: cobalt, niobium, tungsten, yttrium, and the rare earth elements. For each element, the most relevant data concerning mining, abundance, recycling rates and possible substitutes are summarized and discussed.​

Sediment contamination in coastal areas with high anthropogenic pressure is a widespread environmental problem. Metal contaminants are of particular concern, since they are persistent and cannot be degraded. Microorganisms can influence metal mobility in the sediment by several direct and indirect processes. However, the actual fate of metals in the environment is not easily predictable and several biogeochemical constraints affect their behaviour. In addition, the geochemical characteristics of the sediment play an important role and the general assumptions for soils or freshwater sediments cannot be extended to marine sediments. In this paper we analysed the correlation between metal mobility and main geochemical properties of the sediment. Although the prediction of metal fate in sediment environment, both forex-situbioleaching treatments andin-situbiostimulation strategies, appears to require metal-specific and site-specific tools, we found that TOM and pH are likely the main variables in describing and predicting Zn behaviour. Arsenic solubilisation/increase in mobility appears to correlate positively with carbonate content. Cd, Pb and Ni appear to require multivariate and/or non-linear approaches.

The present study deals with the management of end-of-life copper indium gallium selenide (CIGS) and cadmium telluride (CdTe) thin-film photovoltaic (PV) panels. We quantitatively compare the impacts and environmental weak points of the recycling processes of such panels, and their disposal in a landfill site. Two scenarios of recycling are considered: conventional and innovative. In the conventional recycling, the modules are crushed, glass is recovered, ethylene-vinyl acetate (EVA) is sent to thermal treatment to gain energy and the residual material is disposed of in a landfill site. Conversely, the innovative recycling option goes beyond conventional technologies and it allows to recover also selenium, indium and gallium from the CIGS panels, and tellurium from the CdTe panels. The potential impacts on the environment are similar for the conventional recycling processes of both the typologies of PV panels. Conversely, the innovative recycling of the CdTe panels creates a net production of environmental credits thanks to the recovery of valuable materials. The innovative recycling of CIGS panels has a higher impact than the recycling of CdTe panels (e.g. 2.5 vs 0.7 kg CO 2 -eq., respectively, for global warming potential). In any case, the disposal of end-of-life panels is not advantageous for the environment according to life cycle assessment. Data obtained with the recycling processes currently available suggest that the innovative recycling is environmentally beneficial only for the CdTe panels, due to the very low content of valuable elements in the CIGS panels. More effort should be directed to the development of a pre-treatment that can effectively concentrate the valuable elements. Overall, the results of this study give a quantitative basis to support the recycling of PV panels and the recovery of secondary raw materials like tellurium, indium, gallium and selenium.

The contamination of aquatic sediments with metals is a widespread environmental problem. Coastal aquatic ecosystems with low hydrodynamics need to be periodically dredged in order to maintain the navigation depth and facilitate sailing; consequently large volumes of contaminated sediments need to be managed. Conventional remediation strategies include in-place sediment remediation strategies (e.g. in situ-capping) and relocation actions; in particular, landfill disposal and dumping at sea are still widely applied. Both this options are becoming unsustainable, due to problems associated with contaminant transport pathways, the uncertainties about long-term stability under various environmental conditions, the limited space capacity, costs and environmental compatibility. Alternative approaches have received increased attention; treatment and reuse of contaminated sediments is politically encouraged, but its application is still very limited. Because of the potential human health and environmental impacts of contaminated sediment, different chemical treatments are conventionally applied for contaminated sediments before reuse in other environmental settings. Environmentally friendly techniques developed for soils and other environmental matrices have been investigated for applications with sediments. Biotechnological approaches are gaining increasing prominence in this field and they are often considered as a promising strategy for the eventual treatment of contaminated sediments. In this paper an overview of the main treatment strategies potentially available for sediment contaminated with metals is given, together with a brief overview of the issue associated with the problem of the sediment management.

This study deals with anaerobic biotreatments of sediments contaminated with toxic metals carried out in slurry reactor. The sediment samples used for the investigation came from two Italian ports, and they were mainly contaminated with inorganic compounds (zinc, nickel and chromium). The treatments were aimed at assessing the responses of the autochthonous microbial community in relation to the geochemistry of the sediments (mainly organic carbon bioavailability) and the addition of organic and inorganic substrates. It was observed that the bio-available carbon in the sediments can greatly influence microbial growth but without a significant effect on metal mobilization. By contrast, the supply of inorganic nutrients to the sediments did not have a major effect on microbial growth although important changes in metal mobility were observed. Our results provide new insights on the effects of anaerobic biotreatments on changes in metal partitioning in contaminated sediments, highlighting that, under certain conditions, an increase of metals in the more mobile fractions can occur.

The present study was aimed at the reclamation of harbour sediments contaminated with butyltin compounds (BTCs) by means of biostimulation and/or bioaugmentation experiments carried out in a 5-L slurry bioreactor. In the biostimulation experiment with inorganic nutrients, almost 50% of TBT was degraded in 20 weeks. In the bioaugmentation experiment with a microbial consortium, no significant degradation of TBT was observed. Conversely, bioaugmentation combined with biostimulation led to a decrease of ∼50% in TBT after four weeks. A simple kinetic model fitted to the experimental data of BTC concentration allowed us to estimate that 10 weeks are needed to decrease BTC contamination by 90% using a strategy based on both biostimulation and bioaugmentation, and 29 weeks for a strategy using biostimulation only. Overall, our study indicates that strategies based on biostimulation coupled to bioaugmentation can be effective in significantly reducing the concentration of BTCs over relatively short timescales.

We compared the environmental burdens in the management of end-of life cathode ray tubes (CRTs) within two frameworks according to the different technologies of the production of televisions/monitors. In the first case, CRT recycling is addressed to the recovery of the panel and funnel glass for the manufacturing of new CRT screens. In the second case, where flat screen technology has replaced that of CRT, the recycling is addressed to the recovery of the glass cullet and lead for other applications. The impacts were evaluated according to the problem-oriented methodology of the Institute of Environmental Sciences, Leiden University, Leiden, The Netherlands. Our data confirm that in both cases, the recycling treatment allows benefits to be gained for the environment through the recovery of the secondary raw materials. These benefits are higher for the “CRT technology” framework (1 kg CO2 saved per CRT) than for the “flat screen technology” (0.9 kg CO2 saved, per CRT, as the highest possible), mainly due to the high energy consumption for lead separation from the funnel glass. Furthermore, the recovery of yttrium from the fluorescent powders that are a residue of the recycling treatment would further improve the CO2 credit for both the frameworks considered, which would provide a further saving of about 0.75 kg CO2 per CRT, net of the energy and raw materials needed for the recovery. Overall, this study confirms that, even with a change in the destination of the recovered materials, the recycling processes provide a benefit for the environment: indeed the higher loads for the environment are balanced by avoiding the primary production of the recovered materials.

End-of-life liquid crystal displays (LCD) represent a possible source of secondary raw materials, mainly glass and an optoelectronic film composed of indium (90%) and tin (10%) oxides. A strong interest for indium, classified as critical raw material, pushed research towards the development of high-efficiency recycling processes. Nevertheless, a deepened study of the technological innovation highlighted that only a small number of treatments included use of whole waste. Furthermore, these processes often need high temperatures, long times, and raw materials that have a significant environmental impact. In this context, this article shows an approach developed in accordance with the &ldquo, zero waste&rdquo, principles for whole, end-of-life LCD panel recycling. This process includes preliminary grinding, followed by cross-current acid leaching and indium recovery by zinc cementation, with efficiencies greater than 90%. A recirculation system further increases sustainability of the process. To enhance all waste fractions, glass cullets from leaching are used for concrete production, avoiding their disposal in landfill sites. Considering the achieved efficiencies, combined the simple design suitable for real-scale application (as confirmed by the related patent pending), this process represents an excellent example of implementing circular economy pillars.

This study deals with laboratory-scale investigations to evaluate the efficiency of different chemical leaching agents (i.e. sulfuric, oxalic and citric acids) and bioleaching processes (based on different acidophilic bacterial strains) on the mobilisation of metals/semi-metals in contaminated harbour sediments. A simplified life-cycle assessment was also performed in order to compare the investigated strategies in terms of their main environmental impacts. The different chemical leaching agents provided different extraction efficiencies of toxic metals. Among the investigated chemical leaching agents, citric acid 0.5 M and sulfuric acid pH 2 were the most effective, with average mobilisation efficiencies of ∼30% for Zn and Cr, ∼40% for Ni, and 35 and 58% for As, under citric and sulfuric acid, respectively. Similar higher extraction efficiencies of metals were also observed in bioleaching experiments with the presence of ferrous iron. The life-cycle assessment revealed that treatments based on diluted su...