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Organic waste-to-energy (OWtE) technologies are playing a steadily increasing role in the Green Transition, thus becoming a powerful driver in the establishment of an ever more efficient and sustainable circular economy. The advantages of OWtE processes are well known: not only do they reduce the waste volumes sent to landfills or incineration plants, but also and foremost, through the energy they yield (biogenic carbon dioxide, amongst others), they reduce dependance on fossil fuels. This article gives a complete panorama of these technologies, starting from the classical methods and ending with a review of the latest modern novelties. Advantages and disadvantages of each method are highlighted, with particular focus on the formation of by-products and the relevant treatment aimed at preventing environmental pollution. Accordingly, modern techniques for increasing waste-to-energy efficiency and integrating the concept of circular economy and substitutability are analyzed from this perspective. Along with an analysis of modern scientific achievements in this area, practical examples of the implementation of technologies in European countries are given, with an emphasis on the obvious advantages, both economic and environmental. [ABSTRACT FROM AUTHOR]

Electronic waste grows globally at a rate of 5% annually, which makes electronic waste recycling (WEEE recycling) an urgent task aimed at achieving (i) environmental protection and (ii) the preservation of mineral resources through the re-introduction of strategic metals into the market. As it turns out, WEEE recycling produces further waste, called WEEE secondary waste, which still contains valuable metals such as gold, silver, and copper. This study assessed the economic viability of recovering these metals and identified the most promising targets and approaches. WEEE secondary waste produced at a plant in southern Europe was sampled and examined for this purpose. The study methods included an ANOVA (analysis of variance) and an OCCP (orthogonal central composition plan). Over 90% gold, silver, and copper extraction was achieved with hydrochloric acid leaching in sodium hypochlorite with sodium chlorite as an oxidizing agent at 60 °C. The significance of the variation in the response for each factor, calculated using the Yates algorithm, demonstrates that by excluding sodium chloride and optimizing the doses of hydrochloric acid and sodium hypochlorite, gold can be selectively recovered through the leaching process. The scenario of HCl (2.5M)/NaClO (5%) leaching results in the maximum extraction effect of Au (91.6%) at the lowest concentrations of Ag and Cu (37–44%). [ABSTRACT FROM AUTHOR]

The resistance of steel to corrosion is obtained with a number of industrial processes based on Zn galvanization. However, all these methods bear a relatively high price tag due to the cost of Zinc plates and electrolytes as well as the formation of hazardous wastewaters containing metals and acids. Wastewaters from Zn galvanization may be grouped into two main types: Mix of Rinse Water (MRW) and Spent Pickling Solutions (SPS). Ordinarily, these waters are mixed and sent for treatment by precipitation. As a result large volumes of galvanic sludge is formed, containing iron, calcium, sulphates and a relatively small quantity of zinc (

The main objective of this work was to improve the technological scheme of oil refinery wastewater treatment. Replacment of the expensive filter section in a refinery plant by coagulation in order to increase effectiveness of the process at lower cost was investigated. This research has proven that Ca(OH)2 and Al2(SO4)3 were effective in treatment of oil wastewater. Central Composite Design was applied to two factors, the Al2(SO4)3 dosage and pH. Under optimum conditions effect of removal of Turbidity did reach 100 %, Total hydrocarbons 90 % and COD 70 %. Concentration of Total hydrocarbons in wastewater after treatment were below Limits for sewerage. Prevailing mechanism for coagulation was charge neutralization, associated with deposition of positively charged aluminum hydroxide onto negatively charged particles. Applying of cogulation will let significantly reduce operating expenses up to 5,436.35 €/year, at the same efficiency, due to replacing expensive filtration processes with cost of 102,600.00 €/year.

Featured Application: The results obtained can be used to optimize the process of anaerobic bioconversion of organic waste in the Russian Federation. Anaerobic digestion (AD) is a promising option to obtain renewable energy in the form of biogas and reduce the anthropogenic impact on the environment. In recent years there has been increasing interest in using pressurized digesters to improve the quality of biogas. However, maintaining high overpressure increases the requirements for the explosion safety of digesters. Consequently, there are natural limitations in the available technologies and facilities suitable for full-scale operation. In this work, we aimed to evaluate the possibility of using overpressure in the digester to improve the efficiency of codigestion of common municipal organic waste–sewage sludge and the organic fraction of municipal solid waste. Three levels of moderate excess pressure (100, 150 and 200 kPa) were used to meet requirements of existing block-modular anaerobic bioreactors based on railway tanks, which are widely utilized for AD in the Russian Federation. There was no significant change in methane content in biogas (65% ± 3%) at different values of overpressure, hydraulic retention time (HRT) and organic loading rate (OLR). The maximum methane and energy production rates (2.365 L/(L·day) and 94.27 kJ/(L·day), respectively) were obtained at an overpressure of 200 kPa, HRT of 5 days and OLR of 14 kg VS/(m3·day). However, the maximum methane yield (202.44 mL/g VS), energy yield (8.07 kJ/g VS) and volatile solids (VS) removal (63.21%) were recorded at an overpressure of 150 kPa, HRT of 7 days and OLR of 10.4 kg VS/(m3·day). The pressured conditions showed better performance in terms of AD stability at high OLRs. [ABSTRACT FROM AUTHOR]

Discussions about whether the improvement of environmental indicators of companies has a positive or negative impact on their competitiveness (i.e., based on their economic indicators) have been conducted for a long time: environmentalists and the public insist on stricter environmental standards, and politicians, economists, and the business community are looking for a compromise between the costs of environmental protection and economic efficiency. Understanding this relationship is important for all disputing parties since two goals are simultaneously pursued: ensuring high quality of the environment, which requires unproductive costs, and obtaining good economic results. This is also important for separating environmental, economic, and political goals: is the policy of "greening" business implemented in developed countries a real fight against climate change and bad ecology, or is it used as a tool for mobilizing the electorate and hidden protectionism? Despite a large number of studies conducted in this area, the question remains open about the direction of the causal relationship: whether environmental investments lead to higher profits or simply act as indicators of firms with high financial results. This article presents a comparative analysis of methods and models for forming relationships between the environmental and economic characteristics of firms in the context of the activation of the international environmental agenda as one of the promising areas for the development of economic analysis. The authors show that the relationship between environmental regulation and competitiveness is not the same and depends on the market structure of the industry, while important problems of analysis are the presence of different approaches to defining the concepts of "competitiveness," "economic efficiency," "environmental efficiency," and "regulatory rigor," as well as the use of various indicators for their measurement, the complexity of selecting indirect indicators of environmental regulation and competitiveness, and the availability and quality of data. Furthermore,the possibilities and problems of the empirical analysis of the relationship between environmental and economic efficiency according to Russian companies and domestic statistics are studied. [ABSTRACT FROM AUTHOR]

The circular economy and maximization of environmental sustainability are increasingly becoming the vision and mission of companies competing in present-day global markets. In particular, in the energy sector, the transition from fossil fuels to renewable sources of energy has become the widespread mantra. One typical example is the deployment of devices which produce clean energy, such as solar photovoltaic panels and solar thermal panels, wind generators, tidal stream generators, wave power generators, etc. These are undoubtedly generating clean energy, but their manufacture creates hazardous by-products, the disposal of which results in increased environmental pollution. Chemical Vapor Deposition (CVD) is widely used in manufacturing of solar photovoltaic cells. In these processes, typically, crystalline silicon is precipitated from chlorosilanes, iodides, bromides and fluorides. Polluting by-products include deposition of a silicon film, formation of SiO2 powder and formation of toxic vapors of HF, SiH4 and PH3. Usually, these gaseous products are eliminated in a central scrubber, whose unwanted by-product consists in large quantities of hazardous fluorine-containing sludge. This article concerns an effective and inexpensive detoxification of fluorinated sludge, developed by the authors during research into the sludge collected from the scrubber of a PV cell manufacturing plant located in southern Italy. [ABSTRACT FROM AUTHOR]

TMAH is quaternary ammonium salt, consists of a methylated nitrogen molecule, and is widely used in the electronics industry as a developer and silicon etching agent. This substance is toxic and fatal if ingested. It can also cause skin burns, eye damage, and organ damage. Moreover, TMAH exhibits long-lasting toxicity to aquatic systems. Despite this known toxicity, the authorities currently do not provide emission limits (i.e., discharge concentrations) for wastewater by EU regulation. The current scenario necessitates the study of the processes for industrial wastewater containing TMAH. This work aims to present a successful example of the treatment process for the degradation of TMAH waste solutions of the E&S industry. Research was conducted at the pilot scale, and the process feasibility (both technical and economic) and its environmental sustainability are demonstrated. This process, which treats three exhausted solutions with a high concentration of toxic substances, is considered to be innovative. [ABSTRACT FROM AUTHOR]

According to the International Energy Agency (IEA), only a tiny fraction of the full potential of energy from biomass is currently exploited in the world. Biogas is a good source of energy and heat, and a clean fuel. Converting it to biomethane creates a product that combines all the benefits of natural gas with zero greenhouse gas emissions. This is important given that the methane contained in biogas is a more potent greenhouse gas than carbon dioxide (CO2). The total amount of CO2 emission avoided due to the installation of biogas plants is around 3380 ton/year, as 1 m3 of biogas corresponds to 0.70 kg of CO2 saved. In Russia, despite the huge potential, the development of bioenergy is rather on the periphery, due to the abundance of cheap hydrocarbons and the lack of government support. Based on the data from an agro-industrial plant located in Central Russia, the authors of the article demonstrate that biogas technologies could be successfully used in Russia, provided that the Russian Government adopted Western-type measures of financial incentives. [ABSTRACT FROM AUTHOR]

The trends of sustainable development and green agenda transform the production processes, leading industries, and regional markets, and reveal objective contradictions in ensuring the ecological safety of certain territories. This study aims to develop a methodology and assess ecological safety at aggregated system levels, taking into account natural and socioeconomic factors as well as the factor of human capital development with specification of the place of ecological safety in the concept of sustainable development. The objects of empirical research are the EAEU and CIS countries for the period 2010–2019, as well as 85 Russian regions. The scientific research toolkit is based on the methods of structural-logical, economical-statistical, and comparative analyses, and expert judgments. The concepts of sustainable development and human capital and the theory of the national school of ecological safety are analyzed using the systematic approach. The mixed methodological approach showed the interconnection of four approaches of assessing ecological safety (technogenic, environmental, institutional, resource-based). The authors developed a method for assessing ecological safety taking into account the contribution of human capital. The assessment results are typologized and grouped according to the dynamic trend. For the majority of the considered countries, changes in the level of ecological safety correlate with changes in socioeconomic indicators. The same trend is observed when considering the Russian regional formations. The contribution of human capital was recorded to a lesser extent. For several regions, the increased number of objects polluting the environment is accompanied by a decreased volume of polluting emissions into the atmosphere. [ABSTRACT FROM AUTHOR]

Typical methods for the treatment of waste pickling solutions include precipitation by alkaline reagents, most commonly calcium hydroxide. As a result, large volumes of galvanic sludge form, containing iron, calcium, sulphates, and a relatively small quantity of zinc (<20%), making Zn recovery not profitable. In summary, state-of-the-art Zn galvanization processes entail the loss of valuable metals and the irrational and expensive handling of spent pickling solutions (SPSs). The resulting conclusion is that there is room for a significant improvement in the way SPSs are treated, with the double goal of enhancing Zn galvanization methods' economic viability and achieving a lesser impact on the environment's processes. The experimental results show that it is possible to use SPS as a coagulant to treat the process wastewaters, kept separated, and added with sodium hydroxide. The results in obtaining precipitates with Zn contents higher than 40%, increasing the added advantage of making Zn recovery profitable. The results show the possibility of using SPS as a coagulant in the process of physical-chemical wastewater treatment and sodium hydroxide to obtain a precipitate with a zinc content of more than 40%. [ABSTRACT FROM AUTHOR]

This article describes the improvement of wastewater treatment in a fertilizer plant located in Central Italy (municipality of Vasto). In this facility, water is used for the removal of dust and fluorinated gases from the air. The resulting wastewater contains fluorides and phosphates in hazardous forms. Its treatment ordinarily does not result in a Zero-Liquid Discharge (ZLD) process. To achieve this purpose, several reagents were tested, focusing on the correlation linking pH, type of reagent and the effect on the separation of fluorides and phosphates from the wastewater. It was eventually found, and explained with a model, that hydrated lime at pH = 12 was so effective as a precipitating agent that phosphate and fluoride separation reached a value of 99.9%, thus allowing for reuse of the water in the plant process. Furthermore, phosphates and fluorides precipitated in a non-hazardous form, so that the material could also be recycled. In synthesis, wastewater treatment of the fertilizer plant was upgraded so that it became a ZLD process coupled with the recovery and recycling of fluorides and phosphates. [ABSTRACT FROM AUTHOR]

Tetramethylammonium hydroxide (TMAH) is widely used as a solvent in the semiconductor industry. After the photo-impression process, it is necessary to remove the photoresist (PR) layer from the surface of the circuits; for this purpose, a TMAH solution is usually used. This chemical compound is highly toxic and corrosive and cannot be discharged into the environment. This study was carried out in collaboration with LFoundry (SMIC group), in order to prove the feasibility of biodegradation under aerobic conditions, using microorganisms coming from the LFoundry's wastewater treatment plant (WWTP) at different operating conditions. The feed composition was modified in order to add a small but increasing amount of TMAH and PR. The aim was to verify if the increase of TMAH concentration was harmful to bacteria. The feed stream, containing TMAH and PR, was the only carbon source for the metabolism of the aerobic microorganisms. The results of this study demonstrated an effective biological degradation of TMAH and showed a total removal efficiency of more than 99.3%, with a final concentration of 7 mg/L. Moreover, the kinetic parameters of the Monod model were also calculated. The results obtained from the experimental campaign were used to design a pilot plant that will treat around 25 L/h of waste TMAH/PR solution. [ABSTRACT FROM AUTHOR]

The article reports the preliminary results obtained in a pilot plant that treats a spent tetramethylammonium hydroxide (TMAH) solution, a typical chemical compound used in the microelectronics industry and massively present in wastewaters. The plant is based on three aerobic bioreactors in series, fed by a real TMAH solution effluent from the semiconductor industry. The plant ran for 14 days in continuous operating mode with a flow rate of 5 L/h; then, the plant switched to batch mode. The microbial population was analyzed to determine if microbial population changes occurred. The results indicated that TMAH degradation only occurred during the batch operation mode. The TMAH reduction was about 80% in the first reactor and complete (100%) in the second and third bioreactors. At the same time, the microorganisms increased their mass by 338%, 58%, and 1% in the first, second, and third bioreactor, respectively. The degradation intermediates confirmed the efficiency of the process and the possible reuse of water, which closes the water loop's circularity. Furthermore, a nitrate concentration of 150–250 mg/L was found in the last two bioreactors: this implies a significant presence of ammonium-oxidizing bacteria. Community genomic analysis was conducted to detect changes in the microbial community due to changes in operating conditions that could cause reactor failure if methylotrophs were washed out or outcompeted by unspecific bacteria. [ABSTRACT FROM AUTHOR]