The treatment of municipal wastewater is considered a cornerstone for the protection of public health and environment. However, a major issue derived from this process is the large quantities of produced sewage sludge. Although anaerobic digestion is a widely applied method in Wastewater Treatment Plants (WWTPs) aiming to stabilize the sludge and to recover energy in the form of methane, it is usually limited due to the reduced decomposition efficiency and slow biodegradation rate of this recalcitrant substrate. For this reason, various pretreatment methods have been proposed aiming to modify the sludge structure, solubilize the organic matter, and decrease the crystallinity of sludge so as to accelerate hydrolysis and consequently enhance methane production. The current research is a comprehensive collection of recent advances in pretreatment technologies that can be potentially applied in wastewater treatment facilities. The critical review analysis presented herein reveals the several advantages and drawbacks, as well as the technical opportunities of the pretreatment methods and provides an assessment of their feasibility/applicability from an energetic, environmental, and economic point of view.

The management of solid waste is currently seen as one of the most important concerns that national authorities, particularly in south Europe, must address. In recent years, emphasis has begun to be paid to Construction and Demolition Waste (CDW) being the largest waste stream in the European Union that is produced by renovation and repair work on buildings, roads, bridges, and other constructions made of bulky materials such as asphalt, bricks, wood, and plastic. Many EU countries responded quickly as a result of the large amounts of such waste and the presence of hazardous substances in their composition. This study illustrates the anticipated outcomes of several CDW management strategies other than final disposal, such as recycling, reuse, and incineration, for a public-school building in Greece. In order to assess how well the chosen schemes performed in terms of various environmental criteria, the SimaPro software suite and the Ecoinvent v.3 Life Cycle Inventory database were used. In order to enhance the quality of the outcomes, inventory data from earlier studies were also employed as input data for the Life Cycle Assessment tool.

Municipal Solid Waste (MSW) management has been a major problem of modern cities for many years. Thus, the development of optimal waste management strategies has been a priority for the European Commission, especially in the transition toward a circular economy. In this paper, an analysis of different MSW treatment methods that can be effectively implemented in the Region of Central Macedonia (RCM) is provided, and their comparison from an environmental point of view is performed. The assessment is based on real data indicated in the recently updated Greek National Waste Management Plan, whereas the different scenarios developed include landfilling without energy recovery, landfilling with energy recovery, recycling and secondary materials recovery, mechanical-biological treatment, bio-waste composting and anaerobic digestion with energy recovery, and incineration with energy recovery. The obtained results illustrate that efficient waste streams sorting is of vital importance for the effective implementation of an integrated waste management system toward the sustainable management of MSW.

The amount of spent coffee grounds (SCGs) created, represents an environmental challenge worldwide. In this context, the aim of the present study was to exploit the potential of SCGs as a source of bioactive compounds that can be utilized in high value-added products. Thus, a cost-effective and environmentally friendly extraction technique was developed to ensure extracts with high total phenolic content and antioxidant activity, as well as significant amounts of caffeine and chlorogenic acid. Response surface methodology was implemented to evaluate the effects of the main extraction parameters (i.e., time, temperature, and ethanol-to-water ratio) and their interactions on the defined responses. The ethanol ratio was found to be the most significant variable. Then, a set of optimum values was determined (i.e., 7 min, 75 °C, and ethanol:water ratio 5:95), where the predicted values for responses were found to be 5.65% for the yield (Y₁), 152.68 mg gallic acid equivalents per L for total phenolic content (Y₂), 0.797 μmol Trolox equivalent per mL for the antioxidant activity (Y₃), 30.5 ppm for caffeine concentration (Y₄), and 17.4 ppm for chlorogenic acid concentration (Y₅). Furthermore, the corresponding high experimental values from the validation experiment fitted well to these predictions, clearly clarifying the high potential of SCG extracts for use in high value-added applications.

Modern pig production must balance efficiency, animal welfare, and environmental sustainability while embracing circular bioeconomy principles. This review critically examines the scientific literature from the past decade, focusing on the environmental impacts of pig farming, animal welfare considerations, and circular bioeconomy strategies. Key challenges include the ethical treatment of pigs, regulatory frameworks, and the sector’s contribution to climate change through emissions and resource use. Sustainable pig farming relies on innovative housing systems, welfare-oriented management practices, and legislative measures that improve animal welfare. Moreover, integrating circular bioeconomy strategies, which include manure management for biogas production, alternative feed ingredients, and wastewater recycling, enhances resource efficiency while reducing environmental footprints. Life Cycle Assessment (LCA) methodologies provide insight into the environmental impacts of different production systems, guiding policymakers and producers toward more sustainable practices. Despite these advances, further research is needed to optimize feed alternatives, improve manure treatment technologies, and explain how to improve animal welfare standards. This review highlights the importance of interdisciplinary approaches in achieving sustainable pig farming and underscores the need for continued innovation in aligning productivity and environmental aims.

Food systems and, to an extent, the pig sector are major contributors of greenhouse gas (GHG) emissions globally. At the same time, significant amounts of waste are produced from the food sector. The aim of this study is to examine the implementation of circular bio-economy practices in the Greek pig sector to improve its environmental performance. More specifically, in collaboration with a pig farm in Northern Greece and a waste management company, the collection and processing of bakery by-products was organized to produce bakery meal (BM) to integrate it in the diets of fattening and growing pigs. Using Life Cycle Assessment (LCA) methodology, the environmental performance of 20% BM inclusion in pig diets was examined in comparison with the conventional feedstock. BM experimentally replaced corn, wheat, barley, and soya bean from conventional feedstock. The Life Cycle Inventory (LCI) was based on the yearly average values of feed and energy consumption to produce 1 kg of living weight of pig on the pig farm. Life Cycle Impact Assessment (LCIA) was conducted with SimaPro v3.5, using Recipe Midpoint Hierarchical v1.6. The LCIA calculations exhibited that BM inclusion in pig diets can lead to significant land occupation decrease, approximately 30%, which is mostly related to reduced wheat and soya beans. The reduction of cultivated croplands also led to reduced fertilizer and pesticide application, which improved marine eutrophication and freshwater ecotoxicity impact by 20% while it significantly reduced risks of human carcinogenic toxicity by 25%. Moreover, the Greek pig sector exhibited a 5% capacity for overall improvement of its environmental performance, which relies on minimizing logistics when the pig farm conducted collection and processing of by-products. A basic assumption of this study is the assessment of bakery by-product quantities in the wider region of the pig farm. The availability of by-products, based on the reported experience, was limited, and the reliability of the supply was frequently disrupted. As such, the supply chain model of the central hub for the collection and processing of bakery by-products is proposed as more efficient for regulating logistic challenges and availability.