The present study investigates a two-stage process aimed at producing biogas from food waste leachates (FWL) through an experimental approach. The first stage involves biohydrogen production via dark fermentation (DF), while the second focuses on biomethane production through anaerobic digestion (AD). The substrate consists of leachates derived from fruit and vegetable waste, which are introduced into two continuous stirred-tank reactors (CSTR1) with two different inoculum-to-substrate ratios (ISR). Dark fermentation occurs in these reactors. The effluent from the CSTRs is then fed into two additional reactors for methanogenesis. All reactors operated under mesophilic conditions. During the DF stage, hydrogen yields were relatively low, with a maximum of 8.2 NmL H₂/g VS added (ISR = 0.3) and 6.1 NmL H₂/g VS added (ISR = 0.5). These results were attributed to limited biodegradation of volatile solids (VS), which reached only 21.9% and 23.6% in each respective assay. Similarly, the removal of organic matter was modest. In contrast, the AD stage demonstrated more robust methane production, achieving yields of 275.2 NmL CH₄/g VS added (ISR = 0.3) and 277.5 NmL CH₄/g VS added (ISR = 0.5). The system exhibited significant organic matter degradation, with VS biodegradability reaching 66%, and COD removal efficiencies of 50.8% (ISR = 0.3) and 60.1% (ISR = 0.5). The primary focus of the study was to monitor and quantify the production of the two biofuels, biohydrogen and biomethane. In conclusion, this study provides an assessment of the two biochemical conversion pathways, detailing the generation of two valuable and utilizable gaseous products. This research examines the process-specific operational conditions governing gas production, with a focus on optimizing process parameters to enhance yield and overall efficiency.

The European Union has started a progressive decarbonization pathway with the aim to become carbon neutral by 2050. Energy-intensive industries (EEIs) are expected to play an important role in this transition as they represent 24% of the final energy consumption. To stay competitive as EEI, a clear and consistent long-term strategy is required. In the magnesia sector, an essential portion of CO₂ emissions result from solid fossil fuels (MgCO₃, pet coke) during the production process. This study concerns the partial substitution of fossil fuels with biomass to reduce carbon emissions. An experimental campaign is conducted by implementing a new low-NO_x burner at the magnesia plant of Grecian Magnesite (GM). Life cycle assessment (LCA) is performed to quantify the carbon reduction potential of various biomass mixtures. The experimental analysis revealed that even with a 100% pet coke feed of the new NO_x burner, NO_x emissions are decreased by 41%, while the emissions of CO and SO_x increase slightly. By applying a biomass/pet coke mixture as fuel input, where 50% of the required energy input results from biomass, a further 21% of NO_x emission reduction is achieved. In this case, SO_x and CO emissions are additionally reduced by 50% and 13%, respectively. LCA results confirmed the sustainable impact of applying biomass. Carbon emissions could be significantly decreased by 32.5% for CCM products to 1.51 ton of CO₂eq and by 38.2% for DBM products to 1.64 ton of CO₂eq per ton of MgO in a best case scenario. Since the calcination of MgCO₃ releases an essential and unavoidable amount of CO₂ naturally bound in the mineral, biomass usage as a fuel is a promising way to become sustainable and resilient against future increased CO₂ prices.

A rapidly emerging approach within the scientific community involves the utilization of waste streams for renewable energy generation, particularly through biomethane production. A key aspect of this approach lies in the co-digestion of diverse waste streams, which can enhance process efficiency and contribute to a more effective reduction in the organic load. The present study investigates the anaerobic digestion of a mixture of food waste leachates and dairy waste (cheese whey wastewater), with a dual objective: to evaluate the reduction in organic-load efficiency of the mixed substrate and to assess the production of biogas enriched in biomethane content. Three distinct mixing ratios by volume of the two waste streams (25%/75%, 50%/50% and 75%/25%) were subjected to an anaerobic digestion process under the same SIR. The performance of each mixture was assessed in terms of both reduction in organic-load efficiency and biomethane yield, followed by a comparative analysis to identify the optimal mixing ratio. The results indicate that while the organic-load reduction remains consistently effective across all mixing ratios, the biomethane production potential is notably higher for the 25%/75% waste mixture, highlighting it as the most promising configuration for both energy recovery and waste treatment efficiency.

In this paper, two flexible model tools (CO₂ emissions/cost tool and CFD tool) that simulate the production process of Grecian Magnesite (GM) and extract economic and technical conclusions regarding the substitution of fossil fuels with various types of biomass are presented and analyzed. According to the analysis, the higher the substitution, the higher the profit in both CO₂ emissions and cost reduction. The reduction in CO₂ emissions that can be achieved through biomass fuel substitution ranges from 15% for a 30% substitution to 35% for a 70% substitution. Accordingly, production costs are also reduced with the use of biomass. The initial results of this decision-making cost tool showed that the most profitable solution is a 70% substitution, for which production costs can be reduced by up to 38.7%, while the most beneficial type of biomass proved to be the olive kernel. A proposed and feasible solution is the substitution of 50% sunflower husk pellets, which will result in a reduction of 25% in CO₂ emissions and almost 10% in production cost. From CFD simulation, a reduced order model (ROM) has been developed that allows the running of scenarios in real time, instead of the usual long times required by complex simulations. Comparative studies of fuel blend and biomass type can be carried out easily and rapidly, allowing one to choose the most suitable substitution.

The greatest challenge of our era is achieving climate neutrality while strengthening adaptation and resilience to climate change. Addressing this requires an integrated approach that combines scientific, technological, and economic solutions with community engagement and public awareness. In this context, the European Commission’s New European Bauhaus (NEB) initiative serves as a bridge linking science and technology with art, culture, social inclusion, and civic participation. This paper investigates the regeneration of an urban area in Kozani, Greece, carried out in alignment with the principles of NEB. The project comprises the energy and esthetic renovation of three public buildings—two schools and a cultural center—together with the comprehensive revitalization of an adjacent park. The impact of these interventions is assessed through a set of Key Performance Indicators (KPIs) defined within the NEB framework. These KPIs encompass technical, social, and economic dimensions, with a particular emphasis on the initiative’s three core values: Beautiful, Sustainable, and Together. The implementation represents one of the earliest practical applications of the NEB framework in Europe. Beyond the tangible outcomes, its significance lies in the systematic evaluation of both the interventions and the methodological tools employed, highlighting how the implementation process diverges from conventional urban regeneration approaches, how it operationalizes NEB principles, and how these principles contribute to results that are more effective. Finally, this comprehensive assessment provides a transferable model for monitoring, learning, and scaling similar initiatives in other urban contexts.

One of the most challenging yet promising technologies combining waste management with waste utilization for the production of a renewable fuel (biogas) is anaerobic co-digestion. This study investigated the anaerobic co-digestion of three organic waste streams: cheese whey wastewater (CWWW), pig slurry (PS), and food waste leachate (FWL). FWL and CWWW were combined to form a base mixture of constant composition (BM), which was subsequently blended with diluted PS at three BM/PS mass ratios: 25/75, 50/50, and 75/25 (% v/v). The mixtures were evaluated under mesophilic conditions through laboratory-scale batch experiments to assess the influence of substrate composition on biomethane production and organic matter removal. Physicochemical characterization of the individual substrates and mixtures included pH, volatile fatty acids, alkalinity, chemical oxygen demand (COD), and volatile solids (VS). Biochemical methane potential (BMP) assays were conducted, with daily and cumulative methane production systematically monitored throughout the experimental period. Methane production kinetics were evaluated by fitting the modified Gompertz model to the experimental data, enabling estimation of maximum methane production potential, maximum production rate, and lag-phase duration. Experimental results demonstrated that the 75/25 BM/PS mixture achieved the highest specific biomethane yield (525.9 CH₄ Nml/g VS_added) and maximum production rate (μ_m = 36.3 CH₄ Nml/g VS_added/d), alongside the highest removal efficiencies for COD (83.0%), TOC (87.9%), and VS (63.7%), compared with the 50/50 (309.9 CH₄ Nml/g VS_added) and 25/75 (156.5 CH₄ Nml/g VS_added) mixtures. The integrated assessment of methane yield, kinetic parameters, and organic matter removal enables comparative evaluation of the three mixtures and identifies the 75/25 BM/PS formulation as the most favorable mixing ratio for efficient co-digestion of these waste streams.