Energy is a crucial factor for urban development. Cities have a crucial role in climate change, as they use 2/3 of the world’s energy, producing 70% of greenhouse gas (GHG) emissions. In order to reduce the large ecological footprint of the utilization of conversional energy sources (coal, gas, and oil) and enhance a nation’s energy independence (security), it is crucial to find alternative fuels. Biomass residues are characterized as a sustainable and carbon-neutral energy source. Hence, this review describes a critical assessment of not only the quality characteristics of several waste and biomass residues for bioenergy production and biofuels but also the value-added products that could be produced from wastes to enhance industry (e.g., pharmaceutical, cosmetics, packaging industry, etc.). Furthermore, the challenges and potential solutions of waste utilization for bioenergy production and the transformation of value-added products for urban sustainability are also explored. Despite the high-quality characteristics and the availability of these wastes, several critical factors should be taken into account. Biomass residues could contribute to sustainable development goals (SDG), such as sustainable cities and communities, clean energy, responsible consumption and production, the economic growth of a country, and, as a result, urban development.

A global scientific interest is observed for alternative utilization of biomass wastes in the context of circular economy. Transforming waste into biofuels is a sustainable solution for dealing with global environmental issues. This article reviews recent trends and the development of biomass waste combustion technologies for energy recovery. Not only the latest scientific progress on combustion processes but also several innovative advanced technologies, such as carbon capture and storage (BECCS) technologies, oxy-fuel combustion, and chemical looping combustion (CLC) are analyzed. More specifically, combustion technologies such as fixed bed combustion, bubbling fluidized bed combustion (BFBC), circulating fluidized bed combustion (CFBC), pulverized fuel combustion (PC), oxy-biomass combustion in pulverization systems (Oxy-PC), oxy-biomass combustion in Bubbling fluidized bed combustors (Oxy-BFB), oxy-biomass combustion in circulating fluidized bed systems (Oxy-CFB), and biomass chemical looping combustion (CLC) are analyzed. Advantages and limitations of each advanced combustion method are also discussed. In addition, recent applications of artificial intelligence (AI) and machine learning (ML) for optimizing bioenergy processes and mitigating greenhouse gas (GHGs) emissions are presented. The combination of these advanced combustion technologies (CCS/CLC) with intelligence tools (AI/ML) can lead to enhanced combustion efficiency, reduced secondary wastes, better waste management, and reduced emissions. This comprehensive analysis could assist scientists and decision-makers in choosing the appropriate sustainable advanced waste-to-energy (WtE) technology. More studies should be performed in advanced AI-based smart bioenergy production to optimize the best solution in alternative feedstocks, operating parameters, green nanomaterials, and zero emissions for enhanced plant performance and reduced environmental issues.

Recently, coal power plants across Europe have been reopened. Alternative fuels are needed for energy autonomy purposes, for a smoother transition to the post-lignite era and for sustainable development. In this work, different categories of municipal solid wastes (MSW) and their blends with lignite were studied for their potential use as alternative fuels. Seventeen samples were studied using several techniques: gross calorific value (GCV), proximate analysis, ultimate analysis, ion chromatography, ash elemental analysis, thermogravimetric analysis, kinetic modeling and thermodynamic analysis. A determination of empirical chemical formulas was performed. Slagging/fouling potential was evaluated with various indices including modified indices that take into account ash production and GCV. Maximum emission factors were calculated and defined per produced MJ. Also, an environmental footprint index was developed regarding the environmental impact of solid wastes. The GCV experimental results were compared with those of twenty different empirical models. Moreover, several case studies were performed to evaluate the potential of covering the energy demands, with combustion of MSW, in Greece and Europe. The results showed that MSW as a primary/secondary fuel is an attractive solution considering the fact that it boasts better characteristics in comparison with lignite. Moreover, the environmental footprint index (EFI_sw) of the MSW revealed a much smaller environmental impact. The high N content is not always translated to high emissions if NO is expressed per produced MJ (gNO/MJ). In addition, MSW can also be used as a significant contributor in covering energy demands regarding the energy recovery potential. Graphical

The combustion characteristics of blends of lignite with various organic waste materials are evaluated in this study in order to assess their potential for energy recovery. Different types of municipal solid waste (i. e. paper, plastic, textile, organic), as well as sewage sludge and agri-residues (sunflower shells) samples were collected from the Western Macedonia region, northern Greece. Mixtures of each one of them with lignite in different proportions (30-50-70 wt.%) were prepared. Proximate analysis, calorific value determination, and thermogravimetry (TGA/ DTG) were performed. Thermal parameters such as ignition temperature, total weight loss, maximum rate of weight loss, peak and burnout temperatures and burnout time were determined from the TG/DTG profiles of the raw materials and their blends. The combined utilization of proximate analysis, calorific value determination and TG/DTG method proved to be an effective method for a preliminary assessment of the energetic potential of raw solid waste ?combustible? materials and their blends with lignite. The analytical results revealed that most of the blends are promising for energy recovery. Regarding the raw wastes, sunflower shells were the most reactive. A non-synergistic effect was found for the blends. Organic and sewage sludge blends revealed the lowest combustibility, which is attributed to the high content of inorganic matter and the heterogeneity of these two types of wastes.