Circular economy and sustainability are pivotal concepts in the discourse on the synergies between economic growth and environmental impact. As resource scarcity and environmental degradation intensify, advancements in energy conversion technologies become crucial for a sustainable economic model. Currently dependent on fossil fuels, the global economy must shift to a sustainable framework focused on bioenergy. Biomass, a renewable energy source, offers a promising solution by converting waste into valuable resources, reducing waste and environmental impact, and creating economic opportunities. Biofuels and bioproducts can meet energy needs while reducing greenhouse gas emissions and addressing global warming. Recent advances in biofuels, supported by initiatives and policies, promote more sustainable energy production. This paper aims to highlight the potential of biomass in meeting contemporary energy demand and provides an overview of biofuels and their production as a renewable alternative to fossil fuels. It also explores the future of agriculture and energy sectors, emphasizing global energy and environmental challenges and the competition between food and fuel feedstocks.

Can mitigating only particle mass, as the existing air quality measures do, ultimately lead to reduction in ultrafine particles (UFP)? The aim of this study was to provide a broader urban perspective on the relationship between UFP, measured in terms of particle number concentration (PNC) and PM2.5 (mass concentration of particles with aerodynamic diameter < 2.5 μm) and factors that influence their concentrations. Hourly average PNC and PM2.5 were acquired from 10 cities located in North America, Europe, Asia, and Australia over a 12-month period. A pairwise comparison of the mean difference and the Kolmogorov-Smirnov test with the application of bootstrapping were performed for each city. Diurnal and seasonal trends were obtained using a generalized additive model (GAM). The particle number to mass concentration ratios and the Pearson's correlation coefficient were calculated to elucidate the nature of the relationship between these two metrics. Results show that the annual mean concentrations ranged from 8.0 × 103 to 19.5 × 103 particles·cm-3 and from 7.0 to 65.8 μg·m-3 for PNC and PM2.5, respectively, with the data distributions generally skewed to the right, and with a wider spread for PNC. PNC showed a more distinct diurnal trend compared with PM2.5, attributed to the high contributions of UFP from vehicular emissions to PNC. The variation in both PNC and PM2.5 due to seasonality is linked to the cities' geographical location and features. Clustering the cities based on annual median concentrations of both PNC and PM2.5 demonstrated that a high PNC level does not lead to a high PM2.5, and vice versa. The particle number-to-mass ratio (in units of 109 particles·μg-1) ranged from 0.14 to 2.2, >1 for roadside sites and <1 for urban background sites with lower values for more polluted cities. The Pearson's r ranged from 0.09 to 0.64 for the log-transformed data, indicating generally poor linear correlation between PNC and PM2.5. Therefore, PNC and PM2.5 measurements are not representative of each other; and regulating PM2.5 does little to reduce PNC. This highlights the need to establish regulatory approaches and control measures to address the impacts of elevated UFP concentrations, especially in urban areas, considering their potential health risks.

An economy based on renewable energy sources is the hallmark of responsible companies. Climate policy and energy crisis commitments have led to a search for alternative ways to produce energy. Bioenergy is considered the most consistent renewable energy source due to its economic and environmental benefits. Biogas and biomethane are promising forms of renewable energy derived from widely available evergreen raw materials. Agricultural, animal, industrial and food wastes are excellent substrates used to produce clean and sustainable energy in a circular economy context. Their conversion into biogas and biomethane through the anaerobic digestion (AD) process is an efficient solution to the treatment of waste of different origins. The production and use of biomethane favor important environmental advantages, such as the reduction in greenhouse gas emissions compared with those deriving from the use of conventional fossil fuels. This review would like to highlight modern trends and approaches to evaluate processes and strategies to control biogas and biomethane production. In particular, the use of livestock waste for the digestion process and the reuse of the by-product as fertilizer, as well as the potential development of biogas and biomethane as prospects for the improvement and optimization of renewable energy sources, are discussed.

The World Health Organization (WHO) has always stressed the importance of indoor air quality (IAQ) and the potential danger of pollutants emitted from indoor sources; thus, it has become one of the main determinants for health. In recent years, reference documents and guidelines have been produced on many pollutants in order to: i) decrease their impact on human health (as well as the number of pollutants present in indoor environments), and ii) regulate the relevant levels of chemicals that can be emitted from the various materials. The aim of this paper is to discuss and compare the different legislations present in the European Union (EU). Furthermore, a focus of this paper will be dedicated at Italian legislation, where there is currently no specific reference to IAQ. Although initiatives in the pre-regulatory sector have multiplied, a comprehensive and integrated policy on the issue is lacking. Pending framework law for indoor air quality, which takes into account WHO indications, the National Study Group (GdS) on Indoor Air Pollution by the Italian Institute of Health (IIS) is committed to providing shared technical-scientific documents in order to allow actions harmonized at a national level. An outlook of the main Italian papers published during these last five years will be reported and discussed.