Research in Advanced Biofuels steadily developed during recent years. A number of highly innovative technologies have been explored at various scale: among these, lignocellulosic ethanol and CTO (Crude Tall Oil)-biofuel technologies already achieved the early-commercial status, while hydrotreating of vegetable oils (HVO, or HEFA) can be considered today fully commercial. However, despite the level of innovation in each specific technological process under consideration, the feedstock maintains a central role in making a biofuel chain really sustainable. In this context, microalgae grown in salt-water and arid areas offers a considerable opportunity for advanced biofuel production: at the same time, however, they also represent a considerable challenge. Processing microalgae in an economic way into a viable and sustainable liquid biofuel (a low-cost mass-produced product) is not trivial. So far, the main attention has been given to cultivating the microorganism, accumulating lipids, extracting the oil, valorising co-products, and treating the algae oil into biodiesel (through esterification) or HEFA (Hydrotreated Esthers and Fatty Acids), this second one representing a very high quality biofuels, almost a drop-in fuel (suitable either for road transport or for aviation), which production exceed 2 Mt y-1 today.However, extracting the algae oil at low cost and at industrial scale is not yet a full industrial mature process, and the still limited market size of algae-to-biofuels makes difficult the development of industrial-scale systems. Nevertheless, another option can be considered, i.e. processing the whole algae into dedicated thermochemical reactors, thus approaching the downstream processing of algae in a completely different way from separation.The present work examines the possible routes for thermochemical conversion of microalgae, distinguishing between dry-processes (namely pyrolysis and gasification) and wet-processes (near critical water hydrothermal liquefaction and hydrothermal gasification). Typical expected elementary composition of major products is given. Main peculiarities of batch versus continuous processing are also discussed from an engineering point of view.Major engineering advantages and challenges in thermochemically conversion of algae are identified and discussed, in view of the production of a transport biofuel. Finally, future perspectives for each route are given in terms of current and expected technological readiness level

Biochar, produced through pyrolysis of lignocellulosic biomass, is attracting increasing interest as soil amendment thanks to its potential numerous benefits to agriculture, as well as its ability to sequester carbon in soil. Solid fraction of digestate from anaerobic digestion is a well-known N-rich substrate, most often composted in large and small agro-industrial plants. Co-composting biochar and digestate has the potential to synergistically increase the agronomic value of both components: however, it needs further process and on-field research. The present research work reports on the experimental tests on producing biochar and co-composting various biochar amounts with digestate from biomass anaerobic digestion (product here named COMBI). Biochar was produced by feeding wood chips from chestnut to an innovative oxidative reactor. In order to evaluate the quality of the products obtained by composting and co-composting, correlating this with the final biochar rate in the material, the net organic matter yield, the humified organic matter, the compliance with the European Compost Network Quality Assurance Scheme (ECN-QAS) limits for inorganic pollutants, and the product stabilization and sanitization indexes were investigated. The 11.2% w/w d.b. biochar rate in the initial blend (19.8% w/w d.b final concentration in the co-composted products) offered the best performances and is recommended for further investigation. Additional benefits from co-composting were also assessed, as the reduced dust load that favors safety and health during logistics and use.

In recent years, the application of biochar as soil amendment has generated a huge interest for the preservation of soil fertility by improving the physicochemical and biological properties of soil, and for the reduction of the negative effects of greenhouse emissions (climate-change adaptation). In this study, we investigated the effect of three soil amendments, namely, biochars derived from wood (BC), solid digestate (SD), and biochar derived from solid digestate (BSD), on soil parameters and their influence in maize-growth performance. The experiment was conducted in a greenhouse where organic amendments were applied to the soil control (C) at different application rates: 0%, 1%, 2%, and 3% w/w (equivalent at 0, 10, 20, and 30 t ha⁻¹, respectively). The results indicated that all applications of organic amendments significantly enhanced soil parameters such as pH and electrical conductivity, while only BSD and SD showed a significant increase in secondary macro-(i.e., Ca, Mg) and micronutrient-element content (i.e., Na, Fe, Mn and Zn). The best maize performance (i.e., plant height, stem diameter, biomass dry weight, seed number, and weight per ear) was observed while using BSD, while plant growth in BC had reduced results, probably due to the low presence of elemental content and the relatively high volatile-matter (VM) content, which may have altered nitrogen dynamics.