The chemical composition of woody biomass directly influences its thermal degradation and, subsequently, the selection of processes and technologies used for its conversion into energy or value-added products. Thus, the present study aimed to evaluate the thermal behavior and chemical-physical characteristics of three different woody biomass species (hardwood, softwood and chemically-treated wood) using thermogravimetric and characterization analysis based on ISO 16948, ISO 18125 and ISO 18122 methods. The main findings show that the most significant trend of mass loss, around 70%, in the thermal degradation of the different species of woody biomass occurred between 150 °C and 500 °C and that the residual mass at 650 °C was between 13% and 24%. Although the three species of woody biomass showed a high average energy content (19.60 MJ/kg), softwood samples had a more stable thermal degradation than hardwoods and chemically-treated woods.

Electricity is predicted to be the energy vector that will undergo major changes in the future, and a transition would be observed in the resources such as waste and residual biomass that we use to satisfy the energy demand. Therefore, this study aims to highlight the main economic and environmental performances of different biowaste-to-energy technologies for small-scale electricity generation by comparing the direct combustion of refined vegetable oil obtained from waste cooking oils (thermal pathway), anaerobic digestion of biowaste (bio-chemical pathway), and gasification of wood residues (thermo-chemical pathway). The economic analysis is mainly based on personal experiences in the energy sector and shows an overview of the performance in investment of combined heat and power (CHP) systems, ranging from 100 to 500 kW for a period of 20 years. The environmental assessment is conducted considering the life-cycle thinking approach using support from the openLCA software, product environmental footprint (PEF) data-base, and previous studies that have reported environmental inventory data from real industrial cases.

At present, the majority of available road and jet biofuels are produced from oleochemical feedstocks that include vegetable oils and biowastes such as waste cooking oils and animal fats. Additionally, one of the most promising ways to achieve long-term environmental goals is to sustainably use lignocellulosic residues. These resources must be treated through a deoxygenation process and subsequent upgrading processes to obtain high-quality road and jet biofuels. Accordingly, in this review, we explore recent advancements in the deoxygenation of oleochemical and lignocellulosic feedstocks in the absence of hydrogen to produce high-quality road and jet biofuels, mainly focusing on the use of nanomaterials as catalysts and the valorization of lipid-rich biowastes and lignocellulosic residues. As a result, we found that regardless of the catalyst particle size, the coexistence of basic sites and weak/medium acid sites is highly important in catalytic systems. Basic sites can enhance the removal of oxygenates via decarboxylation and decarbonylation reactions and inhibit coke formation, while weak/medium acid sites can enhance the cracking reaction. Additionally, the extraction of value-added derivatives from lignocellulosic residues and their subsequent upgrade require the use of advanced methods such as the lignin-first approach and condensation reactions.