The coconut tree (Cocos nucifera) stands as a pivotal resource in tropical regions, playing a crucial role in both subsistence and economic activities across Asia, the Pacific Islands, and South America. While the harvesting of coconut fruit is essential for producing globally utilized edible products, such as coconut oil, by small owners and large producers around the world in the food, cosmetics, and pharmaceutical industries, concerns have arisen due to the substantial amount of agro-industrial residue generated in this process, posing environmental risks if they are not properly managed. Recognizing the environmental challenges, this paper emphasizes the transformative potential inherent in coconut waste, characterized by its lignocellulosic composition rich in lignin and multifunctional groups. By delving into the historical context of coconut economic exploration and its chemical composition, this review explores the diverse applications of coconut products, focusing on the utilization and processing of residues to generate sustainable products and byproducts. Ultimately, this comprehensive review underscores the significance of repurposing coconut waste, not only to mitigate the environmental impact but also as a valuable contributor to a circular economy, promoting the use of the lignocellulosic biomass in research and bolstering its role as a raw material in the chemical and energy sectors.

Europe is considered the largest producer of wine worldwide, showing a high market potential. Several wastes are generated at the different stages of the wine production process, namely, vine pruning, stalks, and grape marc. Typically, these residues are not used and are commonly discarded. Portugal generates annually approximately 178 thousand metric tons of wine production waste. In this context, the interest in redirecting the use of these residues has increased due to overproduction, great availability, and low costs. The utilization of these lignocellulosic biomasses derived from the wine industry would economically benefit the producers, while mitigating impacts on the environment. These by-products can be submitted to pre-treatments (physical, chemical, and biological) for the separation of different compounds with high industrial interest, reducing the waste of agro-industrial activities and increasing industrial profitability. Particularly, vine-pruning residue, besides being a source of sugar, has high nutritional value and may serve as a source of phenolic compounds. These compounds can be obtained by bioconversion, following a concept of biorefinery. In this framework, the current routes of the valorisation of the pruning residues will be addressed and put into a circular economy context.

Gasification of lignocellulosic biomass has been widely highlighted as one of the most robust and promising low-carb approaches toward sustainable energy production. The gasification syngas obtained from agro-industrial residues can produce heat, power, biohydrogen, and other drop-in biofuels via F-T (Fischer-Tropsch) synthesis. However, the tar formation during the thermochemical process imposes severe limitations on the commercial scale of this technology. Tar elimination is a critical step for avoiding damage to equipment and not restricting the further application of syngas. In this context, this work sheds light on the biomass gasification field and reviews some aspects of tar formation and technologies for its reduction and removal. The approaches for dealing with tar are primary methods, which suppress or remove tar within the gasifier, and secondary methods, which remove tar in post-operation treatment. Catalytic reforming offers the most cost-effective pathway to removing tar. The bimetallic combination of nickel with other metals and using biochar as support have been intensely investigated, showing excellent tar conversion capacity. Recent research has provided new trends in non-thermal plasma-catalyzed biomass tar reforming. Future studies should focus on the integration of catalysts with multiple techniques to improve efficiency and reduce energy consumption.