###### Abstract
Afterward, a series of treatments are usually applied to the resulting materials like torrefaction, a mild pyrolysis process where the biomass is heated in an inert atmosphere, typically between 200 \({}^{\circ}\)C and 300 \({}^{\circ}\)C. This results in the dehydration and decarboxylation of the biomass, making it more brittle and enhancing its grindability. The main advantages of torrefaction include increased energy density, improved storage properties, and reduced biological activity. However, it has the disadvantages of requiring additional energy input for the process and potential emissions of volatile organic compounds [31, 32, 33]. Steam Explosion involves subjecting the biomass to pressurized hot steam for a period of time and then rapidly depressurizing it. This treatment disrupts the structure of the biomass, making it more accessible for further processing. The advantages of steam explosion include enhanced pellet durability and mechanical strength, as well as increased surface area for subsequent chemical reactions. The disadvantages include the complexity of the equipment and the potential loss of some volatile components [31, 32, 33]. Hydrothermal carbonization is a process where biomass is treated with water at elevated temperatures and pressures, leading to the formation of a carbon-rich material. This method is particularly suitable for materials with high moisture content, such as wet agricultural residues. The advantages include the production of a stable, high-energy-density product, and the ability to handle wet feedstock directly. However, the disadvantages include the need for high-pressure equipment and the generation of a wastewater stream that requires treatment. Biological treatment involves exposing the biomass to microorganisms that break down the recalcitrant components of the biomass. This method can be advantageous due to its low energy requirements and the potential for bioconversion into valuable products. However, it is often a slower process and can be less predictable due to variations in microbial activity and environmental conditions [31, 32, 33]. These advanced treatments significantly improve the efficiency and utility of biomass as a renewable energy source. By refining the raw materials through these processes, we can create biomass fuels that are more energy-dense, easier to transport and store, and capable of producing lower emissions when used. This holistic approach to biomass utilization helps address the limitations of raw biomass and maximizes its potential as a sustainable alternative to fossil fuels. The biomass is then finally turned into pellets ranging from 6 mm up to 40 mm in size, as per literature [32], permitting its use for energy generation [28]. In the context of wine by-products, understanding the production of these biomass pellets is important, specifically the few nuances related to the utilization of mixed biomass pellets. These are pellets produced through the usage of biomass materials other than wood, normally by reusing biomass from agricultural wastes. If worked upon properly, these pellets can possibly achieve energy release and heating values similar to standard wood pellets [34,35]. However, mixed biomass pellets tend to contain problematic amounts of sulfur and chlorine, which is concerning due to the effects these chemicals have on both the equipment upon which they are used and the environment [35]. In the case that the values exceed the commercially recommended standard set by independent pellet certification schemes it is suggested that the biomass should be mixed in with other materials in order to improve its content properties [35]. The need to sometimes combine different materials in order to produce adequate pellets does present itself as an opportunity to reutilize biomasses such as wood shavings, sawdust and other wastes that may have been produced in a variety of industries [28; 35].