###### Abstract  
The by-products of the wine industry represent a global production of 10.5 to 13.1 million tons of wine pomace annually. This study examines the chemical composition and energy potential of wine pomace and distillation stillage, evaluating their suitability for pellet production within ENplus(r) standards. Proximate analysis, elemental analysis, and calorimetric analysis were conducted on samples of the two by-products collected in a local Distillery in Portugal. The results reveal that wine pomace has a higher volatile matter content (62.695%) than distillation stillage, which, however, has lower ash content (3.762%) and higher fixed carbon (31.813%). Calorimetric analyses show that distillation stillage has a superior low heating value compared to wine pomace, with values exceeding 19 MJ/kg. Both by-products, however, exceed ENplus(r) limits for ash (\(\leq\)0.70), nitrogen (\(\leq\)0.3), and sulfur (\(\leq\)0.04) content, presenting challenges for use as high-quality fuel pellets. Combining these biomasses with other materials could reduce the pollutant content of the pellet and improve efficiency. This study highlights the need for pre-treatment strategies to lower ash content and enhance combustion. Policy support for sustainable practices is essential to optimize the use of wine pomace and distillation stillage as renewable energy sources. renewable energy sources; agro-industrial by-products; bioenergy; sustainable practices; environmental impact 2024  
[PERSON], [PERSON], [PERSON], A.D.S. Transforming Wine By-Products into Energy: Evaluating Grape Pomace and Distillation Stillage for Biomass Pellet Production. _Appl. Sci._**2024**, _14_, 7313. [[https://doi.org/10.3309/appl4167313](https://doi.org/10.3309/appl4167313)]([https://doi.org/10.3309/appl4167313](https://doi.org/10.3309/appl4167313)) Academic Editors: [PERSON] and [PERSON] Received: 15 July 2024 Received: 10 August 2024 Accepted: 13 August 2024 Published: 20 August 2024 Accepted  
such as high energy content, waste utilization, and the antioxidant properties that aid in biomass preservation, underscore the potential of grape pomace as a valuable resource for sustainable bioenergy production [6; 7]. There are two distinct types of grape pomace. Pomace derived from pressing grapes before fermentation begins, a method commonly used in white wine production, is called fresh pomace. The pomace obtained from pressing grapes after the fermentation process, which is typical in red wine production, is called fermented pomace [5]. Estimates indicate that every 6 liters yields approximately 1 kg of grape pomace, which represents a global production of 10.5 to 13.1 million tons of grape pomace annually [8]. This by-product of wine production is mainly made up of skins, stems, and seeds [3; 9; 10; 11]. Estimates indicate that each ton of grape pomace contains approximately 430 kg of skins, 250 kg of stems, and 230 kg of seeds [12]. Much of this by-product of wine production has been applied as an organic soil impover, as it contains significant amounts of organic matter and is rich in nutrients [13; 14; 15]. However, due to the continuous application of agricultural by-products in agricultural fields, soils are becoming increasingly saturated, posing a significant challenge for large producers in determining the appropriate disposal methods for grape pomace [16; 17]. This saturation can lead to nutrient imbalances, reduced soil fertility, and potential environmental contamination. As a result, producers must explore sustainable disposal and utilization options, such as composting, biogas production, or developing new markets for grape pomace-based products, to mitigate these challenges and ensure environmental compliance.