## 1 Introduction  
Increasingly stringent legal and environmental regulations, coupled with the depletion of conventional fuel resources, are driving the advancement of renewable energy sources (RES) [1, 2, 3]. In 2022, primary energy production in the European Union (EU) amounted to 23,566 PJ, with renewable energy sources contributing approximately 40% (a decrease from 43.2% in 2021) [4, 5]. In Poland, 13.2% of primary energy is derived from renewable sources, including ambient heat, biofuels, biomass, waste, water, wind, solar and geothermal energy. Among this, 4.7% comes from non-wood renewable sources [6, 7]. Renewable energy includes resources such as water, wind, solar, and geothermal energy [8], as well as energy derived from woody biomass, which is produced from tree and shrub residues from forests, agriculture (e.g., orchards), and other sources (e.g., urban greenery) [9]. Fast-growing willow species are the most commonly cultivated energy crops in Poland [10, 11, 12]. Among these, basket willow, also known as _Salix criminalis_, has achieved the highest popularity [13]. It is characterised by significant annual woody mass growth (approximately 14 times that of naturally growing forests) [14, 15]. As a perennial plant,it can yield for 25-30 years after planting. One hectare of willow cultivation produces approximately 10 tons of dry matter annually, with a calorific value of 19.23 MJ/kg [16; 17]. The greatest potential for cost reduction, while adhering to current fuel quality standards, lies in optimising energy inputs at various stages of production technology [18; 19; 20]. Among these stages, biomass grinding is identified as one of the most energy-intensive processes [21]. The blade is the direct working element in the cutting process, interacting with the plant. Its parameters affect the working resistance of machines and the quality of cutting [22]. Cutting resistance is not only influenced by technical parameters (blade angle and cutting speed) but also by the biological properties of the material, and the conditions under which the plant is stored and seasoned. The energy intensity of this process is heavily impacted by material moisture content, the cutting area, and the length of the chips produced [23]. The energy transition and decarbonisation of the power and heating sectors are driving the need for alternative energy sources to replace traditional fuels and meet increasing energy demands [24; 25; 26; 27; 28]. Despite intensified efforts in recent years to promote the widespread use of renewable energy sources, logistical, economic, and technical challenges persist [29; 30]. Biomass is a fuel used in commercial power and heating industries [31; 32]. Its utilisation enables the achievement of the required energy efficiency levels while maintaining low environmental impact [33; 34]. Biomass combustion is the oldest and simplest method of energy conversion. Compared to coal, biomass has a higher volatile content, reduced ash and sulphur content, increased oxygen content, and higher moisture levels, resulting in a significantly lower calorific value than coal [35; 36; 37; 38]. One of the main advantages of biomass is its ability to be stored and pelletised over short time periods. To prepare biomass for combustion in boilers, it must undergo several processing steps, including drying and grinding. In scientific literature and reports on decarbonisation, researchers commonly use the terms \"sustainable biomass\" and \"modern solid biomass\" [39; 40]. Sustainable biomass refers to biomass produced with minimal environmental impact, ensuring support for local communities. This concept includes resource management practices that prevent deforestation, land degradation, biodiversity loss, and excessive water consumption [41; 42]. Modern solid biomass encompasses advanced processing technologies such as pelletisation and briquetting, along with the implementation of high-efficiency, low-emission solid biofuel furnaces and boilers [43; 44].