## 5 The Use of Hemp Biomass for Biofuels Production  
The need for rational use of energy resources and a significant reduction in fossil fuel consumption in favor of sustainable renewable sources has been noticed for years and is reflected in legislation, both EU and national. Biofuels derived from plant biomass are mentioned in many documents and legal acts concerning long-term energy strategies. Therefore, it is highly justified to search for and develop solutions leading to the most effective use of this source of green energy. Biomass, both plant and animal, is regarded as an alternative energy source to fossil fuels. Even though significant amounts of energy are needed for their production and processing, their energy management is less inconvenient for the environment than the use of petroleum, lignite, or hard coal [64; 65; 66]. This is due to its absorption of CO\({}_{2}\) during plant growth, which significantly reduces the overall balance of the impact of biomass production on the ecosystem [67; 68]. Plant biomass can be used to produce solid, liquid, and gaseous biofuels (Figure 6). The figure below shows the structure of industrial hemp cultivation in Europe (Figure 7). According to various sources, the average yield of hemp straw, depending on the variety, climatic and soil conditions, and type of plantation, ranges from about 10 to 20 t\(\cdot\)ha\({}^{-1}\)[13; 70]. Hemp biomass can be used to produce solid as well as liquid and gaseous biofuels (Figure 8). Figure 6: Schematic of using hemp biomass for energy purposes [69]. Figure 7: Hemp cultivation area in Europe in 2018 [10]. For solid biofuel production, waste biomass from various types of processing or from energy crops with a high content of lignocellulosic compounds is usually used. The most commonly produced solid biofuels are briquettes and pellets. They are intended mainly for combustion in household stores [72; 73; 74]. Hemp biomass, which is waste from hemp cultivation for various purposes, e.g., seed, food, cosmetics, or pharmaceuticals, can be successfully used for the production of solid biofuels. For example, in cultivation for seed or grain, whole stalks and threshing are waste; in fiber crops, they are shives, respectively. The hemp biomass at 8.5% humidity has a high content of cellulose--more than 40%--and hemicellulose--almost 30% (Figure 9), which makes it a valuable material for solid biofuel production, such as pellets or briquettes. In addition, hemp biomass heat of combustion is 18,300 kJ\(\cdot\)kg\({}^{-1}\), and the calorific value is 17,100 kJ\(\cdot\)kg\({}^{-1}\)[71]. The heat of combustion of hemp biomass is higher than the heat of combustion of other popular energy crops such as _Hibiscus cannabirus_ (15,800 kJ\(\cdot\)kg\({}^{-1}\)), _Ripariosida hermaphrodita_ (17,200 kJ\(\cdot\)kg\({}^{-1}\)), and _Brassica napus_ var. _nupus_ (17,600 kJ\(\cdot\)kg\({}^{-1}\)). Nevertheless, the calorific value is slightly lower than the calorific value of _Triticum_ straw (18,700 kJ\(\cdot\)kg\({}^{-1}\)) [75]. Solid biofuels from hemp biomass have a higher energy yield compared to other hemp biofuels such as biogas and liquid biofuels [76]. They can also be produced and used locally, even on individual farms or by small groups of farmers in the vicinity of hemp plantations. Liquid biofuels are substitutes or additives to diesel oil [77]. In Poland, biocomponents are not used themselves [78], due to the low temperatures in winter, which could freeze the fuel in the tanks [79; 80]. The use of biofuels may have a lower environmental impact than the use of diesel [81]. Nevertheless, the production of liquid biofuels is energy- and cost-intensive; hence, numerous studies have been conducted in the field of optimizing production efficiency and minimizing bioethanol production costs [82; 83; 84; 85]. Figure 8: Schematic of the possibility of using hemp biomass for the production of biofuels [71]. Figure 9: Henola variety biomass chemical composition [71].