# Biomass from Green Areas and Its Use for Energy Purposes
## 1 Introduction
\begin{table}
\begin{tabular}{c c} \hline \hline
**Biomass Waste** & **Calorific Value** \\  & **MJ**-**kg\({}^{-1}\)** \\ \hline Wood chips from vineyard pruning [11] & 18.07 \\ \hline Corncob [12] & 17.0 \\ \hline Olive husk [12] & 20.9 \\ \hline Sunflower shell [12] & 18.0 \\ \hline Walnut shell [12] & 21.6 \\ \hline Hazelnut shell [12] & 20.2 \\ \hline Tomato residue [12] & 11.3 \\ \hline Wood bark [12] & 20.5 \\ \hline Barley straw [13] & 18.2 \\ \hline Sugarcane bagasse [13] & 20.0 \\ \hline Pine bark [14] & 20.4 \\ \hline Cotton stalks [14] & 19.0 \\ \hline Bagasse [14] & 21.2 \\ \hline Wood chips [14] & 20.9 \\ \hline Rice husk [14] & 15.1 \\ \hline Pine sawdust [15] & 18.3 \\ \hline Saw dust [16] & 17.7 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Raw materials used for the production of solid fuels and their calorific value. In addition to the commonly used types of biomass, such as wood and energy plants, there are other materials that need to be used to generate electricity. These include both household waste and residues from the care of urban greenery, falling leaves, grass, and tree branches [18; 19]. The term \"urban greenery\" means vegetation complexes, especially parks and greenery in squares, streets, and allotment gardens. All managed waste resulting from plant care, such as leaves, moved grass, tree branches, flowers, weeds, and seeds, is extremely important in economic and ecological terms. In most cases, this biomass, after being collected, is transported to landfills and composted there. It is worth paying attention to the energy potential of this raw material and its use as a source of energy because waste in green areas is generated regularly and throughout the year [2]. The management of waste from green areas Is a topic that is currently being discussed in many countries. In Italy, biomass from urban green areas is considered \"hazardous waste\". This biomass is properly processed and disposed of [20]. In the United States of America, the great potential of biomass from urban greenery has been noticed. It was concluded that additional research is needed to determine its potential [21]. Green biomass is not used for energy purposes, and specialized companies deal with its disposal in Germany [22]. In Spain, attention has been paid to the potential of biomass from the maintenance of ornamental plants and urban trees [23; 24; 25]. The most popular form of waste management for green areas is composting [26], which results in the production of fertilizer [27]. Obtaining energy by incinerating waste from green areas is another method of managing this type of waste. In order to obtain energy, biomass that is fragmented or in the form of plriquettes or pellets has been used [2]. Another way to use green waste is the production of biogas. Grass is best suited for this purpose because it does not contain too many impurities [28]. In order to valorize plant biomass, the process of so-called torrefraction is used. This involves gentle roasting of the biomass at a temperature of approx. 200-350 \({}^{\circ}\)C without access to oxygen, under atmospheric pressure. As a result of this process, a solid product is obtained, the so-called torrefied biomass, which, compared to raw biomass, has more favorable physicochemical properties when used as fuel in the power industry. In addition, torrefied is more durable and more homogeneous than solid biomass, which is important when using plant biomass [29]. [PERSON] et al. [30] studied the properties of sugar cane pellets subjected to dry and wet torrefraction. They found that the wet torrefraction process can significantly reduce the ash content of the finished product (ash content below 1% at a torrefraction temperature above 180 \({}^{\circ}\)C), resulting in a higher quality of the solid fuels tested. In turn, the calorific value of dry torrefied pellets was higher by 0.27 MJ compared to wet torrefied pellets. The production of pellets from heat-treated bagasse has been shown to be economically viable.