# Selective Collection and Management of Biowaste from the Municipal Sector in Poland: A Review
## 1 Introduction  
Waste management is one of the important challenges in reducing adverse environmental changes [1; 2]. As defined in the Polish Act on Waste of 14 December 2012 [3], waste means any substance or object the holder disposes of, intends to dispose of, or is obligated to dispose of. The waste generated can be divided into the industry and municipal sectors. Among municipal waste, biodegradable waste plays an important role. According to the Polish Act on Waste of 14 December 2012 [3], biodegradable waste is defined as waste that undergoes aerobic or anaerobic decomposition with the participation of microorganisms. This waste is a broad group where many substrates, such as grass, leaves, branches, peelings, spoiled vegetables, and fruits, can be mentioned. The unique role of biodegradable waste, including biowaste, is due to the quantities in which they are generated daily and their specific properties [4]. This includes the high water content and susceptibility to decomposition under the influence of microorganisms, both under aerobic and anaerobic conditions [5]. In many countries, including Poland, the waste in question is collected selectively following the Regulation of the Minister of Climate and Environment of 10 May 2021 on the method of selective collection of selected waste fractions [6]. This is supported by its properties, which allow them to be recycled or recovered relatively quickly [7]. Often, this waste is the dominant fraction of all waste from the municipal sector--both in developedand developing countries [8]. Consequently, biowaste management is a critical component of the overall municipal waste management system [9]. There are several main directions for biowaste management. Among them are landfilling, thermal conversion, and management through recycling and recovery processes. According to the Regulation of the Ministry of Economy and Labor on the criteria and procedures for admission of waste to respective landfill types [10], the selectively collected municipal waste from group 20 (including biodegradable waste in the group of municipal waste) as defined in the waste catalog [11] undergoes classification along with other selectively collected municipal waste fractions. In accordance with Article 122, Polish Act on Waste [3], there is no possibility to landfill selectively collected biodegradable waste. This means that biogas from landfilled waste will be significantly reduced. Another potential option is to manage municipal waste in thermal waste conversion facilities, commonly known as incinerators [12]. For several years, these installations have become increasingly popular in Poland [13]. In Poland, in 2020, there were eight installations for the thermal conversion of municipal waste. The total capacity of these installations was 1.159 million tons, and they mainly processed municipal waste and waste from municipal waste management [14]. Among the main advantages of waste disposal by incineration is the reduction of waste mass and volume. The disadvantage, however, is the lack of recovery of numerous raw materials found in the mixed municipal waste stream. Additionally, in the case of biowaste, a problem that reduces the effectiveness of this solution is the high degree of hydration of thermally converted waste [15]. Before the incineration process, energy is needed to evaporate the water. The high water content, a ballast in thermal processes [16], is an advantage in biological waste conversion processes. This is because water is necessary for microorganisms to function appropriately and decompose the organic matter found in the waste being processed [17]. Depending on whether the process takes place under aerobic or anaerobic conditions, composting [18] and biogas production can occur using the anaerobic digestion process can occur [19; 20]. With the right quality of collected substrates, it is possible to produce energy from both systems, especially in the anaerobic digestion process [21].