## 1 Introduction  
The world population has already reached 7 billion and will reach 9.7 billion by 2050 [1]. As the population grows, so does the demand for arable land and high quality food all year round. To meet this, fertigation is used in conventional farming, which entails problems of excessive soil salinization. Common causes of excessive salinity also include poor agricultural practices, the use of excessive mineral fertilizers and a hot climate [2, 3]. The solution to these problems in most countries of the world is soilless cultivation using mineral and organic substrates, inert to plants. Soilless cultivation has many advantages, one of which is isolation of the plant from the soil, which is often heterogeneous. Intensively exploited, the soil may be degraded, become a habitat of pathogenic pathogens, and in addition is often excessively saline [2; 3; 4]. Controlled growing conditions in hydroponic systems allow a significant increase in production efficiency compared to conventional methods [4]. High efficiency and healthiness of cultivation are ensured by a substrate with appropriate, stable physical properties [1; 5]. This is usually mineral wool, which is a versatile substrate, widely used in the commercial cultivation of vegetables and other plants. Mineral wool in year-round cultivation is usually used for one season, which leads to the creation of a large amount of post-production waste, of which only a small part is recycled or reused for cultivation [6; 7; 8; 9]. The process of utilization of mineral wool after cultivation itself is expensive and is not neutral for the environment, and mineral wool stored outside production facilities, without any protection, may adversely affect human health [9]. Annually, from the area of 1 ha of greenhouses, about 150 m\({}^{3}\) of used mineral wool remains after cultivation. The production of such an amount of mineral wool emits to the atmosphere approximately 26 tons of CO\({}_{2}\)[6; 10]. The growing awareness of ecology and problems with mineral wool utilization have contributed to the search for new pro-ecological substrates that will be fully biodegradable [9]. New substrates being investigated for hydroponic cultivation include wood industry waste, composts or biocarbon produced from many types of waste [10; 11; 12]. Plant residues such as grape pomace and nut and almond shells are also being tested, along with many others [13; 14; 15]. These substrates are often used in mixtures with other organic or mineral substrates, such as perlite or vermiculite, in order to improve physical properties [8; 16]. Another type of organic substrate is lignite, which retains a stable homogeneous structure due to its highly condensed matter. Its suitability has been studied in tomato, cucumber and other vegetable and soft fruit cultivation [17; 18; 19]. Lignite has good, stable physical properties that allow it to be used for a longer period of time [19]. Additionally, during its production, CO\({}_{2}\) emission is reduced by almost 40% in comparison to the production of the substrate from mineral wool [20]. Lignite mining is associated with negative social and environmental impacts, but it also has some benefits. Mining itself can cause rapid development of areas rich in coal resources by creating new jobs and developing infrastructure [21]. However, the exploitation of springs can take years, and during this period, negative effects on agriculture and the environment can occur, as well as have a negative impact on the mental and physical health of neighboring residents [22]. Positive public attitudes about lignite mining are linked to perceptions of employment opportunities, cheaper fuel and energy [23; 24]. The increase in CO\({}_{2}\) and greenhouse gas emissions from the electricity sector has forced a gradual shift away from the use of lignite as a fossil fuel. Coal extracted from low seams can be used for food production, is not used as a fuel, and, therefore, does not emit CO\({}_{2}\) or greenhouse gases. [PERSON] et al.