# Gases Emissions during Compositing Process of Agri-Food Industry Waste
## 1 Introduction  
Forecasts made by the United Nations predict uninterrupted population growth for the next 80 years--from 7.9 billion today to nearly 11 billion by the end of the 21 st century. [1]. In this context, uninterrupted population growth is also the cause of considerable amount of waste from the agro-food industry [2]. In Poland, vegetables and fruits production covering the area of no more than 3% of agricultural land, is more than 36% of plant production and 14-15% of the whole agricultural production [3]. When harvesting and processing the vegetables large amounts of waste are formed [4]. The source of their origin are unclassified vegetables, non-commercial parts of the plants or processing waste. These wastes are frequently characterized by a considerable moisture level and high content of organic matter [5]. The use of post-production residues from the vegetable sector is a good example of a closed loop economy, which the main aims is the reduce of the carbon footprint [6]. There are many possibilities for managing waste from vegetable production. Some of them will also allow the recovery of energy that is contained in waste biomass. Those processes will allow not only to manage the wastes but moreover will be the actions protecting the environment, which already have gained importance in recent years [7, 8]. Biological and chemical processes used today include anaerobic digestion, aerobic digestion, thermophilic anaerobic digestion, composting, gasification, pyrolysis, and incineration [9, 10]. Increasingly often are created the installations allowing not only for waste management but also on energy recovery from the waste biomass [11]. The processes of combustion, gasification and pyrolysis are classified as thermal methods of converting matter [12]. The differences that exist between each of the aforementioned processes are primarily the different conditions under which they are carried out and the non-uniform end products [13]. Carrying out the incineration of bio-waste requires supplying significant amounts of energy along with excess air [14]. The resulting end products have no possibility of reuse. A more energy-advantageous process is gasification, which yields a combustible gas that is used in industry. Biomass pyrolysis, in contrast with the other processes, proceeds without air. The resulting products are usually bio-oils characterized by high energy density [12]. One of the biological method of organic waste disposal, which among others includes the agri-food ones is a biogas production [15]. The biogas is obtained in consequence of the methane fermentation process from the substrates placed in the fermentation chamber. It is a mixture of gases among which the methane is dominant. The biggest advantage of this process is the energy yield, both the electricity and [16; 17]. The biofuels production from the waste or algae is gaining an importance in recent years, hence it is important to define the processes being the source of energy [18]. The disadvantages include the relatively large investment costs and the need for regular supply of substrates to the biogas plant, so as not to stop the fermentation process [19]. Biological methods such as composting are among the options for use of waste, which is significantly hydrated and high content of organic matter. In addition to high organic matter content, feedstock materials must have an optimal carbon and nitrogen ratio [20]. This process requires the presence of oxygen, however, it occurs naturally under the influence of microorganisms [21]. The compost is a fertilizer rich in organic matter and chemicals desired by plants. Another advantage is reduction of the mass and volume of the waste by water evaporation, which is caused by high temperatures during the composting [22; 23]. Moreover the high temperatures will help to improve the sanitary condition of the compost mix [24]. Gaseous emissions during the composting process are a key parameter. The relationship between O\({}_{2}\) and CO\({}_{2}\) showed that the decomposition is correct.