# Gases Emissions during Compositing Process of Agri-Food Industry Waste
## 3 Results and Discussion
### Changes of Gases Emissions  
Gaseous emissions from the composting piles are equally important parameter informing about the proper course of composting process as the temperature changes [35]. Among the gases in the reactor chamber the most important are oxygen and carbon dioxide. It is the presence of the first one in excess of 10% that influences the process correctness. When its concentration falls below 5% can develop anaerobic conditions that cause rotting of the compost [36]. The evidence of this is mainly the appearance of the methane at the level of 0.1% and the hydrogen sulfide in concentration from about 200 ppm and higher. In the analyzed compost mixtures no methane emissions were measured, and the oxygen flow was maintained at the level of 10%. In the second chamber (K2), wherein the process run most rapidly the oxygen concentration fell below 5% on the second day. This proved a very rapid decomposition of organic materials by the microorganisms. After a decline below 5% the flow of the air entering the chamber increased from 2 dm\({}^{3}\)/min do 3.5 dm\({}^{3}\)/min so to avoid rotting (Figure 3). The similar situation took place in the first chamber (K1), however it occurred much later (7 th and 8 th day) than in the second and third chambers. This proves that the thermophilic phase also run clearly however after a long time than it was in the other reactors. The lowest concentration of oxygen in the third chamber took place on the second day and amounted 7.6%. Those changes are shown in Figure 5. The oxygen concentrations in mixtures are dependent mainly on substrates which are the composition of the feedstock for composting. In studies [PERSON] et al. [32] for example, concentrations below 15% occurred over a longer period of time. Similar results in the oxygen content have been demonstrated in research of [PERSON] et al., [37] where the substrate was the cattle manure. The emission of carbon dioxide is an important parameter of biological changes [38]. Its level is closely correlated with the oxygen values. This is due to the fact that the sum of the concentrations of those gases should be close to their sum in the atmospheric air. After intensive phase involving heat release and significant emission of carbon dioxide the levels of CO\({}_{2}\) started to decrease. First it was in the chambers 2 and 3 and after day 7 th also in the first reactor (Figure 6). The 40 th day of composting was noticeable relatively large  
Figure 5: Concentration of the oxygen in the exhausted gas in analyzed composts. peak for the curve of the second reactor. It shows an increased decomposition of organic matter, which was caused by additional aeration by mixing of whole material in 35 th day of the experiment. A specific gas produced mainly by the decomposition of the proteins (including the amino acids) is ammonia. As it is well known, the use of natural fertilizers such as slurry or manure is related to the emissions of this gas into the environment. There is no difference in the case of organic fertilizer that is compost. Thus, the fertilizers management can be a real threat to the functioning of ecosystems and the biosphere [39, 40]. This concerns not only fertilizers but also other types of biomass from agriculture or agri-food industry [41]. The detection limit for the discussed gas is within the range of 15-25 ppm. Above 400 ppm are visible symptoms such as irritation of the eyes and respiratory tract [42]. Hence, it is important to control this gas both in reactor composting and in piles. In the reactors this gas can be captured and purified which should not be carried out in piles in the open air. As it is shown in Figure 7 the ammonia emissions in compost vegetable waste were significantly high during the first week of composting. For the first chamber the maximum emission was 295 ppm (4 th day), and for the second reactor 332 ppm in the third day. In the third chamber the maximum emission was 146 ppm.