## 3 Results  
Comparisons of VOC emissions potential for 84 compounds (mass of VOC emitted per mass of CRDF) and the % mitigation rate are summarized in Table 1.  
Identified compounds have been organized to five groups:  
1. alkyl derivatives of benzene or phenols (possible carcinogens) (32 compounds with an emission of 4196.92 ug/kg (ground) and 576.28 ug/kg (pelletized));
2. alkyl derivatives of two-ring aromatic hydrocarbon (16 compounds with an emmision of 1367 ug/kg (ground) and 178 ug/kg (pelletized));
3. Figure 1: The experimental procedure used to measure VOC emissions from stored carbonized refuse-derived fuel. GC-MS—gas chromatography with mass spectrometry, GC—gas chromatography, MS—mass spectrometry, SPME—solid-phase microextraction, VOCs—volatile organic compounds, CRDF—carbonized refuse-derived fuel. * derivatives of heterocyclic amines (7 compounds, with an emission of 170 \(\upmu\)g/kg (ground) and 23 \(\upmu\)g/kg (pelletized));
* compounds that are generally considered as lower risk (e.g., present naturally in food) (22 compounds with an emission of 8097 \(\upmu\)g/kg (ground) and 1113 \(\upmu\)g/kg (pelletized));
* belonging to other groups or with an unknown structure (7 compounds with an emission of 662 \(\upmu\)g/kg (ground) and 95 \(\upmu\)g/kg (pelletized). According to [37], the 11 compounds were identified as immediately dangerous to life or health (IDLH), these being emissions 1196 (8.25% of total emission) and 157 (7.86% of total emission) \(\upmu\)g/kg from ground and pelletized forms, respectively. Moreover, 52 compounds have a flash point below 100 \({}^{\circ}\)C (emissions 142 (0.98% of total emission) and 20 (1.0% of total emission) \(\upmu\)g/kg from ground and pelletized form, respectively), while 3 of them have flash points in the range of 100-150 \({}^{\circ}\)C.  
In the case of 37 of the compounds: the lower explosive limit (LEL) was identified [37], and was present in emission rates 10420 (71.84% of total emission) and 1424 (71.31% of total emission) \(\upmu\)g/kg before and after pelletization, respectively. The emissions of the mentioned compounds causes the risk of a toxic effect on humans, but also the risk of self-ignition, and in consequence fire or explosion. Therefore, the problem of the control and mitigation of the emissions of these compounds from CRDF should be solved. One of the proposed methods is pelletization. Pelletization reduced the total VOC emission rate by 86% for four days of CRDF storage. In most cases (except for five VOCs) the pelletization reduced the emission rate. This preliminary study revealed that VOCs emission mitigation due to pelletization was highly effective. Emissions of 75 of the identified VOCs were reduced with an efficiency higher than 80%. One of the potential explanations could be the decrease of the contact surface area by densification of the CRDF structure. Pelletization likely decreases the porosity and VOCs adsorbed, or those present inside pores are displaced from CRDF as pore space becomes smaller. Our findings are consistent with the observation of the influence of wood pelletization on VOCs emissions. It has been shown that during wood pellet production, only \(\sim\)30-40% of the initial terpen remain in the wood after dying, 20-30% remain after grinding, and 10-15% remain after pelletization [22]. It is also known that wood undergoes several chemical changes during the process of pelletization. [PERSON] and [PERSON] [47] determined the change in the pH value of wood during the different steps of pellet making and established that the pH value of spruce wood decreases noticeably, and the alkaline buffering capacity increases significantly during the process of pellet making. Moreover, the amount of cold-water extractives of spruce wood increases, indicating some hydrothermal degradation of wood during the process of pellet making. Especially, the pressing process at high temperature and pressure appears to thermally degrade wood [36].