## 1 Introduction
### Volatile Organic Compound (VOC) Emissions from Biochar  
One of the remaining issues related to the development of torrefaction technology for MSW is mitigating the potential impact of VOC emissions from biochar, including CRDF [17]. Many VOCs cause negative effects on human life and health. According to EU law, a VOC is defined as any organic compound or creosote fraction that, at 293.15 K, has a vapor pressure of no less than 0.01 kPa, or having equivalent volatility under specific conditions of use [18]. However, in EU legislation there is also another definition for VOC, that is, any organic compound with an initial boiling point of less than or equal to 250 \({}^{\circ}\)C, measured at a standard pressure of 101.3 kPa [19]. In turn, in the United States, VOCs are defined as any carbon compound, excluding CO, CO\({}_{2}\), H\({}_{2}\)CO\({}_{3}\), metal carbides or carbonates, and (NH\({}_{4}\))\({}_{2}\)CO\({}_{3}\), which participates in atmospheric photochemical reactions [20]. The most common VOCs are halogenated compounds, aldehydes, alcohols, ketones, aromatic compounds, and ethers [21]. The World Health Organization [22] classifies organic pollutants into three groups by boiling point: very VOCs (VVOCs), 0 to 50-100 \({}^{\circ}\)C; VOCs, 50-100 to 240-260 \({}^{\circ}\)C; and semi-VOCs (SVOCs), 240-260 to 380-400 \({}^{\circ}\)C.  
The health effects of VOC emissions from CRDF could be concerning, especially when considering inhalation during production, handling, storage, transportation, and use. Some VOCs are classified as highly reactive, mutagenic, and carcinogenic. Even small concentrations of these VOCs can cause health problems and chronic diseases, and even be fatal. According to a study conducted by the U.S. Environmental Protection Agency [23], VOCs are responsible for 35%-55% of lung-cancer risk [24] and contribute to photochemical smog [25]. It was proven that VOCs can directly inhibit microbiological and plant processes [26; 27]. A provision was made that VOC emissions should be halved from the released amount in 2000 [25] as a consequence of increased knowledge and awareness of their negative impact on human health and the environment in the Goteborg Protocol. To date, there are only a few studies on the qualitative and quantitative analysis of VOCs in biochars derived from biomass. The occurrence of up to 140 VOCs was reported [26], of which 74 were identified. The most frequently observed compounds in biochar are acetone, benzene, methyl ethyl ketone, toluene, methyl acetate, ethanol, phenol, and cresols. According to [PERSON] et al. [28], biochars are associated with aliphatic acids and naphthalene. Char Team 2015 reported 26 VOCs [29]. The potential problem of VOCs in biochar was also noticed by [PERSON] et al. [30], who analyzed biochar from composted MSW. Compost was thermally processed at temperatures ranging from 450 to 650 \({}^{\circ}\)C. Different VOC types were detected, including alkylbenzenes, methoxyalkylphenols, N-containing VOCs, furans, and the BTEX group. Their percentage share varied depending on thermal-process conditions. The generation of the BTEX group to obtain biocarbon from raw materials is of significant concern. The highest concentrations were found for naphthalene, toluene, phenol, benzonitrile, and several compounds with the ester group. [PERSON] et al. [31] reported the presence of polycyclic aromatic hydrocarbons (PAHs), with concentration ranging from <0.1 to >10,000 mg\(\cdot\)kg\({}^{-1}\). The highest concentrations were found for naphthalene and phenanthrene. In recent work, [PERSON] et al. [17] found 84 VOCs in the headspace of CRDF produced from municipal waste, including many that are classified as toxic, e.g., benzene or toluene derivatives. The highest emission was measured for nonanal, octanal, heptanal. The top 10 most emitted VOCs consisted of almost 65% of total emissions.