# Application of Fly Ash Obtained from the Incineration of Municipal Solid Waste in Agriculture
## 2 The Chemical Composition of Fly Ash from the Incineration of Municipal Solid Waste  
The fly ash obtained from municipal solid waste incineration contains the following elements: silicon, aluminum, iron, magnesium, calcium, phosphorus, potassium, and chlorine (Table 1), and the following oxides: aluminum oxide, silicon oxide, sodium oxide, calcium oxide, potassium oxide, and iron oxide (Table 2) [26]. SiO\({}_{2}\) and CaO are in a higher concentration (Table 2). The fly ash obtained from the incineration of municipal solid waste is characterized by particles that are moved with the help of combustion gases, which are subsequently eliminated [28; 29]. The nutrients that the soil needs are contained in the ash obtained from the incineration of municipal solid waste (Table 1) [30; 31]. The chemical composition of fly ash obtained from the incineration of municipal solid waste is diverse and depends on the quality of the burned materials and the fly ash treatment methods.  
According to Table 1, the concentration of some elements necessary for the growth of plants in the ash is higher than in the soil, such as potassium, phosphorus, copper, iron,  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Element** & **Unit** & **FA [30]** & **Soil [30]** & **Soil [31]** & **Soil [32]** \\ \hline Ca & \% & 0.11–22.2 & 0.7–50 & - & - \\ S & \% & 0.1–1.5 & 0.01–2.0 & - & - \\ Al & \% & 0.1–17.3 & 4–30 & - & - \\ Si & \% & - & - & - & - \\ Na & \% & 0.01–2.03 & 0.04–3.0 & - & - \\ K & \% & 0.15–3.5 & 0.04–3.0 & - & - \\ Cl & \% & - & - & - & - \\ Mg & \% & 0.04–7.6 & 0.06–0.6 & - & - \\ Fe & \% & 36–1333 & 0.7–55 & - & - \\ As & mg/kg & 2.3–6300 & 0.1–40 & 5–15 & 20 \\ Ba & mg/kg & - & - & 200–400 & - \\ Cd & mg/kg & 0.7–130 & 0.01–7.0 & 1–3 & 1–3 \\ Co & mg/kg & 7–520 & 1–40 & 15–30 & - \\ Cr & mg/kg & 10–1000 & 5–3000 & 30–100 & 100 \\ Cu & mg/kg & 14–2800 & 2–100 & 20–100 & 50–140 \\ Mo & mg/kg & 7–160 & 0.2–5.0 & 2–5 & - \\ Ni & mg/kg & 6.3–4300 & 10–1000 & 20–75 & 30–75 \\ Pb & mg/kg & 3.1–5000 & 2–100 & 20–100 & 50–300 \\ Sr & mg/kg & - & - & - & - \\ V & mg/kg & - & - & 50–100 & - \\ Zn & mg/kg & 10–3500 & 10–300 & 100–300 & 150–300 \\ Sb & mg/kg & - & - & 5–20 & - \\ P & mg/kg & 0.004–0.8\% & 0.005–0.2\% & - & - \\ Hg & - & 0.02–1.0 & - & 0.1–1 & 1–5 \\ Mn & - & 58–3000 & 100–4000 & 900–1500 & - \\ TOC & g/kg & - & - & - & - \\ Ti & \% & - & - & - & - \\ Ag & - & - & - & 2–20 & - \\ B & - & 10–618 & 2–100 & 1–2 & - \\ Se & - & 0.2–134 & 0.1–2.0 & 1–3 & - \\ \hline \hline \end{tabular}
\end{table}
Table 1: Components of fly ash (FA) from incineration units and soil (mg/kg) (data from [30; 31; 32]).  
molybdenum, zinc, and boron. The minimum values of the concentration of heavy metals do not exceed the standardized limits.  
According to [PERSON] et al. [33], the permissible limit of metals in the soil may vary depending on the type and characteristics of the soil. Heavy metals at high concentrations in the soil can have a negative impact on crops, inhibiting their growth. An alkaline soil pH can restrict metal mobilization in the soil matrix, thus controlling metal uptake by crops and reducing the risk of metal toxicity [34; 35].  
Many types of residues are generated during the waste combustion stage in the combustion chamber or in the flue gas purification part. In the waste incineration stage in the combustion chamber, residues such as bottom ash result in the second part, depending on the type of installation, boiler ash from the area of the heat recovery economizer and other types of residues result [36].  
Oxides contained in fly ash are presented in Table 2. In fly ash, the highest concentration is SiO\({}_{2}\), and the content of calcium oxide (CaO) in fly ash can reduce soil acidity [37].