# Application of Near-Infrared Spectroscopy for Monitoring and/or Control of Composting Processes
## 5 Use of NIR Spectroscopy to Monitor and/or Control the Composing Process
 &
\begin{tabular}{c} Results showed that the determination \\ coefficient of calibration (\(R^{2}\)) and the \\ standard error of estimate (SEE) were \\ for moisture (0. \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Type of Composting** & **Composting Material** & **Spectroscopic Method and Chemometrics** & **Specific Results** & **Reference** \\ \hline Composting pile monitored for 135 days. & 10 m\({}^{3}\) of thick sludge was mixed with 5 m\({}^{3}\) of fresh green waste in pile 8 m long and 1.5 m high. & FTIR detection of components of biodegradation that can be easily assimilated by microorganisms (e.g., certain aliphatic and peptide structures and carbohydrates, including celluloses and hemicelluloses). & [87] \\ \hline Composting pile monitored for 1 year. & 280 kg olive marc, 20 kg wheat straw, and 85 L of olive-m wastewater. & FTIR spectroscopy in the wavelength range 2500–25,000 nm. & The FTIR spectra revealed that the aromatic groups were enriched and the aliphatic groups were degraded throughout composting. & [88] \\ \hline  & Four experiments were performed: (i) powdered cellulose + ammonium-nitrate mixed with the soil, (ii) green manure as chopped entive leaves mixed with the soil, mixed with the soil, (iii) ammonium-nitrate mixed into the substrate, with no organic amendment and (iv) with no inorganic supplements. & & \\ \hline  & Four substrates were tested: (i) organic fraction of municipal solid waste, (ii) of organic fraction of municipal solid waste with orange peel waste, (iii) sewage sludge with building agent, and (iv) mixture of strawberry extrudate, fish waste, sewage sludge, and bulking agent. & & \\ \hline  & Mixture of different organic waste, including urban organic waste, organic waste, organic residuals, and biochar mixed with vegetable active principles. & Hyperspectral imaging analysis in the NIR wavelength range (1000–1700 nm) & Respectable correlations were achieved for all the studied variables, with \(R^{2}\) values of 0.93, 0.85, 0.89, and 0.96 for pH, electrical conductivity, soluble total organic carbon, and soluble total nitrogen. & [91] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: _Cont._Taking into account that it is critical to quickly and correctly assess the maturity, stability, and fertility of waste products during the composite process, [PERSON] et al. [93] analyzed the changes in the compost of sewage sludges and green wastes (one-third of crushed green waste, one-third of pine bark, and one-third of municipal sewage sludge) using NIR reflectance spectroscopy coupled with partial least squares regression during 180 days of the composting process. The authors stated that the validation of the composting time forecast model enabled for the determination of C, N, C/N, and the stage of composting of unknown composts by incorporating the NIRS spectrum into the model and comparing it to those in the data library. NIRS provided more accurate information about decomposition duration without using a complex traditional analytical method. Moreover, [PERSON] et al. [94] used ultraviolet-visible-near-infrared (UV-VNIR) spectroscopy in the wavelength range of 190-1000 nm to quantify the degree of maturity of compost based on compost extracts' spectra. The compost was produced by mixing city sewer sludge, sawdust, and chopped wheat fiber in a 4:3:1 proportion. By introducing additional waste materials, such as wheat straw, rice straw, cotton waste, or sawdust, as bulking agents, the composting process was enhanced. The chemical components of the compost were correlated with the UV and VNIR wavelengths using PLSR. PLSR models for the UV (220-400 nm) and VNIR (400-1000 nm) spectrum wavelengths were developed. Total organic matter was measured more accurately in the 700-1000 nm spectral region. The overall extractable carbon had a stronger association with VNIR spectra, particularly the visible spectral region.