10.48788/DVUA/CFSY4TOstroha, RuslanRuslanOstroha0000-0003-0045-3416Sumy State UniversityMija, AliceAliceMija0000-0001-5208-5956Université Côte d'AzurCibotaru, SanduSanduCibotaru0000-0002-9080-9502Université Côte d'AzurSkydanenko, MaksymMaksymSkydanenko0000-0002-0277-1867Sumy State UniversityBataltsev, YevhenYevhenBataltsev0000-0003-2035-2014Sumy State UniversityDataverseUA2025Agricultural SciencesEarth and Environmental SciencesFTIR spectroscopyDigestatePeatBiocharAmmonium sulfateOstroha, RuslanRuslanOstrohaSumy State University2025-12-202026-01-08Spectral Data646026531356959583053264image/pngimage/pngimage/pngimage/pngtext/plain2.0CC BY 4.0<p>This dataset contains graphical representations (.png) of FTIR spectra for four organic and organo-mineral samples. The spectral analysis was performed to identify functional group changes during the valorization of digestate.</p> <b>List of analyzed samples:</b> <ol> <li>Peat (Reference material)</li> <li>Solid Digestate (Raw material from anaerobic digestion)</li> <li>Digestate Biochar (Pyrolyzed digestate)</li> <li>Digestate + (NH₄)₂SO₄ (Organo-mineral fertilizer enriched with ammonium sulfate)</li> </ol> <b>Methodology:</b> <p>The FTIR spectra were recorded using a Nicolet iS50 FT-IR spectrometer (Thermo Fisher Scientific, USA) equipped with a GladiATR diamond ATR accessory (PIKE Technologies, USA). Measurements were performed at a resolution of 2 cm^-1, with 32 scans, in the spectral range of 4000–600 cm^-1.</p><p>The dataset consists of 4 image files (PNG format).</p> <b>File naming convention:</b> <ul> <li><code>FTIR_Sample_01_Peat.png</code> – Spectrum of peat sample.</li> <li><code>FTIR_Sample_02_Digestate.png</code> – Spectrum of raw digestate solids.</li> <li><code>FTIR_Sample_03_Digestate_Biochar.png</code> – Spectrum of biochar derived from digestate.</li> <li><code>FTIR_Sample_04_Digestate_AmmoniumSulfate.png</code> – Spectrum of digestate enriched with (NH₄)₂SO₄.</li> </ul>Ministry of Education and Science of Ukraine0125U000500French Government within the NADIYA Programme2025-435