Machines. Technologies. Materials.
Vol. 20 (2026), Issue 1, pg(s) 38-44

MATERIALS

Fermented grape pomace ash – by-product of rakia (brandy) production

  • 1 Institute of Mineralogy and Crystallography, Bulgarian Academy of Sciences, Sofia, Bulgaria;

Abstract

This study investigates the chemical, mineralogical, and functional characteristics of fermented grape pomace ash generated after brandy production and subsequent combustion. Semi-quantitative WDXRF analysis revealed a Ca–K–P-dominated composition with high alkalinity, significant phosphorus content, and notable copper concentration. The water-soluble fraction of the ash was determined to be 17.1 wt.%, indicating a moderate content of mobile inorganic salts that may influence leaching behaviour and environmental compatibility. XRD and vibrational spectroscopy confirmed the presence of lime, calcite, silicates, sulphates, and calcium phosphate phases, including hydroxyapatite, together with a significant amorphous fraction and residual carbon. UV–Vis analysis indicated partial reduction of copper species to metallic nanoparticles, suggesting heterogeneous redox conditions during thermal treatment. The combined composition confers potential functionality in soil amendment, mineral carbonation for CO₂ sequestration, and incorporation into cementitious or alkali-activated systems, although soluble salts and copper mobility represent critical constraints, requiring application-specific environmental and performance assessment.

Keywords

References

  1. Miranda, M.; Arranz, J.; Román, S.; Rojas, S.; Montero, I.; López, M.; Cruz, J. Characterization of grape pomace and pyrenean oak pellets. Fuel processing technology 2011, 92, 278-283.
  2. Pereira, P.; Palma, C.; Ferreira-Pêgo, C.; Amaral, O.; Amaral, A.; Rijo, P.; Gregório, J.; Palma, L.; Nicolai, M. Grape pomace: A potential ingredient for the human diet. Foods 2020, 9, 1772.
  3. Pop, I.; Pascariu, S.M.; Simeanu, D.; Radu-Rusu, C.; Albu, A. Determination of the chemical composition of the grape pomace of different varieties of grapes. Scientific Papers-Animal Science Series: Lucraritiinifice-Seria Zootehnie 2015, 63, 76-80.
  4. Valiente, C.; Arrigoni, E.; Esteban, R.; Amado, R. Grape pomace as a potential food fiber. Journal of Food Science 1995, 60, 818-820.
  5. Mohamed Ahmed, I.A.; Özcan, M.M.; Al Juhaimi, F.; Babiker, E.F.E.; Ghafoor, K.; Banjanin, T.; Osman, M.A.; Gassem, M.A.; Alqah, H.A. Chemical composition, bioactive compounds, mineral contents, and fatty acid composition of pomace powder of different grape varieties. Journal of Food Processing and Preservation 2020, 44, e14539.
  6. Mortari, D.; Perondi, D.; Rossi, G.; Bonato, J.; Godinho, M.; Pereira, F. The influence of water-soluble inorganic matter on combustion of grape pomace and its chars produced by slow and fast pyrolysis. Fuel 2021, 284, 118880.
  7. Moço, A.; Costa, M.; Casaca, C. Ash deposit formation during the combustion of pulverized grape pomace in a drop tube furnace. Energy conversion and management 2018, 169, 383-389.
  8. Vassilev, S.V.; Baxter, D.; Vassileva, C.G. An overview of the behaviour of biomass during combustion: Part I. Phase-mineral transformations of organic and inorganic matter. Fuel 2013, 112, 391-449.
  9. Nikolov, A.; Kostov, V.; Petrova, N.; Tsvetanova, L.; Vassilev, S.V.; Titorenkova, R. Sunflower Shells Biomass Fly Ash as Alternative Alkali Activator for One-Part Cement Based on Ladle Slag. Ceramics 2025, 8, 79.
  10. Vassilev, S.V.; Vassileva, C.G. Water-soluble fractions of biomass and biomass ash and their significance for biofuel application. Energy & Fuels 2019, 33, 2763-2777.
  11. Oliveira, M.; Teixeira, B.M.; Toste, R.; Borges, A.D. Transforming wine by-products into energy: Evaluating grape pomace and distillation stillage for biomass pellet production. Applied Sciences 2024, 14, 7313.
  12. Kalembkiewicz, J.; Galas, D.; Sitarz-Palczak, E. The physicochemical properties and composition of biomass ash and evaluating directions of its applications. Polish Journal of Environmental Studies 2018, 27, 2593-2603.
  13. Machado, A.R.; Voss, G.B.; Machado, M.; Paiva, J.A.; Nunes, J.; Pintado, M. Chemical characterization of the cultivar ‘Vinhão’(Vitis vinifera L.) grape pomace towards its circular valorisation and its health benefits. Measurement: Food 2024, 15, 100175.
  14. Wang, J.; Ma, T.; Wei, M.; Lan, T.; Bao, S.; Zhao, Q.; Fang, Y.; Sun, X. Copper in grape and wine industry: Source, presence, impacts on production and human health, and removal methods. Comprehensive Reviews in Food Science and Food Safety 2023, 22, 1794-1816.
  15. Nikolov, A.; Kostov-Kytin, V.; Tarassov, M.; Tsvetanova, L.; Lazarova, H.; Tasheva, T. Products of carbonation of cement kiln dust. Review of the Bulgarian Geological Society 2024, 85, 163-166.
  16. Kandikonda, R.; Murugadoss, G.; Venkatesh, N.; Subbaraj, S.S.V.; Palani, D.; Thota, S.; Rajaboina, R.K.; Divi, H.; Dhayalan, M.; Phanumartwiwath, A. Redox-driven synthesis of stable copper nanoparticles via metal displacement and their application in organic dye degradation. Materials Advances 2025, 6, 9575-9589.
  17. Rehman, I.; Bonfield, W. Characterization of hydroxyapatite and carbonated apatite by photo acoustic FTIR spectroscopy. Journal of materials science: materials in Medicine 1997, 8, 1-4.
  18. Grunenwald, A.; Keyser, C.; Sautereau, A.-M.; Crubézy, E.; Ludes, B.; Drouet, C. Revisiting carbonate quantification in apatite (bio) minerals: a validated FTIR methodology. Journal of archaeological science 2014, 49, 134-141.
  19. Apfelbaum, F.; Diab, H.; Mayer, I.; Featherstone, J. An FTIR study of carbonate in synthetic apatites. Journal of inorganic biochemistry 1992, 45, 277-282.
  20. Stoch, A.; Jastrzębski, W.; Brożek, A.; Trybalska, B.; Cichocińska, M.; Szarawara, E. FTIR monitoring of the growth of the carbonate containing apatite layers from simulated and natural body fluids. Journal of Molecular Structure 1999, 511, 287-294.
  21. Baldassarre, F.; Altomare, A.; Mesto, E.; Lacalamita, M.; Dida, B.; Mele, A.; Bauer, E.M.; Puzone, M.; Tempesta, E.; Capelli, D. Structural characterization of low-Sr-doped hydroxyapatite obtained by solid-state synthesis. Crystals 2023, 13, 117.
  22. Penel, G.; Leroy, G.; Rey, C.; Bres, E. MicroRaman spectral study of the PO4 and CO3 vibrational modes in synthetic and biological apatites. Calcified tissue international 1998, 63, 475-481.
  23. Nikolov, A.; Dobreva, L.; Danova, S.; Miteva-Staleva, J.; Krumova, E.; Rashev, V.; Vilhelmova-Ilieva, N. Natural and modified zeolite clinoptilolite with antimicrobial properties: A review. Acta Microbiologica Bulgaricа 2023, 39, 147-161.

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