Properties of Humic Substances in Composts Comprised of Different Organic Source Material

Marge Lanno (), Maris Klavins, Oskars Purmalis, Merrit Shanskiy, Anu Kisand and Mait Kriipsalu
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Marge Lanno: Institute of Agricultural and Environmental Sciences, Estonian University of Life Sciences, 51006 Tartu, Estonia
Maris Klavins: Department of Environmental Sciences, University of Latvia, 1586 Riga, Latvia
Oskars Purmalis: Department of Environmental Sciences, University of Latvia, 1586 Riga, Latvia
Merrit Shanskiy: Institute of Agricultural and Environmental Sciences, Estonian University of Life Sciences, 51006 Tartu, Estonia
Anu Kisand: Institute of Agricultural and Environmental Sciences, Estonian University of Life Sciences, 51006 Tartu, Estonia
Mait Kriipsalu: Institute of Forestry and Rural Engineering, Estonian University of Life Sciences, 51006 Tartu, Estonia

Agriculture, 2022, vol. 12, issue 11, 1-14

Abstract: Reusing organic waste as fertilizer is one method to reduce the use of mineral fertilizers and minimize waste disposal in landfills. Regulations have been enacted for the processing of organic waste and for recycling end products, but the humic content of organic fertilizers has been neglected. We studied seven composts with different organic input materials and technologies. Humic substances (HSs) were detected in all composts. The total organic carbon in the HSs constituted 8.7 ± 0.1% (SD)–27.0 ± 0.2% of the compost dry matter. Spectral differences between the studied samples in FTIR spectroscopy could be observed at 1700–1000 cm −1 , indicating differences in compost precursor material. The EEM peak, associated with humic acids (HAs), was high in composts containing animal by-products (e.g., fish waste, horse manure, and kitchen biowaste). Kitchen biowaste, also when processed by Hermetia illucens larvae and vermicompost, exhibited slower organic material transformation with low humic acid/fulvic acid ratios (<1.60). The results show the importance of source material origin and amendments, which influence the composting process and final products. Our study emphasizes the role of humic substances in the comprehensive evaluation of composts. To maximize the added value of composts, marketing strategies should consider determining the share of humic substances besides the content of organic matter and nutrients.

Keywords: humic acid; fulvic acid; fish waste; horse manure; sewage sludge; Hermetia illucens frass; green waste; kitchen biowaste (search for similar items in EconPapers)
JEL-codes: Q1 Q10 Q11 Q12 Q13 Q14 Q15 Q16 Q17 Q18 (search for similar items in EconPapers)
Date: 2022
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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