Extraction Optimization, Multi-Dimensional Characterization, and Agricultural Application of Humic Acid from...

Area of Science:

• Agricultural Science
• Biotechnology
• Soil Science

Background:

• Agricultural straw is a major lignocellulosic byproduct requiring valorization.
• Insect larvae, specifically *Protaetia brevitarsis*, can convert straw into insect protein and humic acid-rich frass.
• Developing efficient humic acid (HA) extraction from insect frass is crucial for its application.

Purpose of the Study:

• To investigate parameters influencing HA extraction efficiency from *P. brevitarsis* frass.
• To optimize the HA extraction process for high-value fertilizer production.
• To characterize the extracted HA and evaluate its impact on plant growth and quality.

Main Methods:

• Optimization of multiple parameters for HA extraction.
• Characterization of the extract using elemental analysis and 13C NMR spectroscopy.
• Pot experiments with cherry radish to assess plant growth and quality effects.

Main Results:

• Optimized extraction achieved a total organic carbon (TOC) concentration of 46.8 g/L, meeting Chinese fertilizer standards.
• Elemental analysis confirmed the extract's richness in trace elements and compliance with heavy metal regulations.
• 13C NMR indicated enrichment in aliphatic and methoxyl carbons; pot experiments showed significant promotion of plant growth and improved crop quality.

Conclusions:

• The optimized HA extract from insect frass is a viable, high-quality fertilizer.
• This process supports circular agriculture by valorizing agricultural waste.
• The findings highlight the academic and practical potential of insect frass-derived humic acid for sustainable agriculture.