Bioconversion of wastes from olive oil industries by vermicomposting process using the epigeic earthworm Eisenia andrei

Abstract

The present work evaluates the possible bioconversion of wet olive cake by low-cost biostabilization (vermicomposting process). Wet olive cake fresh (WOC), precomposted (WOCP), or mixed with biosolids (WOCB), were vermicomposted for 6 months to obtain organic amendments for agricultural and remediation purposes. The results showed initial differences depending on previous treatment. WOCP was initially more stable, presented a low C:N ratio, and showed more dehydrogenase and urease activity. By contrast, there was no dehydrogenase activity initially in WOC and WOCB, due to the presence of some different types of polyphenols. Finally, the end product showed relatively higher amounts of total nitrogen and humic acid and met the standard of quality for composts and vermicomposts for use both in conventional and organic agriculture and soil-restoration programs.

Keywords:

• Olive oil industry
• wet olive cake
• vermicomposting process
• by-products
• biochemical parameters
• standard quality

Acknowledgments

This study was financed by Junta de Andalusia, Spain (Project CAO01-007). Melgar thanks the European Social Fund for funding her research. We would also like to thank David Nesbitt for assisting in the translation of the original manuscript into English.

Notes

*Indicates a significant difference (P < 0.05) between substrates (I) and final products (F).