Reuse of composted food waste from rural China as vermicomposting substrate: effects on earthworms, associated microorganisms, and economic benefits

ABSTRACT

Aerobic composting of food waste (FW) from rural China using a composting device results in a substantial financial burden on the government. This study aimed to assess the feasibility of mitigating this cost using vermicomposting of composted FW. The specific aims were to elucidate the effects of composted FW on earthworm growth and reproduction, reveal the changes in the physical and chemical properties of earthworm casts during vermicomposting, identify the microbial community structure associated with vermicomposting, and perform a financial analysis based on the yield of earthworms and earthworm casts. Mixing composted FW and mature cow dung in an equal ratio achieved the highest earthworm reproduction rate, where 100 adult earthworms produced 567 juvenile earthworms and 252 cocoons in 40 d. Earthworms reduce salt content of vermicomposting substrates by assimilating Na⁺ and promoting humification by transforming humin into humic and fulvic acid, thus producing earthworm casts with a high generation index > 80%. When composted FW was added to a vermicomposting substrate, a distinctive microbial community structure with alkaliphilic, halophilic, and lignocellulolytic microorganisms dominated the microflora. The dominant bacterial species was Saccharopolyspora rectivirgula, and the dominant fungal species changed from Kernia nitida to Coprinopsis scobicola. Furthermore, microbial genes for refractory organic matter and fat degradation were observed in Vibrio cholerae, Kernia nitida, and Coprinopsis scobicola. Financial analysis showed that vermicomposting has the potential to reduce the cost associated with FW disposal from $ 57 to $ 18/t.

GRAPHICAL ABSTRACT

KEYWORDS:

• Food waste
• vermicomposting
• microbial community structure
• gene function
• financial analysis

Acknowledgments

The authors thank Personal Biotechnology Co. Ltd., Shanghai, China (http://www.personalbio.cn/) for their assistance in microbial data analysis.

Data availability statement

The authors confirm that the data supporting the findings of this study are available within the article [and/or] its supplementary materials.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the [Research and Development Fund Project of Zhejiang A&F University] under Grant [number 2021LFR004] and [number 2022LFR021], the [Key Research and Development Plan of Zhejiang Province] under Grant [number 2020C02009] and [number 2021C03190], the [Special Project of Science and Technology Cooperation Plan ‘San Nong Jiu Fang’ of Zhejiang Province] under Grant [number 2022SNJF077], and the [Overseas Expertise Introduction Project for Discipline Innovation (111 Project)] under Grant [number D18008].