Re ECF Project: 2011-33

Project Title: Composting of Food Waste with Chinese Medicinal Herb Residues as a Bulk Agent to Produce a High-end Organic Fertilizer

Applicant: Mr. Edwin CHAN, Property Secretary of Tung Wah Group of Hospitals

Total Approved Grant: $1,086,480

Duration: 1/11/2012 to 31/10/2014

Project Status/Remarks: Completed

The project aims to demonstrate the feasibility of using Chinese medicinal herb residues collected from local Chinese medicine clinics as bulking agents for food waste composting so as to reduce the operation cost of composting as well as to establish a carbon neutral and resource conservation technology for managing both wastes.

Summary of the Findings/Outcomes:
Bench-scale composting experiments revealed that a mixing ratio of food waste (FW)+saw dust (SD): Chinese medicinal herbal residues (CMHR) at 1:1 was optimum reaching 67% organic degradation. The lignin content of the CMHR provided the nucleus for the formation of humic substances that accelerating the composting maturity. Extracts of both CMHR and CMHR-derived exhibited 3-times lower MIC50 values (13-16 ppm) than the CMHR extracts against fungal pathogens Alternaria solani and Fusarium oxysporum. Besides, the bacteria and fungi exist in the CMHR compost exhibited more antagonistic effects on the pathogens indicating both direct and indirect antipathogenic effects. About 22 compounds, mainly belonging to alkaloids, flavonoids and coumarins, identified were derived from the CMHR and significant concentrations and activities exist after the composting process. Compost application to tomato and pak choi plants increased the biomass by 2-3 folds than the control/food waste. About 40-70% of the bioactive compounds present were degraded in the soil during the plant growth yet the pathogenic population was reduced by >99% indicating multiple advantages. Optimization of a pilot-scale in-vessel composting revealed that a mixing ratio of 1:1:0.5 (CMHR:FW:SD) with horse manure compost seed, 2% lime, and oil degrading bacterial inoculation provided a good composting performance; and mature compost could be obtained from 6 weeks. A public seminar was held and 6 papers were published in journals/conferences.