HKBU and TWGHs jointly develop food waste compost with biopesticide properties by adding Chinese medicine herbal residue as bulking agent
15 Dec 2014
The HKBU’s Sino-Forest Applied Research Centre for Pearl River Delta Environment (ARCPE) and the Tung Wah Group of Hospitals (TWGHs) have been collaborating since 2013 to improve the efficacy of community food waste composter performance through the use of Chinese medicinal herbal residue as bulking agent in the food waste composting process. The compost produced is effective in pest control due to the presence of natural bioactive compounds. The latest results showed that the compost enhanced plant growth by reducing fungal pathogens by more than 99% when it was applied to plants inoculated with pathogenic fungal populations. This is the first report in the world of a “biopesticide compost derived from Chinese medicinal herbal residue” being produced and is expected to have tremendous market potential.
According to the study, the optimised composting mix of 1:1:0.5 ratio (on dry weight basis) of Chinese medicinal herbal residue: food waste: saw dust effectively reduced the composting time from 8-9 weeks to 5 weeks. Moreover, the temperature of the composter could be maintained between 60 to 70°C throughout the composting period, meeting the new EU requirement on compost temperature which was proposed to ensure sufficient heat to kill the pathogens. At such high temperatures, the problem of fat, oil and grease could also be effectively alleviated. The quality of the final product also meets the requirement for “Organic Farming” set by the HKBU’s Hong Kong Organic Resource Centre.
In addition, the results showed that Chinese medicinal herbal residue helped boost the bulking condition of compost and its antipathogenic effects. Growth experiments using tomato and Chinese cabbage plants that received Chinese medicinal herbal residue derived compost demonstrated antipathogenic effects and inhibition of two fungal pathogens. About 22 bioactive compounds were found in the compost that contained herbal residues, and seven of these compounds belonging to the groups alkaloids, flavonoids and coumarins were present in significant quantities. These compounds killed bacteria and fungal pathogens. When the compost was applied to tomato and Chinese cabbage plants inoculated with Alternaria solani and Fusarium oxysporum, the pathogenic fungal population was reduced by more than 99% resulting in enhanced plant growth and protection against diseases. A 5% compost application enhanced the biomass by 3.16 and 1.28-fold for tomato plants, and 2.42 and 2.21-fold for Chinese cabbage plants when compared with the control and regular food waste compost, respectively, demonstrating the ability of this product in suppressing fungal pathogens.
Professor Jonathan Wong, Director of ARCPE and the project-in-charge of this study, said that this is the first report in the world of producing compost with biopesticide properties by incorporating Chinese medicinal herbal residue into food waste compost. He said that the new compost could be a potential “organic fertiliser” for organic farming where the use of synthetic fertilisers is prohibited. The recycling of organic resources including food waste and Chinese herbal residue through composting is contributive to the exigent food waste problem in Hong Kong. He believed that the application potential of the biopesticide compost is important in crop production as it reduces the reliance on artificial pesticides and fertilisers, and the compost produced has strong market potential locally and internationally.