Re ECF Project: 2010-34

Project Title: De-centralized food waste composting at community level: Challenges, optimization and demonstration

Applicant: Prof. Jonathan W.C.WONG of Hong Kong Baptist University

Total Approved Grant: $1,925,520

Duration: 1/10/ 2011 to 30/9/2014

Project Status/Remarks: Completed

The project aims to demonstrate the feasibility of establishing decentralized small scale on-site composting facilities in various residential and commercial premises for diverting food waste from landfilling. The objectives of this demonstration project are to:

  • develop an ideal composting mix formulation that is suitable for small-scale commercial composters;
  • alleviate the acidity and odour problems through suitable/ sustainable bulking agents, inorganic additives such as lime, coal fly ash and zeolite;
  • monitor the selected food waste composting facilities to identify the problems, develop solutions and streamline the process;
  • attract the compost users through demonstrating the product quality on plant growth and yield to bridge the gap between the production and consumption with the purpose to encourage the community and industries to setup composting facilities; and
  • develop a composting guideline from the results and experiences obtained from this project.

Summary of the Findings/Outcomes:
Results revealed that (1) an initial composting mix of food waste and horse manure pre-mature composts mixed with sawdust (at 2:6:1) provided a good starting culture before loading the food wastes; (2) addition of 10% zeolite controlled the acidity and odour and reduced nitrogen loss; and (3) microbes effectively degrading the fat and oil are essential for food waste composting. Community composters clearly failed to provide the manufacturer-projected performance when applying food wastes as the sole substrate due to the inadequate retention of the mass. Oil content of the food waste created lumpy and sticky composting mass that hindered the composting completely. The composters at the organizations monitored also reflected the same operational problems and quality compost products were obtained when the optimum operational and mixing conditions were applied. In addition to the above solutions, reducing the loading rate to increase retention time and providing a curing period is essential to obtain mature compost.

Compost application at 5% increased the cabbage and tomato plants as well as greenroof plants by >5 fold but higher concentrations affected the biomass negatively. Supplementation of peanut cake at 50 kg/ha as additional nitrogen source to the 5% compost enhanced the biomass by ~2-fold compared with compost, however, higher concentrations affected the growth.

A composting guideline was developed for each site at the early phase to guide the organization facility operators. In addition, those problems and possible solutions were compiled with the composting manual to develop into a final general composting guideline. A training and awareness program was conducted at 3 organizations as well as the Hong Kong Baptist University canteen staff and student. Publicity and promotion materials were developed and distributed to the fresh graduates also so as to plant the recycling concept and responsibility