Abstract:
The thesis aims to study fed-batch composting in a 5.L vessel which was supplied with air through manual mixing. Fresh food waste was fed daily at a constant rate. A screening type and size of bulking agents for composting was done through an investigation of their followingproperties; density, particle space ratio, water retention ratio, water drainage resistance, moisture content, pH influence, ash content, and C/N ratio. The result indicates that 60 mesh sawdust, 40mesh bagasses and 40 mesh cassava pulps show good properties among all. With 60 mesh sawdust and 40 mesh bagasses, it resulted in higher constant value representing organic carbon decomposition, of 0.0011 and 0.0005 per day compared with the rate of 0.0004 per day whenusing cassava pulps as a bulking agent. No odor was observed if the composting process was carried out under aerobic condition.Besides the type and properties of bulking agents, the seedling, initial C/N ratio, and feed rate of food waste also affected the physical, chemical and microbiological changes during the composting process directly. Using sawdust as a bulking agent, 3 types of seeding such as PD.1, bionic, and F-60 could help enhancing the constant value for organic carbon decomposition from 0.0007 to 0.0010 per day. With the ratio between food waste and bulking agent of O.5:l.0 (kg:kg), the initial ratio of 37 and the daily feed rate of food waste at 0.5 per day, the highest constant value representing organic carbon decomposition at 0.0010 per day was achieved. With the 12.5 kg of food waste loading, the composting process lasted about 26 days whereas the process was prolonged when employing a lower waste feed rate. In addition, changes in characteristics of bulking agents started slightly longer than one month. This was shown by a noticeable odor caused by a transformation of aerobic to anaerobic condition after a reduction in ventilation within the composting pile. Therefore, it is important to change the bulking agent once a month. The study also shows that organic carbon decomposition during fedbatch composting follows a first order kinetic model.