Aeration improvement in fed batch composting of vegetable and fruit wastes

Vegetable and fruit wastes amended with sawdust and urea were composted in a laboratory scale reactor controlling a waste feeding rate of 21 g L(-1) day under proper conditions of composting. Effects of aeration, agitation, and initial waste-to-sawdust ratio on enhancing organic matter degradation and process performance in fed batch composting were investigated. During the feeding stage, rapid increase in moisture content and lowest removal of dry mass (0.28-0-30 g g(-1) day(-1)) were observed at all aeration rates without agitation at a waste-to-sawdust ratio of 1:1.5. As the amount of sawdust was doubled, the water released was not only absorbed by waste matrix efficiently, resulted in the highest dry mass removal and total amount of new waste addition, but also demonstrated the substantial N loss (54-71%). The results revealed that the initial waste-to-sawdust ratio and agitation mode indeed influenced the performance of the fed batch composting (feeding stage) as indicated by a higher percentage of dry mass removal (34-59%) and larger free air space in compost matrix were determined. Adoption of a large amount of sawdust and agitation mode is recommended for maintaining stable degradation and enhancing fed batch composting under continuous aeration at a rate of 10.62-21.24 L m(-3) min(-1). (C) 2008 American Institute of Chemical Engineers Environ Prog.