Influence of different airflows and the presence of bulking agent on biodrying of gardening wastes in reactors

Biodrying consists on evaporating the water from a biodegradable substrate by the heat generated in the aerobic fermentation. To achieve a biomass with low humidity from garden waste of a university campus, this biological drying process has been applied. On the other hand, the influence of bulking agent (BA) for improving the process must be analyzed. In this work the effect of biodrying process on properties of lawn mowing and garden waste used as substrate was studied. Biodrying was performed in 10 reactors with known aeration rate from 0.88 to 6.42 L/min • kg d/w. Five reactors had 15 % of bulking agent (BA) and five reactors had only grass. The parameters influencing the process were: aeration, temperature and initial moisture of biowaste. The results obtained indicate that the essays with BA presented the best reduction of moisture; after 20 days the water content of waste was reduced between 50 and 69 %, allowing the production of biodried waste with a low heat value (LHV) between 11063-13709 kJ kg-1. After the experiences it is also found that the BA improves moisture reduction, drops NH3 production and permits good performance of thermophilic phase. However, the increase in aeration rate was not linearly proportional to the weight loss.