Pressure Drop through Raw Food Waste Compost containing Synthetic Bulking Agents

Abstract

Abstract The pressure drop of air forced through a column of raw vegetable waste compost was measured for six different synthetic bulking agents and compared to pine bark as a reference. The volume of each bulking agent used per mass of compost material, referred to as the bulking agent ratio, was used to compare these bulking agents. Results indicate that synthetic bulking agents reduce the pressure drop significantly more than pine bark for any given bulking agent ratio and air flow. The pressure drop measurements were regressed to three pressure drop-flow models, and these models were similarly successful in predicting the observed pressure drop behaviour. To quantify the impact of bulking agent ratio on pressure drop, a two-parameter empirical relationship was proposed between the bulking agent ratio and the linear coefficient of Ergun's model (model 3) or the coefficient in Shedd's model (model 1) forced to an exponent of 1·0 or 1·1. One of the parameters in this proposed model is the bulking agent ratio necessary to reduce by 50% the viscous energy losses of air flow through the compost column. Using the empirical model to compare this parameter among bulking agents used, the synthetic bulking agents were demonstrated to be approximately 3–10 times more effective than pine bark. The utility of this model to aid the optimization of the bulking agent ratio is also discussed.