Optimizing sugarbeet molasses distillery slops to olive mill husks ratio and incubation period for composting

Abstract

This paper analyzes the influence of operating conditions, such as mixing ratio of the waste ingredients and extension of the stabilization time, on the composting of sugarbeet molasses distillery slops (DS) and olive mill husks (OMH). The addition of 0–40% sugarbeet molasses DS to the starting mixtures and the treatment duration (40 d) were tested at the bench to optimize the process dynamics using the in-vessel composting method. Changes of compost stabilization conditions (organic matter, nitrogen losses, germination index) were also related to the characteristics of the different end products obtained. A second-order polynomial equation based on two independent process variables was developed to model the composting of sugarbeet molasses DS – OMH mixtures. Differences between experimental values and data derived by the application of the model never exceeded 10%. The best results in terms of biodegradation rate (i.e., degree of stabilization), maturity, and limitation of Kjeldahl-N losses were observed with process times of 30–40 d and the addition of 0–10% sugarbeet molasses DS to OMH. Key words: biodegradability, compost, sugarbeet molasses distillery slops, olive mill husks.