Economic implications of alternative mill mud management options in the Australian sugar industry

Sugar mills produce a range of byproducts during the process of extracting sugar from cane. Mill mud is one of the byproducts produced in significant volume. The practice of spreading mill mud onto cane fields close by the mill has been the primary means of disposing of mill mud for many years. The continued application of mill mud at high rates, without appropriate recognition of its nutrient content, the soil condition, crop nutrient requirements, slope of the land, or proximity of application sites to environmentally sensitive areas has raised a number of concerns in recent years, including overfertilization, heavy‐metal contamination, leaching, and offsite impacts from drainage to waterways. This study develops a regional mathematical programming model to determine optimal rates of mill mud application for various soil types and distances from the mill in the Mackay region in central Queensland, Australia. The optimal application rate of mill mud varies according to soil type and by distance from the mill. Lower rates of mill mud application are economically desirable at greater distances from the mill. However, when the cost of mill mud application is shared between growers and the mill operator, the optimal application rates are reduced at some locations while increasing at others.