Some implications of the recycling of sugar industry by-products

This paper presents results of the total concentrations of a range of nutrients and heavy metals (arsenic, cadmium, copper, chromium, mercury, lead, nickel and zinc) in sugar mill by~products (mill mud, ash material and mixtures of mud/ash) from all sugar regions in Queensland and New South Wales. Similar concentrations of nutrients to earlier reported data were found indicating that these concentrations are reasonably consistent. Mean cadmium, mercury and zinc concentrations were higher in filter mud compared to ash material, while chromium and nickel were higher in ash. Regional differences were variable, probably a reflection on geology from which soils derived, and fertiliser management strategies. Mean cadmium and zinc concentrations in filter mud were five and three times respectively those in contemporary cane soils. Inputs of heavy metals from sugar mill by-products are relatively small. In the case of cadmium, they are of similar magnitude to inputs from phosphatic fertilisers applied at normal agronomic rates. As such, these inputs need to be considered when assessing the effects of management practices on heavy metal budgets for canelands.