Determination of Liming Potential of Industrial Byproducts.

Acid soils in the southeastern Coastal Plain require liming materials to reduce acidity, but few of the high-quality limestone deposits in Alabama are used for agricultural purposes.  It has been suggested that the annual need of ground limestone in Alabama for crops and forages is at least twice of what is currently used.  Some industrial byproducts (e.g., paper mill sludge and stainless steel slag) are potential alternative liming materials, but their liming potential needs to be evaluated.  The objective of this study is to evaluate the liming potential of nine industrial byproducts: K-lime, two types of stainless steel slag, three types of paper mill sludge, paper mill lime mud, paper mill ash, and blast furnace slag.  For each product, calcium carbonate equivalent, particle size, relative neutralizing value, and total elements were analyzed.  Results indicate a wide range in properties of byproducts evaluated.  Only K-lime, paper mill lime mud, and paper mill ash met the particle size requirement for agricultural lime in Alabama.  Calcium carbonate equivalentranged from 13% in paper mill primary sludge to 102% in paper mill lime mud, which was related to the effective neutralizing value of these byproducts, which spanned from <1% in paper mill primary sludge to 100% in paper mill lime mud.  The stainless steel slag was high in Cr (1087 mg kg^-1), which is close to the maximum limit (1200 mg kg^-1) enforced by USEPA. Overall, results from this study indicate that paper mill ash and lime mud may be suitable alternative liming materials, whereas paper mill primary sludge and stainless steel slag have considerable limitations to use.  Particle size of blast furnace slag needs to be sufficiently reduced before commercial use.