Beneficial Re-Use of Spent Refinery Catalyst as P Fertilizer for Dryland Winter Wheat

Abstract

Approximately 7 Gg of high P content spent refinery catalyst (SRC) are produced as a by-product of the petroleum refining industry each year in the U.S. This spent refinery catalyst is classified as a hazardous waste due to its low pH, and is currently disposed of in hazardous waste storage facilities. The potential exists for beneficial re-use of SRC as P fertilizer for crops. This study was conducted to determine the availability and uptake of P and metals from SRC to dryland winter wheat in eastern Colorado. A field study was conducted for two years at five sites with a range of soil properties. Treatments included 6 rates of SRC (0, 10, 20, 40, 80, and 160 g/m2), and equivalent rates of a commercial source of P (triple superphosphate (TSP)) based on P content. Grain, straw, and boot stage plant materials were evaluated for yield and elemental uptake. Surface soils at grain harvest were evaluated for P availability, pH, and metal availability. Yield and P uptake data showed that SRC equaled TSP in providing P to wheat. The SRC significantly lowered surface soil pH, but in general no differences existed between SRC and TSP with regard to concentration of metals found in plant parts or in surface soils at grain harvest. Based on the parameters that were evaluated in these studies, there appears to be no adverse effect of using SRC as a P source for dryland winter wheat.