Animal waste-enhanced degradation of hydrocarbon-contaminated soil

Land previously used for petroleum production is being converted to commercial, industrial, or residential uses and requires remediation to remove petroleum hydrocarbons (HC). Concurrently, large quantities of animal wastes are produced annually, creating waste-handling and disposal problems. A laboratory study was conducted to determine whether amending contaminated soil with animal manure and inorganic fertilizer affected the degradation rate and amount of HC in the soil. HC-impacted soil was prepared by mixing a diesel fuel: motor oil solution (1:1 v/v) with a noncontaminated loamy sand, with a target concentration of 5000 mg HC per kg soil. Treatments included ammonium sulfate fertilizer, composted steer manure at 5, 10, and 20% on a dry weight basis, and a mixture of fertilizer and steer manure, with three replications for each treatment. Five-gram aliquot soil samples were extracted with hexane. The extracts were analyzed using a gas chromatograph with a flame ionization detector. Over a period of 41 days, control treatment HC concentrations were reduced by 32%. Hydrocarbon concentrations in (NH4)2SO4 fertilizer-amended soil were decreased by nearly 54% during the same time. In contrast, HC degradation was much faster and more complete in manure-amended soils. Up to 81% of the HC in the 20% manure-treated soil were removed by day 41.