Date of Award:


Document Type:


Degree Name:

Doctor of Philosophy (PhD)


Civil and Environmental Engineering

Committee Chair(s)

Michael J. McFarland


Michael J. McFarland


Gary P. Merkley


Randall D. Wiedmeier


Gilberto E. Urroz


William J. Doucette


The land application of biosolids to provide nutrients and organic matter is widely practiced in agricultural applications. However, the potential benefit of applying biosolids to disturbed rangelands has not been adequately evaluated. Thus the main goal of the current study was to evaluate the potential economic and environmental benefits of applying biosolids to disturbed rangeland with the main focus on evaluating the impact on forage quality and quantity as a function of biosolids type and application rate. Three types of biosolids (aerobically, anaerobically, and lime stabilized biosolids) were surface applied with no subsequent tilling at various loading rates (1, 5, 10, and 20 times nitrogen plant requirement) in Skull Valley, Utah. It was demonstrated that forage quality (crude protein and in vitro digestibility) and quantity (biomass) can be improved by biosolids land application. Also, the analyses of the soil and forage for 16 specific metals indicated no measurable accumulation except for a statistical increase of sodium compared with the control. No negative impact on soil moisture infiltration (e.g., drainage) properties were seen. The economic analysis of biosolids land application on disturbed rangeland associated with improvements in forage quality indicated that use of biosolids for land restoration would be profitable. The highest potential financial return was observed when anaerobically digested biosolids were land applied at 20 times the agronomic rate. Finally, despite the numerous benefits associated with biosolids land application, there remain a number of human health and environmental concerns regarding its use on publicly accessible lands that should be addressed in future studies. These concerns are primarily associated with the accumulation of heavy metals and recalcitrant organics (e.g. polychlorinated biphenyls, dioxins, brominated biphenyls, and pharmaceuticals and personal care products) that may be associated with the biosolids.