Graduate Studies

 

First Advisor

Amy Millmier Schmidt

Degree Name

Doctor of Philosophy (Ph.D.)

Committee Members

Aaron Daigh, Benny Mote, Caro Cordoba

Department

Agricultural and Biological Systems Engineering

Date of this Version

8-2025

Document Type

Dissertation

Citation

A dissertation presented to the Graduate College of the University of Nebraska in partial fulfillment of requirements for the degree of Doctor of Philosophy

Major: Biological Engineering

Under the supervision of Professor Amy Millmier Schmidt

Lincoln, Nebraska, August 2025

Comments

Copyright 2025, Gustavo Castro Garcia. Used by permission

Abstract

This dissertation evaluates the performance of three on-farm swine carcass disposal methods: whole carcass composting (WCC), ground carcass composting (GCC), and shallow burial with carbon (SBC), focusing on biosecurity factors and groundwater contamination risks. Foreign animal diseases (FADs), such as African swine fever and classical swine fever, pose severe economic and animal well-being risks if introduced to the United States. With confirmation of an FAD, swine movement will be halted, creating an urgent need for practical, biosecure, and environmentally responsible on-farm disposal strategies for swine carcasses. Nebraska, as a leading swine-producing state, exemplifies the vulnerability of high-density livestock regions to such disease outbreaks.

This project investigated performance of WCC, GCC, and SBC during a yearlong field study, transport characteristics through soils of leachate produced by each disposal method, and modeling of nitrogen transport from WCC and SBC methods using HYDRUS-1D to assess groundwater contamination risks. SBC emerged as a preferred disposal method, demonstrating achievement of time-temperature goals for pathogen destruction and significantly less leachate production compared to WCC and GCC. The model effectively captured vertical solute movement and decay kinetics, supporting the model’s utility for screening-level assessments, while also suggesting the need for enhanced reactive transport modeling in future applications.

Advisor: Amy Millmier Schmidt

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