Degree Name

Master of Science (MS)

Semester of Degree Completion


Thesis Director

Karen F. Gaines


Soil application of solid residues from thermal conversion of biomass (i.e. combustion and pyrolysis) has become a topic of interest in recent years. However, there exists a gap in the literature with regard to soil application of gasification residues and their effects on soil health and soil macroorganisms. This study investigates the effects of three different ashes (hardwood oak/hickory, hardwood willow, corn stover), collected from industrial biomass gasification reactors (University of Minnesota Morris, Eastern Illinois University), as a soil amendment on the composting worm Eisenia fetida. Additionally, ash samples were analyzed for total polycyclic aromatic hydrocarbons (PAHs) and potentially toxic elements, such as heavy metals. E. fetida were exposed for 28 days at various application rates (0 t ha-1, 5 t ha-1, 10 t ha-1, 25 t ha-1, and 100 t ha-1). After three exposure trials, it was determined that none of the three ash samples had an effect on survival of E. fetida except at concentrations in which soil pH reached 9.8 or higher, where 100% mortality was observed. All ash samples were found to have moderately to extremely high pH. Weight loss observed in all E. fetida samples was attributed to starvation and there were no relationships found between weight loss and any of the three ash samples or their application rates. PAHs were undetectable using GC-FID and GC-MS. Elemental analysis using ICP-MS determined that all potentially toxic elements were well below U.S. regulatory limits. In conclusion, these three ash samples were determined to be safe for use as soil amendments at application rates that maintain soil pH below a threshold of 9.7.

Included in

Soil Science Commons