Date of Award

2012

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Environmental Science

First Advisor

Ahmedna, Mohamed

Abstract

Soil carbon sequestration has emerged as an innovative approach that may offer a low-risk and an efficient way to mitigate climate change and replenish soil fertility. In various agricultural production systems, byproducts are produced in significant amounts from crop residues such as pecan shells (PC), peanut shells (PS), and cotton gin (CG) that can be used to produce biochar and applied to agricultural soil first to sequester C and second to enhance plant growth by supplying and retaining nutrients, improving soil physical and biological properties. The objectives of this study were to (a) produce biochars from different byproducts (PC, PS, CG, and switchgrass) at different pyrolysis temperatures and times, and determine their physico-chemical properties, (b) apply the biochars to the coastal plains and Piedmont regions soils and determine their effects on the soil characteristics (bulk density, water holding capacity, aggregate stability, pH, CEC, and macro and micronutrients content) and leaching of nutrients, (c) perform a greenhouse testing of the best biochars and compare treated and untreated soils in terms of plant growth using lettuce as a crop, and (d) determine the effect of the best biochars on the GHGs emission (CO2 and NH4) during a 10 weeks soil incubation study. Higher pyrolysis temperatures resulted in lower biochar recovery, greater surface areas, higher pH, minimal total surface charge, and higher ash contents. Soil properties were significantly improved after biochar addition. No significant increase in the crop biomass, while, a net decrease in GHGs was observed following the biochar addition to soil. Biochars produced from different feedstocks and under different pyrolysis conditions influenced soil physical and chemical properties in different ways; consequently these may be designed to selectively improve soil chemical and physical properties by altering feedstocks and pyrolysis conditions. The addition of biochar to soil did not significantly improve the crop growth, but significantly reduced the emission of GHGs from soil.

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