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Title

DEGRADATION RATE MODEL TO ESTIMATE SOIL CARBON SEQUESTRATION

Creator

Zhai, Wenjuan

Date

2016, 2016-05

Description

Concern over climate change as a consequence of carbon dioxide (CO2) emissions from human activities has resulted in efforts to better...
Show moreConcern over climate change as a consequence of carbon dioxide (CO2) emissions from human activities has resulted in efforts to better understand potential mitigation measures such as carbon sequestration in soils. Processes shaping natural carbon sequestration may be used to remove excess CO2 from combustion and other anthropogenic sources of carbon, and, alleviate concerns over climate change. Land application of biosolids is a process that increases the amount of soil carbon sequestration and may produce carbon credits in accordance with the definition of UN Climate Change Convention. A dynamic degradation rate model (DRM) has been developed based on a mass balance and first order kinetics to describe the soil organic carbon (SOC) decomposition process, which provides insights on carbon sequestration due to microbial biomass, SOC, CO2 emission rates, residence time of sequestered carbon, and biomass to biosolids ratios. A curve fitting approach was used to produce a best fit average degradation rate for biosolids degradation and microbial biomass yield. This study employed a 34-year biosolids application database from the literature to determine the amount of carbon sequestered in 41 strip-mined Illinois fields. The DRM application identifies two SOC phases in soil. Soil organic carbon gain in phase one (first 10 yrs) is primarily due to biosolids C application remaining and accumulation while in phase two, SOC gain is due to biomass or C sequestration. Carbon sequestration changes with time relate to variations in biosolids application amounts (10 and 18 Mg ha-1 yr-1), different degradation rate constants (0.04yr-1 to 0.16yr-1), and biomass yields (35 to 40%). Additionally, comparison between model simulation results and laboratory resultsdetermine the amount of carbon sequestered in 41 strip-mined Illinois fields. The DRM application identifies two SOC phases in soil. Soil organic carbon gain in phase one (first 10 yrs) is primarily due to biosolids C application remaining and accumulation while in phase two, SOC gain is due to biomass or C sequestration. Carbon sequestration changes with time relate to variations in biosolids application amounts (10 and 18 Mg ha-1 yr-1), different degradation rate constants (0.04yr-1 to 0.16yr-1), and biomass yields (35 to 40%). Additionally, comparison between model simulation results and laboratory resultsdetermine the amount of carbon sequestered in 41 strip-mined Illinois fields. The DRM application identifies two SOC phases in soil. Soil organic carbon gain in phase one (first 10 yrs) is primarily due to biosolids C application remaining and accumulation while in phase two, SOC gain is due to biomass or C sequestration. Carbon sequestration changes with time relate to variations in biosolids application amounts (10 and 18 Mg ha-1 yr-1), different degradation rate constants (0.04yr-1 to 0.16yr-1), and biomass yields (35 to 40%). Additionally, comparison between model simulation results and laboratory resultsdetermine the amount of carbon sequestered in 41 strip-mined Illinois fields. The DRM application identifies two SOC phases in soil. Soil organic carbon gain in phase one (first 10 yrs) is primarily due to biosolids C application remaining and accumulation while in phase two, SOC gain is due to biomass or C sequestration. Carbon sequestration changes with time relate to variations in biosolids application amounts (10 and 18 Mg ha-1 yr-1), different degradation rate constants (0.04yr-1 to 0.16yr-1), and biomass yields (35 to 40%). Additionally, comparison between model simulation results and laboratory results provided by a yearlong study indicates that higher temperatures and moisture content and finer soils are related to larger degradation rates. To summarize, this study has the following contributions: (1) developed a degradation rate model which simulates the biosolids degradation process in soil and identifies two SOC phases in soil, and quantifies the biosolids degradation rate constant, biomass yield, and the C sequestered amount for multiple and long term soil application; (2) assessed the effect of changes in the amount of biosolids applied, soil type, and weather conditions on the C degradation rate by comparing model results to laboratory data; and (3) provides an easy quantitative method for predicting C sequestration from biosolids added to soil.
Ph.D. in Environmental Engineering, May 2016
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