|Novak, Jeffrey - Jeff|
|Watts, Donald - Don|
Submitted to: Annals of Environmental Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/17/2009
Publication Date: 11/19/2009
Citation: Novak, J.M., Lima, I., Xing, B., Gaskin, J.W., Steiner, C., Das, K.C., Ahmedna, M., Rehrah, D., Watts, D.W., Busscher, W.J., Schomberg, H.H. 2009. Characterization of designer biochar produced at different temperatures and their effects on a loamy sand. Annals of Environmental Science. 3:195-206. Interpretive Summary: Sandy soils used for farming in the southeastern Coastal Plain region have low fertility, water retention, and organic carbon contents. These characteristics cause the sandy soils to be prone to drought during times of low rainfall and to nutrient leaching during periods of high rainfall. The lack of nutrients and water results in crop stress and reduced yields. It has been proposed that adding biochar, a byproduct of energy production from agricultural residues, can improve these poor soil characteristics. Differences in pyrolytic processes (biochar production) and type of agricultural residues affect biochar quality. As a result, biochars can be designed to have certain qualities that can react differently with soil and improve particular deficiencies. We made biochars from four different residues (switchgrass, pecan shells, peanut hulls and poultry manure) at two different pyrolysis temperatures and mixed them into a sandy soil from South Carolina. Biochars made at higher temperatures had higher pHs; biochars made at lower temperatures had more sites for holding nutrient for plant growth. After a few weeks of incubation, amended soils were leached with water and the amount of water retained was determined. Some biochars increased the soils water retention and pH while other biochars increased soils sodium and phosphorus content. Our results demonstrate that biochar additions can improve soil fertility and that biochar quality is an important characteristic. To improve the value of their product, biochar producers might consider adjusting their production process to generate designed biochars aimed at remedying specific soil problems.
Technical Abstract: Biochar supplements to degraded soils have the potential to improve crop yield and soil quality. We hypothesize that the biochar chemical production process can be tailored to form designer biochars that have specific chemical characteristics matched to selective chemical and/or physical issues of a degraded soil. We produced biochars from peanut hulls, pecan shells, poultry litter and switchgrass at temperatures ranging from 250 to 700 degrees Celsius. Biochars were characterized by percentage of mass recovery, and by their physical and chemical characteristics. These were mixed at 2 percent weight basis with a Norfolk loamy sand (Fine-loamy, kaolinitic, thermic Typic Kandudults) and was laboratory incubated to examine changes in the Norfolk’s soil properties. Higher pyrolysis temperatures resulted in lower biochar mass recovery, greater surface areas, pH, higher ash contents, and minimal total surface charge. Removal of volatile compounds at the higher pyrolysis temperatures also caused biochars to have higher percent carbon but much lower hydrogen and oxygen contents. Nuclear magnetic resonance spectral analyses confirmed that aliphatic compound losses occurred at the higher pyrolysis temperatures causing the remaining structures to be composed mostly of poly-condensed aromatic moieties. Biochars produced at higher pyrolysis temperatures increased soil pH values while biochar made from poultry litter feedstock grossly increased Mehlich-1 extractable phosphorus and sodium concentrations. Water holding capacity varied after biochar incorporation. 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. [GRACEnet Publication]