Characterization of Designer Biochar Produced at Different Temperatures and Their Effects on a Loamy Sand
Keywords:designer biochar, pyrolysis, feedstock, soil improvement, GRACEnet
Biochar additions to degraded soils have the potential to improve crop yield and soil quality. We hypothesize that the biochar 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 250ºC to 700ºC. Biochars were characterized by % mass recovery and by their physical and chemical distinctiveness. These were mixed at 2% w/w with a Norfolk loamy sand (fine-loamy, kaolinitic, thermic Typic Kandiudults) and were laboratory incubated to examine changes in the Norfolk's soil properties. Higher pyrolysis temperatures resulted in lower biochar mass recovery, greater surface areas, elevated pHs, higher ash contents, and minimal total surface charge. Removal of volatile compounds at the higher pyrolysis temperatures also caused biochars to have higher percentages of carbon (C) but much lower hydrogen (H) and oxygen (O) contents. 13C NMR spectral analyses confirmed that aliphatic structure 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 (P) and sodium (Na) 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, biochars may be designed to selectively improve soil chemical and physical properties by altering feedstocks and pyrolysis conditions.
Permanent URL: http://hdl.handle.net/2047/d10019637