THERMOCHEMICAL PROCESSING OF AGRICULTURAL WASTES TO VALUE-ADDED PRODUCTS AND BIOENERGY
Location: Commodity Utilization Research
Title: Lead retention by broiler litter biochars in small arms range soil: Impact of pyrolysis temperature
Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 1, 2012
Publication Date: May 1, 2012
Citation: Uchimiya, M., Bannon, D.I., Wartelle, L.H., Lima, I.M., Klasson, K.T. 2012. Lead retention by broiler litter biochars in small arms range soil: Impact of pyrolysis temperature. Journal of Agricultural and Food Chemistry. 60:5035-5044.
Interpretive Summary: This study demonstrates how biochars made from chicken manure can be used to remove toxic heavy metals such as lead in contaminated soils. Specific focus of this study was on the temperature used to produce biochars from chicken manure. The results obtained in this study are applicable to cost-effective remediation of thousands of shooting ranges across the United States. In addition, these biochars can be used in agriculture as a cheap, pathogen-free fertilizer. Biochars, especially when produced at lower temperature, effectively removed target contaminants (lead, copper and zinc) in shooting range soils, without side-effects such as the release of other undesirable elements. This study also provided information on bioavailability of heavy metals in contaminated soils. Biochars used in this study will have a potential for large-scale field application to remediate a wide range of soil types having problems related to heavy metals, and will at the same time allow end-user to reduce carbon footprint.
Phosphorus-rich manure biochar has a potential for stabilizing Pb and other heavy metal contaminants, as well as serving as a sterile fertilizer. In this study, broiler litter biochars produced at 350 and 650 °C were employed to understand how biochar’s elemental composition (P, K, Ca, Mg, Na, Cu, Pb, Sb, and Zn) impacts the extent of heavy metal stabilization and plant nutrient release. Soil incubation experiments were conducted using a sandy, slightly acidic (pH 6.11) Pb contaminated (19,906 mg kg-1 total Pb primarily as PbCO3) small arms range (SAR) soil fraction (<250 'm) amended with 2-20 wt% biochar. The Pb stabilization in pH 4.9 acetate buffer reached maximum at lower (2-10 wt%) biochar amendment rate, and 350 °C biochar containing more soluble P was better able to stabilize Pb than the 650 °C biochar. The 350 °C biochar consistently released a greater amount of P, K, Mg, Na, and Ca than 650 °C biochar in both unbuffered (pH 4.5 sulfuric acid) and buffered (pH 4.9 acetate) systems, despite 1.9 to 4.5-fold greater total content of the 650 °C biochar. Biochars, however, did not influence the total extractable Pb over three consecutive equilibration periods consisting of (1) 1 wk in pH 4.5 sulfuric acid (simulated leaching by rainfall), (2) 1 wk in pH 4.9 acetate buffer (standard solution for Toxicity Characteristic Leaching Procedure), and (3) 1 h in pH 1.5 glycine at 37 °C (in vitro bioaccessibility procedure). Overall, lower pyrolysis temperature was favorable for stabilizing Pb (major risk driver of SAR soils), and to release P, K, Ca, and other plant nutrients in a sandy acidic soil.