Engineering Poultry Litter Biochar: Capturing Phosphorus, Improving Soil Phosphorus Management, and Protecting Water Quality
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Long-term application of poultry litter (PL) manures in watersheds with dense animal production has increased soil phosphorus (P) concentration, exceeding plant, and soil assimilative capacities, often leading to P movement into down gradient water bodies that can result in eutrophication. This presentation describes research on making useful biochar products out of PL. Initially, we hypothesized that turning PL into biochar would change the solubility of the P in the PL such that it would no longer leach and would sequester excess P in P-saturated soils. PL biochar does have reduced P solubility, but sequestering additional P requires activation of the PL with magnesium chloride (MgCl2). We also report that PL biochar is highly effective at sorbing and retaining heavy metals such as copper, zinc, cadmium, nickel and lead. This means that PL biochar can be used as an in situ amendment for reducing the bioaccessibility of these metals in contaminated soils. These beneficial uses for PL provides additional markets for producers and provides a beneficial use for the manures that might otherwise be considered waste materials. This innovative technology will be a valuable tool for land and environmental managers in areas with known issues with excess soil P and for those tasked with revegetating metal-contaminated soils.