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Engineering Poultry Litter Biochar to Capture Phosphorus to Improve Soil Phosphorus Management and Protect Water Quality


<p>The focus of this project will be on phosphorus (P). Our first objective is using biochar as a means to capture and stabilize P derived from high intensity poultry production. Biochar is a charcoal-like, carbon-rich, porous by-product of the thermal pyrolysis or gasification of organic residues (e.g., manures, green-wastes, etc.). We will take fresh and aged poultry litter (including house bedding material) as a biochar feedstock, and will selectively modify the chemistry of the biochar to promote P capture and stabilization. We propose to introduce a novel modification involving treating biochar feedstocks with water treatment residuals (WTR) [e.g., left-over KAl(SO4) (Alum) after drinking water purification] before pyrolysis. We anticipate that this will result in an increase in P-binding sites in the poultry litter biochar. We will also evaluate other P-capture activating agents such as iron oxyhydroxide [e.g., FeOOH (Goethite)] from coal mine drainage residuals (MDR)9. Next, the WTR and MDR-activated feedstock mixtures will be pelletized (6-mm) and pyrolyzed (i.e., turned into biochar) at temperatures ranging from 350 to 700 °C. This temperature range is most commonly used to produce biochars via slow pyrolysis. We hypothesize that the resulting metal oxide "activated" biochars will have chemical and physical properties specifically attuned to capture P and form stabilized phases of P. Our approach is unique because we are engineering the activation of poultry litter feedstock prior to pyrolysis with the intended outcome to produce biochar possessing properties to bind more P. A second objective of our project is to investigate whether activated and unactivated biochar can be used as soil amendments to reduce available P concentrations in P-saturated soils. By carefully sequestering only a portion of the total soil P pool, we anticipate that the reduction in soluble P will reduce the risk of P leaching and off-site movement from land to surface waters. Using different measures of P availability we will determine if there is a commensurate reduction in P availability. We will also employ greenhouse experiments to carefully balance activated biochar application rates to ensure that there is sufficient plant available P remaining in these soils.</p>

Novak, John
USDA - Agricultural Research Service
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