Selective release of inorganic constituents in broiler manure biochars under different post-activation treatments

Authors: Lima, Isabel; Klasson, K Thomas; Uchimiya, Sophie

Submitted to: Journal of Residuals Science & Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/17/2015
Publication Date: 1/1/2016
Citation: Lima, I., Klasson, K.T., Uchimiya, M. 2016. Selective release of inorganic constituents in broiler manure biochars under different post-activation treatments. Journal of Residuals Science & Technology. 13(1):37-48.

Interpretive Summary: Animal manures such as poultry litter contain a significant fraction of inorganic material that can significantly affect the final physical, chemical and sorptive properties of activated chars. This study traces key inorganic elements (Ca, Fe, K, Mg, Na, and P) from raw poultry manure to respective activated chars produced under different processing conditions and their selective removal upon acid and water treatments. Pelletized samples of broiler litter and cake were pyrolyzed at 700°C for 1 hour and steam activated for 45 min at 800°C and subsequently either acid washed or rinsed. Mineral composition concentrated during pyrolysis/activation and acid wash and water treatments were effective at removing loose inorganic content with highest extraction rates as percentage of original amounts observed after acid wash for potassium (37-100%) and sodium (27-49%) and lowest for iron (0-0.02%). While these two elements were easily removed in either treatment, the remaining elements (P, Ca, Mg, and Fe) leached significantly less in water treatment indicating selective removal dependent on initial manure composition and effect of pyrolysis/activation process on element solubility. Negligent amounts of heavy metals leached for either treatment (acid wash or water rinse). Post-activation treatments herein studied can improve usability of poultry manure-based chars in wastewater applications by avoiding leaching of potentially unwanted elements, without compromising their functionality.

Technical Abstract: Previous studies determined that poultry litter is a desirable feedstock for activated biochars with enhanced adsorption towards cations. Animal manures such as poultry litter contain a significant fraction of inorganic material that can significantly affect the final physical, chemical and adsorptive properties of the carbons. This study traces key inorganic elements (Ca, Fe, K, Mg, Na, and P) from raw poultry manure to respective activated biochars produced under different activation conditions and their selective fate upon acid and water treatments. Pelletized samples of broiler litter and cake were pyrolyzed at 700°C for 1 hour and steam activated at 1, 3 or 5 mL/min for 45 min at 800°C and subsequently either acid washed or rinsed. Mineral composition was concentrated during pyrolysis/activation. Acid wash and water treatments were effective at removing unbound inorganic content with highest extraction rates as percentage of original amounts observed after acid wash for potassium (37-100%) and sodium (27-49%) and lowest for iron (0-0.02%). While these two elements were easily removed in either treatment, the remaining elements (P, Ca, Mg, and Fe) leached significantly less in water treatment indicating selective removal dependent on element and treatment as influenced by initial manure composition and the effect of pyrolysis/activation process on their solubility. Volatilization rates during pyrolysis were estimated based on elemental compositions and yield data, and were found to be highest for potassium and negligent for sodium. Concentration of heavy metals also increased in the activated biochars with copper and zinc being present at the highest concentrations, however, negligent amounts leached for either treatment (acid wash or water rinse). Post-activation treatments herein studied can improve usability of poultry manure-based biochars in wastewater applications by avoiding leaching of potentially unwanted elements, without compromising their functionality.