Work

Phosphate sorption by iron-activated biochars derived from dephosphatized poultry litter and swine manure

Year: 2026

Type: article

Abstract: The removal of phosphorus (P) from animal manure (dephosphatation) produces a low-P manure byproduct. In this work, we aimed to upcycle dephosphatized poultry litter (PL) and swine manure (SM) into biochar-based P sorbents via pyrolysis and chemical activation. We evaluated different pre-and post-pyrolysis magnesium and iron (Fe) activation methods and determined that post-pyrolysis Fe-activation was the most effective at increasing biochar's affinity for soluble P. Phosphorus sorption by Fe-activated, dephosphatized poultry litter (FewPL) and swine manure (FewSM) was strongly pH-dependent, with higher P sorption under more acidic conditions. Experimental and modeling results showed that FewPL had a higher affinity for P than FewSM, although both biochars removed ≥95% of added P from solution at pH < 5. Attenuated Total Reflectance-Fourier Transform Infrared spectroscopic analysis of biochar pre- and post-P sorption suggested P association with Fe(III)-OH groups as the dominant adsorption mechanism for both biochars. Measured maximum P sorption capacities (Q M , obtained at pH 6.2) from isotherm experiments were 21.4 and 14.1 mg P g −1 for FewPL and FewSM, respectively. To obtain estimates of Q M under environmentally relevant P concentrations, we used an alternative batch experimental method whereby biochar was repeatedly equilibrated with 2.5 mg P L −1 (pH 6.2). Under these conditions, Q M values for FewPL and FewSM were 1.8 and 1.1 mg P g −1 , respectively. Overall, our results demonstrate that pyrolysis and Fe-activation are viable for converting dephosphatized PL and SM into biochar-based P sorbents as an approach for utilizing animal waste byproducts to mitigate P contamination in soil and water.

Source: Cleaner Engineering and Technology

DOI: 10.1016/j.clet.2026.101208

Authors: Joshua T. Padilla, Ariel A. Szogi, Donald W. Watts

Institutions: Agricultural Research Service, United States Department of Agriculture

Language: English

Topic: Phosphorus and nutrient management

Subfield: Waste Management and Disposal

Field: Environmental Science

Domain: Physical Sciences

SDGs: Responsible consumption and production, Clean water and sanitation, Zero hunger

Open Access status: gold

Estimated APC paid: $2,220