Oxidized lignite reduces greenhouse gas emissions, nitrogen loss, and heavy metal bioavailability in pig manure

Considerable carbon (C) and nitrogen (N) losses, along with potential heavy metal pollution from pig manure, pose substantial environmental and public health risks. This study investigates the use of thermal air oxidized lignite, treated at 150 °C for 2 hours, as a novel approach to address these challenges during a 14-day incubation period of pig manure. The oxidation process increased the intensity of oxygen-containing functional groups, with the consequent adsorption capacity for Cd and NH 3 by 96.96 % and 77.68 %, respectively. Spectroscopic analysis confirmed the chemical adsorption mechanism, indicating the formation of covalent bonds on the lignite surface. The application of 20 % oxidized lignite (T3) to pig manure demonstrated outstanding N retention, with an increase of 11.85 % by the end of the incubation, while also reducing NH 3 and N 2 O emissions by 92.53 % and 30.27 %, respectively. Additionally, T3 reduced CO 2 and CH 4 emissions by 52.91 % and 31.11 %, respectively. Moreover, T3 lowered the bioavailability of heavy metals including Zn, Cu, Cr, and Cd by up to 73.60 %. These findings demonstrate the potential of oxidized lignite as a low-cost, multifunctional additive for reducing nutrient losses, stabilizing heavy metals, and mitigating greenhouse gas emissions in intensive livestock systems. • Oxidized lignite enhanced Cd and NH 3 adsorption by 96.96 % and 77.68 %. • NH 3 formed quaternary N, amide, and amine on the lignite surface. • 20 % oxidized lignite lowered gaseous C and N losses from pig manure. • 20 % oxidized lignite reduced Zn, Cu, Cr, and Cd bioavailability during incubation. • A low-cost strategy to reduce emissions and stabilize nutrients in manure.