63 / 2025-04-15 11:34:30

Changes in Fertilizer Value, Heavy Metal Residues, Sanitary Indicators, and Agricultural Risk Assessment of Pig Slurry After Biogas Fermentation

Pig slurry; Biogas fermentation; Heavy metal residues; Sanitization; Risk assessment

5.减污降碳与废弃物利用 > （5）畜禽废弃物处理技术：好氧发酵集成技术、卧床垫料再生技术、异位发酵床集成技术、储存发酵集成技术、厌氧发酵集成技术、粪肥制备集成技术、固体粪肥施用技术、液体粪肥施用技术、环境控制集成技术、区域集中处理技术。

[Objective] This study aimed to compare the changes in fertilizer efficiency, heavy metal residues, and sanitary indicators of pig slurry before and after biogas fermentation, and to assess its agricultural risks, providing a theoretical basis for the land application of pig slurry.[Methods] Liquid samples were collected from temporary storage ponds and final sedimentation ponds of three large-scale pig farms in Hunan Province. The study measured changes in heavy metal residues (Cu, Zn, Pb, Cr, Cd, As, Hg), nutrient elements (TN, TP, K), parasite eggs, coliform bacteria counts, and seed germination index. The single-factor pollution index and Nemerow comprehensive pollution index methods were used to evaluate the agricultural risks of biogas-fermented slurry.[Results] The highest residual concentrations of heavy metals in pig slurry were Cu and Zn, with maximum levels of 12.34 mg/L and 36.57 mg/L, respectively, while Hg was undetectable in all samples. After biogas fermentation, the residual concentrations of Cu, Zn, Pb, Cr, Cd, and As significantly decreased. The removal rates were: Cu (88.6%–96.11%), Zn (84.0%–97.07%), Pb (80.8%–92.9%), Cr (88.9%–90.8%), Cd (79.3%–100%), and As (66.7%–86.9%). Nutrient elements—total nitrogen (TN), total phosphorus (TP), and potassium (K)—showed losses, with concentrations ranked as K > TN > TP. TN content ranged from 10.3 mg/L to 131 mg/L, TP from 0.2 mg/L to 10.2 mg/L, and K from 7.12 mg/L to 957 mg/L. The removal rates of hookworm eggs and roundworm eggs reached 100%, while coliform bacteria removal rates were 97.6%–99.6%. The seed germination index of the fermented slurry was 70.2%–82.6%. The single-factor pollution index and Nemerow comprehensive pollution index results for Pb, Cr, Cd, As, and Hg residues indicated clean levels with low agricultural risk. However, Cu and Zn residues showed moderate pollution, posing potential risks for agricultural irrigation.[Conclusion] Pig slurry retains high nutritional value after biogas fermentation and achieves thorough sanitization. It is recommended that the application rate of biogas slurry be controlled appropriately when used for land application.