Alkaline Hydrolysis of Poultry Carcasses and Health Risk Assessment of Exposure to Target Volatile Organic Compounds

Abstract

Animal carcass management is an essential part of a livestock production system. Alkaline hydrolysis is a relatively new disposal method used to digest and break down animal tissues. Despite the effectiveness of inactivating pathogens, alkaline hydrolysis has not been widely accepted as a disposal method because of its high capital and operating costs when done at high temperatures and pressure. The objectives of this research were (1) to test if alkaline solutions at ambient temperature and pressure can be used to hydrolyze poultry carcasses; (2) to quantify target VOCs emitted from carcasses, and (3) to neutralize and aerobically treat hydrolysates to prepare liquid fertilizer. 1 molar (M), 2 M, and 4 M potassium hydroxide solutions were used to hydrolyze chicken carcasses, and the headspace was sampled to quantify target VOCs. The pH of the hydrolysates stayed above 13.1 during the study, which was considered sufficient for eliminating pathogens of concern. Concentrations of target VOCs fluctuated over 10 weeks, and concentrations of trimethylamine (TMA), acetic acid, and propionic acid exceeded their recommended inhalation exposure limits. It was found that more than 17% of the workers exposed to the process headspace gases for 3 h a day would be at a high risk of developing serious chronic health problems. Although the results of this study indicated that chicken carcasses can be hydrolyzed under ambient conditions, they raised concerns about the health risks associated with inhalation exposure to the gases produced during the process. Future studies are needed to adjust daily exposure times depending on the ventilation rates of full-scale alkaline hydrolysis sites.