Ambient alkaline hydrolysis and anaerobic digestion as a mortality management strategy for whole poultry carcasses

Abstract

Livestock mortality management is a critical factor for ensuring biosecurity, minimizing environmental impact, and maintaining public trust in livestock production agriculture. The number of technologies currently used for livestock mortality management is small, including composting, burial, incineration, landfilling, and rendering. Each technology has advantages and disadvantages which make their suitability situational. In this study, ambient alkaline hydrolysis (AAH) using 2, 4, or 8 M potassium hydroxide at ambient temperature and pressure was explored as a disposal method for whole broiler chicken carcasses. Alkaline hydrolysate (pH > 14) resulting from the process was neutralized by mixing with acidic corn silage, and then utilized as a substrate for anaerobic digestion in bench top continuously stirred tank reactors. All AAH treatments solubilized broiler carcasses within 20 days. Corn silage neutralized 2 M hydrolysate using a 2:1 (w/w) mixing ratio, while 4 M hydrolysate required a 4:1 mixing ratio. Anaerobic digestion of neutralized hydrolysate reduced volatile solids by >96% for all treatments. Highest methane yields were observed from the 2 M hydrolysate (607.2 ± 47.9 g mL^-1 VS), while biogas production from the 8 M hydrolysate was totally inhibited over a total of 42 days. Ambient alkaline hydrolysis followed by silage neutralization and anaerobic digestion provides a feasible, straightforward technology to manage routine and emergency animal mortalities.

Keywords: Biogas; Corn silage; Deadstock; Emergency response; Methane production; Pretreatment.