Enhancing bioavailable carbon sources and minimizing ammonia emissions in distillery sludge and distiller's grains waste co-composting through deep eutectic solvent addition

Abstract

This study introduced two deep eutectic solvents, ChCl/oxalic acid (CO) and ChCl/ethylene glycol (CE), into a 34-day co-composting process of distillery sludge and distiller's grains waste to address challenges related to NH₃ emissions. The addition of DES increased dissolved organic carbon by 68% to 92%, offering more utilizable carbon for microorganisms. SYTO9/PI staining and enzyme activity tests showed the CE group had higher bacterial activity and metabolic levels during the thermophilic phase than the control. Bacterial community analysis revealed that early dominance of Lactobacillus and Lysinibacillus in CE accelerated the onset of the thermophilic phase, reduced pile pH, and significantly decreased urease production by reducing Ureibacillus. Consequently, CE treatment substantially dropped NH₃ emissions by 73% and nitrogen loss by 54%. Besides, CE fostered a more abundant functional microbial community during the cooling and maturation phases, enhancing deep degradation and humification of organic matter.

Keywords: Enzyme activity; Microbial community analysis; Nitrogen loss; Resource utilization; Urease.