Accelerated thermophilic aerobic digestion of poultry wastes for rapid composting

The Australian chicken industry produces significant amounts of waste. The meat chicken industry alone produces about 1 million tonnes of poultry litter, with high levels of manure and wastes (mortalities and eggs) generated annually by the egg chicken industry. Poultry producers face increasing social and regulatory pressure for waste management but are limited by economically viable and sustainable waste management options. Therefore, management and disposal of poultry waste has increasingly become a major cost for industry. The conventional methods of poultry waste management are windrow composting and direct application to cropping land. The current research evaluated an alternative method for rapid composting using the accelerated thermophilic aerobic digestion (ATAD) system. The ATAD in-vessel process allows for rapid biodigestion of waste aided by effective inoculum leading to digested materials that can be subsequently and rapidly composted allowing savings of space and time. 

Using 16S rRNA sequencing, each of three inocula (T1, T2 and T3) were diverse in microbiota at the family level of taxonomy with prevalence of Clostridiaceae and Peptostreptococcaceae (T1), Comamonadaceae (T2) and Lactobacillaceae (T3). The biodigester pasteurised the feedstock at temperatures greater than 90°C for 4 h then a further 20 h biodigestion at 60°C and composts reached stability by 9 weeks post-biodigestion, compared to 6 to 9 months for conventional windrow composting systems. Particle size grading at 24 h and in the final compost (31 weeks) indicated T1 inoculum accelerated feedstock degradation more rapidly than other inocula and the control batches. Bacteria pathogens were not detected from the high-risk feedstock-based compost throughout the composting process. In addition, the final compost was value-added through pelletisation process and no significant differences in abundance and diversity of bacterial microorganisms were indicated. 

The research validated ATAD as biodigestion technology to enable subsequent rapid composting, reaching stability within 90 days, the inocula accelerated the composting process compared to control and also altered the microbiome of the compost during biodigestion phase, although final composts did not show significant differences in abundance or diversity of microorganisms.