Indigenous microbial capability in solid manure residues to start-up solid-phase anaerobic digesters.

Area of Science:

• Agricultural Science
• Environmental Science
• Biotechnology

Background:

• Batch solid-phase anaerobic digestion is a sustainable on-farm technology for solid residue treatment.
• Optimization of start-up and inoculation strategies is crucial for this emerging technology.

Purpose of the Study:

• To evaluate the methane production potential of piggery spent bedding using indigenous microbial communities.
• To investigate the effects of total solids (TS) concentration, temperature, and inoculation on digestion performance.

Main Methods:

• Spent bedding from two piggeries was batch digested at 5%, 10%, and 20% TS.
• Digestion was conducted at mesophilic (37°C) and thermophilic (55°C) temperatures without external inoculum.
• Subsequent batches were inoculated with residues from previous digestions.

Main Results:

• Indigenous microbial communities recovered full methane potential, though treatment times were longer without external inoculum.
• High TS levels (>10%) led to chemical inhibition (ammonia/humic acid), impacting digestion.
• Thermophilic temperatures did not improve performance but increased start-up failure risk.
• Inoculation, particularly with liquid leachate, enhanced start-up and methane recovery.

Conclusions:

• Indigenous microbial communities in piggery residues are capable of full methane potential recovery in solid-phase digestion.
• Chemical inhibition, not microbial community limitations, ultimately constrains solid-phase digestion performance at high solid loadings.
• Optimized inoculation strategies are key for efficient start-up and methane recovery.