Biological denitrification potential as an indicator for measuring digestate stability

Area of Science:

• Environmental Science
• Microbiology
• Biotechnology

Background:

• Biological stability is crucial for evaluating digestate's environmental impact in land applications.
• Assessing digestate stability ensures its safe use as an organic amendment.

Purpose of the Study:

• To develop and validate a novel indicator, biological denitrification potential (BDP), for assessing digestate bio-stability.
• To compare BDP with existing stability indices like Respiration Index (RI) and Biochemical Methane Potential (BMP).

Main Methods:

• Investigated digestate samples from a food waste-fed anaerobic digester at varying solid retention times.
• Measured nitrate removal to determine BDP values.
• Analyzed microbial communities, identifying Thiopseudomonas and Pseudomonas as dominant denitrifying bacteria.

Main Results:

• BDP values ranged from 176.3 to 48.3 mg-N/g-VS, correlating with digestion time and total organic carbon.
• BDP trends mirrored RI and BMP, decreasing as digestate stabilization increased.
• Nitrate conversion to N2 gas was the primary process, linked to organic carbon mineralization.

Conclusions:

• Biological denitrification potential (BDP) is an efficient indicator for digestate bio-stability assessment in agricultural and land use contexts.
• BDP offers advantages including no exogenous inoculum, homogenous conditions, and shorter incubation times compared to other indices.
• Digestate bio-stability evaluated by BDP is influenced by its carbon source and intrinsic denitrification activity.