Odor generation patterns during different operational composting stages of anaerobically digested sewage sludge

Area of Science:

• Environmental Science
• Waste Management
• Air Quality

Background:

• Anaerobically digested sewage sludge (ADS) composting is a common waste treatment method.
• Odor generation during composting poses environmental and social challenges.
• Understanding odor patterns is crucial for effective management.

Purpose of the Study:

• To evaluate global patterns of odor generation and odorant composition during ADS composting.
• To identify critical operational stages for odor emission.
• To characterize the key odor compounds at different composting phases.

Main Methods:

• Pilot-scale composting of ADS.
• Gas emission sampling during storage, active aeration, turning, and curing.
• Odor emission rate (OER) measurement using dynamic olfactometry.
• Odorant compound quantification via GC/MS and odor activity value (OAV) calculation.
• Principal component analysis (PCA) for pattern recognition.

Main Results:

• Ammonia (55.5%) and volatile sulfur compounds (VSCs) (20.6%) were the primary emitted pollutants.
• The first eight days of aeration and the first turning were critical odor generation stages (OER 30–317 OU_E h^-1 kg^-1ADS).
• Dimethyl disulfide, dimethyl sulfide, and methanethiol were predominant early odorants; hydrogen sulfide dominated later stages.

Conclusions:

• Odor generation is highly dependent on the operational stage of ADS composting.
• Targeted management during the initial aerobic treatment and first turning is essential for odor control.
• Odor composition shifts significantly from early to later composting phases, requiring distinct mitigation strategies.