Understanding Aerobic Composting
Aerobic composting is one of the most effective and environmentally sound techniques for converting organic waste into nutrient-rich soil amendments. This method enables efficient decomposition through oxygen-fuelled biological activity by harnessing the natural metabolic processes of aerobic microorganisms, including bacteria, fungi, and earthworms.
As these organisms break down organic matter, they generate heat, water vapour, and carbon dioxide, transforming raw waste into humus-like compost. Maintaining adequate oxygen levels is critical for this process to occur effectively. Without proper oxygenation, microbial efficiency drops, decomposition slows, and undesirable anaerobic byproducts begin to form.
This blog discusses why accurate oxygen measurement is essential for high-performance composting and how SST’s OXY-FLEX Oxygen Analyser supports process control in demanding compost environments.
The Biological Stages of Aerobic Composting
The composting process occurs in four primary phases, each dependent on oxygen availability:
1. Mesophilic Phase (20–45°C):
In the initial stage, mesophilic microbes rapidly consume simple organic materials such as sugars and amino acids. This activity generates heat and raises the temperature of the compost.
2. Thermophilic Phase (45–65°C):
As temperatures climb, thermophilic organisms take over, breaking down more complex compounds like cellulose and proteins. High temperatures at this stage help destroy pathogens and weed seeds. However, exceeding 65°C may harm beneficial microbes and trigger unwanted emissions, making oxygen regulation essential.
3. Cooling Phase:
As microbial activity slows, the compost temperature drops. Mesophilic microbes return to complete the breakdown of remaining organic matter.
4. Maturation (Curing) Phase:
The compost stabilizes as microbial action converts resistant material into humic substances. The end product becomes nutrient-dense, with a dark, crumbly texture, an earthy aroma, and signs of well-managed, mature compost.
Why Monitoring Oxygen Matters
Maintaining appropriate oxygen levels throughout the composting process offers several advantages that directly impact efficiency, quality, and environmental impact:
Supports Optimal Microbial Activity
Aerobic organisms depend on oxygen for metabolism. Continuous monitoring ensures these microbes operate at peak efficiency, accelerating the breakdown of organic waste.
Prevents Anaerobic Conditions
Insufficient oxygen encourages anaerobic microbes, which generate methane and hydrogen sulfide, contributing to unpleasant odours and harmful emissions.
Maintaining aerobic conditions reduces these risks and promotes faster, cleaner composting.
Enhances Decomposition Rate
Well-aerated compost piles decompose significantly faster. Real-time oxygen monitoring allows timely intervention, such as turning or aerating the pile to maintain optimal airflow.
Regulates Compost Temperature
Oxygen fuels microbial respiration, which in turn generates heat. Controlled oxygen input ensures the pile stays within the desired temperature range—safely high enough to sterilize the compost without damaging beneficial organisms.
Preserves Nutrient Content
Aerobic conditions reduce the loss of key nutrients like nitrogen and phosphorus, enhancing the final compost as a soil improver.
Improves Product Quality
Compost processed with proper oxygenation tends to be uniform, odour-free, and biologically stable, ideal for agricultural and horticultural use.
Target Oxygen Levels
For optimal aerobic activity, oxygen concentrations within the compost should typically remain between 5% and 15%. However, ideal levels may vary depending on:
- Feedstock composition
- Moisture content
- Microbial population
- Pile structure and aeration method
Regular turning and mixing help maintain uniform airflow and avoid anaerobic pockets, especially in larger or denser piles.
Accurate Oxygen Measurement Techniques
Several methods exist for assessing oxygen content in compost:
- Respirometry measures microbial respiration indirectly through carbon dioxide production.
- Visual and olfactory inspection can suggest poor aeration (e.g., foul odours).
- Direct oxygen sensing using industrial-grade oxygen probes provides the most accurate and actionable data.
For precision monitoring, probes must withstand high humidity, variable temperatures, and physical debris, making durability and measurement reliability critical selection criteria.
Reliable Oxygen Monitoring for Composting Environments
The OXY-FLEX Oxygen Analyser from SST is a proven solution for real-time oxygen measurement in demanding conditions such as composting facilities. Compact and robust, it delivers accurate, continuous data essential for maintaining aerobic conditions and ensuring efficient decomposition.
With options to measure oxygen concentrations from 0–25% or 0–100%, the analyser supports a wide range of composting setups. Multiple probe lengths allow monitoring at various depths, while the standard 4–20 mA output ensures seamless integration with process control systems. Calibration can be automatic or manual, and no special software is required, simplifying both setup and ongoing operation.
Built to perform in high-moisture, corrosive environments, the stainless steel construction ensures long-term durability. Its compact design makes it suitable for installation across different zones, providing flexible deployment and dependable readings. By offering real-time insight into oxygen levels, OXY-FLEX enables better control of aeration, improves compost quality, reduces energy use, and helps avoid anaerobic conditions.
Efficient composting depends on accurate oxygen monitoring. With the OXY-FLEX, operators gain a low-maintenance, high-performance tool to enhance process control, optimise productivity, and consistently produce high-quality compost.
To discuss your application or for more information please contact one of our highly trained engineers today.
