The Importance of Oxygen Measurement in Aerobic Composting

Measuring oxygen in compost

The Importance of Oxygen Measurement in Aerobic Composting

Composting has long been a traditional technique for repurposing organic waste. Among the diverse composting methods available, aerobic composting is particularly noted for being both eco-friendly and effective in transforming organic waste into nutrient-rich fertilizer.

In this blog, we explore the aerobic composting process and discuss the significance of monitoring oxygen levels to achieve the best possible decomposition outcomes.

The Role of Oxygen in the Aerobic Composting Process

Aerobic composting relies on the activity of soil organisms, such as fungi, bacteria, and earthworms, to decompose organic waste using oxygen. This process primarily results in the production of carbon dioxide, water, heat, and humus-like decomposition products that can be utilized as fertilizers. The composting process can be divided into the following stages:

1. Initial Phase (Mesophilic Phase): During this phase, mesophilic microorganisms, which thrive at moderate temperatures (20 to 45°C), rapidly break down the readily available and easily degradable components of the organic waste, such as sugars, amino acids, and simple carbohydrates. The temperature within the compost pile begins to rise due to the heat generated by microbial activity.

2. Thermophilic Phase: As the temperature increases (45 to 65°C), thermophilic microorganisms, which thrive in higher temperatures, take over the decomposition process. These microorganisms break down more complex compounds like cellulose, hemicellulose, and proteins. The high temperature during this stage helps eliminate weed seeds, pathogens, and pests. It's essential to keep the temperature below 65°C to avoid killing beneficial microorganisms and generating unwanted emissions.

3. Cooling Phase: Once organic matter has been decomposed, the microbial activity decreases, leading to a decline in temperature. Mesophilic microorganisms become active again, breaking down any remaining organic materials. During this phase, the compost pile gradually returns to the ambient temperature.

Maturation Phase (Curing Phase): This final stage involves the stabilization and humification of the remaining organic matter. Microorganisms continue to break down more resistant compounds and produce humic substances, which are essential for soil fertility. The compost is considered mature when the temperature stabilizes close to the ambient temperature, and the material exhibits a dark, crumbly texture with an earthy aroma. This mature compost is rich in nutrients and organic matter, making it an excellent soil amendment for gardens and landscapes.

The Importance of Oxygen Measurement in Composting

Monitoring oxygen levels and ensuring they are maintained in the compost is critical for the effectiveness and overall quality of the composting process. The following are some key reasons that underscore the significance of oxygen management in aerobic composting:

Optimal microbial activity:

Aerobic microorganisms require oxygen to break down organic matter efficiently. When oxygen levels are maintained, these microorganisms can thrive and effectively decompose the organic waste. Inadequate oxygen levels can lead to a decrease in microbial activity, slowing down the composting process.

Prevention of anaerobic conditions:

If oxygen levels fall too low, anaerobic microorganisms may dominate the decomposition process. This anaerobic decomposition is not only slower and less effective than its aerobic counterpart but also generates unwanted byproducts like methane, a powerful greenhouse gas, and hydrogen sulfide, which releases a foul smell. By maintaining appropriate oxygen levels, anaerobic conditions can be avoided, leading to a more efficient and odorless composting process.

Enhanced decomposition rate:

Adequate oxygen levels support a more rapid decomposition rate, as aerobic microorganisms can break down organic matter faster than anaerobic microorganisms. With proper aeration, the composting process can be completed in a shorter time, producing mature compost more quickly.

Temperature control:

Oxygen is necessary for microbial metabolism, which generates heat during the composting process. When oxygen levels are maintained, microbial activity can be controlled, and the temperature within the compost pile can be regulated more effectively. This helps prevent overheating, which can kill beneficial microorganisms and produce unwanted emissions, while ensuring that weed seeds and pathogens are eliminated through the generated heat.

Preservation of nutrients:

Under aerobic conditions, essential nutrients for plant growth and health, such as nitrogen, phosphorus, and potassium, are conserved and stabilized within the compost. On the other hand, anaerobic conditions may lead to nutrient loss through processes like leaching or the creation of volatile compounds, which diminishes the compost's quality and effectiveness as a fertilizer.

Better compost quality:

A compost pile with proper aeration usually yields a superior end product. Mature aerobic compost is distinguished by its dark color, crumbly consistency, and earthy scent. Abundant in nutrients and organic matter, this high-quality compost serves as an outstanding soil-enhancer for gardens and landscapes.

What level of oxygen is measured?

The optimum oxygen level for aerobic composting typically falls within the range of 5% to 15%. Maintaining an adequate O2 supply throughout the composting process is essential for promoting the growth of aerobic microorganisms, which break down organic materials efficiently and produce heat.

However, the ideal oxygen level depends on factors such as the composition of the compost, temperature, moisture content, and the specific aerobic microorganisms present. To maintain optimal oxygen levels, turning or aerating the compost regularly is recommended. This prevents the formation of anaerobic pockets, which can lead to foul odors and slow decomposition.

It is important to remember that the oxygen level in compost is just one factor influencing the composting process. Other critical factors include moisture content, carbon-to-nitrogen (C:N) ratio, and temperature. Maintaining a proper balance of these factors will help ensure successful composting.

How to measure oxygen in composting

There are several methods to measure oxygen levels in compost, including respirometry and visual inspection. Respirometry testing measures the amount of carbon dioxide (CO2) produced by the aerobic microorganisms in the compost as they respire. Since oxygen consumption and CO2 production are directly related, respirometry can be used to measure oxygen levels in compost indirectly. This can be done using a closed respirometer system or by monitoring gas emissions from the compost pile. Although not as accurate, visual inspection and smelling the compost can provide some information about oxygen levels. Well-aerated compost should have a pleasant, earthy smell, while a strong, foul odor may indicate anaerobic conditions, which are unfavorable for composting.

However, one of the most accurate methods is to measure oxygen directly inside the process using an oxygen probe. Oxygen probes or sensors can be inserted directly into the compost pile to measure the oxygen concentration. Oxygen probes for use in composting are typically more resilient and can withstand the high moisture and temperature conditions often found in compost piles. To achieve a representative measurement of the overall oxygen levels, the oxygen probe should be inserted into the compost pile at various depths and locations while care is taken not to make contact with hard materials.

What are the benefits of using an oxygen probe to measure O2 levels in composting?

Using an oxygen probe to measure O2 levels in composting offers several benefits that can contribute to a more efficient and effective composting process with improved compost quality.

1. Real-time monitoring

Oxygen probes provide real-time, accurate measurements of the oxygen levels in compost piles, allowing users to assess the conditions and adjust as needed to optimize the composting process.

2. Better understanding of composting dynamics

Regular measurements of oxygen levels can help you understand the dynamics of the composting process, such as how aeration, moisture content, and the balance of carbon- and nitrogen-rich materials influence oxygen availability.

3. Early identification of problems

Oxygen probes can help you detect issues such as insufficient aeration, excessive moisture, or an imbalance in the compost materials. Identifying these problems early on allows you to make timely adjustments and prevent potential issues such as anaerobic decomposition, which can produce foul odors and slow the composting process.

4. Efficient use of resources

By using an oxygen probe to monitor oxygen levels, you can make more informed decisions about when to turn the compost pile or add bulking agents, thus minimizing labor and resource inputs while maximizing compost quality and efficiency.

PST Solution

Understanding the importance of oxygen measurement in aerobic composting is crucial for achieving an efficient and effective composting process. By monitoring and maintaining adequate oxygen levels, a favorable environment is created for aerobic microorganisms to thrive, which ensures rapid decomposition, reduced odors, and preservation of essential nutrients.

Oxygen probes and transmitters offer real-time monitoring and accurate measurements, enabling you to make informed decisions and adjustments to optimize the composting process further. PST offers a range of O2 transmitters designed specifically to last longer in this aggressive environment.

The OXY-FLEX Series is a compact and cost-effective zirconia O2 transmitter for measuring percentage level oxygen. The unit can be configured to measure oxygen levels ranging from 0-25% or 0-100% and provides the option for manual or automatic calibration, depending on the client's preferences. The OXY-FLEX has different lengths of stainless-steel probes to enable measurement at different levels within the compost. Simple electronics providing a 4-20mA output allow probes to be positioned across wide production areas. The OXY-FLEX allows for seamless integration into pre-existing systems without necessitating any specialized software.




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