7 Factors Affecting Composting and Their Role in Different Stages of Compost Formation

Did you know that annual waste generation is projected to increase by 73% from 2020 to 2050, reaching a staggering 3.88 billion tonnes? 

This alarming trend, highlighted by the World Bank, calls for immediate action in adopting sustainable waste management practices, such as composting.

Composting is a natural process that transforms organic waste into nutrient-rich compost. It is not only an age-old practice but also a powerful practice in sustainable waste management. 

In this blog, we will delve into the factors affecting composting, including stages of composting, and its significance in effective waste management.

What Factors Affect the Composting Process?

Composting, as a biological process, is influenced by various factors that can directly impact its efficiency and effectiveness. They are:

Understanding and managing these factors is essential for successful composting. Here are some key factors that affect the composting process:

1. Aeration (Oxygenation)

Composting requires adequate oxygen supply for breaking down organic material by microorganisms. 

Aerobic microorganisms need oxygen for breaking down organic material and supplying oxygen for rapid composting. 

The composting environment should maintain oxygen level around 10% for ideal composting conditions. 

If there is excess of oxygen (>15%) it may cause dehydration and decrease in temperature of compost materials.

This will hamper the production of spores and enzymes necessary for degradation of organic raw materials.

Low oxygen level may cause moisture development and hydration which may create anaerobic conditions. 

Odor may also develop due to the presence of acetic acid, H2S and CH4.

2. Carbon dioxide (CO₂ ) generation

Carbon Dioxide (CO₂) plays a crucial role in the aerobic processes involved in composting and the respiratory activities of microbes. 

During composting, the oxidation of carbon in the raw material results in the production of biomass and the release of CO₂ through microbial respiration. 

Approximately, about 2-3 kg of CO₂  is generated per tonne of composting material which has a minimal environmental impact as it is utilized by plants and autotrophic microorganisms for photosynthesis.

3. Temperature

Temperature is an important factor that influences the composting process. In the initial stages, it starts with ambient temperature and varies depending on different stages. 

During composting, the temperature may rise up to 65°C (149°F) due to microorganism activity. Maintaining a high temperature for an extended period is beneficial as it accelerates decomposition. 

However, it’s important to avoid sudden drops in temperature, as they can hinder the process, increasing the composting time.

It is necessary to closely monitor the temperature and make necessary adjustments to keep it within the optimal temperature range. 

This may include insulating the compost pile during colder periods or adding nitrogen-rich materials to fuel the microbial activity.

4. Moisture content

Moisture content directly impacts the microbial activity of the microorganisms in composting organic materials. 

The water present in the compost helps these microorganisms in carrying essential plant nutrients and energy in their cell membranes. 

If the compost has less than the required moisture, it will make the compost dry causing dehydration. This will hinder the decomposition and slow down the process. 

Excessive moisture will make the compost environment anaerobic. The moisture level varies depending on the particle size and physical condition of the composting system.

5. Carbon-to-nitrogen ratio

The carbon-to-nitrogen ratio of the compost should be maintained for a healthy composting process. This ratio depends on the compost ingredients used in the process. 

The greens are carbon rich. The examples include grass clippings, weed seeds, fruit and vegetable scraps, plant trimmings, coffee grounds, etc. 

The browns are nitrogen rich. The examples include dry leaves and grasses, wood chips, cardboard, hay, straw, saw dust, etc.

The optimal C/N ratio is 30:1. It varies from 35:1 to 15:1 during the composting process.

6. PH level

The PH level tells about how acidic/basic our system is. Generally, organic materials with a high range of PH (3 to 11) are suitable for composting. 

The PH level depends on the raw materials added and changes during different stages of the process, which we will discuss later in the blog.



Initially during the process, the PH will be slightly on the acidic scale due to release of organic acids by the microorganisms. 

Then gradually it will become alakalized due to conversion of ammonium into ammonia during the thermophilic phase. 

The PH is an important factor because each group of microorganisms prefers certain PH for their health and growth. 

Most bacterial functions occur at 6 to 7.5, while most fungal functions occur at 5.5 to 8.0. The ideal range for a composting environment lies between 5.8 to 7.2. 

These pH ranges are approximate and can vary depending on the specific microbial species.

7. Particle size

For faster composting, smaller particle sizes are preferred as compared to large chunks of organic material. 

Smaller the particle size greater the specific surface area of the composting material. This will facilitate more area for aeration which will boost the decomposition process. 

The ideal size is between 5 to 20 cm for composting materials. However, one should also note that the smaller particle doesn’t always suffice. 

The raw material should also have enough strength to support proper oxygen supply between the interstices.

Maintaining optimal levels of these factors during composting might be a challenging task, and requires proper planning and management. 

Composters should be ready and equipped with potential solutions for problems occurring during composting.

How These Factors Evolve During Different Stages of Composting?

All these factors affecting composting go through dynamic changes during the composting process.

These dynamic changes are differentiated based on the temperature changes and microbial activity during the process. They are often referred to as the 4 stages of composting.

Cooling phase and maturation phase are often used interchangeably. But there are subtle differences in each phase which makes them distinct. Let’s discuss a bit deeply about each phase:

1. Hot stage (mesophilic stage):

In the initial stage, the composting process kicks off at ambient temperature, and within a short span, the temperature surges to around 45°C (113^o F). 

During this phase, diverse groups of mesophilic bacteria engage in metabolic activities, utilizing the nitrogen (N) and carbon (C) of organic matter to fuel their growth. 

Sugars and soluble compounds are broken down, leading to the production of organic acids and a potential drop in pH. This hot phase typically lasts for two to eight days.

2. Curing stage (thermophilic and hygienization stage):

As the temperature surpasses 45°C (113^o F), mesophilic microorganisms make way for thermophilic microorganisms, particularly thermophilic bacteria capable of thriving at higher temperatures. 

These heat-loving microbes play a crucial role in decomposing complex organic matter, such as cellulose and lignin. 

Ammonia is released as nitrogen undergoes conversion, causing the pH of the compost pile to rise. 

At temperatures exceeding 60°C (140^o F), spore-producing bacteria and actinobacteria take charge, breaking down waxes, hemicellulose, and other complex carbon compounds. 

This phase is also known as the hygienization phase as it eliminates potential contaminants like faecal bacteria (e.g., Escherichia coli, Salmonella sp.), helminth cysts and eggs, phytopathogenic fungi spores, and weed seeds. 

It serves as a critical step in ensuring the compost’s hygiene and safety.

3. Cooling or mesophilic stage II

After the carbon and nitrogen sources in the composting materials are depleted, the temperature gradually decreases to around 40-45°C (104-113^o F). 

During this mesophilic phase, cellulose degradation continues, visible fungi appear, and polymers break down. 

As the temperature drops below 40°C (104^o F), the activity of mesophilic organisms resumes. The pH of the compost pile may slightly decrease, while generally remaining slightly alkaline. 

Fungal growth becomes more pronounced, with visible structures taking shape. This cooling phase spans several weeks and can sometimes be mistaken for the maturation phase.

4. Maturation stage

In the final phase, the temperature of the compost pile reaches ambient levels, typically ranging from 20-30°C (68-86^o F). 

Condensation of carbonaceous compounds and polymerization occur during maturation, contributing to the formation of fulvic and humic acids. 

This phase solidifies the compost’s stability and prepares it for utilization as a potent soil amendment.

Why is Composting Important?

Its significance extends far beyond the realm of waste reduction, as it contributes to soil health, environmental sustainability, and the creation of a circular economy. While composting offers numerous benefits, here are few major ones:

Waste diversion

Composting diverts waste from landfills, where it would otherwise decompose anaerobically and produce methane—a potent greenhouse gas. 

By diverting degradable waste to composting facilities or engaging in home composting practices, we can significantly reduce methane emissions and alleviate the burden on landfills.

Enriching soil quality

Compost, often referred to as “black gold,” acts as a valuable source of organic matter for soil. 



When incorporated into the earth, it improves soil structure by enhancing its ability to retain moisture and allow for proper aeration. 

This improved structure not only prevents soil erosion but also creates an optimal environment for the growth of beneficial soil organisms.

Retaining moisture in drought conditions

One of the significant advantages of composting lies in its ability to hold moisture in the soil, particularly during drought conditions. 

The organic matter in compost acts as a sponge, absorbing and retaining water, thus reducing water loss through evaporation. 

This water-holding capacity of compost helps to alleviate the impacts of dry spells, ensuring that plants have access to the moisture they need to thrive.

Enhancing physico-chemical properties

Composting goes beyond supplying the organic matter. It enriches the soil with vital nutrients. 

As waste decomposes, it releases essential elements such as nitrogen, phosphorus, and potassium, along with a range of micronutrients. 

These nutrients contribute to the improvement of the soil’s physico-chemical properties, fostering an environment conducive to plant growth and development.

Binding agent for soil health

In addition to providing essential nutrients, compost acts as a binding agent for soil particles. This binding property enhances soil structure, stability, and fertility. 

By binding soil particles together, compost creates an optimal habitat for roots to penetrate, absorb nutrients, and establish strong plant structures. 

The availability of nutrients in compost further strengthens the health and resilience of plants, making them less susceptible to diseases and pests.

Reducing reliance on chemical fertilizers

Composting plays a crucial role in reducing our dependence on chemical fertilizers. By incorporating nutrient-rich compost into the soil, farmers and gardeners can supplement or even replace synthetic fertilizers. 

Chemical fertilizers do provide essential nutrients to the crops but it doesn’t help in improving the overall soil quality. Hence, it doesn’t have any lasting impact. It also attracts pests. 

This sustainable practice not only reduces the potential environmental harm caused by chemical fertilizers but also contributes to the long-term health of the soil and surrounding ecosystems.

Balancing the optimal levels of all these factors is quite challenging and you may face some problems to maintain them in a controlled environment.

Conclusion

Composting serves us as nature’s gift that helps in managing waste generated by us in a sustainable manner.

Throughout the composting process, factors like aeration, carbon dioxide generation, temperature, carbon-to-nitrogen (C/N) ratio, PH level and particle size exert direct influence. These factors vary during the process along with temperature changes and microbial activity. 

Also, these changes are differentiated based on the temperature changes and termed as 4 stages of composting – Mesophilic, Thermophilic, Mesophilic phase II & Maturation phase.

Understanding such factors and stages allows composting practitioners to monitor and optimize the process, ensuring the production of high-quality compost.

By utilizing these factors and thorough understanding of composting stages, we can harness the full potential of this natural process and create exceptional compost that nourishes our soil and sustains our environment.