What is Mineralisation?
Mineralisation through aerobic fermentation is a biological process where micro-organisms (primarily bacteria and fungi) break down organic matter, such as waste, plant residues, or sewage into inorganic compounds in the presence of oxygen. It is a form of nutrient cycling that converts nutrients bound in complex organic structures into simple, bioavailable forms like phosphates, nitrates, and sulphates, which can then be used by plants or other organisms.
How Mineralisation Occurs in Aerobic Conditions
Role of Oxygen
The presence of oxygen allows aerobic heterotrophic bacteria to operate with high efficiency. They “breathe” oxygen to oxidize complex organic compounds, releasing carbon dioxide, water, and energy in the form of ATP.
Decomposition Steps
The process generally occurs in three stages: initial degradation by surface bacteria, an intermediate stage where fermentation byproducts are utilized, and a final stage where remaining substances are oxidized into minerals.
Nutrient Release
Nitrogen in organic matter is converted to ammonium and then to nitrate, while phosphorus and sulphur are released as phosphate and sulphate, respectively.
Environmental Factors
The process thrives in warm, moist, and well-aerated environments.
Applications of Aerobic Mineralisation
Aquaponics and Aquaculture
It is used to turn fish waste (sludge) into nutrient-rich water (supernatant) that can be reused for plant growth.
Waste Management
It is a rapid method for treating sewage and organic solids, reducing organic contaminants by up to 98%.
Composting
The process behind Aerated Compost Tea (ACT) that enhances soil health by accelerating the breakdown of organic material.
Benefits of Aerobic Mineralisation
Nutrient Availability
It directly converts unavailable organic nutrients into forms that plants can readily absorb, such as nitrate and phosphate.
Solid Volume Reduction
It reduces the volume of organic waste solids (sludge).
Efficiency
It is often faster and more efficient at releasing nutrients compared to anaerobic, or waterlogged, conditions. The efficiency of this process is often monitored by measuring the carbon-to-nitrogen ratio, with lower ratios below 25:1 generally leading to faster and more complete mineralization.
Key Differences: Aerobic Mineralization vs. Traditional Fermentation
While traditionally “fermentation” implies an anaerobic (no oxygen) process, aerobic fermentation – often called aerobic mineralisation – uses oxygen to drive metabolic reactions that break down organic waste without producing methane.
Aerobic Mineralization/Fermentation
Uses oxygen, produces carbon dioxide and inorganic nutrients (high nutrient release), no methane.
Anaerobic Fermentation
Occurs in the absence of oxygen, results in intermediate organic compounds like alcohol or acids, and produces lower levels of available nutrients.