15th Feb 2023
Composting is essentially the breakdown of organic materials by bacteria. Typically, Aerobic (with air) is widely considered the best method by home composters.
But what happens when the process is interrupted at the start of the composting process and does it matter if this interruption is only temporary?
That’s what scientists from the Institute of School of Environment and Society, Tokyo Institute of Technology sought to discover in a recent study.
The researchers studied the effects of supplying nitrogen gas into the compost for 3 and 5 days in the early stages of composting and compared it to fully aerobic compost. They then introduced air into the composting until the end of the process.
The result? Organic matter decomposition was lower in the composts where nitrogen replaced air. The compost which had 3 days of nitrogen had 10% less decomposition, while the compost which had 5 days of nitrogen had 19% less organic material.
The scientists found the reason for this was down to the bacteria in the compost. A certain type of bacteria (Caldibacillus) that flourished during anaerobic composting inhibited the activity of aerobic bacteria even after the air had been introduced.
The enzymes bacteria produce are also key to breaking down organic materials. The scientists found that a key enzyme (Alpha-galactosidase) showed low activity when air was replaced with nitrogen. What’s more, this enzyme did not become significantly active until after composting was complete.
The study shows that oxygen in the early thermophilic stages of composting is key to producing high-quality compost with fully decomposed material. This can be challenging, as when compost heats up the oxygen demands of the bacteria are at their highest.
This highlights the importance of ensuring good aeration, whether that’s by turning compost, using bulking materials to create free air space, or other methods.