Trial Results
The NBT trial provides compelling evidence that oxygenated water can enhance composting by speeding up decomposition and reducing odour.
Composting is an aerobic process driven by microorganisms that require oxygen to break down organic matter into stable, nutrient-rich compost.
Oxygen is critical for maintaining aerobic conditions, as low oxygen levels lead to anaerobic decomposition, which is slower and produces foul odours like hydrogen sulphide (rotten eggs) and volatile organic compounds (VOCs).
NBT’s trial demonstrates that oxygenated water—water with elevated dissolved oxygen (DO) levels—can enhance this process by improving oxygen availability, thereby boosting microbial activity and mitigating odour.
Following is a detailed exploration of the benefits, focusing on composting speed and odour reduction, as observed in the trial.
1. Increased Composting Speed
The trial showed a minimum 33.5% increase in the speed of composting when using oxygenated water (DO ~30 ppm) compared to the control (normal water, DO 7.8 ppm).
This can be attributed to the following mechanisms:
Enhanced Microbial Activity
Aerobic bacteria, such as mesophiles and thermophiles, thrive in oxygen-rich environments.
Oxygenated water increases the DO in the compost’s aqueous films, where microbes live, enabling faster metabolism of organic matter.
In the trial, Samples 2 and 3 (oxygenated water) reached higher temperatures (up to 43°C) than the control (max 37°C), indicating greater microbial activity, as heat is a by-product of bio-oxidation.
Improved Oxygen Penetration
Compost piles often develop anaerobic zones due to limited oxygen diffusion, especially in wet or compacted areas.
Oxygenated water delivers oxygen directly to these zones via the liquid phase, reducing the distance oxygen must diffuse through water films.
This is particularly effective in maintaining aerobic conditions in the pile’s core, where oxygen is often limited.
NBT’s trial’s daily spraying oxygenated water ensured consistent oxygen supply, accelerating decomposition.
Temperature Dynamics
The temperature data from NBT’s trial shows that oxygenated water samples (2 and 3) sustained higher temperatures (e.g., 43°C on June 19 for Sample 2) for longer than the control, suggesting a more robust thermophilic phase, which is critical for rapid organic matter breakdown.
The thermophilic phase (45–65°C) is driven by heat-loving bacteria that consume bioavailable volatile solids (BVS), and oxygenated water likely supported their activity by preventing oxygen depletion.
Reduced Need for Bacterial Additives
Sample 3 (oxygenated water without bacteria) performed comparably to Sample 2 (oxygenated water with bacteria), suggesting that oxygenated water alone can enhance composting speed without costly microbial additives.
This is likely because the elevated DO levels supported the native microbial population, reducing reliance on external agents.
2. Odour Reduction
The trial reported an average 50% reduction in odour across the composting process, with Sample 3 (oxygenated water, no bacteria) showing the greatest reduction (from 8.5 to 0 by June 22).
This aligns with composting science, as odour is primarily caused by anaerobic conditions.
The benefits of oxygenated water for odour control include:
Prevention of Anaerobic Odours:
Anaerobic decomposition produces malodorous compounds like hydrogen sulphide (H2S), volatile fatty acids, and amines.
By increasing DO levels, oxygenated water maintains aerobic conditions, preventing the formation of these compounds.
NBT’s trial’s olfactory tests showed a significant drop in odour scores for oxygenated water samples (e.g., Sample 3: 8.5 to 0), compared to the control (8.5 to 2).
Enhanced Bio-oxidation of VOCs:
Volatile organic compounds (VOCs), which contribute to odour, are more readily bio-oxidized by aerobic microbes when oxygen is abundant.
Oxygenated water increases DO in the compost’s liquid films, allowing microbes to degrade VOCs into less odorous compounds like CO2 and water.
This is supported by research indicating that higher DO levels at cooler temperatures promote VOC dissolution and microbial degradation, reducing odour intensity.
Reduced Need for Expensive Odour Control:
Oxygenated water offers a cost-effective alternative by addressing the root cause of odours (anaerobic conditions) rather than masking them.
pH and Chemical Interactions:
While the trial didn’t measure pH, research suggests that aerobic conditions supported by oxygenated water can stabilize pH, reducing ammonia (NH3) volatilisation, which contributes to odour.
Anaerobic conditions often lead to ammonia release at high pH, but oxygenated water promotes NH3 oxidation, conserving nitrogen and reducing odour
3. Additional Benefits and Considerations
Beyond speed and odour, oxygenated water may offer other advantages:
Moisture Management:
Compost requires moisture (45–70% by weight, like a wrung-out sponge) for microbial activity, but excess moisture can fill pores and create anaerobic zones.
NBT’s trial’s controlled application of oxygenated water daily likely maintained optimal moisture while delivering oxygen, avoiding the pitfalls of over-wetting
Environmental Impact:
Aerobic composting with oxygenated water reduces methane emissions, a potent greenhouse gas produced under anaerobic conditions.
This aligns with sustainable waste management goals, as methane has 28 times the warming potential of CO2