Substrate composition and moisture in composting source-separated human faeces and food waste

Area of Science:

• Environmental Science
• Microbiology
• Waste Management

Background:

• Faecal sludge and food waste are significant waste streams requiring safe disposal methods.
• Composting offers a sustainable approach to waste management, potentially reducing pathogen loads.

Purpose of the Study:

• To evaluate the thermophilic composting of faeces/ash and food waste mixtures.
• To determine the impact of insulation and substrate ratios on temperature profiles and pathogen reduction.

Main Methods:

• Composting experiments were conducted in 216 L reactors with varying faeces/ash to food waste ratios (1:0, 1:1, 1:3).
• Reactors were either insulated (75 mm styrofoam) or not insulated.
• Temperature, Escherichia coli, total coliforms, and Enterococcus spp. were monitored.

Main Results:

• Insulated reactors with faeces/ash alone reached >50°C for up to 12 days; food waste inclusion extended this period.
• Temperatures above 50°C for at least six days eliminated E. coli and total coliforms.
• Enterococcus spp. required >50°C for at least two weeks for complete reduction.

Conclusions:

• Insulated composting of faeces/ash and food waste effectively achieves thermophilic conditions for pathogen inactivation.
• A minimum of two weeks at >50°C, coupled with mixing, is crucial for sanitization, particularly for Enterococcus spp.
• Managing substrate moisture is critical for successful composting, especially in initial stages.