• In the composting process, aerobic microorganisms use organic matter as a substrate.

• Aerobic bacteria, which require oxygen to survive, produce mostly carbon dioxide which is essentially odourless.

• Aerobic microorganisms, while the oxygen lasts, degrade organic materials into carbon dioxide (CO2), water, partially degraded residual organics, and heat.

• Composting differs significantly from the decay process that occurs in nature; it is monitored and controlled, aerobic conditions are maintained, and it includes a high-temperature phase (e.g., above 55 degrees Celsius [°C]) that reduces or eliminates pathogens and weed seeds.

• The fate of virtually all municipal organic waste is bacterial digestion, either in highly anaerobic conditions (as in a landfill) or in predominately aerobic conditions (as in compost facility).

• Initially, bacterial decomposition occurs under aerobic conditions because a certain amount of air is trapped within the landfill.