I was reading about the dangers of introducing pathogens in a compost pile. As you know, some moulds can be toxic. So I am curious if the normal household mould that appears in the kitchen or the refridgerator is something I should be concerned about.
Moulds help break down organic matter. They are part of a good compost heap and there is no reason why food with moulds cannot be placed on your heap. However, your heap can become too mouldy but that is usually the result of the heap being too wet and/or containing to much nitrogen. It is true that moulds can be toxic, so you should not let your pets eat any compost heap material.
Once the decomposition process is done, the moulds will be gone and the risk of pathogens is very small. This is due to a number of things:
- during the composting process the temperature in the heap rises, killing most of the pathogens
- other micro-organisms will kill and eat pathogens
- in time the pathogens will die by natural causes
To reduce the risk of pathogens even further you can:
- make sure you have the correct C:N balance, the correct moisture balance and enough air in your heap. This is all to ensure the heap reaches a good temperature.
- turn and mix your heap regularly so stuff on the edges of the heap (where it is less warm) are also heated.
- don't throw cat and dog feces on the heap (see also this answer)
The concern about adding pathogens to a compost pile mostly overstated. The normal biological action of composting reduces but does not eliminate pathogens in the compost, and the fact is that a lot of things which we compost are potentially hazardous foods. I suppose if you want to be particularly paranoid you could avoid throwing things like cooked veggies into the compost heap. Aside from very high pathogen sources (like manure), composting is believed to cause great reduction in pathogen concentration, to safe levels.
See Pathogens and Public Health Concerns with Composting by Chris Cronin (PDF, via Vermont Waste Management Division).