before choosing a compost method)
how to compost, there are many considerations. How much time and
effort do you want to spend? Do you want your compost
within months, or do you have space for a slow pile that you can
leave for a year? What types of materials will you be composing?
Will they possibly have pathogens and weeds, or will you only compost “safe” materials?
Do you want to spend lots of money for a fancy bin, or will a heap,
or bin made out of free pallets suffice?
of pathogenic organisms
Destruction of pathogenic organisms is a most important aspect-and
a problem- of compost. Experiments have shown that aerobic composting
at high temperatures is effective in destroying pathogenic organisms.
The absence of health hazards is characteristic of well-managed
composting operations. This is significant evidence of the effectiveness
of thermophilic composting.
An analysis of the typical temperature and of thermal death points
of a number of pathogenic microorganisms, parasites, and parasite
ova, indicates the unlikelihood of survival of some of the common
disease-bearing organisms. The highest thermal death points are appreciably
lower than the maximum temperatures found inside the composting pile
or bin. The magnitude and duration of the high temperatures, as well
as the antibiosis which is characteristic of a mixed population of
microorganisms, provide a sound basis for believing that no pathogens,
parasites, or parasite ova survive the aerobic composting process.
The high temperature zone usually extends only to within 4 to 8
inches of the surface. Therefore, turning is necessary, quite apart
from its function in aerating the mass, for ensuring pathogen and
parasite destruction, particularly if a composting period under six
months is used. The compost temperature curves and thermal-death-point
values may indicate that one turning will be sufficient eliminate
the pathogens and parasites if all of the surface material is completely
turned to the inside, thus exposing any organisms present to lethal
internal temperatures. But, although this may be true in many cases,
as a safety factor, and to guard against failure to turn all of the
material to the inside, at least two turns are required, and at least
three for maximum assurance of complete destruction. Three turns
would also be the normal practice for aeration purposes when rapid
composting is done in stacks or piles on the ground surface.
In some composting operations the material is turned only once or
not at all. A thermophilic temperature is developed after the initial
aerobic stacking. This is considered to be sufficient to destroy
pathogens and parasites. Unless composting was under a thermal cover,
or in vessel, it is doubtful this practice is sufficiently safe when
contaminated material is composted, since some pathogen and parasites
may escape destruction in the cooler side and top layers.
Anaerobic composting in the mesophilic temperature range does not
affect good destruction of parasites in an anaerobic environment.
The biological antagonisms will eventually eliminate them, but this
will generally take at least 6 months.
Unless six months or more can be allowed to elapse before the compost
is used, anaerobic composting should be preceded by aerobic conditions
and thermophilic temperatures for at least a week with at least one
turning, in order to ensure the desired destruction of pathogens.
General cleanliness and systematic attention to the details of operation
around the compost site, is necessary and particularly important
when contaminated material is used.