(considerations before choosing a compost
When deciding 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?
destruction 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
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
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
General cleanliness and systematic attention
to the details of operation around the compost
site, is necessary and particularly important
when contaminated material is used.