CHAPTER VIII. COMPOSTING
In economically developing countries, constraints related to economics, technology, and qualified
personnel have narrowed the choice of acceptable solid waste management, treatment, and
disposal options. Viable options include minimization, recycling, composting, incineration, and
sanitary landfilling. Composting is the option that, with fewexceptions, best fits within the
limited resources available in developing countries. A characteristic that renders composting
especially suitable is its adaptability to a broad range of situations, due in part to the flexibility of
its requirements. As a result, there is a composting system for nearly every situation; i.e. (this is to say), simple
systems for early stages of industrialdevelopment to relatively complex, mechanised systems for
advanced industrial development.
The compost option affords the many advantages of biological systems: lower equipment and
operating costs; in harmony with the environment; and results in a useful product. On the other
hand, composting is sometimes attributed with disadvantages often associated with biological
systems -- namely, a slowreaction rate and some unpredictability. Regarding the attributed
disadvantages, slow reaction rate may be justified, in that retention times are in terms of weeks
and months. However, the attribution of unpredictability is not justified. If all conditions are
known, applied, and maintained, the course of a given process will be predictable.
Among the major prerequisites for successfulcomposting are a satisfactory understanding and
application of the basic principles of the process. Without this understanding, inadequacies of
design and operation are practically inevitable. An understanding of the biology rests upon a
knowledge of the basic principles of the process. Such a knowledge enables a rational evaluation
of individual compost technologies and utilization ofthose technologies. An obvious benefit of
the knowledge is the ability to select the system most suited to an intended undertaking. An
accompanying benefit is the ability to critically evaluate claims made on behalf of candidate
Two definitions of composting are presented. The first is a definition in the strict sense of the
term, which differentiates compostingfrom all other forms of decomposition. The second one is
an ecological definition.
B1. DEFINITION in the strict sense
A definition that distinguishes composting from other biological processes is:
“Composting is the biological decomposition of biodegradable solid waste under controlled
predominantly aerobic conditions to a state that is sufficiently stable for nuisance-free
storageand handling and is satisfactorily matured for safe use in agriculture”.
The terms and phrases that collectively differentiate composting from other decomposition
processes are: “biological decomposition”, “biodegradable”, “under controlled predominantly
aerobic conditions”, “sufficiently stable”, and “matured”. The phrase “biological decomposition”
implies that the decomposition isaccomplished by living organisms. “Biodegradable” refers to
the substrate and it requires that the substance be susceptible to decomposition attack by certain
living organisms, e.g., bacteria and fungi. Such substances are organic compounds formed either
by living organisms or by way por medio de sinstesis quimica of chemical synthesis (e.g., halogenated hydrocarbons).
Decomposition of syntheticorganics generally involves the activity of certain microorganisms
under special conditions. The phrase “under controlled predominantly aerobic conditions” has a
twofold significance: 1) it differentiates composting from the random biological decomposition
that takes place in nature (e.g., open dump, forest, field, etc.); and 2) it distinguishes composting
from anaerobic digestion...
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