Introduction 5Figure 1.2 Energy consumption increases and changes in use pattern with human
advances in science and technology (Energy Information Administration 2004)
Organic wastes such as human excreta, wastewater and animal wastes, contain
energy which may be recovered by physical, chemical, and biological techniques,
and combinations of these. Incineration and pyrolysis of sewage sludge are
examples of physical and chemical methods of energy recovery from municipal
and agricultural solid wastes; however, these methods involve very high investment
and operation costs, which are not yet economically viable. The treatment and
recycling of organic wastes can be most effectively accomplished by biological
processes, employing the activities of microorganisms such as bacteria, algae,
fungi, and other higher life forms. The by-products of these biological processes
include compost fertilizer, biofuels, and protein biomass. Because the growth of
organisms (or the efficiency of organic waste treatment/recycling) is temperature-
dependent, areas having hot climates should be most favorable for implementation
of the waste recycling schemes. However, waste recycling is applicable to
temperate-zone areas also, with successful results from several projects (from
which many design criteria were derived) presented in this book.
It is therefore evident that technologies of waste management which are simple,
practical, and economical for use should be developed, and they should both
safeguard public health and reduce environmental pollution. With the current
energy crisis and since one of the greatest assets in tropical areas - where most
developing countries are located - is the production of natural resources, the
BTU (× 10^15 )
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