116 Organic waste recycling: technology and management
the compost pile is structurally stable, but they can remain there for a longer
period. An experiment conducted at the Asian Institute of Technology (AIT),
Bangkok, Thailand, found the time required for compost stabilization to be
about 60 days (Polprasert et al. 1980), and the composted product was suitable
for use as soil conditioner. In China, more than 90% kill of Ascaris ova in the
compost was achieved (McGarry and Stainforth 1978).
Figure 3.11 Chinese composting pile (McGarry and Stainforth 1978; reproduced by
permission of the International Development Research Centre, Canada)
Windrow composting
This system involves periodic turning of the compost piles, manually about once
a week, or mechanically once (or more) daily. The purpose of pile turning is to
provide aeration and mix the compost materials, hence, a faster decomposition
rate than that of the Chinese ground-surface aerobic composting. The
approximate size of each pile is 15 x 3 x 1.5 m (length x width x height), but
other sizes, subject to convenience, have been employed. The period required
for compost stabilization varies according to the frequency of pile turning, being
20 - 40 days, and temperatures over 65°C in the center of the compost pile can
be reached.