252 T.C. DAVIES, M.M. IKIARA, A.M. KARANJA, C. FUREDY
The most important problem experienced during storage and application of urban
organic waste is bad smell, as cited by almost all the respondents. Other important
problems mentioned included flies and cuts from sharp objects.
Trace element- and heavy metal content of urban organic solid waste
The soil has enormous capacity to absorb and transform waste by microbial activity
into usable nutrients for plant growth. However, the use of urban organic solid waste
has caused concern in recent years because of the possibility of soil contamination by
heavy metals and other trace elements. Analysis of samples of municipal compost by
Purves and Mackenzie (1973) indicated that they contained up to 100 times as much
copper and 300 times as much zinc and lead as uncontaminated, normal soils.
There is hardly any information on trace element and heavy metal composition of urban
organic solid wastes in Nairobi, but a number of studies in Hyderabad (e.g. Rao and
Shantaram, 1994) have shown that land application of organic waste increases the
concentrations of trace elements in soils. These studies have also reported on the concen-
trations and relative availability of heavy metals in urban solid wastes and the possible
implications of the addition of urban solid wastes to soil in relation to heavy metals.
These studies have shown that the long-term effects of such applications to land
should be constantly monitored, for although the removal of most heavy metals by
plants would be slow their accumulation may present a hazard in the long term.
Williams et al. (1980), Banin et al. (1981) and Emmerich et al. (1982) have all advo-
cated a cautions approach to repeated applications of urban solid wastes on land. It is
therefore important to assess the impact of long-term application of fresh garbage on
soil properties and trace metal concentrations in agricultural fields. Predicting poten-
tial hazards associated with land application of garbage is, however, sometimes diffi-
cult because of the inherent variability in the composition of wastes and the manures
obtained from them. It should be ensured that the land application of wastes does not
become an environmental hazard or cause fertility problems for the future (Rao and
Shantaram, 1994). Judicious management through proper selection of wastes, soils
and crops, and proper reliance on soil and plant testing can avoid most of the potential
problems associated with garbage application on land.
12.8. GENERAL PERCEPTIONS OF WASTE WORKERS
Most of the workers in the composting sector see economic gain as the principal benefit
that accrues from their work. They also acknowledge the contribution they make
towards the attainment of a cleaner environment and thus to the enhancement of envi-
ronmental quality. Composting groups have a clear vision of what they would like to see
in the future. Sixty percent of our respondents spoke of plans to expand their businesses
and increase their level of production, constructing more facilities and moving on to new