Agriculture Reference
In-Depth Information
ed with rapid urbanization caused by rural to urban migration overstretching re-
sources and problems of dysfunctional solid waste management facilities and ser-
vices (Yhdego
1995
). MSW constitute one of the most crucial public health and
environmental problems in African cities (Achankeng
2003
; Rotich et al.
2006
),
putting municipalities and local governments under heavy pressure to find sustain-
able and cost-effective waste management policies to the urban waste problem
without compromising environmental goals (Yhdego
1995
; Diaz et al.
2007
).
Municipalities generate huge quantities of wastes, with the average per-capita
residential waste generation (in kg/day) from about 0.51 to 1.45; waste is gener-
ated everywhere from small houses to large industries. The main sources of wastes
in sub-Saharan Africa are households, markets, institutions, streets, public areas,
commercial areas and manufacturing industries; the rate of waste generation is high
since the population and use of resources are higher in urban areas; urban resi-
dents generate two to three times more solid waste than their fellow rural citizens
(Couth and Trois
2010
). MSW undergoes a life cycle with generation, collection,
transformation, and disposal as the main steps. The efficient execution of each of
these stages requires taking many decisions at the strategic, tactical, and operational
levels (Henry et al.
2006
). The most common methods used for MSW management
include landfilling, incineration, composting, recycling, mechanical-biological
treatment, and waste-to-energy. The disposal of MSW in sanitary landfills is still
the main waste management method applied by municipalities in sub-Saharan Af-
rica. Landfilling has many negative impacts since it causes a profound strain on the
environment, e.g., contamination of ground water resources, organic and inorganic
pollution of nearby lakes and rivers, the carbon dioxide and methane (with high
global warming potential) release from incineration plants, contributing to global
warming (Couth and Trois
2012
). Disposal of waste in landfills is reported to con-
tribute to global GHG emissions approximately by 4 % (Bogner et al.
2004
,
2008
).
GHG emissions per person from urban waste management activities are greater
in sub-Saharan African countries than in other developing countries, and are con-
stantly increasing since the populations are more and more urbanized (Couth and
Trois
2011
).
Methane (CH
4
) gas generated through landfilling is 21 times more potent as
a GHG than the natural carbon dioxide (CO
2
) produced through composting the
biogenic wastes (Seng et al.
2013
). Since, global warming is more and more be-
coming important environmental issue, alternatives methods that are ecological
and environmental sound have to be promoted. A much more efficient and cost
effective way to control GHG emissions from waste is to stabilize the waste via
composting and to use the composted material as a soil improver/organic fertilizer
or as a component of growing media; compost that could be supplement with oth-
er ecological material (e.g., wood ash) when dealing with acidic soils (Bougnom
et al.
2009
,
2010
,
2011
).
Intensification of UPA in the tropics aiming at satisfying the increasing food
demand requires large amounts of inputs. Urban farmers in the tropics are gener-
ally subsistence farmers and cannot cope with the higher cost of agrochemicals
