conditions, during which the organic materials undergo a thermophilic stage, which
allows for the sanitation of the materials (Mupambwa et al. 2015). The end product
of traditional composting is a stabilized and well-humified compost with a high
fertilizer value relative to the unprocessed animal manures, with no pathogens.
However, a major disadvantage of mineralizing farmyard animal manures through
composting is the loss of nitrogen through volatilization of ammonia during the
thermophilic stage. It is also important to indicate that the chemical composition of
the original materials used for composts influences the quality of the final nutritional
composition of the organic fertilizer; hence, researchers have reported wide variations in terms of the fertilizer values of farmyard manure composts (Mupambwa
2015; Sinha et al. 2010; Theunissen et al. 2010).
Apart from the animal manures indicated above, other important animal-related
sources of organic nutrients include bone meal, bird guano and blood meal. Bone
meal is a product from animal meat processing and is finely ground bone mixed with
slaughterhouse waste products and has been reported to be rich in organic matter,
nitrogen, phosphorus and calcium (Jeng et al. 2006). Meanwhile, guano which is of
bird or bat origin is made up of deposits consisting of excrements, eggshells and
carcasses of dead bird and bats. Guano has been reported to be a very high source of
the essential macro-elements nitrogen, phosphorus and potassium (Schnug et al.
2018). Lastly, blood meal, which is dried and powdered blood collected from animal
slaughterhouses is an excellent source of organic nitrogen due to its the high protein
composition.
18.3.2 Urban or Municipal Waste and Sewage Sludge
Urban wastes and sewage sludge are all waste products resulting from the increase in
world population, urbanization and industrial activities. Due to the increase in these
municipal wastes and sewage sludge, options such as incineration, pyrolysis and
direct soil applications have been evaluated (Ayuso et al. 1996). Application of the
composted municipal wastes presents an interesting option for the sustainable
management and use of these wastes though the major challenge is that it could
lead to the accumulation of phytotoxic levels of heavy metals in soils (Hemmata
et al. 2010). The interest of using municipal wastes and sewage sludge has been
driven by their high content of organic matter, essential macronutrients and other
micronutrients required for plant growth (Mdolo 2016). However, the presence of
potentially toxic heavy metals and pathogens in these wastes has seen their strict
regulation when used in organic soil fertility management as the heavy metals taken
up by the plants can easily bioaccumulate in other organisms higher up in the trophic
levels. This has seen the use of municipal wastes and sewage sludge being strongly
regulated by different bodies in many countries (Mdolo 2016; Alvarenga et al.
2015).
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allows for the sanitation of the materials (Mupambwa et al. 2015). The end product
of traditional composting is a stabilized and well-humified compost with a high
fertilizer value relative to the unprocessed animal manures, with no pathogens.
However, a major disadvantage of mineralizing farmyard animal manures through
composting is the loss of nitrogen through volatilization of ammonia during the
thermophilic stage. It is also important to indicate that the chemical composition of
the original materials used for composts influences the quality of the final nutritional
composition of the organic fertilizer; hence, researchers have reported wide variations in terms of the fertilizer values of farmyard manure composts (Mupambwa
2015; Sinha et al. 2010; Theunissen et al. 2010).
Apart from the animal manures indicated above, other important animal-related
sources of organic nutrients include bone meal, bird guano and blood meal. Bone
meal is a product from animal meat processing and is finely ground bone mixed with
slaughterhouse waste products and has been reported to be rich in organic matter,
nitrogen, phosphorus and calcium (Jeng et al. 2006). Meanwhile, guano which is of
bird or bat origin is made up of deposits consisting of excrements, eggshells and
carcasses of dead bird and bats. Guano has been reported to be a very high source of
the essential macro-elements nitrogen, phosphorus and potassium (Schnug et al.
2018). Lastly, blood meal, which is dried and powdered blood collected from animal
slaughterhouses is an excellent source of organic nitrogen due to its the high protein
composition.
18.3.2 Urban or Municipal Waste and Sewage Sludge
Urban wastes and sewage sludge are all waste products resulting from the increase in
world population, urbanization and industrial activities. Due to the increase in these
municipal wastes and sewage sludge, options such as incineration, pyrolysis and
direct soil applications have been evaluated (Ayuso et al. 1996). Application of the
composted municipal wastes presents an interesting option for the sustainable
management and use of these wastes though the major challenge is that it could
lead to the accumulation of phytotoxic levels of heavy metals in soils (Hemmata
et al. 2010). The interest of using municipal wastes and sewage sludge has been
driven by their high content of organic matter, essential macronutrients and other
micronutrients required for plant growth (Mdolo 2016). However, the presence of
potentially toxic heavy metals and pathogens in these wastes has seen their strict
regulation when used in organic soil fertility management as the heavy metals taken
up by the plants can easily bioaccumulate in other organisms higher up in the trophic
levels. This has seen the use of municipal wastes and sewage sludge being strongly
regulated by different bodies in many countries (Mdolo 2016; Alvarenga et al.
2015).
304
H. A. Mupambwa et al.