Composting as A Sustainable Waste Management Technique in Developing Countries
Adewale M. Taiwo
Attaining sustainability in waste management requires an option that employs environmental friendliness. Such a technique must be effective, efficient and less costly than many options. Solid waste management is an enormous task in developing nations all over the globe due to factors like poverty, population explosion, urbanization and lack of proper funding by the government. Disposal methods such as incinerator, landfill, pyrolysis and gasification are efficient but have negative impacts on the environment as well as threat to public health. Composting when properly handled is sustainable with various advantages such as production of biofertlizer, relatively low air and water pollution, low operational cost and income generation. The use of composting for bioremediation of contaminated soil has gained much ground in many developed countries of the world. However, composting when improperly designed could lead to methane production, odour emission and heavy metals build-up in the final product. Therefore, this study reviewed sustainability of composting and its numerous advantages over other waste disposal options in developing countries.
February 02, 2010; Accepted: May 09, 2010;
Published: August 21, 2010
Solid waste management is the second most important problem after the water
quality in developing countries all over the world (Senkoro,
2003). Most of the populace lack access to proper and routine removal of
garbage (Awomeso et al., 2010). According to
UNEP (2002) and Doan (1998), disposal
of solid wastes is a major issue of concern in less-developed nations due to
population explosion, poverty and high urbanization rates combined with ineffective
and under-funding by government to proffer efficient management of waste.
Factors such as waste composition, technologies and lack of infrastructure
have been found to set apart the good management of solid waste in developing
nations (Cointreau, 1982; Daskalopoulos
et al., 1998; UNESCO, 2003). Collection and
disposal of waste differ from nation to nation and from community to community.
For instance, in USA, the methods of disposal are landfill (true disposal) and
incineration. In developing nations like Nigeria, the only feasible method of
disposal is open landfills, which are set on fire seasonally. The resultant
effect of this action is air pollution as well as leachate production (El-Fadel
et al., 1997).
Municipal solid waste can be defined as non-air and sewage emission created
within and disposed of by a municipality (local government), including household
garbage, commercial refuse, construction and demolition debris, dead animals
and abandoned vehicles (Cointreau, 1982). USEPA
(2003) observed that the majority of substances that are municipal solid
waste include: paper, vegetable matter, plastics, metals, textiles, rubber and
The wastes generated in communities are the reflection of their ways of life,
wealth and culture (UNCHS, 1989). In developing nations
certain medical and hazardous wastes streamed into municipal solid waste and
may pose health risks to waste handlers and the general public. Waste generation
in developing countries has average 0.4-0.6 kg/person/day against 0.7-1.8 kg/person/day
in developed countries (Cointreau, 1982). Blight
and Mbande (1996) observed that high density, large amount of organic content,
small sized particles and large amount of dust and dirt characterize wastes
generated in developing countries.
Composting is a biological process whereby regular introduction of air by mechanical
turning stimulates aerobic microorganism to reduce organic materials such as
manure to a more stable materials similar to humus (Rynk,
1992). It is a suitable way of recycling organic wastes in an environmentally
friendly manner. As a result of the types, nature and compositions of waste
in developing countries, composting remains the most economical and efficient
management technique among other management options. In Nigeria, organic manure
resources are no longer explored to its fullness (Sridhar
and Adeoye, 1995) due to petroleum resources, which has slaughtered
the agricultural sector of the economy. In a country of over 140 million people,
only four composting plants are functional: The pacesetters organic fertilizer
plant at Bodija, Ibadan (Oyo state); Ayeye community organic fertilizer plant
(Oyo state); a food waste composting plant at Forcadoes, Warri (Delta state)
and Lagos state compost plant, Ikorodu (Lagos state). The aim of this study
is to highlight sustainable advantages of composting over other solid waste
WASTE MANAGEMENT TECHNIQUES
Waste management is the collection, transportation, processing, treatment,
recycling or disposal of waste materials to reduce their adverse effects on
human health or amenities (www.wastewikipedia).
Waste can be liquid, gas, or a solid substance and it is an unwanted material
the owner is about to discard or has discarded. The management of waste in developing
countries differs greatly from what is done in advanced communities and also
from urban to rural and from residential to industrial settings. In developing
country like Nigeria, there are less of metal and plastic wastes compared to
high organic wastes (Cointreau, 1982). Problem of waste
management in developing countries include: less effective garbage trucks, low
technology and unplanned and haphazardly constructed sprawling slums with narrow
roads (Cointreau, 1982). Political and economic framework
is another major problem of waste management in developing countries. Non-hazardous
residential and institutional waste is the responsibility of local government
authorities in Nigeria. But the unholy sights of refuse, dirts, wastes, loitering
our streets, highways and neighborhood a confirmation of inefficiency on part
of the local government; even though they claimed responsibility of spending
huge amount of money on waste related issues.
Table 1 shows the percentage of waste compositions in all
the continents of the world. Food wastes carried the highest percentage followed
by paper-cardboard and wood, respectively. The type of waste management techniques
that should be applied for proper management of waste depend on the composition
Although, composting will be appropriate for all organic wastes: wastes such
as plastic, metals and glasses are better handled through recycling.
Waste management techniques take place in many ways viz., landfill, incineration, pyrolysis and gasification, composting and anaerobic digestion.
Landfilling: Landfilling is an economical method of wastes disposal
in developing countries involving pitching refuses into a depression, abandoned,
mining void, excavated land, or borrowed pits (Daskalopoulos
et al., 1998). It is the most traditional way of true waste disposal
practiced in many countries. The following are various forms of landfills:
Open-dump system/ordinary landfill: This disposal of waste materials is in pits, excavated lands, canals, sloping landscapes or flat surface without covering the waste. From time to time, open dumps burn leading to air pollution. Other environmental implications of landfill are the sites eyesore, windblow of litters along the landscape, presence of faecal matters, intrusion of vermin such as mice and rats, odor, smoke with resultant effects on human health and breeding ground for disease vectors (cockroaches, flies and mosquitoes).
Sanitary landfill: This engineering means of disposing solid wastes
uses thin layers, compacted into the smallest practical volume and cover with
inert ash at the end of each working day. Environmental effects of sanitary
landfill are production of Landfill Gases (LFGs), leachates and leaving heavy
metals. LFGs are produced when methanogens are decomposed primarily into methane
(CH4) and carbon dioxide (CO2) and other gases such as
carbon monoxide (CO), nitrogen (N2), alcohols, hydrocarbons and organo-sulfur
compounds (El-Fadel et al., 1997). CH4
and CO2 are green house-gases (Seo et al.,
2004; Johannessen, 1999). Leachate production is
a phenomenon in sanitary landfill and is one of the major problems unless a
collection system is designed. Leachate could contain high levels of nutrients
(nitrogen, phosphorus and potassium), heavy metals and toxins like cyanide and
dissolved organics (El-Fadel et al., 1997). Leachates
may infilterate into groundwater resource and pollute it thereby leading to
public health problems (Adekunle et al., 2007;
Orebiyi et al., 2010). Heavy metals in plants
and animals could be deleterious to health. Other potential problems of sanitary
landfill are high cost of designing, loss of biodiversity and impact on landscape.
Secured landfill: This landfill is constructed mainly for hazardous wastes disposal such as hospital and radoiactice wastes. If it is not designed properly, the resultant effect could be similar to that of a sanitary landfill.
Incineration: Incineration refers to high temperature combustion of
waste in a high-efficiency furnace to produce steam and ash (EPA,
1995). The benefits of incineration are a major reduction in waste volume
and production of energy in form of electricity and heat production (Seo
et al., 2004). However, the problems of waste incineration cannot
be overemphasized in the light of the following: construction and start up costs
of facilities, which could be too expensive for developing countries (Rand
et al., 2000); acid gases production (sulphur oxide (SOx),
hydrochloric acid (HCl), nitrogen oxide (NOx)); ash management; non-combustible
waste such as metals and toxicants like metals ((lead (Pb), mercury (Hg)), organics
(dioxin, polychlorinated biphenyl), CO and dust (UNEP, 1996).
Pyrolysis and gasification: These are methods for managing wastes by
heating under controlled conditions to produce low to medium heating fuel gases,
tars, char and ash; under a high temperature with limited oxygen (Heimlich
et al., 2005). Usually, the process takes place in a sealed vessel
under a high pressure. Whereas pyrolysis converts the solid wastes into solid,
liquid and gas products, gasification converts organic materials into a syngas
(CO and H2). In Nigeria, pyrolysis is used to convert wood to charcoal
that is used for domestic cooking. The effect of pyrolysis to the environment
is loss of biodiversity, desertification and emission of acid and green-house
gases. Generally, the use of pyrolysis and gasification for waste management
is uncommon in developing countries because of the expense of equipment. Another
reason why pyrolysis and gasification may not be sustainable is the emission
of green house gases during thermal treatment.
Composting and anaerobic digestion: Composting is a controlled method
of using microbial organisms to decompose the organic fraction of solid waste
(Seo et al., 2004). Solid wastes in developing
countries are composed of over 50% organic materials (Hoornweg
et al., 1999). Incineration of such waste is a waste of time whereas
disposal in landfill will be a waste of resources. The only viable option to
sustainably manage wastes in developing nations is composting because of the
following advantages: lower operational cost (Airan and
Bell, 1980), decreased water pollution, lessened environmental pollution
and beneficial use of end products (Poincelot, 1974).
Cointreau (1982) found that in developing nations such
as Indonesia, Colombo and Sri Lanka, residential wastes are 78, 81 and 89% compostable,
respectively. Waste compositions in different countries of the world are depicted
in Table 1. Sustainable waste management should be employed
to maximize wastes generation while maximizing the ability to reuse and recycle.
In composting, a strategy of sustainable waste management is recycling of organic
wastes to a useful and valuable end point. Composting as a waste management
option has little record of operation in Africa, Latin America and in places
where most of the facilities failed worldwide (UNEP, 1996).
The failures were attributed to lack of understanding and maintaining biological
conditions, high cost of mechanization, higher economic cost, poor presorting
of incoming wastes and failure to understand market condition (Hoornweg
et al., 1999).
In Nigeria and in other developing countries most of the composting plants
have failed. For instance, nine out of eleven plants have been closed in India
and eighteen out fifty-four facilities failed in Brazil between 1974 and 1996
(UNEP, 1996; Hoornweg, 1999).
Composting has been used effectively to remediate soils and sediment with hydrocarbons
(Williams and Keehan, 1993). Beaudin
et al. (1996) found that 73% PAH was degraded by composting. Barker
(1997) and Chaney et al. (2001) reported that
explosive-contaminated soil, toxic organic compounds, metals in organic residues,
wastes and by-products were remediated successfully through composting. The
use of composting accelerates destruction of contaminants (Briggs
et al., 1998). However, problems like heavy metal accumulation and
health hazards related to pathogen (Anid, 1986) cannot
be found wanting in this method despite the numerous advantages. These problems
can be circumvented through proper wastes sorting at the source, addition of
lime (reduces heavy metals availability) and proper compost maturity (Petruzzelli,
1989; Ciavatta et al., 1993).
INTEGRATED WASTE MANAGEMENT
Arowolo and Sridhar (2005) defined Integrated Waste
Management (IWM) as the selection and application of techniques technologies
and management programmes to achieve specific wastes management objectives and
goals. IWM can also be defined simply as the combination of all the waste management
techniques in order to minimize waste generation. The waste hierarchyin IWM
includes reduction, reuse, recycling, incineration and landfill (Fig.
The list starts with reduction meaning using less and re-using more in order
to safe materials production, resource cost and energy. At the bottom of the
list lies the ultimate disposal, which is the final resting place of wastes.
Waste recycling through collection, scavenging and processing with a high proportion of reuse is an efficient IWM. However, there is need to create markets and market incentives to encourage scavenging, recycling and composting. A reduction strategy is to lower the amount of wastes being produced, e.g., through surcharge of excess bags, containers, or household refuse in order to save energy, conserve resources and reduce waste stream volume.
A reuse strategy is to encourage the use of a product more than once either
for the same purpose or for alternative purpose i.e., through donation to charity
and reusing packaging. The third is material recovery, which has to do with
composting and recycling. It entails reprocessing of waste material into either
same form as the original or into other different products (Heimlich
et al., 2005). The fourth is resource recovery, which has to do with
incineration of waste and the use of heat for energy. Material recovery when
combined with energy recovery often extends the lifespan of incineration. The
ultimate disposal is the last option in IWM in which residuals from other processes
and material that cant be recoverable are disposed off in landfills.
Since, municipal solid wastes in developing countries have a large portion
of organic materials (Awomeso et al., 2010),
composting could be seen as best sustainable option that would reduce waste
volume. Notwithstanding, it is just a subset in IWM, which encompasses other
waste management techniques. Scavenging of landfills and open dumps, a common
phenomenon, helps in salvaging materials that could be sold in the recycling
market. According to Kasseva and Mbulgwe (2000), there
is a high demand for scavenging materials.
No single approach can apply completely to waste management due to waste and community diversity. Therefore, every waste management technique must be utilized fully in an environmentally sustainable manner. Composting in this case is sustainable and environmentally friendly and a viable technique.
COMPOSTING BIOREMEDIATION TECHNOLOGY
Composting has been used widely for remediation of organic contaminants as
it accelerates destruction of contaminants (Buyuksonmez
et al., 1999; Williams and Keehan, 1993; Rao
et al., 1995). With proper aeration, water, C:N ratio and duration,
composting can degraded various organic compound present in feedlot (Sikora,
1998). Strom (1998) reported a decomposition of
organophosphate and carbamate pesticides during composting. However, organochlorine
insecticides are resistant to degradation (Buyuksonmez et
al., 1999). Organochlorine insecticides have been banned in most countries.
Degradation of pesticides during composting depends on the pesticide and the
substrate in which the pesticide is been co-composted along with (Barker and
Bryson, 2002). For instance, a wood containing Polynuclear Aromatic Hydrocarbon
(PAH) after composting for 61 days had PAH concentration greatly reduced. 1000
mg kg-1 of each PAH (phenanthrene and pyrene) was reduced to 26 mg
phenanthrene kg-1 and 83 mg pyrene kg-1 (Baker
and Bryson, 2002).
In the study of Raymond et al. (1997), paraffin
wax-coated corrugated cardboard decomposed well during composting. In a similar
manner, Williams and Keehan (1993) demonstrated a destruction
of explosives on composting (trinitrotoluene and nitrocellulose). Soil contaminated
with 212 mg kg-1 chlorophenols on composting recorded a level of
30 mg kg-1 within 48 weeks of composting (Valo
and Salkinoja-Salomen, 1986). Hydrocarbon contaminated soil had been degraded
on composting (Beaudin et al., 1996).
Apart from organic contaminants where composting had been used extensively
to bioremediate, composting bioremediation has also been demonstrated with inorganic
contaminants (Chaney and Ryan, 1993). According to Pare
et al. (1998, 1999), stabilized organic matter
forms complexes with metals, thereby inhibit their mobility and the availability
for plants sorption. However, composting may release metals from organic combination
through organometallic complexes degradation and increasing metals bioavailability
(Heyes et al., 1998). Addition of lime to compost
and increase in pH of compost could help reduce the availability of metals (Fang
and Wong, 1999; Petruzzelli, 1989; Ciavatta
et al., 1993).
COMPOSITIONS OF COMPOST
Compost compositions will determine its quality. Addition of compost should
not lead to soil pollution. According to World Bank (1997)
compost must be of high quality such that no leaching or heavy metal uptake
by plants can occur even under acidic soil conditions. Compost should be directed
to develop and maintain soil structure, improve physical properties of soil,
decrease soil-susceptibility to erosion, encouraging microbial activity as well
as providing potentially available plants nutrients (Hesse,
1998). Richard (1990) and Walker
and ODonnell (1991), reported that compost quality is a major factor
that could affect both societal acceptability and economic value of compost.
The composition of some selected composts in various developed nations of the
world is presented in Table 2.
The recommended C:N ratio of a good compost is between 25:1 and 40:1. Inappropriate
use of wastes with high C:N ratio can lead to reduced soil fertility (Harris
et al., 2001).
ENVIRONMENTAL BENEFIT OF COMPOSTING
A properly managed compost operation promotes clean and readily marketable
finished products, minimizes nuisance potential and is simple to operate (World
Bank, 1996). There is a reduction in landfill space where composting is
operated as waste management technique (He et al.,
1992, Awomeso et al., 2010). There is also
a reduced surface and groundwater contamination, which is a phenomenon in landfill.
According to WHO, 900 million people experience diarrhea or contact diseases
such as typhoid and cholera through contaminated water (WHO,
2008). Through composting waste blocking of rivers, canals, drainages could
be reduced (World Bank, 1996). As a flexible waste management,
composting enhances recycling of materials, low transportation cost. In composting
there is a minimal emission of greenhouse gases with subsequent effect on climate
change and global warming (Seo et al., 2004).
Moreover, addition of compost to soil reduces soil erosion as well as improvement
of soils structure, aeration and water retention. The use of chemical
fertilizer could lead to groundwater pollution. But the use of compost discourages
this water pollution.
CONCLUSION AND RECOMMENDATION
From this review, composting could be been as an option of waste management operation that is cheap, environmental friendly, wealth creating and sustainable. The technique has been used extensively for bioremediation of polluted soils and sites. However, composting requires proper handling and appropriate technology for its sustainability.
It is in this light that I will recommend that composting of organic wastes should be encouraged in all the developing nations of the world by the appropriate waste management authorities. This action will lead to waste reduction at landfill, job creation and production of organically produced food crops. Organic agriculture has continued to gain more ground all over the world for its sustainability and safety of the farm produce. The crops produced from this organic agriculture are expensive. But with the encouragement of compost fertilizer at high rate and low price to the farmers, the price of organic food could drop drastically.
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