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PHYSICAL COMPOSITION AND ENERGY CONTENT APPROXIMATION OF SOLID

WASTE AT THE UNIVERSITY OF PORT HARCOURT, NIGERIA

MOMOH, O.L YUSUF*, ODONGHANRO BESIDONE** and DIEMUODEKE, E.O***

Department of Civil and Environmental Engineering,

University of Port Harcourt, Choba P.M.B. 5323, Port Harcourt,E-mail:[email protected]

E-mail:[email protected]

E-mail:[email protected]

+2348035386779*, +2348065458698** AND +2348056320209***

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ABSTRACT

The physical characterization of solid waste generated at the University of Port Harcourt, Rivers state,

Nigeria was carried out for the three campuses situated at the university. The quartering method was

used to physically quantify the various waste components. The solid waste types were observed to

comprise of plastic (38.33%), paper (23.33%), glass (4.8%), tin (3.2%), wood (1.9%), leather (1.2%),

yard waste (9.45%), textile (1.0%), food waste (11.03%) and ash/dirt (5.03%). The average moisture

content as-discarded, density and solid waste generation rate were observed to be 16.81%,

564.15kg/m3 and 0.55kg/capital/day respectively. However, there was no significant difference

amongst the waste type generated within the three campuses at 95% confidence interval when

analyzed with one-way analyses of variance. In order to understand the suitability of the solid waste

as a possible source of energy, an estimation of energy content was carried out. The energy content of

the solid waste was observed to be 18.43MJ/kg which is significant, hence, it can be used for energy

generation at the university campus.

Keywords: waste types, components, energy content, generation, mass–incineration.

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INTRODUCTION

It is well known that human activities create waste and these wastes must be properly handled

stored, collected, processed, and disposed of to reduce the risk they will pose to the general public.

The rate of solid waste generation has been on the increase due to increase in human population

(Cunninghams et al 2005; Zurbrugg, 2003; Sridhar and Ojediran, 1983). In developed countries,

proper waste management practices have lead to reduced environmental and health implication

associated with solid wastes, due to formation and implementation of sustainable policies designed to

protect human life’s and the environment in general. However, in developing countries the

consequence of improper solid waste management is overwhelming due to lack of proper policies to

manage solid waste problems. Solid wastes have been observed to block drains leading to episodes of

flooding (UNEP-1ETC 1996). Also, dump sites have become breeding grounds for insects, rodents

responsible for disease proliferation among the population (Kungskulniti, 1990; Lohani, 1984). This

poor management practice in developing countries persist despites the enormous benefits that could

be derived from implementing proper waste management program.

The implementation of proper solid waste management program has the potential to support

the principles of sustainable development. The practice of reuse and recycling of solid waste in form

of compost, biogas and materials recovery, if properly utilized by developing countries can help to

alleviate poverty and reduce problems of joblessness (World Bank, 2001; Cunninghams et al, 2005).

Also, waste to energy programs that convert combustible waste fraction of municipal solid waste into

electrical energy in controlled incinerator or combustor power plants can supplement or contribute to

the generation of decentralized electrical energy. This method of solid waste management is historical

to developed countries like Japan that burns about two-third of its wastes, Germany and France that

burn 30 and 40% of its waste respectively for power generation (Gilbert, 1998). Thus, in order to

achieve a sustainable waste management program an adequate knowledge about the types of waste

generated is needed. This will enable for proper selection of suitable management practice/technology

that can be applied to achieve this goal (Zurbrugg, 2002).

MATERIALS AND METHODS

The University of Port Harcourt in Rivers State, Nigeria comprises of three campuses:

(i) Abuja Part Campus: This campus is the largest with high population density. Most of the

residential buildings of the university staffs are found in this campus.

(ii) Delta Park Campus: This campus is the hob of administration. It also contains hostels for

female undergraduate students and few residential buildings for staffs of the university.

(iii) Choba Park Campus: This campus is the centre of commercial activities. It is the

smallest of the three campuses with hostels to accommodate male students of the university.

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In order to properly manage solid waste generated at the University, a unit known as the

Campus Environmental Beautification and Sanitation (CEBAS) was created. This unit ensures that

refuse are collected by contracted waste managers from locations which have been classified into

three zones. Each zone has a number of collection points with a final disposal site. Solid wastes

characterization was carried out at the final disposal site after a day activity.

The major collection system used at the university premises is the stationary collection

system of waste collection (SCS) with collection trucks of dimensions 0.5m by 1.8m by 3m. . The

weight of refuse was determined before loading into the collection truck using a weighing balance.

The itemization of the individual components, moisture content and density of solid waste generated

at the University was carried out at the respective zones in the three campuses. The quartering

method as described by Tchobanoglous et al (1993); Hasselriis, (1984) and Klee, (1970) was

employed for this purpose. The density of solid waste as-discarded was determined with Equation (1)

Density of solid waste as-discarded …… (1)

The moisture content as percentage wet weight of solid waste (Pw) and dry weight (Pd) of the solid

waste components were determined from typical values as presented by Tchobanoglous et al., (1993)

(Table 1) using Equation (2) and (3). In determining the moisture content for various waste types, a

100kg sample was assumed as the basis.

100 xS

W P

w

w= …………………………………… (2)

100 xS

W P

d

d =

…………………………………….. (3)

The

…………………..... (4)

While the Mass of waste fraction (kg) can be represented by Equation (5)

………………………………… (5)

Where;

Pw = moisture content as a percentage wet weight of solid waste

Pd = moisture content as a percentage dry weight of solid waste

Sd = dry weight of solid waste (kg)

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Sw = wet weight of solid waste (kg) assumed as 100kg

W = total moisture content (kg)

Table 1: Moisture content for various solid wastecomponents

Source; Tchobanoglous et al (1993)

In order to assess the heating value (energy content) of the waste generated, the Equation (6)

as developed by Khan and Abu-Gharah (1991) was employed.

…………………………….. (6)

RESULT AND DISCUSSION

The number of trips made to the final disposal site for Abuja, Choba and Delta park

campuses (zones) were 8, 6 and 4 trips per day respectively. It was observed that the weight per

trip/day was approximately 152.2kg. With a population of approximately 50,000 persons (CEBAS,

2009), the solid waste generation rate was determined to be 0.55kg/capital /day (Table 2).

Figures 1-3 show the corresponding composition of various waste components as determined

for the three campuses. Plastic materials within the three campuses ranged between 35.3% - 41.7% by

weight and it was the most abundant waste type identified at the University of Port Harcourt.

Polyethylene sachet for packaging table water popularly called “pure water”, soft drinks, cosmetics

products and disposable bags contributed to the total amount of plastic materials.

Paper and food waste ranked second and third respectively in abundance ranging between

21.8% - 25% and 10.3% - 12.3%by weight, respectively. Yard waste ranked fourth ranging between8% - 10.3% followed by ash, dirts, and bottles which ranked fifth and sixth between the range of 3.2%

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Components Moisture content (%)

plastic 2.00

papers 6.00

glass 2.00

tin 3.00

wood 20.00

leather 10.00

yard waste 60.00

textile 10.00

food waste 70.00

ash,dirt,etc 8.00

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- 6.4% and 4% - 6% by weight, respectively. Tin and wood ranked seventh and eight respectively

while textile and leather were the lowest components ranking ninth and tenth and ranged between 1%

- 2% and 0.6% - 1.8% by weight, respectively.

The average composition of waste types generated in the university was thus observed to

comprise of plastic (38.33%), paper (23.33%), glass (4.8%), tin (3.2%), wood (1.9%), leather (1.2%),

yard waste (9.45%), textile (1.0%), food waste (11.03%) and ash/dirt (5.03%). The high amount of

paper and food waste may be attributed to the nature of the area of study, being an academic

institution.

Table 2: Solid waste loading character at the University of Port Harcourt

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Zone Number Of

Trips/day

Weight Of Refuse

per Day (kg/d)

Volume Of

Refuse (m3/ d)

Density

As-Discarded

(kg/m3)

Abuja park 8 12,185.60 21.60 564.15Choba park 6 9,129.20 16.20 564.15

Delta park 4 6,092.80 10.80 564.15

Total 18 27,407.60 48.60

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Figure 4 shows the relative distribution of the various waste types within the three campuses.

However, a one way analysis of variance (ANOVA) to establish if any significance difference existed

in the solid waste types generated within the three campuses was carried out using Microsoft Excel

ANOVA function. ANOVA revealed that solid waste types generated within the three campuses was

not significantly different from each other at 95% confidence interval. A critical F-value of 3.35 was

observed against a calculated F-value of 0.000181 which implies a case of no significant difference

amongst the solid waste types generated within the three campuses.

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The moisture contents of solid waste as a percent wet weight (P w) were observed for Abuja park,

Choba park, and Delta park to be, 17.09%, 18.06% and 15.3% respectively, while the moisture

contents as a percent of dry weight (Pd) were observed for Abuja park Choba park and Delta park

campuses as 20.6% and 22.03%, 18.67%, from the Equation (1) and (2) respectively. These values are

close to that determined by Igoni et al (2006), who determined the liquid composition of solid waste

in Port Harcourt metropolises to be 19.1%

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Table 3: Moisture content (kg) of solid waste at university of Port Harcourt campuses

Components Abuja park campus Choba park campus Delta park campus

plastic 0.706 0.76 0.834

papers 1.482 1.5 1.308

glass 0.088 0.08 0.12

tin 0.129 0.045 0.12

wood 0.46 0.4 0.32

leather 0.18 0.06 0.14yard waste 6.18 6.06 4.8

textile 0 0.1 0.2

food waste 7.35 8.61 7.21

Ash ,dirt, etc 0.512 0.44 0.256

Total (kg) 17.087 18.055 15.308

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The high amount of plastic, paper and food wastes suggest that solid waste may be amenable

to various waste management technology options. Segregation of plastic paper waste for recycling

purpose, separation of food waste for compost or biogas generation or incineration of the entire waste

types are possible options available in handling waste generated in the university of port Harcourt

campuses.

However, due to the tedious nature of segregation and separation of solid waste the

combustion of the entire waste types generated at the university may be a feasible option. Also,

because the moisture content of the solid waste types observed in this study was not so high with little

inert materials, combustion in a controlled incinerator may provide a suitable means of solid waste

reduction.

The energy content estimation of solid waste is useful in assessing if the solid waste can be a

source of energy for electricity generation when combusted in a controlled incinerator whereby, the

heat produced from the combustion of these solid waste is utilized in boilers that convert water to

steam which in turn can be used to drive turbines that eventually converts mechanical energy to

electrical energy (Tchbanoglous et al, 1993; Edward, 2001). Equation (6) is very effective in

estimating the energy content of solid wastes, when the amount of yard waste is small enough to be

neglected.

Substituting PLR, CP, and F into the Equation (6), the energy content of solid waste

generated in Abuja Park, Choba Park and Delta park campuses were estimated to be 17.5, 18.6 and

19.2 MJ/kg respectively. These values are only approximations because the yard wastes content are

not small enough to be neglected. Nonetheless, the values obtained are high when compared to the

heating value of sub- bituminous coal which is 19.4 MJ/kg (EPRI, 1997) and (USDOE, 1997). Thus,

with an average energy content of 18.43MJ/kg and a total solid waste generation rate of 27,407kg/day

from the three campuses (as shown in Table 2) simulation of electrical output can be carried out by

assuming different operating overall efficiencies for the mass-fired combustor (incinerator) power

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Table 4 : Dry weight (kg) of solid waste at university of Port Harcourt campuses

Components Abuja park campus Choba park campus Delta park campus

plastic 34.594 37.240 40.866

papers 23.218 23.500 20.492

glass 4.312 3.920 5.880

tin 4.171 1.455 3.880wood 1.840 1.600 1.280

leather 1.620 0.540 1.260

yard waste 4.120 4.040 3.200

textile 0.000 0.900 1.800

food waste 3.150 3.690 3.090

Ash, dirt, etc 5.888 5.060 2.944

Total (kg) 82.913 81.945 84.692

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plant. The overall efficiency of a mass-fired combustor power plant is given by Equation (7) (Edward,

2001).

However, the energy input is the product of the flow rate of fuel source which in this case is solid

waste of about 27,407kg/day and the heating value of the fuel (Edward, 2001).

Therefore,

Hence, the potential for electrical energy generation for a fuel mass fed rate of 27,407kg/day, heating

value of 18.43MJ/kg and assumed overall efficiency values that range between 0.1 to 1.0 can be

projected as shown in Figure 5.

It is important to note that the . For example, if

the combustor power plant were to operate at an assumed overall efficiency of 0.1, then the energy

output would be as follows;

It can be observed that, if the combustion plant was to operate at 10% efficiency, as much as 584.6kW

of electricity can be generated each day while as much as 2923.1kW of electricity can be generated

each day at 50% efficiency (Fig. 5)

CONCLUSION

The solid waste generated at the University of Port Harcourt was observed to be comprised

largely of combustible materials, with plastic/polyethylene being the most abundant waste type in the

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three campuses paper, food waste and yard waste ranked second third and fourth in abundance

respectively. The average energy content of the solid waste from the three campuses was observed to

be close to that of sub-bituminous coal. The suitability of solid waste generated at the University of

Port Harcourt as a source of energy in mass-fired incinerator was assessed to be a feasible source of

electrical energy even if the mass-fired incinerator operated as an efficiency of 30%.

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CEBAS, 2009. Campus Environmental Beautification and Sanitation, University of Port- Harcourt,

Rivers State, Nigeria, Data Log.

Cunningham,W. P. Cunninghams, M. T, and B.W Saigo .2005. Environmental Science: A Global Concern, 8 th

Edition McGraw Hills NY pp.78-90.

Edward, S.R. 2001. Introduction to Engineering and the Environment, McGraw Hill Water Resources and

Environmental Engineering series, 1st Edition. U.S, pp. 163-178.

EPRI 1997, Power Plant Chemical Assessment Model Version 2.0 CM-107036 VI, Electric Power

Research Institute, Palo Alto CA pp.367-379

Gilbert, M.M 1998, Introduction to Environmental Engineering and Science, 2nd Ed. Prentice-Hall Inc. New

Delhi, p.612.

Hasselriis, F .1984. Refuse Derived Fuel, An Ann Arbor Science Book Butterworth Publisher Boston, and

p.67.

Igoni, A.H, Ayotamuno, M. J, Ogaji S.O.T. and S.D Probert 2006. Municipal Solid-Waste in Port

Harcourt, Nigeria, Applied Energy, Vol. 84(6) pp. 664-670.

Khan, Z.A and Z.H Abu-Gharah. 1991. New Approaches for Estimating Energy Content in MSW, ASCE

Journal of Environmental Engineering 117(3): 376-380

Klee A. J. and D. Carruth. 1970. Sample Weights in Solid Waste Composition Studies, ASCE Journal of the

Sanitary Engineering Division, Vol 96, No 5A, pp. 345-354

Kungskulniti, N.1990. Public Health Aspects of a Solid Waste Scavenger Community in Thailand, Waste

Management and Research 8 (2), 167-170.

Lohani, B. N.1984. Recycling Potential of solid Waste in Asia Through Organized ScavengingConservation and Recycling 7(2-4), 181-190.

Sridhar, M.K.C and O. Ojediran. 1983. The Problems and Prospects of Refuse in Ibadan City, Nigeria. ,

Senate Committee on Environment and Ecology, Solid Waste Management in the 21st century

Nigeria, pp.1-8

Tchobanoglous. G, Theisen H, and S.Vigil. 1993. Integrated Solid Waste Management: Engineering

Principles and Management Issues. McGraw Hill U.S, pp.292-295

UNEP-IETC,HIID, 1996. International Source Book on Environmentally Sound Technologies for

Municipal Solid Waste Management United Nation Environment Programme

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(UNEP).International Environment Technology Centre (IETC)

www.encapafrica.org/sectors/solidwaste USDOE 1997. Annual Energy Outlook 1998 DOE/EIA-0383(98) Energy Information Administration, US

Department of Energy, Washington DC p.300

World Bank 2001. The Philippines environment Monitor 2001, http://go.worldbank.org/

Zurbrugg, C. 2002. Urban Solid Waste Management in low-Income Countries of Asia, How to cope with

the Garbage Crisis, Scientific Committee on Problems of the Environment (SCOPE), Durban South

Africa pp.1-13

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