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ESTIMATING EMISSIONS OF METHANE (CH4)
FINAL RESULT REPORT PREPARED TO BE PRESENTED TOTHE GHG INVENTORY PROJECT STEERING COMMITTEE
1999
July 1999
Addis Ababa
Ethiopia
3
E S T I M A T I N G E M I S S I O N O F
M E T H A N E (CH4)
F R O M S O I L D W A S T E
By:
Fikru Tessema (M.Sc, B.Sc, D.Sc)
Consultant
i
DEFINITION OF TERMS
1. Green House Gases (GHG): are gases like methane, carbon dioxide, nitrous
oxide, CFC-11, HCFC- & CF4 that contribute effects to the climate change.
2. Methane: is a GHG emitted from waste under anaerobic condition.
3. Landfill: is a land disposal method for solid waste.
4. Municipal Solid Waste: is a waste generated by every urban dweller.
5. Urban Center: is the urban settler with more than 2 thousand number of
population.
6. Methane Correction Factor (MCF): is a value obtained by dividing the
methane atomic weight by carbon atomic weight.
7. Degradable Organic Carbon (DOC): is the organic component in MSW that
actually degrades.
8. Disposal Rate: is the per capita based rate of disposing of the portion of
solid waste generated per person per day in kg.
9. Waste: is the unwanted material that can exist in solid or liquid form.
ii
ACRONYMS
1. CSA : Central Statistics Authority
2. GHG : Greenhouse Gas
3. IPCC : Intergovernmental Panel on Climate Change
4. MSW : Municipal Solid Waste
5. SWDS : Solid Waste Disposal Site
6. CH4 : Methane
7. DOC : Degradable Organic Carbon
8. CO2 : Carbon dioxide
9. Gg : Giga gram
iii
Executive Summary
A retrospective data based estimation of methane emissions from solid waste
disposed of in the solid waste disposal sites for urban centers of Ethiopia has been
done for GHG inventory for each year 1989-1998.
The population of Addis Ababa City accounts about 28% of the total population of
urban centers of Ethiopia and the other urban centers 72%. The work of solid waste
management is left for the Municipality in most urban centers of Ethiopia.
The solid waste generation units of per capita per day in Addis Ababa City,
according to the Norconsult 1982 study, was 0.15 kg with 1% growth rate per year
per capita based. According to the Louisberger consultant 1995 study, it was also
0.35, 0.28 and 0.17 kg/ c/ day for high, medium and low-income group respectively.
The major organic components of MSW of Addis Ababa City are paper & textiles,
(4.8%); grass, leaves & other organic putrescibles, (22.6%); food waste, (4.5%) and
wood & straw/ organic fines (35.7%).
The method employed to dispose solid waste in urban centers of Ethiopia is land
disposal called landfill. In order to complete the estimation of methane emissions
from SWDSs, the data on solid waste have been collected from Health Bureau for
Addis Ababa City and estimated using the IPCC methods for the rest of urban
centers of Ethiopia.
On the average, about 86.7 Gg MSW was disposed of in landfill for Addis Ababa
City and 387.2 Gg MSW for other urban centers per year (Table – I).
iv
The IPCC default methodology is divided into four parts: (1) Estimation of total
MSW generated and disposed of in SWDSs; (2) Determination of methane
correction factor; (3) Estimation of methane production rate per unit of waste and
(4) Estimation of total net annual methane emissions. There are also four steps to
complete each part, which finally gives net annual methane emissions.
The Addis Ababa City landfills methane emission accounts 18% of the total annual
emissions and the other urban centers 82%.
Methane emitted from solid waste placed in SWDSs is not recovered. Since there is
no methane recovery, the net annual emission of methane is equal to the gross and
net annual generation. On the average, about 5.3 Gg CH4 was emitted from the
landfill for Addis Ababa City and 23.8 Gg CH4 for the other urban centers per year
(Table-II).
Methane emissions from SWDSs increases by 34% of the base year (1989) emissions
for Addis Ababa City and 39% for the rest of urban centers. This implies that there is
a significant emission from landfill for Addis Ababa City.
This inventory has also quite demonstrated that a significant increase of country
methane emissions by 38% of the base year emissions from SWDSs for urban
centers of Ethiopia.
This GHG inventory, therefore, recommends that every local authority should no
longer continue to ignore methane emissions estimation that will help to design
mitigation strategies for GHG concentration reduction in the atmosphere globally
and locally.
v
TABLE OF CONTENTS
CONTENTS PAGE
DEFINITION OF TERMS ..........................................................................................................................................i ACRONYMS ........................................................................................................................................................... ii Executive Summary ............................................................................................................................................ iii TABLE OF CONTENTS ............................................................................................................................................ v CHAPTER - 1 ............................................................................................................................................................ 1
1.1 INTRODUCTION ....................................................................................................................................... 1 1.2 BACKGROUND ......................................................................................................................................... 1
1.2.1 URBAN POPULATION OF ETHIOPIA: .............................................................................................. 1 1.2.2 SOLID WASTE MANAGEMENT IN URBAN CENTERS OF ETHIOPIA: ............................................. 3 1.2.3 WASTE GENERATION RATE: ........................................................................................................... 3 1.2.4 PHYSICAL COMPOSITION OF WASTE BY WEIGHT: ....................................................................... 4 1.2.5 QUANTITY OF SOLID WASTE DISPOSED TO THE SWDSs: ............................................................ 4 1.2.6 ESTIMATION OF METHANE EMISSIONS FROM SWDSs: ............................................................... 5
1.3 OBJECTIVES ............................................................................................................................................. 6 1.3.1 GENERAL OBJECTIVES .................................................................................................................... 6 1.3.2 SPECIFIC OBJECTIVES ...................................................................................................................... 6
1.4 METHODS ................................................................................................................................................ 6 1.4.1 GENERAL METHODOLOGY: ............................................................................................................ 6 1.4.2 IPCC METHODOLOGY: ..................................................................................................................... 7
CHAPTER - 2 ......................................................................................................................................................... 10 2.1 RESULTS ................................................................................................................................................ 10
CHAPTER - 3 ......................................................................................................................................................... 11 3.1 DISCUSSION .......................................................................................................................................... 11 3.2 CONCLUSION ......................................................................................................................................... 12 3.3 RECOMMENDATIONS ........................................................................................................................... 12
REFERENCES ........................................................................................................................................................ 13
1
CHAPTER - 1
1.1 INTRODUCTION
The greenhouse gases are gases that exist with different concentration in the
atmosphere. Their concentration can increase in the atmosphere as a result of
some human activities and natural processes. The GHG are emitted with
different quantity of emissions from different sources. Solid waste disposal
site is one of the areas that generate the GHG like methane, carbon dioxide,
etc. Methane is the most common gas that released from solid waste under
anaerobic condition. CO2 is also released from shallow solid waste disposal
sites.
A significant quantity of methane emissions is from municipal solid waste
disposed of in the landfill for urban population (1). It is insignificant for rural
population because the amount of waste that goes to solid waste disposal
sites is very few. Estimation of methane emissions from solid waste placed in
solid waste disposal sites for urban centers is more important because it is the
urban centers that managed its waste.
Some major urban cities of Ethiopia that are found in the Northern part
Gondar, Mekele, Baherdar, and Debermarkos, in the Eastern Desie, Deriedwa,
Harar, and Asela, in the Southern Awassa, Arbamench, Jimma, Metu and
Goba, in the Western Nekement and in the Central Addis Ababa and Nazeret
(2).
1.2 BACKGROUND
1.2.1 URBAN POPULATION OF ETHIOPIA:
The urban population in Ethiopia is currently estimated at 15.4% and it is
expected to increase to 30% by the year 2020. This implies that the waste
2
generation and methane emissions for urban centers will also increase
substantially by the year 2020.
Table – III Some Major Urban Cities of Ethiopia and Their Population,
1998
Se.
No.
Cities
Population
1 Mekele 114 721
2 Gondar 60 837
3 Dire Dawa 195 546
4 Dessie 115 590
5 Debre Markos 58 230
6 Bahir Dar 113 852
7 Nekemet 56 492
8 Metu 25 337
9 Jimma 108 638
10 Nazeret 181 642
11 Assela 61 011
12 Harar 90 386
13 Goba 33 895
14 Awassa 86 041
15 Arbamench 47 801
16 Addis Ababa 2 354 000
Source: CSA, 1994 Population and Housing Census Projection
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1.2.2 SOLID WASTE MANAGEMENT IN URBAN CENTERS OF ETHIOPIA:
The municipality in most urban centers of Ethiopia carries out the solid waste
management services. It involves collection and transportation of waste and
its disposal to solid waste disposal sites (1).
Addis Ababa, among the forefront growing cities of Ethiopia, has commenced
its solid waste management service over three decades ago. It was only the
Municipality that managed solid waste generated in the city. The time when
the management of solid waste was started in Addis Ababa, the collection and
disposal capacity of the Municipality was very limited. Out of many tones of
waste generated per day in the city, few portions were collected by the
municipal refuse collection system (6).
Currently, the Health Bureau is engaged to collect solid waste. The collection
efficiency is estimated to be 65% of the total waste generated in Addis Ababa
City, but it is not yet known for the rest of urban centers (7). The most
commonly used for solid waste disposal method in the urban centers of
Ethiopia is the land disposal called landfill (1).
1.2.3 WASTE GENERATION RATE:
Quantity of waste generation units of per capita per day in Addis Ababa City
was very much unclear until 1982 when a Nor consultant, a private company on
waste management, first published its findings. Gordon Sturdy, a Louisberger
consultant was also made a study on solid waste generation rate in 1994 &
1995 (4,5).
According to the Nor consultant study on the solid waste generation rate in
Addis Ababa City, the per capita per day generation was 0.150 kg and density
per cu.m was 370kg. In its conclusion, the volume growth rate of the domestic
solid waste generation has an increase of 1% per year per capita based (4).
4
According to the Louisberger consultant study, based on the income level, the
unit of domestic waste generation of per capita per day is 0.35, 0.28 and 0.17
kg for high, medium and low income group respectively (5).
For other urban centers of Ethiopia, the quantity of solid waste generation
units of per capita per day is not yet clear because there is no study done on
the solid waste generation rate.
1.2.4 PHYSICAL COMPOSITION OF WASTE BY WEIGHT:
The most common and major components of solid waste in cities of
developing countries, like Ethiopia, are organic substances and fines (1).
According to the IPCC classification, the Addis Ababa City MSW has the
following composition by weight for the organic components: paper & textiles,
(4.8%); grass, leaves & other organic putrescibles, (22.6%); food waste, (4.5%);
and wood & straw waste/organic fines, (35.7%) (5).
1.2.5 QUANTITY OF SOLID WASTE DISPOSED TO THE SWDSs:
The time when Addis Ababa Municipality started refuses collection, the
disposal method employed was land disposal that was located at the border of
the city. Its surface area is estimated to be about 25 hectares with about 10
hectares in use at present. The already disposed refuse for the last 30 years is
estimated to be about six million M3 or two million tones or more than 66.7
thousand tones per year (3,7). For the last ten years (1989 – 1998), the amount
of waste disposed of in landfill was also more than 86.7 thousand tones per
year in Addis Ababa City.
The quantity of solid waste collected and disposed per year is registered in
Addis Ababa City by using the volumetric system, in M3. According to the
5
Norconsult study, 1 M3 of solid waste has a weight of 370 kg or its density is 370
kg/M3. The cubic meter converted to gigagram based on these findings (4).
Since there is no data available on MSW generation rate and fraction of MSW
disposed to SWDSs for other urban centers of Ethiopia, the quantity of solid waste
disposed to SWDSs has been estimated using the IPCC default values. For the last
ten years (1989 – 1999), the estimated quantity of refuses disposed to SWDSs was
more than 387.2 thousand tones per year.
1.2.6 ESTIMATION OF METHANE EMISSIONS FROM SWDSs:
The Ministry of Mine & Energy is the first ministry that made the first GHG
Inventory at National level and reported its findings in the year 1996. Different
sectors, based on the IPCC classification, have been assessed for the year 1990 to
1993. The waste sectors in general and municipal solid waste disposal sites in
particular were the areas that have been assessed for methane emissions.
6
1.3 OBJECTIVES
1.3.1 GENERAL OBJECTIVES
The main objective is to estimate methane emissions from SWDSs for urban
population for each year 1989 - 1998 and incorporate the CO2 emissions
estimation from shallow SWDSs in the GHG inventory, so as to have a GHG
inventory nationally and globally.
1.3.2 SPECIFIC OBJECTIVES
To estimate quantity of MSW landfilled for urban centers of Ethiopia,
excluding Addis Ababa.
To estimate methane emitted from MSW landfilled for Addis Ababa
(the capital city of Ethiopia) and other urban centers of Ethiopia.
1.4 METHODS
1.4.1 GENERAL METHODOLOGY:
A retrospective data based estimation of methane emissions from MSW
disposed of in landfills for urban centers of Ethiopia was designed for GHG
inventory. The year 1989 was taken as a base year to evaluate the ten years
emissions. The first GHG inventory results for methane emissions for the year
1990 –1993 have also been revised based on the IPCC default method revised in
1996.
The urban population of Ethiopia has been estimated to be about 12.6% of the
total population since 1989. Currently, it is estimated to be reached about 15.4%
of the total population.
Of the total urban population, about 28% is the population estimated to be
found in Addis Ababa City and 72% in the other Urban Centers of Ethiopia (2).
7
A data for the quantity of MSW landfilled for Addis Ababa City has been
collected from Health Bureau, and for other urban centers estimated using the
IPCC default values since there is no data on the fraction of MSW disposed to
SWDSs. For CO2 emissions from portion of unmanaged waste in shallow
SWDSs, there is no available method for estimation.
The compiled data has been analyzed using the IPCC workbook and processed
using computer. The figure analysis and cross tabulations have been done for
all results using the IPCC worksheet.
1.4.2 IPCC METHODOLOGY:
The IPCC default methodology is divided into four parts: (1) Estimation of total
municipal solid waste generated and disposed of in the solid waste disposal
sites. (2) Determination of methane correction factor; (3) Estimation of
methane production rate per unit of waste and (4) Estimation of total net
annual methane emissions.
The results of each step for each part are presented in the Main Work- sheet #
6-1. The first step corresponds to part 1 (Column A), second to part 2 (Column
B), third to part 3 (Column C-H) and fourth to part 4 (Column J-N).
Step 1 begins with Column A, which is derived from data compiled by using the
supplementary work sheets. The Supplementary Worksheet 6-1A is not used
for Addis Ababa City since there is detailed data on Total Annual MSW
Disposed to SWDSs (in gig grams of MSW). It is also not used for the rest of
urban centers since there is no data on MSW per Capita Generation Rate and
Fraction of MSW Disposed to SWDSs. But, the Supplementary Worksheet 6-1B
is used for the estimation of Total Annual MSW Disposed to SWDSs (in
gigagram of MSW) for the rest of urban centers. Column A of Worksheet 6-1B
8
gives Total Population per urban center, which was obtained from CSA.
Column B from the same worksheet, refers to MSW Disposal Rate to SWDS (in
kg/capita/day), which is 0.2 (default value). The value in Column C of the same
worksheet is the product of the Column A & B that gives Total Annual MSW
Disposed to SWDSs.
Step 2 begins with Column B, which refers to Methane Correction Factor
(MCF). It is also derived from information compiled by using the
Supplementary Worksheet 6-1C. Since there is no detailed data on Proportion
of Waste (by weight) for each type of SWDSs, the default value 0.6 was taken
as a Methane Correction Factor.
Step 3 begins with Column C that is the Estimation of Methane Production
Rate per Unit of Waste. Values presented in Column C are given by estimating
the Fraction of Degradable Organic Carbon (DOC) in the MSW by using Table 6-
3. It is calculated for Addis Ababa City by using data on the organic component
of MSW of the city. According to the IPCC classification of organic components
of MSW, the DOC by weight in each type of waste stream in MSW is given as:
% DOC (by weight) =(0.4x0.048)+(0.17x0.226)+(0.15x0.045)+(0.3x0.357)
Where:
0.4, 0.17, 0.15 and 0.3 are IPCC default values for % of DOC by weight
in each type of organic waste in MSW.
0.048, 0.226, 0.045 and 0.357 are country data for % composition by
weight for each type of organic waste in MSW (5).
The values can show DOC in MSW 0.2 for Addis Ababa City. Since this value
closely corresponds to the conditions in other urban centers, it is also used for
DOC in MSW for the rest of urban centers.
9
It can be seen in Column D & E that the default values 0.77 & 0.5 for the
Fraction of DOC Which Actually Degrades and Carbon Released as Methane
respectively. Column F gives information on Conversion Ratio (the atomic
weight of methane is divided by carbon atomic weight). The product of the
values in Column C, D, E & F derives Column G. The product of the values in
Column B in step 2 and Column G in step 3 gives Column H for Methane
Generation Rate per Unit of MSW.
Step 4 is referred to the Estimation of the Total Net Annual Methane
Emissions. The product of values in Column H of step 3 and Column J of step 4
gives the Gross Annual Methane Generation (in Gg of CH4). Since there is no
Methane Recovery, the Gross Annual Methane Generation and Net Annual
Methane Generation (in Gg of CH4) are equal. Since One minus Methane
Oxidation Correction Factor in column M of step 4 is 1, the products of Column
L in step 4 and column M finally gives the Total Net Annual Methane Emissions
(in gigagram of methane).
10
CHAPTER - 2
2.1 RESULTS
The estimated amount of total municipal solid waste disposed to solid waste
disposal sites is given in the (Table – 1 & 2) and net annual methane generation
in (Table – 3 & 4).
11
CHAPTER - 3
3.1 DISCUSSION
The quantity of methane emission is influenced by the quantity and
composition of solid waste disposed to the disposal sites and the depth of
waste in the site (1).
This inventory of GHG, therefore, demonstrates that the methane emissions
increase or decrease with the increase or decrease of MSW disposed to the
disposal sites and the variation of the amount of methane emitted in each year
continue to vary with the variation of the amount of MSW landfilled.
In the last ten years (1989 – 1998), the methane emissions from landfill for
Addis Ababa City increased by 34% of the base year (1989) emission and 39% for
other urban centers.
The overall increase of methane emission has quite demonestrated that a
significant increase of methane emissions by 38% of the base year emissions
from SWDSs for urban centers of Ethiopia.
The increase of methane emissions in the past ten years for Addis Ababa City
was very close to the other urban centers of Ethiopia. This implies that there is
a significant emission from Addis Ababa City Municipal Landfill. The Addis
Ababa City landfill methane emission accounts 18% of the total country
emissions per year and the other urban centers 82%.
The revised GHG inventory in each year 1990 – 1993 also came up with results
that have no significant difference from the first GHG inventory results for
Addis Ababa City. But, there is significant difference for other urban centers
12
due to difference in the situational analysis for solid waste management in
urban centers of Ethiopia and using IPCC default values.
Some studies shew that the per capita per day generation rate for solid waste
in Addis Ababa City is estimated to be 0.27 kg (weighted mean) per person per
day. The disposal rate is also estimated to be reached about 0.2 kg/ c/d. This
implies that the disposal rate for other urban centers of Ethiopia can not go far
from this value. Therefore, the default value 0.2 kg/c/d closely corresponds to
conditions in other urban centers. Thus, the default value, (0.4 kg/c/d), that
used in the first GHG inventory does not reflect the conditions in urban centers
of Ethiopia.
3.2 CONCLUSION
The increase of methane emissions substantially from year to year is alarming
from the viewpoint of climate change globally and locally. This, therefore,
indicates that the intergovernmental in general and the local government in
particular should no longer continue to ignore the issue of mitigation of GHG
emissions in the developing countries.
3.3 RECOMMENDATIONS
1. There should be mitigation assessment to design methods that will help to reduce
the concentration of GHG in the atmosphere.
2. Since the methane emissions inventory is dependant on the MSW disposed to
SWDSs, there should be an assessment for the amount of MSW disposed of in
landfills for urban centers of Ethiopia, excluding Addis Ababa.
3. Since there is high portion of solid waste in the unmanaged shallow SWDSs, the
IPCC methodology should reconsider these sites for CO2 emissions; and
incorporate its emissions from SWDSs in the GHG inventory and develop the
methodology for its estimation.
13
REFERENCES
1. H. Glas, etal, Solid Waste Disposal, Netherlands, 1994
2. CSA, The 1984 & 1994 Population and Housing Census of Ethiopia,
Addis Ababa, 1986 & 1996.
3. Kumie, A., An Overview of Addis Ababa Solid Waste and its
Management Service, Addis Ababa, 1997
4. Nor consult, Addis Ababa Solid Waste Management Study, 1982.
5. Gordon, S, Addis Ababa Solid Waste Management 3rd and 4th Study,
1994 & 1995.
6. Region 14 Health Bureau, Annual Activities Reports, Addis Ababa,
1984-1998.
7. Health Bureau, Addis Ababa, Health Sector Development Program,
A5 Year Plan (1998-2002), Addis Ababa, May 1998.