Estimation of landfill gas production and potential utilization in a South Africa landfill

Figures & data

Table 1. Studies conducted using different models to estimate the LFG emissions.

References	Models	Study Area
Farzadkia et al. (2015)	Mexican LandGEM version 2	Shiraz, Iran
Mou, Scheutz, and Kjeldsen (2015)	Afvalzorg, LandGem and IPCC models	Denmark
Fallahizadeh et al. (2019).	LandGEM	Yasuj-Babameydan road, Iran
Di Bella, Di Trapani, and Viviani (2011)	LandGEM and Erhig	Palermo, Italy
Njoku, Edokpayi, and Odiyo (2020).	LandGEM and Afvalzorg	Thohoyandou, South Africa
Bhailall et al. (2010)	LandGEM, GasSim and IPCC	Johannesburg, South Africa
Donovan et al. (2010)	GasSIM	Berkshire, England
Larsson (2014)	LandGEM, IPCC and Afvalzorg	Kikås landfill, Sweden

Table 2. 2012 Potential energy recoveries from LFG recovery (TJ/year) in urban areas of Africa (Scarlat et al., 2015).

Countries	Potential electricity generation (TJ/year)	Potential electricity generated using the total CH4 captured (TJ/year)
Algeria	24,663	22,690
Angola	4808	2067
Benin	1692	389
Botswana	1152	496
Burkina Faso	1905	762
Burundi	437	175
Cameroon	7799	3353
Cape Verde	130	124
Central African Rep.	704	281
Chad	1325	265
Comoros	449	90
Congo Rep	9911	3965
Congo	1166	501
Cote d׳Ivoire	4013	1605
Djibouti	291	125
Egypt	41,502	26,146
Equatorial Guinea	200	86
Eritrea	492	197
Ethiopia	3450	1380
Gabon	532	229
Gambia	450	180
Ghana	949	806
Guinea	1340	536
Guinea-Bissau	168	67
Kenya	2288	915
Lesotho	260	112
Liberia	723	289
Libya	5297	2278
Madagascar	4237	763
Malawi	1289	541
Mali	3095	1238
Mauritania	594	178
Mauritius	1102	1080
Mayotte	144	137
Morocco	23,354	20,085
Mozambique	1069	449
Namibia	383	165
Niger	1106	465
Nigeria	37,275	15,656
Rwanda	888	373
Réunion	1639	1557
Saint Helena	4	4
Sao Tome	42	40
Senegal	2286	480
Seychelles	127	121
Sierra Leone	841	370
Somalia	881	370
South Africa	55,420	27,710
Sudan	13,084	5626
Swaziland	116	55
Tanzania	2953	1240
Togo	1142	1085
Tunisia	5143	2006
Uganda	1445	433
Western Sahara	203	41
Zambia	918	386
Zimbabwe	2361	1170
Total Africa	282,602	154,520
Sub-Saharan Africa	182,439	81,275

Figure 1. Study area map for Weltervenden landfill.

Figure 2. Pie chart showing the average annual composition of waste present in the Weltervenden landfill.

Table 3. Values of DOC in Southern African region.

DOC (by weight wet basis)	Default	Range
Food waste	0.15	0.08–0.20
Garden	0.20	0.18–0.22
Bulk MSW	0.20	0.12–0.28
Sewage sludge	0.05	0.04–0.05
Industrial waste	0.15	0–0.54

Table 4. Input data for the simulation of LFG to run the LandGEM and Afvalzorg models.

Input Data	Weltervenden landfill site
Year landfill commenced operation	1999
Potential year of closure of landfill	2022
Degradation constant k (/year)	0.05
Potential Methane Generation Capacity L0 (m^3/Mg)	100
Methane correction factor MCF (managed anaerobic landfill)	1
Oxidation Factor OX (managed and covered landfill with oxidizing material)	0.1
Recovery efficiency	0
The total amount of waste deposited in the landfill annually from the inception of the landfill	Derived from SAWIC website and Municipality
The general waste composition	Shown in Figure 2
Degradable Organic Compound (DOC)	Shown in Table 2

Figure 3. Graphical representation showing the CH₄ and CO₂ emissions using the LandGEM.

Figure 4. Simulation of CH₄ emission from the Weltervenden landfill site using the Afvalzorg model.

Figure 5. Comparison of the simulation of CH₄ using the Afvalzorg and LandGEM models for the Weltervenden landfill site.

Table 5. Economic and financial results for the implementation of a LFG Technology for Weltervenden landfill site.

LFG Engines	Area of LFG wellfield to supply project(hectare)	Down payment for project	Net Present Value (NPV) million (Rands) year of construction	Internal Rate of Return (IRR)	Years to Breakeven	LFG Energy Project million (Rands)	Total Capital Costs million (Rands)	Annual Operations and Management costs million (Rands)
Standard turbine generator set	20	50%	66	Negative	None	83	96	7
		100%	65	−32	None
	40	50%	87	Negative	None	83	104	8
		100%	86	Negative	None
Standard reciprocating engine-generator set	20	50%	68	Negative	None	74	87	10
		100%	67	Negative	None
	40	50%	88	Negative	None	74	96	11
		100%	87	Negative	None
Microturbines	20	50%	11	5%	None	41	54	3
		100%	12	6%	None
	40	50%	27	−3%	None	41	62	5
		100%	26	1%	None
Combined Heat and Power (CHP) turbine	20	50%	50	−7%	None	96	109	7
		100%	49	−1%	None
	40	50%	67	−11%	None	96	117	8
		100%	66	−5%	None
CHP microturbine	20	50%	5	16%	8	43	56	3
		100%	3	12%	9
	40	50%	7	10%	None	43	65	5
		100%	9	8%	None

Note: These financial results include the costs associated with a completely new LFG collection (costs for expansion of an existing system will be higher).

Table 6. A step by step conversion of methane to t CO₂e.

Methane (m^3) emitted using LandGEM	Step 1: 85% of methane (m^3) captured and combusted	Step 2: Covert methane (m^3) to tonnes by multiplying by 0.000717 tCH4/m^3	Step 3: Convert methane (tonnes) to CO2equivalent by multiplying by 25
6.122E+06	5.20E+06	3.73E+03	9.33E+04
6.521E+06	5.54E+06	3.97E+03	9.94E+04
6.914E+06	5.88E+06	4.21E+03	1.05E+05
6.577E+06	5.59E+06	4.01E+03	1.00E+05
6.256E+06	5.32E+06	3.81E+03	9.53E+04
5.951E+06	5.06E+06	3.63E+03	9.07E+04
5.661E+06	4.81E+06	3.45E+03	8.63E+04
5.385E+06	4.58E+06	3.28E+03	8.20E+04
5.122E+06	4.35E+06	3.12E+03	7.80E+04
4.872E+06	4.14E+06	2.97E+03	7.42E+04
4.635E+06	3.94E+06	2.82E+03	7.06E+04
4.409E+06	3.75E+06	2.69E+03	6.72E+04
4.194E+06	3.56E+06	2.56E+03	6.39E+04
3.989E+06	3.39E+06	2.43E+03	6.08E+04
3.795E+06	3.23E+06	2.31E+03	5.78E+04
3.610E+06	3.07E+06	2.20E+03	5.50E+04

Table 7. Annual electricity generated in kWh for the different LFG engines.

Year	Standard turbine generator set	Standard reciprocating engine-generator set	Microturbines	CHP turbine	CHP microturbine
2023	10,861,799	13,264,561	9,512,891	10,861,799	9,512,891
2024	11,570,525	14,130,065	10,133,601	11,570,525	10,133,601
2025	12,268,526	14,982,472	10,744,918	12,268,526	10,744,918
2026	11,670,182	14,251,768	10,220,882	11,670,182	10,220,882
2027	11,101,021	13,556,701	9,722,404	11,101,021	9,722,404
2028	10,559,618	12,895,533	9,248,237	10,559,618	9,248,237
2029	10,044,619	12,266,611	8,797,195	10,044,619	8,797,195
2030	9,554,737	11,668,361	8,368,151	9,554,737	8,368,151
2031	9,088,747	11,099,288	7,960,031	9,088,747	7,960,031
2032	8,645,484	10,557,970	7,571,816	8,645,484	7,571,816
2033	8,223,839	10,043,051	7,202,534	8,223,839	7,202,534
2034	7.82E+06	9,553,246	6,851,262	7,822,757	6,851,262
2035	7.44E+06	9,087,329	6,517,122	7,441,237	6,517,122
2036	7.08E+06	8,644,134	6,199,278	7,078,323	6,199,278
2037	6.73E+06	8,222,555	5,896,936	6,733,110	5,896,936

Table 8. The average electricity per year generated and the number of household beneficiaries.

Engines	Standard turbine generator set	Standard reciprocating engine-generator set	Micro turbines	CHP turbine	CHP microturbine
Average electricity generated (KWh /year)	9,510,968	11,614,910	8,329,817	9,510,968	8,329,817
Average households to benefit	4194	5121	3673	4194	3673

Farzadkia, M., B. Djahed, S. Shahsavani, and E. Dehghanifard. 2015. Prediction of gas emission and derived electrical power generation from shiraz landfill. Global Nest J. 17 (3):487–97.

 Web of Science ®Google Scholar

Mou, Z., C. Scheutz, and P. Kjeldsen. 2015. Evaluating the methane generation rate constant (k value) of low-organic waste at Danish landfills. Waste Manage. 35:170–76. doi:10.1016/j.wasman.2014.10.003.

 PubMed Web of Science ®Google Scholar

Fallahizadeh, S., M. Rahmatinia, Z. Mohammadi, M. Vaezzadeh, A. Tajamiri, and H. Soleimani. 2019. Estimation of methane gas by LandGEM model from Yasuj municipal solid waste landfill, Iran. MethodsX 6:391–98. doi:10.1016/j.mex.2019.02.013.

 PubMed Web of Science ®Google Scholar

Di Bella, G., D. Di Trapani, and G. Viviani. 2011. Evaluation of methane emissions from Palermo municipal landfill: Comparison between field measurements and models. Waste Manage. 31 (8):1820–26. doi:10.1016/j.wasman.2011.03.013.

 PubMed Web of Science ®Google Scholar

Njoku, P. O., J. N. Edokpayi, and J. O. Odiyo. 2020. Modelling landfill gas potential and potential energy recovery from Thohoyandou landfill site, South Africa. J. Air Waste Manage. Assoc. 70 (8):820–33. doi:10.1080/10962247.2020.1778137.

 PubMed Web of Science ®Google Scholar

Bhailall, S., S. Piketh, N. Smith, and J. Bogner. 2010. Subsurface gas generation at a landfill in Johannesburg. Clean Air J. Tydskrif vir Skoon Lug 18 (1):10–14.

 Google Scholar

Donovan, S. M., T. Bateson, J. R. Gronow, and N. Voulvoulis. 2010. Modelling the behaviour of mechanical biological treatment outputs in landfills using the GasSim model. Sci. Total Environ. 408 (8):1979–84. doi:10.1016/j.scitotenv.2009.12.011.

 PubMed Web of Science ®Google Scholar

Larsson, J. 2014. A case study of landfill gas potential at Kikås landfill-Assessment of environmental impacts and alternatives for mitigation ( Master’s thesis).

 Google Scholar

Scarlat, N., V. Motola, J. F. Dallemand, F. Monforti-Ferrario, and L. Mofor. 2015. Evaluation of energy potential of municipal solid waste from African urban areas. Renew. Sust. Energ. Rev 50:269–1286.

 Web of Science ®Google Scholar

Data availability Statement

The data that support the findings of this study are available from the corresponding author, (P.O Njoku), upon reasonable request.