spatial and temporal variation of landfill gas collection in
SPATIAL AND TEMPORAL VARIATION OF LANDFILL GAS COLLECTION IN SUDOGWON LANDFILL IN REPUBLIC OF KOREA S. JEONG*, M.H. PARK**, J.Y. KIM** * Institute of Construction and Environmental Engineering, Seoul National University, Gwanak-ro 1, Seoul, 08826, Republic of Korea **Department of Civil and Environmental Engineering, College of Engineering, Seoul National University, Gwanak-ro 1, Seoul, 08826, Republic of Korea
SUMMARY: In order to reduce greenhouse gas emission and produce renewable energy, installation of LFG collection system is increasing. Due to safety issue and stable power generation, the concentration of CH4 and O2 in LFG collection pipes are monitored regularly and the valve opening is adjusted to meet the guidelines. In this study, monitoring data of LFG collection pipes has been used to analyse spatial and temporal variation and suggest monitoring frequencies of LFG collection pipes. More CH4 is collected from landfill sections of fresh waste is landfilled. When fresh waste is landfilled, concentration of CH4 is increased causing increase of valve opening rate. However, there were some exceptions. Most of LFG collection pipes are not adjusted during monitoring process. LFG collection pipes that has valve opening from 20 to 45% was more likely to be adjusted at next monitoring. Therefore, further analysis on the factors for LFG collection would contribute to effective monitoring practices. 1. INTRODUCTION Landfill gas (LFG) mostly consists of carbon dioxide (CO2) and methane (CH4) (Jeong et al., 2015). As methane is one of six major greenhouse gases (GHG) and solid waste landfill is third largest anthropogenic methane source in Republic of Korea (GIR, 2014). On the other hand, LFG possesses high calorific value which can be utilized as renewable energy. In order to reduce greenhouse gas emission and produce renewable energy, installation of LFG collection system is increasing. 13 LFG utilization plants are installed and 160 million Nm3 CH4 is collected in 2015 in Republic of Korea (Korea Ministry of Environment, 2016). In order to operate energy generator of LFG safely and effectively, the concentration of CH4 in collected LFG need to be controlled. There are a few guidelines on the management of LFG collection pipes. US EPA (2009) suggested to monitor flow rate, CH4 concentration, temperature and pressure to secure stable energy generation. O2 concentration below 2.5 % is recommended to prevent fire within landfill (Conestoga-Rovers & Associates, 2010; USACE, 2013). Above mentioned guidelines suggest monthly monitoring of collection pipes. Due to lack of managment guidelines, field engineers of the Sudogwon landfill, the largest landfill in Repbulic of Korea, monitor LFG collection pipes and adjust valve openings every working day. Therefore, spatial and temporal variation of landfill gas collection has been analyzed to suggest proper management practices of LFG collection pipes.
Proceedings Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium/ 2 - 6 October 2017 S. Margherita di Pula, Cagliari, Italy / © 2017 by CISA Publisher, Italy
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
2. MATERIALS AND METHODS 2.1 Study sites The Sudogwon landfill site is the largest landfill where 47.7 % of landfilled solid waste is treated in 2015 in Republic of Korea (Korea Ministry of Environment, 2016). The Sudogwon landfill consists of two landfills, 1st landfill and 2nd landfill. The 1st landfill was closed in 2001 and the 2nd landfill started landfilling since 2000. More than 65 million ton of municipal solid waste has been landfilled and still under operation in the 2nd landfill of Sudogwon landfill (Sudogwon Landfill Site Management Corp., 2016). The 2nd landfill is divided into 25 sections (Fig. 1). 2.2 Monitoring and adjustment of landfill gas collection pipes LFG collection system has been installed in 2001 in 2nd landfill. Horizontal and vertical LFG collection has been installed. LFG in horizontal pipes is sent to 699 vertical LFG collection pipes. 699 vertical LFG collection pipes are controlled in 44 manifold stations. LFG collection pipes are monitored by every working day. LFG monitoring data from 2012 to 2016 has been used in the analysis.
Table. Monitoring data in the 2nd Sudogwon landfill Year
Date of monitoring (days)
No. of LFG collection pipes
Total No. of data
2012
241
699
168,459
2013
205
699
143,295
2014
245
699
171,255
2015
197
699
137,703
During monitoring of LFG collection pipes, the concentration of CH4, CO2 and O2 (%), temperature (℃), pressure (mmAq) and flow rate (m3/min) are monitored (Fig. 2). In order to secure stable power generation and prevent landfill fire, the valve of opening of LFG collection pipes was adjusted when the concentration of CH4 is below 48% or the concentration of O2 is over than 5%. The valve opening on LFG collection pipe can be controlled from 0% to 100% at intervals of 5%.
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
Fig. 1. Landfill sections and manifold stations in 2nd landfill
Fig. 2. Monitoring of LFG collection pipes
3. RESULTS AND DISCUSSIONS 3.1 Spatial variation of LFG collection The landfill is conducted successively for landfill sections in the 2nd Sudogwon landfill. Fig. 3 shows the age of landfilled waste at the top landfill layer. As decomposition of organic matters is considered as first order, the top-left landfill sections (E-4, F-4 and F-3) are expected to collect more CH4 than other landfill sections. F-4 and F-3 showed higher CH4 collection as expected (Fig. 4). However, central landfill sections showed relatively higher CH4 collection while the age of waste at top layer is old.
Fig. 3. The age of landfilled waste at the top layer in 2014
Fig. 4. Annual CH4 collected in 2014 (unit: 103 m3CH4/year)
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
Fig. 5. Monthly CH4 collected by landfill area in (left) Mar., (center) Jun., (right) Aug. 2014
3.2 Valve opening rate Valve opening rate indicates CH4 concentration in LFG collection pipes because valves are adjusted based on the concentration of CH4. Fig. 6 shows the average valve opening rate in each landfill section. Over four years of monitoring, valve opening rate tent to increase when new waste is landfilled. In the section C-2 and C-3 showed increase of valve opening rate from 40 to 100 % (day 130) when new waste is landfilled, respectively. However, there were some cases that valve opening rate didn’t increased despite fresh waste is landfilled. In the sections in line D, there were no significant increases in valve opening rate or decreased soon after landfill of fresh waste.
100 C-1 C-2 C-3 C-4
Valve opening rate (%)
80
60
40
20
0 0
100
200
300
400
500
600
700
800
900
1000
Time (day)
100
Valve opening rate (%)
80
60
40
D-1 D-2 D-3 D-4
20
0 0
100
200
300
400
500
600
Time (day)
Fig. 6. Valve opening rate of landfill sections in line C and F
700
800
900
1000
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
3.3 Adjustment of valve opening rate Valve opening is adjusted when the concentration of CH4 is below 48% or the concentration of O2 is over than 5% for stable energy production and safety. Average frequency of valve adjustment was 56.9 ± 42.8 times per year (Fig. 7). For one time monitoring, 71.8% of LFG collection pipes kept their valve opening rate and 19.9 % of LFG collection pipes adjusted 5% of opening rate. LFG collection pipes which have valve opening from 20% to 45% have more chances to be adjusted. Field engineers adjust valve opening for 5% per day. Consequently, total number of adjustment is large and adjustment for the LFG collection pipes for valve opening between 20% and 45% is frequent because it is on the process to find proper valve opening.
No. of LFG collection pipes
200 2012 2013 2014 2015
150
100
50
0 ≤ 10
≤ 30
≤ 50
≤ 70
≤ 90
≤ 110
≤ 130
≤ 150
≤ 170
>170
No. of adjustment in a year
Fig. 7. Valve adjustment frequencies
Fig. 7. Probability of adjustment on valve opening rate
4. CONCLUSIONS In order to suggest effective managment guidelines of LFG collection pipes, seasonal and
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
temporal variation of LFG collection has been analyzed. LFG collection was too heterogeneous that any statistical tendency was not found. Most of LFG collection pipes are not adjusted during monitoring process. LFG collection pipes that has valve opening from 20 to 45% was more likely to be adjusted at next monitoring. Consequently, LFG collection pipes need to be managed on the basis of each LFG collection pipes and set up of monitoring hiarrachy would save time and labor. Futher studies on factors for other environmental factors are needed to develop more detailed guidelines. AKNOWLEDGEMENTS This work is supported by Korea Ministry of Environment (MOE) as Waste to Energy-Recycling Human Resource Development Program and by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2017R1D1A1A02019215). We also thank for technical support of Institute of Construction and Environmental Engineering in Seoul National University and Sudogwon Landfill Site Mangement Corporation. REFERENCES Jeong, S., Nam, A., Yi, S.M., Kim, J.Y., 2015. Field assessment of semi-aerobic condition and the methane correction factor for the semi-aerobic landfills provided by IPCC guidelines, Waste Management 36, 197-203 Greenhouse Gas Inventory & Research Center of Korea (GIR) (2014). 2014 National Greenhouse Gas Inventory Report of Korea. p. 32. (In Korean). Korea Ministry of Environment, 2016. Generation and Treatment of Solid Waste in 2015. (in Korean) US Environmental Protection Agency (US EPA), 2009. Techinical support document for the landfill sector: proposed rule for mandatory reporting of greenhouse gases Conestoga-Rovers & Associates, 2010. Landfill gas management facilities design guidelines, British Columbia Ministry of Environment US Army Corps of Engineers (USACE), 2013. Landfill Gas Collection and Treatment Systems, available at: http://140.194.76.129/publications/. Sudogwon Landfill Site Management Corp., 2016. Sudogwon Landfill Statistics Yearbook 2016. (in Korean)
SUMMARY: In order to reduce greenhouse gas emission and produce renewable energy, installation of LFG collection system is increasing. Due to safety issue and stable power generation, the concentration of CH4 and O2 in LFG collection pipes are monitored regularly and the valve opening is adjusted to meet the guidelines. In this study, monitoring data of LFG collection pipes has been used to analyse spatial and temporal variation and suggest monitoring frequencies of LFG collection pipes. More CH4 is collected from landfill sections of fresh waste is landfilled. When fresh waste is landfilled, concentration of CH4 is increased causing increase of valve opening rate. However, there were some exceptions. Most of LFG collection pipes are not adjusted during monitoring process. LFG collection pipes that has valve opening from 20 to 45% was more likely to be adjusted at next monitoring. Therefore, further analysis on the factors for LFG collection would contribute to effective monitoring practices. 1. INTRODUCTION Landfill gas (LFG) mostly consists of carbon dioxide (CO2) and methane (CH4) (Jeong et al., 2015). As methane is one of six major greenhouse gases (GHG) and solid waste landfill is third largest anthropogenic methane source in Republic of Korea (GIR, 2014). On the other hand, LFG possesses high calorific value which can be utilized as renewable energy. In order to reduce greenhouse gas emission and produce renewable energy, installation of LFG collection system is increasing. 13 LFG utilization plants are installed and 160 million Nm3 CH4 is collected in 2015 in Republic of Korea (Korea Ministry of Environment, 2016). In order to operate energy generator of LFG safely and effectively, the concentration of CH4 in collected LFG need to be controlled. There are a few guidelines on the management of LFG collection pipes. US EPA (2009) suggested to monitor flow rate, CH4 concentration, temperature and pressure to secure stable energy generation. O2 concentration below 2.5 % is recommended to prevent fire within landfill (Conestoga-Rovers & Associates, 2010; USACE, 2013). Above mentioned guidelines suggest monthly monitoring of collection pipes. Due to lack of managment guidelines, field engineers of the Sudogwon landfill, the largest landfill in Repbulic of Korea, monitor LFG collection pipes and adjust valve openings every working day. Therefore, spatial and temporal variation of landfill gas collection has been analyzed to suggest proper management practices of LFG collection pipes.
Proceedings Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium/ 2 - 6 October 2017 S. Margherita di Pula, Cagliari, Italy / © 2017 by CISA Publisher, Italy
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
2. MATERIALS AND METHODS 2.1 Study sites The Sudogwon landfill site is the largest landfill where 47.7 % of landfilled solid waste is treated in 2015 in Republic of Korea (Korea Ministry of Environment, 2016). The Sudogwon landfill consists of two landfills, 1st landfill and 2nd landfill. The 1st landfill was closed in 2001 and the 2nd landfill started landfilling since 2000. More than 65 million ton of municipal solid waste has been landfilled and still under operation in the 2nd landfill of Sudogwon landfill (Sudogwon Landfill Site Management Corp., 2016). The 2nd landfill is divided into 25 sections (Fig. 1). 2.2 Monitoring and adjustment of landfill gas collection pipes LFG collection system has been installed in 2001 in 2nd landfill. Horizontal and vertical LFG collection has been installed. LFG in horizontal pipes is sent to 699 vertical LFG collection pipes. 699 vertical LFG collection pipes are controlled in 44 manifold stations. LFG collection pipes are monitored by every working day. LFG monitoring data from 2012 to 2016 has been used in the analysis.
Table. Monitoring data in the 2nd Sudogwon landfill Year
Date of monitoring (days)
No. of LFG collection pipes
Total No. of data
2012
241
699
168,459
2013
205
699
143,295
2014
245
699
171,255
2015
197
699
137,703
During monitoring of LFG collection pipes, the concentration of CH4, CO2 and O2 (%), temperature (℃), pressure (mmAq) and flow rate (m3/min) are monitored (Fig. 2). In order to secure stable power generation and prevent landfill fire, the valve of opening of LFG collection pipes was adjusted when the concentration of CH4 is below 48% or the concentration of O2 is over than 5%. The valve opening on LFG collection pipe can be controlled from 0% to 100% at intervals of 5%.
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
Fig. 1. Landfill sections and manifold stations in 2nd landfill
Fig. 2. Monitoring of LFG collection pipes
3. RESULTS AND DISCUSSIONS 3.1 Spatial variation of LFG collection The landfill is conducted successively for landfill sections in the 2nd Sudogwon landfill. Fig. 3 shows the age of landfilled waste at the top landfill layer. As decomposition of organic matters is considered as first order, the top-left landfill sections (E-4, F-4 and F-3) are expected to collect more CH4 than other landfill sections. F-4 and F-3 showed higher CH4 collection as expected (Fig. 4). However, central landfill sections showed relatively higher CH4 collection while the age of waste at top layer is old.
Fig. 3. The age of landfilled waste at the top layer in 2014
Fig. 4. Annual CH4 collected in 2014 (unit: 103 m3CH4/year)
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
Fig. 5. Monthly CH4 collected by landfill area in (left) Mar., (center) Jun., (right) Aug. 2014
3.2 Valve opening rate Valve opening rate indicates CH4 concentration in LFG collection pipes because valves are adjusted based on the concentration of CH4. Fig. 6 shows the average valve opening rate in each landfill section. Over four years of monitoring, valve opening rate tent to increase when new waste is landfilled. In the section C-2 and C-3 showed increase of valve opening rate from 40 to 100 % (day 130) when new waste is landfilled, respectively. However, there were some cases that valve opening rate didn’t increased despite fresh waste is landfilled. In the sections in line D, there were no significant increases in valve opening rate or decreased soon after landfill of fresh waste.
100 C-1 C-2 C-3 C-4
Valve opening rate (%)
80
60
40
20
0 0
100
200
300
400
500
600
700
800
900
1000
Time (day)
100
Valve opening rate (%)
80
60
40
D-1 D-2 D-3 D-4
20
0 0
100
200
300
400
500
600
Time (day)
Fig. 6. Valve opening rate of landfill sections in line C and F
700
800
900
1000
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
3.3 Adjustment of valve opening rate Valve opening is adjusted when the concentration of CH4 is below 48% or the concentration of O2 is over than 5% for stable energy production and safety. Average frequency of valve adjustment was 56.9 ± 42.8 times per year (Fig. 7). For one time monitoring, 71.8% of LFG collection pipes kept their valve opening rate and 19.9 % of LFG collection pipes adjusted 5% of opening rate. LFG collection pipes which have valve opening from 20% to 45% have more chances to be adjusted. Field engineers adjust valve opening for 5% per day. Consequently, total number of adjustment is large and adjustment for the LFG collection pipes for valve opening between 20% and 45% is frequent because it is on the process to find proper valve opening.
No. of LFG collection pipes
200 2012 2013 2014 2015
150
100
50
0 ≤ 10
≤ 30
≤ 50
≤ 70
≤ 90
≤ 110
≤ 130
≤ 150
≤ 170
>170
No. of adjustment in a year
Fig. 7. Valve adjustment frequencies
Fig. 7. Probability of adjustment on valve opening rate
4. CONCLUSIONS In order to suggest effective managment guidelines of LFG collection pipes, seasonal and
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
temporal variation of LFG collection has been analyzed. LFG collection was too heterogeneous that any statistical tendency was not found. Most of LFG collection pipes are not adjusted during monitoring process. LFG collection pipes that has valve opening from 20 to 45% was more likely to be adjusted at next monitoring. Consequently, LFG collection pipes need to be managed on the basis of each LFG collection pipes and set up of monitoring hiarrachy would save time and labor. Futher studies on factors for other environmental factors are needed to develop more detailed guidelines. AKNOWLEDGEMENTS This work is supported by Korea Ministry of Environment (MOE) as Waste to Energy-Recycling Human Resource Development Program and by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2017R1D1A1A02019215). We also thank for technical support of Institute of Construction and Environmental Engineering in Seoul National University and Sudogwon Landfill Site Mangement Corporation. REFERENCES Jeong, S., Nam, A., Yi, S.M., Kim, J.Y., 2015. Field assessment of semi-aerobic condition and the methane correction factor for the semi-aerobic landfills provided by IPCC guidelines, Waste Management 36, 197-203 Greenhouse Gas Inventory & Research Center of Korea (GIR) (2014). 2014 National Greenhouse Gas Inventory Report of Korea. p. 32. (In Korean). Korea Ministry of Environment, 2016. Generation and Treatment of Solid Waste in 2015. (in Korean) US Environmental Protection Agency (US EPA), 2009. Techinical support document for the landfill sector: proposed rule for mandatory reporting of greenhouse gases Conestoga-Rovers & Associates, 2010. Landfill gas management facilities design guidelines, British Columbia Ministry of Environment US Army Corps of Engineers (USACE), 2013. Landfill Gas Collection and Treatment Systems, available at: http://140.194.76.129/publications/. Sudogwon Landfill Site Management Corp., 2016. Sudogwon Landfill Statistics Yearbook 2016. (in Korean)
