Methane collection efficiency of horizontal landfill gas collectors.Abstract
Pumping test and closed flux chamber technique were used to evaluate the performance of horizontal landfill gas collection system at the Rachathewa sanitary landfill sanitary landfill: see solid waste. , Samutprakan, Thailand. Two investigated areas consisting of three horizontal extraction wells each with a total length of 150 meters with a well spacing of 15 m were used. The closed flux chambers were used to measure the surface landfill methane emissions before and during pumping tests. Pumping tests were done for a period of two weeks. The gas adjustment was tuned to maintain landfill gas (LFG LFG Landfill Gas
LFG Lincoln Financial Group (insurance & financial planning company)
LFG Looking For Group (Everquest)
LFG Lexical-Functional Grammar (computational linguistics) ) quality of greater than 50 % C[H.sub.4] and less than 2 % [O.sub.2]. Portable landfill gas analyzer and pre-calibrated orifice plates were used to control composition and collection rates of landfill gas from the collection system, respectively.
The average spatial methane emission rate without extraction process was 82 g/[m.sup.2]/d and with extraction process was 8.5 g/[m.sup.2]/d. The results showed that the spatial distribution of methane emissions without extraction process is very high and is reduced when the extraction process is applied. The efficiency of horizontal landfill gas extraction system was markedly above 80%. The collection efficiency from this study can be used for evaluation of landfill gas to energy projects. Furthermore, from the methane emissions data, it is recommended that in order to distribute suction force into the middle area to improve the collection efficiency, the position of wellhead well·head
1. The source of a well or stream.
2. A principal source; a fountainhead.
3. The structure built over a well.
1. should be offset about 10 to 15 meters from the end of collector. Thus, the collection of LFG by forced extraction would be an effective option in order to utilize LFG as well as reduce the global warming global warming, the gradual increase of the temperature of the earth's lower atmosphere as a result of the increase in greenhouse gases since the Industrial Revolution. and local air pollution problems.
Keywords: landfill gas; methane emissions; pumping test; flux chamber, horizontal collector.
Landfill gas (LFG) is formed as a natural byproduct by·prod·uct or by-prod·uct
1. Something produced in the making of something else.
2. A secondary result; a side effect.
Noun 1. of the anaerobic anaerobic /an·aer·o·bic/ (an?ah-ro´bik)
1. lacking molecular oxygen.
2. growing, living, or occurring in the absence of molecular oxygen; pertaining to an anaerobe. decomposition of wastes in landfills. Typically, LFG is composed of about 50% methane, 45 % carbon dioxide carbon dioxide, chemical compound, CO2, a colorless, odorless, tasteless gas that is about one and one-half times as dense as air under ordinary conditions of temperature and pressure. , and 5% of other gases including hydrogen sulfides and volatile organic compounds volatile organic compound Environment Any toxic cabon-based (organic) substance that easily become vapors or gases–eg, solvents–paint thinners, lacquer thinner, degreasers, dry cleaning fluids . LFG is thought to be released from six months to two years after waste is placed in the landfill . Methane is a potent greenhouse gas greenhouse gas
Any of the atmospheric gases that contribute to the greenhouse effect.
greenhouse gas (GHG GHG Greenhouse Gas
GHG Governor's Horse Guard (various locations) ), with 21 times the global warming potential Global warming potential (GWP) is a measure of how much a given mass of greenhouse gas is estimated to contribute to global warming. It is a relative scale which compares the gas in question to that of the same mass of carbon dioxide (whose GWP is by definition 1). of carbon dioxide. Estimates indicate that about 13% of methane emissions released to the atmosphere in 2000 were from landfills .
LFG can contribute to malodor and present health and safety hazards if it is not well-controlled. To recover its energy value and minimize its pollutant pol·lut·ant
Something that pollutes, especially a waste material that contaminates air, soil, or water. effects, many landfill sites have installed LFG recovery and utilization systems. Recovery of 100% of the generated gas is generally considered infeasible due to the permeability of wastes and recovery system inefficiencies as well as installation timing. There is lack of information about the recovery efficiency of LFG. In Thailand, the absence of data on recovery efficiency makes it difficult for landfill site owners and developers to set realistic target and establish reference for the use of LFG for energy projects.
The purpose of this study is to evaluate the performance of horizontal landfill gas collection system at the Rachathewa sanitary landfill, Samutprakan, Thailand by using pumping tests and closed flux chamber technique. Two major aspects have been studied--C[H.sub.4] emission rates in the presence and absence of gas extraction.
The Rachathewa sanitary landfill site is located 30 km east of the Bangkok area and receives about 3,500 tons/day of municipal solid waste “Municipal waste” redirects here. For other uses, see Municipal waste (disambiguation).
Municipal solid waste (MSW) is a waste type that includes predominantly household waste (domestic waste) with sometimes the addition of commercial wastes collected by a . The site operated from 2000 to 2003 and occupies 40 hectares including a landfill and ancillary facilities necessary to support its operation.
The experimental cell is located at the one part of disposal area. The disposal area has been filled in three zones and the waste has primarily been placed using loaders, bulldozers, and a landfill compactor. At the present time (2006), there are approximately 1,902,380 metric tons of solid wastes in place.
LFG Collection System
The two common ways to recover LFG are vertical extraction wells and horizontal collectors. The standard and most commonly used is the vertical extraction well. The well is drilled into the landfill at spacing typically ranging from 45 to 90 m. Two to 8-inch diameter pipes (typically PVC PVC: see polyvinyl chloride.
in full polyvinyl chloride
Synthetic resin, an organic polymer made by treating vinyl chloride monomers with a peroxide. or HDPE HDPE
high-density polyethylene ) are placed in the holes, which are backfilled with 1-inch-diameter, or larger, stones. The pipe is perforated in the lower section where the LFG is collected.
Horizontal extraction collectors or trenches may be installed instead of/or in combination with vertical wells to collect LFG. They consist of excavated trenches (similar to a pipeline trench) which are backfilled with permeable permeable /per·me·a·ble/ (per´me-ah-b'l) not impassable; pervious; permitting passage of a substance.
That can be permeated or penetrated, especially by liquids or gases. gravel. Perforated, slotted, or alternating diameters of pipe are installed in the trench. Horizontal extraction collectors are less expensive than vertical extraction wells and are particularly suitable for installation in active filling areas. The advantages of a horizontal extraction collector are low effects from high leachate leach·ate
A product or solution formed by leaching, especially a solution containing contaminants picked up through the leaching of soil. level problem in landfill, less obstruction for landfill operations caused by collector headers and easy installation. The disadvantages of a horizontal extraction collector are high effects from waste settlement and a low recovery efficiency rate per well .
The LFG collection system should be used in concert with good leachate management practices. Leachate accumulation within the refuse can dramatically impact the rate of LFG recovery because liquid in the extraction well and collection trenches effectively restricts their ability to collect and convey LFG .
Field experiences indicate that horizontal extraction collectors are more suitable for Thai landfills compared to vertical extraction wells . The main purpose of using the horizontal extraction well is the very high leachate level in Thai landfills. Figure 1 provides a schematic of the typical horizontal collectors at the site.
[FIGURE 1 OMITTED]
Size of Experimental Cell
The two investigated areas had three horizontal collectors with a total length of 150 meters. Spacing between the wells was 15 meters. Each cell covers a footprint area of approximately 45m x 50m. The cell covers three horizontal gas extraction wells. The collector extended from the outside edge into the landfill with a 3% slope. At the outside edge, leachate drainage was provided using a PVC pipe. The leachate drain was 12 meters long and had a diameter of 100 mm. The location of two investigated areas is shown in Figure 2.
[FIGURE 2 OMITTED]
Methane Emissions Rate
Gas samples were collected using a closed acrylic chamber (length 40 cm, width 40 cm and height 10 cm) that was equipped with an electronic thermometer and a sampling port. The bottom of the chamber was placed on the soil surface with 5 cm inserted into the soil. The height between soil surface and bottom level of sealed trench of basement was measured. To protect from air disturbance, the water was filled to the trench of basement. The flux chamber was placed to the basement and gas sampling started. The concentration of methane within the box was measured at short time intervals (1 minute) by syringe and conveyed to the vacutainer over a period of 4 minutes.
Methane concentration was measured by a Shimadzu 14A gas chromatograph gas chromatograph
An instrument used in gas chromatography to separate a sample of a volatile substance into its components. (Shimadzu Co., Japan). The rates of methane emissions were calculated by fitting linear regression Linear regression
A statistical technique for fitting a straight line to a set of data points. to the difference in the methane concentrations and adjusting for the chamber volume and area covered following the equation 1.
Q = V/A V/A Various Artists (dc/dt) (1)
Q = flux density flux density
The rate of flow of fluid, particles, or energy per unit area. of the gas (mg.[m.sup.-2][s.sup.-1])
V = chamber volume ([m.sup.3])
A = chamber footprint ([m.sup.2])
dc/dt = rate of change of gas concentration in the chamber with time (mg.[m.sup.-3][s.sup.-1])
For measuring methane emission rates, 100 sets of closed flux chambers were installed on the final cover soils at each measurement site (both with and without extraction process). The chambers were placed in a grid pattern in the 1st and 2nd areas having dimensions (x - y) of 7.5 m x 16.7 m and 7.5 m x 10 m, respectively.
LFG extraction by root blower at the Rachathewa power plant had been performed for a period of two weeks. The manifold at each wellhead was tuned to maintain landfill gas (LFG) quality greater than 50 % C[H.sub.4] and less than 2 % [O.sub.2]. The composition and production rate of landfill gas from the well system was measured everyday using a portable LFG analyzer (GEM 2000) and pre-calibrated orifice plate.
Spatial Interpolation interpolation
In mathematics, estimation of a value between two known data points. A simple example is calculating the mean (see mean, median, and mode) of two population counts made 10 years apart to estimate the population in the fifth year.
Mapping software Surfer by Golden Software was used to analyze the geospatial distribution. Kriging model was applied to map the results, and the volumetric volumetric /vol·u·met·ric/ (vol?u-met´rik) pertaining to or accompanied by measurement in volumes.
Of or relating to measurement by volume. value of the contour map was produced by volume and area integration algorithms in Surfer.
Results and Discussion
The results showed that the methane emissions without extraction process were in the range of 1.93 to 351.44 g/[m.sup.2]/d in the 1st area and 0.51 to 754.74 g/[m.sup.2]/d in the 2nd area. The spatial average methane emissions without extraction process were 66.48 and 97.67 g/[m.sup.2]/d for the 1st and 2nd area, respectively. The methane emissions with extraction process ranged from 0.00 to 24.65 g/[m.sup.2]/d in the 1st area and 0.00 to 268.09 g/[m.sup.2]/d in the 2nd area. The spatial average methane emissions with extraction process were 4.18 and 12.91 g/[m.sup.2]/d for the 1st and 2nd area, respectively. The efficiencies of the collector ranged from 9.93 to 100 % and 5.96 to 100 % for the 1st and 2nd area, respectively. The overall spatial efficiencies of horizontal landfill gas extraction system were about 82% in both the areas.
Methane emissions in the 1st and 2nd area with and without extraction process are shown in Figure 3. The efficiencies of horizontal landfill gas extraction system in these two areas are presented in Figure 4.
[FIGURE 3 OMITTED]
[FIGURE 4 OMITTED]
These tests showed that the spatial distribution of LFG emissions was lower in the 1st area than in the 2nd area. This trend was also observed when LFG was being extracted. However, in the latter case, the spatial distributions of LFG emissions were lower than without extraction for both areas.
Utilization of geospatial methodologies to determine the whole landfill emission rates in both areas showed that the amounts of LFG emissions from the landfill surface were about 20% higher than the amount of LFG generation with extraction process. When LFG was extracted by blower, the LFG emissions rates rapidly decreased. In order to improve the collection efficiency it is recommended that the position of wellhead should be offset about 10 to 15 meters from the end of collector. This will improve the suction force distribution in the middle of extraction area.
Using pumping tests and closed flux chambers technique to evaluate the performance of landfill gas extraction system and methane emissions revealed significant methane emissions and the effect of LFG extraction on methane emissions. The results showed that the spatial distribution of methane emissions without extraction process is higher than when the extraction process is applied. The spatial average methane emissions without extraction process were 66.48 and 97.67 g/[m.sup.2]/d in the 1st and 2nd area respectively. With extraction process, they were 4.18 and 12.91 g/[m.sup.2]/d in the 1st and 2nd area respectively. The average spatial efficiencies of horizontal landfill gas extraction system, determined from the collection efficiency at each sampling point, were about 82%.
Furthermore, from this obtained information, the surface LFG emissions patterns can be progressively developed in the extraction well system design process. In order to improve the collection efficiency it is recommended that the position of wellhead should be offset about 10 to 15 meters from the end of collector to improve the suction force distribution into the middle of extraction area.
The conservative value for LFG recovery by using horizontal LFG collection system for evaluation in landfill gas to energy project planning project planning - project management can be 80%. This will significantly reduce the environmental impact on landfill emissions. Thus, the utilization of LFG by forced extraction would be a very good solution to maximize LFG recovery and so to use CH4 as biofuel bi·o·fuel
Fuel such as methane produced from renewable resources, especially plant biomass and treated municipal and industrial wastes.
bi to mitigate GHG emissions as well as reduce odors Odors
Medicine. the absence of the sense of smell; olfactory anesthesia. Also called anosphrasia. — anosmic, adj.
bad breath; an unpleasant odor emanating from the mouth. in neighborhoods surrounding the landfill .
 U.S. Environmental Protection Agency Environmental Protection Agency (EPA), independent agency of the U.S. government, with headquarters in Washington, D.C. It was established in 1970 to reduce and control air and water pollution, noise pollution, and radiation and to ensure the safe handling and (EPA EPA eicosapentaenoic acid.
n.pr See acid, eicosapentaenoic.
n. ), 1997, "Opportunities for Landfill Gas Energy Recovery in Colorado," EPA 430-B-97-036, Washington, DC: EPA.
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 The World Bank, 2004, "Handbook for the Preparation of LFG to Energy Projects in Latin America Latin America, the Spanish-speaking, Portuguese-speaking, and French-speaking countries (except Canada) of North America, South America, Central America, and the West Indies. and the Caribbean," Available online at: www.bancomundial.org.ar/lfg
 Eam-o-pas, K. and Panpradit, B., 2003, "Landfill Gas Recovery Using Horizontal Collectors in Thailand," Fourth International Conference of the ORBIT Association, Perth, Australia Perth may refer to:
 Wang-Yao, K., Towprayoon, S. and Wangyao, P., 2005, "Landfill Gas to Energy in Thailand: Case Study at Rachathewa Power Plant," Third Eco-Energy and Materials Science and Engineering Materials science and engineering
A multidisciplinary field concerned with the generation and application of knowledge relating to the composition, structure, and processing of materials to their properties and uses. Symposium, Chiangmai, Thailand.
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Komsilp Wang-Yao (1) *, Sirintornthep Towprayoon (1), Chart Chiemchaisri (2), Shabbir H. Gheewala (1) and Annop Nopharatana (3)
(1) The Joint Graduate School of Energy and Environment, King Mongkut's University of Technology Thonburi King Mongkut's University of Technology Thonburi (KMUTT, มหาวิทยาลัยเทคโนโลยีพระจอมเกล้าธน$ , Bangkok, Thailand 10140 E-mail: email@example.com, firstname.lastname@example.org and Shabbir_g@jgsee.kmutt.ac.th
(2) Department of Environmental Engineering, Faculty of Engineering, Kasetsart University Kasetsart University (Thai: มหาวิทยาลัยเกษตรศาสตร์) the first agricultural university in Thailand, was established on February 2, 1943 with the prime , Bangkok, Thailand 10900 E-mail: email@example.com
(3) Pilot Plant Development and Training Institute, King Mongkut's University of Technology Thonburi, Bangkok, Thailand 10150 E-mail: firstname.lastname@example.org