The capture of methane from waste disposal facilities can have a significant impact on the reduction of anthropogenic methane emissions. In the United States, more than six hundred facilities are capturing approximately 26.3 MMTCO2e methane annually (U.S. EPA, 2015). The importance of the capture is two-fold: reduction of greenhouse gases and the exploitation of a beneficial energy source.
Yet methane capture efficiencies have been moderate due to many logistical issues. Few methods currently exist to rehabilitate marginally producing extraction wells at landfills. This study was designed to test whether post-perforation technology, invented in 2009, is effective in increasing the efficiency of gas capture from marginally producing wells.
This study examined the effectiveness of post-perforation technology to improve the environmental and energy benefits associated with additional methane capture. Post perforation technology was designed and developed to rehabilitate marginal extraction wells. The technology creates new openings to allow more methane to enter an extraction well. Prior to this technology low yield or marginal extraction wells were abandoned and new extraction wells were drilled and installed.
The study consisted of gathering data from nine existing municipal solid waste facilities that had extraction wells previously post-perforated. After review, five of the nine facilities were selected for the study. For adequate sample size, facilities with nine or more post-perforated extraction wells were included in this study. The number of post perforated wells from the five facilities ranged from 9 to 19. All facilities were from Texas or Florida. Post-perforation at these facilities was conducted between September 2009 and October 2014. The number of methane extraction wells from the five facilities ranged from 49 to 138. Measurements for % methane (CH4), initial flow (standard cubic feet per minute scfm) and adjusted flow (scfm) were obtained at each extraction well at least on a monthly basis. One year’s worth of data was obtained at each facility, six months prior and six month after post-perforation for each extraction well.
All extraction at each of the five facilities wells were categorized into one of three groups for analyses based on the following criteria. If the initial flow was ≤2 (scfm) or the % methane was ˂50% the extraction well was a candidate for post-perforation. If this type of extraction well was subsequently post-perforated, it was categorized into group 1, but if not selected for post-perforation it was categorized into group 2, serving as a control group within that landfill. However, if the initial flow was >3 (scfm) the extraction wells was categorized into group 3. The total sample size for group 1 was 67, group 2 contained 165, and group 3 contained 261 extraction wells.
The results of the analyses demonstrated a statistical effect after post-perforation on the initial flow (scfm) and on adjusted flow (scfm) in Group 1, the treatment group.
The mean initial flow after post-perforation increased from 16.9 to 28.5 scfm (t = 3.05; p = 0.016; n=67), and the adjusted flow increased from 16.8 to 30.1 scfm (t = 3.66; p = 0.002; n=67). Group 2 and Group 3 mean values also increased after the time of perforation of Group 1 wells, but with not as large an increase in either variable.
The added methane capture from landfills yielded substantial environmental and energy benefits. Four facilities yielded mean flow increases of methane at 125, 157, 120 and 558 scfm, for a total 960 scfm methane. The increase from those four facilities represents a total equivalent emission reduction of 0.1329 MMTCO2E/year, equivalent to 5,336 tons of CH4/year or 13,171 tons of CO2/ year. The energy benefit from 960 scfm could heat 3,315 homes for a year.
This study demonstrates that post-perforation does increase the capture of methane in extraction wells at municipal solid waste facilities. Furthermore, this study demonstrated the advantages to be gained from any methodology or innovation that decreases fugitive emissions from landfills. Further research is required to increase the efficiency of methane capture. Industry change is slow due to the inconsistencies between federal, state and local regulatory requirements, but this study helps point the way.
| Identifer | oai:union.ndltd.org:harvard.edu/oai:dash.harvard.edu:1/24078375 |
| Date | 11 January 2016 |
| Creators | Stamoulis, Stefan |
| Publisher | Harvard University |
| Source Sets | Harvard University |
| Detected Language | English |
| Type | Thesis or Dissertation, text |
| Format | application/pdf |
| Rights | open |
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