STRATEGIES AND TECHNOLOGIES AVAILABLE TO CONTROL GREENHOUSE GASES
| Jurisdiction | United States |
(Jan 2015)
STRATEGIES AND TECHNOLOGIES AVAILABLE TO CONTROL GREENHOUSE GASES
Partner, Air Quality & Climate Change
Environmental Resource Management (ERM)
Houston, Texas
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LESLIE COOK WONG, Partner, Air Quality and Climate Change, Environmental Resources Management in Houston, Texas, is a licensed attorney (Texas) and experienced in air and GHG regulatory analysis and advocacy, agency negotiations, compliance program development, and permitting. She brings to ERM over 20 years of experience in the oil and gas, landfill, renewable power, traditional power, and manufacturing sectors from a mix of prior industry and consulting roles. In addition to developing and implementing the GHG management and sustainability reporting programs for a major North American waste and recycling company as its Director of GHG Programs, she has developed and implemented successful air regulatory change initiatives, GHG PSD permitting efforts, NOx and GHG offset generation and marketing projects as well as Energy Management Information System (EMIS) implementation projects. More recently, in her past consulting roles, she led firm branding and marketing initiatives as well as firm recruiting efforts.
GHG Reduction Technologies for Oil and Gas Production
Methane is the second most prevalent anthropogenic (emitted from human activities) greenhouse gas (GHG) in the United States, with carbon dioxide being the most prevalent. Nevertheless, in 2012, methane accounted for only about nine percent of all U.S. GHG emissions. While comprising a small percentage of total emissions, methane is a much more potent GHG than carbon dioxide, meaning that it is more efficient at trapping solar radiation. Methane has a global warming potential of 25, which means that one pound of methane has 25 times the capacity to trap solar radiation as one pound of carbon dioxide.1
While most people associate methane with its fossil fuel form, natural gas, it is much more prevalent as part of the natural carbon cycle. Methane is generated when complex organic materials decay in a low-oxygen environment. Complex organic materials typically decay into carbon dioxide in a higher-oxygen environment. This anaerobic decay occurs in nature when plant material decays in a saturated wetland (ancient forms of which are the origin of fossil fuel natural gas) and when food is broken down in the digestive systems of animals. The carbon cycle is referred to as a cycle because the carbon released into the atmosphere by organic decay is taken in by plants to support photosynthesis, then the plants either die and decay or are eaten, and the carbon is released again. Carbon is neither gained nor lost in this cycle unless the cycle is disrupted by long term carbon sequestration (reducing carbon load) or by release of carbon that was sequestered long ago (fossil fuel production and use).
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Globally, about 60 percent of methane emissions come from human activity, including both human management of natural processes and industry. Methane from animal digestion occurs in a much more concentrated and aggressive form in managed agriculture than in nature. In fact, the largest source of methane emissions in the U.S. is enteric fermentation (farm animal digestion), which, in 2012 accounted for roughly 25 percent of U.S. methane emissions. Then, also associated with animal husbandry, another 9 percent were associated with agricultural manure management.2 Still more methane originates from human management of the natural organic decay of waste; specifically, from wastewater treatment/sewage plants and landfills.
Finally, methane emissions are associated with the oil and gas industry. Methane emissions are associated with the production of both natural gas and oil, as well as their processing and transportation.3 In 2012, these emissions comprised approximately 23 percent of total U.S. methane emissions.
While by no means the dominant source of methane emissions in the U.S., the oil and gas industry emits enough methane to be worthy of efforts to reduce emissions. It is relevant that, of the largest sources of methane emissions, the oil and gas industry is the only source for which methane is one of the two primary commodities that it produces. Where methane is an undesired by-product for agriculture and waste management, it is a primary commodity for the oil and gas industry, providing a strong business motivation to manage and minimize emissions. For the oil and gas industry, methane released is money unearned and market share lost, unless, of course, collection of the methane is prohibitively costly, unsafe or simply infeasible. Following is a discussion of available technology that can be employed to reduce oil and gas industry methane emissions, with comments on their cost, feasibility and safety issues.
1) Oil and Gas Production Methane Capture and Management:
The most obvious avenue for reducing methane emissions from the oil and gas industry is to go right to source and reduce the amount of natural gas lost during production, processing
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and transportation. This is easier said than done, because so many sources of oil and gas industry methane emissions are fugitive by nature rather than point source. Point source emissions are those that are released through a stack or other conduit, allowing for attachment of measurement and control devices. Fugitive emissions are those that are released from sources that cannot be redirected to a stack because they are unintended, very small or located over an area too large to be fitted with a stack. These include equipment leaks and losses from the ground or wells during drilling and well completion. Because fugitive emissions, by definition, cannot be feasibly collected, the only means for their control is prevention.
Even point source emissions of methane are not without collection and control problems. The biggest and most intractable problem associated with reduction of GHG impacts from the oil and gas industry is what to do with the collected methane if a sales gas line is not available at your site. The reality of oil production is that, until the last few years, it has been traditional to release methane associated with oil production to atmosphere or to flare it. Sales gas lines were not installed, and new pipelines are very long-term projects requiring significant financial investment, engineering, land use planning and infrastructure development. If there is not potential for a new pipeline to see sufficient use to provide payback for its inventors, the pipeline will not be developed. One solution to the pipeline problem is liquefying or compressing the gas to allow for containerization and vehicular transportation, but these technologies are very energy intensive and not practical for installation in areas without utility service, which applies to most sites without a sales gas pipeline. Unless the price of natural gas increases to the point that pipelines and/or processing equipment can be supported, flaring may be the only option.
Following is a brief discussion of the various technologies that can be applied to reduce oil and gas industry methane emissions, including both fugitive and point source:
a. Leak Detection and Repair:
One source of methane emissions from the oil and gas industry is leaking equipment. A lead detection and repair program provides for a formalized process to find leaks and repair them. Equipment subject to leaking includes flanges that join pipes together, valves that control product flow, pumps that move product and seals in compressors that compress collected natural gas; basically, any connection between pieces of equipment in which a gap can form and allow gas to escape.
The three most commonly used leak detection tools are catalytic gas detectors, infrared (IR) cameras and tunable diode lasers. A catalytic gas detector takes a small sample of air and introduces it to a catalyst that is sensitive to organic gases. The
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detector reacts when methane or other organic gases are introduced, indicating a leak. An IR camera is an optical gas imaging technology that uses infrared light which reflects off methane emissions, where visible light does not. Tunable diode laser absorption spectroscopy (TDLAS) uses a laser beam to measure a specific gas that crosses its path. Like IR cameras, TOLAS cameras identify methane by its particular light absorbing properties. All of these technologies can be handheld for conducting routine inspections, and the camera and laser can be mounted permanently to allow for continuous monitoring.
Use of cameras and lasers is very expensive because the units themselves and their maintenance are expensive units and they require highly trained staff to operate them. Even though catalytic gas detectors are not as expensive to buy and maintain, they require close contact to the potential emissions source to operate, meaning that the operator must engage in a time consuming exercise of taking many samples over a large area. This proximity can also create a safety risk if hydrogen sulfide gas (a highly toxic gas frequently associated with natural gas and oil) may be present or if the equipment to be measured is in a location that is dangerous to reach. Not that this expense is not rewarded by generation of additional useable product, because this is a means to minimize fugitive emissions, not collect point source emissions. Also, it does not net significant emissions reductions at well-run facilities, as it captures only very small leaks, because good operating and observational practices will detect large leaks before a monitoring event can occur.
...Regulatory leak detection and repair programs tend to be very strict and very burdensom, requiring multiple rounds of sampling, repair and
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