Natural Gas & The Low-Carbon Economy


encroach on other regional demands for water. Gas companies have begun experimenting with reusing produced water in subsequent fracturing jobs, a practice that could greatly reduce water consumption, transportation costs, emissions, and contamination risks. The extraction and transport of


natural gas also generates local air pollution and greenhouse gases. Natural gas itself is made up mostly of methane, a greenhouse gas 23 times more potent than CO2. During the production process, natural gas may be intentionally vented or unintentionally leaked. According to the EPA, natural gas systems were responsible for 178.9 million metric tons of CO2-equivalent of methane in 2008 – 61% of the energy sector’s methane emissions and 24% of total US methane emissions. Efforts are underway to capture this methane, including the EPA’s Natural Gas STAR program, which has worked with industry to reduce methane emissions from the US gas industry by 822 billion cubic feet, or 334 million metric tons of CO2-equivalent, since 1993.


Produced water or natural gas can contaminate underground


aquifers if improperly lined and cased wellbores to leak under the pressure of hydraulic fracturing. In 2007 in Bainbridge, Ohio, a well that had been drilled almost 4,000 feet into a tight sand formation through a layer of gas-bearing shale was not properly sealed with cement, allowing gas from the shale layer to leak into an underground source of drinking water. The methane eventually built up until an explosion in a resident’s basement alerted state officials to the problem. The sheer volume of water consumed during hydraulic fracturing could make unconventional gas production costly and unsustainable in many areas of the world that are water-constrained. Each well requires an average of 2-4 million gallons of water to fracture, depending on the characteristics of the shale formation. Although these volumes are significant, the Department of Energy estimates that they will represent less than 1% of all water usage in each basin. Nevertheless, producers must work with regulators to ensure that shale gas production does not


120 Aside from methane, the natural gas production process


also emits CO2 and other air pollutants. Diesel-powered compressors, which enable gas to be transported via pipeline, emit significant amounts of CO2 and smog-forming pollutants if they are not equipped with control technologies. Diesel fuel, drilling equipment, and water for hydraulic fracturing all must be trucked to drilling sites, adding additional emissions from vehicle exhaust. An Environmental Defence Fund study found that oil and gas production in the Barnett shale basin generates more smog-forming compounds than motor vehicles in the five counties it occupies, as well as high levels of air toxics, and greenhouse gases equivalent to the expected impact from two 750 MW coal-fired power plants. These could likely be reduced significantly if pollution controls were required. And if widely dispersed unconventional resources allow gas to be produced closer to the point of use, the emissions associated with transporting it could be significantly reduced. Increased seismic activity from hydraulic fracturing is


worldPower 2010


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