While coal-fired power plants continue to be the primary target of carbon dioxide regulation, emissions of a lesser known but more potent greenhouse gas from the electric utility industry are being regulated for the first time in California.
Sulfur hexafluoride (SF6) is a colorless, odorless, non-toxic, and non-flammable gas that has been used in the electric utility industry in the United States since the 1950s. However, since SF6 has a 100-year global warming potential (capacity to heat the atmosphere) that is more than 22,000 times that of carbon dioxide and an atmospheric lifetime of 3,200 years, it is by far the most potent of all recognized greenhouse gases.
SF6 is primarily used in electricity transmission and distribution systems as an insulator and arc interrupter for circuit breakers, switchgear and other electrical equipment. Emissions of SF6 occur during equipment installation, servicing and disposal, as well as escaping through seals in older equipment. SF6 largely replaced flammable insulating oils – its advantages include allowing for more compact substations in urban areas. The U.S. Environmental Protection Agency (EPA) says that currently there are no available substitutes for SF6 in this application.
New Regulations for 2012
By virtue of a vote of its Air Resources Board in February, California became the first jurisdiction to formally regulate SF6 emissions from electrical equipment in the United States. Starting in 2012, equipment containing SF6 will be allowed to leak no more than 10 percent of its total capacity into the atmosphere. The cap will decline each year until it reaches the ultimate target of 1 percent of the SF6 capacity in 2020 – which equates to a 70 percent reduction of SF6 emissions from all electric utility applications in the state.
The regulations exempt several other uses of SF6, including medical uses, nuclear power plant testing and equipment calibration. Everyone else will be prohibited from purchasing, selling, owning or using SF6 in the state after January 2011. The Air Resources Board estimated that the rule would affect 75 utilities, government agencies and other owners of electrical equipment. The cost of implementing this measure has been estimated to be $4.5 million to $7 million over the 10-year period, which is anticipated to result in an increase in electricity rates of 1 to 2 cents per month per household, a minuscule amount.
Compliance will be achieved through plugging leaks, recycling the gas and refurbishing or replacing equipment. Through improvements in the leak rate of new equipment, refurbishing of older equipment and the use of more efficient operation and maintenance techniques, utilities can over time find more economical solutions to reduce SF6 emissions.
Actions at the Federal Level
The electric transmission and distribution industry has already been working with the EPA on this issue for more than a decade. A voluntary industry-EPA program called the SF6 Emission Reduction Partnership was initiated in 1999, with 49 charter partners from the electric utility industry. The program’s primary objective is to share information and resources to reduce SF6 emissions via cost-effective technologies and practices. Partners agree to estimate current emissions and annually inventory actual emissions using an established protocol; establish a strategy for replacing older, leakier pieces of equipment; implement SF6 recycling; and ensure that only knowledgeable personnel handle the gas.
Each partner submits annual progress reports to the EPA. The Partnership’s cumulative SF6 emission rates have dropped from 17 percent in 1999 to 6.5 percent in 2006. Quantitatively, this reduction prevented the loss of approximately 1.2 million pounds of SF6, or 12.84 million metric tons of carbon dioxide equivalent emissions, to the atmosphere. This also translates into an equivalent of $7.1 million to $10.7 million of avoided SF6 purchases to replace such losses. The Partnership has now grown to 81 members, representing more than 45 percent of the industry.
Meanwhile, the EPA has been busy developing its own mandatory regulatory regime to address SF6 emissions. The agency had originally proposed to include leaks of SF6 from electrical equipment in its mandatory reporting rule that came into effect on January 1, 2010, but chose to defer requiring annual inventories pending additional analysis of data collection procedures and methodologies. EPA published a proposed revision on April 12, 2010, that would require reporting on a systemwide (rather than facility) level, and anticipates finalizing this rulemaking in the fourth quarter of 2010.
Convergence of EPA and California Initiatives
The efforts and advances from EPA’s voluntary program will hopefully make compliance with the new California requirements more feasible. Five California utilities are members of the SF6 Emission Reduction Partnership. One reported that its SF6 leak rate had been reduced by more than 50 percent since 1998, while another noted a 32 percent emissions reduction since 2001.
It remains to be seen how much further California’s regulation of utility SF6 emissions may drive advancements in technologies and cost-effective leak detection and mitigation practices. Whatever the outcome, California has once again chosen to be the regulatory trailblazer for the rest of the country, this time for the most potent of all greenhouse gases.
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