Utility companies and other users of Continuous Emissions
Monitoring (CEM) calibration gases often mistakenly consider
them a commodity, making price the primary purchase
consideration. Consequently, many are willing to settle for
calibration gases that are less accurate than premium
calibration gases, as long as they are also less expensive.
But many companies are beginning to see that buying less
expensive and potentially inaccurate CEM calibration gases may,
ironically, lead to losing hundreds of thousands or millions of
dollars! This is because the use of inaccurate calibration gases
often leads to the overstatement of emissions that could
otherwise be claimed as valuable emission credits which are
trading at values ranging from $700 to $2,500 per ton.
For instance, if a company uses a calibration gas mixture that
has been inaccurately manufactured and certified with a 100 ppm
tag value, but in reality contains only 96 ppm, that company
would unwittingly calibrate its CEM incorrectly, and overstate
its emission levels. Noting the image below, this inaccurate
calibration gas would eventually lead to tons of lost emission
credits that could have been sold, banked for future use, or
traded for significant dollars. Now, they are lost forever.
Accurate CEM calibration gases not only allow companies to
comply with EPA standards, but ultimately save significant
amounts of money in emission credits that might otherwise be
lost.
Failing to Measure Up
EPA regulations, as stated in the Clean Air Act of 1990, require
that protocol gases used to calibrate CEMs for Nitric Oxide or
Sulfur Dioxide (SO2) emissions be within ±2% of the accuracy
value as stated by the manufacturer on the mixture’s certificate
of analysis, or “tag” to comply with the EPA-mandated 7 – Day
Drift test. However, in a recent EPA blind audit, in which three
cylinders of calibration gases were bought from fourteen
different specialty gas manufacturers, it was found that 43% of
the vendors (6 of 14) failed to comply with the ±2% accuracy
requirement. The inaccuracies, in fact, ranged from 2% to as
high as 8%.
If the CEM error rate due to calibration is, between 2% and 8%,
then America’s acid rain utilities could be overstating
emissions by 82,050 to 328,203 tons of SO2 each year. With the
SO2 current market value at $700 per ton, this results in
$57,435,000 to $229,742,100 lost potential emission credits this
year – with the utility companies that use unacceptably
inaccurate calibration gases, such as those produced by the 43%
of vendors who failed the blind audit, bearing much of that loss.
The Cost of Inaccuracy
In order to fully understand the significance of these numbers,
imagine a utility company with a total SO2 Allowance Trading
System (ATS) credit of 400,000 tons for one year, but which also
used calibration gases that were actually 2% higher than the tag
value. That company would likely be overstating emissions by
8,000 tons (400,000 tons x 2%), which, at a value of $700/ton,
means it would be losing over $5 million in allowance credits
which could have been banked or sold that year. Companies using
calibration gases bought from vendors who failed the blind
audit, and whose gases therefore exceed the 2% accuracy
requirement, stand to lose even more.
Such a gross loss of potential trading credits clearly
overshadows the higher initial cost of accurate CEM calibration
gases. This year’s blind audit reveals the scope of the problem
of inaccurate gases, and utility companies would do well to take
notice. The companies could not see the difference because they
calibrated their CEMs based on the tag values of these
calibration gases. This problem is one which is only detectable
after an annual or semi annual Relative Accuracy Test Audit
(RATA) as mandated by EPA.
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