Air Quality Testing FAQs at Seneca Sustainable Energy

August 22, 2013

The following article appeared in the Register Guard on Sunday August 18, 2013:

By Richard Re

For The Register-Guard

On July 17, The Register-Guard ran a front-page article on Seneca Sustainable Energy’s request for a modification of our Lane Regional Air Protection Agency air contaminant discharge permit for our state-of-the-art renewable energy facility.

Many facets of the article were inaccurate, misleading and unfairly cast our operations in a poor light. I explained to the reporter that air quality permitting is a complicated regulatory field. I hope that is the reason the article contained so much misinformation.

To begin, I want to make clear that Seneca Sustainable Energy has not been “caught” emitting too much of anything. As reported by The Register-Guard, we have had three regulatory issues, all self-reported. One dealt with a report that was filed late, and the second dealt with exceeding the volume of lumber that our sawmills were permitted to dry; neither of these issues dealt with excess emissions.

The third issue has been the most frustrating and the most complicated. It involves the challenge of measuring particulate emissions at extremely low levels. Conventional tests we were required to perform could not accurately measure our particulate emissions because they are so low. This was not known when we received our permit to construct the plant.

Verifying that we are meeting the permitted emission levels was a two-year process.

In 2009, LRAPA issued to Seneca an air permit that the federal Environmental Protection Agency lauded as the best-controlled project in the Pacific Northwest, with particulate emissions less than 40 percent of those at comparable facilities that had recently been given permits.

There are two kinds of particulates — the kind that is a solid when emitted (referred to as “filterable particulate”) and the kind that is a gas when emitted (called “condensable particulate”). Seneca emits both kinds, and it was required by its permit to test for both, add them together, and then compare that sum to the limit allowed by the permit. The permit identified the testing methods to be used. While testing for filterable particulate is a well-established science, the testing methods for condensable particulate are still developing.

This is nowhere more true than when trying to measure very low levels of particulate in an exhaust stream that employs the type of emission control device used by Seneca to reduce its emissions of nitrogen oxides. There are defects in the common test methods that result in misidentifying a small amount of the exhaust air as condensable particulate. Between the time that the Seneca plant’s permit was issued and the time it started operation, the knowledge of these test defects increased significantly.

When Seneca started up its boiler, initial test results showed we met all of the standards except for particulate emissions. But we now know the initial test results for emissions were wrong. The filterable particulate emissions were extremely low due to the advanced emission controls employed at the plant. The condensable particulate emissions were identified as being higher than anticipated. Independent experts readily identified this as a problem with the test method.

Over the next year, Seneca performed three sets of emission tests using more advanced EPA methods than were contemplated when the permit was issued to prove that what looked like elevated condensable emissions were actually false positives attributable to defects in the old test methods. The more advanced and accurate tests unequivocally demonstrated that the plant was and always has been in compliance with the particulate limits in its permit.

However, there was a short period of time before the first round of advanced test method data was available when it was unknown whether the test emission readings were false positives resulting from nitrogen oxide controls or actual emissions.

After lengthy discussions with LRAPA, it was jointly concluded that until we were absolutely certain that the test results were false, the most environmentally responsible pathway was to turn off the nitrogen oxide emission control equipment for a period in the fall of 2011, until it was proven that this control equipment was not causing particulate emissions. This was deemed appropriate because nitrogen oxide emissions are of greatest concern during hot summer days, and of considerably less concern in the fall and winter. Particulate, by contrast, is typically of greatest concern as you enter the time of year when wood stoves are in use.

Although this was an agreed-upon strategy, Seneca still was technically in violation of its short-term nitrogen oxide limit (but not its rolling 12-month limit) until the test results vindicated the plant. Therefore, Seneca Sustainable Energy agreed in advance to pay a penalty to LRAPA for that exceedance. Seneca has never been subject to a penalty for excess particulate emissions, because it has never exceeded that limit.

So why, if we have now proven that the plant meets its originally permitted particulate emission limits, are we asking for an increase from 0.008 pounds per million British thermal units to 0.010 pounds per million Btu?

Multiple tests were conducted to verify that we meet our permitted particulate emission levels. Although our tests all show compliance with the current limit, the emission rates vary from test to test. This is mainly due to the complexity of the new testing methods. This variation is important when the emission levels are so low that we are pushing the boundaries of what the laboratory methods can detect.

Nobody questions that Seneca installed the most advanced particulate controls in the country for a boiler of this type. The EPA even sent a letter of commendation. However, our permit limit is supposed to reflect the maximum capacity of our advanced particulate controls “taking into account variability.” Sometimes that means a limit must be adjusted after operation starts and the regulatory authorities are able to see how the emission controls perform. Such changes are not unusual where a source of emissions proposes an aggressive improvement to the state of the art — exactly what Seneca did when it proposed its advanced particulate controls.

That is why Seneca is now requesting a small increase to its particulate emission limit. It is not because the plant is exceeding its current limit or that Seneca intends to increase emissions. Even with this change to its limit, Seneca will continue to represent the best-controlled source of its type nationwide.

It is also important to note another significant permit change. Seneca has actually requested that LRAPA lower our plant’s hazardous air pollutant emissions limit from the 17 tons per year allowed by the original permit to 6 tons per year under the modified permit. This came to light when our test results showed our original permit hazardous pollutant limits could be lowered to more accurately reflect actual levels.

This is another sign as to the efficiency of our facility. And it’s another example of how LRAPA will look at a facility after it has been operating and adjust the emission limits to reflect the test data.

Seneca Sustainable Energy remains the cleanest plant of its type in the Pacific Northwest and, likely, all of North America. We are very proud of Seneca’s renewable energy facility — and we know that others will be too, once they know the facts.

Richard Re is manager of the Seneca Sustainable Energy Biomass Plant in Eugene.