Opinion ID: 4538714
Heading Depth: 4
Heading Rank: 2

Heading: Selective Catalytic Reduction

Text: Unlike the electric motor, the SCR was analyzed in Algonquin's application. According to the application, SCR is a post-combustion gas treatment process in which NH3 [ammonia] is injected into the exhaust gas upstream of a catalyst bed. SCR can reduce NOx emissions from a gas-fired turbine like SoLoNOx by up to 90%. In Step 3 of the BACT analysis, Algonquin's application ranked the SCR as the most effective technology at reducing NOx emissions, and the only technology included that outranked SoLoNOx. However, Algonquin excluded the SCR at Step 4 as not cost feasible. Using the 9-ppm SoLoNOx emissions rate as a baseline, Algonquin calculated the SCR's cost effectiveness at $41,541 per ton of NOx removed, which well exceeded DEP's $11,000– $13,000 range. DEP agreed, leaving SoLoNOx as the BACT. - 26 - Petitioners argued before the Presiding Officer, and now before us, that Algonquin incorrectly calculated the SCR's cost effectiveness. They claim that Algonquin should have used a baseline emissions rate of 25 ppm, which represents the emissions rate of older models of Dry Low NOx turbines. Put differently, petitioners fault Algonquin for considering only the SCR added to its preferred technology, SoLoNOx, without considering the combination of SCR plus a cheaper, less effective turbine. According to petitioners, the SCR-plus-older-turbine combination would be more effective at reducing emissions than SoLoNOx alone and would have a cost effectiveness of $14,483. That value is still over the $13,000 threshold, but petitioners go on to argue that DEP set that threshold in 1990 and that it should be updated for inflation at a minimum.14 So adjusting, petitioners claim, would make the SCR/turbine combination cost feasible. We need not reach the inflation issue because we agree with DEP that 9 ppm was the correct baseline under the applicable BACT guidance.15 The NSR Workshop Manual addresses this situation under the instructions for average cost effectiveness: When calculating the cost effectiveness of adding post process 14 The Presiding Officer rejected petitioners' argument in this case but recommended that DEP consider updating its thresholds for inflation going forward. 15 Petitioners do not argue that an inflation adjustment alone would make $41,541 per ton cost feasible. - 27 - emissions controls to certain inherently lower polluting processes, baseline emissions may be assumed to be the emissions from the lower polluting process itself. In other words, emission reduction credit can be taken for use of inherently lower polluting processes. NSR Workshop Manual, supra, at B.37. The SCR is a post-process emissions control, and SoLoNOx is an inherently lower polluting process (as compared to other Dry Low NOx turbines), so SoLoNOx's 9-ppm emissions rate is the proper baseline. If there was any doubt as to whether the above rule applies here, DEP's 2011 BACT Guidance offers an even more onpoint case study. It says: In the recent past, boiler manufacturers have developed ultra-low NOx burners (UNLBs) which can achieve an oxides of nitrogen emission rate of 9 parts per million (ppm). Before the advent of UNLBs, BACT for NOx for boilers with capacity above approximately 50 million British thermal units per hour was achieved by the use of Selective Catalytic Reduction (SCR) to reduce NOx emissions to 5 ppm, accompanied by a 5 ppm ammonia (NH3) slip. When analyzing the incremental cost of using SCR to reduce the 9 ppm NOx emission rate attained by UNLB to reach a 5 ppm NOx emission limit, it became readily apparent that requiring SCR with added NH3 emissions would be economically infeasible, on a dollar-per-ton-of-pollutant-removed basis. Therefore, NOx BACT for this category of emission units is now 9 ppm, with no NH3 emissions. - 28 - BACT Guidance, supra, at 5 (footnote omitted). Algonquin and DEP followed this guidance to a T, so we can hardly call DEP's decision arbitrary and capricious.16 Petitioners argue that DEP's approach yields undesirable results. Algonquin's 9-ppm turbine may be state-of-the-art, they say, but the BACT process is focused not on technological progress for its own sake. . . . If pairing two older or less effective technologies will achieve a better result than cutting edge, standalone technology, BACT favors the former. Perhaps. But on the other hand, there may be good policy reasons for DEP's current approach. Requiring applicants to fully analyze every combination of add-on technology and process-control technology, including different models of the same technology, would make an already drawn out and expensive process even more so. And, as the case study shows, exclusion of the SCR in this situation may result in slightly higher NOx emissions, but it also results in lower emissions of ammonia, another air pollutant. 16Petitioners attempt to distinguish the NSR Workshop Manual rule by arguing that the phrase inherently lower polluting processes does not apply to newer models of an existing technology like SoLoNOx, which provide incremental refinement. But as the BACT Guidance case study suggests, that is not necessarily the case. See also 310 Mass. Code Regs. § 7.00 (The best available control technology determination . . . may include a[n] . . . equipment specification . . . .). The better understanding of the phrase inherently lower polluting processes, as DEP has interpreted it, is any control technology yielding a lower emissions rate that is not an add-on technology (i.e., a processcontrol technology). - 29 - Lastly, promoting technological development of cleaner technologies may indeed be a goal of the BACT framework. Even if the application of that technology in the instant case does not reduce emissions, the fact that there is an economic incentive for manufacturers to develop cleaner technologies may benefit the state as a whole by, for example, improving the New Source Performance Standards (NSPS) applicable to other facilities. See 42 U.S.C. § 7411; 310 Mass. Code Regs. § 7.00 (citing 40 C.F.R. pt. 60). In any event, our task is not to pick the better policy. As DEP points out, nothing in its rules or regulations requires applicants to consider every possible combination of older, dirtier technologies in order to achieve the lowest possible emissions outcome. Finally, we note that petitioners argue that Algonquin used the wrong formula in calculating the SCR's cost effectiveness, saying that Algonquin focused only on incremental costs when the analysis required demands a focus on average cost. Petitioners miss the point. The NSR Workshop Manual says that, for add-on technologies, the baseline for the average-cost-effectiveness calculation is the emissions rate for the technology to which it is being added (here, SoLoNOx). Incremental cost effectiveness compares one control technology to the next most effective technology (again, SoLoNOx). So for the SCR, the two formulae - 30 - would yield the same result of $41,541 per ton. It matters not whether Algonquin called this average or incremental cost effectiveness.