Recent increases in nitrogen oxide (NO_x) emissions from coal-fired electric generating units equipped with selective catalytic reduction

Figures & data

Figure 1. Total number of coal-fired EGUs, and the number and percent with installed SCR in each year in CAIR states.

Figure 2. CAIR states average ozone season NO_x emission rates of SCR-equipped coal-fired EGUs, with number of units.

Figure 3. Average ozone season emission rates of coal-fired, SCR-equipped EGUs among the Top 200 NO_x emitters in each of the three cap and trade programs.

Table 1. Representative individual EGU comparisons of pre-SCR installation NO_x emission rates (lb NO_x/mmBTU), with BORs, 2014 ozone season rates, and 2014/BOR ratios.

	Pre-SCR Installation	Best Observed Rate
Unit ID	Rate | Year	Rate | Year	2014 Rate	2014/BOR
9943	0.337 | 2003	0.047 | 2005	0.150	3.2
31223	0.397 | 2000	0.087 | 2005	0.370	4.2
39442	0.478 | 1998	0.066 | 2005	0.372	5.6
31492	0.381 | 1998	0.047 | 2003	0.411	8.7
60042	0.355 | 2002	0.039 | 2005	0.367	9.4

Figure 4. Numbers of SCR Coal units found among the top cohorts of CAIR states NO_x-emitting EGUs in the 2008–2014 ozone seasons.

Table 2. Percentage of U.S. annual electric generation by fuel type.

Fuel	2008	2009	2010	2011	2012	2013
Coal	48%	44%	45%	42%	37%	39%
Natural gas	21%	23%	24%	25%	30%	28%
Other	31%	33%	31%	33%	33%	33%

Figure 5. Production of shale gas and annual average delivered gas cost for electrical generation, 2007–2013.

Figure 6. Total monthly average ozone season allowance costs at 3.0 lb NO_x/MWhr, with monthly average natural gas electrical generation costs, approximate ammonia cost, and average ozone season emission rates.

Figure 7. U.S. net electric generation.

Figure 8. Average 2014 ozone season statewide NO_x emission rates of SCR Coal EGUs.

Figure 9. Ozone season NO_x emissions in CAIR states with fraction due to SCR Coal curtailment and its percentage of total emissions.