Recent data indicate that North Dakota lignites are similar in mercury
content to subbituminous coals from Montana and Wyoming. Studies dati
ng back to the 1970s and early 1980s had shown that North Dakota ligni
tes contain significantly higher levels of mercury than subbituminous
coals from the Powder River Basin (10.1 mg/MMBtu for lignite compared
to 6.2 mg/MMBtu for subbituminous). New data suggest significantly low
er mercury concentrations for both North Dakota lignites and Powder Ri
ver Basin subbituminous coals. These results indicate that North Dakot
a lignites contain an average of 4.2 mg Hg/MMBtu, whereas Powder River
Basin subbituminous coals have an average of 3.7 mg Hg/MMBtu. Thus, t
he two types of coal appear to be very similar in average mercury conc
entrations. The difference between the new and older data likely resul
ts, in part, from recent improvements in sample collection and laborat
ory procedures. If North Dakota lignites do have average mercury conce
ntrations similar to those of Montana and Wyoming coals, as indicated
by the recently obtained data, it is likely that fuel switching would
not significantly affect mercury emissions. These results demonstrate
the importance of using up-to-date information when assessing emission
s at electric utilities or other sources.