Urb -- If those are the stacks from the new units at Mystic Station - that is mostly water vapor with a small amount of CO2 -- the new units burn Natural Gas
PS -- none of the above is visible -- you are just seeing the effect of turbulent changing of the refractive index due to lots of warm moving air pouring out of the stacks -- there is no more pollution here than if you were lying on your back outside in cold weather blowing air upward while I took a picture from your feet toward your head
PPS: -- outside of one or two Brahmins still having the butler put a scuttle of coal in the fire -- there hasn't been any coal burned in Boston for several generations [no pun intended] :=]
PPPS: -- my dog reminded me that there are wood burning fireplaces in the Back Bay in the Taj, Lenox and perhaps a few other hotels
Ron -- that's in Salem and there's the even bigger Brayton Point in Sommersett (near Fall River) as well -- but neither is close to Boston or to the inner suburbs
The other old plants in the core -- either were originally built to burn oil, were converted from coal to oil -- But today they either burn natural gas with capability to burn oil in an emergency or have been shut down:
Mystic,
South Boston,
T at Southy,
Edgar station at Weymouth (world famous as the most effecient steam generating plant in the wold circa 1925)
Cambridge Parkway
River Street in Cambridge
Everything built in the past 20 years is either all natural gas or it might also host a small fast response peaking unit -- a jt engine which can burn jet fue or natural gas