I work with large biomass plants for part of my living and spent several years reducing the odor of the Berlin pulpmill previously. There will be no sulfur odor and with the amount of air emmision control equipment they are required to put on, its going to be very clear source of combustion. The permits for the facility are for low grade forest resdiduals, they are not permitted for trash or any other waste products, they would have to repermit the facility to burn anything else. The wood they burn has to be certified as sustainably harvested so they cant just buy wood from a clear cut , there has to be a chain of custody going all the way back to the woods.
The biggest local impact may be fugitive dust from the chip piles and the traffic associated with bringing in 1600 tons per day of wood (thats a very rough swag on volume). Regionally the impact will be more thinning cuts and "prescriptive foresty" now that there will be steady market for low grade wood. Unfortunately Dillon left a lot of trashed woods in the region and when they regenerate, there will have to be several intermediate thinnings to get the woods back quickly. Mother nature can eventually do it, but it takes a lot longer.
I dont have any involvement with the current project but compared to a vacant lot or an abandoned mill complex like Millinocket still is, the Berlin project sire looks a lot better.