Interesting. I've not seen kilns for drying firewood, myself. But, I have been in more than one lumber drying kiln, selecting hardwoods for various projects. Those are all run on electric around here, although I know there are gas kilns closer to the city.
Well, it's a good question. It's certainly a lot cheaper to dry the wood by burning wood detritus as the heat source. Plus firewood doesn't need to be as dry as construction lumber. But if demand rises dramatically, the additional speed in drying might become necessary and the extra cost only somewhat offset by sales.
There are maybe half a dozen such operations in VT, all of them small and for firewood only, except for one at a big lumberyard. The lumberyard has a very powerful kiln heated by the enormous amounts of scrap wood the regular lumber operations produce, and it dries very large splits down to about 20 MC. (It's fabulous stuff, but very expensive.) The smaller ones only dry generally to around 30 MC-- not really good enough for an EPA stove, but a huge improvement compared to what most people around here are used to burning. I've coaxed and wheedled the one I deal with to get it down to low to mid 20s, but it takes a full week and can only be done in relatively warm weather.
But buying green wood, never mind cutting it yourself, and stacking several years' worth on your property to dry just isn't within the physical means of most people, even if you live in the country, as I do, and have room. I live on a nice sunny SE-facing slope with lots of wind, but my property is just that, sloped. I tried for several years to do it, but the damn stacks fell over repeatedly after a good rain caused the ground to shift, and i finally just gave up.
But my point is that the fuel issue simply hasn't been even thought of, never mind addressed, by the EPA folks, and you can't wean people off of the old smoke dragons and/or bad burning habits until somebody figures out some kind of solution to it. EPA's goal has more to do with reducing particulates for air quality than it does reducing our carbon footprint per se. Iit may be that they figured as the supply of usable pre-EPA stoves gradually dies out, wood-burners will switch to gas or electricity or fuel oil if they can't deal with the EPA stove fuel problem. They're not in it to promote wood-burning, just reducing the amount of crap that goes into the air by people who insist on wood heat.