The idea behind biomass is that it's fuel that can be cultivated and harvested. Be it wood, corn, soya beans, palm or cane, or whatever, you grow "fuel". You burn it, and then you burn each year a new harvest.
Yes, ecological problems will always exists with any kind of fuel. As far as biomasses are concerned, besides the sulphur oxides, or the ashes of combustion, we should consider the chemicals used in agriculture, or the competition in arable land and water between "fuel" and "food".
But it's a great progress compared to fossil fuels. It's much more sustainable, and economically it's "here" very competitive already, while solar energy and wind energy are still not competitive with fossil fuels and experience growth because of the heavy subsidies (I'm not against this kind of subsidies, as they have helped reaching a higher efficiency and economies of scale, but, so far, those alternative energy sources are not yet competitive with the "dirty" ones).
Also, being limited in quantity, and relatively expensive, they force an energetic disciplines on economies. Cheap oil did not do that for decades.
Humanity has, for many centuries or millennia, relied solely on biomasses. The lucky ones would burn their wood on fireplace which could reach, maybe, 8% efficiency being optimist.
My wood and woodpellet stove is certified to deliver >85% efficiency. Some "accumulation stoves", typically with great mass (such as the Finnish Tulikiwi, to name a famous name) reach 90% efficiency. We can potentially produce 10 times more heat than, say, the ancient Romans while burning the same wood. It goes without saying that we can produce and transport much more wood than them. Add the corn, soya etc, plus the wood from discarded material, the gases from tenure etc and we have a huge amount of energy that we just "throw away" and that it's there ready to be economically exploited.
All in all, biomasses are really the present of alternative fuels. Wind and solar are the future maybe. Nuclear fusion is probably more like a dream than a possibility, but who knows...
PS Electric energy from nuclear fission was available a few years after the first atomic bomb. Decades have elapsed since the first hydrogen bomb and still no trace of energy from nuclear fusion.