On behalf of the global MSDS (Mustard Seed Day Society) initiative, I present our answer.
Before we can understand how biomass can be a viable alternative, we must first become intimate with the original meaning of the word, which describes all that is (or was) alive. The answer to your question can be found in a clump of turf. To help on that journey of the mind, your touchstone will be a simple point: Production of biomass holds the real solutions; Consumption does not.
Biomass is a pure, easy, simple form of solar energy production and storage, so it's a wonder how Bill Gates could recently say we need a miracle in storage before solar can be viable. It's right before our eyes, everywhere. In theory, every single human on Earth could build a solar collector with solar storage in less than a minute.
No one we know will ever build a 50 megawatt biomass consumption plant, but everyone we know can build a production plant with nothing more than a mustard seed, and we do not mean that figuratively.
On every scale, production is the imperative. Consider how you could produce enough biomass to supply a single breath of air, and build up from there according to your needs. We doubt you will ever get into the megawatt range because you will stop somewhere along the way when you've found your solutions.
At whatever level you stop (individual, family, neighborhood, village, etc.) your solution will depend on the previous levels. It feels lonely to shift our thinking from a top-down perspective because we are so dependent on civilization as our mother, but it is inevitable that we will grow up or die young. We must first reverse the general direction of flow in our infrastructure. It's only hard because it frightens those at the top who need us to remain dependent.
It's much easier if you consume your energy farther down in the food chain where you can produce it, and store it where you will need it. It's important to recognize that there are many different kinds of biomass energy generation strategies besides burning trees. Biomass energy can be supplied by methane, biodiesel, syngas, algae, animal waste, biogas, sewage, and other human waste streams, with minimal to positive impacts on the environment. The choice of which biomass solution to implement will depend a lot on your location.
The answer is different for each of us, but that's the only way it can be found, by understanding the old definition of the word "biomass" so we can consume greenhouse gasses to produce our energy. Our answer to your question is that it is not a viable alternative. It's an imperative.