A simple thought experiment. What if instead of building the 3.2 GW Hinkley C nuclear power station, the UK built a biomass plant instead? We would need to do two things: build the power plant and gather up the biomass for the plant. The first is not a major problem. The latter on the other hand is a problem, and not a mild one.
Even with an intensively cultivated plantation of fast-growing trees, a wood-burning electricity generation plant would not have power densities higher than 0.6 W/m2, and for most operations the rate would be below 0.5 W/m²
Wind farms have a power density of roughly 2.5 W/m², or about 5 times greater than biomass. As I showed in an earlier post an offshore wind farm would have to be something close to 1,200 km² to provide as much power as Hinkley C.. So, a back of the envelope calculation would indicate that our biomass plant would need to be about 6,000 km², or more accurately 5,200 km² assuming a power density of 0.5 W/m². The United Kingdom has a surface area of 243,610 km², so this would already be taking up slightly over 2% of the UK’s land surface, and this is to provide only about 7% of the UK’s electricity.
What if we expanded biomass to provide all of the UK’s electricity? UK electricity demand averages about 40.6 GW throughout the year (source). To meet this we would need biomass plantations to cover about 81,000 km², essentially one third of the UK (or more likely somewhere else)). To put this in perspective only 12% of the UK is currently forested. The island of Ireland has a total surface area of just over 81,000 square km², so the map below will give you a good idea of just how much land is needed to supply all of the UK’s electricity from biomass. So, it is quite clear that there are some sharp limits on how much electricity you can get from biomass.