It's less sustainable than renewables, but fills a practical requirement for peaker style powerplants (which fill sudden demand) without resorting to coal/oil/gas, which are considerably less sustainable. Drax already existed as a coal/gas facility, so transitioning it to a biomass-with-carbon-capture facility is a net benefit to the environment, even when considering the packaging and transportation of the wood, because those steps were required for its coal predecessor.