Expensive modifications to the turbines have increased the thermal efficiency to 40%, so this is 10GW of thermal power to be obtained from woodchips. Which appears to be (caloric content from here) half a ton of dry woodchips a second: and they'll have to be dry, since wet woodchips would explode impressively in that hot a furnace.
There are ships available capable of carrying 125,000 cubic metres of woodchips (I confess I'm not quite sure why people want to ship wood chips by the fifty Olympic swimming-pools-full; isn't it easier to build the paper or chipboard factory near the forest?); wood chips have a density of about 250kg per cubic metre when packed in ships, so you're talking about one ship that size docking daily.
Swedish short-rotation willow coppice is about nine tons per hectare per year, so you need about fifteen thousand square kilometres of the stuff : half of Belgium. Most reasonably accessible half-Belgiums are not really available to be repurposed for growing flammable trees; Drax refuse on grounds of 'commercial confidence' to say where they're planning to source the wood-chip from, so I would tend to assume it would come from Borneo with an admixture of baby orangutans.