The phrase "enough biomass" means having an adequate amount of living or organic matter (such as plants and wood) that can be used for various purposes. Full definition
They should be resistant to disease and pests, and also produce enough biomass to make them competitive with fossil fuels. (scientificamerican.com)
The amount of available agricultural land is entirely insufficient for growing enough biomass to replace our current use of fossil fuels, but there is scope for more efficient use of existing biomass. (ramblingsdc.net)