The U.S. total land area is almost \(9,307,800 \mathrm{~km}^{2}\). Thirty percent of the land is forestland. How much above-ground biomass is available in the U.S. forestland assuming a \(15,240 \mathrm{Mg} / \mathrm{km}^{2}\) biomass density? How much land would we need to grow an equivalent amount of biomass with fast-growing trees (hybrid poplar), or energy crops (switchgrass)?