Question

The United States has a lot of federally owned land. Unfortunately, uncontrolled natural forest fires destroy large areas in the western US every summer. In 2002, about 1,000,000 acres of standing timber in national forests were consumed. Some consideration is being given to improved management practices that could produce electric power from residual forest thinning. Estimate the lost energy content of burned US forests during 2002. Assuming the US average electricity demand is about 300,000 MW e , how much forested land would be needed to produce all the country ’ s power? Is this a sustainable alternative? How would you manage the forest lands needed? A few facts to consider: the total forested area on US federal lands in the lower 48 states is about 600 million acres with a standing stock density of about 100 dry metric tonnes of wood per acre. Woody plants and trees capture solar energy via photosynthesis at an average rate of about 0.8 W/m 2 , which corresponds to producing about 5 – 10 dry tons of biomass per acre annually with an average heating value of 8000 BTU/dry lb. Note that 1 acre = 43,560 ft 2 = 0.405 hectare = 4047 m 2 and the average heat-to-work conversion efficiency of a biomass-fired electric power plant is about 35%.

Answer 1