Reap more than you sow. That's the challenge faced by farmers who grow crops for biofuels.
Even as biofuel production booms, some scientists have questioned whether the fertilizer- and tractor-intensive farming of crops used to make biofuels consumes more energy than it produces. But making ethanol from switchgrass can yield more than five times as much energy as the farmers use to grow the crops, new research shows.
The study is the first based on large-scale, real-world farming of switchgrass, a perennial prairie grass that can grow on marginal lands unsuitable for food crops. In previous work, scientists estimated the efficiency of growing switchgrass for fuel based on experimental plots, which are typically only a few square meters in size.