Increased cultivation of perennial bioenergy crops ranks #51 on Drawdown’s list of climate solutions, with the potential to reduce atmospheric carbon dioxide by 3.33 gigatons by 2050 at a net cost of US$77.9 billion, but net savings of $542 billion.

“Plant material is used in a variety of ways to create energy,” writes Drawdown. It can be “combusted to produce heat or electricity; anaerobically digested to produce methane; and converted to ethanol, biodiesel, or hydrogenated vegetable oil for fuel.” Currently comprising just under 5% of the global energy mix, “the whole bioenergy lineup is expected to grow.”

But what needs desperately to shrink, Drawdown states, is the market share of corn-based ethanol. Forty percent of America’s corn (the United States is the current king of biofuel production) is today converted directly to ethanol—with the aid of enormous subsidies and a level of inputs that entirely negates all possible climate benefit.

“Cultivated appropriately,” however, perennial bioenergy crops like low-input and self-seeding switchgrass—and willow, whose rapid regrowth from its base trunk allows repeated harvests through a 20- to 30-year life cycle—“can reduce emissions by 85% compared to corn ethanol.”

And because perennials, unlike annuals, live for many years in the same place, giving as much as they take from the soil in which they grow, “they can make a net-positive contribution through sequestration.”

Such laudable goals will require that global perennial cultivation increase rapidly to 143 million acres from 0.5 million today—an escalation that will need to be managed carefully, writes Drawdown.

No “silver bullet,” bioenergy continues to generate heated debate as to “whether or to what extent it can benefit the climate, without endangering food supply or encroaching on forests.” The chapter stresses that, “given the amount of energy we use and food we need to produce, there is simply not enough land to meet all of our needs with plant-based fuels.”