Plant material is used in a variety of ways to create energy: combusted to produce heat or electricity; anaerobically digested to produce methane; and converted to ethanol, biodiesel, or hydrogenated vegetable oil for fuel. Within transportation, bioenergy makes up almost 3 percent of fuel consumed. Within the power sector, it comprises 2 percent of the total.
From a climate perspective, whether plant material used for bioenergy is annual or perennial (or waste content) makes all the difference. Because energy inputs for annual bioenergy crops, such as corn, are so high, they make little progress on cutting emissions.
Perennial bioenergy crops—such as switchgrass, fountain grasses, silver grass, poplar, willow, eucalyptus, and locust—can be different. Cultivated appropriately, they can reduce emissions by 85 percent compared to corn ethanol. Replacing annuals with perennials also raises carbon sequestration in soil.
Many perennial bioenergy crops are prime candidates to grow on degraded land not suited to food production. Compared to corn and other annuals, perennials can prevent erosion, produce more stable yields, be less vulnerable to pests, and support pollinators and biodiversity.
Technical summaries for each solution will be available May 1, 2017.