Table 1.

Bioenergy feedstocks

Crop category	Example	Industry status	Land, environment, and energy
Starch-rich1	Maize, wheat, sorghum	About 50 billion L ethanol in the US based on maize	Typically grown on high-quality cropland with substantial fertilizer input. Fossil energy displacement ratio 1.3 to 1.7. 4,000 L ethanol/ha in the U.S.
Sugar-rich2	Sugarcane, sugar beets	About 23 billion L ethanol in Brazil based on sugarcane	Grown primarily on former pastureland in Brazil. Agrichemical inputs less than maize. Fossil energy displacement ratio about 8 to 10. 6,700 L/ha in Brazil today, could be substantially higher with conversion of cellulosics, energy cane.
Oil-rich3	Rapeseed, soy, sunflower, palm oil	About 23 billion L produced worldwide, most in the EU, US, and Brazil	Rapeseed, soy generally grown on cropland. Most palm oil plantations are on former forests. Fossil energy displacement ratio 2 to 2.5 for rapeseed and soy, about 4 to 8 for palm. 530 L/ha for soy in Argentina; 3,600 L/ha for palm in Malaysia.
Cellulosic4	Grass, trees, various wastes	331 TWh electricity globally. Liquid fuel capacity about 175 million L worldwide	Could in principle grow on land unsuitable for crops. Potential environmental benefits when incorporated into agricultural landscapes. Fossil energy displacement ratio somewhat speculative for liquid fuel production but expected to be similar to sugarcane. Over 7500 L/ha based on miscanthus yields in the US (25 tonnes/ha), 75 US gal/ton.

¹Starch-rich crops: annual production [39]; fossil energy displacement [40]; corn yield [41]; dry mill yield [42].

²Sugar-rich crops: annual production [43]; fossil energy displacement and ethanol land yield [44].

³Oil-rich crops: annual production [7]; fossil energy displacement [45,46]; soy oil yield [47]; palm oil yield [48].

⁴Cellulosic crops: global electricity [49]; global cellulosic biofuel capacity [37]; current miscanthus yields [50].