In experiments conducted by the USDA's Agricultural Research Service (ARS), sweet potatoes grown in Maryland and Alabama yielded
two to three times as much carbohydrate for fuel ethanol production as field corn grown in those states.
The sweet potato carbohydrate yields approached the lower limits of those produced by sugarcane, the highest-yielding ethanol crop.
For the sweet potatoes, carbohydrate production was 4,692 tons an acre in Alabama and 6,353 tons an acre in Maryland.
The disadvantages to sweet potato are higher start-up costs, particularly because of increased labor at planting and harvesting times. Further studies are needed to get data on inputs of fertilizer, water, pesticides and estimates of energy efficiency.
Overall, the data indicate it would be worthwhile to start pilot programs to study growing cassava and sweet potato for ethanol, especially on marginal lands.