According to a report by the USDA Agriculture Research Service, sweet potatoes provide more carbohydrate for fuel ethanol production as field corn in Maryland and Alabama, the two states tests were run in.
In experiments, 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, Agricultural Research Service (ARS) scientists report. The same was true of tropical cassava in Alabama.
The results seem pretty promising especially once you consider that both sweet potatoes and cassava require less fertilizer and pesticides than corn does.
For the sweet potatoes, carbohydrate production was 4,692 tons an acre in Alabama and 6,353 tons an acre in Maryland. Carbohydrate production for cassava in Alabama was 4,940 tons an acre, compared to 1,434 tons an acre in Maryland. For corn, carbohydrate production was 1,692 tons an acre in Alabama and 2,760 tons an acre in Maryland.
There are some downsides to both sweet potatoes and cassava but as the report states the results are positive enough to warrant further study.
The disadvantages to cassava and sweet potato are higher start-up costs, particularly because of increased labor at planting and harvesting times. If economical harvesting and processing techniques could be developed, the data suggests that sweet potato in Maryland and sweet potato and cassava in Alabama have greater potential than corn as ethanol sources.
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.
Source : USDA