Evaluation of Alternative Bioethanol Feedstock Crops

Evaluation Of Alternative Bioethanol Feedstock Crops

This material was first presented as a poster:

J.A. Rodgers, M.K. Bomford, B.A. Geier, and A.F. Silvernail. 2007. Evaluation of alternative bioethanol feedstock crops. Kentucky Academy of Sciences Annual Meeting, Louisville, KY.

Download poster (1 MB pdf)

Introduction

Growing concern about foreign energy dependence has led to increased interest in biofuels as domestically-produced alternative energy sources. The United States is now the world’s largest producer of ethanol fermented from plant carbohydrates.  More than 95% of this ethanol is currently made from the grain of corn (Zea mays L.) through a production process that consumes 75-90% as much energy as is available from the fuel.1 Other crops may offer superior energy returns, or be more compatible with sustainable production systems suitable for adoption by limited-resource farmers.


Materials and Methods

Four crops that could be used for food or fuel -- sweet corn, sweet sorghum (Sorghum bicolor L.), sweet potato (Ipomoea batatas L.), and Jerusalem artichoke (Helianthus tuberosus L.) -- were grown in 2 x 4 m plots on land in transition to organic production at the Kentucky State University Research and Demonstration farm. Each plot contained three crop rows, spaced 90 cm apart. Treatments were replicated four times. Jerusalem artichoke tubers were planted 30 cm apart on 1 June, 2007; sweet sorghum  was seeded with a push seeder on 6 June; sweet potato starts were planted 30 cm apart on 8 June; and sweet corn was hand-seeded 15 cm apart on 12 June. All rows were irrigated with drip tape as needed, beginning on 12 June.

Potential food / fuel crops

Sweet corn (left), Jerusalem artichoke flower and root mass (center top & bottom), sweet potato foliage (top right), and sweet sorghum seed heads (bottom right).

Corn was hand-harvested on 6 September. Grain was dried and removed from cobs. Sweet potato was harvested on 4 October using a potato digger attached to a walk-behind tractor. Sweet potatoes were cured in a warm (>26 °C), humid high tunnel for 10 days, before storage in a cool dark location. Jerusalem artichoke tubers were dug and removed from stems and leaves on 10 October. Sweet sorghum was cut on 10 October. The stalks were pressed to extract juice on 11 October. 


Results

Yield of alternative food/fuel crops

Yield of sweet corn kernels, Jerusalem artichoke tubers, sweet potato tuberous roots, and sweet sorghum juice. A good grain corn yield in the US is about 1 kg/m2.2

Carbohydrate and expected ethanol yields

Carbohydrate and expected ethanol yields, based on standard conversion values.3 Current ethanol yield from grain corn in the US and sugarcane in Brazil is approximately 3,500 and 6,000 L/ha, respectively.1 


Conclusion

  1. Sweet potato may be a more land-efficient crop for bioethanol production than corn. 
  2. Sweet potato and sweet sorghum are compatible with low-input production systems suitable for adoption by limited resource farmers in Kentucky.


References

  1. Marris, E. 2006. Drink the best and drive the rest. Nature 444: 670-672.
  2. USDA-ERS. 2008. Feed grains database.
  3. Matheson, S.W. 1980. The manual for the home and farm production of alcohol fuel. Ten Speed Press, Berkeley, CA.

Last updated March 18, 2008

College of Agriculture, Food Science and Sustainable Systems