Introduction
Several studies have been done on the energy life cycle analysis of soybean biodiesel. These include:
- A 1994 paper published by the National SoyDiesel Development Board (Ahmed et al.);
- a 1998 study by the National Renewable Energy Laboratory (Sheehan, et al., also called the NREL model);
- A 2005 paper by Pimentel and Patzek;
- A 2006 study by the Argonne National Laboratory (ANL – also called the GREET model); and
- a 2009 study published by the U.S. Department of Agriculture (Pradhan et al.).
All of these studies varied in their conclusions. The variations were due to different assumptions about energy inputs. This article addresses the varied energy inputs for transporting soybeans from the farm to the crushing plant.
Soybean Transport
There was a significant variation in soybean transport energy among the models. Ahmed et al. (1994) estimated the transportation energy based on 80 kilomters (50 miles) of crop transport distance by truck. Sheehan et al. (1998) assumed the soybeans were moved by trucks from the field to a crushing plant located at a distance of 120 kilometers (75 miles). In the Pimentel and Patzek (2005) study, the soybean transportation included transportation of machinery, fuel and seed at an estimated distance of 1,000 kilometers (621 miles). The other models did not include any energy for transportation. Despite the longer distance included for soybean transport in Pimentel’s model, it was puzzling to see that the actual energy allocated to soybean transport was smaller (Table 1).
New estimates from GREET Model (Argonne National Laboratory)reported a distance of 50 miles from field to crushing plant with energy for transportation of 6,393 Btu/bushel (Pradhan et. al, 2009). The energy use could be adjusted for longer or shorter actual distance hauled.
Table 1: Energy use in soybean transport (MJ/ha except for energy allocation)
| Inputs | Ahmed et al. (1994) | ANL (2006) | Sheehan et al. (1998) | Pimentel and Patzek (2005) | Pradhan et al. (2009) |
| Soybean Transport | 63.44 | 587.77 | 378.77 | 167.37 | 633.04 |
Assuming the crushing plant is at the center of a circular field, the theoretical minimum distance (radius of the field) needed to supply soybeans for a 189 milliliters (50 million gallon) oil production plant is about 24 kilometers (15 mi), given average yield and oil content. Even after considering inefficiencies, such as a non-circular field, making turns, non-contiguous soybean fields, and hauling to a plant that is not the closest, transporting soybeans 1,000 kilometers (621 mile), as assumed by Pimentel, is hard to justify. Since bean transportation is only a small fraction of the total energy input in all cases, it is not a major factor leading to differing conclusions.
Bibliography
Ahmed, I., Decker, J., and Morris, D. (1994): How much energy does it take to make a gallon of soydiesel? Jefferson City, MO: National SoyDiesel Development Board.
ANL (2006) The greenhouse gases, regulated emissions, and energy use in transportation (GREET) model Version 1.6. U.S. Department of Energy laboratory, Argonne, LLC. Available at: http://www.transportation.anl.gov/software/GREET/
Pimentel, David and Patzek, Tad W. (2005): Ethanol production using corn, switchgrass, and wood; biodiesel production using soybean and sunflower. Natural Resources Research 14(1), 65-76.
Pradhan, A., Shrestha, D. S., McAloon, A., Yee, W., Haas, M., Duffield, J.A., and Shapouri, H. (2009) Energy Life-Cycle Assessment of Soybean Biodiesel. U.S. Department of Agriculture, Agricultural Economic Report Number 845.
Sheehan, J., Camobreco, V., Duffield, J., Graboski, M., and Shapouri, H. (1998): Life cycle inventory of biodiesel and petroleum diesel for use in an urban bus. NREL/SR-580-24089 Golden, CO: National Renewable Energy Laboratory. U.S. Department of Energy.
More Topics on Biodiesel LCA
Introduction to Life Cycle Analysis (LCA)
Energy Life Cycle Analysis of Biodiesel
Energy in Soybean Agriculture
Energy in Soybean Crushing and Transesterification
Energy in Biodiesel Transport
Environmental Life Cycle Analysis of Biodiesel
- Introduction to Farm Energy
- Introduction to Biodiesel
- Biodiesel Feedstocks
- Biodiesel Processing
- Biodiesel Utilization
Contributors to this Article
Author
- Dev Shrestha, Associate Professor of Bioenergy, Department of Biological and Agricultural Engineering, National Biodiesel Education Program, University of Idaho
Peer Reviewers
- Joe Thompson, Research Support Scientist, Department of Biological and Agricultural Engineering, National Biodiesel Education Program, University of Idaho
- Cole Gustafson, Biofuels Economist, North Dakota State University
