Oklahoma State University


Soybean as a Biofuel Crop

Soybean [Glycine max (L) (Merr.)] is a species of legume native to East Asia.  It is an annual plant that has been used in China for thousands of years.  Soy contains significant amounts of all the essential amino acids for humans; thus, a good source of protein.  Soybeans are the primary ingredient in many processed foods, including dairy product substitutes; however, it was first used in the U.S. as a forage crop.

Beans are classed as pulses whereas soybeans are classed as oilseeds and are more like the pea than beans.  It is a versatile crop, having a diverse range of uses.  Soybean varies in growth, habit, and height.  It may grow prostrate, less than 8 inches tall, or grow upright in excess of 6 feet high.

Pods, stems, and leaves are covered with fine brown or gray hairs. The leaves are trifoliolate, having three or four leaflets per leaf, and the leaflets are two to six inches long and one to three inches broad.  Leaves fall before the seeds mature.  The fruit is a hairy pod that grows in clusters of three to five; each pod is one to three inches long and usually contains two to four seeds, five to ten mm in diameter.  Seeds such as soybeans containing high levels of protein can undergo desiccation yet survive and revive after water absorption.

The acreage of soybean in Oklahoma is usually around 300,000 acres. Production of soybean in western Oklahoma is limited because of rainfall (total and distribution).  Typically, shorter season soybeans are planted in April, while longer season soybeans are planted in June after wheat harvest.

Soybean has been used in biodiesel for many years but the demand for it in food and animal feed products keeps its price relatively high.  This means the price of biodiesel from soybeans will only be economical when the price of petroleum is high.  In general it is thought that energy conversion of soybean via biodiesel is higher than energy in corn via ethanol.  In both cases when grown as biofuel crops, these crops compete for the best land available for the production of food and feed.

Web sites for soybean as a biofuel crop:




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