Increasing Availability of Renewable Diesel with a High Oil – Low Protein Soybean Variety
We all know that greenhouse gas (GHG) emissions must decrease rapidly to limit global warming and prevent catastrophic climate change. The transportation sector is a big contributor to GHG emissions (approximately 30% of the US total emissions) and biofuels can play a significant role in reducing these emissions. Biodiesel and renewable diesel made from vegetable oils can replace petroleum diesel in long-haul trucks and shipping. Biodiesel blended with petroleum diesel and renewable diesel are ‘drop-in fuels’ that can be used without modifications of diesel engines.
The U.S. Energy Information Administration expects the production of renewable diesel in the U.S. to reach 1.8 billion gallons per year by 2024 (compared to 0.6 billion gallons per year in 2020). Diverting that much vegetable oil to fuel production will greatly increase the competition between food and fuel production. The development of a high oil – low protein soybean variety would provide a partial solution to this dilemma. A high oil – low protein variety would increase oil production per acre, reducing the acres needed to meet the potential demand for renewable diesel.
Breeding for high seed oil concentration in soybean is difficult because higher oil concentrations are directly related to lower protein concentrations and protein contributes significantly to the commercial value of soybean seed. When breeders increase oil concentration, protein concentration usually goes down resulting in a variety that is unacceptable for routine production. It should be possible, however, to significantly increase oil concentration if the protein concentration is allowed to decrease. Historical data describing the inverse relationship between oil and protein concentrations suggests that the oil concentration could reach 35% if the protein concentration dropped to 5% (current varieties are about 20% oil). This approach would produce a unique new variety- essentially a new crop - that would be grown only for its oil and segregated from commodity soybean. This ‘new crop’ could be given a new name to help differentiate it from commodity soybean.
One of the advantages of this approach is that this ‘new crop’ would still be soybean with the high yield and improved agronomic characteristics resulting from 100 years of intense breeding activity. The management practices, herbicides, and pesticides for the production of this ‘new crop’ are already available along with a large pool of experienced growers.
Another advantage stems from the fact that soybean is a legume and does not require N fertilizer. Eliminating N fertilizer and the GHG emissions associated with its production reduces the carbon footprint of renewable diesel providing soybean with an advantage over other oil crops (such as canola, carinata, pennycress and camelina) that require N fertilizer.
Increasing production of conventional soybean varieties to meet the forecast demand for renewable Increasing Availability of Renewable Diesel with a High Oil – Low Protein Soybean Varietydiesel could result in a glut of soybean meal on the market. This new high oil – low protein soybean variety would not produce 48% soybean meal, so it would help reduce excess meal supplies.
A high oil-low protein variety will increase the oil production per acre but is not realistic to expect it to meet the enormous demand (currently 46 billion gallons per year) for diesel fuel by the U.S. transportation sector. Growing a new high oil variety (35% oil) on the entire U.S. soybean acreage (84 million acres, average for 2018 – 2022) and assuming an average U.S. yield (2018 to 2022) would produce only roughly 20% of the U.S. yearly diesel consumption. Clearly, a high oil soybean cannot supply the total needs of the transportation sector, but it can help the sector transition to greener fuels (hydrogen, green ammonia, electricity). Changes in agricultural production systems and dietary habits as society adjusts to a changing climate may make more land available for biofuel production. For example, a shift to a plant-based diet or reduced demand for ethanol due to an increase in electric cars could significantly reduce corn production, making more land available for oil production.
Our current knowledge of the genetics of soybean seed composition suggests that it may be possible to produce a high oil – low protein variety. Such a variety would fit right into current production systems and the increased oil production per acre would contribute to the shift away from fossil fuels that is needed to avoid climate catastrophe.
Adapted from Egli, D.B. 2023. Expanding the Availability of Soybean Oil for Renewable Diesel with a High Oil – Low Protein Cultivar. Crop Science (https://doi.org/10.1002/csc2.21133).