New research is confirming that corn-based ethanol is even greener than we thought — especially ethanol from South Dakota.
A national study shows that greenhouse gas emissions from ethanol continue to decline over time.
However, a ground-breaking study from South Dakota Corn Growers and South Dakota State University proves that corn grown in South Dakota actually adds carbon to the soil by virtue of the unique Northern Plains climate and increased use of minimum tillage practices by farmers. This means that ethanol produced from South Dakota corn has a lower carbon footprint than was previously assumed.
Researchers collected a total of 95,214 soil samples from the zero- to six-inch depth, and 74,655 production surveys from between 1985 and 2010. Researchers used these samples to assess South Dakota carbon storage and tillage practices.
The long-term organic soil test data, when analyzed, confirmed that corn production in eastern South Dakota is now putting carbon back into the soil, reducing the carbon footprint of South Dakota corn.
It’s called carbon sink. A carbon sink is anything that absorbs more carbon than it releases. In contrast, a carbon source is anything that releases more carbon than is absorbed. Forests, soils, oceans and the atmosphere all store carbon, and this carbon moves between them in a continuous cycle.
Several facts are key to the science behind the research results. One of the most important is the ability of South Dakota corn producers to grow higher yields in the cooler, Northern Plains climate.
- Over the 25 years of the study, South Dakota corn average yields have increased at a rate of 2.29 bushels per acre per year.
- Higher yields mean more crop residue left behind. The increased amount of residue has a significant impact in building soil carbon.
- The cooler Northern Plains climate plays a key role in the equation due to mineralization, a process by which organic matter and humus break down in the soil. When there are cooler temperatures, the mineralization rates are lower.
The Impact of Minimum Tillage
No-tillage adoption in South Dakota has increased from less than five percent in 1985 to 35 percent in 2010. Minimum and no-tillage production means there is more residue left behind in cornfields. Those practices also mean fewer trips across a field, resulting in even greater environmental benefits. The researchers used life-cycle-analysis methodology to determine the carbon footprint of agricultural products.
As South Dakota producers moved from conventional tillage to a reduced tillage, the amount of carbon that was consumed in diesel fuel has declined from eight to ten gallons of diesel per acre down to two to three gallons per acre.
Now it’s proven that the carbon concentration of South Dakota soil profiles is increasing – which means the quality of our soil is improving.