New Global Analysis by Federal and State Scientists Pinpoints Gains In Corn Field Carbon Retention

Source: By Clean Fuels Development Coalition • Posted: Thursday, July 25, 2019

Study Also Finds Risks of Removing Crop Residues

Washington, D.C., July 22:  A new analysis of the results of thousands of soil samples taken around the world has found that, on average, well-managed cornfields increased their stocks of carbon by an annual rate of .41 metric tons per hectare compared to baseline values. At the same time, scientists analyzing the data found that removing corn stalks, leaves and cobs from harvested fields can reduce levels of organic carbon in soil and cause deterioration of soil health.

These were among the principal findings of a meta-analysis of hundreds of studies assessing the impact of corn stover retainage or removal on soil organic carbon stocks. It was conducted by a team of environmental and soil Scientists from the Department of Energy’s Argonne National Laboratory, the U.S. Department of Agriculture’s Agricultural Research Service, South Dakota State University and the South Dakota School of Mines and Technology. The project was led by Dr. Hui Xu, Energy Systems Assessment Group, Argonne National Laboratory

Their paper, titled “A global meta-analysis of soil organic carbon response to corn stover removal,” was recently published in Global Change Biology, Bioenergy, an international journal that publishes original research relating to the interface between science and the production of fuels from plants, algae and agricultural wastes.

Corn stover is a global resource used for feeding livestock and producing fuel. It is generally defined as stalks and leafy residue left on the fields after harvest.  Some studies have suggested that while the stover itself is a potential biofuel feedstock, excessive removal of it can reduce soil carbon levels and soil health. Researchers believe the results of the far more comprehensive meta-analysis confirm concerns of many soil scientists and corn producers about the impact of removal.   Stover removal generally reduced final SOC stocks by 8% and stover retention, which is the predominant practice in the U.S. Midwest, increased stocks of organic carbon.

The results provide guidance for farmers, soil scientists and soil health and climate change mitigation advocates and have implications for biofuel life cycle greenhouse gas accounting/modeling. At present, life cycle analysis models that rate the carbon intensity of corn ethanol and other biofuels, as well as petroleum products, do not take into account farming practices that could increase or lower carbon levels in soil. But according to Doug Durante, president of the Clean Fuels Development Coalition, this is critical to understand as the quest for low carbon fuels is both a national and global issue.

“Up until now, crop residue cellulosic biofuel has been considered to be a very low carbon fuel.  However, this research indicates that its GHG intensity is significantly higher than thought, and while still capable of providing more than a 50% reduction compared to fossil fuel gasoline,  this research shows that traditionally managed first generation corn starch ethanol can provide the same reductions in terms of a lower greenhouse gas footprint.

According to CFDC calculations, the additional .41 metric tons of carbon sequestration per acre is a huge gain based on EPA data that calculates  conventional passenger vehicles emit 4.6 tons of CO2, or 1.2 tons of carbon,  annually.  The result is that the soil sequestration per acre from corn can offset 1/3 of the carbon emission from one car for a year.  Put another way, said Durante, the 90 million acres of corn in the US is offsetting 60 million tons of carbon dioxide emissions.

“These are dramatic percentages in terms of carbon reduction,” Durante said. “There is not a carbon mitigation program on the planet that contemplates those kinds of reductions, and it is happening now.

This study shows that corn not only produces food, feed, and fuel but can do so in an environmentally responsible manner.”

He called on the Environment Protection Agency to reflect this benefit and other recently-developed scientific data in their analyses by adopting the Argonne National Laboratory’s 2018 GREET model for biofuel GHG accounting.  “In the interest of efficient use of tax dollars, smaller government, and scientific accuracy, EPA must recognize that DOE and the Argonne Lab have what is the gold standard in this field and adopt their model immediately.”  Durante praised the efforts of Dr. Xu, Michael Wang, Hoyoung, and the entire study team for their continual updating and refinement of the GREET model and ensuring it represents accurate information.

For more information, contact Dr. Hui Xu, the lead author of the study at hui.xu@anl.gov, copies of the study can be downloaded from the Clean Fuels Development Coalition website (www.cleanfuelsdc.org)

 

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