Study Shows Carbon Sequestration from Corn Production Runs Deep

The ethanol industry has some good news to share. And it comes in an arena where the domestically produced biofuel has often been challenged – carbon sequestration and the life-cycle assessment of ethanol made from corn.

A study published by researchers associated with USDA’s Agricultural Research Service uses soil samples taken continuously in Nebraska over the past decade that show growth in carbon sequestration greater than previously reported and at greater depths.

Retaining carbon in the soil offers a wide array of benefits. It offers food for microbes, enhances air and water movement, offers holding areas for plant nutrients, reduces erosion and reduces the compaction of soil.

Life-cycle assessments use a methodology that determines the total greenhouse gases, including carbon dioxide, and converts soil, animal and plant processes data into a cradle-to-grave environmental accounting analysis.

To date, life-cycle analyses for corn and other bioenergy crops have been conducted using models in which soil organic carbon information is usually taken from the top 30 to 40 centimeters of soil. Furthermore, any data about the effects of crop management practices on soil organic carbon has been limited and, as a result, life-cycle assessment models have not generally included the effects of those management practices.

What the research in eastern Nebraska – the longest on-going carbon sequestration study on corn and switchgrass crops grown for bioenergy – has shown is that in the first nine years, corn with best management practices averaged annual increases in sequestration at levels greater – and at greater depths – than previous models would suggest. For corn, 50 percent of the increase in soil organic carbon sequestration was below the 30-centimeter depth. Furthermore, the results indicate that nitrogen fertilizer rates and harvest management regimes can affect the magnitude of sequestration.

It has long been determined that aggressive tillage can send carbon dioxide into the atmosphere and result in erosion that can send organic matter into neighboring waterways. Management practices such as no-tillage, strip tillage, cover crops and growing perennial forages slow the decay of organic matter and aid in the sequestration of soil carbon.

An equally critical point raised by the study is that it would suggest the use of uniform soil carbon effects for bioenergy crops from sampling depths of 30-40 centimeters for large-scale life-cycle assessments, as has been the practice among researchers until now, doesn’t tell the whole story. By using what has now been shown to be limited data, policy makers penalize ethanol producers by failing to consider factors that went into the corn grown for the biofuel, including good management practices and the wealth of sequestration that is now shown to exist well below traditionally studied depths.

The Nebraska study is the kind of information that needs to be brought to the attention of policy makers and regulators who continually rely on dated findings that undervalue the carbon sequestration that occurs with the production of corn for ethanol. Agricultural producers increasingly are being asked to document the impacts of their products on the environment. Those who regulate the market access of biofuels have an equal responsibility to consider all of the facts.

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