Thursday, September 03, 2009

University of Illinois researchers developing better method to measure carbon content of soil

University of Illinois researchers developing better method to measure carbon content of soil

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One effect of a cap and trade policy for carbon emissions would be to make it profitable to devise ways of storing carbon in the ground. People in Illinois think of FutureGen when they hear this. That’s the plan to inject carbon released by coal-fired power generation into deep underground rock formations. But there are also low-tech ways of storing carbon in the earth, much closer to the surface. Modified tilling methods and patterns of crop rotation can help sequester the carbon that is captured by growing crops.

Of course, credit to landholders for increasing the carbon content of soil would have to be based on accurate before-and-after measurements of soil carbon stocks on a very large scale.

Currently, there is no efficient way of making such measurements. To be sure, scientists are able to determine accurately the percentage of carbon contained in a sample of soil. But in order to do that they must collect it, bring it into a lab, dry it, grind it, run it through a sieve, and then burn it away in a very fancy combustion chamber. This process is labor intensive, time-consuming and expensive. And even when the data derived from it are incorporated with other information into comprehensive modeling systems, the result is only a rough estimate of the carbon content in soil for large areas.

Working with support from the recently established Environmental Change Institute at the University of Illinois, researchers Willie Dong and Nick Glumac are collaborating to develop a faster, cheaper, more accurate way to assess soil organic carbon stocks on a large scale.

Dong, who is a professor in the Environmental Change Institute, and Glumac, who is a professor in the Department of Mechanical Science and Engineering, say they are currently nearing completion of the first step toward this goal, which is to adapt a process called “laser-induced breakdown spectroscopy” to accurately measure the percentage of carbon in soil samples in a lab.

That’s both simpler and more complicated than it sounds.

It means using a laser to vaporize a small amount of soil and then analyzing the light emitted by the resulting plasma to determine what elements were contained in the sample and in what concentrations. Do you remember in science class when you learned that astronomers understand the makeup of stars by analyzing the light they produce? The principle here is the same. The challenge is refining the process to minimize false positive results for carbon from other elements in the sample, but resolution of that issue is within reach.

The next step toward the overall goal will be to modify components of the laser-induced breakdown spectroscopy system for use in the field. This means incorporating the laser and the plasma light receiver into a probe that can be inserted into the ground, and figuring out how to mount all of the necessary apparatus on a mobile platform, such as a flatbed truck. Ultimately this set-up will enable researchers to move across the land and measure the carbon content of soil at many points right in the field, instead of bringing soil samples into a lab for processing and analysis. In combination with other data, these measurements will allow researchers to accurately estimate the total amount of carbon in a given volume of land.

Whether or not it becomes profitable to store carbon in soil will depend on what kind of policy Congress and the President develop to address climate change—and the process of developing that may be more complicated than laser-induced breakdown spectroscopy.

Below you can link to a video on this topic by John E. Marlin from the Agroecology and Sustainable Agriculture Program at the University of Illinois

Zapping Dirt in the Search for Soil Carbon from ASAP Illinois on Vimeo.