To help stakeholders in government and business make smart decisions about the best types of land and local climates for planting bioenergy crops, researchers at the U.S. Department of Energy’s (DOE’s) Argonne National Laboratory are using computational modeling to predict which counties could see increases in soil organic carbon from cultivation of crops like switchgrass for biofuels. Increasing carbon stored in soil is one way to help mediate the amount of carbon dioxide released into the atmosphere.
Soil carbon modelling
The researchers combined county-level crop yield and weather data and soil data at depths relevant to bioenergy crops. The team used a soil carbon model to calculate sequestration rates, or the rate at which carbon is transported in or out of the soil. This work was done in collaboration with Steffen Mueller at the University of Chicago, Michelle Wander at the University of Illinois at Urbana-Champaign and Ho-Young Kwon at the International Food Policy Research Institute.
By modeling soil carbon at a depth of 100 centimeters rather than the standard 30, the study results represent the deeper root systems of crops like switchgrass and poplar trees that transport carbon below the topsoil, unlike more shallow-rooted row crops like corn. The team also collected detailed data on local weather patterns, soil conditions, historical land use and local crop yields for each county, as well as data from bioenergy crop field trials conducted by other agencies and national laboratories.
“By doing this type of analysis we can find areas where bioenergy crops can have positive environmental effects — but also hotspots where growing bioenergy crops may cause a decline in soil carbon,” said Argonne postdoctoral researcher Zhangcai Qin, who is examining the environmental effects of biofuel production.
Incorporation of obtained results into the GREET model
To further understand the net carbon impact of biofuels from the farm to fuel emissions, the researchers incorporated soil carbon modeling results into Argonne’s Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation (GREET) model, which evaluates the full life cycle of energy consumption and emissions of different transportation fuels, including biofuels. For example, when soil organic carbon changes were included in the GREET model, ethanol produced from deep-rootedMiscanthus showed the potential to sequester carbon on a life-cycle basis.
“By integrating high-resolution, soil organic carbon modeling with a life-cycle analysis model, we can holistically estimate the life-cycle greenhouse gas emissions of biofuels, including the influences of the life-cycle stages of feedstock planting, conversion to a fuel and fuel combustion,” said Jennifer Dunn, Argonne Biofuels Life Cycle Analysis team lead. “These results could help decision-makers at all levels identify areas that are poorly or well-suited for biofuel crops.”
Based on the press release by Argonne National Laboratory
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